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Streptococcus anginosus (milleri) Group Strains Isolated in Poland (1996-2012) and their Antibiotic Resistance

Katarzyna Obszańska, Izabella Kern-Zdanowicz, Aleksandra Kozińska

    Polish Journal of Microbiology
    |June 11, 2016
    PubMed

    Insights

    The Streptococcus Anginosus Group (SAG) causes purulent infections but is often misidentified. This study analyzed SAG strains in Poland, finding them diverse and mostly sensitive to penicillin but resistant to tetracycline and macrolides.

    Area of Science:

    • Microbiology
    • Infectious Diseases
    • Epidemiology

    Background:

    • The Streptococcus Anginosus Group (SAG), previously known as the
    • milleri
    • group, comprises Streptococcus anginosus, Streptococcus intermedius, and Streptococcus constellatus.
    • These bacteria are increasingly recognized as pathogens causing purulent infections, though their prevalence is likely underestimated due to misclassification as
    • viridans streptococci
    • in clinical laboratories.

    Purpose of the Study:

    • To investigate the epidemiological situation and antibiotic resistance patterns of SAG infections in Poland.
    • To re-identify and characterize SAG strains isolated between 1996 and 2012.
    • To assess the genetic diversity of SAG strains in Poland.

    Main Methods:

    • Retrospective analysis of SAG strains isolated in Poland from 1996–2012.
    • Strain identification using automated Vitek2 system and MALDI-TOF MS.
    • Antibiotic susceptibility testing via Vitek2, disk diffusion, and E-Tests; PCR for resistance determinants.
    • Genomic typing using Pulse Field Gel Electrophoresis (PFGE) and Multiple Locus Variable Number Tandem Repeats (MLVF) analysis.

    Main Results:

    • SAG strains were rarely isolated in Poland, primarily from purulent infections.
    • Automated methods showed limitations in distinguishing between SAG species and in MIC evaluation.
    • Genomic analysis revealed significant diversity among the analyzed SAG strains.
    • All isolates were sensitive to penicillin; however, a substantial proportion exhibited resistance to macrolides and the majority were resistant to tetracycline.

    Conclusions:

    • SAG infections in Poland are underreported, and current automated diagnostic methods require improvement for accurate species identification and susceptibility testing.
    • The genetic diversity of SAG strains suggests multiple origins or adaptation mechanisms.
    • Antibiotic resistance patterns highlight the need for careful treatment selection, particularly concerning macrolides and tetracyclines.

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