Experience with the use of an automated system for diagnosis of urinar y tract infections

Abstract

Objective. To compare results of microbiological examination obtained on rapid automated system with semiquantitative plate culture to assess possibility and necessity of using the system in urine examination. Materials and Methods. The study included 231 urine samples collected from February to July 2023 from patients at Lomonosov Moscow State University Medical Research and Educational Center. The samples were cultured according to the standards of urine microbiological examination using chromogenic media and using an automatic HB&L system (Alifax, Italy) for 4 h. 30 min. to detect bacteriuria of 102 CFU/ ml or more and residual antimicrobial activity. When microbial growth was detected in the analyzer, extraction of microorganisms was performed on the same day for accelerated identification. Identification was performed by MALDI-TOF mass spectrometry. Results. According to the plate culture method, 160 positive samples were obtained. A total of 273 isolates were isolated, the predominant microorganisms were E. faecalis (22.3%) and E. coli (19.8%), a significant part was composed of atypical pathogens for UTI and normobiota (33.7%). According to the rapid automated system, only in 100 samples the growth of microorganisms was detected, in 4 cases the positive result obtained by the automatic system was not confirmed by growth on chromogenic media. Thus, 64 of the 160 positive cultures were not detected using the automated system, and 14 of those ones was E. coli. Residual antimicrobial activity was detected in 104 samples, including 43 of 64 false-negative culture results using the automated system. Rapid identification was performed on 57 samples, a microbial identification result was obtained in 49 of them. Complete or partial match between the results of rapid identification and classical methods was obtained for 48 samples. In all cases, when rapid identification was performed for a sample with monoculture, the results of two methods were identical. Conclusions. An overall sensitivity and specificity of the culture method using an automatic system were 60% and 94.4%, respectively. Sensitivity for samples containing E. coli was 74.1%, and for their isolation in monoculture – 87.5%.

Keywords

• urinary tract infections
• diagnosis
• culture
• automated system