Screening for sterilizing activity of antibiotic combinations in an acid model of rapidly growing mycobacteria during the stationary phase of growth.

BACKGROUND

In view of the problems of correlation between the data provided by classical microbiological studies and clinical response, we designed an in vitro method to screen for the sterilizing activity of various antibiotics, individually or in combinations, against clinical isolates of various rapidly growing mycobacteria in the stationary phase.

MATERIAL AND METHODS

We screened a large number of antibiotic combinations (4-16 microg/ml) for their sterilizing capacity in 26 Mycobacterium fortuitum clinical isolates, 7 Mycobacterium chelonae and 2 Mycobacterium abscessus clinical isolates (10(5) CFU).

RESULTS

The best results against M. fortuitum were obtained with moxifloxacin, both on its own (13/26 strains) and in combination. This drug is also very active against M. chelonae (3/7 strains), and in combination with clarithromycin and amikacin exhibits sterilizing activity against all the strains studied. Combinations of clarithromycin with moxifloxacin or linezolid at high doses (16 microg/ml) exhibit activity against M. abscessus.

CONCLUSIONS

The most relevant finding of our study is the good activity of moxifloxacin against these microorganisms in the stationary phase. This indicates the need to confirm these data in animal models or clinical trials in order to determine their true clinical importance.