Mycobacterium fortuitum is a Gram-negative bacillus. Its optimal growing temperature is 30-37°C, making it a thermophile. It is a chemoheterotroph and obligate anaerobe. It is described as acid-fast which means it resists decolorization by acified organic solvents. It is found in water, soil, and air.
Mycobacterium tuberculosis was identified by Robert Koch in 1882, and M. fortuitum was identified shortly after. It was classified as a nontuberculous mycobacterium (NTM) and not much thought was given to it until 1954. Edward Runyon took it upon himself to categorize all the NTMs at this time. M. fortuitum is now classified as Runyon Group IV, which means, among other lab culture characteristics, it is a rapid grower.
Infection in healthy humans is rare, but exposure to large and repeated amounts of the organism can overwhelm the immune system and cause disease. Infections most likely occur in immunocompromised patients.
Diseases and infections are varied and involve almost every organ and tissue system. The most common infections are NTM lung disease, local cutaneous disease, disseminated disease, surgical site infections and injection site abscesses. Most surgical site infections and injection site abscesses occur when the open wound is contaminated with tap water.Mortality is very rare, but death may come from extensive pulmonary or disseminated disease in immunocompromised patients. The morbidity ultimately depends on the site of infection. Localized skin lesions can heal without antibiotics or surgical excision. The average antibiotic treatment for all infections is six months. If no progress is made within six months, surgical excision of the lesion or removal of the device (ex. catheter) is required.
I became interested in the bacteria after reading about an outbreak in California. Over 115 people were infected with M. fortuitum after being exposed to it in whirlpool footbaths at a spa. Even though the footbaths were cleaned with bleach between each use, the water filter where the water entered the footbath was not cleaned, and the bacteria colonized behind it. Everyone developed lesions on their lower legs, some requiring antibiotics and excision and some not.
Another case occurred in Colorado. A family of five became deathly ill when they were exposed to large amounts of M. fortuitum in their hot tub. They did not change the water regularly, did not shower before entering after playing in the yard, and did not measure the pH level. Large colonies of M. fortuitum were found in the family’s lungs and the hot tub after they all were diagnosed with a NTM infection. They recovered fully about a year after given the correct treatment.
NTM infections are not required to be reported to the CDC, so there is no way of knowing how many cases occur in the U.S. each year. More cases are being reported after these incidences, and awareness is being raised.
References:
Albrecht et al. “Nontuberculous Mycobacterial Disease Following Hot Tub Exposure.” 30 Jan 2004. <www.cdc.gov/ncidod/eid/vol7no6/mangione.htm>
Desmond, Edward et al. “Mycobacteria in Nail Salon Whirlpool Footbaths, California.” <www.cdc.gov/ncidod/EID/vol11no04/04-0936.htm>
Gibson, Kevin, MD. “Tuberculosis and NonTuberculous Mycobacterial Infections.” <www.pitt.edu/~paccm/pdfs/airspacedisorders/tuberculosisandnontuberculousmycobacterialinfection.pdf>
Harris, Ron. “Dirty Footbaths at Nail Salon Blamed for Outbreak of boils.” 27 April 2001. <www.mindfully.org/Health/Mycobacterium-Fortuitum-Footbath.htm>
Woetje, Keith, MD, PhD. “Mycobacterium Fortuitum.” <www.emedecine.com/med/topic1534.htm>
*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
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