Cluster of cases of Mycobacterium chelonae bacteraemia

Mycobacterium chelonae was isolated from the blood of four immunosuppressed patients over a period of 10 weeks. Three patients had intravascular catheters in situ and the other had a biliary stent. All presented with recurrent fever despite treatment with broad-spectrum antibiotics. Blood cultures using standard bacteriological medium yielded a gram-positive bacillus from each patient. Ziehl-Neelsen staining of these cultures demonstrated a branching acid-fast bacillus that was subsequently identified as Mycobacterium chelonae in each case. The isolates were sensitive to clarithromycin and, although success of treatment with clarithromycin monotherapy has been variable, this antibiotic combined with removal of the intravascular catheters was used to treat those three patients. The treatment was successful with no recurrence of symptoms after 12 months of follow-up. The patient with the biliary stent died soon after Mycobacterium chelonae was isolated. Pyrolysis mass spectrometry analysis indicated the isolates were of two distinct strains. Radiological insertion of the Hickman lines and biliary stent was implicated epidemiologically as the source of infection.