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Background: Nontuberculous mycobacteria (NTM) have been identified in human pulmonary and extrapulmonary infections and are increasing globally, which makes it challenging to identify them. This article reports our experience with the laboratory identification of NTM in clinical practice among pulmonary and extrapulmonary samples received in our routine work. Methods: The study was conducted at the Universite Catholique de Louvain at the Cliniques Universitaires Saint-Luc, Brussels, Belgium, from 2015 to 2018. A total of 386 clinical samples were collected from patients suspected of having pulmonary or extrapulmonary mycobacterial infections. Routine laboratory methods phenotypic and molecular tests were performed. Results: The majority of NTM species were isolated from pulmonary samples (68%). The most prevalent species identified were Mycobacterium chimaera_intracellulare group (32%), followed by Mycobacterium avium complex (21%), Mycobacterium abscessus complex (18%), Mycobacterium gordonae (9%), and Mycobacterium chelonae (4%). In extrapulmonary samples, M. avium and M. chimaera_intracellulare were the most frequently isolated. Conclusion: The species diversity of NTM found in our setting suggests the importance of the use of new modern methods for accurate identification of NTM at species level and in some case at subspecies level for the proper treatment and management of patients.

Background: There is evidence that drinking water could be a source of infections with pathogenic nontuberculous mycobacteria (NTM) potentially risky to human health. The aim was to investigate the resistance of two NTM isolated from drinking water, Mycobacterium gordonae and Mycobacterium chubuense, at different concentrations of chlorine (as sodium hypochlorite), used in drinking water sanitation. Methods: The NTM were grown in suspension and in biofilms and were challenged with biocide for 10 and 60 min. Results: To obtain 7-log reduction from the initial population of M. chubuense, in the planktonic state, there were necessary 20 ppm of chorine and 60 min of exposure. The same effect was achieved in M. gordonae with 10 ppm for the same period. The maximum reduction of both NTM in biofilm was 3-log reduction and was achieved using 30 ppm for 60 min. The chlorine susceptibility of cells in biofilms was significantly lower than that of planktonic cells. The results highlight the resistance of both NTM to the concentrations used in routine water sanitation (0.2 ppm according to Argentine Food Code). Differences in chlorine resistance found between the two NTM in planktonic growth decrease when they are grown in biofilm. Conclusion: This suggests that current water disinfection procedures do not always achieve effective control of NTM in the public supply system, with the consequent health risk to susceptible population, and the need to take into account biofilms, because of their deep consequences in the way to analyze the survival of prokaryotic cells in different environments.

Over the last 30 years, there have been at least 17 published reports of nontuberculous mycobacteria (NTMs) being isolated from hospital ice or ice-making machines. Of these, 12 were reports of pseudo-outbreaks, i.e., the nosocomial transmission of organism from hospital ice/ice machines to patients, resulting in patient colonization, but with no disease manifestations. In addition, there were five outbreaks that resulted in clinical disease/pathology associated with NTM organism. Eleven different species of NTMs have been associated with these reports, where over half (59%) of the species identified were Mycobacterium fortuitum (18%), Mycobacterium gordonae (14%), Mycobacterium mucogenicum (14%), and Mycobacterium porcinum (14%). Several of these reports clearly documented that ice machines had been properly maintained, cleaned, and serviced in accordance with the CDC guidelines yet became contaminated with NTM organisms. These reports frequently detail that after extensive cleaning/disinfection following the discovery of NTM organisms, ice machines remained contaminated with NTM organisms, highlighting the difficulty in eradicating these from ice machines, once contaminated. Several reports identified that the only remedy to the contamination problem was to replace the ice machine with a new machine. Two qualitative risk assessment models are presented for (i) patients exposed to contaminated ice machine but before NTM colonization/infection and (ii) patients already colonized with NTMs from ice machines. Therefore, to protect immunocompromised/immunosuppressed patients' safety, especially during surgical or respiratory procedures, ice should not be sourced from the ice machine but should be made from sterile water and stored safely and separately away from the ice machine.

