Utility of InTray COLOREX Screen agar and InTray COLOREX ESBL agar for urine culture in the Lao PDR

Background There is a need for simple microbiology diagnostics to enable antimicrobial resistance surveillance in low- and middle-income countries. Objectives To investigate the field utility of InTray COLOREX plates for urine culture and ESBL detection. Methods Clinical urine samples from Mahosot Hospital, Vientiane, Lao PDR were inoculated onto chromogenic media and InTray COLOREX Screen plates between June and August 2020. Urine and isolates from other clinical specimens were inoculated onto COLOREX ESBL plates. A simulated field study investigating the field utility of the InTray COLOREX plates was also completed. Results In total, 355 urine samples were inoculated onto standard chromogenic agar and InTray COLOREX Screen plates, and 154 urine samples and 54 isolates from other clinical specimens on the COLOREX ESBL plates. Growth was similar for the two methods (COLOREX Screen 41%, standard method 38%) with 20% discordant results, mainly due to differences in colony counts or colonial appearance. Contamination occurred in 13% of samples, with the COLOREX Screen plates showing increased contamination rates, potentially due to condensation. ESBL producers were confirmed from 80% of isolates from the COLOREX ESBL plates, and direct plating provided rapid detection of presumptive ESBL producers. Burkholderia pseudomallei also grew well on the ESBL plates, a relevant finding in this melioidosis-endemic area. Conclusions The InTray COLOREX Screen and ESBL plates were simple to use and interpret, permitting rapid detection of uropathogens and ESBLs, and have the potential for easy transport and storage from field sites and use in laboratories with low capacity.