M. fortuitum and M. chelonei—fast growing mycobacteria.

Abstract

Infection due to opportunist mycobacteria is considered in general and that due to the fast growing mycobacteria in particular. The group is now seen to contain two facultative pathogens, M. fortuitum and M. chelonei (abscessus), all other synonyms for these two species having been shown to be invalid. Both organisms are ubiquitous and normally harmless; however, following injury or injection, they may cause chronic sub-cutaneous abscesses. Pulmonary lesions have also been described. More recently M. fortuitum has been found to cause osteomyelitis and corneal ulceration and both organisms have been identified in cases of septicaemia associated with renal dialysis. In the past M. chelonei my have been identified as M. fortuitum but although it is more difficult to isolate, it may in fact be the more common cause of disease. A case is reported of an English girl who received a small injury to her shin in Spain. The initial lesion failed to heal and for 18 months there was repeated formation small sinuses in the area. Healing then occurred spontaneously. Histology showed a chronic granuloma and on two occasions a rapid growing mycobacteria resistant to all antibiotics was isolated. This was initially identified as M. fortuitum but finally as M. chelonei and the latter diagnosis was confirmed by differential skin tests. Difficulties in interpretation of these tests are discussed.