Evaluation of methods for detection of ß-lactamase production in MSSA.
J Antimicrob Chemother
; 76(6): 1487-1494, 2021 05 12.
Article
in En
| MEDLINE
| ID: mdl-33615356
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 ß-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 ß-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 ß-lactamase-negative isolate.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Staphylococcus aureus
/
Beta-Lactamases
Type of study:
Diagnostic_studies
Language:
En
Journal:
J Antimicrob Chemother
Year:
2021
Document type:
Article
Affiliation country:
Denmark