Surveillance of the Activity of Aminoglycosides and Fluoroquinolones Against Ophthalmic Pathogens from Europe in 2010-2011

Purpose/aim: Bacterial infections of the ocular surface are commonly treated empirically with broad spectrum antibiotics. Due to concerns over increasing antibiotic resistance, we evaluated current susceptibility patterns of the ocular bacterial pathogens in Europe.

Materials and methods: Non-consecutive ocular isolates of Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Streptococcus pneumoniae, Haemophilus influenzae, and Pseudomonas aeruginosa were collected in 2011 from centers in France, Germany, Italy, Poland, Slovak Republic, Spain, and the United Kingdom. Centers were asked to provide similar numbers of methicillin-susceptible and -resistant staphylococcal isolates. Minimum inhibitory concentrations were determined for fluoroquinolones (besifloxacin, ciprofloxacin, moxifloxacin), aminoglycosides (tobramycin, gentamicin, netilmicin), oxacillin, chloramphenicol and erythromycin. Isolates were categorized as susceptible, intermediate, or resistant according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria.

Results: A total of 741 ocular isolates were obtained. Antibiotic resistance rates depended not only on the antibiotic and species, but also varied greatly by the country of origin. Resistance to ciprofloxacin, tobramycin, erythromycin, and to a lesser extent, chloramphenicol, was a concern for all staphylococci. Multidrug resistance was common among methicillin-resistant S. aureus (MRSA) and MRCoNS and isolates of S. pneumoniae, H. influenzae, and P. aeruginosa were frequently non-susceptible to erythromycin, beta-lactams, and ciprofloxacin/tobramycin, respectively. Resistance rates showed substantial differences among the seven countries tested. Fluoroquinolones and aminoglycosides showed differences in antibacterial potency and resilience toward the antibiotic resistance mechanisms.

Conclusions: Methicillin-resistant staphylococcal isolates were frequently non-susceptible to a multitude of other antibiotics, making MRSA and MRCoNS a potentially significant concern. The broad range of resistance rates observed across Europe in this study confirms the importance of considering current local resistance patterns when antibacterial agents are chosen for empiric management of ocular infections.