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Are controls needed for urine cultures?

Are controls needed for urine cultures?


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If testing for bacteria (gram-negative) in a urine culture, are negative or positive cultures needed?

I could not find anything that says controls are needed unless results seem to be contaminated. I thought since controls are used in Gram stains, they would be used in cultures as well. Thanks!


Reducing unnecessary culturing: a systems approach to evaluating urine culture ordering and collection practices among nurses in two acute care settings

Inappropriate ordering and acquisition of urine cultures leads to unnecessary treatment of asymptomatic bacteriuria (ASB). Treatment of ASB contributes to antimicrobial resistance particularly among hospital-acquired organisms. Our objective was to investigate urine culture ordering and collection practices among nurses to identify key system-level and human factor barriers and facilitators that affect optimal ordering and collection practices.

Methods

We conducted two focus groups, one with ED nurses and the other with ICU nurses. Questions were developed using the Systems Engineering Initiative for Patient Safety (SEIPS) framework. We used iterative categorization (directed content analysis followed by summative content analysis) to code and analyze the data both deductively (using SEIPS domains) and inductively (emerging themes).

Results

Factors affecting optimal urine ordering and collection included barriers at the person, process, and task levels. For ED nurses, barriers included patient factors, physician communication, reflex culture protocols, the electronic health record, urinary symptoms, and ED throughput. For ICU nurses, barriers included physician notification of urinalysis results, personal protective equipment, collection technique, patient body habitus, and Foley catheter issues.

Conclusions

We identified multiple potential process barriers to nurse adherence with evidence-based recommendations for ordering and collecting urine cultures in the ICU and ED. A systems approach to identifying barriers and facilitators can be useful to design interventions for improving urine ordering and collection practices.


How does urination occur?

To urinate, your brain signals the sphincters to relax. Then it signals the muscular bladder wall to tighten, squeezing urine through the urethra and out of your bladder.

How often you need to urinate depends on how quickly your kidneys produce the urine that fills the bladder and how much urine your bladder can comfortably hold. The muscles of your bladder wall remain relaxed while the bladder fills with urine, and the sphincter muscles remain contracted to keep urine in the bladder. As your bladder fills up, signals sent to your brain tell you to find a toilet soon.


Contents

Anatomy of the bladder and outlet

The main organs involved in urination are the urinary bladder and the urethra. The smooth muscle of the bladder, known as the detrusor, is innervated by sympathetic nervous system fibers from the lumbar spinal cord and parasympathetic fibers from the sacral spinal cord. [4] Fibers in the pelvic nerves constitute the main afferent limb of the voiding reflex the parasympathetic fibers to the bladder that constitute the excitatory efferent limb also travel in these nerves. Part of the urethra is surrounded by the male or female external urethral sphincter, which is innervated by the somatic pudendal nerve originating in the cord, in an area termed Onuf's nucleus. [5]

Smooth muscle bundles pass on either side of the urethra, and these fibers are sometimes called the internal urethral sphincter, although they do not encircle the urethra. Further along the urethra is a sphincter of skeletal muscle, the sphincter of the membranous urethra (external urethral sphincter). The bladder's epithelium is termed transitional epithelium which contains a superficial layer of dome-like cells and multiple layers of stratified cuboidal cells underneath when evacuated. When the bladder is fully distended the superficial cells become squamous (flat) and the stratification of the cuboidal cells is reduced in order to provide lateral stretching.

Physiology

The physiology of micturition and the physiologic basis of its disorders are subjects about which there is much confusion, especially at the supraspinal level. Micturition is fundamentally a spinobulbospinal reflex facilitated and inhibited by higher brain centers such as the pontine micturition center and, like defecation, subject to voluntary facilitation and inhibition. [6]

In healthy individuals, the lower urinary tract has two discrete phases of activity: the storage (or guarding) phase, when urine is stored in the bladder and the voiding phase, when urine is released through the urethra. The state of the reflex system is dependent on both a conscious signal from the brain and the firing rate of sensory fibers from the bladder and urethra. [6] At low bladder volumes, afferent firing is low, resulting in excitation of the outlet (the sphincter and urethra), and relaxation of the bladder. [7] At high bladder volumes, afferent firing increases, causing a conscious sensation of urinary urge. When the individual is ready to urinate, he or she consciously initiates voiding, causing the bladder to contract and the outlet to relax. Voiding continues until the bladder empties completely, at which point the bladder relaxes and the outlet contracts to re-initiate storage. [6] The muscles controlling micturition are controlled by the autonomic and somatic nervous systems. During the storage phase, the internal urethral sphincter remains tense and the detrusor muscle relaxed by sympathetic stimulation. During micturition, parasympathetic stimulation causes the detrusor muscle to contract and the internal urethral sphincter to relax. The external urethral sphincter (sphincter urethrae) is under somatic control and is consciously relaxed during micturition.

In infants, voiding occurs involuntarily (as a reflex). The ability to voluntarily inhibit micturition develops by the age of 2–3 years, as control at higher levels of the central nervous system develops. In the adult, the volume of urine in the bladder that normally initiates a reflex contraction is about 300–400 millilitres (11–14 imp fl oz 10–14 US fl oz).

Storage phase

During storage, bladder pressure stays low, because of the bladder's highly compliant nature. A plot of bladder (intravesical) pressure against the depressant of fluid in the bladder (called a cystometrogram), will show a very slight rise as the bladder is filled. This phenomenon is a manifestation of the law of Laplace, which states that the pressure in a spherical viscus is equal to twice the wall tension divided by the radius. In the case of the bladder, the tension increases as the organ fills, but so does the radius. Therefore, the pressure increase is slight until the organ is relatively full. The bladder's smooth muscle has some inherent contractile activity however, when its nerve supply is intact, stretch receptors in the bladder wall initiate a reflex contraction that has a lower threshold than the inherent contractile response of the muscle.

