A comparative analysis of expanded quantitative urine culture and standard urine culture methods in patients with urinary tract infections

Abstract

Urinary tract infections (UTI) are one of the most common bacterial infections of humans. Accurate diagnosis of the cause of UTI is necessary for effective treatment. Even though clinically Standard Urine Culture (SUC) is common for detecting bacterial presence in urine samples, latest reports show that Expanded Quantitative Urine Culture (EQUC) provides better diagnostic sensitivity compared to SUC. To test this, SUC and EQUC methods were compared to analyse bacterial load and diversity using urine samples collected from 20 patients with UTI symptoms and 20 healthy controls in this study. Samples were diluted and inoculated on nutrient agar, HiChrome UTI agar, MacConkey agar and blood agar for SUC method, then incubated at 37°C for 24 hours under aerobic conditions. On the other hand, for EQUC, in addition to all the media, chocolate agar was used with different conditions like carbon-enriched, anaerobic environment with incubation at 37°C for 48 hours. Colony characteristics and polymerase chain reaction (PCR) were performed for bacterial detection. Antibiotic susceptibility test was conducted by the Kirby-Baur method. On nutrient agar medium, EQUC yielded 5-fold higher bacteria than SUC and portrayed higher bacterial diversity. While several bacterial species for example, klebsiella spp., Staphylococcus aureus, and Pseudomonas aeruginosa was detected by SUC and EQUC based on colony characteristics, EQUC exclusively detected the presence of Staphylococcus haemolyticus. Seventy-five percent of presumptive Klebsiella and 73.3% of presumptive E. coli were confirmed by PCR. AST was performed on E. coli and Klebsiella. Notably, bacteria grown via EQUC showed a diverse resistance pattern compared to SUC. Further molecular diagnoses will be performed to validate these findings.