Recovery of Cronobacter sakazakii from environmental surface swabbing materials using a 5-h enrichment procedure

Abstract

This study aimed to reduce the time taken to detect low numbers of Cronobacter sakazakii inoculated onto environmental swabs (100, 10 or 1 cfu per swab) using a simple plating procedure for application in a dairy testing laboratory. Three types of environmental swabs (Biolab FlexiSwab, gauze swabs and the Whatman SwabCheck Polywipe sponge) were inoculated with either Cron. sakazakii in single culture or Cron. sakazakii together with Citrobacter freundii. A 5-h enrichment procedure of swabs in Cronobacter enrichment broth at 37 degrees C prior to plating was then compared with no enrichment or 24-h enrichment. The 5-h enrichment procedure was as efficient at detecting Cron. sakazakii on environmental swabs at low cell concentrations (100 cfu per swab), and in pure culture or in competition with other coliforms (Citrobacter), as pre-enrichment for 24 h. This protocol was also successful in detecting 10 cfu per swab 80% of the time. The results also indicated that the type of swab selected for use in environmental safety programmes is influential on the outcome, with the FlexiSwab and gauze swabs being the most efficient swabbing materials evaluated in this study.