Comparison of Type of Species and Antibacterial Susceptibility Profile of Staphylococci Isolated From Normal Healthy Conjunctiva and Ocular Infections.

Purpose: To compare the prevalence of various staphylococcal species in ocular infections [OIs (n = 105)] and in normal healthy conjunctiva [NC (n = 51)]. Antibacterial susceptibility profile of the isolates and prevalence of mecA gene among the isolates were also compared.

Design: A prospective, comparative, experimental study.

Methods: Antibiotic susceptibility was determined against chloramphenicol, ciprofloxacin, gatifloxacin, moxifloxacin, ofloxacin, cefazolin, vancomycin and cefoxitin by disc diffusion technique as per Clinical and Laboratory Standards Institute guidelines. Methicillin resistance was confirmed by detection of mecA gene by polymerase chain reaction.

Results: The prevalence of Staphylococcus aureus was significantly higher (P < 0.0001) in OIs compared with NC (48.6%, 9.8%), whereas the prevalence of Staphylococcus epidermidis was higher (P = 0.02) in NC (22.9%, 41.2%). Overall methicillin resistance was higher in S. epidermidis (66.7% each in OIs and NC) compared with S. aureus (OIs: 7.8%; NC: 0%), which was statistically significant (P < 0.0001). Methicillin resistance was also high among other coagulase-negative staphylococci in both groups [OIs: 40% (12/30); NC: 28% (7/25)]. Vancomycin was effective against all the isolates from both groups. Cefazolin was equally effective.

Conclusions: This study found S. aureus to be a major pathogen in OIs, although it is not common conjunctival flora. The data caution that prevalence of methicillin resistance in coagulase-negative staphylococci is more than S. aureus in OIs and must be considered in their treatment. Despite methicillin resistance, staphylococci from OIs and NC remain sensitive to vancomycin and cefazolin.