Penicillin tolerance among oral streptococci.

Area of Science:

• Microbiology
• Bacteriology
• Oral Microbiology

Background:

• Penicillin tolerance is a significant factor in treatment failures for bacterial infections.
• Viridans streptococci are common commensals in the human oral cavity and can cause opportunistic infections.
• Understanding penicillin tolerance in oral streptococci is crucial for effective antimicrobial strategies.

Purpose of the Study:

• To determine the prevalence of penicillin tolerance in viridans streptococci isolated from healthy subjects and blood cultures.
• To identify streptococcal species most frequently exhibiting penicillin tolerance.
• To evaluate the efficacy of penicillin alone and in combination with gentamicin against tolerant oral streptococci.

Main Methods:

• Isolation and identification of viridans streptococci from oral swabs and blood cultures.
• Determination of penicillin tolerance using standard microbiological techniques.
• In vitro susceptibility testing of penicillin and gentamicin against various streptococcal strains.

Main Results:

• Penicillin tolerance was observed in 18/46 oral streptococcal strains and 31/54 blood culture isolates.
• Enterococci and Streptococcus sanguis showed the highest rates of tolerance.
• Oral streptococci, whether tolerant or sensitive, exhibited slower killing by penicillin alone compared to Streptococcus pyogenes, but were effectively killed by penicillin-gentamicin combinations.

Conclusions:

• Penicillin tolerance is a prevalent characteristic among oral streptococci, posing a challenge for antibiotic therapy.
• Specific species like Enterococci and S. sanguis are frequently tolerant.
• Combination therapy with penicillin and gentamicin demonstrates potent bactericidal activity against both tolerant and sensitive oral streptococci.