Question
A 25 year old female patient came to medical O.P with history of high grade fever with chills rigor. She also complaints of painful micturition. What is your provisional diagnosis Name four common bacteria causing this condition Describe in detail the sample collection transport and processing for the laboratory diagnosis of this condition Name four drugs used for treating this patient What are the predisposing factors for the above condition (1+2+4+2+1)
Answer
Provisional diagnosis: Urinary tract infection (acute pyelonephritis, given fever with chills/rigor plus dysuria, suggesting upper tract involvement).
Four common causative bacteria: Escherichia coli (the commonest, ~80% of cases, via uropathogenic strains with P-fimbriae), Klebsiella pneumoniae, Proteus mirabilis (associated with urinary stones due to urease production), and Enterococcus faecalis (also Staphylococcus saprophyticus in young sexually active women, and Pseudomonas aeruginosa in catheter-associated/nosocomial UTI).
Sample collection, transport, and processing
- Collection: a properly collected clean-catch midstream urine (MSU) sample, after cleaning the external genitalia, discarding the initial stream, and collecting the mid-stream portion into a sterile, wide-mouthed container; catheter specimen or suprapubic aspirate may be used where clean-catch collection is not feasible or in infants.
- Transport: sample should be transported to the laboratory and processed within 1–2 hours of collection; if delay is unavoidable, the sample should be refrigerated at 4°C (or a boric acid preservative used) to prevent bacterial multiplication in vitro, which would give a falsely elevated colony count on culture.
- Processing:
- Microscopy — centrifuged/uncentrifuged urine examined for pus cells (pyuria, >5–10/hpf) and bacteria.
- Culture — inoculated onto CLED (cystine-lactose-electrolyte-deficient) agar or MacConkey agar using a calibrated (standard) loop to deliver a known volume, allowing accurate colony counting; incubated aerobically at 37°C for 18–24 hours.
- Interpretation — significant bacteriuria (Kass’s criterion): ≥10⁵ CFU/mL of a single organism from a properly collected MSU sample.
- Identification and antibiotic sensitivity testing performed on significant isolates to guide treatment.
Four drugs used for treatment: nitrofurantoin, co-trimoxazole (trimethoprim-sulfamethoxazole), fluoroquinolones (e.g., ciprofloxacin), and third-generation cephalosporins (e.g., ceftriaxone, particularly for pyelonephritis/systemic infection) — final choice guided by local resistance patterns and culture/sensitivity report.
Predisposing factors: female sex (shorter urethra), sexual activity, urinary tract obstruction/stasis (stones, structural anomalies, benign prostatic hyperplasia), vesicoureteric reflux, catheterization/urinary instrumentation, pregnancy, diabetes mellitus, and immunosuppression.