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Campylobacter jejuni has caused several campylobacteriosis outbreaks via raw milk consumption. This study reports follow-up of a milk-borne campylobacteriosis outbreak that revealed persistent C. jejuni contamination of bulk tank milk for seven months or longer. Only the outbreak-causing strain, representing sequence type (ST) 883, was isolated from milk, although other C. jejuni STs were also isolated from the farm. We hypothesized that the outbreak strain harbors features that aid its environmental transmission or survival in milk. To identify such phenotypic features, the outbreak strain was characterized for survival in refrigerated raw milk and in aerobic broth culture by plate counting and for biofilm formation on microplates by crystal violet staining and quantification. Furthermore, whole-genome sequences were studied for such genotypic features. For comparison, we characterized isolates representing other STs from the same farm and an ST-883 isolate that persisted on another dairy farm, but was not isolated from bulk tank milk. With high inocula (105 CFU/ml), ST-883 strains survived in refrigerated raw milk longer (4-6 days) than the other strains (≤3 days), but the outbreak strain showed no outperformance among ST-883 strains. This suggests that ST-883 strains may share features that aid their survival in milk, but other mechanisms are required for persistence in milk. No correlation was observed between survival in refrigerated milk and aerotolerance. The outbreak strain formed a biofilm, offering a potential explanation for persistence in milk. Whether biofilm formation was affected by pTet-like genomic element and phase-variable genes encoding capsular methyltransferase and cytochrome C551 peroxidase warrants further study. This study suggests a phenotypic target candidate for interventions and genetic markers for the phenotype, which should be investigated further with the final aim of developing control strategies against C. jejuni infections.

Campylobacter spp. cause foodborne illness on a global scale. Despite their sensitivity to atmospheric oxygen, Campylobacter spp. often survive O 2 exposure during meat processing. The genetic mechanisms underlying aerotolerance in Campylobacter spp. are not well understood. In this study, C. jejuni strain S2-20 and C. coli strain WA333 were subjected to atmospheric O 2, and transcriptomes were analyzed at multiple timepoints, using RNA-Seq technology. In both species, a large number of genes involved in ribosomal formation and oxidative phosphorylation were downregulated at most timepoints. Upregulation of genes associated with iron acquisition was noted in C. coli but not C. jejuni . Several genes involved in molybdate and tungstate uptake were upregulated in C. jejuni . Molybdate is important for enzymes that allow the use of alternate electron acceptors instead of O 2 . This finding, along with the downregulation of genes involved in oxidative phosphorylation, suggests a shift in C. jejuni from aerobic to anaerobic respiration during aerobic conditions, possibly reducing oxidative stress. Our results also suggest that C. jejuni and C. coli utilize different strategies to survive aerobic conditions. To our knowledge, this is the first study to use RNA-Seq to investigate C. coli aerotolerance on a genome-wide scale.

The mammalian gut microbiota is a complex microbial community with diverse impacts on host biology. House mice ( Mus musculus ) are the major model organism for research on mammals, but laboratory domestication has altered their gut microbiota from that of their wild counterparts. Knowledge about how and why the gut microbiota of this species varies between lab and wild settings and among natural populations could improve its utility as a model organism. Here, we use a large dataset comprising over 800 house mouse samples from multiple laboratory facilities and strains and wild mice from mainland and island populations to investigate gut microbiota variation in this species across contrasting genetic and environmental settings. Across geographically disparate populations, we find that wild mice possess a gut microbiota that is compositionally distinct, displays a higher relative abundance and richness of aerotolerant taxa, and is taxonomically and functionally more diverse than that of lab mice. Longitudinally sampled wild mice also display markedly higher temporal turnover in microbiota composition than lab mice. Wild mice from oceanic islands harboured microbiotas that differed subtly from those of mainland wild mice and were more divergent from lab mouse microbiotas. These findings highlight much greater spatial and temporal turnover of gut microbes in wild compared to laboratory mice.

The control of Campylobacter in poultry at the pre-harvest level is critical to reducing foodborne infections with Campylobacter since the consumption of contaminated poultry is the most frequent cause of human campylobacteriosis. Although poultry vaccination is suggested as useful intervention measures, no Campylobacter vaccines are currently available. To develop live-attenuated oral Campylobacter vaccines, in this study, we evaluated the efficacy of pre-colonization by oxidative stress defense mutants, including knockout mutants of ahpC, katA, and sodB, in preventing Campylobacter jejuni from colonizing poultry. Interestingly, when chickens were pre-colonized with ΔahpC and ΔkatA mutants, rather than the ΔsodB mutant, the level of C. jejuni colonization was significantly reduced within 35 days. Further studies demonstrated when chickens were pre-colonized with the ΔahpC mutant by oral challenge with a high dose (ca., 5 × 108 CFU/bird) and a low dose (ca., 5 × 106 CFU/bird), it twice reduced the level of C. jejuni by 3.9 log10CFU/g feces and 3 log10CFU/g feces after 42 days, respectively, compared to the untreated control. Due to a colonization defect, the ΔahpC mutant was removed from chickens within 42 days. After excretion from the host, moreover, the ΔahpC mutant cannot survive in aerobic environments because of compromised aerotolerance. Our findings suggest that the ahpC mutant has a great potential for on-farm application to control C. jejuni at the pre-harvest level.

