Background Mycobacterium abscessus (M.abscessus) can cause a variety of human infections,involving the lung,skin and soft tissues,and is generally believed to be acquired from environmental sources.The aim of this study was to investigate the molecular diversity and antibiotic susceptibility of M.abscessus isolates as the basis for strategies to improve control and management of infection.Methods Seventy M.abscessus isolates from patients attending the Guangzhou Thoracic Hospital were identified from 2003 to 2005 by biochemical tests,gas chromatography,polymerase chain reaction (PCR)-restriction analysis (PRA) of heat shock protein gene hsp65,and sequencing of the quinolone resistance determining regions (QRDRs) of gyrA.Susceptibilities to six antibiotics were determined by micro-broth dilution.Isolates were genotyped using randomly amplified polymorphic DNA (RAPD) analysis.Results Most isolates (63/70； 90％) were susceptible to amikacin but rates of susceptibility to other antibiotics varied from moderate,clarithromycin (60％) and imipenem (43％),to low for ciprofloxacin and ofloxacin (3％),and 87％ of isolates had intermediate susceptibility to cefoxitin.RAPD analysis showed that the 70 clinical isolates displayed 69 unique RAPD patts.Conclusions The high genetic diversity of isolates suggests that they are not transmitted from person to person but,presumably,are acquired independently from environmental sources.M.abscessus isolates displayed variable levels of susceptibility to all antibiotics tested,other than amikacin,indicating a need for routine susceptibility testing to guide treatment.