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Urinary Tract Infections Sina Mobasherizadeh Ph.D Candidate of Bacteriology IUMS Urinary tract infection A urinary tract infection (UTI) is an infection that involves any of the organs or structures of the urinary tract, including the kidneys, ureters, bladder, and urethra. Some of the common symptoms of a urinary tract infection are burning or pain in the lower abdomen, fever, burning during urination, or an increase in the frequency of urination. UTIs are the most common type of healthcare-associated infection (HAI) and are most often caused by the placement or presence of a catheter in the urinary tract. 2 [email protected] 5/23/2017 3 [email protected] 5/23/2017 4 [email protected] 5/23/2017 Uncomplicated UTIs occur primarily in sexually active young women with normal GU tracts and no prior instrumentation and are usually caused by antibiotic-susceptible bacteria. Complicated UTls occur in individuals who have one or more structural or functional GU abnormalities or have indwelling catheters and whose conditions cannot be controlled with therapy. Bacteriuria, which can be symptomatic or asymptomatic, is the presence of bacteria in the urine. Asymptomatic bacteriuria (ASB) is the isolation of bacteria from the urine insignificant quantities, but without GU signs or symptoms of infection. ASB requires treatment only in some populations, such as pregnant women and patients about to undergo instrumentation of the GU tract. 5 [email protected] 5/23/2017 Signs and Symptoms of Upper Urinary Tract Infection • Fever and chills (systemic reaction) • Flank pain • Lower urinary tract signs and symptoms (frequency, urgency, and dysuria) Signs and Symptoms of Lower Urinary Tract Infection • Frequent and painful urination of small volumes of turbid urine • Inflammatory irritation of urethral and bladder mucosa • Occasional suprapubic pain or sensation of heaviness • Fever generally absent Catheter-associated urinary tract infection (CAUTI) A catheter-associated urinary tract infection (CAUTI) are the most common type of healthcare-associated infection, accounting for more than 30% of infections reported by acute care hospitals. CAUTIs have been associated with increased morbidity, mortality, healthcare costs, and length of stay. The risk of CAUTI can be reduced by ensuring that catheters are used only when needed and removed as soon as possible; that catheters are placed using proper aseptic technique. The clinical significance of ASB in catheterized patients is undefined. Approximately 75% to 90% of patients with ASB do not develop a systemic inflammatory response or other signs or symptoms to suggest infection 8 [email protected] 5/23/2017 Epidemiology Between 15% and 25% of hospitalized patients may receive short-term indwelling urinary catheters. fewer than 5% of bacteriuric cases develop bacteremia, CAUTI is the leading cause of secondary nosocomial bloodstream infections; about 17% of hospital-acquired bacteremias are from a urinary source, with an associated mortality of approximately 10%. UTIs in kidney transplant recipients most often present as cystitis, however, pyelonephritis may occur in almost 25% of them and can lead to allograft injury. may be responsible for more than 50% of bacteremias in this population. An estimated 17% to 69% of CAUTI may be preventable with recommended infection control measures, which means that up to 380,000 infections and 9000 deaths related to CAUTI per year could be prevented. 9 [email protected] 5/23/2017 Pathogenesis and Microbiology The source of microorganisms causing CAUTI can be endogenous, typically via rectal, or vaginal colonization, or exogenous, such as via contaminated hands of healthcare personnel or equipment. The daily risk of bacteriuria with catheterization is 3% to 10%, approaching 100% after 30 days. Formation of biofilms by urinary pathogens on the surface of the catheter occurs universally with prolonged duration of catheterization. 10 [email protected] 5/23/2017 Microbiological agents The most frequent pathogens associated with CAUTI (combining both ASB and SUTI) in hospitals reporting to NHSN (National Healthcare Safety Network)between 2006-2007 were : Escherichia coli (21.4%) and Candida spp (21.0%), followed by Enterococcus spp (14.9%), Pseudomonas aeruginosa (10.0%), Klebsiella pneumoniae (7.7%), and Enterobacter spp (4.1%). A smaller proportion was caused by other gram-negative bacteria and Staphylococcus spp. 11 [email protected] 5/23/2017 12 [email protected] 5/23/2017 13 [email protected] 5/23/2017 Antimicrobial resistance Antimicrobial resistance among urinary pathogens is an ever increasing problem. About a quarter of E. coli isolates and one third of P. aeruginosa isolates from CAUTI cases were fluoroquinolone-resistant. Resistance of gram-negative pathogens to other agents, including third-generation cephalosporins and carbapenems, was also considerable . The proportion of organisms that were multidrug-resistant, defined by non-susceptibility to all agents in 4 classes, was 4% of P. aeruginosa, 9% of K. pneumoniae, and 21% of Acinetobacter baumannii. 