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Mycobacterium chimera

STRUCTURE AND PHYSIOLOGY

Mycobacterium chimera is classified as a non-tuberculosis Mycobacterium that is a member of the Mycobacterium avium complex (MAC). As a member of MAC, Mycobacterium chimera is characterized as gram-positive, non-motile, and acid-fast-positive bacteria.

TRANSMISSION AND DISEASE

Mycobacterium chimera is an opportunistic pathogen responsible for respiratory infection mainly in immunocompromised subjects and particularly in patients with underlying respiratory diseases such as cystic fibrosis. Mycobacterium chimera has become a global public health concern due to infection following cardiac surgery performed with contaminated heater-cooler units. Mycobacterium chimera infection is characterized by a long latency, non-specific signs and symptoms, and high mortality rates. Mycobacterium chimera forms biofilms in heater-cooler unit water tanks of contaminated devices and then spreads through airborne transmission. Clinical manifestations of Mycobacterium chimaera infection include endocarditis, hepatitis, nephritis, encephalitis and chorioretinitis.

Currently, no standardized treatment for Mycobacterium chimera infection exists. Thus, antibiotic therapy should be guided by the results of a drug susceptibility test performed in a reference center for mycobacterial pathogens.

DISINFECTION

The combination of an enzyme detergent cleaning agent and Clorox® was equivalent to Clorox alone in reducing M. chimaera CFU in heater-cooler water reservoir samples. However, the reappearance of those bacteria was delayed by 12 weeks by the combination of enzyme detergent cleaning agent and Clorox exposure compared to Clorox disinfection alone.

Mycobacterium chimera tends to form biofilms. It was found in a 2020 study that uses an enzyme detergent as a cleaning agent to help disrupt the biofilm.

UNIQUE OR INTERESTING FACTS

After E. Tortoli sequenced the bacteria in 2004 and found it similar to three other Mycobacterium, the name “chimaera” was proposed to identify the species; after the Greek mythical creature that is composed of parts from three different animals.

REFERENCE(S)

Falkinham, J. O. (2020). Disinfection and cleaning of heater-cooler units: suspension- and biofilm-killing. Journal of Hospital Infection, 105(3), 552-557. https://linkinghub.elsevier.com/retrieve/pii/S019567012030236X

Henry, R. (2017). Etymologia: <em>Mycobacterium chimaera</em>. Emerging Infectious Disease journal, 23(3), 499. https://doi.org/10.3201/eid2303.et2303

Miskoff, J. A., & Chaudhri, M. (2018). Mycobacterium Chimaera: A Rare Presentation. Cureus, 10(6), e2750-e2750. https://doi.org/10.7759/cureus.2750

Natanti, A., Palpacelli, M., Valsecchi, M., Tagliabracci, A., & Pesaresi, M. (2021). Mycobacterium chimaera: a report of 2 new cases and literature review. International journal of legal medicine, 135(6), 2667-2679. https://doi.org/10.1007/s00414-021-02630-y

Image from: https://www.jtcvs.org/article/S0022-5223%2817%2933001-5/fulltext

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