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M. Feilmeier, E. Alfonso, D. Miller, R. Oechsler; In vitro Antimicrobial Susceptibility Patterns and Source Distribution of Rapidly Growing Mycobacteria (RGM) From Ocular Infections in South Florida. Invest. Ophthalmol. Vis. Sci. 2008;49(13):511.
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© ARVO (1962-2015); The Authors (2016-present)
To update the antimicrobial susceptibility patterns and source distribution of RGM isolated from ocular infections in south Florida (1980-2007) and determine the susceptibility of these organisms to tigecycline, daptomycin, and moxifloxacin.
Laboratory records of ocular cultures positive for growth of RGM between 1980 and 2007 were reviewed to determine the source distribution and relative frequency of infection for each organism. Historical antimicrobial susceptibility patterns were determined through review of the broth micro dilution testing profiles. In addition, E tests and Mueller Hinton agar supplemented with 5% sheep's blood agar were used to evaluate in vitro susceptibility of 33 ocular isolates (2005-2007) against tigecycline, daptomycin, and moxifloxacin.
186 ocular cultures from 170 patients were positive for RGM from 1980-2007. Of the 186 isolates, 84% were M. Chelonae/abscessus, 12% were M. fortuitum, and 5% were other species. The most common sources were cornea (56/186), conjunctiva (36/186), lacrimal sac (19/186), scleral buckle (15/186), anophthalmic socket (13/186), and vitreous (11/186). Analysis of all specimen susceptibility data demonstrated susceptibility rates of 95% to cefazolin, 94% to clarithromycin, and 59% to linezolid. Among the flouroquinolones, susceptibility rates were 39% for gatifloxacin, 33% for moxifloxacin, 25% for levofloxacin, 15% for ciprofloxacin, and 14% for ofloxacin. M chelonae/abscessus showed susceptibility of 2% to ciprofloxacin, 6% to levofloxacin, 19% to gatifloxacin, 14% to moxifloxacin and M. fortuitum showed susceptibility of 76% to ciprocloxacin, and 100% to levofloxacin, gatifloxacin, and moxifloxacin. Etest susceptibility of 33 ocular isolates (2005-2007) yielded in vitro susceptibility rates of 22%, and 0% for moxifloxacin, and daptomycin, respectively. For tigecycline, the MIC 90% was 16ug/ml and MIC 50% was 3ug/ml.
Cefazolin and clarithromycin are associated with the highest in vitro susceptibility among RGM. In vitro susceptibility rates for RGM are higher for the 3rd and 4th generation flouroquinolones compared to ciprofloxacin and ofloxacin. M. chelonae/abscessus species showed significantly lower in vitro susceptibility rates to the flouroquinolones when compared to M. fortuitum isolates. Daptomycin does not appear to be effective in vitro against mycobacteria. Tigecycline, however, is an effective antibiotic in vitro and may be clinically useful against ocular RGM infections.
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