14 [email protected] 5/23/2017 EPIDEMIOLOGY AND RISK FACTORS Age Pediatrics Adults to Age 65 Geriatrics Institutionalized Care Pregnancy Bladder Catheterization 15 [email protected] 5/23/2017 Pediatrics: • During the neonatal period, about I% of all babies have bacteria in bladder urine; the incidence is higher in boys, and bacteremia often is present. • Non circumcised males younger than 6 months of age have a 12-fold increased risk of UTI compared with circumcised cohorts. • Among preschool-aged children, girls develop UTIs more often than boys, and infection frequently is associated with severe congenital abnormalities. These infections are often asymptomatic. 16 [email protected] 5/23/2017 Adults to Age 65 the incidence of UTIs in men is extremely low. Infections associated : with anatomic abnormalities or prostatic disease and the consequent instrumentation, such as catheterization. women :as many as one fifth experience a symptomatic UTI. In terms of antibacterial activity, urine from men is more inhibitory than urine from women because of the presence of prostatic fluids in the urine of men, and the difference in pH and osmolarity. 17 [email protected] 5/23/2017 Geriatrics The diagnosis and management of UTI in the geriatric population can be challenging. Older adults frequently have an atypical clinical presentation including delirium, fevers alone, or failure to thrive. the incidence of UTIs increases dramatically for both genders, and the female to-male ratio progressively declines. The increased incidence of UTIs in men arises from obstructive uropathologic conditions caused by the loss of the bactericidal activity of prostate secretions. In women, bladder prolapse contributes to the occurrence of infection, as does soiling of the perineum from fecal incontinence in women afflicted with dementia. In both genders, neuromuscular disease and increased instrumentation and bladder catheterization are contributing factors. 18 [email protected] 5/23/2017 Pregnancy Pregnant women are at higher risk for UTI for several reasons. Hormonal changes lead to changes in the ureter and urethra, making them more susceptible to bacterial adherence and infection. The enlarging uterus can put pressure on the bladder and impair urinary flow. Asymptomatic bacteriuria in pregnant women should be treated because infection can lead to premature labor. Susceptibility testing is particularly important in this patient population because not all antibiotics can be given to pregnant women. 19 [email protected] 5/23/2017 20 [email protected] 5/23/2017 Specimen Collection Preventing contamination by normal vaginal, perianal, and interior urethral flora is the most important consideration in collecting a clinically relevant urine specimen The voided midstream collection, in which the patient collects the urine specimen, is the most commonly used method in clinical practice. The urine is contaminated with bacteria from the urethra unless the first portion of the voided specimen is discarded. 21 [email protected] 5/23/2017 Catheterized Specimen Collection When specimens are collected from an existing, indwelling urinary catheter, the catheter collection port should be cleaned with an alcohol pad and punctured directly with a needle and syringe. The specimen should never be collected from the drainage bag. 22 [email protected] 5/23/2017 straight catheter Before collecting urine with a single, straight catheter, the urethral opening or vaginal vault is cleansed with a soap solution and rinsed with sterile water. Ileal Conduit Samples obtained from an ileoconduit are collected from the stoma opening after the area has been swabbed with an alcohol wipe. The urine on the external appliance is never used for culture, because it is similar to the urine in a drainage bag in patients with indwelling catheters. 