Basics
Description
Nontuberculous mycobacteria (NTMB) are mycobacteria other than the Mycobacterium tuberculosis complex bacteria (M. tuberculosis, Mycobacterium africanum, Mycobacterium bovis, Mycobacterium canetti, and Mycobacterium microti) or Mycobacterium leprae capable of causing disease in humans. ‚
- NTMB are classified based on growth rate in culture media as "rapid " ť or "slow " ť growers.
- Disease from these infections most commonly presents as cervical lymphadenitis in children.
Epidemiology
- NTMB are ubiquitous in nature and found in soil, food, water, and animals.
- More than 120 species of mycobacteria have been identified.
- Each species has a different level of virulence and many species are associated with specific reservoirs or geographic areas. For example, Mycobacterium marinum is found in fish tanks and Mycobacterium malmoense is found in Northern Europe.
- Health care " “related infections can occur, typically due to rapid-growing Mycobacterium abscessus or Mycobacterium fortuitum.
- Tap water is a major reservoir for a number of NTMB.
Risk Factors
- Cystic fibrosis
- Immune deficiency especially HIV
- Tympanostomy tubes
- Foreign bodies or medical hardware
- Interleukin-12 receptor deficiency
Pathophysiology
- Rapid growers include the M. fortuitum and Mycobacterium chelonae/abscessus groups. These rapid growers show significant growth on culture media in 3 " “7 days.
- Slow-growing mycobacteria take more than 7 days and typically 4 " “6 weeks to grow in culture.
- Dirty wounds and breaks in oral, respiratory, or gastrointestinal mucosa are the common portals of entry.
- Infection is usually localized near the inoculation site and related regional lymph nodes.
- No evidence of person-to-person spread
Etiology
- Cervical adenitis is the most common presentation in children 1 " “5 years of age. In the United States, 80% of these cases are due to Mycobacterium avium-intracellulare (MAI).
- In healthy adults, pulmonary disease is the most common illness, typically caused by MAI, Mycobacterium kansasii, Mycobacterium xenopi, or M. malmoense.
- Other presentations may include skin and soft tissue infections, bone and joint infections, chronic ear infections, catheter-associated infections, and pneumonia.
- Disseminated disease is seen primarily with MAI in patients with advanced HIV.
Diagnosis
History
- Travel history and area of residence
- Fever history and systemic complaints
- Length of symptoms " ”longer history is characteristic.
- Water and animal exposures
- Trauma history
- Recent surgery or hardware
Physical Exam
- Lymphadenitis is typically unilateral, minimally tender, anterior cervical, or submandibular.
- Skin disease is usually an ulcer, a localized cellulitis, a draining abscess, or a persistent nodule.
- Pulmonary disease may be associated with fever, weight loss, and fatigue.
- Mediastinal and hilar lymphadenopathy is common.
- Lung findings are nonspecific.
- Otitis media in children with tympanostomy tubes presents with chronic drainage unresponsive to antibiotics.
- Disseminated disease is rare; findings include fever, night sweats, abdominal pain, and wasting.
Diagnostic Tests & Interpretation
- Definitive diagnosis requires isolation of NTMB in culture.
- Special media and laboratory facilities are required.
- Contamination of nonsterile sites can occur and may require 2 or more cultures to confirm diagnosis.
- Any growth from a draining wound is clinically significant.
- A tuberculin skin test may be positive as cross-reactivity occurs but is not diagnostic.
- PCR for identification of specific NTMB is becoming more readily available and may facilitate quicker diagnosis.
Differential Diagnosis
- M. tuberculosis complex
- Dimorphic fungi: Histoplasma capsulatum, Coccidioides species, Blastomyces dermatitidis, Sporothrix schenckii
- Malignancy typically leukemia/lymphoma
- Bartonella henselae: cat-scratch disease
- Viral or bacterial adenitis
Treatment
Treatment is variable depending on the site of infection and the specific mycobacterium isolated. In general, complete surgical excision of infected lymph nodes is curative. ‚
Medication
- MAI is treated orally with a macrolide (clarithromycin or azithromycin) plus ethambutol or rifampin. Azithromycin is used as prophylaxis in patients with AIDS.
- Other slow growers such as M. kansasii, M. marinum, and Mycobacterium ulcerans are treated with rifampin-based regimens in combination with ethambutol, macrolides, trimethoprim-sulfamethoxazole, doxycycline, and/or aminoglycosides.