Action potentials carried by sensory neurons from stretch receptors in the urinary bladder wall travel to the sacral segments of the spinal cord through the pelvic nerves. [6] Since bladder wall stretch is low during the storage phase, these afferent neurons fire at low frequencies. Low-frequency afferent signals cause relaxation of the bladder by inhibiting sacral parasympathetic preganglionic neurons and exciting lumbar sympathetic preganglionic neurons. Conversely, afferent input causes contraction of the sphincter through excitation of Onuf's nucleus, and contraction of the bladder neck and urethra through excitation of the sympathetic preganglionic neurons.

Diuresis (production of urine by the kidney) occurs constantly, and as the bladder becomes full, afferent firing increases, yet the micturition reflex can be voluntarily inhibited until it is appropriate to begin voiding.

Voiding phase

Voiding begins when a voluntary signal is sent from the brain to begin urination, and continues until the bladder is empty.

Bladder afferent signals ascend the spinal cord to the periaqueductal gray, where they project both to the pontine micturition center and to the cerebrum. [8] At a certain level of afferent activity, the conscious urge to void becomes difficult to ignore. Once the voluntary signal to begin voiding has been issued, neurons in pontine micturition center fire maximally, causing excitation of sacral preganglionic neurons. The firing of these neurons causes the wall of the bladder to contract as a result, a sudden, sharp rise in intravesical pressure occurs. The pontine micturition center also causes inhibition of Onuf's nucleus, resulting in relaxation of the external urinary sphincter. [9] When the external urinary sphincter is relaxed urine is released from the urinary bladder when the pressure there is great enough to force urine to flow out of the urethra. The micturition reflex normally produces a series of contractions of the urinary bladder.

The flow of urine through the urethra has an overall excitatory role in micturition, which helps sustain voiding until the bladder is empty. [10]

Many men, and some women, may sometimes briefly shiver after or during urination. [11]

After urination, the female urethra empties partially by gravity, with assistance from muscles. [ clarification needed ] Urine remaining in the male urethra is expelled by several contractions of the bulbospongiosus muscle, and, by some men, manual squeezing along the length of the penis to expel the rest of the urine.

For land mammals over 1 kilogram, the duration of urination does not vary with body mass, being dispersed around an average of 21 seconds (standard deviation 13 seconds), despite a 4 order of magnitude (1000×) difference in bladder volume. [12] [13] This is due to increased urethra length of large animals, which amplifies gravitational force (hence flow rate), and increased urethra width, which increases flow rate. For smaller mammals a different phenomenon occurs, where urine is discharged as droplets, and urination in smaller mammals, such as mice and rats, can occur in less than a second. [13] The posited benefits of faster voiding are decreased risk of predation (while voiding) and decreased risk of urinary tract infection.

Voluntary control

The mechanism by which voluntary urination is initiated remains unsettled. [14] One possibility is that the voluntary relaxation of the muscles of the pelvic floor causes a sufficient downward tug on the detrusor muscle to initiate its contraction. [15] Another possibility is the excitation or disinhibition of neurons in the pontine micturition center, which causes concurrent contraction of the bladder and relaxation of the sphincter. [6]

There is an inhibitory area for micturition in the midbrain. After transection of the brain stem just above the pons, the threshold is lowered and less bladder filling is required to trigger it, whereas after transection at the top of the midbrain, the threshold for the reflex is essentially normal. There is another facilitatory area in the posterior hypothalamus. In humans with lesions in the superior frontal gyrus, the desire to urinate is reduced and there is also difficulty in stopping micturition once it has commenced. However, stimulation experiments in animals indicate that other cortical areas also affect the process.

The bladder can be made to contract by voluntary facilitation of the spinal voiding reflex when it contains only a few milliliters of urine. Voluntary contraction of the abdominal muscles aids the expulsion of urine by increasing the pressure applied to the urinary bladder wall, but voiding can be initiated without straining even when the bladder is nearly empty.

Voiding can also be consciously interrupted once it has begun, through a contraction of the perineal muscles. The external sphincter can be contracted voluntarily, which will prevent urine from passing down the urethra.

Experience of urination

The need to urinate is experienced as an uncomfortable, full feeling. It is highly correlated with the fullness of the bladder. [16] In many males the feeling of the need to urinate can be sensed at the base of the penis as well as the bladder, even though the neural activity associated with a full bladder comes from the bladder itself, and can be felt there as well. In females the need to urinate is felt in the lower abdomen region when the bladder is full. When the bladder becomes too full, the sphincter muscles will involuntarily relax, allowing urine to pass from the bladder. Release of urine is experienced as a lessening of the discomfort.

Disorders

Clinical conditions

Many clinical conditions can cause disturbances to normal urination, including:

    , the inability to hold urine
      , incontinence as a result of external mechanical disturbances , incontinence that occurs as a result of the uncontrollable urge to urinate
    • Mixed incontinence, a combination of the two types of incontinence

    A drug that increases urination is called a diuretic, whereas antidiuretics decrease the production of urine by the kidneys.

    Experimentally induced disorders

    There are three major types of bladder dysfunction due to neural lesions: (1) the type due to interruption of the afferent nerves from the bladder (2) the type due to interruption of both afferent and efferent nerves and (3) the type due to interruption of facilitatory and inhibitory pathways descending from the brain. In all three types the bladder contracts, but the contractions are generally not sufficient to empty the viscus completely, and residual urine is left in the bladder. Paruresis, also known as shy bladder syndrome, is an example of a bladder interruption from the brain that often causes total interruption until the person has left a public area. These people (males) may have difficulty urinating in the presence of others and will consequently avoid using urinals without dividers or those directly adjacent to another person. Alternatively, they may opt for the privacy of a stall or simply avoid public toilets altogether.

