A comparative study on the occurrence, risk factors, and genetic characteristics of Listeria species recovered  from cattle farms, and beef abattoirs in Gauteng Province, South Africa

Abstract

These cross-sectional reported the occurrence, risk factors, and genetic characteristics of Listeria species recovered from cattle farms and beef abattoirs in Gauteng Province, South Africa. A total of 328 samples collected from 23 cattle farms and 262 samples from 8 beef abattoirs were processed using standard bacteriological and molecular methods to detect Listeria spp. The factors associated with the prevalence of Listeria spp. were investigated, and multiplex polymerase chain reaction (mPCR) was used to determine Listeria species, the pathogenic serogroups, and carriage of eight virulence-associated genes by Listeria monocytogenes. The overall prevalence of Listeria spp. in cattle farms was 14.6%, comprising Listeria innocua (11.3%), Listeria monocytogenes (3.4%), Listeria welshimeri (0.0%) compared with 11.1%, comprising Listeria innocua (5.7%), Listeria monocytogenes (4.6%), Listeria welshimeri (0.8%) for beef abattoirs. Of the three variables (area, type of farm/abattoir, and sample type) investigated, only the sample types at abattoirs had a significant (P < 0.001) effect on the prevalence of L. innocua and L. welshimeri. The frequency of distribution of the serogroups based on 11 L. monocytogenes isolated from farms was 72.7% and 27.3% for the serogroup 1/2a-3a and 4b-4d-4e, respectively, while for the 12 L. monocytogenes isolates recovered from abattoirs, it was 25%, 8.3%, 50% and 16.7% for the serogroup 1/2a-3a, 1/2b-3b, 1/2c-3c, and 4b-4d-4e respectively (P < 0.05). All (100.0%) isolates of L. monocytogenes from the farms and abattoirs were positive for seven virulence genes (hlyA, inlB, plcA, iap, inlA, inlC, and inlJ). The clinical and food safety significance of the findings cannot be ignored.

Detection of Pathogenic Serogroups and Virulence Genes in Listeria monocytogenes Strains Isolated from Beef and Beef Products Retailed in Gauteng Province, South Africa, Using Phenotypic and Polymerase Chain Reaction (PCR)-Based Methods

“…Of potential virulence and pathogenicity importance is the detection that all (100%) of the isolates of L. monocytogenes assessed in the current study were positive for seven of the virulence-associated genes, which included the genes encoding specific virulence factors, specifically, internalins ( inlA, inlB, inlC, inlJ ), hemolysin ( hlyA) , phospholipase ( plcA ), and actin polymerization ( actA ) in 97.3% of the isolates. Similar findings were reported in a nationwide study on meat and meat products [ 10 ] and isolates recovered from cattle farms and cattle abattoirs [ 10 , 74 ]. However, diversity has been reported in the detection of the virulence genes in L. monocytogenes recovered from meat and meat products in the literature, such as hlyA, prfA, and inlA in Chile [ 75 ], inlC, and inlJ in China [ 76 ], and hlyA , actA , inlA, inlB, inlC, inlJ , prfA , plcA , and iap in Turkey and Norway [ 77 , 78 ].…”

Genomic Characterization of Listeria innocua Isolates Recovered from Cattle Farms, Beef Abattoirs, and Retail Outlets in Gauteng Province, South Africa

“…Therefore, there is a potential for tetracycline-resistant L. innocua strains to enter the human food chain. It is relevant to mention that the prevalence of phenotypic tetracycline resistance exhibited by the same isolates of L. innocua using the disc diffusion method was 36.8% [37]. Interestingly, this phenotypic resistance correlates well with the putative resistance to tetracycline due to both the tet(M) and tet(S) genes, suggesting that the genes may have been partly responsible for the resistance detected.…”

“…The isolates of L. innocua subjected to WGS in the current study originated from an earlier study. Details on the types and number of samples collected from the sources mentioned earlier and the types of samples in the current study have been documented [37].…”

Whole Genome Sequence Analysis of <em>Listeria monocytogenes</em> Isolates Recovered from Cattle Farms, Cattle Abattoirs, and Retail Outlets in Gauteng Province, South Africa

“…Sixty isolates of L. monocytogenes on which WGS and bioinformatics analyses were performed in the current study were recovered from cattle farms, cattle abattoirs, and retail outlets in Gauteng province. A detailed description of the isolates regarding the sources and types of samples processed has been provided in an earlier study [57].…”

“…The isolates of L. monocytogenes stored at -80 o C were confirmed using standard bacteriological and molecular (multiplex PCR) techniques [56,57]. There were 60 isolates of L. monocytogenes comprising 11, 12, and 37 isolates originating from cattle farms, cattle abattoirs, and retail outlets, respectively studied.…”