Abstract:
INTRODUCTION : Mycobacterium avium complex (MAC) bacteria are the most
prominent etiological agents of lymphadenitis in pigs. M. avium subspecies
hominissuis (MAH) is a member of MAC and has been reported in many parts
of the world to be the most prevalent non-tuberculous mycobacteria (NTM)
to cause mycobacteriosis in humans, mainly in children. Thus, the economic
and zoonotic impact of MAC species are increasingly being recognized. In
South Africa, little is known about the distribution of NTM and the molecular
epidemiology of M. avium in pigs.
MATERIALS AND METHODS : In this study, lymph nodes including mandibular,
mesenteric, submandibular, and retropharyngeal, with tuberculosis-like lesions
were collected during routine meat inspection of slaughter pigs with no disease
symptoms (n = 132), between 1991 and 2002. These pigs were slaughtered
at 44 abattoirs distributed across seven of the nine South African provinces.
Mycobacterial culture, polymerase chain reaction (PCR), and sequencing of the
Mycobacterium specific 577 bp 16S rRNA gene fragment were performed for
species and subspecies identification.
RESULTS : The majority of the isolates (each per sample); 114 (86.4%) were
identified as MAH, 8 (6%) as MAA/M. avium subsp. silvaticum, 4 (3%) were
Mycobacterium tuberculosis, 2 (1.5%) as Mycobacterium intracellulare, and
1 (0.75%) as Mycobacterium bovis. The other isolates were identified as Mycobacterium lentiflavum (0.75%), Mycobacterium novocastrense (0.75%), and
a Micrococcus spp. (0.75%). Using an eight-marker MLVA typing tool, we
deciphered at least nine MIRU VNTR INMV types of MAH and MAA.
DISCUSSION : Identification of known zoonotic mycobacteria, including MAH, MAA,
M. intracellulare, M. bovis, and M. tuberculosis, from slaughter pigs has a potential public health impact and also strengthens recognition of the potential economic
impact of MAC. This study has also for the first time in South Africa, revealed
MAC MIRU VNTR INMV genotypes which will aid in the future epidemiological
investigation of MAC in South Africa.