    Deafferentation

    When the sacral dorsal roots are cut in experimental animals or interrupted by diseases of the dorsal roots such as tabes dorsalis in humans, all reflex contractions of the bladder are abolished. The bladder becomes distended, thin-walled, and hypotonic, but there are some contractions because of the intrinsic response of the smooth muscle to stretch.

    Denervation

    When the afferent and efferent nerves are both destroyed, as they may be by tumors of the cauda equina or filum terminale, the bladder is flaccid and distended for a while. Gradually, however, the muscle of the "decentralized bladder" becomes active, with many contraction waves that expel dribbles of urine out of the urethra. The bladder becomes shrunken and the bladder wall hypertrophied. The reason for the difference between the small, hypertrophic bladder seen in this condition and the distended, hypotonic bladder seen when only the afferent nerves are interrupted is not known. The hyperactive state in the former condition suggests the development of denervation hypersensitization even though the neurons interrupted are preganglionic rather than postganglionic.

    Spinal cord injury

    During spinal shock, the bladder is flaccid and unresponsive. It becomes overfilled, and urine dribbles through the sphincters (overflow incontinence). After spinal shock has passed, a spinally mediated voiding reflex ensues, although there is no voluntary control and no inhibition or facilitation from higher centers. Some paraplegic patients train themselves to initiate voiding by pinching or stroking their thighs, provoking a mild mass reflex. In some instances, the voiding reflex becomes hyperactive. Bladder capacity is reduced and the wall becomes hypertrophied. This type of bladder is sometimes called the spastic neurogenic bladder. The reflex hyperactivity is made worse, and may be caused, by infection in the bladder wall.

    Due to the positions where the urethra exits the body, males and females often use different techniques for urination.

    Male urination

    Most males prefer to urinate standing while others prefer to urinate sitting or squatting. Elderly males with prostate gland enlargement may benefit from sitting down while in healthy males, no difference is found in the ability to urinate. [17] [18] For practising Muslim men, the genital modesty of squatting is also associated with proper cleanliness requirements or awrah. [19]

    Female urination

    In human females, the urethra opens straight into the vulva. Hence, urination can take place while sitting or squatting for defecation. It is also possible for females to urinate while standing, and while clothed. [20] It is common for women in various regions of Africa to use this method when they urinate, [21] [22] [23] [ need quotation to verify ] [24] [25] [26] as do women in Laos. [27] [ failed verification ] Herodotus described a similar custom in ancient Egypt. [28] An alternative method for women to urinate standing is to use a tool known as a female urination device to assist. [29]

    Young children

    A common technique used in many developing nations involves holding the child by the backs of the thighs, above the ground, facing outward, in order to urinate. [ citation needed ]

    Fetal urination

    The fetus urinates hourly and produces most of the amniotic fluid in the second and third trimester of pregnancy. The amniotic fluid is then recycled by fetal swallowing. [30]

    Urination after injury

    Occasionally, if a male's penis is damaged or removed, or a female's genitals/urinary tract is damaged, other urination techniques must be used. Most often in such cases, doctors will reposition the urethra to a location where urination can still be accomplished, usually in a position that would promote urination only while seated/squatting, though a permanent urinary catheter may be used in rare cases. [ citation needed ]

    Alternative urination tools

    Sometimes urination is done in a container such as a bottle, urinal, bedpan, or chamber pot (also known as a gazunder). A container or wearable urine collection device may be used so that the urine can be examined for medical reasons or for a drug test, for a bedridden patient, when no toilet is available, or there is no other possibility to dispose of the urine immediately.

    An alternative solution (for traveling, stakeouts, etc.) is a special disposable bag containing absorbent material that solidifies the urine within seconds, making it convenient and safe to store and dispose of later. [ citation needed ]

    It is possible for both genders to urinate into bottles in case of emergencies. The technique can help children to urinate discreetly inside cars and in other places without being seen by others. [31]

    Toilet training

    Babies have little socialized control over urination within traditions or families that do not practice elimination communication and instead use diapers. Toilet training is the process of learning to restrict urination to socially approved times and situations. Consequently, young children sometimes suffer from nocturnal enuresis. [32]

    Facilities

    It is socially more accepted and more environmentally hygienic for those who are able, to urinate in a toilet. Public toilets may have urinals, usually for males, although female urinals exist, designed to be used in various ways. [20]

    Urination without facilities

    Acceptability of outdoor urination in a public place other than at a public urinal varies with the situation and with customs. Potential disadvantages include a dislike of the smell of urine, and some exposure of genitals. [ citation needed ] The latter can be unpleasant for the one who exposes them (modesty, lack of privacy) and/or those who can see them [ citation needed ] it can be avoided or mitigated by going to a quiet place and/or facing a tree or wall if urinating standing up, or while squatting, hiding the back behind walls, bushes, or a tree. [ citation needed ]

    Portable toilets (port-a-potties) are frequently placed in outdoor situations where no immediate facility is available. These need to be serviced (cleaned out) on a regular basis. Urination in a heavily wooded area is generally harmless, actually saves water, and may be condoned for males (and less commonly, females) in certain situations as long as common sense is used. Examples (depending on circumstances) include activities such as camping, hiking, delivery driving, cross country running, rural fishing, amateur baseball, golf, etc.

    The more developed and crowded a place is, the more public urination tends to be objectionable. In the countryside, it is more acceptable than in a street in a town, where it may be a common transgression. Often this is done after the consumption of alcoholic beverages, which causes production of additional urine as well as a reduction of inhibitions. One proposed way to inhibit public urination due to drunkenness is the Urilift, which is disguised as a normal manhole by day but raises out of the ground at night to provide a public restroom for bar-goers.

