Urinary Tract Infections Flashcards
Urinary Tract Infections (General)
- very common bacterial infection
- more frequent in women due to anatomic difference
- can be single, recurrent, uncomplicated or complicated
- Urinary tract normally resistant to infection due to urine characteristics
Upper UTI’s
infection of renal parenchyma or ureters
Lower UTI’s
infection of bladder, urethra or prostate (males)
Recurrent UTI’s
- Relapse: re-infection with the same bacteria
- Reinfection: second UTI infection by different organism
Uncomplicated UTI’s
UTI’s in sexually active women with normal GU tracts; no procedures
Complicated UTI’s
UTI’s due to one or more structural or functional abnormalities
Urine infection resistance
- extremely high osmolarity to inhibit growth of most organisms
- low pH
- dilute urine grows less
- prostatic fluid (men)
- flow has washing affect to inhibit adherence
UTI Risk factors
- AGE (kids with long-term medical problems, adults with GU abnormalities, elderly because of catheterization, prostate problems, bladder prolapse)
- INSTITUTIONALIZE CARE (catheters, asymptomatic bacteruria)
- PREGNANCY (increased ASB)
- RENAL TRANSPLANT (leads to septicemia)
- BLADDER CATHETERIZATION
Route of Infection
- Ascending route: most common route, migration from bladder, acquired UTI’s
- Descending route: infection via blood, < 5% of UTI’s
UTI’s (Clinical Signs/Symptoms)
- failure to thrive, vomiting, lethargy, fever in kids < 2 y/o
- dysuria, frequency and abdominal/flank pain in kids
- dysuria, frequency, urgency, suprapubic pain, hematuria in adults
- fever, costovertebral angle tenderness, flank pain, chills, vomiting in upper UTI’s
Infections in urine cultures that aren’t UTI’s
- Herpes simplex (HSV)
- Chlamydia trachomatis
- Neisseria gonorrhoeae
UTI pathogenesis (women)
- infection via ascending route
- due to shorter ureter
UTI pathogens
- Gram-positives (S. sapro, Enterococcus, S. epi) via ascending route
- Gram-negatives (E. coli, Pseudomonas, Proteus, Kleb, Acinetobacter, Enterobacter) via ascending route - from catheterization (except E. coli)
- GPR’s (Bacillus, MAC, Listeria)
- Chlamydia, N. gonorrhoeae, Mycoplasma, Ureaplasma, Gardnerella, Adenovirus, HSV
- Bacteremias, endocarditis, , mycobacteria, Candida, fungal infections via hematogenous route
UTI virulence factors
- adherence
- biofilms
- calculi formation
- Gram positive cocci
- catalase positive, coagulase negative
- Bacitracin resistant, Novobiocin resistant
S. saprophyticus
- Gram positive cocci
- catalse -
- Bile esculin +, growth in 6.5% NaCl, PYR +
Enterococcus
- Gram positive cocci
- catalase +, coagulase -
- Bacitracin resistant, Novobiocin susceptible
S. epidermidis
- GNR
- oxidase -, glucose fermenter, nitrate reducer, motile
- IMVC (++–)
- H2S -, citrate -, PAD -, A/A
E. coli
- blue-green hue on MAC (pyoverdin and pyocyanin)
- beta hemolytic
- oxidase +, catalase +, ADH +, citrate +
- glucose oxidizer
- grows at 42C
P. aeruginosa
- GNR
- H2S +, swarm, PAD +, urease +
- vulgaris (indole +, ODC -, A/A)
- mirabilis (indole -, ODC +, K/A)
Proteus
- GNR
- citrate +, H2S -, PAD -, urease -, IMVC (–++)
- oxytoca (indole +)
Klebsiella
- GNR
- oxidase -, glucose oxidizer
- NLF, but purple on MAC
Acinetobacter
- GNR
- oxidase -, IMVC (–++), LDC + (except cloacae), ODC +
- citrate +, H2S -, PAD -, urease -
Enterobacter
- Gram positive bacilli
- grows at 4C, catalase +
- umbrella motility at 25C, tumbling motility
- CAMP positive (block)
Listeria
- Gram positive bacilli
- motile, beta hemolytic
- catalase positive
Bacillus (cereus)
- inactive in most tests
- heat-stable catalase
- common Mycobacteria in US
M. avium complex (MAC)
- intracellular parasites
- specimen on Dacron swab
- EB and RB stages of life cycle
- won’t grow on a normal plate
Chlamydia trachomatis
- Gram negative dipplococci
- oxidase -
- grows on MTM
- utilizes glucose
Neisseria gonorrhoeae
Lab Diagnosis of UTI
- colony count: leukocyte count at least 10/mm^3 in more than 96% of patients with bacteruria
- Urine culture and other tests for diagnosis
Types of urinary infections (women)
- Symptomatic pyuria without bacteruria
- Asymptomatic bacteruria (with or without pyuria)
Specimen collection
- Voided midstream specimen collection (CCMS)
- Catheterized specimen collection (best for kids)
- Suprapubic aspiration (for anaerobes)
- 24hr old specimen is unacceptable
- first morning urine is best
Specimen processing
- processed within 2 hours
- refrigerated if not processed immediately
- avoid contamination of specimen
- rapid nonculture screening or manual screening
Microscopy
- pyuria: 5-10 leukocytes in urine
- detect fungi and mycobacteria (use acid fast stain)
- chemical tests
Specimen rejection
Reject if inadequate collection/transportation
Culturing urine specimens
- usually BAP and MAC
- incubate 24 hours
- plate to more plates for fastidious organisms
Interpreting culture results
- colony count indicates level of pyuria
- presence of symptoms also indicative
Culture with 3 or more uropathogens
probably contamination
Culture with 2 significant uropathogens (>10^5)
identify and perform susceptibility
Culture with 1 or 2 uropathogens (small numbers >10^2)
identify if clinical situation warrants
Reportable results
- a pure culture of S. aureus is significant
- yeast in any culture is significant
- unusual organisms are reportable
- only report significant UTI antibiotics
