Mycobacterium Fortuitum

Updated: Nov 18, 2019
  • Author: Sami M Akram, MD, MHA, RDMS; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Overview

Background

Mycobacterium fortuitum is a rapidly growing nontuberculous mycobacterium (NTM), classified in the Runyon group IV. [1] Other mycobacteria in this group include Mycobacterium abscessus, Mycobacteria chelonae, and Mycobacteria peregrinum. M fortuitum was first isolated from frogs, explaining why it was formerly called Mycobacterium ranae. It is distributed worldwide and is found in soil and water. [2]

M fortuitum is isolated with increasing frequency from clinical samples. [2] At least 50 strains of M fortuitum exist. [3] The taxonomy of mycobacteria, including rapidly growing mycobacteria (RGM), is constantly evolving. Distribution is probably worldwide.

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Pathophysiology

M fortuitum infection can cause a wide spectrum of clinical syndromes, often based on the initial exposure. M fortuitum infection occurs in both immunocompetent and immunocompromised individuals.

Surgical or nonsurgical trauma and contaminated water introduce the organisms into the body; thereafter, M fortuitum establishes infection at these sites. Therefore, infections after cardiac, ophthalmologic, neurologic, [3] orthopedic, endoscopic, plastic, and reconstructive surgeries have been reported. For this reason, infections of implanted devices (eg, defibrillators, catheters, dialysis catheters) and injection-site abscesses can occur.

Pseudo-outbreaks after exposure to contaminated whirlpools in nail salons [4] and contaminated tattoo ink [5] have been reported.

M fortuitum can cause transient or chronic pulmonary infections, particularly in individuals with underlying structural defects and/or gastroesophageal abnormalities such as achalasia. [6]

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Epidemiology

Geographic Distribution

The epidemiological study of NTM infections is still in its infancy. NTM infections, including M fortuitum infections, occur globally.

Recently, epidemiological reports from Europe, North America, China, India, Africa, the Middle East, and Australia have been published.

To date, M fortuitum has no identifiable endemic areas.

Age-, Sex-, and Race-Based Incidence

Patients who develop M fortuitum infection related to plastic and reconstructive surgery tend to be younger (in the mid-fourth decade of life [7] ), while patients with pulmonary M fortuitum infection tend to be older (>50 years [8] ). Lung disease in a younger patient (< 50 years) strongly suggests a primary underlying lung disorder. Isolated lymphadenitis primarily occurs in children. M fortuitum infections do not appear to have a sexual or racial predilection.

Frequency

NTM infections are not required to be reported; therefore, exact estimates of disease prevalence and incidence are difficult to determine. Sputum is most frequently examined for acid-fast bacilli (AFB) so is easiest to track. In one study, of the 6,800 patients tested for AFB, 40 had M fortuitum lung disease. [8] In a study of Kaiser Permanente patients in Hawaii, 109 of 2,197 (4.9%) respiratory specimen cultures were positive for M fortuitum. [9] Rapidly growing NTM were more frequently isolated in medical tourists, who developed postoperative wound infections. M abscesses is the most prevalent isolate, followed by M fortuitum. [10]

Mortality/Morbidity

Mortality due to localized M fortuitum infection is rare. Death may result from extensive pulmonary or disseminated disease in immunocompromised patients.

Morbidity depends largely on the site of the infection. Localized skin lesions may eventually heal without therapy or surgical intervention. At other sites, chronic infection is the rule.

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Prognosis

The prognosis of M fortuitum infection is very good for most sites of infection if debridement is performed and appropriate antibiotic therapy administered, particularly if more than one antibiotic is used, including a quinolone.

Lung disease may be difficult or impossible to eradicate. Chronic suppression of the infection and slowing of the progression of lung disease may be the only achievable goal in this setting.

Cure of infected implants that cannot be removed may be impossible.

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Patient Education

Medical tourists have developed chronic NTM infections (particularly rapidly growing mycobacteria) of surgical sites, breast prostheses, and injection sites. Tap water may be contaminated with mycobacteria, which are resistant to disinfecting procedures, so may be present even in treated water.

Multidrug therapy is necessary to successfully treat mycobacterial infections. Frequently, two or three antibiotics are needed. The success rate of antibiotic monotherapy is dismal, so it is important that patients adhere to the prescribed antibiotic regimen.

Patients may confuse the disease with tuberculosis and need to be reassured that they are not contagious to others.

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