    In many places, public urination is punishable by fines, though attitudes vary widely by country. In general, females are less likely to urinate in public than males. Women and girls, unlike men and boys, are restricted in where they can urinate conveniently and discreetly. [33]

    The 5th-century BC historian Herodotus, writing on the culture of the ancient Persians and highlighting the differences with those of the Greeks, noted that to urinate in the presence of others was prohibited among Persians. [34] [35]

    There was [ when? ] a popular belief in the UK, that it was legal for a man to urinate in public so long as it occurred on the rear wheel of his vehicle and he had his right hand on the vehicle, but this is not true. [36] Public urination still remains more accepted by males in the UK, although British cultural tradition itself seems to find such practices objectionable. [37]

    In Islamic toilet etiquette, it is haram to urinate while facing the Qibla, or to turn one's back to it when urinating or relieving bowels but modesty requirements for females make it impossible for girls to relieve themselves without facilities. [38] [39] When toilets are unavailable, females can relieve themselves in Laos, Russia and Mongolia in emergency [40] but it remains less accepted for females in India even when circumstances make this a highly desirable option. [41]

    Women generally need to urinate more frequently than men due to having smaller bladders. [42] Resisting the urge to urinate because of lack of facilities can promote urinary tract infections which can lead to more serious infections and, in rare situations, can cause renal damage in women. [43] [44] Female urination devices are available to help women to urinate discreetly, as well to help them urinate while standing.

    Standing versus sitting or squatting

    Males

    In Western culture, the standing position is regarded by some as more comfortable and more masculine than the sitting or squatting option. [ citation needed ] However, in public restrooms without urinals and sometimes at home, men may be urged to use the sitting position as to diminish spattering of urine. [18] A systematic review meta-analysis of the effect of voiding position on the quality of urination found that in elderly males with benign prostate hyperplasia, the sitting position was superior compared with the standing. [45] [46] Healthy males were not influenced by voiding position.

    A literature review found cultural differences in socially accepted voiding positions around the world and found differences in preferred position: in the Middle-East and Asia, the squatting position was more prevalent, while in the Western world the standing and sitting positions were more common. [47]

    Females

    Females usually sit or squat for urination, depending on what type of toilet they use: A squat toilet is used for urination in a squatting position. If there is no toilet available then a squatting or a half squat position is common. A partial squatting position (or "hovering") is taken up during urination by some women to avoid sitting on a potentially contaminated toilet seat or when using a female urinal. However, this may leave urine behind in the bladder. [48] It can also result in urine landing on the toilet seat.

    Talking about urination

    In many societies and in many social classes, even mentioning the need to urinate is seen as a social transgression, despite it being a universal need. Even today, many adults avoid stating that they need to urinate. [49] [50]

    Many expressions exist, some euphemistic and some vulgar. For example, centuries ago the standard English word (both noun and verb, for the product and the activity) was "piss", but subsequently "pee", formerly associated with children, has become more common in general public speech. Since elimination of bodily wastes is, of necessity, a subject talked about with toddlers during toilet training, other expressions considered suitable for use by and with children exist, and some continue to be used by adults, e.g. "weeing", "doing/having a wee-wee", "to tinkle", "go potty". [ citation needed ]

    Other expressions include "squirting" and "taking a leak", and, predominantly by younger persons for outdoor female urination, "popping a squat", referring to the position many women adopt in such circumstances. National varieties of English show creativity. American English uses "to whiz". [51] Australian English has coined "I am off to take a Chinese singing lesson", derived from the tinkling sound of urination against the China porcelain of a toilet bowl. [52] British English uses "going to see my aunt", "going to see a man about a dog", "to piddle", "to splash (one's) boots", as well as "to have a slash", which originates from the Scottish term for a large splash of liquid. [53] One of the most common, albeit old-fashioned, euphemisms in British English is "to spend a penny", a reference to coin-operated pay toilets, which used (pre-decimalisation) to charge that sum. [54]

    Use in language

    References to urination are commonly used in slang. Usage in English includes:

      (to anger someone alternatively, to leave somewhere in a hurry)
    • Piss off! (to express contempt see above)
    • Pissing down (to refer to heavy rain) (an unproductive ego-driven battle)
    • Pisshead (vulgar way to refer to someone who drinks too much alcohol)
    • Piss ant (a worthless person in non-slang usage the term refers to several species of ant whose colonies have a urine-like odor)
    • Pissing up a flagpole (to partake in a futile activity)
    • Pissing into the wind (to act in ways that cause self-harm)
    • Piss away (to squander or use wastefully) (to take liberties, be unreasonable, or to mock another person)
    • Full of piss and vinegar (energetic or ambitious late adolescent or young adult male)
    • Piss up (British expression for drinking to get drunk)
    • Pissed (drunk in British English or angry in American English)

    Urination and sexual activity

    Urolagnia, a paraphilia, is an inclination to obtain sexual enjoyment by looking at or thinking of urine or urination. [55] Urine may be consumed, or the person may bathe in it. Drinking urine is known as urophagia, though uraphagia refers to the consumption of urine regardless of whether the context is sexual. Involuntary urination during sexual intercourse is common, but rarely acknowledged. In one survey, 24% of women reported involuntary urination during sexual intercourse in 66% of sufferers urination occurred on penetration, while in 33% urine leakage was restricted to orgasm. [56]

    Female kob may exhibit urolagnia during sex one female will urinate while the other sticks her nose in the stream. [57] [58]

    A male Patagonian mara, a type of rodent, will stand on his hind legs and urinate on a female's rump, to which the female may respond by spraying a jet of urine backwards into the face of the male. [59] The male's urination is meant to repel other males from his partner while the female's urination is a rejection of any approaching male when she is not receptive. [59] Both anal digging and urination are more frequent during the breeding season and are more commonly done by males. [60]

    A male porcupine urinates on a female porcupine prior to mating, spraying the urine at high velocity. [61] [62] [63] [64] [65]

    Wikimedia Commons has media related to Urinating animals .

