 list the main microorganisms responsible from UTI  explain the importance of significant bacteriuria and quantitative culture method  List the main advantages and disadvantages of each type ofsample for the laboratory diagnosis  List the laboratory tests for UTI

 Urinary tract infections are common, especially among women  20-30% of women have recurrent urinary tract infections (UTI) at some time in their life.  UTIs in men are less common and primarily occur after 50 years of age.

 Although the majority of infections are  acute  short-lived  they contribute to a significant amount of morbidity in the population.

 Severe infections result in a loss of renal function and serious long-term sequelae.  In females, a distinction is made between cystitis, urethritis and vaginitis, but the genitourinary tract is a continuum and the symptoms often overlap.

 Coagulase negative staphylococci  Viridans nonhemolytic streptococci  Lactobacilli ♀  Diphtheroids  Non pathogenic Neisseria species  Commensal Mycobacterium species  Yeasts

 Bacterial infection :  usually acquired by the ascending route from the urethra to the bladder  The infection may then proceed to the kidney.  Occasionally, bacteria infecting the urinary tract invade the bloodstream to cause septicemia.

 Bacterial infection :  Less commonly, infection may result from hematogenous spread of an organism to the kidney  with the renal tissue being the first part of the tract to be infected.

 From an epidemiological viewpoint,  UTIs occur in two general settings: 1-community-acquired and 2-hospital (nosocomially) acquired, most often being associated with catheterization. Hospital-acquired UTIs, while less common than community acquired, contribute significantly to overall nosocomial infection rates.

 The Gram-negative rods:  Escherichia coli (the commonest cause of ascending UTI )  Other members of the Enterobacteriaceae: -Proteus mirabilis -Klebsiella, Enterobacter, Serratia spp. and Pseudomonas aeruginosa

 The Gram-negative rods:  Enterobacteriaceae: -Proteus mirabilis: associated with urinary stones (calculi), probably because this organism produces a potent urease, which acts on urea to produce ammonia, rendering the urine alkaline.

 The Gram-negative rods:  Enterobacteriaceae: -Klebsiella, Enterobacter, Serratia spp. and Pseudomonas aeruginosa : are more frequently found in hospital- acquired UTI because their resistance to antibiotics favors their selection in hospital patients

 Gram-positive species  Staphylococcus saprophyticus : ◦ especially in young sexually active women.  Staphylococcus epidermidis and  Enterococcus species are more often associated with UTI in hospitalized patients (especially those with AIDS), where multiple antibiotic resistance can cause treatment difficulties.

 Gram-positive species  corynebacteria and lactobacilli  Obligate anaerobes: very rarely

 Hematogenous spread to the urinary tract:  other species may be found:  Salmonella typhi,  Staphylococcus aureus  Mycobacterium tuberculosis (renal tuberculosis).

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 rare  hemorrhagic cystitis and other renal syndromes

 may be recovered from the urine in the absence of urinary tract  The human polyomaviruses, JC and BK  cytomegalovirus (CMV) and  rubella

 Adenovirus:hemorrhagic cystitis  The rodent-borne hantavirus  mumps and HIV

 Candida spp. and  Histoplasma capsulatum  The protozoan: Trichomonas vaginalis  Schistosoma haematobium : hematuria.

 A variety of mechanical factors predispose to UTI  Pregnancy, prostatic hypertrophy, renal calculi, tumors and strictures are the main causes of obstruction to complete bladder emptying  Catheterization is a major predisposing factor for UTI  A variety of virulence factors are present in the causative organisms  The healthy urinary tract is resistant to bacterial colonization

 A key feature is the detection of significant bacteriuria.  Infection can be distinguished from contamination by quantitative culture methods

 the urinary tract is sterile,  the distal region of the urethra is colonized with commensal organisms,  which may include periurethral and fecal organisms.  As urine specimens are usually collected by voiding a specimen into a sterile container, they become contaminated with the periurethral flora during collection.  Infection can be distinguished from contamination by quantitative culture methods.

 the urinary tract is sterile,  the distal region of the urethra is colonized with commensal organisms,  which may include periurethral and fecal organisms.  As urine specimens are usually collected by voiding a specimen into a sterile container, they become contaminated with the periurethral flora during collection. Midstream urine (MSU)  Infection can be distinguished from contamination by quantitative culture methods.

 is defined as 'significant' when a properly collected midstream urine (MSU) specimen is shown to contain over 10 5 organisms/ml.  Infected urine usually contains only a single bacterial species.  Contaminated urine usually has <10 4 organisms/ml and often contains more than one bacterial species  Distinguishing infection from contamination when counts are organisms/ml can be difficult.

