Prevalence, Levels, and Viability of Salmonella in and on Raw Chicken Livers

Abstract

We surveyed chicken livers from various sources for the presence and levels of Salmonella. The pathogen was recovered from 148 (59.4%) of 249 chicken livers purchased at retail stores in Delaware, New Jersey, and Pennsylvania over about a 9-month period. Positive samples harbored Salmonella at levels of 6.4 most probable number (MPN)/g to 2.4 log CFU/g. The percentage of Salmonella-positive livers purchased at retail outlets in New Jersey (72%, 59 of 82 livers) was significantly higher (P < 0.05) than the percentage for livers purchased in Delaware (48%, 36 of 75 livers); however, this percentage was not significantly different (P > 0.05) from that for livers purchased in Pennsylvania (57.6%, 53 of 92 livers). The pathogen was also recovered more often (P = 0.019) from livers that were packaged by retailers (81 of 121 livers, 66.9%) than from livers packaged directly by processors (67 of 128 livers, 52.3%). In related studies, 12 (5.8%) of 207 chicken livers harvested from birds on a research farm tested positive for Salmonella at levels of 0.4 to 2.2 MPN/g. The recovery rate of Salmonella was 4.4% (6 of 135 livers) from livers with the gall bladder attached and 8.3% (6 of 72 livers) from livers when the gall bladder was removed at harvest on the research farm. We also quantified the levels of a nine-strain cocktail (ca. 6.5 log CFU/g) of Salmonella strains inoculated externally onto or internally into livers both before and after extended cold storage. Storage for at least 2 days at 4°C or 15 days at -20°C resulted in a decrease of about 1.0 log CFU/g in pathogen levels. Given the relatively high recovery rate (ca. 6.0 to 60.0%) and high (possibly illness causing) levels (0.4 MPN/g to 2.4 CFU/g) of Salmonella associated with chicken livers in the present study, further interventions for processors are needed to lower the prevalence and levels of this pathogen on poultry liver.

Keywords: Chicken liver; Poultry; Prevalence; Pâté; Retail survey.