Pneumococcal beta hemolysin produced under the effect of antibiotics.

The relationship between exposure of pneumococci to antibiotics and appearance of beta hemolysis (rather than the usual alpha hemolysis) was studied in 100 isolates. All strains were capable of producing beta hemolysis. This occurred at the edge of inhibition zones produced by methicillin and other antibiotics, but only if grown anaerobically and subsequently exposed to air at reduced temperatures. Autolysis of the pneumococci was necessary for the beta hemolysis to be produced. Beta hemolysis was optimal at pH 6.8; none occurred at pH 7.4. The concentration of red cells influenced the reaction: at 4% the extent of beta hemolysis was drastically reduced, which suggests that the lysin is not an enzyme.