Listeria monocytogenes is a zoonotic food-borne pathogen that is associated with serious public health and economic implications. In animals, L. monocytogenes can be associated with clinical listeriosis, which is characterised by symptoms such as abortion, encephalitis and septicaemia. In human beings, listeriosis symptoms include encephalitis, septicaemia and meningitis. In addition, listeriosis may cause gastroenteric symptoms in human beings and still births or spontaneous abortions in pregnant women. In the last few years, a number of reported outbreaks and sporadic cases associated with consumption of contaminated meat and meat products with L. monocytogenes have increased in developing countries. A variety of virulence factors play a role in the pathogenicity of L. monocytogenes . This zoonotic pathogen can be diagnosed using both classical microbiological techniques and molecular-based methods. There is limited information about L. monocytogenes recovered from meat and meat products in African countries. This review strives to: (1) provide information on prevalence and control measures of L. monocytogenes along the meat value chain, (2) describe the epidemiology of L. monocytogenes (3) provide an overview of different methods for detection and typing of L. monocytogenes for epidemiological, regulatory and trading purposes and (4) discuss the pathogenicity, virulence traits and antimicrobial resistance profiles of L. monocytogenes .

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...

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.

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