No abstract

Cronobacter spp. (formerly Enterobacter sakazakii) are emerging, opportunistic pathogens that are linked with food-borne infections in neonates and infants. In the present study, 291 samples of food, 36 samples from a dairy farm and 140 samples of dust from vacuum cleaners were examined for the presence of Cronobacter spp. using chromogenic media and biochemical tests. Altogether, 72 Cronobacter spp. strains were isolated in accordance with the reference standard ČSN P ISO/TS 22964 (2006). No Cronobacter spp. strains were detected in 10 samples of infant milk formula or in samples from a dairy farm. Twelve out of 20 positive food samples were dry products. The incidence of Cronobacter spp. in instant and powdered products and spices (12 positive isolates out of 82 samples) was significantly higher than that in other foods (P = 0.002), but lower than that in samples of dust (52 isolates; P< 0.001). The incidence of Cronobacter spp. in dust from restaurants, bars and hotels (13 positive isolates in 20 samples) was significantly higher than that in dust from households (P = 0.010). The polymerase chain reaction assay for the species-specific detection of the rpoB gene was performed in 49 isolates. Thirty-four Cronobacter spp. isolates were identified as Cronobacter sakazakii, nine isolates as Cronobacter malonaticus and one isolate as Cronobacter turicensis.

The presence of phytase activity was demonstrated in 26 strains of rabbit cecal bacteria. In 25 strains a low phytase activity, 0.10-0.62 micromol phosphate released per min per mg protein, was found. High activity (2.61 micromol/min per mg protein) was found in the strain PP2 identified as Enterococcus hirae. Phytase activity was cell-associated, being higher in the cell extract than in the cell walls. Extracellular phytase activity and cell-associated phosphatase activity were not detected. Phytase activity was optimal around pH 5.0, which is below the physiological cecal pH range. The K (m) determined using the Lineweaver-Burk plot was 0.19 micromol/mL. Cations Fe(3+), Cu(2+) and Zn(2+) at 0.5 mmol/L decreased phytase activity in sonicated cells of E. hirae by 99.4, 90.7 and 96.5 %, respectively. In contrast, Mg(2+) increased activity by 11.0 %. Characteristics of E. hirae phytase (pH optimum, K (m), cation sensitivity) were similar to those of other bacterial phytases reported in the literature. Other bacteria with a high phytase activity may be present in the rabbit cecum but remain to be identified.

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, fi rstly using commercial ESIA agar and thereafter on Kim and Rhee-KR agar described in the literature. Phenotypic characteristics were obtained by commercial miniaturized biochemical ENTEROTEST 24 kits and the fi nal confi rmation 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 identifi ed, however, only 22 isolates (51%) were identifi ed as Cronobacter spp. with high identity scores (75-99%). The occurrence of presumptive cronobacters in environmental samples was signifi cantly 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 identifi ed by means of ENTERO24 test kits with high probability. Both phenotypic and genotypic methodology could be used for identifi cation of Cronobacter spp. and they can be combined for reliable identifi cation.