{"doi":"10.1093/jac/dkab032","title":"Evaluation of methods for detection of β-lactamase production in MSSA","abstract":"OBJECTIVES: Correct determination of penicillin susceptibility is pivotal for using penicillin in the treatment of Staphylococcus aureus infections. This study examines the performance of MIC determination, disc diffusion and a range of confirmatory tests for detection of penicillin susceptibility in S. aureus. METHODS: A total of 286 consecutive penicillin-susceptible S. aureus blood culture isolates as well as a challenge set of 62 MSSA isolates were investigated for the presence of the blaZ gene by PCR and subjected to penicillin-susceptibility testing using broth microdilution MIC determination, disc diffusion including reading of the zone edge, two nitrocefin tests and the cloverleaf test. RESULTS: Using PCR-based detection of blaZ as the gold standard, both broth microdilution MIC testing and disc diffusion testing resulted in a relatively low accuracy (82%-93%) with a sensitivity ranging from 49%-93%. Among the confirmatory tests, the cloverleaf test performed with 100% accuracy, while zone edge interpretation and nitrocefin-based tests increased the sensitivity of β-lactamase detection to 96%-98% and 82%-96% when using MIC determination or disc diffusion as primary test, respectively. CONCLUSIONS: This investigation showed that reliable and accurate detection of β-lactamase production in S. aureus can be obtained by MIC determination or penicillin disc diffusion followed by interpretation of the zone edge as a confirmatory test for apparently penicillin-susceptible isolates. The more cumbersome cloverleaf test can also be used. Nitrocefin-based tests should not be used as the only test for confirmation of a presumptive β-lactamase-negative isolate.","journal":"Journal of Antimicrobial Chemotherapy","year":2021,"id":176131,"datarank":0.961667561655503,"base_score":3.091042453358316,"endowment":3.091042453358316,"self_citation_contribution":0.4636563680037475,"citation_network_contribution":0.4980111936517556,"self_endowment_contribution":0.4636563680037475,"citer_contribution":0.4980111936517556,"corpus_percentile":78.98971145664113,"corpus_rank":2717,"citation_count":21,"citer_count":19,"citers_with_citation_signal":13,"citers_with_endowment":13,"datacite_reuse_total":0,"is_dataset":true,"is_dataset_confidence":0.5481,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2021-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":422020,"name":"David Lonsway","orcid":"0000-0002-7359-7587","position":1,"is_corresponding":false},{"id":335015,"name":"Jesper Larsen","orcid":"0000-0003-0582-0457","position":2,"is_corresponding":false},{"id":335014,"name":"Anders Rhod Larsen","orcid":"0000-0002-1713-8765","position":3,"is_corresponding":false},{"id":718670,"name":"Jurgita Samulioniené","orcid":null,"position":4,"is_corresponding":false},{"id":464692,"name":"Brandi Limbago","orcid":null,"position":5,"is_corresponding":false},{"id":335013,"name":"Robert Skov","orcid":"0000-0002-6079-5381","position":0,"is_corresponding":true}],"reference_count":27,"raw_metadata":null,"created_at":"2026-07-18T23:47:19.591542Z","pmid":"33615356","pmcid":"PMC9479532","fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}