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 urine specimens collected from:  Catheters  nephrostomy tubes  suprapubic aspiration directly from the bladder:  any number of organisms may be significant because the specimen is not contaminated by periurethral flora.

 Infection of sites in the urinary tract below the bladder  by organisms that are not members of the normal fecal flora:  may not lead to the presence of significant numbers in the urine.

 Difficult  'Bag urine' may be collected by sticking a plastic bag to the perineum in girls or to the penis in boys  After 30 minutes the bag should be renewed  such specimens are frequently heavily contaminated with fecal organisms.

 with minimum delay  because urine is a good growth medium  for many bacteria and multiplication of organisms in the specimen between collection and culture will distort the results

 Should be collected in the morning or letting the urine to be collected for four hours  should be collected before antimicrobial therapy is started.  If the patient is receiving, or has received, therapy within the previous 48 h, this should be stated clearly on the request form.

 a catheter specimen of urine is used  Patients should not be catheterized simply to obtain a urine sample.

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 M. tuberculosis  Schistosoma haematobium

 M. tuberculosis  three early morning urine samples on consecutive days

 S. haematobium  the last few ml of a late morning urine sample collected after exercise

 Microscopic examination of urine allows a rapid preliminary report  Bacteria may be seen on microscopy when present in the specimen in large numbers.  However, they are not necessarily indicative of infection,  but may indicate that the specimen has been poorly collected or left at room temperature for a prolonged period of time.

 Microscopic examination of urine  The presence of red and white blood cells, although abnormal, is not necessarily indicative of UTI.

 infection of the urinary tract and elsewhere (e.g. bacterial endocarditis)  renal trauma  calculi  urinary tract carcinomas  clotting disorders  thrombocytopenia  Occasionally, red blood cells may contaminate urine specimens of menstruating women.

 White blood cells are present in the urine in very small numbers (e.g. <10/ml) in health  a count of over 10/ml is considered abnormal, but is not always associated with bacteriuria.

 Sterile pyuria is an important finding and may reflect: concurrent antibiotic therapy  other diseases such as neoplasms or urinary calculi  infection with organisms not detected by routine urine culture methods.  Renal tubular cells, seen in the urine of aspirin-misusers, may be confused with white blood cells. Urinary casts are also indicative of renal tubular damage.

 A laboratory diagnosis of significant bacteriuria requires quantification of the bacteria  Conventional culture methods produce results within h, but rapid methods (e.g. based on bioluminescence, turbidimetry, leukocyte esterase/nitrate reductase test, etc.) are also available.

 storage - the urine must be cultured within 1 h of collection or held at 4°C for not more than 18 h before culture  antibiotic treatment - in a patient receiving antibiotics, smaller numbers of organisms may be significant and may represent an emerging resistant population; simple laboratory methods are available to detect antibacterial substances

 fluid intake - the patient may be taking more or less fluid than usual, and this will clearly influence the quantitative result  the specimen - the quantitative guidelines are valid for MSU specimens; they do not apply to catheter specimens, suprapubic aspirates or nephrostomy samples.

 1. Microscopy  2. Quantitative culture  3. Susceptibility testing

 Gram staining→ presence of leukocytes and microorganisms

 microscopic examination:  Presence of significant number of bacteria in uncentrifuged urine sample–high magnifaction power in immersion field; x1000- with Gram stain): ≥ 1 bacterium or bacteria/high power field.  conventionally accepted to correspond ≥10 5 CFU/mL)

 Culture: Presence of significant number of bacteria inuncentrifuged urine sample (quantitative culture result): ≥ 10 3 to ≥10 5 CFU/mL

 Bacteria/ no.of coloni  In asemptomatic patients  10 5 cfu/ml (male 10 4 ): identification and antibiotic susceptibility test (AST)  cfu/ml : contact with clinician if >2 bacteria is seen  10 2 cfu/ml : significant if it is taken from catheter  10 cfu/ml: significant if its suprapubic aspiration

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 E. coli (%50-90)  Other Enterobacteriaceae  S. saphrophyticus ( ♀ )  P. aeruginosa  Enterococcus spp.  Other CNS

 For asymptomatic women, bacteriuria is defined as -2 consecutive voided urine specimens -isolation of the same bacterial strain in quantitative counts 10 5 cfu/mL  Pregnant women should be screened for bacteriuria by urine culture at least once in early pregnancy, and they should be treated if the results are positive