Coagulase-negative staphylococci (CoNS) are a significant cause of bacteraemia, the treatment of which is becoming increasingly complex due to the emergence of multidrug-resistant strains. This study aimed to evaluate the in vitro activity of ceftobiprole, an advanced-generation cephalosporin, as compared with other antimicrobial agents against CoNS from patients with bacteraemia. As part of the British Society for Antimicrobial Chemotherapy (BSAC) Bacteraemia Surveillance Programme, 650 blood isolates of CoNS were obtained from patients with bacteraemia at 74 centres throughout the UK and Ireland for the years 2013-2015. Minimum inhibitory concentrations (MICs) of ceftobiprole and other antimicrobial agents were determined using the BSAC agar dilution method. Susceptibility was assessed by European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. The majority of the isolates (63.2%) were Staphylococcus epidermidis. Overall, methicillin resistance, as determined by oxacillin susceptibility testing, was observed in 64.2% of isolates. The MIC50/90 of ceftobiprole was 1/2 mg/L, and 100% of CoNS isolates were inhibited at the EUCAST ceftobiprole non-species-specific pharmacokinetic/pharmacodynamic breakpoint of 4 mg/L. Only one isolate was resistant to vancomycin. Overall rates of resistance to ciprofloxacin, clindamycin, erythromycin and teicoplanin were 50.5, 25.1, 68.2 and 20.9%, respectively. In S. epidermidis, resistance to oxacillin was associated with increased resistance to other antimicrobials. Ceftobiprole demonstrated in vitro activity against all CoNS species isolated from patients with bacteraemia and was active against species resistant to other antistaphylococcal antimicrobials. The collection of clinical data regarding the efficacy of ceftobiprole in treating CoNS bacteraemia is warranted.
Keywords: Antimicrobial resistance; Bacteraemia Surveillance Programme; British Society for Antimicrobial Chemotherapy; Ceftobiprole; Coagulase-negative staphylococci; Susceptibility testing.