Genetic Diversity of Campylobacter jejuni Isolated From Avian and Human Sources in Egypt

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.

A multiplex PCR assay was used to simultaneously detect genes from the five major clinically relevant Campylobacter spp. Those genes selected were hipO and 23S rRNA from Campylobacter jejuni; glyA from each of C. coli, C. lari, and C. upsaliensis; and sapB2 from C. fetus subsp. fetus. The assay was evaluated with 137 clinical and environmental isolates and was found to be rapid and easy to perform and had a high sensitivity and specificity for characterizing isolates, even in mixed cultures.

Campylobacter contaminated broiler chicken meat is an important source of foodborne gastroenteritis and poses a serious health burden in industrialized countries. Broiler chickens are commonly regarded as a natural host for this zoonotic pathogen and infected birds carry a very high C. jejuni load in their gastrointestinal tract, especially the ceca. This eventually results in contaminated carcasses during processing. Current intervention methods fail to reduce the colonization of broiler chicks by C. jejuni due to an incomplete understanding on the interaction between C. jejuni and its avian host. Clearly, C. jejuni developed several survival and colonization mechanisms which are responsible for its highly adapted nature to the chicken host. But how these mechanisms interact with one another, leading to persistent, high-level cecal colonization remains largely obscure. A plethora of mutagenesis studies in the past few years resulted in the identification of several of the genes and proteins of C. jejuni involved in different aspects of the cellular response of this bacterium in the chicken gut. In this review, a thorough, up-to-date overview will be given of the survival mechanisms and colonization factors of C. jejuni identified to date. These factors may contribute to our understanding on how C. jejuni survival and colonization in chicks is mediated, as well as provide potential targets for effective subunit vaccine development.