Azithromycin resistance in Escherichia coli and Salmonella from food-producing animals and meat in Europe.

OBJECTIVES: To characterize the genetic basis of azithromycin resistance in Escherichia coli and Salmonella collected within the EU harmonized antimicrobial resistance (AMR) surveillance programme in 2014-18 and the Danish AMR surveillance programme in 2016-19. METHODS: WGS data of 1007 E. coli [165 azithromycin resistant (MIC > 16 mg/L)] and 269 Salmonella [29 azithromycin resistant (MIC > 16 mg/L)] were screened for acquired macrolide resistance genes and mutations in rplDV, 23S rRNA and acrB genes using ResFinder v4.0, AMRFinder Plus and custom scripts. Genotype-phenotype concordance was determined for all isolates. Transferability of mef(C)-mph(G)-carrying plasmids was assessed by conjugation experiments. RESULTS: mph(A), mph(B), mef(B), erm(B) and mef(C)-mph(G) were detected in E. coli and Salmonella, whereas erm(C), erm(42), ere(A) and mph(E)-msr(E) were detected in E. coli only. The presence of macrolide resistance genes, alone or in combination, was concordant with the azithromycin-resistant phenotype in 69% of isolates. Distinct mph(A) operon structures were observed in azithromycin-susceptible (n = 50) and -resistant (n = 136) isolates. mef(C)-mph(G) were detected in porcine and bovine E. coli and in porcine Salmonella enterica serovar Derby and Salmonella enterica 1,4, [5],12:i:-, flanked downstream by ISCR2 or TnAs1 and associated with IncIγ and IncFII plasmids. CONCLUSIONS: Diverse azithromycin resistance genes were detected in E. coli and Salmonella from food-producing animals and meat in Europe. Azithromycin resistance genes mef(C)-mph(G) and erm(42) appear to be emerging primarily in porcine E. coli isolates. The identification of distinct mph(A) operon structures in susceptible and resistant isolates increases the predictive power of WGS-based methods for in silico detection of azithromycin resistance in Enterobacterales.

Detection of Salmonella Reservoirs in Birds of Prey Hosted in an Italian Wildlife Centre: Molecular and Antimicrobial Resistance Characterisation.

In the European Union, salmonellosis is one of the most important zoonoses reported. Poultry meat and egg products are the most common food matrices associated with Salmonella presence. Moreover, wild and domestic animals could represent an important reservoir that could favour the direct and indirect transmission of pathogens to humans. Salmonella spp. can infect carnivorous or omnivorous wild birds that regularly ingest food and water exposed to faecal contamination. Birds kept in captivity can act as reservoirs of Salmonella spp. following ingestion of infected prey or feed. In this paper, we describe the isolation of different Salmonella serovars in several species of raptors hosted in aviaries in an Italian wildlife centre and in the raw chicken necks used as their feed but intended for human consumption. Characterisations of strains were carried out by integrating classical methods and whole genome sequencing analysis. The strains of S. bredeney isolated in poultry meat and birds belonged to the same cluster, with some of them being multidrug-resistant (MDR) and carrying the Col(pHAD28) plasmid-borne qnrB19 (fluoro)quinolone resistance gene, thus confirming the source of infection. Differently, the S. infantis found in feed and raptors were all MDR, carried a plasmid of emerging S. infantis (pESI)-like plasmid and belonged to different clusters, possibly suggesting a long-lasting infection or the presence of additional undetected sources. Due to the high risk of fuelling a reservoir of human pathogens, the control and treatment of feed for captive species are crucial.