Background: Streptococcus mutans and Streptococcus sobrinus are major causative bacterial pathogens of dental caries. Objective: We investigated the applicability of three Lactobacillus strains (L. kefiranofaciens DD2, DD5, and DD6) isolated from kefir and three commercial Lactobacillus strains (L. plantarum ATCC 10012, L. johnsonii JCM 1022, and L. rhamnosus ATCC 7469) as potential oral probiotics with respect to their survivability in an experimental oral environment, antimicrobial activity, and anti-biofilm formation activity against S. mutans and S. sobrinus. Results: Strains DD2, ATCC 10012, ATCC 7469, and JCM 1022 had the best oral survivability, including aerotolerance and enzymatic resistance, and inhibited the growth and biofilm formation of S. mutans and S. sobrinus. In particular, DD2 suppressed all three classes of biofilm formation-associated genes: those associated with carbohydrate metabolism and those encoding regulatory biofilm and adhesion proteins. Conclusions: These results indicate that the novel kefir isolate L. kefiranofaciens DD2 effectively and directly inhibits S. mutans and S. sobrinus.

Despite Earth’s oxygen-free origins and the abundance of microorganisms that thrive without oxygen, little is known about the rates and patterns of mutations in anaerobic species. This study directly measures the mutation rates of three fermentative lactic acid bacteria across 1,000 generations in oxygen-free conditions, revealing elevated and highly biased genome-wide mutation rates in these species compared to oxygen-using bacteria. These results highlight how non-oxygen-related factors contribute to mutagenesis, shaping genome evolution in microbes with anaerobic life histories.

In retail meat products, Campylobacter jejuni , C. coli , and Staphylococcus aureus have been reported in high prevalence. The polymicrobial interaction between Campylobacter and other bacteria could enhance Campylobacter survival during the adverse conditions encountered during retail meat processing and storage. This study was designed to investigate the potential role of S. aureus from retail meats in enhancing the survival of Campylobacter exposed to low temperature, aerobic conditions, and biofilm formation. Results indicated that viable S. aureus cells and filter-sterilized cell-free media obtained from S. aureus prolonged the survival of Campylobacter at low temperature and during aerobic conditions. Biofilm formation of Campylobacter strains was significantly enhanced in the presence of viable S. aureus cells, but the results were inconclusive when extracts from cell-free media were used. In conclusion, the presence of S. aureus cells enhances survivability of Campylobacter strains in adverse conditions such as low temperature and aerobic conditions. Further investigations are warranted to understand the interaction between Campylobacter and S. aureus , and effective intervention strategies are needed to reduce the incidence of both foodborne pathogens in retail meat products.

The high prevalence of Campylobacter spp. in retail liver products was previously reported and has been linked to several outbreaks of campylobacteriosis. The main objective of this study was to investigate the influence of retail liver juices on the survivability of several strains of C. jejuni and C. coli , which were previously isolated from various retail meats at 4 °C. All tested Campylobacter strains showed higher survival in beef liver juice (BLJ) and chicken liver juice (CLJ) as compared to beef and chicken juices (BJ and CJ) or Mueller Hinton broth (MHB) at 4 °C. Overall, C. jejuni strains showed greater survival in retail liver and meat juices as compared to C. coli . CLJ enhanced biofilm formation of most C. coli strains and supported growth in favorable conditions. When diluted, retail liver and meat juices enhanced survival of Campylobacter strains at low temperatures and increased aerotolerance. In conclusion, beef and chicken liver juices enhanced the survival of C. jejuni and C. coli strains at low temperatures, which helps explain the high prevalence of Campylobacter spp. in retail liver products.

Background Clostridium septicum is an opportunistic pathogen residing in the human gut flora. Due to its aerotolerance and production of exotoxins, dissemination is an uncommon but potentially lethal condition, often associated with underlying malignancy. This report represents the first described case of a patient with aortic, musculoskeletal and epidural infection caused by C. septicum. It illustrates an example of successful treatment and discusses specific treatment options in relation to current antibiotic and surgical recommendations. Case presentation We report a rare case of a 76-year-old man presenting with mild symptoms, who developed life-threatening complications caused by C. septicum including an aortic aneurysm as well as an epidural abscess and spondylodiscitis. The patient was successfully treated with endovascular stents in conjunction with a six-week course of intravenous antibiotics and was discharged from the hospital with oral clindamycin. After more than a year on oral antibiotics the treatment was terminated, which promptly led to a relapse of C. septicum bacteremia and spondylodiscitis. Following a second hospitalization with IV therapy, lifelong suppressive antibiotic therapy was deemed necessary. Conclusion C. septicum bacteremia is a severe condition that may cause multifocal infection although presenting with few clinical signs. This unique case reflects the aggressiveness of the bacteria and how antibiotic and surgical treatment should be thoughtfully considered in the presence of aortitis, epidural abscesses and spondylodiscitis.

Campylobacter, a common foodborne human pathogen, is considered sensitive to oxygen. Recently, aerotolerant (AT) Campylobacter jejuni with the ability to survive under aerobic stress has been reported. Here, we investigated the prevalence of hyper-aerotolerant (HAT) Campylobacter coli from duck sources (118 carcasses and meat) and its characteristics to assess potential impacts on public health. Half of 56 C. coli isolates were HAT and most harbored various virulence genes including flaA, cadF, cdtA, ceuB, and wlaN. Moreover, 98.2% of C. coli isolates showed resistance to quinolones, including ciprofloxacin (CIP), and nine (16.1%) showed high-level resistance to ciprofloxacin (Minimum Inhibitory Concentration, MIC ≥ 32 μg/mL) and most of these were HAT. Based on genetic relatedness between C. coli from duck sources and those from human sources (PubMLST and NCBI), HAT isolates sharing the same MLST sequence types were significantly more prevalent than those not sharing the same sequence types as those from human sources. Therefore, HAT C. coli is prevalent in duck sources, and is most likely transmitted to humans through the food chain given its aerotolerance. This being so, it might pose a threat to public health given its virulence and antimicrobial resistance (AMR). This study will assist in improving control strategies to reduce farm-to-table HAT C. coli transmission to humans.