26 Aug Bacteria Causing Eye Infections Increasingly Resistant To Common Antibiotics
MedicalResearch.com Interview with
Ronald C Gentile, MD, FACS, FASRS
Professor of Ophthalmology
Chief, Ocular Trauma Service (Posterior Segment)
The New York Eye and Ear Infirmary of Mount Sinai
New York, NY 10003
Medical Research: What are the main findings of the study?
Dr. Gentile: We had three main findings in our study on the microbiological spectrum and antibiotic sensitivity in endophthalmitis over the past twenty- five years at the New York Eye and Ear Infirmary of Mount Sinai.
First Finding: The first main finding of the study was that there has not been any major change in the types of organisms causing endophthalmitis over the past 25 years. The most common cause of endophthalmitis in the study was bacteria, 95%, with most, 85%, being Gram-positive bacteria. The most prevalent organisms isolated were coagulase-negative staphylococcus, making up about 40% of the cases. This was followed by Streptococcus viridans species in about 12% and Staphylococcus aureus in about 11%. Gram-negative organisms accounted for about 10% and fungi for about 5%.
Second Finding: The second main finding of the study was that the current empiric intravitreal antibiotics used for treating endophthalmitis, vancomycin and ceftazidime, continue to be an excellent choice. The overwhelming majority of microorganisms causing endophthalmitis are susceptible to this combination. Over 99% of the Gram-positive isolates were susceptible to the vancomycin and about 92 percent of the Gram-negative isolates were susceptible to ceftazidime.
Third Finding: The third main finding of the study was that there was increasing microbial resistance to eight antibiotics including cefazolin, cefotetan, cephalothin, clindamycin, erythromycin, methicillin/oxacillin, ampicillin, ceftriaxone and decreasing microbial resistance to three antibiotics including gentamicin, tobramycin, and imipenem. For example, Staph Aureus isolates resistant to methicillin increased from 18% in the late 1980s to just over 50% this past decade while gentamicin-resistance endophthalmitis isolates decreased during the same time period from 42% to 6%.
Medical Research: Were any of the findings unexpected?
Dr. Gentile: One of the unexpected findings of the study was the significant trend towards decreasing microbial resistance against three antibiotics, including two aminoglycosides. This was especially interesting since prior to our study, increasing resistance to aminoglycoside antibiotics was seen in the 1980s. For example as mentioned above, gentamicin-resistance endophthalmitis isolates in our study decreased from 42% to 6% whereas an increase from 0 to 35% was seen from the 1970’s to the 1980’s. This finding was most likely caused by the selective pressure placed upon the bacteria from the decreased use of aminoglycoside antibiotics during the increased use of other antibiotics.
Medical Research: What should clinicians and patients take away from your report?
Dr. Gentile: The take home message of our report is that even though our current choice of empiric antibiotics (vancomycin and ceftazidime) for the organisms causing the most serious type of eye infections are supported by our study, these bacteria are becoming more resistant to commonly used antibiotics. The concept that antibiotic resistance is a natural process in which bacteria evolve, the opposite is also true since antibiotic susceptibility can increase with antibiotic restriction. As the CDC has also recommended, doctors and patients can play a role on trying to decease antibiotic resistance by using antibiotics judiciously.
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Gentile: It is recommended that since regional variability in sensitivities of infectious agents to particular antibiotics exists, we should all continue to perform periodic reviews of our local sensitivities on a regular basis to better enable us to treat infections with the most appropriate antibiotics. Even though new antibiotics will always be needed to keep up with resistant bacteria, the concept of planned antibiotic restriction or cycling of antibiotics may be one option for future study in combating microbial resistance.
Ronald C. Gentile, Salil Shukla, Mahendra Shah, David C. Ritterband, Michael Engelbert, Andrew Davis, Dan-Ning Hu
DOI: http://dx.doi.org/10.1016/j.ophtha.2014.02.001 p1634–1642
Published online: April 3, 2014