Question
A 25 year old pregnant lady attended the out patient department with complaints of fever and pain on micturition . Urine microscopy revealed plenty of pus cells and bacteria.
- (a) List the bacterial agents causing urinary tract infections. 1 mark(s)
- (b) Write a note on asymptomatic bacteriuria and its significance. 3 mark(s)
- (c) What are the methods of sample collection in a suspected case of urinary tract infection. 1 mark(s)
- (d) Describe the laboratory diagnosis of urinary tract infection. e) Name two antibiotics which can be prescribed for this patient 2 mark(s)
Answer
(a) Bacterial agents causing urinary tract infections: Escherichia coli (the single most common cause, accounting for the majority of both community-acquired and uncomplicated UTIs), along with Klebsiella pneumoniae, Proteus mirabilis, Enterococcus faecalis, and Staphylococcus saprophyticus (particularly in young sexually active women).
(b) Asymptomatic bacteriuria and its significance: Asymptomatic bacteriuria is defined as the presence of a significant number of bacteria (≥10⁵ CFU/mL) in a properly collected urine sample from a patient without any symptoms of urinary tract infection. It is common, particularly in elderly individuals, catheterized patients, and pregnant women. Significance: in most populations it does not require treatment, as treatment does not reduce complications and unnecessarily promotes antimicrobial resistance. However, in pregnancy (as in this patient), asymptomatic bacteriuria is a significant exception — it must be actively screened for and treated, since untreated asymptomatic bacteriuria in pregnant women carries a substantially increased risk of progression to symptomatic UTI/acute pyelonephritis, which is in turn associated with preterm labour and low birth weight. Other groups where treatment is indicated include patients about to undergo urological procedures with risk of mucosal bleeding.
(c) Methods of sample collection in suspected UTI: Clean-catch midstream urine sample (the standard, non-invasive method, after appropriate perineal cleaning to reduce contamination) and, where indicated (e.g., inability to void, need to avoid contamination), catheter specimen of urine or suprapubic aspiration (the most reliable method for avoiding contamination, particularly used in infants).
(d) Laboratory diagnosis of UTI:
- Urine microscopy — presence of pus cells (>10/high power field) and bacteria supports the diagnosis, as seen in this patient.
- Urine culture — the definitive/gold-standard test; a colony count of ≥10⁵ CFU/mL of a single organism from a properly collected midstream sample is considered significant bacteriuria (lower thresholds apply for suprapubic aspirate or symptomatic patients with pure growth).
- Antibiotic susceptibility testing — performed on the isolated organism to guide targeted antibiotic therapy.
- Dipstick tests (leukocyte esterase, nitrite) — rapid screening tools, though less sensitive/specific than culture.
(e) Two antibiotics for this patient: given that this patient is pregnant, appropriate, pregnancy-safe antibiotic choices include Nitrofurantoin (avoided near term) and Cephalexin (a first-generation cephalosporin) — both considered safe options for UTI in pregnancy, in contrast to fluoroquinolones and tetracyclines, which are contraindicated in pregnancy.