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2005 OMIG, Abstract 22

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Characterization of Mycobacterium Isolates from Ocular Infections

BA Schlech1, JG Bartell1, JJ Dajcs1, BA Mendoza1, DW Stroman1, S Sharma2, L Therese3, and HN Madhavan3

1Alcon Research, Ltd., Fort Worth, TX, 2LV Prasad Eye Institute, Hyderbad, India, and 3Research Vision Foundation, Chennai, India

Purpose: To characterize Mycobacterium isolates recovered from Indian patients with ocular infections.

Method: Mycobacterium isolates were recovered from ocular tissues from 14 infected eyes. Definitive species-level identification was performed by comparative analysis of the 16S rRNA gene and 16S-23S rDNA-internal transcribed spacer (ITS) region. The MICs for 24 selected antibiotics were determined by broth dilution.

Results: The 14 isolates were identified as M. fortuitum (n=6) and M. abscessus (n=8). The ITS sequences were needed to distinguish M abscessus from M chelonae. Fluoroquinolone susceptibilities (MICs) for these two organisms are as follows:

Fluoroquinolone M. fortuitum M. abscessus
Moxifloxacin 0.06-0.13 ug/ml 8-32 ug/ml
Gatifloxacin 0.06-0.25 ug/m 8-16 ug/ml
Ciprofloxacin 0.06-0.50ug/ml 2-32 ug/ml
Levofloxacin 0.13-0.50ug/ml 32-64 ug/ml

Conclusions: The M. fortuitum isolates were significantly more susceptible to the fluoroquinolones than the M. abscessus isolates. Although the susceptibility to gatifloxacin and moxifloxacin is similar for any particular Mycobacterium isolate, there is a 3-fold difference in penetration into the stroma of human corneas between the two fluoroquinolones (Cmax. of 48.5 ug/g for moxifloxacin versus 15.7 ug/g for gatifloxacin, personal communication from Terry Kim). Considering the antibiotic susceptibility of these strains and the corneal penetration characteristics, moxifloxacin appears to provide the best fluoroquinolone option for preventing and controlling Mycobacterium ocular infections.

Disclosure code: E

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