Listeria monocytogenes is an intracellular pathogen that causes life-threatening disease called listeriosis. However, in South Africa (SA), there is a dearth of information concerning the potential role of meat and meat products as potential sources for human listeriosis. The aim of the study was to determine the occurrence and level of L. monocytogenes found in meat and meat products in SA and to characterize L. monocytogenes strains according to serogroups, antimicrobial resistance profiles and virulence genes. A total of 2,017 samples from imported and locally produced raw, processed and ready to eat meat were collected from 2014 to 2016 across nine provinces of SA. The samples for L. monocytogenes were isolated using microbiological techniques and real-time polymerase chain reaction (PCR). Antimicrobial resistance profiles of the isolates were determined by testing 19 antimicrobial impregnated discs using Kirby-Bauer disc diffusion method. Characterization in terms of serogroup typing and virulence profiling was done using conventional PCR. The overall occurrence of L. monocytogenes was 14.7% (296/2,017), which varied between meat collected on the domestic market (15.0%; 264/1,758) and directly at the three ports of entries (12.4%; 32/259). The contamination level of the positive samples ranged from 1 to 3.7 log CFU/g and 1 to 4.1 log CFU/g for samples collected from the domestic and imported meat, respectively. All positive isolates were serotyped by multiplex PCR, of which majority of the isolates belonged to molecular serogroup ½a-3a (45.5%), followed by 4b-4d-4e (24.2%), and ½c-3c (15.2%). Most of the isolates harbored the inlJ (98.7%) and ipa (95.6%) genes. However, at least one of the other internalin genes (inlB, inlC, and inlA) was present in most of the isolates. All the tested isolates showed resistance to at least 3 of the 19 antibiotics, with 5 (1.7%) of them displaying resistance to 13 of the 19 antibiotics. Resistance to streptomycin (99.0%), clindamycin (97.3%), fusidic acids (95.6%), nitrofurantoin (79.7%), and gentamycin (74.4%) was observed while high rates of sensitivity were observed for ampicillin (85.6%), kanamycin (84.6%), amikacin (77.6%), vancomycin (74.2%), and tetracycline (62.5%).The presence of L. monocytogenes in various meat products in SA pose a risk to human health. Therefore, the present research provides valuable baseline information that will help in the development of policies and regulations for monitoring of L. monocytogenes in meat and meat products in SA. Practical applicationsThis study is extensive and involved analysis of meat and meat products from all the nine provinces of South Africa. Furthermore, the study involved analysis of imported meat (from the three major ports of entry) that was destined for the South African market. The findings that were obtained are significant from academic, policy, and practical points of view. The findings provide empirical evidence of the contamination of a proportion of raw intact, raw processed, and ready-to-eat meat and produc...

Listeria monocytogenes is an important foodborne pathogen which has the ability to adapt and survive in food and food processing facilities where it can persist for years. In this study, a total of 143 L. monocytogenes isolates in South Africa (SA) were characterized for their strain’s genetic relatedness, virulence profiles, stress tolerance and resistance genes associated with L. monocytogenes. The Core Genome Multilocus Sequence Typing (cgMLST) analysis revealed that the most frequent serogroups were IVb and IIa; Sequence Types (ST) were ST204, ST2, and ST1; and Clonal Complexes (CC) were CC204, CC1, and CC2. Examination of genes involved in adaptation and survival of L. monocytogenes in SA showed that ST1, ST2, ST121, ST204, and ST321 are well adapted in food processing environments due to the significant over-representation of Benzalkonium chloride (BC) resistance genes (bcrABC cassette, ermC, mdrL and Ide), stress tolerance genes (SSI-1 and SSI-2), Prophage (φ) profiles (LP_101, vB LmoS 188, vB_LmoS_293, and B054 phage), plasmids profiles (N1-011A, J1776, and pLM5578) and biofilm formation associated genes. Furthermore, the L. monocytogenes strains that showed hyper-virulent potential were ST1, ST2 and ST204, and hypo-virulent were ST121 and ST321 because of the presence and absence of major virulence factors such as LIPI-1, LIPI-3, LIPI-4 and the internalin gene family members including inlABCEFJ. The information provided in this study revealed that hyper-virulent strains ST1, ST2, and ST204 could present a major public health risk due to their association with meat products and food processing environments in SA.

Meat products have been implicated in many listeriosis outbreaks globally, however there is a dearth of information on the diversity of L. monocytogenes isolates circulating in food products in South Africa. The aim of this study was to investigate the population structure of L. monocytogenes isolated in the meat value chain within the South African market. Based on whole-genome sequence analysis, a total of 217 isolates were classified into two main lineage groupings namely lineages I (n = 97; 44.7%) and II (n = 120; 55.3%). The lineage groups were further differentiated into IIa (n = 95, 43.8%), IVb (n = 69, 31.8%), IIb (n = 28, 12.9%), and IIc (n = 25, 11.5%) sero-groups. The most abundant sequence types (STs) were ST204 (n = 32, 14.7%), ST2 (n = 30, 13.8%), ST1 (n = 25, 11.5%), ST9 (n = 24, 11.1%), and ST321 (n = 21, 9.7%). In addition, 14 clonal complex (CCs) were identified with over-representation of CC1, CC3, and CC121 in “Processed Meat-Beef”, “RTE-Poultry”, and “Raw-Lamb” meat categories, respectively. Listeria pathogenic islands were present in 7.4% (LIPI-1), 21.7% (LIPI-3), and 1.8% (LIPI-4) of the isolates. Mutation leading to premature stop codons was detected in inlA virulence genes across isolates identified as ST121 and ST321. The findings of this study demonstrated a high-level of genomic diversity among L. monocytogenes isolates recovered across the meat value chain control points in South Africa.

Zoonoses are a worldwide public health concern, accounting for approximately 75% of human infectious diseases. In addition, zoonoses adversely affect agricultural production and wildlife. We review some mathematical models developed for the study of viral zoonoses in wildlife and identify areas where further modeling efforts are needed.

We describe the frequent isolation of Salmonella of a wide variety of serovars, from an array of animal feeds, food animals, and food animal environment. As prevention of human salmonellosis requires the effective control of Salmonella in food animals, these data can be used to facilitate Salmonella control in food animals and thereby prevent human infections.