Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/29/2004
Publication Date: 6/8/2004
Citation: Chantarapanont, W., Berrang, M.E., Frank, J.F. 2004. Direct microscopic observation of viability of campylobacter jejuni on chicken skin treated wtih selected chemical sanitizing agents. Journal of Food Protection. 67(6):146-1152. Interpretive Summary: Campylobacter is a human pathogen that can be found on chicken skin. This organism can survive on chicken skin despite intensive efforts to kill or remove it during processing. It has been suggested that bacteria located within the many folds, crevices and feather follicles on chicken skin are protected from contact with sanitizers. The objective of this study was to determine if the position or location of Campylobacter cells on chicken skin affects their ability to survive treatment with chlorine, acidified sodium chlorite or peracetic acid. A strain of Campylobacter that fluoresces with a green color visible under a microscope was used to inoculate chicken skin. After chemical treatment, Campylobacter numbers were assessed by culture and direct microscopic observation. Similar Campylobacter counts were noted with both methods. Each sanitizer lowered the overall numbers of live Campylobacter on chicken skin. However, many of the Campylobacter cells that survived treatment were located within 10 µm of the skin surface. These data suggest that the survival of Campylobacter is not dependent on penetration to sites deep within the micro-topography of chicken skin.
Technical Abstract: The objective of this research was to determine the effect of chlorine, acidified sodium chlorite and peracetic acid treatments on viable Campylobacter jejuni located at various depths on chicken skin. Chicken skin was inoculated with C. jejuni transformed with Pcgfp plasmid (GFP-Campylobacter), which also codes for kanamycin resistance. Effectiveness of sanitizer treatments was determined by plate counts using Cefex-campy agar with 200 'g of kanamycin. C. jejuni were also observed on chicken skin using confocal scanning laser microscopy whereby viable and nonviable cells were differentiated by the ability of live cells to take up staining with 5-cyano-2,3-ditolyl tetrazolium chloride (CTC). Sodium hypochlorite, peracetic acid, and acidified sodium chlorite were each applied at 40 ppm or 100 ppm for 2 or 15 min. When measured by plating, each sanitizer resulted in approximately a 1 log decrease when used at 100 ppm for 15 min. and no significant decrease when used at 40 ppm for 2 min. Numbers of viable cells observed on the skin by direct microscopic count were similar to numbers obtained by plate count. Although viable counts decreased with sanitizer treatments, the total number of Campylobacter cells (live plus dead) attached to the skin remained unchanged. Viable C. jejuni were observed at depths of 0-10, 10-20, and 30-40 'm on the chicken skin after all sanitizer treatments. Most of the C. jejuni that survived treatment were located at 0-10'm depth, which is where most of the viable cells were located before treatment. The inability of chemical sanitizers to effectively eliminate C. jejuni on chicken skin does not appear to be a result of Campylobacter penetrating to protective sites.