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Differences between ceftriaxone and cefotaxime: microbiological inconsistencies
John G Gums1, D Wesston Boatwright, Mark Camblin
1Department of Pharmacy Practice, University of Florida, Gainesville, FL 32601, USA. jgums@ufl.edu
Objective:
To review data to determine why pneumococcal isolates appear to be increasingly resistant to cefotaxime, historically regarded as having the same in vitro susceptibility to ceftriaxone, and what this observation might imply clinically.
Data Sources:
Literature was accessed through MEDLINE (1966-October 2007) using the MeSH terms cefotaxime, ceftriaxone, susceptibility, microbial sensitivity tests, antibiotics, pneumococcal infections, Streptococcus pneumoniae, resistance, and cephalosporin resistance. Abstracts and surveillance databases were reviewed and unpublished data were provided by state departments of health and institutions.
Study Selection And Data Extraction:
All articles published in the English language that were identified from the data sources were evaluated.
Data Synthesis:
An experimental model of pneumococcal infection in mice conducted 2 decades ago predicted that the delta T minimum inhibitory concentration (MIC) varied less for ceftriaxone than for cefotaxime. Studies of plasma and serum concentrations show that ceftriaxone remains at a concentration above the S. pneumoniae MIC for 100% of the dosing interval at 12 hours. Types of MIC susceptibility test methods for ceftriaxone and cefotaxime used against S. pneumoniae respiratory isolates were found to be similar. Data from state and county health departments found microbiological discrepancies between ceftriaxone and cefotaxime. In areas with high rates of penicillin-resistant S. pneumoniae (PRSP), isolates were twice as susceptible to ceftriaxone versus cefotaxime. Surveillance databases consistently show differences between susceptibility of S. pneumoniae to cefotaxime versus ceftriaxone over time. MIC and pulsed-field gel electrophoresis studies suggest that phenotypic discrepancies may account for penicillin resistance. Ongoing studies are examining S. pneumoniae isolates at the molecular level to determine the basis of difference in resistance to cefotaxime and ceftriaxone.
Conclusions:
An increase in rates of PRSP and differences in S. pneumoniae isolate susceptibility between ceftriaxone and cefotaxime emphasize the necessity for hospital laboratories to detect these changes as they occur. Clinicians should select the most appropriate agent for patients with S. pneumoniae.
Insights
Increasing penicillin-resistant Streptococcus pneumoniae (PRSP) isolates show differing susceptibility to cefotaxime and ceftriaxone. Hospital labs must monitor these changes for appropriate antibiotic selection in pneumococcal infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Cefotaxime and ceftriaxone are historically considered to have similar in vitro activity against Streptococcus pneumoniae.
- Emerging resistance patterns necessitate a review of antimicrobial susceptibility data.
Purpose of the Study:
- To investigate the reasons for increasing cefotaxime resistance in pneumococcal isolates.
- To determine the clinical implications of observed differences in susceptibility between cefotaxime and ceftriaxone.
Main Methods:
- Literature review of MEDLINE (1966-2007) using relevant MeSH terms.
- Evaluation of abstracts, surveillance databases, and unpublished data from health departments.
- Analysis of minimum inhibitory concentration (MIC) and pulsed-field gel electrophoresis studies.
Main Results:
- Experimental models predicted less variation in ceftriaxone MIC compared to cefotaxime.
- Ceftriaxone maintains concentrations above the S. pneumoniae MIC for longer dosing intervals.
- Discrepancies in susceptibility were observed, with isolates being more susceptible to ceftriaxone than cefotaxime, particularly in areas with high rates of penicillin-resistant S. pneumoniae (PRSP).
Conclusions:
- Increased PRSP rates correlate with differing pneumococcal susceptibility to ceftriaxone and cefotaxime.
- Hospital laboratories need to detect these evolving resistance trends.
- Clinicians should carefully select antibiotics for S. pneumoniae infections based on current susceptibility data.
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