Advanced laboratory diagnostic techniques have improved the isolation and identification of nontuberculous mycobacteria. Mycobacterium gordonae, a commonly found species of mycobacteria, is named after its discoverer, the American bacteriologist Ruth E. Gordon. It is classified in Runyon group 2 as a scotochromogenic organism. Cultures grow slowly, are smooth, and are pigmented yellow. M gordonae is referred to as the tap water bacillus because it is a frequent isolate in tap water. 
M gordonae is ubiquitous and may be found in soil, water (eg, ground, tap, bottled), whirlpools, unpasteurized milk, mucous membranes of healthy persons, urine, and gastric fluid. It is the most commonly encountered nontuberculous mycobacterium in water, with concentrations as high as 1000 colony-forming units per milliliter.
After analyzing the molecular epidemiology of M gordonae infections in hospital environments, Yoshida et al concluded that effective and continuous surveillance is necessary. 
New cases of M gordonae disease should always be published to increase the knowledge of this disease. Many isolates represent contamination of the specimen or colonization, but not true disease. Discussing positive culture findings with microbiology laboratory personnel is useful. The authors are willing to discuss any possibly new case of M gordonae infection and are willing to offer support to write up cases of actual disease.
M gordonae is one of the least pathogenic of the mycobacteria. It is usually a contaminant or colonizer in patients who are not infected with HIV. However, in patients with HIV infection who are severely immunosuppressed (count of < 100 CD4+ cells/µL), M gordonae may infect the lungs, blood, bone marrow, and other organs. In the few published case reports of M gordonae disease, pathogenicity was not always established because of the presence of single isolates, the lack of confirmation by a reference laboratory, or the rapid improvement of pulmonary infiltrates, which are not characteristic features of infections from other mycobacterial species.
M gordonae disease is rare. While more than 100 cases have been reported, most documentation supports contamination or colonization rather than pathogenicity. Nosocomial pseudo-outbreaks have been described from tap water, ice machines, antimicrobial and laboratory solutions, instrumentation, fiberoptic bronchoscopes and colonoscopes (especially if the working channel is not adequately exposed to disinfectant), aerosol devices, and (possibly) continuous ambulatory peritoneal dialysis fluid.
Worldwide distribution of M gordonae infection is probable. Additional studies with adequate documentation are warranted to investigate the pathogenicity of M gordonae.
M gordonae infection carries a mortality rate of less than 0.1%. M gordonae may be a marker of severe immunosuppression in patients infected with HIV. One death was reported in a patient who was HIV positive and had severe immunosuppression, acute respiratory distress syndrome, and multiple isolates of M gordonae.
M gordonae infection has no recognized racial predilection.
M gordonae infection has no known sexual predilection.
M gordonae infection has no determined age predilection.
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