    While the primary purpose of urination is the same across the animal kingdom, urination often serves a social purpose beyond the expulsion of waste material. [66] [67] In dogs and other animals, urination can mark territory or express submissiveness. [68] In small rodents such as rats and mice, it marks familiar paths.

    The urine of animals of differing physiology or sex sometimes has different characteristics. For example, the urine of birds and reptiles is whitish, consisting of a pastelike suspension of uric acid crystals, and discharged with the feces of the animal via the cloaca, whereas mammals' urine is a yellowish colour, with mostly urea instead of uric acid, and is discharged via the urethra, separately from the feces. Some animals' (example: carnivores') urine possesses a strong odour, especially when it is used to mark territory or communicate in other ways. [ clarify ]

    Stallions sometimes exhibit the Flehmen response by smelling the urine of a mare in heat. [69] A stallion sometimes scent marks his urination spots to make his position as herd stallion clear. [70] A male horse's penis is protected by a sheath when it is not in use for urination. [71]

    Ring-tailed lemurs have also been shown to mark using urine. Behaviorally, there is a difference between regular urination, where the tail is slightly raised and a stream of urine is produced, and marking behavior, where the tail is held up in display and only a few drops are used. [72] [73] The urine-marking behavior is typically used by females to mark territory, and has been observed primarily at the edges of the troop's territory and in areas where other troops may frequent. [74] The urine marking behavior is also most frequent during the mating season, and may play a role in reproductive communication between groups. [72] Many loris species also use urine for scent-marking. [75] [76] The white-headed capuchin sometimes engages in a practice known as "urine washing", in which the monkey rubs urine on its feet. [77] Urine washing, in which urine is rubbed on the hands and feet, is also used by the Panamanian night monkey. [78] In some cases, strepsirrhines may also anoint themselves with urine. [79]

    Hyenas do not raise their legs as canids do when urinating, as urination serves no territorial function for them. Instead, hyenas mark their territories using their anal glands, a trait found also in viverrids and mustelids, but not canids and felids. [80] Unlike other female mammals, female spotted hyenas urinate, copulate, and give birth through an organ called the pseudo-penis. [81] [82]

    Dog-like mammals (Canidae)

    All canids (with the possible exception of dholes [83] ) use urine (combined with preputial gland secretions) to mark their territories. Many species of canids, including hoary foxes, [84] cape foxes, [85] and golden jackals, [86] use a raised-leg posture when urinating. [87] [88] The scent of their urine is usually strongest in the winter, before the mating season. [88]

    Domestic dogs mark their territories by urinating on vertical surfaces (usually at nose level), sometimes marking over the urine of other dogs. [87] When one dog marks over another dog's urine, this is known as "counter-marking" or "overmarking". [89] [90] Male dogs urine-mark more frequently than female dogs, [91] typically beginning after the onset of sexual maturity. [92] Male dogs, as well as wolves, sometimes lift a leg and attempt to urinate even when their bladders are empty – this is known as a "raised-leg display", [93] [94] [95] [96] "shadow-urination", [97] or "pseudo-urination". [98] They typically mark their territory due to the presence of new stimuli or social triggers in a dog's environment, as well as out of anxiety. [99] Marking behavior is present in both male and female dogs, and is especially pronounced in male dogs that have not been neutered. [99]

    Raised-leg urination is the most significant form of scent marking in wolves, and is most frequent around the breeding season. [100] Wolves urine-mark more frequently when they detect the scent of other wolves, or other canid species. [101] Leg-lifting is more common in male wolves than female wolves, although dominant females also use the raised-leg posture. [102] Other types of urine-marking in wolves are FLU (flexed-leg urination), STU (standing urination), and SQU (squatting urination). [103] Breeding pairs of wolves will sometimes urinate on the same spot: this is known as "double-marking". [104] [105] [106] [107] [108] [109] Double-marking is practiced by both coyotes and wolves., [110] [111] [112] and also by foxes. [113]

    Coyotes mark their territories by urinating on bushes, trees, or rocks. [114] Male coyotes usually lift their legs when scent-marking. [115] However, females sometimes also raise their legs, and males sometimes squat. [116] Urine marking is also associated with pair bonding in coyotes [ clarification needed ] [117] Coyotes sometimes urinate on their food, possibly to claim ownership over it. [118]

    Red foxes use their urine to mark their territories. [119] [120] [121] [122] [123] A male fox raises one hind leg and his urine is sprayed forward in front of him, whereas a female fox squats down so that the urine is sprayed in the ground between the hind legs. [124] [125] Urine is also used to mark empty cache sites, as reminders not to waste time investigating them. [126] [127] [128] Red foxes use various postures [ clarify ] to urinate, depending on where they are leaving a scent mark. [124] [129]

    As in most other canids, male bush dogs lift their hind legs when urinating. However, female bush dogs use a kind of handstand posture, which is less common in other canids. [130] [131] When male bush dogs urinate, they create a spray instead of a stream. [132]

    Both male and female maned wolves use their urine to communicate, e.g. mark their hunting paths or places where they have buried hunted prey. [133] The urine has a very distinctive smell, which some people liken to hops or cannabis. The responsible substance is very likely a pyrazine, which occurs in both plants. [134] (At the Rotterdam Zoo, this smell once set the police on a hunt for cannabis smokers. [134] [135] )

    Cats (Felidae)

    Within the Felidae, male felids can urinate backwards by curving the tip of the glans penis backward. [136] [137] Urine marking by felids is also known as "spray-urinating" [138] or "spray-marking". [139] To identify their territories, male tigers mark trees by spraying urine [140] [141] and anal gland secretions, as well as marking trails with scat. Males show a grimacing face, called the Flehmen response, when identifying a female's reproductive condition by sniffing their urine markings.

