Various forms of solid tumors harbor intracellular bacteria, but the physiological consequences of these microorganisms are poorly understood. We show that Campylobacter is significantly enriched in primary colorectal cancer (CRC) lesions from patients with metastasis. Campylobacterjejuni-derived cytolethal distending toxin (CDT) promotes CRC metastasis through JAK2-STAT3-MMP9 signaling in liver or pulmonary metastatic mice models, as confirmed in C. jejuni-infected human colonic tissue and CDT-treated colonic tumoroids from patients. Genetic deletion of cdtB (ΔcdtB) or purified CdtB protein demonstrates that the genotoxin is essential for C. jejuni's pro-metastatic property. In C.-jejuni-colonized mice, increased translocation of CDT-producing C. jejuni to extraintestinal implanted tumors potentially leads to accelerated metastasis of these tumors. Overall, these findings demonstrate that an intratumor-bacteria-derived genotoxin accelerates tumor metastasis, potentially opening a new diagnostic and therapeutic avenue for cancer management.

Campylobacter is one of the most important foodborne pathogens worldwide, and poultry is regarded as the main reservoir of Campylobacter. The contamination of Campylobacter in broiler chickens at the farm level is closely related to the transmission of Campylobacter in the poultry production chain. This study identified 464 Campylobacter isolates from 1,534 samples from broiler rearing period and slaughtering process including 233 Campylobacter jejuni isolates and 231 Campylobacter coli isolates. We have observed a dynamic distribution of Campylobacter during broiler chicken production, that 66.3% of Campylobacter isolates were C. jejuni during broiler rearing period, while C. coli occupied 60.4% of Campylobacter isolates during the broiler slaughtering process. A tag-label method allowed us to track the dynamic of Campylobacter in each broiler chicken from 31-day age at rearing to the partition step in the slaughterhouse. At the 31-day during rearing, 150 broiler chicken were labeled, and was tracked for Campylobacter positive from rearing period to slaughtering process. Among the labeled broiler, 11 of the tracking broiler samples were able to detect Campylobacter from rearing period to slaughtering. All Campylobacter isolates from the 11 tracking samples were sequenced and analyzed. C. jejuni isolates were divided into four STs and C. coli isolates were divided into six STs. Isolates with identical core genome were observed from the same tag-labeled samples at different stages indicating a vertical transmission of Campylobacter in the early broiler meat production. Meanwhile, the core genome analysis elucidated the cross-contamination of Campylobacter during the rearing period and the slaughtering process. The virulotyping analysis revealed that all C. jejuni isolates shared the same virulotypes, while C. coli isolates were divided into three different virulotypes. The antimicrobial resistance gene analysis demonstrated that all Campylobacter isolates contained at least two antibiotic resistance genes (ARGs), and the ARG profiles were well-corresponding to each ST type. Our study observed a high prevalence of Campylobacter during the early chicken meat production, and further studies will be needed to investigate the diversity and transmission of Campylobacter in the poultry production chain.

Campylobacter jejuni is an important foodborne pathogen causing campylobacteriosis. It can infect humans through the consumption of contaminated chicken products or via the direct handling of animals. Diallyl trisulfide (DATS) is a trisulfide compound from garlic extracts that has a potential antimicrobial effect on foodborne pathogens. This study investigated the antimicrobial activity of DATS on C. jejuni by evaluating the minimal inhibitory concentrations (MICs) of C. jejuni 81-168, and fourteen C. jejuni isolates from chicken carcasses. Thirteen of 14 C. jejuni isolates and 81-176 had MICs ≤ 32 μg/mL, while one isolate had MIC of 64 μg/mL. Scanning electron microscopy (SEM) analysis showed the disruption and shrink of C. jejuni bacterial cell membrane after the DATS treatment. A time-killing analysis further showed that DATS had a dose-dependent in vitro antimicrobial effect on C. jejuni during the 24 h treatment period. In addition, DATS also showed an antimicrobial effect in chicken through the decrease of C. jejuni colony count by 1.5 log CFU/g (cloacal sample) during the seven-day DATS treatment period. The transcriptional analysis of C. jejuni with 16 μg/mL (0.5× MIC) showed 210 differentially expression genes (DEGs), which were mainly related to the metabolism, bacterial membrane transporter system and the secretion system. Fourteen ABC transporter-related genes responsible for bacterial cell homeostasis and oxidative stress were downregulated, indicating that DATS could decrease the bacterial ability to against environmental stress. We further constructed five ABC transporter deletion mutants according to the RNA-seq analysis, and all five mutants proved less tolerant to the DATS treatment compared to the wild type by MIC test. This study elucidated the antimicrobial activity of DATS on C. jejuni and suggested that DATS could be used as a potential antimicrobial compound in the feed and food industry.

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.

FlhF is a key protein required for complete flagellar synthesis, and its deletion results in the complete absence of a flagella and thus motility in Campylobacter jejuni. However, the specific mechanism still remains unknown. In this study, RNA-Seq, EMSAs, ChIP-qPCR and β-Galactosidase assays were performed to elucidate the novel interactions between FlhF and genes involved in flagellar synthesis. Results showed that FlhF has an overall influence on the transcription of flagellar genes with an flhF mutant displaying down-regulation of most flagellar related genes. FlhF can directly bind to the flgI promoter to regulate its expression, which has significant expression change in an flhF mutant. The possible binding site of FlhF to the flgI promoter was explored by continuously narrowing the flgI promoter region and performing further point mutations. Meanwhile, FlhF can directly bind to the promoters of rpoD, flgS, and fliA encoding early flagellin regulators, thereby directly or indirectly regulating the synthesis of class I, II, and III flagellar genes, respectively. Collectively, this study demonstrates that FlhF may directly regulate the transcription of flagellar genes by binding to their promoters as a transcriptional regulator, which will be helpful in understanding the mechanism of FlhF in flagellar biosynthetic and bacterial flagellation in general.

Pseudogenes are defined as “non-functional” copies of corresponding parent genes. The cognition of pseudogenes continues to be refreshed through accumulating and updating research findings. Previous studies have predominantly focused on mammals, but pseudogenes have received relatively less attention in the field of microbiology. Given the increasing recognition on the importance of pseudogenes, in this review, we focus on several aspects of microorganism pseudogenes, including their classification and characteristics, their generation and fate, their identification, their abundance and distribution, their impact on virulence, their ability to recombine with functional genes, the extent to which some pseudogenes are transcribed and translated, and the relationship between pseudogenes and viruses. By summarizing and organizing the latest research progress, this review will provide a comprehensive perspective and improved understanding on pseudogenes in microorganisms. Key points: • Concept, classification and characteristics, identification and databases, content, and distribution of microbial pseudogenes are presented. • How pseudogenization contribute to pathogen virulence is highlighted. • Pseudogenes with potential functions in microorganisms are discussed.