Abstract
Microbiological evaluation of cephapirin was made by comparing with three known antibiotics of the cephalosporin family, cephalothin, cephaloridine and cefazolin, as to in vitro antimicrobial activity including antimicrobial spectrum, sensitivity of clinically isolated strains of bacteria, stability against beta-lactamase and in vivo therapeutical effect in experimentally induced infections in mice.
(1) Cephapirin has virtually the same antimicrobial spectrum as cephalothin, cephaloridine and cefazolin. In the antimicrobial activity, cephaloridine was found superior to the others, cephapirin being virtually equal to cephalothin and cefazolin, when tested with Gram-positive organisms, while the four were comparable to each other when tested with Gram-negative ones.
(2) Clinically isolated staphylococcal strains were sensitive in the range of 0.09-25 mcg/ml to cephapirin, in the range of 0.09-25 mcg/ml to cephalothin, in the range of >0.011-12.5 mcg/ml to cephaloridine and in the range of 0.09-25 mcg/ml to cefazolin.
Clinically isolated E. coli strains, on the other hand, were sensitive in the range of 3.12->100 mcg/ml to cephapirin, cephalothin and cephaloridine, and in the range of 1.56->100 mcg/ml to cefazolin.
In the sensitivity of clinically isolated staphylococcal strains cephapirin was well correlated with cephalothin and cefazolin, while in the case of E. coli strains cephapirin was found to have a good correlation with cephalothin.
(3) Influence of factors on MIC was investigated. Culture pH, human serum and inoculum size were found to effect on MIC of cephapirin.
(4) Cephapirin was found stable as same as cephalothin against beta-lactamase produced by E. coli.
(5) In therapeutical effect on infections in mice caused by Gram-positive organisms such as Staphylococcus aureus Smith, No.13 and Diplococcus pneumoniae type III, cephaloridine was found best, followed by cephapirin, then by cephalothin. The same order of effectiveness resulted when tested on the infections caused by Gram-negative organism E. coli.
