P1-131 Application of Elevated Hydrostatic Pressure for Inactivation of Wild-type and Rifampicin-resistant Phenotypes of Cronobacter sakazakii

Monday, July 10, 2017
Exhibit Hall (Tampa Convention Center)
Eleonora Troyanovskaya , Public Health Microbiology Laboratory, Tennessee State University , Nashville , TN
Abimbola Allison , Public Health Microbiology Laboratory, Tennessee State University , Nashville , TN
Shahid Chowdhury , Public Health Microbiology Laboratory, Tennessee State University , Nashville , TN
Aliyar Fouladkhah , Public Health Microbiology Laboratory, Tennessee State University , Nashville , TN
Introduction: Infections caused by Cronobacter sakazakii are often fatal to infants born premature, those younger than two months, and infants with weakened immune system. Application of emerging technologies could assure better control of this pathogen in the infant formula manufacturing environment.

Purpose: The current study investigated effects of elevated hydrostatic pressure on the cell reduction and inactivation rate of wild-type (WT) and spontaneous rifampicin-resistant (RR) phenotypes of Cronobacter sakazakii.

Methods:   Various times (0 to 9 minutes) and intensity levels (0 to 380 MPa) of elevated hydrostatic pressure were investigated for inactivation of a 4-strain mixture of WT and RR Cronobacter sakazakii, inoculated into Tryptic Soy Broth (TSB) and TSB supplemented with rifampicin, respectively. The experiment was conducted at 4ºC, in two biologically independent repetitions, as blocking factors of a randomized complete block design, containing three repetitions per time/pressure/phenotype within each block. Study data was analyzed by the SAS generalized linear model for Tukey- and Dunnett-adjusted ANOVA. The inactivation Kmax, 4D, and D-values were derived from the best-fitted (maximum R2) model obtained by GInaFiT software.

Results: At 380 MPa (0 to 9 minutes), D-values of 1.73 and 1.40, 4D of 6.58 and 5.76, and inactivation Kmax of 1.35±0.2 and 1.61±0.1 were observed for WT and RR phenotypes, respectively. Control counts of 7.54±0.5 and 7.58±0.3 log CFU/mL were reduced (P< 0.05) to 1.90±0.5 and <1.07±0.4 after 9 minutes of treatment at 380 MPa for WT and RR phenotypes, respectively. Treatments shorter than three minutes and below 240 MPa were less efficacious (P≥ 0.05) for reduction of the pathogen in vast majority of the tested intervals.

Significance: This study showed that greater than five-log Cronobacter sakazakii reductions are achievable, as the result of optimized high pressure pasteurization. The WT and RR phenotypes of the pathogen showed comparable sensitivity to pressure and inactivation rates and thus could be used interchangeably in microbiological challenge studies.