In Vitro Activities of Two Ketolides, HMR 3647 and HMR 3004, against Gram-Positive Bacteria

ABSTRACT The in vitro activities of two new ketolides, HMR 3647 and HMR 3004, were tested by the agar dilution method against 280 strains of gram-positive bacteria with different antibiotic susceptibility profiles, including Staphylococcus aureus,Enterococcus faecalis, Enterococcus faecium,Streptococcus spp. (group A streptococci, group B streptococci, Streptococcus pneumoniae, and alpha-hemolytic streptococci). Seventeen erythromycin-susceptible (Ems), methicillin-susceptible S. aureus strains were found to have HMR 3647 and HMR 3004 MICs 4- to 16-fold lower than those of erythromycin (MIC at which 50% of isolates were inhibited [MIC50] [HMR 3647 and HMR 3004], 0.03 μg/ml; range, 0.03 to 0.06 μg/ml; MIC50 [erythromycin], 0.25 μg/ml; range, 0.25 to 0.5 μg/ml). All methicillin-resistant S. aureus strains tested were resistant to erythromycin and had HMR 3647 and HMR 3004 MICs of >64 μg/ml. The ketolides were slightly more active against E. faecalis than against E. faecium, and MICs for individual strains varied with erythromycin susceptibility. The MIC50s of HMR 3647 and HMR 3004 against Ems enterococci (MIC ≤ 0.5 μg/ml) and those enterococcal isolates with erythromycin MICs of 1 to 16 μg/ml were 0.015 μg/ml. E. faecalis strains that had erythromycin MICs of 128 to >512 μg/ml showed HMR 3647 MICs in the range of 0.03 to 16 μg/ml and HMR 3004 MICs in the range of 0.03 to 64 μg/ml. In the group of E. faecium strains for which MICs of erythromycin were ≥512 μg/ml, MICs of both ketolides were in the range of 1 to 64 μg/ml, with almost all isolates showing ketolide MICs of ≤16 μg/ml. The ketolides were also more active than erythromycin against group A streptococci, group B streptococci,S. pneumoniae, rhodococci, leuconostocs, pediococci, lactobacilli, and diphtheroids. Time-kill studies showed bactericidal activity against one strain of S. aureus among the four strains tested. The increased activity of ketolides against gram-positive bacteria suggests that further study of these agents for possible efficacy against infections caused by these bacteria is warranted.

Evidence for Disseminated Intravascular Coagulation in Newborns with Streptococcal Sepsis

Neonatal sepsis with Streptococci group B has a high mortality rate. 10 of our 13 patients died within a few days. In all patients we found low platelet counts. However, only the non-survivors showed additional coagulation findings compatible with DIC (low plasma coagulation factors, low plasminogen proactivator level, increased fibrin-fibrinogen degradation products, and low granulocyte numbers). Clinical symptoms were not present until shortly before death. The diagnosis of DIC was confirmed at autopsy. The clinical course was unchanged inspite of adequate antibiotic therapy. In 3 cases therapy with heparin or exchange transfusion was unsuccesful.

A SEROLOGICAL DIFFERENTIATION OF SPECIFIC TYPES OF BOVINE HEMOLYTIC STREPTOCOCCI (GROUP B)

Under uniform diet conditions the normal bile fistula dog will eliminate pretty constant amounts of cholesterol—about 0.5 to 1.0 mg. cholesterol per kilo per 24 hours. Diets rich in cholesterol (egg yolk) will raise the cholesterol output in the bile but compared to the diet intake (1.5 gm. cholesterol) the output increase in the bile is trivial (5–15 mg.). Calves' brains in the diet are inert. Bile salt alone will raise the cholesterol output in the bile as much and often more than a cholesterol rich diet. Bile salt plus egg yolk plus whole bile give maximal output figures for bile cholesterol—60 mg. per 24 hours. Liver injury (chloroform) decreases both bile salt and cholesterol elimination in the bile. Blood destruction (hydrazine) fails to increase the bile cholesterol output and this eliminates the red cell stroma as an important contributing factor. Certain cholagogues (isatin and decholin) will increase the bile flow but cause no change in cholesterol elimination. The ratio of cholesterol to bile salt in the bile normally is about 1 to 100 but the bile salts are more labile in their fluctuations. The ratio is about reversed in the circulating blood plasma where the cholesterol is high (150–300 mg. per cent) and the bile salt concentration very low. Cholesterol runs so closely parallel to bile salt in the bile that one may feel confident of a physical relationship. In addition there is a suspicion that the bile cholesterol is in some obscure fashion linked with the physiological activity of hepatic epithelium.