Editorial: About the Foodborne Pathogen Campylobacter

Abstract

Editorial on the Research Topic About the Foodborne Pathogen Campylobacter The name “Campylobacter” comes from ancient Greek meaning “curved rod” which describes the shape of this microorganism. Campylobacter was firstly isolated as a Vibrio species from epizootic ovine abortion in 1906 by McFadyean and Stockman (1913), and renamed in 1973 as the neotype strain Campylobacter after showing significant biological differences with Vibrio species (Véron and Chatelain, 1973). Rather than a curved rod, the shape looks more like to a spiral and can develop in to filamentous or coccoid forms under stressful conditions (Tangwatcharin et al., 2006; Ghaffar et al., 2015; Rodrigues et al., 2016). Nowadays, Campylobacter spp. are classified among the ε-proteobacteria in the family of Campylobacteriaceae (Vandamme et al., 1991). Campylobacter has emerged as the leading cause of bacterial foodborne infections in developed countries, having surpassed Salmonella several years ago, and represents a significant economic burden (EFSA and ECDC, 2016). Although new species of Campylobacter have been recently discovered, human cases of campylobacterosis are dominated by two main species, Campylobacter jejuni and, to a lesser extent, Campylobacter coli. Quantitative epidemiology reports reveal high rates of contamination for broiler chickens and carcasses by Campylobacter (Hue et al., 2010; Lawes et al., 2012; Powell et al., 2012). The presence of Campylobacter was also detected in other farm animals or foodstuffs due to cross contamination (EFSA and ECDC, 2016). Campylobacter in poultry remains a problem with no effective control measures available that can be recommended for microbial food/farm safety guidelines to mitigate the risk of flock colonization. Campylobacter also remains a puzzle as to how an obligate microaerobic bacterium can survive from farm to retail outlets. The underlying molecular mechanisms of persistence, survival and pathogenesis appear to represent a combination peculiar to this pathogen, which are not shared with other foodborne bacterial pathogens such as Listeria monocytogenes, Salmonella enterica, Escherichia coli, and Staphylococcus aureus. This topic includes 18 published articles describing original studies of C. jejuni and C. coli that deal with (1) epidemiology and animal carriage, (2) host interaction, (3) control strategies, (4) metabolism and regulation specificities of these two pathogen species, (5) methodology to improve cultural technique and (6) chicken gut microbiota challenged with Campylobacter. Organic animal production schemes differ in many ways (antibiotic use, herd structure, feeding regimes, access to outdoor areas, space allowance) from conventional rearing systems, and therefore can have an impact in the occurrence, transmission and pathogenicity of foodborne pathogens, including Campylobacter spp. In this research topic, is however shown that organic pig production schemes have a minor impact on the epidemiology of C. coli. Kempf et al. monitored the prevalence and antimicrobial resistance of C. coli isolated from conventional and organic pigs in farms from France and Sweden and observed no significant difference in prevalence between pigs in organic and conventional productions. They however observed in France a higher occurrence of antimicrobial resistant C. coli isolates (particularly against the antibiotics tetracycline and erythromycin) from conventional rearing systems. Denis et al. characterized C. coli isolates obtained from 19 organic pig farms and 24 conventional pig farms through pulsed field gel electrophoresis, multilocus sequence typing, detection of nine virulence-associated genes and evaluation of the adhesion and invasion capacity on Caco-2 cells. They concluded that pig farm management strategies did not influence the diversity and virulence of C. coli. Ayllón et al. used a proteomic approach to examine relative differences in protein expression levels between C. jejuni interacting with human (INT-407) and porcine (IPEC-1) cell lines. The study revealed 366 differentially expressed proteins after 3 h infection and 485 after 24 h. The identities of the protein enabled analysis of the response pathways that indicate differences in the timing of inflammatory responses between the cell lines and comparative down regulation of the signaling pathways that control cell migration, endocytosis and cell cycle progression in the porcine cell line. The authors attribute the differences in the cellular pathway responses to C. jejuni exposure as indicative of the processes that establish either infective or commensal behavior respectively in human or porcine hosts. Upadhyay et al. examined the potential of three phytochemicals generally recognized as safe (GRAS) and applied at sub-inhibitory concentrations to bacterial growth, to prevent or reduce the severity of human infection. Phytochemical treatments of C. jejuni resulted in reduced motility and a reduction in the expression of cytolethal distending toxin that could result in favorable effects on human infection. Using human intestinal epithelial (Caco-2) cell-based assays the authors demonstrated the abilities of trans-cinnamaldehyde (0.01%), carvacrol (0.002%), and eugenol (0.01%) to reduce the processes of attachment, invasion and translocation of C. jejuni. Effective control of Campylobacter on commercial broiler chicken farms is proving more than challenging. Microbiological risk assessments suggest that if reductions in the intestinal loads carried by chickens could be translated on to poultry meat then these measures could make a significant impact on the cases of human campylobacterosis (Boysen...