Further comparative studies of the action of demethylchlortetracycline and of tetracyclyne hydrochloride on brucella melitensis and on salmonella typhi

Abstract

Work described in a previous paper consisting of a study of the action of demethylchlortetracycline and of tetracycline hydrochloride on newly isolated strains of Brucella melitensis was continued, using the technique and methods described in that paper. Both antibiotics were tested at 10 concentrations, ranging from a concentration of 0.19 5 mcg/ml (referred to as << concentration 10 >> to a concentration of 10 mcg/ml (referred to as << concentration 1 >>), using a doubling up system. The strains of Brucella melitensis had been isolated from human cases by culture from venous blood. Strain 4829/59 had been isolated on the 14/10/59, strain 4859/59 on 16/10/59, strain 5075/59 on 29/10/59, strain 5679/59 on 7/12/59, and strain 5779/59 on 15/12/59. As in previous tests it was found that none of these strains grew in 24 hours even in the absence of antibiotics, as is normallv the case with Brucella which is known to be a slow grower so ·inhibition can only be spoken of in connection with growths older than twenty four hours. The period of observation was 10 days and the average results are given in Table 1.