Abstract
Purpose::
The purpose of this study is to describe the current susceptibility - resistance profile of the major bacterial species in superficial ocular infections collected during clinical studies in the United States.
Methods::
Bacteria were identified to the species level by a combination of phenotypic and DNA-based methods. Susceptibility testing was performed with standard microdilution broth methods to obtain end-point minimal inhibitory concentration (MIC) data for >20 antibiotics. The data is presented as the percentage of isolates of a particular species that were resistant in vitro to specified breakpoints for acquired resistance.
Results::
The five most frequently recovered species in conjunctivitis were: 1) Haemophilus influenzae, 2) Staphylococcus epidermidis, 3) Propionibacterium acnes, 4) Streptococcus pneumoniae, and 5) Staphylococcus aureus. In H. influenzae, the two most common resistance phenotypes were ampicillin - 36% and trimethoprim - 20%. In S. epidermidis, the 3 most common resistance phenotypes were: sulfamethoxazole - 95%, macrolides - 52%, and oxacillin - 45%. In P. acnes, the two most common resistance phenotypes were: trimethoprim - 43% and macrolides - 10%. In S. pneumoniae, the three most common resistance phenotypes were: macrolides - 19%, sulfamethoxazole - 19%, and trimethoprim - 17%. In S. aureus, the two most common resistance phenotypes were: sulfamethoxazole - 67% and macrolides - 29%.In blepharitis, the three most frequently recovered species were 1) S. epidermidis and 2) P. acnes, and 3) S. aureus. In S. epidermidis, the 3 most common resistance phenotypes were: sulfamethoxazole - 81%, macrolides - 61%, and oxacillin - 41%. In P. acnes, the two most common resistance phenotypes were: trimethoprim - 17% and macrolides - 10%. In S. aureus, the two most common resistance phenotypes were: sulfamethoxazole - 74% and macrolides - 33%.
Conclusions::
Although the most frequent pathogens in the eye have not changed over the past several decades, the percentage of resistant isolates (within specific species) differs significantly. The extremely high rate of in vitro resistance to certain older antibiotics raises questions about the appropriateness of therapies based upon these agents.
Keywords: bacterial disease • antibiotics/antifungals/antiparasitics • conjunctivitis