Nathanon Trachoo and Sasinee Kunyaboon

pp. 991 - 998

Abstract

Survival of C. jejuni in biofilms isolated from two chicken houses in Thailand (FBRL-C04, FBRLB05 and FBRL-B06) after chlorine treatment was studied. Biofilm cultures were grown on stainless steel surface in 50% trypticase soy broth for 3 days, subsequently C. jejuni cells were allowed to attach to these
biofilms for 4 h at 25ºC. Sodium hypochlorite was used to prepare sanitizing solution with active chlorine of 15 ppm and 25 ppm. Stainless steel coupons containing C. jejuni with and without biofilms were treated with chlorine for 30 sec and neutralized with 0.05% sodium thiosulfate. At both concentrations, C. jejuni were inactivated to lower than 1 log₁₀CFU/cm² when initial attachment load was approximately 4 log₁₀CFU/cm².However, C. jejuni in all samples treated with 15 ppm active chlorine were recovered in enrichment media. When treated with the higher concentration of chlorine, 25 ppm, C. jejuni in biofilm of FBRL-C04 (5/9),
FBRL-B06 (1/9) and biofilm-free surface (1/9) could also be recovered. This indicates that chlorine treatment at 15 and 25 ppm could not completely inactivate C. jejuni attached to biofilms and biofilm-free surfaces. Biofilm of FBRL-C04 enhanced the survival of C. jejuni after chlorine treatment at 25 ppm although biofilm initial attachment as determined by plate count method was similar to that of other biofilms. Attachment load of viable biofilm cells may not contribute to enhanced survival of C. jejuni in chlorine treatment.