Abstract:
In this study, Listeria isolates (214) were characterized as follows: L. innocua (77.10%),
L. monocytogenes (11.21%), L. welshimeri (5.61%), L. grayi (1.40%), L. seeligeri (0.93%), and L. species
(3.73%) that were not identified at the species level, from beef and beef based products from retail
and farms in Mpumalanga and North West provinces of South Africa. MLVA was further used
to type Listeria innocua isolates (165) and Listeria monocytogenes isolates (24). The L. monocytogenes
isolates were also serogrouped using PCR. The MLVA protocol for L. monocytogenes typing included
six tandem repeat primer sets, and the MLVA protocol for L. innocua included the use of three tandem
repeats primer sets. The L. monocytogenes serogroups were determined as follows: 4b-4d-4e (IVb)
(37.50%), 1/2a-3a (IIa) (29.16%), 1/2b-3b (IIb) (12.50%), 1/2c-3c (IIc) (8.33%), and IVb-1 (4.16%). MLVA
could cluster isolates belonging to each specie, L. monocytogenes, and L. innocua isolates, into MLVArelated
strains. There were 34 and 10 MLVA types obtained from the MLVA typing of L. innocua
and L. monocytogenes, respectively. MLVA clustered the L. monocytogenes isolates irrespective of
sample category, serogroups, and geographical origin. Similarly, the L. innocua isolates clustered
irrespective of meat category and geographical origin. MLVA was able to cluster isolates based
on MLVA relatedness. The clustering of isolates from farms and retailers indicates transmission of
Listeria spp. MLVA is an affordable, simple, and discriminatory method that can be used routinely to
type L. monocytogenes and L. innocua isolates.
