Related Experiment Video
Updated: Jul 28, 2026
14:04
Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
24.7K
Antimicrobial Susceptibility Testing for Staphylococcus lugdunensis
Joanne S K Teh1,2, Ioanna Pantelis1,2, Xiao Chen1,2
1Flinders Medical Centregrid.414925.f, Department of Microbiology and Infectious Diseases, Adelaide, South Australia, Australia.
Journal of Clinical Microbiology
|October 27, 2021
Summary
Disc diffusion testing showed higher accuracy for penicillin and oxacillin susceptibility in Staphylococcus lugdunensis compared to automated methods. This study highlights disc diffusion as a more reliable method for guiding antibiotic treatment decisions.
Area of Science:
- Microbiology
- Clinical Diagnostics
- Antimicrobial Resistance
Background:
- Accurate antibiotic susceptibility testing is crucial for effective treatment of Staphylococcus lugdunensis infections.
- Discrepancies exist between phenotypic testing methods and genotypic resistance mechanisms.
- Evaluating diagnostic methods for common antibiotics like penicillin and oxacillin is essential.
Purpose of the Study:
- To compare the accuracy of disc diffusion and automated broth microdilution for penicillin and oxacillin susceptibility testing in Staphylococcus lugdunensis.
- To evaluate the performance of EUCAST and CLSI penicillin susceptibility testing guidelines.
- To assess the utility of cefoxitin disc diffusion for predicting oxacillin resistance.
Main Methods:
- Susceptibility testing of 200 Staphylococcus lugdunensis isolates using penicillin disc diffusion (1 IU and 10 IU), nitrocefin discs, cefoxitin discs, and automated broth microdilution (Vitek 2).
- Reference methods included blaZ and mecA PCR.
- Comparison of results from different phenotypic methods against genotypic reference standards.
Main Results:
- Disc diffusion showed high correlation with blaZ PCR for penicillin susceptibility, with few major or very major errors.
- Vitek 2 automated broth microdilution overestimated penicillin resistance in blaZ-negative isolates.
- Cefoxitin disc diffusion and Vitek 2 showed categorical agreement for oxacillin resistance in mecA-positive isolates, but Vitek 2 misidentified mecA-negative isolates as resistant.
Conclusions:
- Automated broth microdilution (Vitek 2) overestimated penicillin and oxacillin resistance in Staphylococcus lugdunensis compared to disc diffusion and PCR.
- Disc diffusion with zone edge interpretation demonstrated superior accuracy and specificity for S. lugdunensis susceptibility testing.
- Disc diffusion is a more reliable method for guiding antimicrobial therapy for S. lugdunensis infections.
Related Concept Videos
01:25Mechanism of Antibiotic Resistance in MRSA
Antibiotic resistance in bacteria arises when microorganisms evolve the ability to withstand drugs designed to kill them or inhibit their growth, rendering once-effective treatments useless. This phenomenon, driven by genetic change and selection under antibiotic exposure, poses a profound threat to modern medicine. Mechanisms include drug-inactivating enzymes (e.g., β-lactamases), efflux pumps that eject antibiotics, mutations altering antibiotic targets, decreased drug uptake, and acquisition...
01:25Clinical Significance of Antibiotic Resistance
Methicillin-resistant Staphylococcus aureus (MRSA) presents a critical public health threat, arising from its capacity to resist β-lactam antibiotics due to acquisition of the mecA gene within the staphylococcal cassette chromosome mec (SCCmec). This gene encodes penicillin-binding protein 2a (PBP2a), which impairs binding efficacy of methicillin and other β-lactams. MRSA has evolved into distinct clonal lineages impacting humans and animals alike, reinforcing its significance within the One...