    Lions use urine to mark their territories. They often scrape the ground while urinating, and the urine often flows in short spurts, instead of flowing continuously. They often urinate on vegetation, or on tree trunks at least one meter high. [142] Male lions spray 1–20 jets of urine at an angle of 20–30 degrees upward, at a range of up to 4 meters behind them. [143]

    Male cheetahs mark their territory by urinating on objects that stand out, such as trees, logs, or termite mounds. The whole coalition contributes to the scent. Males will attempt to kill any intruders, and fights result in serious injury or death. [144] When male cheetahs urine-mark their territories, they stand a meter away from a tree or rock surface with the tail raised, pointing the penis either horizontally backward or 60° upward. [145] The odor of cheetah urine (unlike that of other large felids) cannot be easily detected by humans. [139]

    Black-footed cats use scent marking throughout their ranges, with males spraying urine up to 12 times an hour. [146]


    When Will I Get My Results?

    Your doctor’s office will call in 1 to 3 days. They’ll go over the results with you.

    If you have an infection, you’ll likely be given antibiotics. If you are, be sure to complete the entire amount prescribed. Most of the time, the infection goes away. But it may come back, especially if you’re a sexually active woman. In young women, sexual intercourse increases the risk for an infection. The risk is higher in older men who have an enlarged prostate.

    It’s important to take your medicine the way your doctor tells you to. An infection that starts in the bladder or urethra can spread to the kidneys and damage them.

    Sources

    American Association of Clinical Chemistry: “Urine Culture.”

    National Institute of Diabetes and Digestive and Kidney Diseases: “Urinary Tract Infections (UTIs).”

    U.S. Library of Medicine: “Understanding Urine Tests.”

    Nemours Foundation: “Urine Test: Routine Culture.”

    National Kidney Foundation: “Urinary Tract Infections.”

    Harvard Medical School: “When Urinary Tract Infections Keep Coming Back.”


    Contents

    History Edit

    After the discovery and commercialization of antibiotics, microbiologist, pharmacologist, and physician Alexander Fleming developed the broth dilution technique using the turbidity of the broth for assessment. [7] This is commonly believed to be the conception point of minimum inhibitory concentrations. [8] Later in the 1980s, Clinical and Laboratory Standards Institute has consolidated the methods and standards for MIC determination and clinical usage. Following the discovery of new antibacterials, pathogens and their evolution, the protocols by CLSI are also continually updated to reflect that change. [9] The protocols and parameters set by CLSI are considered to be the "gold standard" in the United States and are used by regulatory authorities, such as the FDA, to make evaluations. [10]

    Clinical usage Edit

    Nowadays, the MIC is used in antimicrobial susceptibility testing. The MIC is reported by providing the susceptibility interpretation next to each antibiotic. The different susceptibility interpretations are: S (Sensitive), I (Intermediate), and R (Resistant). These interpretations were created and implemented by the Clinical and Laboratory Standards Institute (CLSI). In clinics, more often than not, exact pathogens cannot be easily determined by symptoms of the patient. Then, even if the pathogen is determined, different serotypes of pathogens, such as Staphylococcus aureus, have varying levels of resistance to antimicrobials. As such, it is difficult to prescribe correct antimicrobials. [11] The MIC is determined in such cases by growing the pathogen isolate from the patient on plate or broth, which is later used in the assay. [12] Thus, knowledge of the MIC will provide a physician valuable information for making a prescription. Accurate and precise usage of antimicrobials is also important in the context of multi-drug resistant bacteria. Microbes such as bacteria have been gaining resistance to antimicrobials they were previously susceptible to. [13] Usage of incompatible levels of antimicrobials provides the selective pressure that has driven the direction and evolution of resistance of bacterial pathogens. [14] This has been seen at sub-MIC levels of antibiotics. [15] As such, it is increasingly important to determine the MIC in order to make the best choice in prescribing antimicrobials.

    MIC is used clinically over MBC because MIC is more easily determined. [9] Minimum bactericidal concentration (MBC), which is the minimum antibacterial concentration resulting in microbial death, is defined by the inability to re-culture bacteria. In addition, drug effectiveness is generally similar when taken at both MIC and MBC concentrations because the host immune system can expel the pathogen when bacterial proliferation is at a standstill. [16] When the MBC is much higher than the MIC, drug toxicity makes taking the MBC of the drug detrimental to patient. Antimicrobial toxicity can come in many forms, such as immune hypersensitivity and off-target toxicity. [17]

    Broth dilution assay Edit

    There are three main reagents necessary to run this assay: the media, an antimicrobial agent, and the microbe being tested. The most commonly used media is cation-adjusted Mueller Hinton Broth, due to its ability to support the growth of most pathogens and its lack of inhibitors towards common antibiotics. [18] Depending on the pathogen and antibiotics being tested, the media can be changed and/or adjusted. The antimicrobial concentration is adjusted into the correct concentration by mixing stock antimicrobial with media. The adjusted antimicrobial is serially diluted into multiple tubes (or wells) to obtain a gradient. The dilution rate can be adjusted depending on the breakpoint and the practitioner's needs. The microbe, or the inoculating agent, must come from the same colony-forming unit, and must be at the correct concentration. This may be adjusted by incubation time and dilution. For verification, the positive control is plated in a hundred fold dilution to count colony forming units. The microbes inoculate the tubes (or plate) and are incubated for 16–20 hours. The MIC is generally determined by turbidity. [18]

    Etest Edit

    Etests can also be used as an alternative method to determine minimal inhibitory concentration values of a wide range of antimicrobial agents against different organism groups which has been widely used in microbiology laboratories around the world. Manufactured by bioMérieux, Etests are a ready-to-use, non-porous plastic reagent strip with a predefined gradient of antibiotic, covering a continuous concentration range. [19]


    1. DNA

    Samples should not be contaminated with other sources of DNA as any contaminant DNA will affect the data.

