The incubation period for L. Listeriosis is a human illness characterized by flu-like symptoms including fever, muscle aches and, sometimes, gastrointestinal symptoms. If infection spreads to the nervous system, symptoms may progress to include severe headache, stiff neck, confusion, loss of balance or convulsions.
Once contracted, the symptoms of listeriosis can last for several days. Diagnosis requires laboratory analysis of blood or cerebrospinal fluid. Treatment is administered through antibiotics like penicillin or ampicillin.
Healthy adults and children can become infected, but rarely become seriously ill. Pregnant women may experience only mild flu-like symptoms, but infection during pregnancy can transfer to newborns or lead to premature delivery, miscarriage or stillbirth. According to the Centers for Disease Control and Prevention CDC , pregnant women are 20 times more likely to contract listeriosis and account for about one-third of reported cases.
In such instances, usually the unborn child suffers the most serious effects. Since , the L. Neighbor-joining tree of L. The neighbor joining tree shows the relatedness of the 64 L. The phylogenetic tree was constructed with sequences of the antibiotic-resistant genes Figure 4. The strains belonging to clade A were further classified into two branches comprising different ST isolates.
Interestingly, each ST strain was clustered within the same group and harbored the same antibiotic-resistant genes Figure 4.
Importantly, fosfomycin resistant genes fosX , lincosamide resistant gene lnu , and multiple peptide resistant gene mprF , were present in all the isolates. The ST strains were divided into two groups, except for the three antibiotic-resistant genes mentioned above, one group carried the tetracycline-resistance gene tetM , and the other carried tetM and gene-encoded dihydrofolate reductase dhfR , our study was the first report on ST carrying dhfR.
Isolates presenting high resistances to fosfomycin have been reported in various countries Harakeh et al.
Notably, Scortti et al. Moreno et al. Considering the intricate characteristics of intrinsic and acquired antibiotic resistance, it is significant to determine the antibiotic phenotype and mechanism of these isolates. Figure 4. Resistance genes profile. Left Maximum likelihood phylogenetic tree based on the antibiotic-resistant genes. Right Patterns of antibiotic-resistant gene presence colored line or absence white.
The right column corresponds to the sequence type. In this study, a total of 64 L. The proportions of these isolates within lineages I and II were Figure 5. Virulence profiles across the phylogeny of the L. Left Phylogenetic tree of all isolates determined by 59 virulent and virulence-related genes, part of genes belong.
The phylogenic relationship among different STs is shown by the phylogenic tree. Right Pattern of gene presence colored line or absence white. To investigate the virulence potentials of the 64 isolates, an in silico detection of 91 virulent and virulence-related genes was carried out, main virulent genes in each isolate were presented in Figure 5.
Parts of the ST strains did not contain ami and aut. Virulent and virulence-associated genes are widely distributed in 64 isolates, particularly the ST strains, indicating high virulence features and potential high risk to humans. A part of the isolates from different supermarket chains showed high genetic similarity 0—50 SNP differences.
Because the pork meats of these 3 supermarket chains were supplied by the same slaughterhouse A, it suggested that the contamination of pork was possibly sourced from the same production chain. Additionally, the isolates were from different supermarket chains and collection times, but the SNP differences were less than two. For example, despite the temporal half year gap and geographical differences among the isolates, Lm, Lm, Lm, and Lm indicated the persistence of specific L.
Therefore, various diversity of the strains was possibly due to the intricate supply chain. This represented a public health concern because of their potential to transfer to humans via the food chain. Figure 6. Strains labeled with light blue color are foreign clinical isolates.
Strains labeled with red color are clinical isolates from China. The right column shows the CCs corresponding to the branches of the phylogenetic tree.
The words after the names of the isolates are the isolation times and supermarket chains. The uppercase letters are the abbreviations of the supermarket chains. Right Neighbor-joining tree of L. The neighbor-joining tree shows the relatedness of the 64 L. Other STs only carried Cas10 protein or one to four Cas3 proteins, particularly of carrying limited spacers between 0 and 10 Table 2.
Figure 7. The diversity of the CRISPR-Cas system indicates the role of various functions in the corresponding strains, which are possibly related to different STs encountered in distinct environments. In brief, these results verify that the organization of the CRISPR-Cas system exhibits genetic diversity of isolates, thereby reflecting the higher discrimination ability. Listeria monocytogenes is a severe foodborne pathogen and is a significant threat to public health.
