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[Comparison of in vitro activity of first, second and third generation cephem antibiotics against various pathogens
Abstract:
In vitro susceptibilities of 3,286 strains of various pathogens isolated from clinical materials in 1983 to various cephem antibiotics were studied using the Showa disk diffusion test. The following antibiotics were evaluated: cephalexin (CEX), cephalothin (CET), cefazolin (CEZ), cefotiam (CTM), cefoxitin (CFX), cefmetazole (CMZ), cefotaxime (CTX), cefoperazone (CPZ), ceftizoxime (CZX), cefmenoxime (CMX) and latamoxef (LMOX). S. aureus: Susceptible strains to CET, CEZ, CTM, CFX and CMZ with MIC less than 15 micrograms/ml accounted for 93, 75, 93, 70 and 96% of the strains tested, while those to CTX, CPZ, CZX, CMX and LMOX for 89, 65, 61, 86 and 62%, respectively. Susceptible strains to CEX at MICs less than or equal to 20 micrograms/ml were 60%. Prevalence of bacterial resistance to CEX and CEZ, which have been used extensively, was greater than that to CET, CTM or CMZ, showing a bimodal distribution of MICs. The third generation cephems studied, in general, also showed bimodal distributions of MICs. S. pyogenes: All strains studied were susceptible to CET, CTX, CPZ, CZX, CMX and LMOX at MICs less than or equal to 15 micrograms/ml. However, susceptible strains to CEZ, CTM, CFX and CMZ accounted for 95, 95, 80 and 90%, respectively, while those to CEX at MICs less than or equal to 20 micrograms/ml for 79%. S. pneumoniae: At MICs less than 3 micrograms/ml, all strains were susceptible to all cephem antibiotics tested. S. faecalis: Only a very few strains were susceptible to these antibiotics. E. coli, K. pneumoniae and Proteus spp.: Susceptible strains of E. coli and K. pneumoniae to CEX at MICs less than or equal to 20 micrograms/ml accounted for 80 and 81% of the strains tested, while those of indole negative and positive Proteus for 69 and 4%, respectively. Strains of E. coli susceptible to CET, CEZ, CTM, CFX and CMZ at MICs less than or equal to 15 micrograms/ml were 78 to 96%, while those to CTX, CPZ, CZX, CMX and LMOX were 94 to 100%. Those of K. pneumoniae to these 2 groups of antibiotics were 81 to 95% and 94 to 100%, respectively. Susceptible strains of indole negative Proteus to the former group were 81 to 93% and those to the latter were 100%.(ABSTRACT TRUNCATED AT 400 WORDS)
Insights
This study evaluated 11 cephem antibiotics against 3,286 clinical bacterial isolates in 1983. Newer cephems showed better activity, with resistance varying by antibiotic and pathogen, highlighting the need for ongoing susceptibility monitoring.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Antibiotic resistance is a growing concern in clinical settings.
- Cephem antibiotics are widely used to treat bacterial infections.
- Understanding in vitro susceptibilities is crucial for effective treatment selection.
Purpose of the Study:
- To assess the in vitro activity of eleven cephem antibiotics against a diverse collection of clinical bacterial pathogens.
- To compare the susceptibility patterns of various bacterial species to different generations of cephem antibiotics.
Main Methods:
- Disk diffusion test (Showa method) was employed.
- 3,286 bacterial strains isolated from clinical materials in 1983 were tested.
- Minimum Inhibitory Concentrations (MICs) were determined for cephalexin, cephalothin, cefazolin, cefotiam, cefoxitin, cefmetazole, cefotaxime, cefoperazone, ceftizoxime, cefmenoxime, and latamoxef.
Main Results:
- Staphylococcus aureus showed high susceptibility to cefmetazole (96%) and cephalothin (93%), but lower susceptibility to cefoperazone (65%).
- Third-generation cephems (cefotaxime, cefoperazone, ceftizoxime, cefmenoxime, latamoxef) demonstrated broad activity against Gram-negative bacteria like E. coli and K. pneumoniae.
- Bacterial resistance patterns, particularly to older cephems like cephalexin and cefazolin, exhibited bimodal distributions, indicating emerging resistance.
Conclusions:
- Newer cephem antibiotics, especially third-generation agents, generally exhibited superior in vitro activity against a wide range of pathogens compared to older ones.
- Significant variations in susceptibility were observed among different bacterial species and even within species, underscoring the importance of pathogen-specific antibiotic selection.
- The study highlighted the prevalence of resistance to commonly used cephems and the potential for bimodal resistance distributions, necessitating continuous surveillance of antibiotic susceptibility.