- For rapid growers (M. fortuitum, M. abscessus, and M. chelonae), serious diseases are treated intravenously with an aminoglycoside plus meropenem or cefoxitin depending on susceptibilities. Milder disease or subsequent oral therapy is treated with clarithromycin, doxycycline, trimethoprim-sulfamethoxazole, or ciprofloxacin based on susceptibility testing.
- Combination therapy is indicated in immunocompromised hosts.
Surgery/Other Procedures
- Isolated lymphadenitis is treated with complete surgical excision. Typically, antimicrobials are not beneficial in this situation.
- Any infected hardware should be removed and serious localized disease debrided.
Ongoing Care
Follow-up Recommendations
- Medical treatment is typically for a minimum of 3 " “6 months.
- Follow-up should last 1 year after completion of therapy.
Patient Education
- Chemoprophylaxis for patients with CD4 count <50 cells/uL
- Avoid tap water contamination of central lines.
Prognosis
- For localized disease and adenitis, prognosis is excellent.
Complications
- Chronic draining wounds can occur and treatment is typically long-term antimicrobials in combination with surgical debridement.
- Disseminated disease " ”occurs in immunocompromised patients
Additional Reading
- Cruz ‚ AT, Ong ‚ LT, Starke ‚ JR. Mycobacterial infections in Texas children. Pediatr Infect Dis. 2010;29(8):772 " “774. ‚ [View Abstract]
- Hazra ‚ R, Robson ‚ CD, Perez-Atayde ‚ AR, et al. Lymphadenitis due to nontuberculous mycobacteria in children: presentation and response to therapy. Clin Infect Dis. 1999;28(1):123 " “129. ‚ [View Abstract]
- Lee ‚ WJ, Kang ‚ SM, Sung ‚ H, et al. Non-tuberculous mycobacterial infections of the skin: a retrospective study of 29 cases. J Dermatol. 2010;37(11):965 " “972. ‚ [View Abstract]
- Lindeboom ‚ JA, Kuijper ‚ EJ, Bruijnesteijn van Coppenraet ‚ ES, et al. Surgical excision versus antibiotic treatment for nontuberculous mycobacterial cervicofacial lymphadenitis in children: a multicenter, randomized, controlled trial. Clin Infect Dis. 2007;44(8):1057 " “1064. ‚ [View Abstract]
- Starke ‚ JR. Management of nontuberculous mycobacterial cervical adenitis. Pediatr Infect Dis J. 2000;19(7):674 " “675. ‚ [View Abstract]
Codes
ICD09
- 031.9 Unspecified diseases due to mycobacteria
- 031.1 Cutaneous diseases due to other mycobacteria
- 031.8 Other specified mycobacterial diseases
- 031.0 Pulmonary diseases due to other mycobacteria
- 031.2 Disseminated due to other mycobacteria
ICD10
- A31.9 Mycobacterial infection, unspecified
- A31.1 Cutaneous mycobacterial infection
- A31.8 Other mycobacterial infections
- A31.0 Pulmonary mycobacterial infection
- A31.2 Dissem mycobacterium avium-intracellulare complex (DMAC)
SNOMED
- 111812000 Atypical mycobacterial infection (disorder)
- 240415007 Skin and soft tissue atypical mycobacterial infection (disorder)
- 234091000 Atypical mycobacterial lymphadenitis (disorder)
- 1731000119106 Atypical mycobacterial infection of lung (disorder)
- 240413000 Disseminated atypical mycobacterial infection (disorder)
FAQ
- Q: When should I worry about NTMB?
- A: NTMB should be on the differential for any child with persistent lymphadenitis or a chronically draining wound.
- Q: When should NTMB be considered as a cause of lymphadenitis?
- A: Most lymphadenitis is due to an acute viral or bacterial infection and will improve with time or respond to a short course of antibiotics. NTMB should be suspected in a healthy toddler (age 1 " “5 years) who presents with a subacute or chronic lymphadenitis. Other considerations should include cat-scratch disease, malignancy, and tuberculosis.
- Q: If infected node is excised, should I treat with antibiotics?
- A: Surgical excision is the treatment of choice of NTMB adenitis. Most studies show that antibiotics are not beneficial after complete surgical excision.