Microbial communities and food safety aspects of crickets (Acheta domesticus) reared under controlled conditions

Abstract

In an approach combining microbiological culture methods with high-throughput sequencing, this study investigated the microbial communities (bacteria, moulds and yeasts) in Swedish-produced edible crickets (Acheta domesticus) reared in a controlled environment. The effects of different feeds on microbial loads and populations in crickets were also studied. The crickets used were third-generation offspring from wild-caught individuals from Sweden, which are adapted to grow in a laboratory environment. The efficiency of rinsing to decrease microbial load was evaluated not obtaining a significant decrease of plating counts for total aerobic counts (TAC) and Enterobacteriaceae. Crickets were divided into three batches and fed different diets (control feed, early-cut red clover hay (ECH), late-cut fresh red clover (LCF)) for 62 days. Bacterial numbers (TAC and Enterobacteriaceae) on whole raw crickets ranged between 7 and 8 log cfu/g. Pre-rinsing in water did not reduce these levels (P=0.19). All batches tested negative for the food-borne bacteria Salmonella, Listeria monocytogenes, Bacillus cereus and Clostridium perfringens. The mean mould count for crickets fed control feed was 2.8 log cfu/g, while the values for crickets fed ECH and LCF were 4.2 and 4.5 log cfu/g, respectively. The dominant bacterial communities were Proteobacteria, Bacteroidetes and Firmicutes, with Firmicutes and Proteobacteria dominating in crickets fed control feed, Firmicutes dominating in crickets fed LCF and Proteobacteria dominating in crickets fed ECH. Aspergillus flavus, a fungus that is capable of producing mycotoxins, was detected in control feed and ECH reared crickets. More work is needed to identify specific food-borne pathogens in edible crickets and establish possible bacterial quality reference values, as an important step in developing microbial quality and safety parameters to ensure consumer safety.