The Activity of Penicillin in Relation to Bacterial Spores and the Preservation of Milk

Abstract

Tubes of sterile (autoclaved) milk were inoculated with washed spores, heated at 98[degree]C for 15 min., cooled, treated with penicillin and stored with or without seals at 30 [degree]C. 49 cultures, comprising 17 aerobic and 2 anaerobic spp., were studied. Bacillus cereus, B. mycoides, B. metiens and B. albolactis were relatively resistant to penicillin. In their presence penicillin was not an effective preserving agent except in prohibitive concs. The remaining 13 spp. were relatively susceptible to penicillin as manifested by strong sporicidal or prolonged sporistatic activity in drug concs, of 5 U./ml.; the latter conc, greatly delayed but did not prevent spoilage and the formation of toxin by Clostridium botulinum. Penicillin (5-500 U./ml.) was usually ineffective in preventing the spoilage of uninoculated raw milk. Evidence suggests that all spore populations contain penicillin-susceptible spores, species differing in the relative proportion of resistant and non-resistant cells. It is concluded that penicillin has no application in the preservation of food.