ANTIBIOTICS 175 



The majuiity of organisms wJiicli arc seiisitive to 

 Ijenicillin are Gram -positive, namely, Stajihylococcus, 

 Streptococcus, pneiimococciis, C. dipJitherice, B. anthracis, 

 Actinomyces, CI. loelchii, CI. cedenuitiens and other 

 Clostridia. The sensitive Gram -negative organisms are 

 the gonococcus, meningococcus and Micrococcus catarrh- 

 alls. The other Gram -negative pathogens are not 

 affected by penicillin nor are Gram-negative saproph;>i3es, 

 yeasts or moulds. The tubercle bacillus is not sensitive 

 to penicillin. The activity of penicillin is not affected 

 by the presence of serum, blood or pus nor by the number 

 of organisms present. 



Penicillin is almost completely non-toxic to man or 

 animals and has no deleterious effect on leucocytes or 

 tissue cells. It is, therefore, superior to the sulphonamides 

 in these respects. From the chemotherapeutic point of 

 view it has the defects that it camiot be given l)y mouth 

 as it is destroyed by the acid of the stomach, and that it 

 is very rapidly excreted in the urine after intravenous 

 or intramuscular injection. In order to maintain an 

 adequate concentration in the blood it must be ad- 

 ministered by the continuous intravenous drip method 

 or by intramuscular injections repeated at least every 

 three hours for as long as the infection persists. A daily 

 dosage of about 120,000 Oxford units is necessary. 

 Penicillin is of particular value in treating staphylococcal 

 septicaemia, which is often resistant to treatment with 

 sulphonamides, osteomyelitis, gas gangrene, gonorrhoea 

 and infections by sulphonamide resistant strains of 

 pneumococci. Penicillin can be used effectively in the 

 local treatment of burns, wounds and skin infections 

 by application in a cream or as a powder (usually mixed 

 with sulphanilamide). The methyl and ethyl esters of 

 penicillin are more stable than penicillin to such an 

 extent that they can be given by mouth. They have 

 only about one hundredth of the activity of penicillin 



