Article
Mycobacterium abscessus is a rapidly growing non-tuberculous mycobacterium (NTM). It is ubiquitous in the environment. Commonly found in water, soil and dust and is known to contaminate medications and medical devices. M. abscessus transmission is usually caused by injection of contaminated substances or through invasive medical procedures using contaminated equipment. Infection can also occur after a wound is contaminated with soil. There is minimal risk of person-to-person transmission.
Healthcare-associated infections usually involve the lungs; however, other sites can be affected. Infection of skin, underlying soft tissues and multiple organs results in inflammation, sometimes with the development of boils and/or pus-filled vesicles, including slowly progressing dental abscesses. Treatment involves pus drainage and debridement followed by prolonged combinations of antibiotics. Infections are usually resistant to antibiotics commonly used to treat skin infections. Mycobacterial culturing must be specifically ordered because the presence of such organisms is not detected using routine bacterial methods.1,2
NTM species are resistant to common disinfectants and are frequently found in the plumbing of healthcare facilities and water distribution systems. Improperly maintained dental units allow the proliferation of micro-organisms, including NTM. The microbes adhere and replicate in biofilms inside waterline tubing. Before 2015, outbreaks have been reported in healthcare facilities, including acupuncture, surgery and general medical clinics, but not dental facilities.1,2
The Georgia Department of Public Health (GDPH) announced a cluster of pediatric M. abscessus odontogenic infections among patients who had undergone pulpotomy procedures during October 2013 – September 2015. During the pulpotomy procedure, decay and the diseased pulp were removed to preserve a deciduous tooth. The GDPH initiated an investigation to identify the outbreak source and recommend preventive and control measures.1,2 A total of 23 patients (13 confirmed and 10 probable) were identified (attack rate of approximately 1%). Case finding is ongoing. The median age was 7 years (range = 3–11 years) and median incubation period was 64 days (range = 18–139 days). All patients became severely ill, requiring more than one hospitalization for a median of 8 days (range 3–19 days). Eleven required complete surgical excision and all received medication, in many cases for ≥12 weeks. Seventy-four percent had complications associated with management, including tooth loss, high-frequency hearing loss, adverse drug reactions, fibrosis, transient facial palsy, acute kidney injury and drug-induced neutropenia. Of pulpotomies, 96% came from a single office associated with a group practice. No deaths were reported and none of the patients was immunocompromised.1,2
The GDPH observed a mock pulpotomy procedure on 22 September 2015. The practice used tap water without water quality monitoring or some form of waterline disinfection and/or purging. Water specimens from all seven dental operatories were collected and analysed. All seven had microbial levels far above the ADA recommended 500 colony-forming units per mL (average = 91,333). M. abscessus was present in all units and was indistinguishable from patient isolates, indicating a common source.1
On 14 October 2016, there was a second report of M. abscessus infections among patients having a pulpotomy procedure at a pediatric dental office in Anaheim, California. By June 2017, there had been 73 cases with 22 confirmed and the other 51 considered probable. All affected patents had a pulpotomy between 4 February–20 August 2016.3,4,5
From 1 January–6 September 2016, the office treated 1082 patients, resulting in a 6.7% attack rate. All save one patient were hospitalized for surgery at some point. The age range for all cases was 2–11 years.3,5
Symptoms began a median 71 days (mean = 112 days; range = 1–409 days) after the pulpotomy and progressed despite antibiotic treatment, such as amoxicillin, Augmentin® and clindamycin. Because the incubation time has been more than 10 months and initial symptoms can be mild, infected patients must be monitored repeatedly for an extended period.3,5
The clinic's internal water system appears to have been the source of the mycobacterium, based on local health department assessment and laboratory testing results. The clinic discontinued pulpotomy procedures from 6 September–7 November 2016 and replaced its water system and installed appropriate infection control procedures.3,4,5
On 15 December 2106, the clinic began performing pulpotomies again. The local health department performed a follow-up testing and found Mycobacterium mucogenicum in multiple water specimens. M. mucogenicum is not known to pose the same risk as M. abscessus; however, the presence of any mycobacterium, even at low levels, is troubling. The local county health officer ordered the clinic closed until another investigation was completed. None of the treated children has developed symptoms of mycobacterial infection. However, they will be followed and treated immediately if symptoms develop. After further testing, the local county health officer, on 11 March 2017, permitted the clinic to re-open and resume patient care.3,4,5