Denaturing gradient gel electrophoresis-polymerase chain reaction comparison of chitosan effects on anaerobic cultures of broiler cecal bacteria and Salmonella Typhimurium

Authors: Hume, Michael; SOHAIL, MUHAMMAD UMAR - Government College University

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2017
Publication Date: 4/1/2018
Citation: Hume, M.E., Sohail, M.U. 2018. Denaturing gradient gel electrophoresis-polymerase chain reaction comparison of chitosan effects on anaerobic cultures of broiler cecal bacteria and Salmonella Typhimurium. Foodborne Pathogens and Disease. 15(4):246-252. https://doi.org/10.1089/fpd.2017.2365.
DOI: https://doi.org/10.1089/fpd.2017.2365

Interpretive Summary: Salmonella contamination is a major problem for the poultry industry. The use of alternatives to traditional antibiotics against Salmonella in poultry may help lessen the development of resistance to antibiotics of importance to human health. Chitin makes up structural parts of a wide assortment of organisms such as shrimp, crabs, insects, and fungi. Chitin, when converted to chitosan, has been shown to kill bacteria. Chitosan of various sizes (small, medium, large) have been shown to have different abilities to kill bacteria. In the current study, populations of intestinal bacteria from three adult chickens and Salmonella were grown together in growth solutions containing small, medium, and large chitosan. The effects of these chitosan sizes were determined by using a molecular method to examine changes in the populations of intestinal bacteria and by counting the numbers of live Salmonella following exposure. The populations of intestine bacteria from the three chickens were shown by the molecular method to be very different from each other. However, exposure to the three chitosan sizes resulted in populations from all three intestine sources being identical regardless of the size of chitosan in the growth solution. Salmonella numbers were dramatically decreased by all three chitosan sizes. These results are of interest to researchers and producers interested in identifying alternatives to traditional antibiotics useful against Salmonella in poultry.

Technical Abstract: Salmonella colonization and product contamination are major poultry industry problems. Alternatives to traditional antibiotics against Salmonella offer the potential to lessen the development of resistance to antibiotics of importance to human health. The chitin derivative chitosan has drawn substantial attention for its bactericidal properties. Various chitosan molecular weight (MW) preparations have been shown to have varied effects against different bacteria in monoculture. In the current study, cecal contents from three adult broilers and Salmonella Typhimurium were exposed in mixed in vitro anaerobic culture to three chitosan preparations (0.08%, wt/vol), low (LMW), medium (MMW), and coarse (CMW). The effects of chitosan on cecal bacteria and Salmonella were examined by denaturing gradient gel electrophoresis (DGGE) and Salmonella enumeration. Compared to Salmonella grown in monoculture, Salmonella decreased by about 1.5 log CFU/ml when grown in mixed culture with cecal contents. Salmonella monocultures in the presence of 0.08% of the chitosan solvent acetic acid decreased growth by almost 3.5 log CFU/ml. Combining acetic acid and cecal contests reduced Salmonella by 7 log CFU/ml. Adding the chitosan preparations to the mixtures reduced Salmonella by 8 log CFU/ml. Bacterial profiles for the three cecal contents were shown by DGGE to be very different, and profiles of contents grown in the presence of 0.08% acetic acid were very different from those of cecal contents grown without the chitosan solvent. Culturing cecal contents in the presence of chitosan altered the bacterial profiles from the control and acetic acid-only cultures. However, profiles from all three cecal sources were identical regardless of the MW chitosan in the culture medium.