Abscessus Clinical Isolates Research Articles

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 μg/ml) for their sterilizing capacity in 26 Mycobacterium fortuitum clinical isolates, 7 Mycobacterium chelonae and 2 Mycobacterium abscessus clinical isolates (10⁵ 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 μg/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.

Detection of Clarithromycin-resistant Strains from Clinical Isolates of Mycobacterium abscessus

Background: Mycobacterium abscessus is the most pathogenic and drug-resistant rapid-growing mycobacterium. Clarithromycin or azithromycin are the only regular oral antimycobacterial agents that have an effect on M. abscessus . We tried to detect the clarithromycin-resistant strains from the clinical isolates of M. abscessus. Methods: We tried to isolate the clarithromycin-resistant strains from 220 clinical isolates of M. abscessus by performing using reverse hybridization assay (RHA) and the broth microdilution test (BMT). Results: Seven resistant strains (3.2%) from all the tested clinical isolates were detected by BMT. Three of these resistant strains were also detected by RHA and it was confirmed that they had point mutants. Conclusion: These results showed that clarithromycin resistance in M. abscessus clinical isolates is related to a point mutation and other unknown mechanisms. (Tuberc Respir Dis 2008;64:422-426)