Colistin Resistance Mechanisms in Human <i>Salmonella</i> <i>enterica</i> Strains Isolated by the National Surveillance Enter-Net Italia (2016-2018)
Background: A collection of human-epidemiologically unrelated <i>S. enterica</i> strains collected over a 3-year period (2016 to 2018) in Italy by the national surveillance Enter-Net Italia was analysed. Methods: Antimicrobial susceptibility tests, including the determination of minimal...
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| Main Authors: | , , , , , , , , |
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| Format: | Book |
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MDPI AG,
2022-01-01T00:00:00Z.
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| Summary: | Background: A collection of human-epidemiologically unrelated <i>S. enterica</i> strains collected over a 3-year period (2016 to 2018) in Italy by the national surveillance Enter-Net Italia was analysed. Methods: Antimicrobial susceptibility tests, including the determination of minimal inhibitory concentrations (MICs) for colistin, were performed. Colistin resistant strains were analysed by PCR to detect mobile colistin resistance (<i>mcr</i>) genes. In <i>mcr</i>-negative <i>S. enterica</i> serovar Enteritidis strains, chromosomal mutations potentially involved in colistin resistance were identified by a genomic approach. Results: The prevalence of colistin-resistant <i>S. enterica</i> strains was 7.7%, the majority (87.5%) were <i>S</i>. Enteritidis. <i>mcr</i> genes were identified only in one strain, a <i>S</i>. Typhimurium monophasic variant, positive for both <i>mcr-1.1</i> and <i>mcr-5.1</i> genes in an IncHI2 ST4 plasmid. Several chromosomal mutations were identified in the colistin-resistant <i>mcr</i>-negative <i>S</i>. Enteritidis strains in proteins involved in lipopolysaccharide and outer membrane synthesis and modification (RfbN, LolB, ZraR) and in a component of a multidrug efflux pump (MdsC). These mutated proteins were defined as possible candidates for colistin resistance in <i>mcr</i>-negative <i>S</i>. Enteritidis of our collection. Conclusions: The colistin national surveillance in <i>Salmonella</i> spp. in humans, implemented with genomic-based surveillance, permitted to monitor colistin resistance, determining the prevalence of <i>mcr</i> determinants and the study of new candidate mechanisms for colistin resistance. |
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| Item Description: | 10.3390/antibiotics11010102 2079-6382 |