First United States Outbreak of Mycobacterium abscessus Hand and Foot Disease Among Children Associated With a Wading Pool

BACKGROUND

Mycobacterium abscessus, an emerging pathogen in healthcare settings, has rarely been associated with community outbreaks. During February-May 2013, Idaho public health officials and pediatric infectious disease physicians investigated an outbreak of M abscessus skin infections in children whose only common exposure was an indoor wading pool.

METHODS

Healthcare providers and parents reported possible M abscessus cases. We used a standardized questionnaire to interview parents of affected children. Clinical specimens were submitted for mycobacterial examination. We conducted an environmental investigation of the pool. Microbial isolates from clinical and environmental samples were identified by sequencing polymerase chain reaction amplicons and underwent pulsed-field gel electrophoresis.

RESULTS

Twelve cases were identified. Specimens from 4 of 7 children grew M abscessus or Mycobacterium abscessus/Mycobacterium chelonae . Ten (83%) of 12 children were female; median age was 3 years (range, 2 to 6 years); and all were immunocompetent. Pool maintenance did not fully comply with Idaho state rules governing pool operation. Mycobacterium abscessus/chelonae was isolated from pool equipment. Pulsed-field gel electrophoresis composite patterns were 87% similar between isolates from the pool ladder and 1 patient, and they were 90% similar between isolates from 2 patients. Environmental remediation included hyperchlorination, scrubbing and disinfection of pool surfaces, draining the pool, and replacement of worn pool materials.

CONCLUSIONS

Immunocompetent children acquired M abscessus cutaneous infection involving hands and feet after exposure to a wading pool. Environmental remediation and proper pool maintenance likely halted transmission. Medical and public health professionals' collaboration effectively detected and controlled an outbreak caused by an emerging recreational waterborne pathogen.

Mycobacterium diagnostics: from the primitive to the promising

The field of clinical microbiology has been revolutionised by genomic and proteomic methods, which have facilitated more rapid diagnosis and characterisation of infection in many cases. In contrast, mycobacteriological evolution has tended to retain the traditional methods of smear microscopy for detection of acid-fast bacilli to indicate mycobacteria, along with culture, and in synergy with more modern molecular methods. Thus, efforts have been focused on reducing the time to diagnosis of infection, while increasing the amount of diagnostic information available, including more definitive speciation, and more rapid susceptibility test results. Although smear microscopy remains a mainstay for the laboratory-based diagnosis of mycobacterial infection, molecular testing has vastly reduced the time needed for identification of Mycobacterium tuberculosis in particular, when compared with traditional culture-based techniques. Molecular methods may also yield antimicrobial susceptibility results through testing for the most common resistance-inducing mutations to some of the antimicrobial agents of choice. However, the diversity of resistance mutations already characterised suggests that these currently-available molecular detection systems should be accompanied by culture-based susceptibility testing. This review compares the efficacy of microscopic, phenotypic, proteomic and genotypic methods available for mycobacterial diagnosis. The diversity of methods currently in use reflects the complexity of this area of diagnostic microbiology.