Yuanyue Tang

Campylobacter jejuni (C. jejuni) is a prevalent zoonotic pathogen that poses a significant threat to global public health, causing gastroenteritis with symptoms ranging from mild diarrhea to severe complications, and is widely distributed among various animal hosts, including poultry, livestock, and wild birds. Among these, wild birds, characterized by their exceptional species diversity, high mobility, and long-distance migratory behavior, are capable of disseminating infectious agents across geographic regions and ecological settings. However, wild birds are increasingly recognized as potential carriers, research on C. jejuni in these hosts remains nascent and fragmented, and a unified understanding has yet to emerge. Therefore, this review synthesizes current knowledge on the prevalence patterns, key determinants, and genetic and transmission characteristics of wild bird origin C. jejuni, aiming to provide a foundation for subsequent in-depth evaluation of the public health significance of C. jejuni derived from wild birds.

Campylobacter jejuni ( C. jejuni ) is a leading cause of human gastroenteritis worldwide and must overcome intestinal innate immunity, including antimicrobial peptide LL-37. However, how C. jejuni responds to LL-37 remains unclear. Here, we showed that C. jejuni infection stimulates intestinal epithelial cells to secrete LL-37, exhibiting effective antibacterial activity against 86.3% of C. jejuni clinical isolates by disrupting essential processes required for bacterial survival. A subset of isolates displays intrinsic resistance, enabling successful intestinal colonization. We further identified conserved serine protease HtrA as the key determinant of resistance. Mechanistically, LL-37 exposure activates transcriptional regulator NssR, which up-regulates htrA expression. Secreted HtrA cleaves LL-37 at Ile ²⁰ -Val ²¹ site, abolishing its antimicrobial activity and promoting bacterial survival. In light of this mechanism, we developed a noncleavable LL-37 ^I20M/V21R that displays enhanced antibacterial activity and promotes bacterial clearance in mice. Together, our findings uncover mechanistic insights into interactions between human enteric pathogens and antimicrobial peptides and provide a potential strategy for combating C. jejuni infection.

Livestock-associated Staphylococcus aureus (LA-MRSA) has been of increasing concern due to its potential risk to humans. This study investigated the prevalence of MRSA in pig production in Eastern China and determined the genomic characteristics of pig-associated MRSA isolates by whole-genome sequencing (WGS). A total of 1,318 samples were collected from pig farms and pig slaughterhouses, and 150 S. aureus were identified, including 63 MRSA isolates and 87 MSSA isolates. MRSA was detected in all pig farms and pig slaughterhouses. The antimicrobial susceptibility test revealed that all MRSA isolates were multidrug-resistant. The WGS and MLST analysis demonstrated that 56 MRSA isolates belonged to clonal complex (CC) 398, and seven MRSA isolates belonged to CC9. All LA-MRSA isolates were absent of phiSa3 phage containing immune evasion cluster (IEC) and possessed an intact hlb gene. In addition, genes associated with Panton-Valentine leukocidin, typically indicative of human adaptation, were not detected. The analysis of antibiotic resistance genes (ARGs) demonstrated that all MRSA isolates contained multiple ARGs. All MRSA isolates had Plthe mecA gene and at least one tetracycline resistance gene. Both tetM and tetK were detected in all MRSA CC398 isolates, while tetL was detected in all MRSA CC9 isolates. The phenicol resistance gene fexA was detected in 51 MRSA isolates, while the linezolid resistance gene cfr was detected in 60 MRSA isolates. The emergence of LA-MRSA CC398 in four pig farms and one slaughterhouse in this study indicates the spread of this clonal complex in the pig production sector in Eastern China. Further investigations are required to understand the potential transmission routes of LA-MRSA CC398 within the pork production chain in China and to assess the potential risks to humans.

Campylobacter is one of the leading causes of bacterial foodborne diseases globally. Poultry is considered a major reservoir for the transmission of Campylobacter to humans. The occurrence and epidemiology of Campylobacter in healthy poultry have been extensively studied, but the prevalence in diseased poultry has rarely been reported. In this study, a total of 1,563 intestinal samples, 547 gallbladder samples, and 3,729 parenchyma organ samples were collected from diseased chickens, ducks, and geese in Yangzhou Veterinary Hospital between December 2016 and September 2017. The bacterial isolates were analyzed for genotype, resistance, and virulence genes. The overall prevalence of Campylobacter was 17.9%, and a significantly higher prevalence was observed in the diseased chickens (21.8%) than in the diseased ducks (12.1%) and geese (11.9%). Campylobacter was significantly more prevalent in the intestinal tract (39.6%), followed by the gallbladder (11.7%) and parenchyma organ (9.7%). Among 84 whole-genome sequenced Campylobacter isolates, we identified 47 multi-locus sequence typing types, of which ST-51 and ST-825 were the most predominant sequence types (STs) for Campylobacter jejuni and Campylobacter coli , respectively. Phylogenetic analysis showed that Campylobacter isolates from different tissues from the same host tended to cluster together with the same STs, which indicated Campylobacter infection in different tissues in vivo . The antimicrobial resistance genes most frequently identified were gyrA (T86I) (97.6%) and tet (O) (65.5%). Our results revealed the high prevalence of Campylobacter in diseased poultry in China, which will help the farms take the necessary action to develop effective mitigation strategies for reducing Campylobacter infection in poultry. IMPORTANCE: Campylobacter is a major cause of campylobacteriosis worldwide, and poultry is the main reservoir for its transmission. Campylobacter was generally considered to be a harmless commensal organism in poultry without pathogenic properties. However, it was proposed that a Campylobacter -like organism may be the cause of vibrionic hepatitis, which poses a significant public health risk. The occurrence and epidemiology of Campylobacter in healthy poultry have been studied systematically, but little is known about the epidemiology of Campylobacter isolates from diseased poultry in China. Therefore, this study determined the prevalence and molecular characterization of Campylobacter from diseased chickens, ducks, and geese in Yangzhou Veterinary Hospital between December 2016 and September 2017, which was critical for improving the diagnosis and prevention of Campylobacter infections.

