Biomedical and Biotechnology Research Journal (Jan 2019)
Validation and impact of the use of automated urine culture streak system in a diagnostic laboratory on surveillance of catheter-associated urinary tract infections at a tertiary care setting
Abstract
Background: Quantitative urine culture reporting on plates inoculated by automated streaking system (PREVI® Isola) demonstrates maximum growth only equivalent up to 104 colony-forming unit (CFU)\ml, according to the manufacturer's recommendation. Therefore, there is a probability of erroneous catheter-associated urinary tract infection (CAUTI) surveillance data as a count of ≥105 CFU/ml is required according to CAUTI definition. This study aimed to validate automated urine culture streak system for improving the surveillance of hospital-acquired CAUTIs. Materials and Methods: This was a prospective, cross-sectional study. In 1-month duration, urine samples of 1000 consecutive patients reported to the microbiology section for culture and sensitivity were included. Samples were processed simultaneously manually (1 μl loop) and with an automated streaking system. Plates streaked by automated method were arbitrarily divided into eight equally sized segments. After 24 h of incubation at similar conditions, microbial growths in each segment were noted and correlated with its manual colony count. To minimize the error, colony count and morphotype were analyzed by a senior technologist and counterchecked by a consultant. Results were recorded on an Excel sheet. Results: Growth on the 7th and 8th segments corresponded with ≥105 CFU/ml. Growth up to the 4th, 5th, and 6th segments corresponded with 104 CFU/ml, whereas the 3rd segment with >103 but <104 CFU/ml. Any growth in the 1st and 2nd sectors was considered insignificant. Conclusion: Quantitative urine culture analysis inoculated by automated streak system corresponds to the CAUTI surveillance definition. Colony count requires validation with manual method before implementing in laboratory.
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