Molecular epidemiology of Mycobacterium abscessus infections in a subtropical chronic ventilatory setting

The aim of this study was to investigate the high level of pulmonary Mycobacterium abscessus infections and implement a surveillance programme among 43 ventilator-dependent patients, 15 with pulmonary M. abscessus infections, in a hospital long-term respiratory care ward (RCW) in central Taiwan. M. abscessus isolates were obtained from 35 patients in the RCW of hospital A, 6 patients in the RCWs of another three hospitals (B, C and D), and from 4 water sources in two of the hospitals (A and B). Strains were characterized by methods including hsp65 PCR-RFLP and PFGE. The patients were followed-up by chest X-ray for 1 year. All clinical isolates were type I and II, and belonged to ten distinct clusters of PFGE patterns. Five clinical strains in two hospitals belonged to a single cluster, whilst four clinical strains in the other two hospitals belonged to a single unique cluster. The strains from hospital A fell into nine clusters and were distinct from the strains isolated from the water supply. Patients infected with type I strains showed a significantly more rapid progression of disease. The number of different strains involved suggested either that there had been a polyclonal outbreak or that a high level of endemic infections was present in the RCW of hospital A. This and the lack of homology between the clinical and environmental isolates from hospital A raised the possibility that pulmonary M. abscessus infections may have been spread by the movement of patients between RCWs, a routine practice in Taiwan's integrated delivery system.