The effect of previous life cycle stage on the growth kinetics, morphology and antimicrobial resistance of Salmonella Typhimurium DT104 in brain heart infusion and ground chicken extract

Authors: HAWKINS, J.L. - University Of Maryland Eastern Shore (UMES); Uknalis, Joseph; Oscar, Thomas; SCHWARTZ, J.G. - University Of Maryland Eastern Shore (UMES); VIMINI, B. - Perdue Farms; PARVEEN, S. - University Of Maryland Eastern Shore (UMES)

Submitted to: bioRxiv
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/21/2018
Publication Date: 5/21/2018
Citation: Hawkins, J., Uknalis, J., Oscar, T.P., Schwartz, J., Vimini, B., Parveen, S. 2018. The effect of previous life cycle stage on the growth kinetics, morphology and antimicrobial resistance of Salmonella Typhimurium DT104 in brain heart infusion and ground chicken extract. bioRxiv. Available:https://doi.org/10.1101/326579. https://doi.org/10.1101/326579.
DOI: https://doi.org/10.1101/326579

Interpretive Summary: Although the poultry industry does a good job of providing consumers with products that contain low levels of Salmonella, if the product is not properly stored and handled, the few cells of Salmonella present can quickly grow to high and dangerous levels. Models that predict the growth of Salmonella on or in poultry products are valuable tools for helping assess the risk of foodborne illness from poultry products that are improperly stored and handled. These models can be improved by identifying new variables that significantly influence the growth of Salmonella. In the current study, a new variable (i.e. previous life cycle phase) was identified that altered the growth of Salmonella. Inclusion of this variable in future growth models will help to improve their ability to accurately predict Salmonella growth and thus, protect public health.

Technical Abstract: Growth models are predominately used in the food industry to estimate the potential growth of select microorganisms under environmental conditions. The growth kinetics, cellular morphology and antimicrobial susceptibility were studied throughout the life cycle of Salmonella Typhimurium. The effect of the previous life cycle phase (late log phase [LLP], early stationary phase [ESP], late stationary phase [LSP] and early death phase [EDP]) of Salmonella after reinoculation in brain heart infusion broth (BHI), ground chicken extract (GCE) and BHI at pH 5, 7 and 9 and salt concentrations 2, 3 and 4% was investigated. The growth media and previous life cycle phase had significant effects on the lag time ('), specific growth rate (µmax) and maximum population density (Ymax). At 2% and 4% salt concentration the LLP had the significantly (P<0.05) fastest µmax (1.07 and 0.69 log CFU/mL/h, respectively). As the cells transitioned from the late log phase (LLP) to the early death phase (EDP), the ' significantly (P<0.05) increased. At pH 5 and 9 the EDP had a significantly (P<0.05) lower Ymax than the LLP, ESP and LSP. As the cells transitioned from a rod shape to a coccoid shape in the EDP, the cells were more susceptible to antimicrobial agents. The cells regained their resistance as they transitioned back to a rod shape from the EDP to the log and stationary phase. The results of this study demonstrate that the previous life cycle should be considered when developing growth models of foodborne pathogens to better ensure the safety of poultry and poultry products.