Outbreak of Mycobacterium mucogenicum Bloodstream Infections in a Tertiary Care Medical Center

Background : Mycobacterium mucogenicum is a slow-growing, nontuberculous environmental mycobacterium which behaves as an opportunistic pathogen.  Outbreaks of M. mucogenicum bloodstream infection (BSI) have been linked to contaminated water and hematologic malignancy.  BSIs are associated with increased morbidity and mortality, especially in the compromised host.  We report the investigation of a cluster of cases of BSI due to M. mucogenicum. 

Objective :  To investigate an outbreak of M. mucogenicum BSIs at a tertiary care hospital using isolates recovered from both clinical and environmental specimens.

Methods :  M. mucogenicum was recovered from the blood in 7 patients (pt) from 2005-2010, with 4 in 2009.  A retrospective review of medical records for the pts identified in 2009 was conducted in an attempt to identify common potential points of exposure. Routine water sample surveillance was obtained for mycobacteria; these were correlated geographically with clinical cases.. Molecular analysis via pulsed field gel electrophoresis to confirm this connection is planned.

Results :  Four unique pts had M. mucogenicum BSI identified during 2009.  All were associated with the presence of an indwelling central venous catheter (CVC).  Two were associated with both hematologic malignancy and bone marrow transplantation (BMT) and were recently hospitalized in the BMTU.  One was associated with a coagulase negative Staphylococcus sp. BSI, the other with a Klebsiella oxytoca BSI.  Two separate BSIs were associated with inappropriate manipulation of the indwelling CVC by the pt; both were also associated with a polymicrobial bacteremia primarily due to non-lactose fermenting gram negative rods and skin flora.  A more detailed review of pt isolates from 2005-2010 identified an additional 3 patients, validating that 4 cases identified during 2009 constituted an outbreak.  These pts also had indwelling CVCs with a history of inappropriate access or a hematologic malignancy. Environmental isolates from potable water were correlated with pt isolates based upon patient room  location.  Molecular analysis to confirm this connection is pending.

Conclusions :  An epidemiological investigation confirmed the suspicion of an outbreak of M. mucogenicum BSIs with the hospital water supply as a potential mycobacterial reservoir and source of infection.  Pulsed-field gel electrophoresis of clinical and environmental isolates is pending.  Indwelling CVCs with inappropriate manipulation or hematologic malignancy were identified as risk factors.