Nontuberculous mycobacteria (NTM) are environmental, opportunistic pathogens found in soil and water. NTM are adapted for residence in drinking water distribution systems as they are disinfectant-resistant, surface adherent, and able to grow on low concentrations of organic matter. Reports of NTM infections have been increasing over the past two decades. Of the >150 NTM species reported in the literature, some 25 species have been strongly associated with a variety of human diseases, of which the pulmonary NTM disease (PNTM) is the most frequent. The distribution of NTM species differs strongly by region and it is generally accepted that NTM species differ in their clinical relevance. Further, NTM differ strongly in their growth rate, temperature tolerance, and drug susceptibility, making the correct species identification a very important step in the process of diagnosis. Because NTM are environmental bacteria, the diagnosis of PNTM is complex and requires good communication between clinicians, radiologists, and microbiologists. Extensive microbial resistance, often misleading in vitro drug susceptibility patterns, and complicated treatment regimens are just some of the factors adding to the frustration of the clinical management of NTM diseases. To prevent unwarranted diagnoses and treatment of NTM disease as well as unnecessary diagnostic delay, it could be helpful to use separate, more stringent criteria for species of low relevance, and less stringent criteria for species considered to be of high clinical relevance in the local setting, namely: isolation of Mycobacterium kansasii (worldwide) and Mycobacterium malmoense (north-western Europe) from pulmonary specimens usually indicates disease, whereas Mycobacterium gordonae and Mycobacterium simiae typically represent contamination. This approach requires complete and up-to-date insight in locally prevalent NTM and their clinical relevance. In Croatia, all strains of NTM isolated in any laboratory are sent to the National Reference Laboratory for identification. NTM strains have been systematically recorded and reported since 1982. In the last decade, two retrospective analyses were done to assess the clinical relevance of different NTM species and the burden of pulmonary NTM disease. Over the past decade, a 30-fold increase in overall NTM isolation rates and a 4-fold increase in PNTM incidence were observed. Mycobacterium xenopi was the most frequently seen causative agent of pulmonary NTM disease, but the degree of clinical relevance (i.e., percentage of patients meeting the diagnosis criteria, per species) was higher for isolates of MAC (66.5%) and M. kansasii (57.2%). Only about 30% of the M. xenopi isolates represented true disease. Further, interesting regional differences were observed. Clinically relevant NTM isolates were significantly more often found in the coastal region of Croatia, and the average annual incidence of the PNTM was twice as high in coastal compared with the continental region. The overall burden of PNTM in Croatia is still low compared with tuberculosis. This can, in part, explain the observed lack of knowledge of NTM infections among respiratory specialists. Since these pathogens are increasingly common worldwide, especially in countries where the incidence of tuberculosis is declining, a constant rising of awareness and knowledge is necessary.

It is often difficult to discern true mycobacterial infection from colonization due to Mycobacterium gordonae (M. gordonae) since this organism is ubiquitous and is commonly an innocuous saprophyte. This study reports a rare case of caseating hilar adenopathy and pulmonary disease caused by M. gordonae in a patient with chronic obstructive pulmonary disease (COPD) and rheumatoid arthritis (RA) on maintenance steroids and methotrexate. Pathologic exam and cultures of lymph node excision biopsy and bronchoalveolar lavage (BAL) confirmed the diagnosis.Triple antimycobacterial therapy with azithromycin, ethambutol and rifabutin was administered. The patient had significant clinical and radiologic improvement and follow-up cultures confirmed microbiologic cure.Mycobacterium gordonae can be a rare cause of significant pulmonary infection, and positive sputum or BAL cultures for M. gordonae should not be automatically discarded and considered as nonpathogenic contaminants or colonizing organisms, especially in immunocompromised hosts with comorbidities. A detailed review of the case and relevant literature is provided.