Validation of dog treats and bones for the presence of Salmonella through in-plant analysis and inoculation challenge studies

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Title: Validation of dog treats and bones for the presence of Salmonella through in-plant analysis and inoculation challenge studies
Author: Daniels, Paden
Abstract: Salmonella is a continual problem within the pet food industry . Salmonella in pet food and treats can lead to a potential human Salmonella infection through the handling of these products . The objective of this experiment was to determine the prevalence of Salmonella in various dog treats through an in -plant analysis study and an inoculation challenge study . For the in -plant analysis study , thirty raw and thirty cooked samples of lamb lung cubes , weasands (weasands ) , pizzles (steer pizzles ) , and jumbo pizzles were delivered to the Texas Tech University Food Microbiology Laboratory on ice and analyzed by the FDA approved BAX system method for detection of Salmonella . When testing raw products , 7 of 30 weasands , 0 of 30 lamb lung cubes , 26 of 30 pizzles , and 29 of 30 jumbo pizzles were positive for Salmonella . For the cooked products , 1 of 30 taffy’s was positive for Salmonella¸ while the other products had no positive cooked samples . During the inoculation challenge , two different lots of raw samples of liver tripe steaks , lamb lung cubes , taffy’s , and pizzles were delivered on ice to Texas Tech University’s Experimental Sciences Building . Fifteen samples from each lot of products were inoculated with a four -strain Salmonella cocktail at 102 -5 CFU /g . After a 30 -min attachment period , five control samples were sampled for initial concentration . Remaining samples were cooked in accordance with the standard cooking procedure established by the company . Before and after cooking , samples were serially diluted and plated onto xylose lysine deoxycholate agar (XLD ) with a tryptic soy agar overlay for injured cells . If no colonies were present on XLD plates , detection was performed by the BAX system and immunomagnetic separation (IMS ) with Remel Salmonella agglutination kit for confirmation . Statistical analysis was performed using SAS program with a significance level of α = 0 .05 . Cooking reduced (P < 0 .01 ) Salmonella of lamb lung cubes by 2 .85 log with one positive sample after cooking ( <10 CFU /g present ) . In addition , cooking reduced (P < 0 .01 ) Salmonella of liver tripe steaks by 3 .11 log , taffy’s by 2 .85 log , and pizzles by 5 .47 log , leaving no positive samples after cooking . A baseline study was performed for pizzles and compared between two groups (ice vs . normal ) . No difference between the groups (P > 0 .05 ) at 2 .59 logs for normal with no BAX positives and 2 .46 logs for iced with 2 BAX positives . The processing procedures were validated by inoculation challenge study with an initial inoculum of 6 .95 logs resulting in a complete reduction after cooking (P < 0 .01 ) . A similar inoculation challenge was performed on bones used for dog treats including femurs , white knuckle bones , large shank bones , and twin hooves . Cooking reduced (P < 0 .01 ) Salmonella of femurs by 3 .86 log , large shank bones by 5 .77 log , and twin hooves by 4 .53 log , and no positive samples were detected after cooking . Furthermore , cooking reduced (P < 0 .01 ) Salmonella of white knuckle bones by 3 .62 log , but one positive sample was detected after cooking . Based on these results , modification to the processing and cooking procedures for taffy’s and white knuckle bones was recommended to ensure safeness during times of high contamination . The results from the inoculation challenge suggest that the processing and cooking procedures would be effective if a high level of Salmonella contamination occurred .
URI: http : / /hdl .handle .net /2346 /45377
Date: 2012-05


Validation of dog treats and bones for the presence of Salmonella through in-plant analysis and inoculation challenge studies. Master's thesis, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /45377 .

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