BACKGROUND: In order to determine the clinical usefulness of the MicroScan (Siemens Healthcare Diagnostics, USA) MICroSTREP plus antimicrobial panel (MICroSTREP) for testing antimicrobial susceptibility of beta-hemolytic streptococci (BHS) and viridans group streptococci (VGS), we compared the accuracy of MICroSTREP with that of the CLSI reference method. METHODS: Seventy-five BHS and 59 VGS isolates were tested for antimicrobial susceptibility to ampicillin, penicillin, cefotaxime, meropenem, erythromycin, clindamycin, levofloxacin, and vancomycin by using MICroSTREP and the CLSI agar dilution method. RESULTS: The overall essential agreement with regard to minimum inhibitory concentrations (MICs) (within +/-1 double dilution) between MICroSTREP and the CLSI reference method was 98.2%, and categorical agreement (CA) was 96.9%. For the BHS isolates, the CA for erythromycin was 96.0%, whereas that for cefotaxime, meropenem, levofloxacin, and vancomycin (for ampicillin, penicillin, and clindamycin; 98.7%) was 100%. For the VGS isolates, the CA for penicillin was 84.7% and that for erythromycin, clindamycin, and vancomycin (for meropenem, 86.5%; for ampicillin, 88.1%; and for cefotaxime and levofloxacin, 96.6%) was 100%. All categorical errors of penicillin and ampicillin in the VGS isolates were minor. CONCLUSIONS: The accuracy of MICroSTREP is comparable to that of the CLSI reference method, suggesting that this panel can be effective for testing antimicrobial susceptibility of BHS and VGS.
Anti-Bacterial Agents/*pharmacology ; Drug Resistance, Bacterial ; Humans ; Microbial Sensitivity Tests ; Reagent Kits, Diagnostic ; Streptococcal Infections/microbiology ; Streptococcus/*drug effects/isolation & purification ; Viridans Streptococci/*drug effects/isolation & purification

BACKGROUND: Viridans group streptococci (VGS) are both commensal microbes and potential pathogens. Increasing resistance to penicillin in VGS is an ongoing issue in the clinical environment. We investigated the difference in susceptibility and resistance to penicillin among various VGS species. METHODS: In total 1,448 VGS isolated from various clinical specimens were analyzed over a two-yr period. Identification and antimicrobial susceptibility test was performed by the automated VITEK 2 system (bioMerieux, France) or the MicroScan MICroSTREP system (Siemens, Germany). RESULTS: Among the 1,448 isolates, 412 were isolated from blood (28.4%). Streptococcus mitis group was the most frequently isolated (589 isolates, 40.7%), followed by the S. anginosus group (290 isolates, 20.0%), S. sanguinis group (179 isolates, 12.4%) and S. salivarius group (57 isolates, 3.9%). In total, 314 isolates could not be identified up to the species level. The overall non-susceptibility to penicillin was observed to be 40.0% (resistant, 11.2% and intermediately resistant, 28.8%) with uneven distribution among groups; 40.2% in S. sanguinis group (resistant, 5.0% and intermediately resistant, 35.2%), 60.3% in S. mitis group (resistant, 20.9% and intermediately resistant, 39.4%), 78.9% in S. salivarius group (resistant, 8.8% and intermediately resistant, 70.1%), and 6.2% in S. anginosus group (resistant, 1.7% and intermediately resistant, 4.5%). CONCLUSIONS: Antimicrobial resistance patterns towards penicillin show differences among various VGS; this should be considered while devising an effective antimicrobial treatment against VGS.
Anti-Infective Agents/*pharmacology ; Body Fluids/microbiology ; Drug Resistance, Bacterial ; Humans ; Microbial Sensitivity Tests ; Penicillins/pharmacology ; Streptococcal Infections/microbiology/pathology ; Viridans Streptococci/*drug effects/isolation & purification