Clinical significance and antibiotic susceptibilities of nontuberculous mycobacteria from patients in Crete, Greece.

AIM

To describe the clinical significance and antibiotic susceptibilities of nontuberculous mycobacteria (NTM) isolated from patients in Crete, Greece between January 2000 and December 2009.

PATIENTS & METHODS: NTM identification was performed using conventional bacteriological methods and confirmed by molecular characterization with commercially available assays. Rare and novel species were identified by sequencing of the 16SrRNA and of the hsp65 genes. Antibiotic susceptibility testing was performed by E-test. Rapidly growing (RGM) and slowly growing (SGM) NTM were tested against 14 antimicrobials, including nine common ones, except for Mycobacterium avium and Mycobacterium intracellulare (MAC) complex isolates that were tested only against azithromycin, clarithromycin, linezolid and moxifloxacin.

RESULTS

During the study period, 290 positive samples for NTM were recovered from 207 patients. Among the positive samples, 150 were identified as SGM and 57 as RGM. Overall, 50 patients met American Thoracic Society criteria for disease due to NTM, 42 by SGM and eight by RGM. Risk factors in patients with NTM disease were underlying lung diseases, mainly chronic obstructive pulmonary disease and asthma, smoking, rheumatoid arthritis, AIDS, alcohol or drug abuse, malignancies and bronchiectasis. The most common disease-causing species were the MAC complex (n = 25) followed by Mycobacterium kansasii (n = 10). Amikacin was the most active drug for RGM with 100% susceptibility. Macrolides were very active against isolates of the MAC complex, while tigecycline had excellent activity in vitro against RGM. M. kansasii was the most susceptible NTM species in vitro.

CONCLUSION

Our study is the first to describe the clinical significance, risk factors and susceptibility patterns of NTM isolates in a Greek population.