Question
A 42-year-old female presented to the OPD with complaints of urinary frequency and urgency and pain in the lower abdomen. One month back she was treated for the same complaint. The Urine culture showed significant growth of lactose fermenting colonies which were Gram negative bacilli.
- (a) What is most probable clinical diagnosis. 1 mark(s)
- (b) What are the various methods of collection of urine for culture. 3 mark(s)
- (c) Name the causative agents of this condition. 2 mark(s)
- (d) What is significant bacteriuria. e) Describe the laboratory diagnosis of this condition. f) Write four antibiotics used to treat the condition. g) Write the measures used to prevent the infection in catheterized patients 2 mark(s)
Answer
(a) Most probable clinical diagnosis: Recurrent urinary tract infection (UTI) — urinary frequency/urgency and lower abdominal pain, with a prior similar episode one month back, and urine culture showing significant growth of lactose-fermenting Gram-negative bacilli (consistent with E. coli).
(b) Methods of collection of urine for culture: Clean-catch midstream urine (the standard method, after appropriate perineal cleaning); catheter specimen of urine (aseptically aspirated from the catheter port); and suprapubic aspiration (the most reliable method for avoiding contamination, via direct percutaneous bladder puncture, particularly used in infants or when a clean sample cannot otherwise be obtained).
(c) Causative agents: Escherichia coli (the most common cause), Klebsiella pneumoniae, Proteus mirabilis, Enterococcus faecalis, and Staphylococcus saprophyticus.
(d) Significant bacteriuria: the presence of ≥10⁵ colony-forming units (CFU)/mL of a single (predominant) bacterial species in a properly collected, midstream urine sample — the threshold (per Kass’ criteria) considered indicative of true urinary tract infection rather than contamination; lower thresholds (e.g., ≥10² CFU/mL) apply for suprapubic aspirate or in symptomatic patients with a single pure isolate.
(e) Laboratory diagnosis:
- Urine microscopy — significant pyuria (pus cells) and bacteriuria.
- Urine culture — quantitative culture on CLED/MacConkey agar, assessing colony count and organism identification; lactose-fermenting pink colonies on MacConkey agar are consistent with E. coli.
- Antibiotic susceptibility testing on significant isolates.
- Dipstick screening (leukocyte esterase, nitrite) — supportive, rapid screening tools.
(f) Four antibiotics used to treat UTI: Nitrofurantoin, Cotrimoxazole (Trimethoprim-Sulfamethoxazole), Ciprofloxacin, and Cephalexin — final selection guided by local resistance patterns and culture/susceptibility results.
(g) Measures to prevent infection in catheterized patients:
- Minimize catheter use — insert only when clinically indicated, and remove as soon as possible.
- Aseptic technique during catheter insertion.
- Maintain a closed, sterile drainage system, avoiding unnecessary disconnection.
- Regular perineal hygiene and proper catheter care.
- Avoid unnecessary catheter irrigation/manipulation.
- Use of antimicrobial/silver-coated catheters in select high-risk situations, and daily review of the continued necessity of catheterization, as part of a formal catheter-care bundle.