23 [email protected] 5/23/2017 Suprapubic Aspiration Suprapubic aspiration is the definitive method for collecting uncontaminated specimens. Although most consider any organism isolated on these specimens to be clinically significant, this may not be correct because transient colonization of the bladder can occur. Suprapubic aspirations are collected : Infants Patients in whom the interpretation of the results of voided specimens is difficult. Anaerobic culture. With the bladder full, the urine is collected with a needle and syringe following skin antisepsis 24 [email protected] 5/23/2017 Specimen Transport Urine is an excellent supportive medium for the growth of most uropathogens and therefore must be immediately refrigerated or preserved. Generally, urine should be refrigerated, received, and processed in the laboratory within 2 hours. Longer delays render examination for significant pyuria unreliable, and the extremes of pH and urea concentration and the presence of antimicrobial agents may adversely affect the recovery of uropathogens. 25 [email protected] 5/23/2017 MICROBIAL DETECTION Microscopy Uncentrifuged urine samples may be used for a stained smear. The presence of one or more bacterial cells per oil immersion field in at least five fields in a smear of uncentrifuged urine correlates with more than 100000CFU/mL. If the uncentrifuged preparation tests negative, the sedimented preparation for leukocyte examination should be stained. 26 [email protected] 5/23/2017 Detection of Pyuria Detection of leukocytes may be performed by microscopic examination of a wet mount of a urinary sediment resulting from centrifugation of 10 mL of a specimen at 2000-2500 rpm on a tabletop centrifuge for 5 minutes. At least five fields should be examined, and each leukocyte seen per highpower field (hpf) (40x) represents approximately 5 to 10 cells per cubic millimeter of urine. In this way, 5 to 10 leukocytes/hpf in the sediment is the upper limit of normal, representing 50 to 100cells/mm3 27 [email protected] 5/23/2017 Chemical Methods WBC leukocyte esterase test White blood cells in the urine usually indicate a urinary tract infection. A positive leukocyte esterase test indicates the presence of granulocytic white blood cells. Lymphocytes do not contain granules, and would not produce a positive leukocyte esterase test. False Positives: •Females due to contamination of the specimen by vaginal discharge. •The presence of strong oxidizing agents in the collection container. •The presence of trichomonas and eosinophils. False Negatives: •The presence of significant levels of protein or glucose and in urines with high specific gravity. • The presence of ascorbic acid •The presence of boric acid in the collection container. • Some drugs such as Cephalexin ,Cephalothin, Tetracycline, or high concentrations of oxalic acid. 28 [email protected] 5/23/2017 A nitrite test is a standard component of a urinary test strip. A positive test for nitrites in the urine is called nitrituria. A positive nitrite test indicates that the cause of the UTI is a gram egative organism, most commonlyEscherichia coli. False negative: • nitrite tests in urinary tract infections occur in cases with a low colony forming unit count, or in recently voided or dilute urine. •The presence of high ascorbic acid •PH< 6 • In addition, a nitrite test does not detect organisms unable to reduce nitrate to nitrite, such as enterococci, staphylococci, or adenovirus •False Positive •Use of Phenazopyridine 29 [email protected] 5/23/2017 Rejection Criteria Specimens may be rejected because of an inadequate or inappropriate method of collection or transport. Samples to be rejected include 24-hour urine specimens. Antibiotic therapy may not have been initiated. 30 [email protected] 5/23/2017 LABORATORY DIAGNOSIS Significance of Colony Counts: Since 1956, the interpretation of quantitative urine cultures has been considered one of the more straightforward and simpler laboratory tests to diagnose UTls. It was "dogma“ that a finding of 100,000 (105)colony-forming units per milliliter (CFU/mL) or more was a "positive" test result symbolizing infection. hence the 105CFU/mL so-called "cut off" positive infection point. 31 [email protected] 5/23/2017 Culture for Etiologic Agents of Urinary Tract Infections Generally, routine urine culture should include plating onto one selective (e.g., MAC) and one nonselective medium. Calibrated loops of 0.0 I mL should be used, not 0.00 I mL loops, because quantitation is difficult to obtain with a low inoculum. The urine specimen should be mixed thoroughly and the calibrated loop should be inserted vertically; inserting the loop in a more horizontal position may increase the volume beyond calibration; it should also be observed visually for bubbles that would decrease the volume. 32 [email protected] 5/23/2017 33 [email protected] 5/23/2017 34 [email protected] 5/23/2017 35 [email protected] 5/23/2017 36 [email protected] 5/23/2017