Microbial dynamics in rearing trials of Hermetia illucens larvae fed coffee silverskin and microalgae

Occurrence of Antibiotic Resistance Genes in Hermetia illucens Larvae Fed Coffee Silverskin Enriched with Schizochytrium limacinum or Isochrysis galbana Microalgae

“…Since a strong correlation between the H. illucens gut microbiome and resistome has been reported in a study performed by Liu et al [10], similar associations between the AR genes detected in H. illucens larvae in the present study and their microbiota highlighted by Osimani et al [38] could be hypothesized. Indeed, Osimani et al [38] recently reported the prevalence of Paenibacillus in larvae reared on basal Cs substrates, whereas Morganella, followed by Paenibacillus, Lysinibacillus, and Enterococcus, prevailed in H. illucens reared on substrates enriched with I. galbana. Multidrug-resistant species from the Morganella genus that are able to spread AR genes horizontally among the same or different species have been reported by Liu et al [46].…”

“…To the author's knowledge, no studies have been performed on the presence of antibiotic residues or on the occurrence of AR genes in coffee silverskin or microalgae-based substrates, whereas a similar study investigating the incidence of AR genes in organic wheatmeal used for the rearing of edible mealworms reported the exclusive presence of tetracycline tet(S) and tet(K) genes [20]. A very recent study focused on the microbial dynamics of the same rearing substrates analyzed in the present study reported the massive presence of lactic acid bacteria (LAB) belonging to the Lactobacillus, Leuconostoc, and Weissella genera [38]. In the study of Osimani et al [38], the prevalence of Leuconostoc in the basal Cs substrate and substrates supplemented with S. limacinum was reported; moreover, the prevalence of Weissella in substrates supplemented with I. galbana was observed [38].…”

“…A very recent study focused on the microbial dynamics of the same rearing substrates analyzed in the present study reported the massive presence of lactic acid bacteria (LAB) belonging to the Lactobacillus, Leuconostoc, and Weissella genera [38]. In the study of Osimani et al [38], the prevalence of Leuconostoc in the basal Cs substrate and substrates supplemented with S. limacinum was reported; moreover, the prevalence of Weissella in substrates supplemented with I. galbana was observed [38]. Although LAB have been recognized as safe with a QPS (qualified presumption of safety) status given by the EFSA [39], the frequent detection of LAB carrying AR genes that can be horizontally transferred to pathogens through the food chain is of great concern [40].…”

“…Despite the growing interest of the scientific community in H. illucens larvae for bioconversion and bioremediation, limited information is available on safety aspects regarding its gut microbiota [41]. Among the limited number of studies investigating the composition of the H. illucens gut microbiota, only a few have focused on the effect of diet on its composition and they have shown that the gut microbiota is strongly influenced by the diet, but a stable core microbiota is also present [38,[41][42][43]. Another important safety aspect neglected in most of the studies performed on H. illucens larvae is the occurrence of antibiotic-resistant bacteria and their AR genes, which in turn could be transferred to fish or livestock destined for human consumption.…”

“…Little is known about the microbiota of frass collected during the rearing of H. illucens [22,38,41,49], and only two studies investigated the occurrence of AR genes in insect frass collected during the rearing of H. illucens [22] and T. molitor [20] larvae. In the present study, a high contamination level of frass by bacteria carrying the AR genes under study was assumed.…”