Objectives: To determine antibiotic susceptibility in isolates of Streptococcus pneumoniae and Haemophilus influenzae collected in 2014-16 from Russia.
Methods: MICs were determined by CLSI broth microdilution and susceptibility was assessed using CLSI, EUCAST and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints.
Results: A total of 279 S. pneumoniae and 279 H. influenzae were collected. Overall, 67.0% of S. pneumoniae were penicillin susceptible by CLSI oral/EUCAST and 93.2% by CLSI intravenous (iv) breakpoints. All were fluoroquinolone susceptible, with amoxicillin, amoxicillin/clavulanic acid and ceftriaxone susceptibility ≥92.8% by CLSI and PK/PD breakpoints. Isolates showed lower susceptibility to cefuroxime, cefaclor, macrolides and trimethoprim/sulfamethoxazole by CLSI criteria: 85.0%, 76.7%, 68.8% and 67.7%, respectively. Generally, susceptibility was slightly lower by EUCAST criteria, except for cefaclor, for which the difference in susceptibility was much greater. Penicillin-resistant isolates had low susceptibility (≤60%) to all agents except fluoroquinolones. All 279 H. influenzae were ceftriaxone susceptible, 15.4% were β-lactamase positive and ≥97.5% were amoxicillin/clavulanic acid susceptible (CLSI, EUCAST and PK/PD breakpoints). Four isolates were fluoroquinolone non-susceptible by current EUCAST criteria. A major discrepancy was found with azithromycin susceptibility between CLSI (99.3%) and EUCAST and PK/PD (2.2%) breakpoints. Trimethoprim/sulfamethoxazole was poorly active (62.7% susceptible).
Conclusions: Susceptibility to penicillin (oral), macrolides and trimethoprim/sulfamethoxazole was low in S. pneumoniae from Russia. However, isolates were fully susceptible to fluoroquinolones and ≥92.8% were susceptible to amoxicillin, amoxicillin/clavulanic acid and ceftriaxone. Isolates of H. influenzae only showed reduced susceptibility to ampicillin, cefaclor, clarithromycin and trimethoprim/sulfamethoxazole. Some differences were detected between CLSI, EUCAST and PK/PD breakpoints, especially with cefaclor, cefuroxime and macrolides. These data suggest further efforts are required to harmonize international breakpoints.