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Mobile elements and chromosomal changes associated with MLS resistance phenotypes of invasive pneumococci recovered in the United States.

ABSTRACT: Pneumococcal macrolide resistance is usually expressed as one of two phenotypes: the M phenotype conferred by the mef gene or the MLSB phenotype caused by modification of ribosomal targets, most commonly mediated by an erm methylase. Target-site modification leading to antibiotic resistance can also occur due to sequence mutations within the 23S rRNA or the L4 and L22 riboproteins. We screened 4,535 invasive isolates resistant to erythromycin and 18 invasive isolates nonsusceptible to quinupristin-dalfopristin (Q-D) to deduce the potential mechanisms involved. Of 4,535 erythromycin-resistant isolates, 66.2% were polymerase chain reaction (PCR)-positive for mef alone, 17.8% for ermB alone, and 15.1% for both mef and ermB. Thirty-seven isolates (0.9%) were PCR negative for both determinants. Of these, 3 were positive for ermA (subclass ermTR) and 25 had chromosomal mutations. No chromosomal mutations (in 23S rRNA, rplD, or rplV) nor any of the macrolides/lincosamides/streptogramin (MLS) resistance genes screened for (ermT, ermA, cfr, lsaC, and vgaA) were found in the remaining nine isolates. Of 18 Q-D nonsusceptible isolates, 14 had chromosomal mutations and one carried both mef and ermB; no chromosomal mutations or other resistance genes were found in 3 isolates. Overall, we found 28 mutations, 13 of which have not been previously described in Streptococcus pneumoniae. The role of these mutations remains to be confirmed by transformation assays.

SUBMITTER: Hawkins PA

PROVIDER: S-EPMC5735413 | biostudies-literature | 2015 Apr

REPOSITORIES: biostudies-literature

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Mobile elements and chromosomal changes associated with MLS resistance phenotypes of invasive pneumococci recovered in the United States.

Hawkins Paulina A PA Chochua Sopio S Jackson Delois D Beall Bernard B McGee Lesley L

Microbial drug resistance (Larchmont, N.Y.) 20140812 2

Pneumococcal macrolide resistance is usually expressed as one of two phenotypes: the M phenotype conferred by the mef gene or the MLSB phenotype caused by modification of ribosomal targets, most commonly mediated by an erm methylase. Target-site modification leading to antibiotic resistance can also occur due to sequence mutations within the 23S rRNA or the L4 and L22 riboproteins. We screened 4,535 invasive isolates resistant to erythromycin and 18 invasive isolates nonsusceptible to quinuprist ...[more]

PMID: 25115711

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Project description:Group A streptococci (GAS) are genetically diverse. Determination of strain features can reveal associations with disease and resistance and assist in vaccine formulation. We employed whole-genome sequence (WGS)-based characterization of 1,454 invasive GAS isolates recovered in 2015 by Active Bacterial Core Surveillance and performed conventional antimicrobial susceptibility testing. Predictions were made for genotype, GAS carbohydrate, antimicrobial resistance, surface proteins (M family, fibronectin binding, T, R28), secreted virulence proteins (Sda1, Sic, exotoxins), hyaluronate capsule, and an upregulated nga operon (encodes NADase and streptolysin O) promoter (Pnga3). Sixty-four M protein gene (emm) types were identified among 69 clonal complexes (CCs), including one CC of Streptococcus dysgalactiae subsp. equisimilisemm types predicted the presence or absence of active sof determinants and were segregated into sof-positive or sof-negative genetic complexes. Only one "emm type switch" between strains was apparent. sof-negative strains showed a propensity to cause infections in the first quarter of the year, while sof+ strain infections were more likely in summer. Of 1,454 isolates, 808 (55.6%) were Pnga3 positive and 637 (78.9%) were accounted for by types emm1, emm89, and emm12 Theoretical coverage of a 30-valent M vaccine combined with an M-related protein (Mrp) vaccine encompassed 98% of the isolates. WGS data predicted that 15.3, 13.8, 12.7, and 0.6% of the isolates were nonsusceptible to tetracycline, erythromycin plus clindamycin, erythromycin, and fluoroquinolones, respectively, with only 19 discordant phenotypic results. Close phylogenetic clustering of emm59 isolates was consistent with recent regional emergence. This study revealed strain traits informative for GAS disease incidence tracking, outbreak detection, vaccine strategy, and antimicrobial therapy.IMPORTANCE The current population-based WGS data from GAS strains causing invasive disease in the United States provide insights important for prevention and control strategies. Strain distribution data support recently proposed multivalent M type-specific and conserved M-like protein vaccine formulations that could potentially protect against nearly all invasive U.S. strains. The three most prevalent clonal complexes share key polymorphisms in the nga operon encoding two secreted virulence factors (NADase and streptolysin O) that have been previously associated with high strain virulence and transmissibility. We find that Streptococcus pyogenes is phylogenetically subdivided into loosely defined multilocus sequence type-based clusters consisting of solely sof-negative or sof-positive strains; with sof-negative strains demonstrating differential seasonal preference for infection, consistent with the recently demonstrated differential seasonal preference based on phylogenetic clustering of full-length M proteins. This might relate to the differences in GAS strain compositions found in different geographic settings and could further inform prevention strategies.

Dataset Information

Mobile elements and chromosomal changes associated with MLS resistance phenotypes of invasive pneumococci recovered in the United States.

Publications

Mobile elements and chromosomal changes associated with MLS resistance phenotypes of invasive pneumococci recovered in the United States.

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