Notes from the Field: Mycobacterium abscessus Infections Among Patients of a Pediatric Dentistry Practice — Georgia, 2015

On September 13, 2015, the Georgia Department of Public Health (DPH) was notified by hospital A of a cluster of pediatric Mycobacterium abscessus odontogenic infections. Hospital A had provided care for nine children who developed presumptive or confirmed M. abscessus infection after having a pulpotomy at pediatric dentistry practice A (dates of onset: July 23, 2014–September 4, 2015). During a pulpotomy procedure, decay and the diseased pulp are removed to preserve a deciduous tooth. DPH initiated an investigation to identify the outbreak source and recommend prevention and control measures.

M. abscessus, a rapidly growing, nontuberculous mycobacterium (NTM), is found ubiquitously in the environment in water, soil, and dust. It commonly causes skin and soft tissue infection and can cause disease in multiple organs (1). NTM species display tolerance to commonly used disinfectants and are frequently found in the plumbing of health care facilities and water distribution systems (2). Improperly maintained dental unit water lines can permit growth and amplification of microorganisms, including NTM, which can form a biofilm and replicate within waterline tubing (3). Outbreaks have been reported in different clinic settings, including acupuncture clinics, a cosmetic surgery clinic, and a general medical clinic, although not dental clinics (4–7).

Probable cases were defined as occurrence of facial or neck swelling and biopsy-confirmed granulomatous inflammation among children with an illness onset date on or after January 1, 2014. Confirmed cases were those in which M. abscessus was isolated by laboratory culture. Active case finding included contacting all patients who had a pulpotomy since January 1, 2015, notifying area pediatricians and dentists of the outbreak, and reviewing hospital A pathology reports and M. abscessus positive cultures since January 1, 2014. DPH staff visited practice A on September 22, 2015, to evaluate infection control and prevention practices, and to view a mock pulpotomy demonstration. Practice A used tap water for pulpotomies without water quality monitoring or bleaching of waterlines at the end of each day, as recommended in the manufacturer guidelines.* No other infection control deficiencies were noted. Water samples were collected for microbiologic analysis, and patient and water sample isolates were sent to CDC for molecular characterization by pulsed-field gel electrophoresis (PFGE).

Practice A had performed 1,386 pulpotomies since January 1, 2014. As of January 1, 2016, a total of 20 patients with confirmed (n = 11) or probable (n = 9) M. abscessus infections were identified, resulting in an attack rate of 1%; case finding is ongoing. Median patient age was 7 years (range = 3–11 years), and median incubation period was 65 days (range = 18–164 days). All patients were severely ill, requiring hospitalization at least once for a median of 7 days (range = 1–17 days); 17 patients required surgical excision and 10 received outpatient intravenous antibiotics (Table). As of April 5, 2016, no deaths have resulted from infection.

All water samples from the seven dental stations had bacterial counts above the American Dental Association recommended ≤500 colony-forming units (CFU)/mL (average = 91,333 CFU/mL); M. abscessus was isolated from all water samples. All water and patient isolates were indistinguishable by PFGE, indicating a common source.

This outbreak was caused by contaminated water used during pulpotomies, which introduced M. abcessus into the chamber of the tooth during irrigation and drilling. M. abscessus can cause severe infection among immunocompetent children, and because M. abscessus is ubiquitous in the environment, it poses a contamination risk. To prevent infections associated with waterlines, dental practices should follow manufacturer guidelines to disinfect waterlines, monitor water quality to ensure recommended bacterial counts, use point-of-use water filters, and eliminate dead ends in plumbing where stagnant water can enable biofilm formation (3,8). Health care providers should promptly report suspected outbreaks of infectious diseases to public health authorities so that an investigation can be initiated and appropriate control measures implemented.

Corresponding author: Gianna Peralta, MPH, Gianna.Peralta@dph.ga.gov, 404-463-0782.

¹Georgia Department of Public Health; ²CDC/CSTE Applied Epidemiology Fellowship Program; ³Epidemic Intelligence Service Program, CDC; ⁴Division of State and Local Readiness, Office of Public Health Preparedness and Response, CDC.

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TABLE. Demographic characteristics, symptoms, diagnostic evaluations, and treatment of 20 patients with confirmed or probable Mycobacterium abscessus infections — Georgia, March 12, 2014–November 12, 2015

Abbreviations: AFB = acid-fast bacteria; CT = computed tomography; IV = intravenous; MRI = magnetic resonance imaging; NA = not available; PICC = peripherally inserted central catheter.
* Age at illness onset.
^† Amikacin or amikacin and cefoxitin by PICC.
^§ Two (11%) AFB cultures are pending.