RESUMO
BACKGROUND: Polymyxins have re-entered use against problem Gram-negative bacteria. Resistance rates are uncertain, with estimates confounded by selective testing. METHODS: The BSAC Resistance Surveillance Programme has routinely tested colistin since 2010; we reviewed data up to 2017 for relevant Enterobacterales (n = 10â¯914). Unexpectedly frequent resistance was seen among the Enterobacter cloacae complex isolates (n = 1749); for these, we investigated relationships to species, genome, carbon source utilization and LPS structure. RESULTS: Annual colistin resistance rates among E. cloacae complex isolates were 4.4%-20%, with a rising trend among bloodstream organisms; in contrast, annual rates for Escherichia coli and Klebsiella spp. (including K. aerogenes) generally remained <2%. WGS split the E. cloacae complex isolates into seven genogroup clusters, designated A-G. Among isolates assigned to genogroups A-D, 47/50 sequenced were colistin resistant, and many of those belonging to genogroups A-C identified as E. asburiae. Isolates belonging to genogroups E-G consistently identified as E. cloacae and were rarely (only 3/45 representatives sequenced) colistin resistant. Genogroups F and G, the predominant colistin-susceptible clusters, were metabolically distinct from other clusters, notably regarding utilization or not of l-fucose, formic acid, d-serine, adonitol, myo-inositol, l-lyxose and polysorbates. LPS from resistant organisms grown without colistin pressure lacked substitutions with 4-amino-arabinose or ethanolamine but was more structurally complex, with more molecular species present. CONCLUSIONS: Colistin resistance is frequent in the E. cloacae complex and increasing among bloodstream isolates. It is associated with: (i) particular genomic and metabolic clusters; (ii) identification as E. asburiae; and (iii) with more complex LPS architectures.
Assuntos
Colistina , Infecções por Enterobacteriaceae , Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Colistina/farmacologia , Farmacorresistência Bacteriana , Enterobacter cloacae/genética , Infecções por Enterobacteriaceae/tratamento farmacológico , Infecções por Enterobacteriaceae/epidemiologia , Genótipo , Humanos , Testes de Sensibilidade MicrobianaRESUMO
The European Antimicrobial Susceptibility Surveillance in Animals (EASSA) program collects zoonotic and commensal bacteria from food-producing animals at slaughter and tracks their susceptibility to medically important antibiotics. Results of commensal enterococci species (2013-2014) are presented here. Intestinal content from cattle, pigs and chickens were randomly sampled (5-6 countries/host; ≥4 abattoirs/country; 1 sample/animal/farm) for isolation of enterococci, MICs of 9 antibiotics were assessed by CLSI agar dilution in a central laboratory. Clinical breakpoints (CLSI) and epidemiological cut-off values (EUCAST) were applied for data interpretation. In total 960 Enterococcus faecium and 779 Enterococcus faecalis strains were recovered. Seven porcine E. faecium/faecalis strains of Spanish origin were resistant to linezolid. One avian E. faecalis and one porcine E. faecium strain were non-wild type (MICs 8â¯mg/L) to daptomycin. Clinical vancomycin resistance was absent; 2 poultry E. faecium and 1 bovine E. faecalis strains were non-wild type, all with MICs of 8â¯mg/L. None of the strains tested were clinically resistant to tigecycline. Little clinical resistance to ampicillin or gentamicin was observed. Clinical resistance of E. faecium to quinupristin/dalfopristin was slightly higher (2.2-12.0%) but 61.9-83.2% of the strains were classified as non-wild type. Very high percentages resistance to tetracycline (67.4-78.3%) and to erythromycin (27.1-57.0%) were noted for both E. faecium and E. faecalis in pigs and chickens compared to cattle (5.2-30.4 and 9.0-10.4%, respectively). Similar non-wild type results were observed for E. hirae (nâ¯=â¯557), E. durans (nâ¯=â¯218) and E. casseliflavus (nâ¯=â¯55) including percentage non-wild type for daptomycin, linezolid, tigecycline being absent and for vancomycin low. For these species percentage non-wild type to erythromycin was lower as compared to E. faecalis/faecium. This pan-EU survey shows high variability in antibiotic susceptibility of commensal enterococci from healthy food animals. Clinical resistance to critically important antibiotics for human medicine was absent or low, except for erythromycin.