Unexpected relationships between frequency of antimicrobial resistance, disease phenotype and emm type in group A Streptococcus

Despite universal susceptibility to β-lactams, resistance to second-line antimicrobials (e.g. erythromycin) is increasingly common among group A (GAS). To better understand the frequency of regional GAS antimicrobial resistance, we screened a previously described GAS strain collection from Houston,...

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Bibliographic Details
Published in:Microbial genomics 2019-11, Vol.5 (11)
Main Authors: Sanson, Misu A, Macias, Olga R, Shah, Brittany J, Hanson, Blake, Vega, Luis Alberto, Alamarat, Zain, Flores, Anthony R
Format: Article
Language:English
Subjects:
Anti-Bacterial Agents - pharmacology
Bacterial Outer Membrane Proteins - genetics
Bacterial Outer Membrane Proteins - metabolism
Drug Resistance, Bacterial - genetics
Erythromycin - pharmacology
Genotype
Microbial Sensitivity Tests
Phenotype
Phylogeny
Streptococcal Infections - genetics
Streptococcus pyogenes - genetics
Streptococcus pyogenes - metabolism
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Summary:Despite universal susceptibility to β-lactams, resistance to second-line antimicrobials (e.g. erythromycin) is increasingly common among group A (GAS). To better understand the frequency of regional GAS antimicrobial resistance, we screened a previously described GAS strain collection from Houston, TX, USA, for resistance to commonly used antimicrobials. A total of 100/929 (10.8 %) showed resistance to at least one antimicrobial. Tetracycline resistance was identified in 52 (5.6 %) GAS strains. The cumulative frequency of erythromycin and clindamycin resistance [macrolide (M) and macrolide-lincosamide-streptogramin (MLS) phenotypes] was greatest among invasive GAS strains (9.9 %) compared to that of strains derived from any other infection type (5.9 %, =0.045). We identified types 11, 75, 77 and 92 as the only types with high (e.g. >50 %) within- type resistance and contributing to the majority (24/26; 92 %) of erythromycin/clindamycin resistance in invasive GAS. High-frequency resistance types were also significantly overrepresented in invasive GAS strains as indicated by invasive index. We performed whole-genome sequencing to define genetic elements associated with resistance among types 11, 75, 77 and 92. Diverse mobile elements contributed to GAS resistance including transposons, integrative conjugative elements, prophage and a plasmid. Phylogenetic analysis suggests recent clonal emergence of GAS strains. Our findings indicate that less frequently encountered GAS types disproportionately contribute to resistance phenotypes, are defined by diverse mobile genetic elements and may favour invasive disease.
ISSN:2057-5858
2057-5858
DOI:10.1099/mgen.0.000316