Methods for predicting susceptibility of Streptococcus pneumoniae to cefixime

Area of Science:

• Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Streptococcus pneumoniae is a common cause of bacterial infections.
• Antimicrobial resistance in S. pneumoniae is a growing public health concern.
• Cefixime is a third-generation cephalosporin antibiotic used to treat bacterial infections.

Purpose of the Study:

• To evaluate the susceptibility of Streptococcus pneumoniae isolates to cefixime.
• To determine the reliability of different antibiotic susceptibility testing methods for predicting cefixime effectiveness.

Main Methods:

• Disk diffusion method was used to test susceptibility of 698 Streptococcus pneumoniae isolates.
• Isolates were tested against cefixime (5-micrograms disk) and oxacillin (1-microgram disk).
• Susceptibility to cefixime (0.5 microgram/ml) was determined for penicillin-susceptible isolates.

Main Results:

• Out of 698 S. pneumoniae isolates, 475 were penicillin-susceptible.
• >99% of penicillin-susceptible isolates showed susceptibility to 0.5 microgram/ml cefixime.
• A 1-microgram oxacillin disk was found to be more reliable than a 5-micrograms cefixime disk for predicting cefixime susceptibility.

Conclusions:

• Cefixime demonstrates high in vitro activity against penicillin-susceptible Streptococcus pneumoniae.
• Oxacillin disk susceptibility testing serves as a reliable surrogate marker for predicting cefixime susceptibility in S. pneumoniae.
• These findings support the continued use of cefixime for treating susceptible S. pneumoniae infections and highlight an effective susceptibility testing strategy.