Evaluation of Violet Red Bile Glucose agar specificity for Enterobacteriaceae isolation in raw goat milk

Abstract

Introduction: Coliforms have been used over the years as indicator microorganisms for microbiological quality. However, several studies report the lack of direct correlation between their presence and that of pathogens in the evaluation of food safety, leading to the suggestion of new analysis proposals, such as the search for total enterobacteria, which includes all members of the Enterobacteriaceae family. Objective: This study aimed to determine the population of enterobacteria in raw goat milk samples based on the microbiological criteria suggested by the National Health Surveillance Agency - Ministry of Health (Anvisa - MS) - Public Consultation Noº 542 of July 17, 2018 for Pasteurized milk samples. Method: 21 samples from small producers from different regions of the state of Rio de Janeiro were used. Isolates were obtained from inoculation on VRBG agar according to ISO 21528-2 and identified by Matrix Associated Laser Desorption-Ionization – Time of Flight (MALDI/TOF) mass spectrometry. Results: Of the 222 isolates identified, only 26.6% belonged to the Enterobacteriaceae family. Another 61.3% belonged to the Pseudomonas genus, 4.5% to the Acinetobacter genus and 7.6% were Stenotrophomonas maltophilia. Although there are no microbiological parameters in Anvisa-MS RDC Nº 12 of January 2, 2001 for raw milk, the results of isolation on VBRG agar led to the investigation of other studies with similar findings regarding isolation of VRBG bacteria from goat and bovine milk samples. Conclusions: Detection in VRBG agar of non-Enterobacteriaceae-negative oxidase bacteria, such as those of the genus Acinetobacter, suggests the need for a debate on the methodology indicated by ISO 21528-2 for enumeration of enterobacteria, as the new regulation on standard microbiological data for food will no longer use the coliform group, but the Enterobacteriaceae/g or mL count, as an indicator.