Chitosan Supplementation Reduces Enteric Colonization of Campylobacter jejuni in Broiler Chickens and Down-Regulates Expression of Colonization Genes

Abstract

Campylobacter is one of the leading causes of foodborne bacterial gastroenteritis
worldwide, and poultry is considered as the most common source of human infections. Campylobacter
is prevalent in most poultry flocks and a reduction of Campylobacter in poultry
would greatly reduce the risk of campylobacteriosis in humans. Unfortunately, efforts to reduce
Campylobacter in pre-harvest poultry have been met with limited success. Preliminary studies
with the natural compound, chitosan, demonstrate its ability to kill Campylobacter, in vitro.
The purpose of this study was to determine the ability of feed supplemented chitosan to reduce
enteric Campylobacter colonization in broiler chickens. Additionally, the effect of chitosan on
expression of Campylobacter’s chicken colonization genes was investigated using real-time
quantitative PCR (RT-qPCR). Because chitosan’s antimicrobial properties may vary depending
upon its molecular weight, selected doses of three molecular weight chitosans were supplemented
in the feed and evaluated for efficacy to reduce Campylobacter in chickens. Three
replicate trials were conducted, and in each trial, birds were divided into 10 treatments (n=10
birds/treatment) and were fed 0% (controls), 0.25%, 0.5% or 1% (wt./wt.) of a low, medium or
high molecular weight chitosan. Birds were fed treated feed for the duration of the study and
orally challenged with a four-strain mixture of wild type C. jejuni on day 6. On day 15, the ceca
samples were collected for enumeration of Campylobacter. In all three trials, the 0.5% dose
of the medium molecular weight chitosan reduced cecal Campylobacter counts (P<0.05). RTqPCR
analysis revealed that chitosan down-regulated the expression of chicken colonization
genes as compared to control (P<0.05). These results suggest that supplementation of chitosan
in feed is a potential strategy to reduce the enteric colonization of Campylobacter in pre-harvest
chickens.