The British Society for Antimicrobial Chemotherapy Resistance Surveillance Project: methods and limitations

Objectives The BSAC Bacteraemia and Respiratory Resistance Surveillance Programmes provided long-term surveillance of antibiotic resistance in key pathogens of bloodstream and both community- and hospital-acquired respiratory infections in the UK and Ireland. This paper details the methodologies used. Data limitations are discussed. Methods Sentinel laboratories across the UK and Ireland contributed up to a fixed annual quota of isolates of defined bacterial groups. For each Programme, a Central Laboratory confirmed bacterial identifications, measured MICs by the BSAC agar dilution method, investigated mechanisms of resistance and determined serotypes of Streptococcus pneumoniae. Identification methods evolved over time, e.g. with adoption of MALDI-TOF. Classification of susceptibility and resistance follows the 2022 (not contemporaneous) EUCAST guidance. Results Seventy-nine laboratories contributed 30 716 community respiratory isolates from 1999/2000 to 2018/19; 65 laboratories contributed 13 508 hospital respiratory isolates from 2008/09 to 2018/19; 81 laboratories contributed 56 064 bacteraemia isolates from 2001 to 2019. Although large and teaching hospitals were over-represented, the resistance rates for bacteraemia organisms collected in England mirror more extensive (but less standardized or detailed) national data gathered from laboratories by the UK Health Security Agency and its predecessor organizations, which provided a bespoke data extract. Conclusions These surveillance Programmes have provided comprehensive and reliable information on antibiotic susceptibility in the UK and Ireland over two decades. Detailed results, showing resistance trends and mechanisms of antibiotic resistance, are presented in five papers in this Supplement.