Campylobacter spp. as a Foodborne Pathogen: A Review

Campylobacters remain highly important zoonotic pathogens worldwide which infect an estimated 1% of the population of Western Europe each year. Certain campylobacters are also important in infections of animals, particularly of the reproductive tract, and some are involved in periodontal disease. This paper focuses, however, on the two species which are most important in food-borne infections of humans, Campylobacter (C.) jejuni and C. coli. Infection with these campylobacters is serious in its own right but can also have long-term sequelae such as reactive arthritis and Guillain-Barré syndrome. The pathogens are ubiquitous in nature and in domestic animals and, as a consequence, are found frequently in the environment and on many raw foods, of both plant and animal origin and bacterial numbers can be very high on certain key foods like raw poultry meat. Although all commercial poultry species can carry campylobacters, the risk is greater from chicken because of the high levels of consumption. Campylobacters are relatively 'new' zoonotic pathogens as routine culture from clinical specimens only became possible in the late 1970s. As a consequence there is much that still needs to be understood about the behaviour and pathogenicity of these highly important bacteria. In particular, and from a food industry/food safety perspective, it is important to better understand the behaviour of C. jejuni and C. coli in the food production environment, and how this affects their ability to survive certain food production processes. There is a belief that campylobacters are much more sensitive to hostile conditions than either salmonellas or Escherichia coli. Much of data to support this view have been derived from laboratory experiments and may not fully represent the natural situation. Studies are showing that campylobacters may be more robust than previously thought and thus may represent a greater challenge to food safety. We recommend that research is undertaken to better understand how campylobacters behave in the food chain and how responses to relevant conditions affect their ability to survive processing and their virulence. There is also a need to better understand the reasons why campylobacters are capable of frequent change, particularly in the expression of surface antigens.

Campylobacter jejuni has long been recognized as a cause of bacterial food-borne illness, and surprisingly, it remains the most prevalent bacterial food-borne pathogen in the industrial world to date. Natural reservoirs for this Gram-negative, spiral-shaped bacterium are wild birds, whose intestines offer a suitable biological niche for the survival and dissemination of C. jejuni Chickens become colonized shortly after birth and are the most important source for human infection. In the last decade, effective intervention strategies to limit infections caused by this elusive pathogen were hindered mainly because of a paucity in understanding the virulence mechanisms of C. jejuni and in part, unavailability of an adequate animal model for the disease. However, recent developments in deciphering molecular mechanisms of virulence of C. jejuni made it clear that C. jejuni is a unique pathogen, being able to execute N-linked glycosylation of more than 30 proteins related to colonization, adherence, and invasion. Moreover, the flagellum is not only depicted to facilitate motility but as well secretion of Campylobacter invasive antigens (Cia). The only toxin of C. jejuni, the so-called cytolethal distending toxin (CdtA,B,C), seems to be important for cell cycle control and induction of host cell apoptosis and has been recognized as a major pathogenicity-associated factor. In contrast to other diarrhoea-causing bacteria, no other classical virulence factors have yet been identified in C. jejuni. Instead, host factors seem to play a major role for pathogenesis of campylobacteriosis of man. Indeed, several lines of evidence suggest exploitation of different adaptation strategies by this pathogen depending on its requirement, whether to establish itself in the natural avian reservoir or during the course of human infection. (c) 2009 Elsevier GmbH. All rights reserved.

The incidence of human Campylobacter jejuni and C. coli infections has increased markedly in many parts of the world in the last decade as has the number of quinolone-resistant and, to a lesser extent, macrolide-resistant Campylobacter strains causing infections. We review macrolide and quinolone resistance in Campylobacter and track resistance trends in human clinical isolates in relation to use of these agents in food animals. Susceptibility data suggest that erythromycin and other macrolides should remain the drugs of choice in most regions, with systematic surveillance and control measures maintained, but fluoroquinolones may now be of limited use in the empiric treatment of Campylobacter infections in many regions.