Cervical lymphadenitis is the main manifestation of Mycobacterium avium infection in immunocompetent children. Exposure to birds has been discussed as a source of infection. To clarify from where children acquire the infection, M. avium isolates from different origins were analysed with restriction fragment length polymorphism (RFLP) on insertion sequence IS1245, and compared by computer cluster correlation analysis. This molecular epidemiological tool has previously revealed a distinction between multiband profiles found mainly in strains from humans, and a 3-band/bird type profile in strains isolated mainly from birds. 32 isolates from children were compared with 28 isolates from adults and 45 isolates from animals. We found that 67% of the animal isolates had the bird type profile, also found in 1 sputum isolate from an adult. Strains from children showed only multiband profiles that did not differ significantly from profiles of isolates from adults. All but 2 bird isolates showed the bird type profile. Neither of the remaining 2, which had multiband profiles, clustered with the isolates from children. Our results indicate that the true reservoir of M. avium. is unknown. Thus the question of whether or not M. avium can be incriminated as a zoonotic disease remains unanswered. © 2005 Taylor & Francis.

We studied Mycobacterium avium lymphadenopathy in 183 Swedish children (<7 years of age) from 1998 through 2003. Seasonal variation in the frequency of the disease, with a peak in October and a low point in April, suggests cyclic environmental factors. We also found a higher incidence of the disease in children who live close to water.

Mycobacterium avium is the most common pathogen in children presenting as non-tuberculous mycobacterial lymphadenitis. In Sweden non-tuberculous mycobacterial infection is a notifiable disease. The goal of our study was to determine the annual incidence of M. avium infection in Swedish children, 1998-2003, and describe clinical features related to age and treatment of children with M. avium lymphadenitis. To do this, we retrospectively analysed patient records of 162 children less than 7 y of age from the entire country with culture-verified M. avium disease. The incidence of M. avium infection in Sweden was lower in 2000-2003 than in 1998-1999. Young children (≤24 months old) had more constitutional symptoms at onset of disease than older children. One-third of the children had received 2 or more antibiotic courses before diagnosis. Disfiguring scars after healing were more common in children who were not treated with surgical extirpation of the affected lymph nodes. The decreasing incidence of M. avium infection among Swedish children in recent y is in contrast to reports of increasing non-tuberculous mycobacterial disease from other countries. Our results support the view that M. avium lymphadenitis should be treated by surgical removal of the affected tissue.

Background: Mycobacterium avium is the principal etiologic agent of non-tuberculous lymphadenitis in children. It is also a known pathogen for birds and other animals. Molecular epidemiologic evidence indicates that humans and animals are infected with different M. avium subspecies, namely, M. avium subsp. avium and M. avium subsp. hominissuis, respectively.

Aim: To investigate the effect on the human immune system of 10 isolates of M. avium subsp. avium mainly isolated from animals and of 11 isolates of M. avium subsp. hominissuis isolated from children with lymphadenitis.

Method: Peripheral blood mononuclear cells (PBMC) from six healthy blood donors were stimulated in vitro with the inactivated mycobacteria followed by quantification of IL-10, IL-12p70, TNF, IFN-γ and IL-17 in supernatants by multiplex bead array analysis (Luminex).

Results: M. avium subsp. hominissuis induced significantly more IL-10 and significantly less IL-12p70, TNF, IFN-γ and IL-17 compared to M. avium subsp. avium. All strains induced high levels of IL-17, but very little IL-12.

Conclusion: The lower T helper (Th) 1 and Th17 responses induced by M. avium subsp. hominissuis compared to M. avium subsp. avium after in vitro stimulation of PBMC might contribute to its higher pathogenicity in humans.