Listeria monocytogenes is a dangerous and sometimes fatal Listeria infection that may be transmitted through contaminated soil or water.
Listeria monocytogenes, a deadly bacteria commonly found in the food processing industry, is a serious threat to human health. It can also be harmful to human health because it is becoming resistant to food safety precautions around the world.
Two previously thought to be harmless Listeria strains have recently been discovered to be harmful to humans.
Listeria found in South Africa is being studied by a team of researchers led by Dr. Thendo Mafuna of the University of Johannesburg.
Listeria innocua strains are evolving to deal with temperature, pH, dehydration, and other stresses, as well as having a genetic equivalent to Listeria monocytogenes.
Listeria innocua and L. welshimeri, a food-borne pathogen, are often regarded as harmless, compared to deadly Listeria monocytogenes. However, both species are developing unexpectedly harmful characteristics that may make food safety measures more difficult to maintain, according to a Whole Genome Sequencing study from South Africa.
The quaternary ammonium compound (QAC or QUAT) group of chemicals includes three strains of L. innocua and L. welshimeri.
Two strains of L. innocua they studied have three or more important pathogenic characteristics, including CRISPR CAS adaptive immune systems.
Listeria strains 2 and 2 were detected in raw, dried, and processed meats at commercial food processing plants in the United States.
The study contradicts other studies that show that Listeria species are increasing in other parts of the world.
Dr. Thendo Mafuna, from the University of Johannesburg's Biochemistry Department, claims that the Listeria innocua we studied has some of the genes that are also found in pathogenic Listeria monocytogenes.
These shared genes between L. innocua and L. monocytogenes are also responsible for illness in humans, as well as stress tolerance, such as resistance to the disinfectant Benzalkonium chloride (BC or BAC).
Dr. Thendo Mafuna from the University of Johannesburg's Biochemistry Department is in a biochemistry lab and facing genetic data for Listeria innocua, according to Therese van Wyk, University of Johannesburg.
L. innocua is rarely found in people who have trouble with their immune systems, according to previous research.
Benzalkonium chloride (BAC) is a member of a group of compounds called Quaternary ammonium compounds, or QUATs, which are used in many common disinfectant medications. Quats have been shown to be extremely effective at killing bacteria, fungi, and viruses.
The entire LIPI-4 hypervirulence gene sequence they found in L. innocua was also found at the Pasteur Institute in Paris, France.
The samples and isolates used in this investigation were collected from the South African Government's Department of Agriculture, Land Reform, and Rural Development (DALRRD). These were submitted to the Agricultural Research Council (ARC) at Onderstepoort Veterinary Research SA for analysis.
258 isolates from butcheries, abbatoirs, retail outlets, cold shops, and processing facilities around the country have been investigated; 38 of these have been identified as nonpathogenic L. Innocua; three additional three have been identified as nonpathogenic L. welshimeri.
Listeria isolation and identification was performed by Dr. Itumeleng Matle at the ARC in Onderstepoort.
Dr. Rian E. Pierneef of the ARC's Biotechnology Platform at Onderstepoort performed the Whole Genome Sequencing (WGS).
Mafuna then compared the genome sequences to those recorded by the Pasteur Institute in Paris, France, and performed the analysis for the research.
"To really see what's going on in South Africa, we need to look at our own facilities." Mafuna believes that our investigations of these bacteria will help us identify which sequence types to look out for.
The number of detrimental qualities that the L. innocua strains have compared to L. monocytogenes is concerning, according to the researcher.
Listeria innocua is becoming resistant to disinfectants that are used in industry to get rid of them, according to the researcher. It is also helpful to apply different disinfectants to surfaces, such as bleaching.
"Big industrial food processors may want to check on how effective BC or quat disinfectants are in their facilities," says Mafuna. This can be done by taking swabs before cleaning and again after cleaning, culturing them, to see how well the disinfectant regimes are working.
T. Mafuna, I. Matle, K. Magwedere, R. E. Pierneef, and O. N. Reva, 6 September 2022, Microbiology Spectrum, DOI: 10.1128/spectrum.01189-22
The South African Department of Agriculture, Land Reform, and Rural Development (DALRRD) provided funding for this study.
The DALRRD Directorate: Veterinary Public Health conducted sample testing and DNA isolation at the ARC Biotechnology Platform. Dr. Thendo Mafuna is a doctoral student at the University of Pretoria.