Study on Prevalence, Antibiotic Susceptibility, and tuf Gene Sequence-Based Genotyping of Species-Level of Coagulase-Negative Staphylococcus Isolated From Keratitis Caused by Using Soft Contact Lenses

Abstract

Objective: To study on antibiotic susceptibility and identify coagulase-negative Staphylococcus (CoNS) species based on tuf gene sequencing from keratitis followed by using soft contact lenses in Isfahan, Iran, 2013. Methods: This study examined 77 keratitis cases. The samples were cultured and the isolation of CoNS was done by phenotypic tests, and in vitro sensitivity testing was done by Kirby-Bauer disk diffusion susceptibility method. Results: Thirty-eight of isolates were conveniently identified as CoNS. In this study, 27 (71.1), 21 (55.3), and 16 (42.1) were resistant to penicillin, erythromycin, and tetracycline, respectively. One hundred percent of isolates were sensitive to gentamicin, and 36 (94.7) and 33 (86.8) of isolates were sensitive to chloramphenicol and ciprofloxacin, respectively. Also, resistances to cefoxitin were 7 (18.4). Analysis of tuf gene proved to be discriminative and sensitive in which all the isolates were identified with 99.0 similarity to reference strains, and Staphylococcus epidermidis had the highest prevalence among other species. Conclusions: Results of this study showed that CoNS are the most common agents causing contact lens-associated microbial keratitis, and the tuf gene sequencing analysis is a reliable method for distinguishing CoNS species. Also gentamycin, chloramphenicol, and ciprofloxacin are more effective than the other antibacterial agents against these types of bacteria.