Isolation of mycobacteria other than Mycobacterium avium from porcine lymph nodes

Mycobacterium avium causes lymphadenitis in pigs. This presents an economical burden, as these pigs meat is considered inappropriate for consumption. In humans, lymphadenitis due to nontuberculous mycobacteria (NTM) primarily affects children and is caused by a variety of NTM, though M. avium predominates. Mycobacterial culture was undertaken on lymph nodes of 107 slaughter pigs from a single pig farm. A high number of pigs with mycobacterial lymphadenitis were identified by culture. A commercial line probe assay and 16S rDNA gene sequencing were used to assess the frequency of disease due to mycobacteria other than M. avium. Forty-five pigs had mandibular lymph node samples yielding mycobacteria in culture. The majority yielded M. avium (39; 87%) only. One yielded M. avium and Mycobacterium palustre, five yielded only NTM other than M. avium (2yielded Mycobacterium malmoense, 1Mycobacterium bohemicum, 1Mycobacterium heckeshornense and a possibly novel species related to Mycobacterium scrofulaceum, and 1 grew a possibly novel species related to M. palustre). Several NTM species other than M. avium were cultured from porcine lymph nodes. The species distribution shows interesting parallels with human NTM lymphadenitis. Molecular typing and environmental sampling studies are required to identify the sources of these infections.