Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/13/2009
Publication Date: 5/1/2009
Citation: Sheffield, C.L., Crippen, T.L., Andrews, K., Bongaerts, R.J., Nisbet, D.J. 2009. Characterization of planktonic and biofilm communities of day-of-hatch chicks cecal microflora and their resistance to Salmonella colonization. Journal of Food Protection. 72:959-965. Interpretive Summary: The treatment of animals with a mix of harmless bacteria in an attempt to prevent infection from disease-causing bacteria is a strategy called competitive exclusion. This strategy is used in place of chemical antibiotics to control disease-causing bacteria in food animals. This mix is originally harvested from healthy animals and its bacterial make-up must be determined prior to its use in competitive exclusion treatment. Competitive exclusion treatments or cultures are prepared using a chemostat. A chemostat is a closed vessel system that provides a constant flow of nutrients and an anaerobic atmosphere for the mix of many different bacterial species which make up the competitive exclusion culture. The culture is a combination of liquid or planktonic and solid or biofilm bacterial communities. In the present study, a technique called automated ribotyping was used to identify the bacteria present in both the planktonic and biofilm communities from six mixed bacterial cultures started from chicken cecal material. Ribotyping provided rapid and precise identification of the individual species of bacteria contained within the mixed culture. In total, ten species of bacteria from eight different genera were found among the six cultures. Overall, planktonic communities were more diverse than the biofilm communities. Two-thirds of the planktonic communities contained four or more species of bacteria. In contrast, only one of the biofilm communities contained more than two species of bacteria. Enterococcus faecalis was the only species found in both communities from all the cultures. This study is the first to use automated ribotyping to identify the bacterial species found in both the biofilm and planktonic communities within cultures started from chicken cecal material.
Technical Abstract: Public and regulatory focus on the use of antimicrobial agents in food animals, especially poultry, and the related risk of developing antibiotic resistance among pathogenic microorganisms has fostered an increased interest in the use of probiotics and competitive exclusion cultures as alternatives to antibiotics within the agricultural arena. Despite increased information relating to the importance of bacterial biofilms and their potential as a contributory factor in the development of bacterial resistance there is a lack of information relating to the role of biofilm in the development and maintenance of effective competitive exclusion cultures. We characterized and compared the biofilm and planktonic communities within continuous flow cultures of chicken cecal microflora using automated ribotyping. Six culture systems were examined and 10 species from eight different genera were identified. The planktonic community exhibited the most diversity with 67% containing four or more species of bacteria from six different genera. In contrast, only one of the biofilm community contained more than three species of bacteria. Enterococcus faecalis was the only species isolated from both communities in all cultures. This study has for the first time provided a molecular based characterization of both the biofilm and planktonic communities found in chicken cecal microflora derived culture systems.