Distribution of Transferable Antibiotic Resistance Genes in Laboratory-Reared Edible Mealworms (Tenebrio molitor L.).

Andrea Osimani,Cristiana Garofalo,Francesca Clementi,Roberta Galarini,Paola Riolo,Lucia Aquilanti,Nunzio Isidoro,Simone Moretti,Federica Cardinali,Nino Loreto,Vesna Milanović,Franco Tonucci,Annalisa Petruzzelli,Eleonora Micci,Sara Ruschioni

doi:10.3389/fmicb.2018.02702

Abstract

In the present study, the distribution of antibiotic resistance genes in laboratory-reared fresh mealworm larvae (Tenebrio molitor L.), their feeding substrates (carrots and wheatmeal), and frass was assessed. Microbial counts on selective media added with antibiotics highlighted the presence of lactic acid bacteria resistant to ampicillin and vancomycin and, more specifically, enterococci resistant to the latter antibiotic. Moreover, staphylococci resistant to gentamicin, erythromycin, tetracycline, and vancomycin were detected. Enterobacteriaceae resistant to ampicillin and gentamicin were also found, together with Pseudomonadaceae resistant to gentamicin. Some of the genes coding for resistance to macrolide-lincosamide-streptogramin B (MLSB) [erm(A), erm(C)], vancomycin [vanA, vanB], tetracycline [tet(O)], and β-lactams [mecA and blaZ] were absent in all of the samples. For the feeding substrates, organic wheatmeal was positive for tet(S) and tet(K), whereas no AR genes were detected in organic carrots. The genes tet(M), tet(K), and tet(S) were detected in both mealworms and frass, whereas gene aac-aph, coding for resistance to amynoglicosides was exclusively detected in frass. No residues for any of the 64 antibiotics belonging to 10 different drug classes were found in either the organic wheatmeal or carrots. Based on the overall results, the contribution of feed to the occurrence of antibiotic resistance (AR) genes and/or antibiotic-resistant microorganisms in mealworm larvae was hypothesized together with vertical transmission via insect egg smearing.

Highlights

“Them insects eats up every blessed green thing that do grow, and us farmers starves
The novelty of this approach relies on the possibility of evaluating the occurrence of antibiotic resistance (AR) under controlled rearing conditions without any selective pressure exerted by antibiotics
Such an approach allowed to exclude any possible interference of insect manipulation and/or processing on the occurrence of transferable AR genes and antibiotic-resistant microorganisms in edible insects, constituting an advancement on the knowledge in respect with the available literature on the same topic (Milanovicet al., 2016; Osimani et al, 2017b,c; Vandeweyer et al, 2019)

Summary

Introduction

“Them insects eats up every blessed green thing that do grow, and us farmers starves. Several studies have already been focused on the microbiota of edible insects through conventional microbiological analyses and advanced DNA-based techniques (Simpanya et al, 2000; Banjo et al, 2006; Klunder et al, 2012; Stoops et al, 2016; Garofalo et al, 2017; Osimani et al, 2017a; Vandeweyer et al, 2017) The results of these studies highlighted the presence of potential human pathogens, suggesting the need for a deeper investigation of the correlation between the microbiota and insect rearing conditions

Methods

Results

Conclusion