BACKGROUND: Mycobacterium abscessus, a bacterium found in water, soil, and dust, can cause severe infection and colonize waterlines by forming biofilms. Dental unit waterlines can become contaminated and develop biofilms if not properly maintained. Outbreaks of M. abcessus have been reported in various clinical settings, although not dental clinics. In September 2015, hospital A notified the Georgia Department of Public Health of nine cases of M. abscessus infection among children who had dental procedures at practice B during the previous 13 months. We investigated to identify additional cases and recommend prevention and control measures.
METHODS: Cases were defined as illness compatible with M. abscessus infection among children with an onset date on or after January 1, 2014. Probable cases were defined as occurrence of facial or neck swelling and biopsies showing granulomatous inflammation. Confirmed cases were culture-positive for M. abscessus. Active case finding included contacting all patients with a history of pulpotomy or extraction, and notifying area pediatricians and dentists of the outbreak. We assessed practice B’s infection control practices, collected water samples for microbiologic analysis, and sent patient and water sample isolates to CDC for molecular characterization by pulsed-field gel electrophoresis (PFGE).
RESULTS: Twenty-two cases were identified; 13 (59%) were culture-confirmed. All case-patients had a history of pulpotomy at practice B <6 months before symptom onset. Onset age range was 3–10 years (median: 7 years); 12 (55%) were male; and none were immunocompromised. Symptoms included pain (19, 86%), gingival swelling (17, 77%), facial swelling (14, 64%), and lymphadenopathy (21, 95%). All underwent surgical intervention, 16 (73%) had osteomyelitis; seven (32%) had pulmonary nodules; 10 (10%) required outpatient intravenous antibiotics. All case-patients were hospitalized at least once for 1–17 days (median: 5.5 days). Practice B used tap water for pulpotomies without recommended water quality monitoring or bleaching of waterlines at the end of each day. Water bacterial counts from all seven dental stations at practice B exceeded the CDC's recommendation of ≤500 CFU/mL. All water samples cultured M. abscessus that matched the PFGE pattern of patient isolates, indicating a common source.
CONCLUSIONS: Contaminated water used during pulpotomies likely caused this outbreak. Poor water quality can result in M. abscessus transmission during invasive procedures. Prevention efforts should focus on eliminating potential sources of potable water contamination and assuring good adherence to general infection prevention methods. Dental practices should adhere to recommendations regarding equipment maintenance and water quality monitoring. Water bacterial counts from all seven dental stations at practice B exceeded the CDC's recommendation of ≤500 CFU/mL.