Prevalence of antibiotic resistance pathogens in online fresh-cut fruit from Chongqing, China and controlling Enterococcus faecalis by bacteriocin GF-15

Abstract

Consuming fresh-cut fruits from online platform has become a common lifestyle in China, especially under the background of COVID-2019 pandemic. To investigate microbial safety of online fresh-cut fruits, pathogens were isolated and their antibiotic resistance was characterized. Results showed that Enterococcus faecalis, Enterococcus faecium, Morganella morganii, Klebsiella pneumoniae, Klebsiella aerogenes, Klebsiella variicola, Proteus mirabilis, Stenotrophomonas maltophilia, Microbacterium paraoxydans, and Achromobacter xylosoxidans were isolated from online fresh-cut fruits. These pathogens showed resistance to tetracyclines, aminoglycosides, beta-lactams, quinolones, macrolides, etc. After genome sequencing, antibiotic resistance genes lsa(A), tet(M), aph(3′)-IIc, aac(6′)-Ii, qnrD1, OqxA, bla(CMY), msr(C), sul2, dfrA14, mdf(A), etc. were identified in these pathogens. A novel bacteriocin GF-15 was used to control E. faecalis which occupied the highest abundance in online fresh-cut fruits. MIC values of GF-15 to E. faecalis strains were 8–16 μM. The growth of E. faecalis can be totally inhibited by ≥ 4 × MIC GF-15 treatment. GF-15 had bactericidal mode and damaged cell envelope of E. faecalis. Tracing by FITC labelled GF-15 showed that it located both on cell envelope and in cytoplasm. On cell envelope, GF-15 led to great pore-formation and strong membrane depolarization. After entering cytoplasm, it induced reactive oxygen species production.