Isolation and characterization of Cronobacter spp. from environmental and food resources

Abstract

Cronobacter spp. (formerly Enterobacter sakazakii) has been isolated from a wide range of environmental and several food sources. Cronobacter spp. is an opportunistic pathogen causing serious infection in infants, particularly neonates. The aim of this study was to isolate and characterize Cronobacter spp. from food sources (infant food, herbs and spices and vegetables) and from environmental sources as dust from vacuum cleaners. Isolation of Cronobacter spp. was performed on selective chromogenic agars, firstly using commercial ESIA agar and thereafter on Kim and Rhee-KR agar described in the literature. Phenotypic were obtained by commercial miniaturized biochemical ENTEROTEST 24 kits and the final confirmation of isolated strains was performed by molecular techniques (PCR, PCR-DGGE analysis, and 16S rDNA sequencing). Altogether, 99 samples were analyzed (47 samples of foods and 52 samples of dust). In total, 43 isolates of presumptive Cronobacter spp. were initially identified, however, only 22 isolates (51%) were identified as Cronobacter spp. with high identity scores (75-99%). The occurrence of presumptive cronobacters in environmental samples was significantly higher than in samples of food (18 out of 52 vs. 4 out of 47; P=0.003). No cronobacters were found in 17 samples of infant food, 3 isolates originated from herbs and spices, 1 isolate from spinach and 18 isolates from samples of dust (households, restaurants, dormitory rooms). It can be concluded that Cronobacter spp. is a ubiquitous pathogen contaminating food and environment. Cronobacter spp. could be well identified by means of ENTERO24 test kits with high probability. Both phenotypic and genotypic methodology could be used for identification of Cronobacter spp. and they can be combined for reliable identification.