Penicillin-resistant and penicillin-tolerant mutants of group A Streptococci

Penicillin-resistant and penicillin-tolerant mutants of group A Streptococci.

Penicillin-resistant and penicillin-tolerant mutants have been isolated from group A streptococci mutagenized by ethyl methane sulfonate. The resistant mutants had an elevated minimal growth inhibitory concentration for benzylpenicillin (minimal inhibitory concentration, 0.2 microgram/ml, as compared with the minimal inhibitory concentration of 0.006 microgram/ml in the penicillin-susceptible p...

Penicillin-resistant streptococci from the saliva.

Penicillin-resistant viridans streptococci have obtained altered penicillin-binding protein genes from penicillin-resistant strains of Streptococcus pneumoniae.

Penicillin-resistant strains of Streptococcus pneumoniae possess altered forms of penicillin-binding proteins (PBPs) with decreased affinity for penicillin. The PBP2B genes of these strains have a mosaic structure, consisting of regions that are very similar to those in penicillin-sensitive strains, alternating with regions that are highly diverged. Penicillin-resistant strains of viridans grou...

In vitro activities of 22 beta-lactam antibiotics against penicillin-resistant and penicillin-susceptible viridans group streptococci isolated from blood.

A total of 410 strains of viridans group streptococci isolated consecutively from blood were tested by the microdilution method for in vitro susceptibility to 22 beta-lactam antibiotics. One hundred thirty-eight strains (33.6%) were resistant to penicillin with a MIC range of 0.25 to 8 micrograms/ml. MICs of all beta-lactam agents tested were higher for penicillin-resistant strains than for sus...

Effect of penicillin G every three weeks on oral microflora by penicillin resistant Viridans Streptococci.

BACKGROUND Benzathine penicillin G every 3 weeks is the standard protocol for secondary prophylaxis for recurrent rheumatic fever. OBJECTIVE Assess the effect of Benzathine penicillin G on Streptococcus sanguinis and Streptococcus oralis in patients with cardiac valvular disease due to rheumatic fever receiving secondary prophylaxis. METHODS Oral streptococci were evaluated before (baseline...