Importance of antimicrobial susceptibility testing of Streptococcus pneumoniae

Area of Science:

• Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Streptococcus pneumoniae is a leading cause of bacterial infections.
• Penicillin G has historically been a primary treatment for pneumococcal infections.
• Monitoring antimicrobial resistance is crucial for effective treatment strategies.

Purpose of the Study:

• To investigate the susceptibility of Streptococcus pneumoniae strains to penicillin G.
• To compare the efficacy of different antimicrobial susceptibility testing methods.

Main Methods:

• Isolation and identification of Streptococcus pneumoniae strains.
• Antimicrobial susceptibility testing using broth dilution and disk diffusion methods.
• Evaluation of penicillin G resistance in isolated strains.

Main Results:

• Six out of 36 Streptococcus pneumoniae strains exhibited relative resistance to penicillin G.
• Penicillin G resistance was only detectable using the broth dilution method.
• All resistant strains were misidentified as susceptible by the disk diffusion method (zone size > 29 mm).

Conclusions:

• The disk diffusion method may underestimate penicillin G resistance in Streptococcus pneumoniae.
• Broth dilution is a more reliable method for detecting low-level penicillin G resistance.
• These findings underscore the importance of using appropriate diagnostic methods to guide antibiotic therapy.