Evaluation of genotypic and antimicrobial resistance characterization of Coagulase-Negative Staphylococci isolated from patients and commensal isolated from healthcare workers in teaching hospitals in Tabriz and Shahroud

Abstract

Coagulase-Negative Staphylococci (CoNS) are among important nosocomial pathogens. Biofilm is the main virulence factor in these bacteria. The aim of this study was to evaluate antibiotic resistance patterns and biofilm formation in CoNS isolates from hospitalized patients (as clinical isolates) and healthcare workers (as colonizing isolates) and to determine the pulsotypes of two species of Methicillin Resistant Staphylococcus epidermidis (MRSE) and Methicillin Resistant Staphylococcus haemolyticus (MRSH) in Tabriz and Shahroud hospitals. Methods: A total of 150 CoNS isolates (including 100 clinical isolates and 50 colonizing isolates) collected in Tabriz and Shahroud during 2016-2017 were studied. Bacterial identification was performed using standard biochemical methods and antibiotic susceptibility patterns was determined by disk diffusion assay. Biofilm formation was performed by phenotypic methods and related icaA, icaD, aap and IS256 genes by PCR. The pulsotypes of MRSE and MRSH was determined by PFGE method. Results: Overall, all isolates were resistant to more than 50% of the tested antibiotics except to linezolid and vancomycin. The highest frequency of resistance was observed to penicillin (92%), cefoxitin (84%) and cotrimoxazole (89%) and the lowest frequency was observed to rifampin (27%). Despite the high frequency of antimicrobial resistance in clinical isolates compared to colonizing isolates, the relationship was not significant. The frequency of biofilm formation by Congo red agar method in clinical and colonizing isolates was 89% and 76%, respectively. The frequencies of icaA, icaD, aap and IS256 genes in clinical isolates were 48%, 47, 62% and 52%, respectively, and for colonizing isolates were 58%, 58%, 62% and 22%, respectively. There was a significant relationship in IS256 gene only. Furthermore, in molecular typing of 51 MRSE by PFGE method, 27 different PFGE types including 14 related PFGE types (A-N) and 13 unrelated types were identified. Clinical and colonizing isolates were clustered in 9 and 4 pulsotypes, respectively, and 2 palsotypes were shared between groups. Also, in 12 MRSH isolates, 8 pulsotypes were identified (5 were singletons), of which pulsotype C was the dominant type and was common in both groups.