Use this URL to cite or link to this record in EThOS:
Title: Survival of Campylobacter jejuni in the environment
Author: Mustafa, Kasem Hamed
ISNI:       0000 0004 6058 6752
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2016
Availability of Full Text:
Access from EThOS:
Access from Institution:
Campylobacter jejuni is an emerging food borne pathogen and a successful human pathogen, with the infection mostly transmitted to humans through consumption of contaminated under-cooked poultry meat. However, the environment can also play a role in transmission either directly or indirectly to humans. The microorganism has reservoirs in water and various animals. Its survival outside the host is generally thought to be poor, but the organism survives well in poultry meat. Previous studies have suggested that the ability to survive may vary between different strain types of C. jejuni. A number of survival experiments were conducted, based on the ability of different C. jejuni strains to retain culturability in sterile distilled water. These experiments demonstrated that survival varies between different strains of C. jejuni and that the retention of culturability was much better at low temperatures (4 °C) than higher temperatures (25 °C). Survival was also better in non-autoclaved natural water. One strain, C. jejuni M1, lost culturability more quickly at both temperatures than the others tested. However, cells remained viable in these samples, suggesting that the bacteria had entered into a viable but non-culturable (VBNC) state under stress conditions. These variations may contribute to the transmission of C. jejuni from the environment to humans or farm animals. Using end-point and Q-PCR assays, a set of stress response genes, including genes implicated previously in the formation of VBNC cells, were targeted for different C. jejuni strains during survival in sterile distilled water. Differences in gene expression between different strains of C. jejuni were identified, including in key genes (luxS, htrA, ppk1), suggesting that these genes might have contributed to strain M1 switching to a VBNC state in response to starvation (sterile distilled water). This is the first report suggesting a role for the C. jejuni luxS (a gene likely to be involved in quorum sensing) in the formation of VBNC state and survival in water. Co-existence with other microorganisms, such as Pseudomonas spp., is one of the suggested survival strategies of C. jejuni in the environment. In a small study using environmental PCR assays, it was demonstrated that when C. jejuni is present in the farm environment, Pseudomonas spp. are also always present. In preliminary in vitro experiments, we demonstrated that some fluorescent Pseudomonas spp. could secret proteinaceous products that enhance the growth of Campylobacter. In natural environments, it is likely that interactions with other species, such as Pseudomonas, play an important role in C. jejuni survival and subsequent transmission to humans or animals.
Supervisor: Winstanley, C. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral