Prevalence and Virulence Characterization of Listeria monocytogenes in Chilled Pork in Zhejiang Province, China

Genomic Insights into Antibiotic Resistance and Virulence of Listeria Monocytogenes Isolated from Chongqing, China

Listeria monocytogenes (L. monocytogenes) is a pathogen of significant concern in food due to its ability to survive and multiply under harsh environmental conditions, such as high osmotic pressure, low temperatures, and freezing. This bacterium can cause listeriosis, a severe infection particularly dangerous for high-risk groups including newborns, pregnant women, and immunocompromised patients, due to its high morbidity and mortality rates. This study aimed to investigate the molecular epidemiological characteristics of L. monocytogenes isolated in Chongqing, southwest China. A total of 72 L. monocytogenes isolates collected between 2015 and 2022 were analyzed using whole-genome sequencing (WGS). Multilocus sequence typing (MLST) revealed 15 sequence types (STs), with ST9 (20.83%), ST87 (19.44%), and ST8 (13.89%) being the most prevalent. The isolates were classified into two phylogenetic lineages and four serotypes, with serotypes 1/2b (lineage I) and 1/2a (lineage II) representing 36.11% and 41.67%, of the isolates, respectively. Antibiotic resistance gene analysis showed a high prevalence of the tetracycline resistance gene tet(M), β-lactam resistance gene blaZ, and erythromycin resistance genes msr(A), msr(D), and mef(A). All isolates contained Listeria pathogenicity islands (LIPI-1) and LIPI-2; 12 isolates carried LIPI-3, and 17 isolates carried LIPI-4, with all ST87 isolates harboring LIPI-4. The ST87 isolates were primarily sourced from meat products. These findings indicate that L. monocytogenes isolates in Chongqing harbor multiple virulence and antibiotic resistance genes, underscoring the need for ongoing surveillance and risk assessment, particularly for ST87 in meat products.

Clinical Outcome and Factors with Dietary Behaviors in Pregnant Women with Listeria monocytogenes: A Hospital-Based Case-Control Study in Shanghai

Listeriosis is a globally rare foodborne disease that causes fetal-placental infection, leading to adverse pregnancy outcome, while limited research among pregnant women is available in China. This study was therefore aimed at analyzing the incidence, clinical manifestations, and clinical outcome of listeriosis among pregnant women and its associated dietary behavior risk factors in prevention. A hospital-based case-control study had been conducted from January 2017 to December 2021. Clinical data, laboratory information, and questionnaires including dietary behaviors and personal hygiene were collected within 2 days after case diagnosis. There were 48 pregnant women, including 12 cases and 36 controls, with an average age of 31.19 ± 3.75 years. The incidence of admission-based listeriosis among pregnant women was 1.6058 per 10,000. The 12 strains were divided into 3 serotypes: 1/2a(83.33%), 1/2b(8.33%), and 4b(8.33%). Among the cases, 5 cases (41.67%) resulted in abortion, 3 cases (25%) induced preterm labor, and 4 cases (33.33%) had full-term deliveries after treatment. There were 7 live births in the case group, among which 6 were admitted to the neonatal intensive care unit (NICU), while 1 case had a healthy fetal outcome. All patients in the control group gave birth to live fetuses. Epidemiological investigation revealed that pregnant women dining at restaurants three or more times per week might increase the risk of having Listeria infection. There were no significant differences in dietary consumed behaviors, hand hygiene, and refrigerator usage behaviors between case and control groups. The study suggested that dining at restaurants might be associated with Listeria infection among pregnant women. Therefore, it is essential to enhance education on listeriosis serious consequences and promote healthy dietary and hygiene habits among pregnant women.