Residual concentrations of antimicrobial growth promoters in poultry litter favour plasmid conjugation among Escherichia coli

Abstract

Considering that plasmid conjugation is a major driver for the dissemination of antimicrobial resistance in bacteria, this study aimed to investigate the effects of residual concentrations of antimicrobial growth promoters (AGPs) in poultry litter on the frequencies of IncFII‐FIB plasmid conjugation among Escherichia coli organisms. A 2 × 5 factorial trial was performed in vitro, using two types of litter materials (sugarcane bagasse and wood shavings) and five treatments of litter: non‐treated (CON), herbal alkaloid sanguinarine (SANG), AGPs monensin (MON), lincomycin (LCM) and virginiamycin (VIR). E. coli H2332 and E. coli J62 were used as donor and recipient strains, respectively. The presence of residues of monensin, lincomycin and virginiamycin increased the frequency of plasmid conjugation among E. coli in both types of litter materials. On the contrary, sanguinarine significantly reduced the frequency of conjugation among E. coli in sugarcane bagasse litter. The conjugation frequencies were significantly higher in wood shavings compared with sugarcane bagasse only in the presence of AGPs. Considering that the presence of AGPs in the litter can increase the conjugation of IncFII‐FIB plasmids carrying antimicrobial resistance genes, the real impact of this phenomenon on the dissemination of antimicrobial resistant bacteria in the poultry production chain must be investigated.

Conditions Necessary for the Transfer of Antimicrobial Resistance in Poultry Litter

“…Others have reported the impact of donor strain background on plasmid transfer [ 69 , 74 , 80 , 81 ]. Plasmid transfer has been previously reported in poultry bedding material where conjugation frequencies varied depending on bedding or presence of inhibitory chemical residues [ 83 , 84 ]. Guan et al reported plasmid transfer but with a higher rate in chicken manure than compost where donor and recipient cell abundance was affected by compost temperature [ 85 ].…”

Is the Use of Monensin Another Trojan Horse for the Spread of Antimicrobial Resistance?

“…The presence of residues of MON, lincomycin and virginiamycin increased the frequency of plasmid conjugation among E. coli in both types of litter materials (sugarcane bagasse and wood shavings). In addition, the conjugation frequencies were significantly higher in wood shavings compared to sugarcane bagasse in the presence of antimicrobial growth promoters [58].…”

“…The process of plasmid conjugation represents the main driver through which bacteria can transfer genes that confer resistance to other bacteria, contributing to the dissemination of cross-resistance to critically important antimicrobials. A recent study well documented the effects of residual concentrations of different antimicrobial growth promoters, including MON, in poultry litter on the frequencies of IncFII-FIB plasmid conjugation, which harbors genes conferring resistance to amphenicols, aminoglycosides, β-lactams, macrolides, tetracyclines, trimethoprim and sulphonamides [57] among Escherichia coli (E. coli) organisms [58]. The presence of residues of MON, lincomycin and virginiamycin increased the frequency of plasmid conjugation among E. coli in both types of litter materials (sugarcane bagasse and wood shavings).…”