2023 Highlights
- In 2023 there were 148 confirmed and 114 pending pulmonary cases of NTM among residents of Ramsey and Hennepin County. There were 106 cases of ENTM statewide.
- Of the 106 cases of ENTM, 51 individuals were interviewed. One cluster of infections (three cases) related to peritoneal dialysis catheters was identified through these interviews.
- A MN physician identified two individuals who had tattoo related M. chelonae skin infections, and investigation found the isolates of M. chelonae were highly related, indicating a common source.
Extrapulmonary Species Distribution by Surveillance Year (number of species isolated per year)
| Species | 2021 | 2022 | 2023 |
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| M. avium complex (not further speciated) | 28 | 23 | 15 |
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| M. avium | 9 | 5 | 10 |
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| M. intracellulare | 2 | 1 | 3 |
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| M. chimaera | 0 | 1 | 1 |
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| Other M. avium complex | 0 | 2 | 0 |
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| Non-avium complex | - | - | - |
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| M. abscessus | 17 | 17 | 16 |
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| M. chelonae | 17 | 23 | 31 |
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| M. fortuitum | 11 | 18 | 11 |
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| M. kansasii | 2 | 2 | 3 |
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| Other non-avium complex species | 28 | 17 | 20 |
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*more than one species can be identified from one isolate
Non-tuberculous mycobacteria (NTM) consist of species of mycobacteria, excluding M. tuberculosis and M. leprae (the causative agents of tuberculosis and Hansen’s disease, respectively). They are generally categorized as slow or rapid growers. Slow growing NTM include members of the M. avium complex (M. avium, M. intracellulare, M. chimaera), M. kansasii, and M. marinum among others. Rapid growers include members of M. abscessus complex, M. chelonae complex, and M. fortuitum group, as well as numerous other species.
For the purposes of surveillance, NTM cases are further categorized as pulmonary and extrapulmonary (ENTM). NTM most commonly causes pulmonary disease but can also cause disease in many other parts of the body including lymph nodes, soft tissue, skin, and blood. NTM disease most commonly effects those with underlying lung disease (chronic obstructive pulmonary disease, cystic fibrosis, bronchiectasis) and immune suppression (HIV/AIDS, chemotherapy, rheumatoid arthritis, multiple sclerosis, tissue/organ transplant). Although many patients with pulmonary NTM infection do not know where or how exposure occurred, some pulmonary infections have been linked to contaminated water supplies in health care facilities, which can go on to contaminate medical devices. ENTM disease often occurs through direct inoculation, such as exposure of open wounds to freshwater or dirt, injection of medication or other substances with non-sterile devices or diluent, or traumatic wounds with sharp objects such as metal nails or staples. For both pulmonary and extrapulmonary NTM, transmission from person to person is rare. Some types of NTM infections are difficult to treat due to multi-drug resistance of the organisms and the need for a long duration of treatment. Treatment is often managed with pulmonary, surgical, and/or infectious disease specialists.
Surveillance for NTM began in 2019 in Hennepin and Ramsey Counties. A case of pulmonary NTM is considered confirmed if NTM is identified (by culture or culture-independent test) in either one bronchoalveolar lavage/washing specimen or one specimen from a lung biopsy, or two sputum or tracheal aspirate specimens that have NTM identified within 12 months. An ENTM case is confirmed in a patient who has NTM identified in a non-pulmonary specimen (excluding stool or rectal swabs). In 2021 surveillance expanded statewide for ENTM cases. Starting in 2023, ENTM cases are interviewed to look for common exposures and to collect any information that may not be found in the medical record.
In 2023, there were 106 ENTM cases reported statewide, with 105 incident cases and one prevalent case. The incidence rate of ENTM for 2023 was 1.8 cases per 100,000 persons.
Of the 106 ENTM cases, the majority of cases resided in Hennepin (18%), Ramsey (6.6%), and Dakota County (6.6%); 52% of cases were female, and median age was 53 years (range <1 to 87 years). Fifty-nine percent of cases were White, 8% Black, 8% Asian, 3% American Indian/Alaskan Native, and 18% were of unknown race. Five percent of ENTM cases were Hispanic.
Of the 106 index specimens collected, 29 isolated M. avium complex (MAC) group and 75 were of non-M. avium complex mycobacteria. Note that specimens can isolate more than one species of NTM. Of non- M. avium complex species isolated, 71% belonged to M. abscessus complex, M. chelonae complex, and M. fortuitum group. Surgical and non-surgical wounds (19%), Blood (17%), Lymph node (13%), and skin (11%) were the most common specimen collection sites. The most common infection types diagnosed were lymphadenitis (11%), bloodstream infection (10%), and disseminated infection (11%). The most common underlying condition was diabetes (23%) and 50% of those cases (n=12) had chronic complications associated with diabetes, such as nephropathy, chronic kidney disease, and retinopathy. Of exposures that occurred at site of infection in the 12 months prior to diagnosis, surgery was identified in 16% of cases, trauma in 9% of cases and in-dwelling medical devices in 11% of cases. Note that multiple exposures can be selected for each individual.
There were 148 confirmed pulmonary cases reported in Hennepin and Ramsey Counties, with 17 cases considered prevalent and 121 incident cases. There were 114 pending pulmonary cases in 2023. Pending pulmonary cases have up to 12 months from the index specimen date to be confirmed, so the number of confirmed cases could change. The incidence rate of confirmed pulmonary cases in Hennepin and Ramsey counties in 2023 was 6.6 per 100,000 persons. 79% of cases were residents of Hennepin County and 21% of Ramsey County. Fifty-four percent of cases were female and 46% were male. The median age of cases was 70 years (range 4 to 95 years). Seventy-two percent of confirmed cases identified as white, 10% African American, 9% Asian. Cases can identify as more than one race in the medical record. Only two cases were of Hispanic ethnicity. Seventy percent of index specimens collected from confirmed cases isolated M. avium complex group and 33% isolated non-mac species. Specimens commonly isolate more than one species of NTM. The most common index specimen type in confirmed cases was sputum (52%) and bronchoalveolar lavage/wash (46%). The most common underlying condition for confirmed pulmonary NTM was chronic lung disease (48% of confirmed cases), which includes, but is not limited to, chronic obstructive pulmonary disease emphysema, chronic bronchitis, asthma, interstitial lung disease, bronchiectasis, and reactive airway disease. Forty-one percent of cases had a history of smoking tobacco.