Genomic sequences of Streptococcus agalactiae with high-level gentamicin resistance, collected in the BSAC bacteraemia surveillance

Michel Doumith, Shazad Mushtaq, Veronique Martin, Aiysha Chaudhry, Rachael Adkin, Juliana Coehlo, Vicki Chalker, Alasdair MacGowan, Neil Woodford, David M Livermore, BSAC Resistance Surveillance Standing Committee

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Background: Like other streptococci, Streptococcus agalactiae typically has intrinsic low-level aminoglycoside resistance. High-level gentamicin resistance was seen in 2 of 1125 isolates collected in the BSAC Bacteraemia Surveillance Programme between 2001 and 2014. These organisms, both isolated in 2014, were characterized. Methods: Identifications were by latex agglutination, MICs by BSAC agar dilution and sequencing by Illumina methodology. Results: Gentamicin MICs were >1024 mg/L versus a species mode of 8 mg/L; both isolates also were unusually ciprofloxacin resistant with MICs of 64 mg/L versus a species mode of 1 mg/L. They were distinct by sequence, but both belonged to the ST19 clone, which occurs globally. Both had aac(6′)-aph(2″), carried by different transposons, explaining their gentamicin resistance, and had gyrA[81:S-L];parC[79:S-Y], accounting for ciprofloxacin resistance. Conclusions: These are the first multiresistant S. agalactiae with the bifunctional AAC(6′)-APH(2″) enzyme to be reported in the UK for >10 years. Despite belonging to the same clonal complex, the two isolates and their resistance transposons were distinct. Both retained full susceptibility to penicillin, but any penicillin/gentamicin synergy is likely to be lost.
Original languageEnglish
Pages (from-to)2704–2707
Number of pages4
JournalJournal of Antimicrobial Chemotherapy
Issue number10
Early online date6 Jul 2017
Publication statusPublished - 1 Oct 2017

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