Asymptomatic Pregnant lady with urine culture positive for E coli but negative nitrate.

Explanation

Core Concept: Asymptomatic bacteriuria in pregnancy. Physiological changes in pregnancy (ureteral dilation, urinary stasis) significantly increase the risk of asymptomatic bacteriuria progressing to acute pyelonephritis.

Clinical Presentation:

• No symptoms of UTI (no dysuria, frequency, or fever), but a positive urine culture (≥ 10^5 CFU/mL of a single uropathogen, commonly E. coli).
• Note: A negative nitrite test does not rule out infection, as it depends on sufficient bladder incubation time and the presence of nitrate-reducing bacteria.
• Complications: Pyelonephritis, preterm birth, low birth weight.

Diagnosis:

• Gold standard: Midstream clean-catch urine culture.

Management:

• Acute/Definitive: Unlike in non-pregnant adults, asymptomatic bacteriuria in pregnancy MUST be treated with a course of safe pregnancy-compatible antibiotics (e.g., cephalexin, amoxicillin-clavulanate, or fosfomycin) to eradicate the bacteria and prevent pyelonephritis. A test-of-cure culture is usually performed afterward.