Animal-derived Listeria -contaminated food is generally understood to be the main cause of listeriosis outbreaks de Valk et al. Therefore, improving the detection of bacterial contamination of pork, beef and poultry is an efficient measure to prevent human listeriosis. Genome sequencing has been gradually used to reveal the detailed characteristics of typing, virulent, and antibiotic-resistant genes and has become a useful investigation tool to support public health Halbedel et al.
The cgMLST and SNP have the advantage of high discriminatory power and are widely used for surveillance by appropriate public health analysts and epidemiologists Hurley et al. It was observed that isolates from clinical sporadic and outbreak cases could be clustered together with the pork isolates obtained in this study as they had close relationships, which was reflected in the SNP differences.
Furthermore, they indicated that pork isolates have a potentially high risk of causing human listeriosis along the food chain. CRISPR-Cas systems are adaptive immunity systems in many prokaryotic microorganisms; they confer defense capabilities against horizontal gene transfer elements and display variations in different species Marraffini, ; Koonin et al.
CRISPR-based genotyping applications have been exploited for some species, which have been classified into 2 classes, 6 types, and 33 subtypes Makarova et al. In the case of Salmonella enterica serovar Typhimurium, the profile of spacer arrangements has strong association with strain phylogeny Xie et al.
However, its application to L. Importantly, L. Understanding the structure and function of CRISPR-Cas system contributes to develop useful technology and products to control pathogen, i. Listeria monocytogenes carrying different virulence factors are highly heterogeneous distributions between CCs and lineages Tavares et al.
The four known Listeria pathogenicity islands play vital roles in L. Maury et al. Whereas, sporadic listeriosis is the primary feature of clinical cases recorded in China, the CCs , -8, -9, , , and were present in human clinical cases Li et al. In this study, none of CC87 strains were isolated, while a unique clonal complex CC isolates carrying LIPI-1, -3, and -4 belonging to lineage II were isolated from different supermarket chains, which have closely evolutionary relationship with clinical ST isolates 50 SNP differences , suggesting that they have high risk to cause listeriosis along food production chain.
Thus, the CC isolates observed in this study implied that although the occurrence of putatively hypervirulent isolates was not high, all isolates associated with the pork production chain could have substantial public health implications.
In this study, WGS was applied as an investigation tool to detect the status of L. Some supermarket chains have different supply channels which results in the diversity of isolates. Multiple farms supplying pigs to the same slaughterhouse possibly caused the abundant diversity of the strains isolated from same supermarket chains.
Importantly, closely evolutionary relationship exists in isolates from the pork sold in different supermarket chains and supplied from the same slaughterhouse, which indicates that L. The genetic similarities between isolates from different supermarket chains suggest the importance and necessity of tracking and detecting the sources of meat supply at both the slaughterhouse and farm levels.
The high isolation rates from contaminated pork meat supplied via 11 supermarket chains in Wuhan city signify the urgent need to strengthen pathogen surveillance systems. Ms Chenal-Francisque is a microbiologist at Institut Pasteur. Her primary research interests include the molecular epidemiology of infectious diseases and evolution of bacterial pathogens, particularly L. Number of isolates from 7 world regions where the most prevalent clones of Listeria monocytogenes are found.
Genetic relationships among Listeria monocytogenes isolates. The graph is a minimum spanning tree based on allelic profiles by using BioNumerics version 6. The isolates of this study are in blue; the L. Each circle represents a multilocus sequence typing genotype ST , the size of which is related to the number of isolates see legend.
Clones, defined as clonal complexes [CC], are composed of groups of STs linked with a single gene difference, denoted as bold lines see legend ; clone number is indicated for the major clones. Worldwide distribution of major clones of Listeria monocytogenes. Emerg Infect Dis [serial on the Internet]. National Center for Biotechnology Information , U. Journal List Emerg Infect Dis v. Emerg Infect Dis.
Author information Copyright and License information Disclaimer. Chenal-Francisque, J. Lopez, T. Cantinelli, V. Caro, C. Tran, A. Leclercq, M. Lecuit, S. Brisse ;. Chenal-Francisque, A. Lecuit ;. Unlike most bacteria, L. The FDA recommends that retailers implement time and temperature controls to reduce the opportunity for the growth of L. Retailers should check with your state for specific guidance. To report a complaint or adverse event illness or serious allergic reaction , you can.
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