Application of Elevated Hydrostatic Pressure for Inactivation of Wild-Type and Rifampicin-Resistant Phenotypes of Cronobacter sakazakii
Infections caused by Cronobacter sakazakii are often fatal in 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 manufacturing environment.
Current study investigated effects of elevated hydrostatic pressure on cell reduction and inactivation rate of wild-type (WT) and spontaneous rifampicin-resistant (RR) phenotypes of Cronobacter sakazakii.
Various times (0 to 9 minutes) and intensity levels (0 to 380 MPa) of elevated hydrostatic pressure were investigated for inactivation of 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 4 ºC, 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 was analyzed by generalized linear model of SAS for Tukey- and Dunnett-adjusted ANOVA. The inactivation Kmax, 4D, and D-value were derived from the best-fitted (maximum R2) model obtained by GInaFiT software.
At 380 MPa (0 to 9 minutes), D-value 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 the pathogen were 7.54±0.5 and 7.58±0.3 log CFU/mL and 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.
Results of this study showed over 5-log reduction of Cronobacter sakazakii is achievable as the result of optimized high pressure pasteurization. The WT and RR phenotypes of the pathogen showed comparable sensitivity and inactivation rate, thus could be used interchangeably in microbiological challenge studies.