Use of Cellulose Filters to Isolate Naturally Occurring Campylobacter spp. from Contaminated Retail Broiler Meat and Survival of Campylobacter jejuni and Campylobacter coli in Retail Broiler Meat
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Campylobacter spp. are indicated as the most common cause of bacteria-related food-borne illness. Campylobacter is present at all steps of the food cycle (i.e. poultry farm, processing plant, retail store, and consumer households). Therefore, a further understanding of the factors associated with the isolation and survival of this pathogen is a necessary step for a reduction in incidence. The first study investigated the parameters for the efficient isolation of Campylobacter through 0.65 μm Millipore filters on a selective medium. We determined the minimum number of Campylobacter cells needed to pass the filter and the effect of the status of the cells. We also determined the minimum number of cells to pass the filter from enriched food samples. Previous studies have indicated membrane filtration as an effective isolation technique for Campylobacter spp. from fecal samples. However, a large number of cells were required for detection. To determine the minimum required cells that go through the filters, experiments were done with healthy (24-h under microaerobiosis), coccoid, centrifuged (20 min, 16,000 g) and non-flagellated mutant cells. We also determined the minimum number of cells needed to isolate Campylobacter spp. from naturally contaminated enriched retail broiler samples. Experiments included 0.65-μm-pore membrane filters (Millipore Corp.) on modified Campy-Cefex agar plates. To determine the rate of passage of Campylobacter through the membrane filters, inoculated filters were harvested at different time intervals and analyzed with scanning electron microscopy (SEM). iii These results demonstrate that cell status may determine the minimum number of cells that can go through the filter. The use of filter membranes is an effective method to obtain pure Campylobacter colonies from enriched food samples. Whereas, the second study investigated the survival of two retail chicken isolates of C. jejuni and two retail chicken isolates of C. coli on boneless, skinless broiler breast meat. Previous studies indicate the survival of Campylobacter spp. on chicken meat before, during, and after processing. Furthermore, its survival at retail is the primary source for at home contamination due to improper food handling techniques. Broiler meat samples were stored at 4ºC and 12ºC for 14 d and -20ºC (common food storage temperatures) for 120 d. For each run, sixteen 30 g (±1 g) pieces of broiler meat were sprayed with C. jejuni or C. coli axenically prepared inocula. Inoculation strains were previously isolated from retail broiler meat. The inoculated breast pieces were stored and sampled at specific time intervals to determine survival and presence. Counts for C. jejuni and C. coli varied significantly across all temperatures, with both species persisting and remaining viable and culturable throughout storage.