Prevalence of macrolide-lincosamide resistance and multidrug resistance phenotypes in streptococcal isolates causing infections in European hospitals: Evaluation of the in vitro activity of oritavancin and comparator agents

The aim of this study was to evaluate the prevalence of resistance to erythromycin alone (M) and to erythromycin and clindamycin (cMLSB) as well as multidrug resistance (MDR) phenotypes (resistance to at least three classes of drugs) among clinical enterococci from European countries and adjacent geographic regions. The in vitro activity of oritavancin against these isolates was also evaluated. A total of 2569 streptococci collected from 12 European countries as well as Russia, Turkey and Israel were included. A total of 9.8%, 8.1% and 6.4% of β-haemolytic streptococci (BHS) displayed M, cMLSB and MDR phenotypes, respectively. Oritavancin (99.4-100.0% susceptible) demonstrated modal minimum inhibitory concentration (MIC) (0.03 mg/L) and MIC50 (0.03 mg/L) values that were the same for all BHS or subsets, including MDR. The oritavancin MIC50 value of 0.06 mg/L against Streptococcus dysgalactiae was similar to those of daptomycin and penicillin (MIC50 ≤ 0.06 mg/L for both). Among viridans group streptococci (VGS), 28.3%, 12.7% and 11.6% showed M, cMLSB and MDR phenotypes, respectively. Oritavancin (99.9-100.0% susceptible; MIC50/90, ≤0.008/0.06 mg/L) exhibited potent in vitro activity against VGS and resistant subsets, as did vancomycin (MIC50/90, 0.5/0.5-1 mg/L), daptomycin (MIC50/90, 0.25-0.5/0.5-1 mg/L) and linezolid (MIC50/90, 0.5-1/1 mg/L). In conclusion, rates of resistance phenotypes were higher in VGS than BHS. Oritavancin demonstrated in vitro potencies that were similar to or greater than those of comparators against this recent collection of streptococci, including drug-resistant subsets, from European and adjacent countries.