Delayed post-operative wound infections due to non-tuberculous Mycobacterium

The non-tuberculous mycobacteria (NTM) have emerged as important opportunistic pathogens of human beings in the recent years. The NTM are rapid growing mycobacteria (RGM), which include Mycobacterium fortuitum and M. chelonae and grouped as M. fortuitum-chelonae complex. Though there are reports on isolation of NTM from various parts of India, information on its occurrence in northeastern India is lacking. We therefore undertook this preliminary investigation to report on the occurrence of NTM-associated with non-healing postoperative wound infections that did not respond to antibiotics used for pyogenic infections and having sterile routine aerobic cultures in patients from northeastern part of India.

Pus/discharge from 25 patients with delayed onset of post-operative wound infections not responding to antibiotics used for pyogenic infections were collected and examined for isolation and identification of the causative agents.

Of the 25 pus/discharge specimens examined, 20 revealed growth of non-tuberculous Mycobacterium spp. All the isolates were identified as M. fortuitum-chelonae complex. Of these only 10 samples revealed acid-fast bacilli (AFB) on direct examination of Ziehl-Neelsen stained smears from the specimens. All cases where direct smear was positive for AFB were also positive for Mycobacterium culture.

The results of the present study indicated that non-tuberculous mycobacterial post-operative wound infection was fairly common in northeastern India. Thus, mycobacterial infections should be considered in wounds that show delayed healing and do not respond to antibiotics used for acute pyogenic infections. Further, 80 per cent of the specimens yielded the growth of AFB in cultures as against only 40 per cent positive in the ZN stained direct smears. This indicates the possibility of missing a mycobacterial wound infection if only direct smears are taken for diagnosis.