Submitted to: American Society for Microbiology Conference
Publication Type: Abstract Only
Publication Acceptance Date: 2/29/2016
Publication Date: 6/16/2016
Citation: Humayoun, S.B., Hiott, L.M., Jackson, C.R., Frye, J.G. 2016. Susceptibility of 194 Salmonella Isolates to 17 Chemicals used as Sanitizers and Biocides. American Society for Microbiology Conference. June 16-20, 2016. Boston, Massachusetts.
Technical Abstract: Salmonella is a major cause of foodborne illnesses in the United States. Meat processing facilities use a wide variety of antimicrobial interventions to reduce Salmonella contamination. The objective of this study was to determine the minimum inhibitory concentration (MIC) of sanitizers and biocides against Salmonella. The biocide used in this study were: Acidified Sodium Chlorite (ASC), Acetic acid (AA), Arsenite (ARI), Arsenate (ARA), Benzalkonium chloride (BC), Cetylpyridinium chloride (CC), Citric Acid (CA), 1,3 dibromo, 5,5 Dimethylhydantoin (DBH), Dodecyltrimethylammonium chloride (DC), Hexadecyltrimethylammonium Bromide (HB), Hexadecyltrimethylammonium Chloride (HC), Lactic acid (LA), Peroxyacetic acid (PXA), Sodium Hypochlorite (SHB), Sodium Metasilicate (SM), Trisodium phosphate (TP), Chlorhexidine (CH). 194 animal associated Salmonella isolates representing 84 serotypes were assayed for susceptibility. Isolates were grown on Blood Agar plates. Colonies were picked and suspended in Mueller Hinton (MH) broth, and inoculum concentration was adjusted to 10^5 cells/ml following protocols for SensititreTM (ThermoFisher, Pittsburgh, PA) MIC assay was done in 96 well plates using two-fold serial dilutions of chemicals in MH. Plates were incubated at 37ºC for 24 hrs and turbidity was used as indicator of bacterial growth. Results were recorded using the Sensititre vision system. The lowest concentration at which no growth was observed was reported as the MIC to the chemical in µg/ml. The median MIC (µg/ml) for 194 isolates was: DC =256, CC=40, LA=7556, CA=6316, BC =40, AA =1640, TP =37953, HB=82, HC =78, ARI =30, ARA 410, SM =120640, SHB=55500, PXA=884, ASC = 1272, DB =1250, and CH =4.0. Most of the isolates showed similar susceptibilities to each chemical with MICs within +/- one two-fold dilution from the median MIC. However, 16 Salmonella isolates had a four-fold higher MIC than the median MIC to Arsenate and 19 isolates had a four-fold higher MIC to Arsenite. Additionally, 5 isolates had a four-fold lower MIC to Arsenate and one isolate also had a four-fold lower MIC to Arsenite. This variability in MIC may indicate reduced susceptibility or hyper susceptibility in some Salmonella isolates to these compounds.