Genetic diversity, virulence factors, and antimicrobial resistance of Listeria monocytogenes from food, livestock, and clinical samples between 2002 and 2019 in China.

Listeria monocytogenes remains a significant public health threat, leading to invasive listeriosis with severe manifestations (i.e. septicemia, meningitis, and abortion) and up to 30% of fatal cases. Here, we aimed to investigate genotypic diversity, virulence profiles, antimicrobial resistance patterns from a large and integrated population of L. monocytogenes isolates in China (n = 369), including food (n = 326), livestock (n = 25), and hospitalized humans (n = 18) over the years (2002-2019). PCR-based serogrouping showed the dominance of serogroup 1/2a-3a (37.4%) in food, 4a-4c (76%) in livestock, and 1/2a-3a (44.4%) in humans. Phylogenetic lineage analysis revealed the dominance of lineage II (63.4%) in food, lineage III (76%) in livestock, and lineage II (55.5%) in humans. Altogether, 369 isolates were grouped into 55 sequence types (STs) via multi-locus sequence typing (MLST), which belonged to 26 clonal complexes (CCs) and 17 singletons. Among various STs, ST9 (26%) was the most abundant in food, ST202 (76%) in livestock, and ST8 (16.6%) in humans. Overall, ST4/CC4, ST218/CC218, and ST619 isolates harbored both LIPI-3 and LIPI-4 genes subsets indicating their hypervirulence potential. Additionally, a low resistance was observed towards tetracycline (5.1%), erythromycin (3.2%), cotrimoxazole (2.9%), chloramphenicol (2.7%), gentamicin (2.4%), and ampicillin (2.1%). Collectively, detection of hypervirulent determinants and antimicrobial-resistant phenotype among Chinese isolates poses an alarming threat to food safety and public health, which requires a continued and enhanced surveillance system for further prevention of human listeriosis.

Genomic Determinants of Pathogenicity and Antimicrobial Resistance for 60 Global Listeria monocytogenes Isolates Responsible for Invasive Infections.

Listeria monocytogenes remains a significant public health threat, causing invasive listeriosis manifested as septicemia, meningitis, and abortion, with up to 30% of cases having a fatal outcome. Tracking the spread of invasive listeriosis requires an updated knowledge for virulence factors (VFs) and antimicrobial resistance features, which is an essential step toward its clinical diagnosis and treatment. Taking advantage of high-throughput genomic sequencing, we proposed that the differential genes based on the pathogenomic composition could be used to evaluate clinical observations and therapeutic options for listeriosis. Here, we performed the comparative genomic analysis of 60 strains from five continents with a diverse range of sources, representing serotypes 1/2a, 1/2b, 1/2c, and 4b, comprising lineage I and lineage II and including 13 newly contributed Chinese isolates from clinical cases. These strains were associated with globally distributed clonal groups linked with confirmed foodborne listeriosis outbreak and sporadic cases. We found that L. monocytogenes strains from clonal complex (CC) CC8, CC7, CC9, and CC415 carried most of the adherence and invasive genes. Conversely, CC1, CC2, CC4, and CC6 have the least number of adherence and invasive genes. Additionally, Listeria pathogenicity island-1 (LIPI-1), LIPI-2, intracellular survival, surface anchoring, and bile salt resistance genes were detected in all isolates. Importantly, LIPI-3 genes were harbored in CC3, CC224, and ST619 of the Chinese isolates and in CC1, CC4, and CC6 of other worldwide isolates. Notably, Chinese isolates belonging to CC14 carried antibiotic resistance genes (ARGs) against ß-lactams (blaTEM-101, blaTEM-105) and macrolide (ermC-15), whereas CC7 and CC8 isolates harbored ARGs against aminoglycoside (aadA10_2, aadA6_1), which may pose a threat to therapeutic efficacy. Phylogenomic analysis showed that CC8, CC7, and CC5 of Chinese isolates, CC8 (Swiss and Italian isolates), and CC5 and CC7 (Canadian isolates) are closely clustered together and belonged to the same CC. Additionally, CC381 and CC29 of Chinese isolates shared the same genomic pattern as CC26 of Swiss isolate and CC37 of Canadian isolate, respectively, indicating strong phylogenomic relation between these isolates. Collectively, this study highlights considerable clonal diversity with well-recognized virulence and antimicrobial-resistant determinants among Chinese and worldwide isolates that stress to design improved strategies for clinical therapies.

Diversified sources for human infections by Salmonella enterica serovar newport.

Salmonella enterica Newport (S. Newport), with phylogenetic diversity feature, contributes to significant public health concerns. Our previous study suggested that S. Newport from multiple animal-borne routes, with distinct antibiotic resistant pattern, might transmit to human. However, their genetic information was lacking. As a complement to the earlier finding, we investigate the relationship between each other among the hosts, sources, genotype and antibiotic resistance in S. Newport. We used the multilocus sequence typing (MLST) in conjunction with minimum inhibitory concentration of 16 antibiotics of globally sampled 1842 S. Newport strains, including 282 newly contributed Chinese strains, to evaluate this association. Our analysis reveals that sequence types (STs) are significantly associated with different host sources, including livestock (ST45), birds (ST5), contaminated water and soil (ST118), reptiles (ST46) and seafood (ST31). Importantly, ST45 contained most of (344/553) the multi-drug resistance (MDR) strains, which were believed to be responsible for human MDR bacterial infections. Chinese isolates were detected to form two unique lineages of avian (ST808 group) and freshwater animal (ST2364 group) origin. Taken together, genotyping information of S. Newport could serve to improve Salmonella source-originated diagnostics and guide better selection of antibiotic therapy against Salmonella infections.