    The most commonly used method to determine the quality is the ratio of absorbance at 260-280 nm.

    Ratios around 1.8 means that it is good-quality, lower values indicate protein contamination, higher values indicate RNA contamination.

    To determine size, DNAs can be run on a gel.

    For an identity check of the DNA sample highly polymorphic microsatellite repeats can be determined and compared with another DNA source of the same sample. An example would be isolating DNA and comparing the alleles from both sources to see if it is from the same source.

    For maximum stability, DNA is usually stored in a Tris-EDTA solution.

    Short-term storage can be done at 4⁰C.

    Long-term storage samples should be kept at -80⁰C.

    Sealed vials can be used for storage as it provides minimal evaporation and therefore, maintains the necessary concentration while 96-well deep-well storage plates are used when there are larger numbers of samples.

    2. RNA

    The most important factors to remember for quality control of RNA are quantity, purity, and integrity.

    The quality of RNA can be determined by the ratio of absorbance which should have idea values between 1.9-2.1. This can be done using a spectrophotometer.

    Gel electrophoresis analysis should show bands of high molecular weight RNA that is between 7-15 kb in size, two predominant rRNA bands at approximately 5 kb (28s and 2 kb (18S) in a ratio of about 2:1, while the low molecular weight RNA is between 0.1-0.3 kb (tRNA, 5S). The integrity of the RNA can also be checked using a bioanalyzer.

    Long tern storage is ideal at -80⁰C, or as an ethanol precipitate at -20⁰C.

    One major concern for laboratories with large sample sizes are errors in sample identification and swapping.

    Due to errors in identification and swapping, bar code labels should be used instead of hand labeling.

    The use of robotics can also help minimize sample swapping.


    Urinalysis and Urine Culture

    Urinalysis, the testing of urine, may be necessary in the evaluation of kidney and urinary tract disorders and can also help evaluate bodywide disorders such as diabetes or liver problems. A urine sample is usually collected using the clean-catch method or another sterile method. For example, a method to obtain an uncontaminated urine sample involves passing a catheter through the urethra into the bladder.

    Urine cultures, in which bacteria from a urine sample are grown in a laboratory, are done to diagnose a urinary tract infection. Cultures are not part of routine urinalysis. The sample of urine must be obtained by the clean-catch method (see sidebar Obtaining a Clean-Catch Urine Sample) or by briefly inserting a sterile catheter through the urethra into the bladder.

    Obtaining a Clean-Catch Urine Sample

    The head of a man’s penis or opening of a woman’s urethra is cleansed, usually with a small pad that contains an antiseptic substance. Uncircumcised men should retract their foreskin to cleanse the head of the penis.

    The first few drops of urine are allowed to flow into the toilet, washing out the urethra.

    Urination is resumed, and a sample is collected from the stream into a sterile cup. Usually the sample is obtained before the stream ends (midstream).

    Chemical tests to detect and measure the level of various substances in the urine

    Often, examining urine under a microscope

    Chemical tests look for protein, glucose (sugar), ketones, blood, and other substances. These tests use a thin strip of plastic (dipstick) impregnated with chemicals that react with substances in the urine and quickly change color. Sometimes the test results are confirmed with more sophisticated and accurate laboratory analysis of the urine.

    Examining the urine under a microscope may be done to check for the presence of red and white blood cells, crystals, and casts (impressions of the kidney tubules created when urinary cells, protein, or both precipitate out in the tubules and are passed in the urine).

    Protein in the urine (proteinuria) can usually be detected by dipstick when present in large amounts. Protein may appear constantly or only intermittently in the urine, depending on the cause. Proteinuria may occur normally after strenuous exercise, such as marathon running, but is usually a sign of a kidney disorder. Small amounts of protein in the urine may be an early sign of kidney damage due to diabetes. Such small amounts may not be detected by dipstick. In these cases, urine will need to be collected over a period of 12 or 24 hours and tested by a laboratory.

    Glucose in the urine (glucosuria) can be accurately detected by dipstick. The most common cause of glucose in the urine is diabetes mellitus, but absence of glucose does not mean a person does not have diabetes or that the diabetes is well controlled. Also, presence of glucose does not necessarily indicate diabetes or another problem.

    Ketones in the urine (ketonuria) can often be detected by dipstick. Ketones are formed when the body breaks down fat. Ketones can appear in the urine as a result of starvation or uncontrolled diabetes mellitus and occasionally after drinking significant amounts of alcohol.

    Blood in the urine (hematuria) is detectable by dipstick and confirmed by viewing the urine with a microscope and other tests. Sometimes the urine contains enough blood to be visible, making the urine appear red or brown.

    Nitrites in the urine (nitrituria) are also detectable by dipstick. High nitrite levels indicate a urinary tract infection.

    Leukocyte esterase (an enzyme found in certain white blood cells) in the urine can be detected by dipstick. Leukocyte esterase is a sign of inflammation, which is most commonly caused by a urinary tract infection.

    The acidity (pH) of urine is measured by dipstick. Certain foods, chemical imbalances, and metabolic disorders may change the acidity of urine. Sometimes a change in acidity can predispose the person to kidney stones.

    The concentration of urine (also called the osmolality, roughly indicated by specific gravity) can vary widely depending on whether a person is dehydrated, how much fluid a person has drunk, and other factors. Urine concentration is also sometimes important in diagnosing abnormal kidney function. The kidneys lose their capacity to concentrate urine at an early stage of a disorder that leads to kidney failure. In one special test, a person drinks no water or other fluids for 12 to 14 hours. In another test, a person receives an injection of vasopressin (also called antidiuretic hormone). Afterward, urine concentration is measured. Normally, either test should make the urine highly concentrated. However, in certain kidney disorders (such as nephrogenic diabetes insipidus), the urine cannot be concentrated even though other kidney functions are normal.

