Antimicrobial susceptibility of Gram-positive cocci isolated from patients with conjunctivitis and keratitis in Crete, Greece

Abstract

To assess the in vitro susceptibility of Streptococcus pneumoniae, Staphylococcus aureus and coagulase-negative staphylococci (CoNS) ocular isolates to antibiotics, and identify changing trends in resistance over a 10-year period. All isolates from ocular infections collected between 2000 and 2009 were prospectively tested against several antibiotics in vitro. S. pneumoniae isolates (n = 93) were tested against 20 and S. aureus (n = 120) and CoNS (n = 214) against 19 antibiotics. To identify changes in susceptibility patterns, we compared results from 2000-2004 with those from 2005-2009. We also compared the antibiotic susceptibilities against aminoglycosides and quinolones between methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) isolates. All S. pneumoniae isolates were susceptible to quinolones, and 99% were susceptible to chloramphenicol. Regarding S. aureus, we noted a significant increase in resistance against penicillin in recent years (p = 0.016). Over 90% of S. aureus isolates were susceptible to quinolones and aminoglycosides. MRSA isolates were more resistant to ciprofloxacin and ofloxacin than MSSA isolates were (p = 0.016). Concerning CoNS, a significant increase in susceptibility to amikacin was noted in the second study period (p = 0.01). Quinolones remain an excellent treatment option for bacterial conjunctivitis and keratitis due to Gram-positive cocci in our region.