Campylobacter succession in broiler chickens

The competitive ability of Campylobacter coli OR12 over C. jejuni OR1 has been examined in experimental broiler chickens following the observation that C. coli replaced an established C. jejuni intestinal colonisation within commercial chicken flocks reared outdoors [El-Shibiny, A., Connerton, P.L., Connerton, I.F., 2005. Enumeration and diversity of campylobacters and bacteriophages isolated during the rearing cycles of free-range and organic chickens. Appl. Environ. Microbiol. 71, 1259-1266]. Co-cultures of C. coli OR12 with C. jejuni OR1, revealed that the two species were able to grow together at similar growth rates in exponential growth phase but if the disparity of the inoculum ratios were >log(10)4 in favour of C. coli OR12, C. jejuni OR1 was observed to prematurely enter decline phase. Chickens were pre-colonised with C. jejuni OR1 at 21-days-old to examine succession in vivo. The birds were inoculated between 2 and 12 days later with C. coli OR12, to determine if the second isolate could efficiently colonise and compete with an established C. jejuni strain. C. coli OR12 were able to co-colonise before replacing C. jejuni OR1 as the dominant species when the birds were more than 27 days of age at the time of administration over a 4-day period. If these criteria were met C. coli OR12 became the dominant isolate otherwise co-colonisation occurred until they were met. C. coli OR12 was also found to displace three alternative C. jejuni strains from pre-colonised chickens challenged with C. coli OR12 at 30 days of age and tested at 40 days. These data raise the possibility of manipulating populations of Campylobacter colonising chickens through competition.

Enumeration and diversity of campylobacters and bacteriophages isolated during the rearing cycles of free-range and organic chickens

Campylobacters and Campylobacter-specific bacteriophages were isolated and enumerated during the rearing cycle of free-range (56 days) and organic chickens (73 days) at 3-day intervals from hatching until slaughter. In both flocks Campylobacter jejuni was the initial colonizer but Campylobacter coli was detected more frequently from 5 weeks of age. The diversity of the Campylobacter isolates was examined by pulsed-field gel electrophoresis of SmaI-digested genomic DNA and antimicrobial resistance typing. Bacteriophages were isolated from 51% (19 of 37 birds) of Campylobacter-positive organic birds (log10 2.5 to log10 5.7 PFU/g of cecal contents). The bacteriophages were all typical group III Campylobacter bacteriophages in terms of genomic size but could be characterized in terms of their host range and placed into five different groups. In contrast to the organic birds, anti-Campylobacter activity (bacteriocin-like) was observed in 26% (10 of 38 birds) of Campylobacter-positive free-range birds, and only one bacteriophage was isolated. Appearance of either bacteriophages or anti-Campylobacter activity was associated with changes in the levels of colonization and the predominant genotypes and species isolated. The frequency and potential influence of naturally occurring bacteriophages and/or inhibitory substances on the diversity and fluctuations of populations of campylobacters have not previously been reported in either free-range or organic chickens.