Rapidly growing mycobacteria (RGM) have emerged as important human pathogens that can cause a variety of diseases. Thirty isolates of the pathogenic RGM were recovered from patients who attended King Chulalongkorn Memorial Hospital during 1997 and 2003. There were 16 isolates of Mycobacterium chelonae, ten isolates of M. fortuitum and four isolates of M. abscessus. Clinical data was available in only nine
patients (five males and four females) including six M. chelonae, two M. abscessus, and one M. fortuitum. The mean age was 37 years (range: 13-62 years). The associated conditions were present in five patients including two diabetes, one HIV infection, one pregnancy, one SLE and one chronic renal failure. A wide spectrum of clinical features was observed. These included two chronic pulmonary infections, two posttraumatic wound infections, two disseminated infections, one lymphadenitis, one keratitis and respiratory colonization. AFB staining was positive in six patients (66.67%). The MIC of one M. chelonae and one M. abscessus were determined by Epsilon test. For M. chelonae, the MIC of clarithromycin, amikacin, ciprofloxacin, sulfamethoxazole and imipenem were 0.25, 2.0, 1.00, > 64, and 0.54 μg/ml, respectively. For M. abscessus, the MIC of clarithromycin, amikacin, ciprofloxacin, tetracycline and sulfamethoxazole were 0.016, 0.016, 0.038, > 16 and 0.002 μg/ml, respectively. Six of eight patients (75%) were initially treated with four first-line antituberculous drugs (isoniazid, rifampicin, pyrazinamide and ethambutol) before obtaining the culture result. Of these, three patients with pulmonary and disseminated infections improved after a prolonged course of these combinations. The patients improved after switching to specific anti-RGM antibiotics. One patient died after 10 months of therapy of four anti-tuberculous drugs. One patient with post-traumatic wound infection was cured with surgical debridement and dicloxacillin. One patient improved after treatment as acute bronchitis with oral amoxicillin. An extensive review of the literature of RGM infections in Thailand is also presented.

Keywords: Rapidly growing mycobacteria, Nontuberculous mycobacteria, Mycobacterium fortuitum, M. chelonae/abscessus, M. smegmatis