PFGE-typing of Enterobacter cloacae, Klebsiella pneumoniae and Leclercia adecarboxylata isolates from an infant formula processing plant

Abstract

The family of Enterobacteriaceae is a useful indicator for hygiene conditions in food production facilities and food products. For powdered infant formula (PIF) the absence of Enterobacteriaceae in 100 g is required. Nevertheless, occasionally Enterobacteriaceae can be detected. A recent study concentrated on the occurrence of a specific foodborne pathogen out of the Enterobacteriaceae family, Cronobacter spp., in PIF manufacturing facilities in order to investigate clonal persistence and identify possible transmission routes. The aim of this study was to genotype isolates from frequently found other species within the family of Enterobateriaceae in order to elucidate and trace back transmission routes not only limited on Cronobacter spp. In total 216 isolates from three different species (Enterobacter (E.) cloacae, Klebsiella (K.) pneumoniae and Leclercia (L.) adecarboxylata) were genotyped. The isolates originated from raw ingredients, environment and products of an infant formula processing plant. Restriction digest with Xbal revealed discriminative PFGE patterns consisting of 10-20 bands for all three species. Heat sensitive additives could be traced back as contamination source for products. Furthermore, the production environment was found as a reservoir for persisting strains. Showing analogy to the situation described for Cronobacter spp., especially E. cloacae that can be found in the same niches as Cronobacter spp. but more frequently might therefore be used for hygiene monitoring along the processing chain. Certain genotypes of E. cloacae, that are able to persist within the factory environment, might possess special properties as e. g. enhanced desiccation tolerance enabling them to survive the harsh environmental conditions.