Group A Streptococcus Colonies from a Single Throat Swab Can Have Heterogeneous Antimicrobial Susceptibility Patterns.
ABSTRACT This study describes for the first time heterogeneity of antibiotic resistance profiles among group A Streptococcus (GAS) isolates originating from a single throat swab in patients with acute pharyngitis. For each throat swab, ten GAS colonies were randomly selected from the primary plate and subcultured to a secondary plate. These isolates were characterized by various phenotypic and genotypic methods. Our results demonstrated that differing antibiotic resistance profiles were present in 19% of pediatric patients with acute pharyngitis before antimicrobial treatment. This heterogeneity likely resulted from horizontal gene transfer amongst streptococcal isolates sharing the same genetic background. As only a minority of colonies displayed antibiotic resistance among these heterogeneous samples, a classical diagnostic antibiogram would have classified them in most instances as 'susceptible' although therapeutic failure could be caused by the proliferation of resistant strains after initiation of antibiotic treatment.
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ABSTRACT: Serious disease caused by Streptococcus pyogenes (group A streptococcus, GAS), particularly rheumatic heart disease and invasive GAS infection, is responsible for more than half a million deaths worldwide per year. With no effective control strategies available for these diseases, a GAS vaccine is urgently needed. The development of a global GAS vaccine has been hindered by the large diversity of circulating strains (emm-types) of GAS in low-incomes settings. Pioneering work in the 1950s showed that the presence of type specific antibodies are responsible for immunity against the homologous emm-type but does not confer protection against heterologous emm-type. Multivalent type specific vaccines would then offer high coverage in the USA and in Europe where only a few strains are predominant while the coverage in low-income settings would be low due to the high diversity of circulating strains. Recent in vitro and in silico discoveries offer an exciting new approach to developing vaccines that protect against the broad range of strains in different regions of the world. These data suggest that antibodies against some emm-types may cross-protect against other emm-types. Cross protection between emm-types would represent a new paradigm in our understanding of immunity against GAS and an avenue for future GAS vaccine formulations.
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ABSTRACT: Preventing the dissemination of antimicrobial resistance depends on appropriate antibiotic stewardship and accurate antimicrobial susceptibility testing (AST). We report the international dissemination of Escherichia coli strains, showing discrepancies between reference methods when phenotypically tested for susceptibility to piperacillin/tazobactam (TZP). We demonstrate that these related strains are predisposed to problematic TZP AST interpretations.European Journal of Clinical Microbiology 02/2013; 32(8). DOI:10.1007/s10096-013-1837-5 · 3.02 Impact Factor
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ABSTRACT: Eleven out of 40 children with adenoiditis were colonized with multiple genotypes of H. influenzae. Heterogeneous antibiotic susceptibility to ampicilin and co-trimoxazole was observed in six children. A multiple-colony methodology may potentially help to find the resistant strains of H. influenzae in patients who do not respond to the antibiotic treatment.Diagnostic microbiology and infectious disease 07/2014; DOI:10.1016/j.diagmicrobio.2014.03.013 · 2.45 Impact Factor