Campylobacter inoculation and quantification from broiler cecal samples to compare two plate counting methodologies

Abstract

Campylobacteriosis is a zoonosis, a disease transmitted to humans from animals or animal products. The primarily source of Campylobacter infection in human is believed to be the handling and/or consumption of contaminated meat, especially poultry meat. Although in humans such infections are generally self-limiting, complications can arise and may include bacteraemia, Guillain-Barré syndrome, reactive arthritis and abortion. In this study, 32 birds were divided in 2 groups: a control (C) group and an inoculated (I) group, with 16 birds each. The I group was inoculated orally with 108 CFU/mL of Campylobacter jejuni ATCC 33291, whereas the C group was inoculated with a saline solution. Four chicks per group were euthanized by cervical dislocation at 0, 7, 14 and 21 days post-inoculation (pi). Cecum samples were collected for microbiological analyses. The samples were processed by two plate count methodologies, one developed by the USDA (United States Department of Agriculture) in 2011 (B method) and the other a serial dilution direct count method (A method). All birds from the C group remained negative until day 21. For the I group, the B method was found to be statistically superior to the A method for counting the recovered cells from the cecal contents at 7, 14 and 21 days pi. The microbiological direct plating counting method is a cost effective and rapid method to determine the level of contamination in broilers to help risk assessment programs at the industry level.