Investigation on the colonisation of Campylobacter strains in the pig intestine depending on available metabolites

Microbial evaluation of wild boar carcasses coming from control culling in the subalpine Prealpi Orobie area, northern Italy

This study tested 32 carcasses of control-culled wild boars in a subalpine area of Northern Italy between May and November 2021, delivered to three approved game meat establishments. Carcasses and organs were submitted to the detection of Salmonella spp., Campylobacter spp., Listeria spp., and Listeria monocytogenes; carcass surfaces were also sampled for microbial counts [total viable count (TVC), Enterobacteriaceae, Escherichia coli, coagulase-positive Staphylococci]. Campylobacter spp. was detected with high prevalence (90.9%) in the caecum as well as Listeria spp. and L. monocytogenes (37.5% and 25%, respectively), whereas only one animal harbored Salmonella spp. (3.8%). A low contamination rate was detected on the carcasses for Campylobacter spp. and Listeria spp. High mean TVC, Enterobacteriaceae, and E. coli counts were detected on the carcasses (5.90, 4.83 and 2.54 Log CFU/cm2, respectively). Animal sex and weight exerted a weak effect on bacterial counts; the same was observed for the culling/sampling interval. Moderately higher counts were detected in animals culled with high (>15°C) environmental temperatures. Animals shot in the abdomen showed higher counts for all the parameters except for Staphylococci, and an increasing count of enteric bacteria was observed when considering head/neck, shoulder, chest, and abdomen locations. A significant difference among the plants was observed, independently from the other factors, thus stressing the importance of the application of hygiene procedures in approved game meat establishments to limit carcass contamination.

Advances in Campylobacter: Molecular Epidemiology, Virulence Factors, Immune Responses and Drug Resistance

Campylobacter infections, caused by Campylobacter jejuni and Campylobacter coli, are a major global concern, particularly as they are the leading cause of bacterial enteritis [...].

Campylobacter jejuni Response When Inoculated in Bovine In Vitro Fecal Microbial Consortia Incubations in the Presence of Metabolic Inhibitors

Infection with the foodborne pathogen Campylobacter is the leading bacterial cause of human foodborne illness in the United States. The objectives of this experiment were to test the hypothesis that mixed microbial populations from the bovine rumen may be better at excluding Campylobacter than populations from freshly voided feces and to explore potential reasons as to why the rumen may be a less favorable environment for Campylobacter than feces. In an initial experiment, C. jejuni cultures inoculated without or with freshly collected bovine rumen fluid, bovine feces or their combination were cultured micro-aerobically for 48 h. Results revealed that C. jejuni grew at similar growth rates during the first 6 h of incubation regardless of whether inoculated with the rumen or fecal contents, with rates ranging from 0.178 to 0.222 h-1. However, C. jejuni counts (log10 colony-forming units/mL) at the end of the 48 h incubation were lowest in cultures inoculated with rumen fluid (5.73 log10 CFUs/mL), intermediate in cultures inoculated with feces or both feces and rumen fluid (7.16 and 6.36 log10 CFUs/mL) and highest in pure culture controls that had not been inoculated with the rumen or fecal contents (8.32 log10 CFUs/mL). In follow-up experiments intended to examine the potential effects of hydrogen and hydrogen-consuming methanogens on C. jejuni, freshly collected bovine feces, suspended in anaerobic buffer, were incubated anaerobically under either a 100% carbon dioxide or 50:50 carbon dioxide/hydrogen gas mix. While C. jejuni viability decreased <1 log10 CFUs/mL during incubation of the fecal suspensions, this did not differ whether under low or high hydrogen accumulations or whether the suspensions were treated without or with the mechanistically distinct methanogen inhibitors, 5 mM nitrate, 0.05 mM 2-bromosulfonate or 0.001 mM monensin. These results suggest that little if any competition between C. jejuni and hydrogen-consuming methanogens exists in the bovine intestine based on fecal incubations.

Staphylococcus aureus adapts to the immunometabolite itaconic acid by inducing acid and oxidative stress responses including S-bacillithiolations and S-itaconations

Staphylococcus aureus is a major pathogen, which has to defend against reactive oxygen and electrophilic species encountered during infections. Activated macrophages produce the immunometabolite itaconate as potent electrophile and antimicrobial upon pathogen infection. In this work, we used transcriptomics, metabolomics and shotgun redox proteomics to investigate the specific stress responses, metabolic changes and redox modifications caused by sublethal concentrations of itaconic acid in S. aureus. In the RNA-seq transcriptome, itaconic acid caused the induction of the GlnR, KdpDE, CidR, SigB, GraRS, PerR, CtsR and HrcA regulons and the urease-encoding operon, revealing an acid and oxidative stress response and impaired proteostasis. Neutralization using external urea as ammonium source improved the growth and decreased the expression of the glutamine synthetase-controlling GlnR regulon, indicating that S. aureus experienced ammonium starvation upon itaconic acid stress. In the extracellular metabolome, the amounts of acetate and formate were decreased, while secretion of pyruvate and the neutral product acetoin were strongly enhanced to avoid intracellular acidification. Exposure to itaconic acid affected the amino acid uptake and metabolism as revealed by the strong intracellular accumulation of lysine, threonine, histidine, aspartate, alanine, valine, leucine, isoleucine, cysteine and methionine. In the proteome, itaconic acid caused widespread S-bacillithiolation and S-itaconation of redox-sensitive antioxidant and metabolic enzymes, ribosomal proteins and translation factors in S. aureus, supporting its oxidative and electrophilic mode of action in S. aureus. In phenotype analyses, the catalase KatA, the low molecular weight thiol bacillithiol and the urease provided protection against itaconic acid-induced oxidative and acid stress in S. aureus. Altogether, our results revealed that under physiological infection conditions, such as in the acidic phagolysome, itaconic acid is a highly effective antimicrobial against multi-resistant S. aureus isolates, which acts as weak acid causing an acid, oxidative and electrophilic stress response, leading to S-bacillithiolation and itaconation.