Biofilm Formation by Campylobacter jejuni: Influence of Genetic, Environment and Antibiotic Resistance Factors

<i>Campylobacter jejuni </i>is one of the most frequent causes of bacterial gastrointestinal food-borne infection worldwide. Biofilms have been suggested to play a role in survival of these bacteria, which is fastidious in its growth requirements, in the environment. The overall objective of this study was to investigate the effect of environment, genetic and antibiotic resistance factors on biofilm formation by a range of <i>C. jejuni</i> strains isolated from poultry and <i>C. jejuni</i> ATCC 33291 strain. <br> <br> The influence of prior modes of growth, temperature, medium and substrate surface on biofilm formation by the <i>C. jejuni</i> strains was investigated. The results obtained indicated that cells grown as sessile culture and in lower nutrient media generally have a greater ability to form biofilm while growth at different temperatures affect biofilm formation in a strain dependent manner. The results also showed that <i>C. jejuni</i> were able to attach and form biofilms on different abiotic surfaces but none of them demonstrated strong biofilm formation. This finding suggests that environmental factors did affect biofilm formation by <i>C. jejuni</i> and they are more likely to persist in the environment in the form of mixed-species rather than mono-species biofilms. <br> <br> The effect of different media with different dissolved oxygen (DO) levels on biofilm formation by <i>C. jejuni</i> under different oxygen conditions was also determined in this study. The results obtained suggested that different broths used for <i>C. jejuni</i> biofilm generation had different DO contents under different incubation conditions and this is likely to affect the biofilm forming ability of <i>C. jejuni</i>, a finding which confounds previous studies that suggested that biofilm formation by <i>C. jejuni</i> is enhanced under aerobic conditions. <br> <br> The influence of different antibiotics with different modes of action on biofilm formation by <i>C. jejuni</i> was also investigated. The results obtained showed that the presence of certain antibiotics induced biofilm formation by some <i>C. jejuni</i> strains tested. These findings indicate that the presence of antibiotics in the environment as a result of their widespread use to treat or prevent diseases might lead to induction of biofilm formation by some strains which is a public health concern. <br> <br> Biofilm formation by selected <i>C. jejuni</i> strains in mono- and mixed-culture on different abiotic surfaces under flow and aerobic conditions mimicking those in the environment was also investigated using a modified Robbins Device. The results indicated that <i>C. jejuni</i> survival is enhanced by forming mixed-species biofilm with <i>Pseudomonas aeruginosa</i> as compared to mono-species <i>C.</i> <i>jejuni</i> biofilm. These findings provided an indication that the presence of other bacteria species in the environment might enhance the survival of <i>C. jejuni</i> under conditions which are detrimental to them. <br> <br> The influence of the genetic makeup of <i>C. jejuni </i>strains on their biofilm formation was investigated through whole genome sequencing and by constructing mutant strains through transposon mutagenesis. Some genes that might be involved in biofilm formation by <i>C. jejuni</i> have been identified. These genes provide a resource for future investigations in order to understand the molecular mechanisms underlying the biofilm formation by <i>C. jejuni.</i> <br> <br> This study provides a better understanding on the ability of antibiotic resistant <i>C. jejuni</i> strains to form biofilm <i>in</i> <i>vitro</i> under different growth conditions, especially under conditions mimicking those in the environment. In addition, further research on the genes potentially involved in biofilm formation, which were identified in this study, may contribute to knowledge of the molecular mechanisms involved in biofilm formation by <i>C. jejuni.</i> A clearer understanding of how <i>C. jejuni </i>survives in the environment (either by forming biofilm or attach to surfaces or other biofilms) could contribute to development of new strategies to prevent or eliminate <i>C. jejuni