Uti Urinary Tract Infection

Urinary Tract Infections
MLAB 2434 Clinical Microbiology Cecile Sanders & Keri Brophy-Martinez
Definitions

UTI = Urinary Tract Infection Upper UT includes renal parenchyma (pyelonephritis) and ureters (ureteritis) Lower UT includes bladder (cystitis), urethra (urethritis), and, in males, the prostrate (prostatitis) Bacteriuria = presence of bacteria in urine; may be symptomatic or asymptomatic
Urinary System
Except for urethral mucosa and renal medulla, the urinary tract efficiently and rapidly eliminates microorganisms Conditions such as high ammonia concentration, hyperosmolarity, lowered pH, and sluggish blood flow in renal medulla can contribute to reduced leukocyte chemotaxis and bactericidal activity of WBCs
Risk Factors
Age
Infants to Pre-school age

Girls infected more than boys Most renal damage due to UTI at this age
School-age children
Presence of bacteria in urine defines population at higher risk for development of UTIs in adulthood Girls more prone to develop UTI upon sexual activity
Risk Factors (contd)
Age (contd)
Adults to 65
UTIs in men extremely low, except with anatomic abnormalities or prostate disease or as a result of instrumentation 20% of women in this age group experience symptomatic UTI
Age (contd)
Over age 65 and residence in longterm care facility

UTIs increase dramatically in both genders Males prostate changes and increased catherization Women fecal soiling, neuromuscular disease, and increased catheterization
Inpatient Care
Hospitals and nursing homes More prone to UTIs due to pathologic conditions and higher probability of urinary tract instrumentation
Clinical Signs and Symptoms

Infants and children < 2 years age have nonspecific symptoms > 2 years are more likely to have localized symptoms (dysuria, frequency, abdominal or flank pain) Adults with lower UT infections have dysuria, frequency, urgency, and sometimes suprapubic tenderness
Clinical Signs and Symptoms (contd)
Upper UTIs, especially with acute pyelonephritis, include LUTI symptoms along with flank pain and tenderness and fever AGN (Acute Glomerulonephritis) results from immune response to S. pyogenes (Group A) infections, either respiratory or pyodermal
Edema around eyes Hematuria RBC and WBC casts
Etiology of UTIs
Pathogenesis of UTI
Three access routes

Ascending (most significant) Hematogenous Lymphatic
UTI Agents
G- Bacilli E. coli Pseudomonas, Proteus, Klebsiella, & Enterobacter sp. G+ Cocci Enterococcus more commonly in
older men
S. saprophyticus sexually active

young women
UTI Agents (contd)
G+ Bacilli Bacillus is a contaminant Others (Mycobacterium, Listeria, Clostridium) Fungi Some powerful STIs will produce UTIs (Ex. N. gonorrhoeae, C. trachomatis, Gardenella vaginalis) Viruses
Specimen Collection
Need to collect specimen to prevent normal vaginal, perianal, and urethral flora Mid-stream clean catch if self collected, patient needs GOOD instructions Catheterized Suprapubic aspiration
Specimen Collection (contd)

Additives even with additive, time from collection to processing should not exceed 24 hours Dip-slide urine collection better for physician offices Transport if not refrigerated or preserved, urine should be refrigerated
Specimen Screening
Manual screening

5 to 10 WBC/hpf is upper limit of normal Chemical screening

Leukocyte Esterase and Nitrate on urine dipstick
Automated methods expensive, except in large volume labs 24 hour urines and Foley catheter tips must be rejected for culture
Culture and Interpretation

Inoculation using either a 0.001 ml (x1000) OR a 0.01 ml (x100) loop Interpretation of urine cultures is determined by medical staff of hospital
Culture and Interpretation (contd)
Textbook algorithm
Specimen with three organisms is probably contamination and should not be identified unless specifically requested by physician One or two pathogens 100,000 CFU/ml should be identified and sensitivities done One or two pathogens 100 CFU/ml should be identified only if clinical situation warrants or specimen is catheterized or suprapubic aspiration

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Urinary Tract Infections

MLAB 2434 Clinical Microbiology Cecile Sanders & Keri Brophy-Martinez

Infants to Pre-school age

Risk Factors (contd)

Risk Factors (contd)

Over age 65 and residence in longterm care facility

Risk Factors (contd)

Clinical Signs and Symptoms

Clinical Signs and Symptoms (contd)

Edema around eyes Hematuria RBC and WBC casts

Three access routes

S. saprophyticus sexually active

UTI Agents (contd)

Specimen Collection (contd)

5 to 10 WBC/hpf is upper limit of normal Chemical screening

Culture and Interpretation

Culture and Interpretation (contd)

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