    Sediment in urine can be examined under a microscope to provide information about a possible kidney or urinary tract disorder. Normally, urine contains a small number of cells and other debris shed from the inside of the urinary tract. A person who has a kidney or urinary tract disorder usually sheds more cells, which form a sediment if urine is spun in a centrifuge (a laboratory instrument that uses centrifugal force to separate components of a liquid) or allowed to settle.


    Urine Culture Stewardship in Patients without Indwelling Urinary Catheters

    The prevalence of asymptomatic bacteriuria (ASB) in patients without indwelling urinary catheters varies widely among groups and is more common in women, the elderly, those with urogenital abnormalities, institutionalized patients, and certain comorbidities. Treatment of ASB in these patients contributes significantly to antibiotic misuse.

    Here are some examples of appropriate and inappropriate uses of urine cultures that you can consider when drafting your list of facility-approved indications, other indications might exist at your facility:

    These examples are not meant to replace the clinical judgement of an individual treating provider. Decisions regarding patient diagnosis and management depend on individual patient characteristics and medical history. For example, conditions other than a bacterial urinary tract infection (UTI) may cause symptoms or pyuria additional investigation for nonbacterial causes of pyuria, including but not limited to sexually transmitted diseases, tuberculosis, interstitial cystitis, and carcinoma in situ of the bladder, may be warranted.

    Urine cultures may not be needed in cases of uncomplicated cystitis unless patient fails empiric treatment.


    Detecting Acid and Gas Production

    Culture media can be used to differentiate between different kinds of bacteria by detecting acid or gas production.

    Learning Objectives

    Show how microbial acid and gas production are detected

    Key Takeaways

    Key Points

    • Differential media uses the biochemical characteristics of a microorganism growing in the presence of specific nutrients or indicators.
    • To measure acid production one can use a pH indicator in the media.
    • The Durham tube method is used to detect production of gas by microorganisms.

    Key Terms

    • differential media: Differential media or indicator media distinguish one microorganism type from another growing on the same media.

    Cultures and Differential Media

    A microbiological culture, or microbial culture, is created using a method for multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory conditions. Microbial cultures are used to determine an organism’s type, its abundance in the sample being tested, or both. It is one of the primary diagnostic techniques of microbiology, where it is used as a tool to determine the cause of infectious diseases by letting the agent multiply in a predetermined medium. A throat culture, for example, is taken by scraping the lining of tissue in the back of the throat and blotting the sample into a growing medium this will allow analysis to screen for harmful microorganisms, such as Streptococcus pyogenes, the causative agent of strep throat. The term “culture” can be used to refer to the process of culturing organisms, to the medium they’re grown in, and is more generally used informally to refer to “selectively growing” a specific kind of microorganism in the lab.

    Differential media, also known as indicator media, distinguish one microorganism type from another growing on the same media. These types of media use the biochemical characteristics of a microorganism grown in the presence of specific nutrients or indicators that have been added to the medium to visibly indicate the defining characteristics of a microorganism. These indicators or nutrients include but are not limited to neutral red, phenol red, eosin y, and methylene blue. Differential media are used for the detection of microorganisms and by molecular biologists to detect recombinant strains of bacteria.

    Durham Cultures

    The Durham tube method is used to detect production of gas by microorganisms. They are simply smaller test tubes inserted upside down in another test tube. This small tube is initially filled with the solution in which the microorganism is to be grown. If gas is produced after inoculation and incubation, a visible gas bubble will be trapped inside the small tube. The initial air gap produced when the tube is inserted upside down is lost during sterilization, usually performed at 121°C for 15 or so minutes

    Escherichia coli

    Escherichia coli (E. coli), a rod-shaped member of the coliform group, can be distinguished from most other coliforms by its ability to ferment lactose at 44°C in the fecal coliform test, and by its growth and color reaction on certain types of culture media. When cultured on an EMB (eosin methylene blue) plate, a positive result for E. coli is metallic green colonies on a dark purple media. Unlike the general coliform group, E. coli are almost exclusively of fecal origin and their presence is thus an effective confirmation of fecal contamination. Some strains of E. coli can cause serious illness in humans.

    Sorbitol MacConkey Agar

    Sorbitol MacConkey agar is a variant of the traditional MacConkey commonly used in the detection of E. coli O157:H7. Traditionally, MacConkey agar has been used to distinguish those bacteria that ferment lactose from those that do not.

    Using differential media to detect acid production: Sorbitol fermenting non pathogenic commensal bacteria from faeces growing on Cefixime Tellurite Sorbitol MacConkey Agar.

    This is an important distinction. Gut bacteria, such as Escherichia coli, can typically ferment lactose important gut pathogens including Salmonella enterica and most shigellas are unable to ferment lactose. Shigella sonnei can ferment lactose, but only after prolonged incubation it is referred to as a late-lactose fermenter.

    During fermentation of sugar, acid is formed and the pH of the medium drops, changing the color of the pH indicator. Different formulations use different indicators neutral red is often used when culturing gut bacteria because lactose fermenters turn a deep red when this pH indicator is used. Those bacteria unable to ferment lactose, often referred to as nonlactose fermenters (NLFs) metabolize the peptone in the medium. This releases ammonia, which raises the pH of the medium. Although some authors refer to NLFs as being colorless, in reality they turn neutral red a buffish color.

    E. coli O157:H7 differs from most other strains of E. coli in being unable to ferment sorbitol. In sorbitol MacConkey agar, lactose is replaced by sorbitol. Most strains of E. coli ferment sorbitol to produce acid: E. coli O157:H7 can not ferment sorbitol, so this strain uses peptone to grow. This raises the pH of the medium, allowing the O157:H7 strain to be differentiated from other E. coli strains through the action of the pH indicator in the medium.


    Watch the video: Testing an Antibiotic Using a Disk Diffusion Assay - Kirby Bauer Method (May 2022).


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