Screening for urinary tract infection-causing Klebsiella pneumoniae using CHROMagar

Introduction. Urinary tract infections (UTIs) are considered prevalent among humans. While Klebsiella pneumoniae and Escherichia coli are commonly isolated from patients with UTIs, K. pneumoniae is more frequently isolated from specimens isolated from hospital-acquired infections.

Aim. The current study aimed to characterise and evaluate pathogenic K. pneumoniae isolated from patients suspected with a UTI at King Abdulaziz University Hospital.

Methodology. Twenty-four urine samples obtained from patients, between 12 November 2018 and 11 January 2019, were included in the study, and the microbial content was analysed via urine culture and VITEK 2 analyses.

Results. Of the 24 urine specimens, 23 samples (95.8%) yielded significant microbial growth (> 105 CFU/mL K. pneumoniae), and one sample (4.2%) yielded non-pathogenic microbial growth (< 105 CFU/mL K. pneumoniae). Of the specimens with cell counts of >105 CFU/mL, 21 samples (87.5%) were pure cultures showing the growth of a single pathogen, and three samples (12.5%) were mixed cultures, showing the growth of two or more pathogens; 10 (41.7%) samples were extended-spectrum beta-lactamase (ESBL) producers. VITEK 2 analysis showed that the most effective antibiotic was piperacillin, with 87.5% of the strains isolated in this study showing sensitivity to it, followed by gentamicin (83.3%) and ciprofloxacin (79.2%). Antibiotic susceptibility studies identified resistance against ampicillin (45.83%), trimethoprim (41.67%), and amoxicillin (25%) in the study isolates. Differential chromogenic culture media CHROMagar ESBL and CHROMagar KPC (K. pneumoniae carbapenemase) were used for rapid screening of ESBL and KPC producers. Among the 24 K. pneumoniae isolates, six isolates (25%) formed metallic blue colonies on CHROMagar ESBL, five (20.3%) were inhibited, and nine (37.5%) showed weak pigmentation. Three isolates (12.5%) formed pink colonies on CHROMagar ESBL. Seventeen isolates (70.8%) were KPC-positive, four (16.7%) showed weak pigmentation, and three (12.5%) formed pink colonies on CHROMagar KPC. The results from CHROMagar cultures agreed with those of VITEK 2 analyses.

Conclusion. Various microbial detection methods have been used in medical microbiology laboratories to identify and screen for microbial resistance in clinical specimens. VITEK 2 and CHROMagar are amongst the commonly used methods. Here, we report a possible discrepancy between the detection techniques and that the data obtained by different methods need not be synergistic. However, the use of a chromogenic medium offers a quick and accurate method for detection, enumeration, and presumptive identification of urinary tract pathogens.