Matrix-assisted laser desorption ionization–time of flight mass spectrometry reveals Enterococcus and Enterobacter spp. in major insect species involved in food security with resistance to common antibiotics

Abstract

Stored-product insects can transfer a wide range of serious pathogens involved in human health. The close contact of these insects with the food production chain makes these species extremely dangerous as carriers of severe infections. In addition, pathogenic bacteria, such as members of Enterococcus, are often resistant to antibiotics commonly used for human therapy. Herein we identified, using Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS), Enterococcus and coliform species isolated from 17 strains of different insect species associated with durable stored products. The antibiotic susceptibility of the isolated strains was also evaluated. MALDI-TOF MS revealed mainly the presence of Enterococcus (E. faecium, E. phoeniculicola and E. casseliflavus) and Enterobacter (Eb. cloacae and Eb. asburiae). E. casseliflavus was resistant to all antibiotics tested, while E. faecium and E. phoeniculicola were resistant to sulphonamides. Among E. faecium isolates, approx. 20% were found to be resistant to tetracycline, while Eb. cloacae and Eb. asburiae showed resistance to erythromycin. The current series of data clearly indicates that certain bacteria of the genera Enterococcus and Enterobacter are very common in stored-product insects, and, under certain circumstances, may seriously endanger public health, through potential introduction of antibiotic resistance. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.