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Surrogate disks for predicting cefotaxime and ceftriaxone susceptibilities of Streptococcus pneumoniae
Abstract:
Cefotaxime- and ceftriaxone-resistant Streptococcus pneumoniae is now appearing in some medical centers, but 30-micrograms cefotaxime or 30-micrograms ceftriaxone disks are not reliable for detecting such strains. Studies were undertaken to select another cephalosporin disk that might be used as a screening test that could be used in conjunction with a 1-micrograms oxacillin disk. A 30-micrograms cefuroxime disk is proposed: strains with zones > or = 28 mm in diameter are predictably susceptible to cefotaxime and ceftriaxone, and those with smaller zones should be further studied to confirm resistance to either drug. A 30-micrograms ceftizoxime disk may also be used as a screening test with zones > or = 26 mm indicating susceptibility, but cefuroxime disks are preferred.
Insights
Cefotaxime- and ceftriaxone-resistant Streptococcus pneumoniae strains are emerging. A cefuroxime disk test is proposed as a reliable method for detecting these resistant strains, improving patient care.
Area of Science:
- Clinical microbiology
- Infectious diseases
- Antimicrobial resistance
Background:
- Emergence of cefotaxime- and ceftriaxone-resistant Streptococcus pneumoniae strains in healthcare settings.
- Limitations of current disk diffusion methods (cefotaxime, ceftriaxone) for detecting these resistant strains.
Purpose of the Study:
- To identify a reliable cephalosporin disk for screening cefotaxime- and ceftriaxone-resistant Streptococcus pneumoniae.
- To evaluate the utility of cefuroxime and ceftizoxime disks as adjuncts to oxacillin disk testing.
Main Methods:
- Comparative analysis of cephalosporin disk diffusion tests.
- Evaluation of cefuroxime and ceftizoxime disks against known resistant and susceptible strains.
- Correlation of disk zone diameters with actual resistance to cefotaxime and ceftriaxone.
Main Results:
- A 30-micrograms cefuroxime disk is proposed as a reliable screening tool.
- Zone diameters ≥ 28 mm with cefuroxime disks predict susceptibility to cefotaxime and ceftriaxone.
- Ceftizoxime disks can also be used, with zones ≥ 26 mm indicating susceptibility, but cefuroxime is preferred.
Conclusions:
- Cefuroxime disk diffusion offers a dependable method for screening cefotaxime- and ceftriaxone-resistant Streptococcus pneumoniae.
- This screening test, used with oxacillin disks, can aid in early identification and management of resistant infections.