Significant bacteriuria among requested repeat urine samples and its clinical correlation

Urinary tract infections (UTI) are the most common bacterial infections in both outpatient and inpatient department received for routine bacterial culture and sensitivity. We looked for significant bacteriuria in requested repeat urine sample after primary urine culture yielded significant growth (>105 CFU/ml) of ≥3 types of colonies. Also studied, different isolates grown with their sensitivity pattern and contamination rates of urine samples from different departments.

In routine, primary urine cultures yielding ≥3 types of colonies on Cystine Lactose Electrolyte Deficient (C.L.E.D) were requested for repeat samples, collected with aseptic precautions after proper instructions. Data was analyzed for the Microbiological profile and its clinical correlation.

Among 617 received requested urine samples, 292 (47.3%) yielded significant bacteriuria. Clinical details were available for 252 cases out of which 100 (39.7%) showed asymptomatic bacteriuria, 87 (34.5%) complicated UTI and 65 (25.7%) uncomplicated UTI. Null hypothesis was rejected as 292 (47.3%) of the received repeat samples showed significant bacteriuria and 325 (53%) showed normal flora/no growth i.e. there is a 50% chance of getting either a positive culture or normal flora/no growth in repeat urine samples after the primary urine culture showed ≥3 types of colonies. It indicates the importance of requesting repeat urine samples for an accurate urine culture report. Male patients were significantly associated with significant bacteriuria and complicated UTI (p= 0.001). Escherichia coli (n=112, 28%) was the most common followed by Klebsiella species (n=66, 16.4%) and Enterococcus species (n=69, 17.2%). 183 (45.6%) isolates were Multi-Drug Resistant (MDR) Gram Negative Bacilli (GNBs), Escherichia coli (50.3%) being most common. Vancomycin Resistant Enterococcus (VRE) (n=8, 2.0%) was also isolated.

Our study justifies the rationale for asking a repeat urine samples which helps in providing an appropriate microbiological report with antibiotic sensitivity pattern, hence preventing unwanted reporting of commensals/contaminants facilitating evidence based therapy.