[Bacteriological in vitro investigations with cefaclor. Correlation of inhibition zone diameter and minimal...

A comparison of the minimal inhibitory concentrations (MIC) of cefaclor and cephalexin shows that cefaclor is noticeably superior against Citrobacter. Enterobacter and Proteus mirabilis. Only slight differences are seen against other enterobacteria and Staphylococcus aureus. Both cefaclor and cephalexin are completely ineffective against enterococci and Pseudomonas aeruginosa. Regression analysis to correlate the inhibition zone diameter and MIC of cefaclor produced a very good correlation (r = -0.9741). Using 30 mcg discs on DST agar, inhibition zones of more than 20 mm are to be interpreted as "sensitivity" and zones of less than 13 mm as "resistance".