Cutting boards can serve as potential carriers for the cross-contamination of pathogens from chicken to other surfaces. This study aimed to assess chefs’ handling practices of cutting boards across five provinces in China and identify the key factors contributing to unsafe cutting board usage, including cleaning methods and handling practices. Handling practices associated with cutting boards were examined through a web-based survey (N = 154), while kitchen environment tests were conducted to investigate the splashing or survival of Campylobacter, inoculated in chicken or on cutting boards, to mimic the practices of chefs. Among chefs in the five provinces of China, wood and plastic cutting boards were the most commonly used for preparing chicken meat. Approximately 33.7% of chefs washed boards with running tap water, 31.17% of chefs washed boards with detergent, and 24.03% of chefs cleaned boards by scraping them with a knife after preparing other meats or chicken. The study tested 23 cutting boards from commercial kitchens for Campylobacter presence before and after chicken preparation and cleaning. Among these, 17 were cleaned with a knife, 5 with running tap water, and only 1 with disinfectant. Results showed that cleaning with a knife significantly reduced Campylobacter presence on cutting boards (p < 0.05), while the three main cleaning methods were inadequate in eliminating contamination to a safe level. In kitchen environment tests, contaminated chicken was chopped on cutting boards, with a maximum distance of 60 cm for low contamination, and 120 cm for medium and high contamination levels. This suggested a contamination risk exposure area ranging from 60 cm to 120 cm. Campylobacter survival on surfaces of wood, plastic, and stainless steel was also tested, with plastic surfaces showing the longest survival time (4.5 h at 15 °C and 3.5 h at 25 °C) In comparison, survival time on stainless steel or wood surfaces was only 3 h, implying a cross-contamination risk exposure period of 3 to 4.5 h after chicken preparation. In conclusion, based on the current study data, the practices employed by chefs play an important role in Campylobacter transfer in the kitchen environment. The presence of Campylobacter on cutting boards even after wiping or droplet splashing highlights its potential as a source of cross-contamination in the kitchen environment. So, chefs in China should reinforce their hygiene culture and adopt effective cutting board cleaning practices to prevent pathogen contamination.

This Special Issue focuses on the recent advancements in our understanding of immune responses against zoonoses, which include viral, bacterial, parasitic and fungal diseases

Intestinal infections caused by methicillin-sensitive Staphylococcus aureus (MSSA) have posed a great challenge for clinical treatments. In recent years, the intestinal carriage rates of MSSA have risen steadily in hospital settings in China. However, the epidemiology and molecular characteristics of MSSA from the intestinal tracts of Chinese adult patients remain unknown. In the present study, a total of 80 S. aureus isolates, including 64 MSSA and 16 methicillin-resistant Staphylococcus aureus (MRSA), were recovered from 466 fecal swabs in adult patients between 2019 and 2021 in China. The MSSA isolates exhibited high resistance to penicillin (92.2%) and erythromycin (45.3%). In addition, a higher proportion of MSSA isolates (14.1%) were multidrug-resistant (MDR) strains than that of MRSA isolates (1.3%). Among the 64 MSSA isolates, we identified 17 MLST types, of which ST398 and ST15 were the most predominant types. The most frequently detected resistance genes were blaZ (87.5%) and erm(C) (21.9%). The hemolysin genes (hla, hld, hlgA, hlgB, hlgC) were detected in all the MSSA isolates, but the Panton–Valentine leucocidin (pvl) gene was identified in 1.7% of the MSSA isolates. Our findings indicated that the prevalence and antimicrobial resistance of intestinal MSSA was a serious concern among adult patients in China.

Bacteriophage (phage) is regarded as an antimicrobial alternative for Campylobacter in food production. However, the development of phage resistance to the host is a main concern for the phage application. This study characterized the phage CP39 and investigated the phage resistance of CP39 in Campylobacter jejuni NCTC12662. We determined that phage CP39 belonged to the Myoviridae family by the WGS and phylogenetic analysis. Phage CP39 was confirmed as a capsular polysaccharide (CPS)-dependent phage by primary C. jejuni phage typing. It was further confirmed that the phage could not be adsorbed by the acapsular mutant ΔkpsM but showed the same lytic ability in both the wild-type strain NCTC 12662 and the ΔmotA mutant lacking motile flagella filaments. We further determined that the 06875 gene encoding CDP-glycerol:poly (glycerophosphate) glycerophosphotransferase (CGPTase) in the CPS loci was related to phage CP39 adsorption by SNP analysis and observed a rapid development of phage resistance in NCTC 12662 during the phage infection. Furthermore, we observed a high mutation frequency of 06875 (32%), which randomly occurred in nine different sites in the gene according to colony PCR sequencing. The mutation of the 06875 gene could cause the phase variable expression of non-functional protein and allow the bacteria against the phage infection by modifying the CPS. Our study confirmed the 06875 gene responsible for the CPS-phage adsorption for the first time and demonstrated the phase variable expression as a main mechanism for the bacteria to defend phage CP39. Our study provided knowledge for the evolutionary adaption of bacteria against the bacteriophage, which could add more information to understand the phage resistance mechanism before applying in the industry.