ABSTRACT
The bactericidal activities of ABT-773, a new ketolide, were compared to those of cefuroxime and amoxicillin-clavulanate against 10 strains of Streptococcus pneumoniae containing the ermB gene. MICs and time-kill curves were determined in duplicate per NCCLS guidelines with cation-adjusted Mueller-Hinton broth with 3% lysed horse blood. Viable counts were done at 0, 2, 6, and 24 h. Antibiotic concentrations tested were two and eight times the MIC. ABT-773 MICs ranged from 0.008 to 1.0 micro g/ml. Bactericidal activity was observed with ABT-773 at eight times the MIC against 4 of 10 strains at 24 h compared to 10 of 10 strains with the beta-lactam antibiotics.
Subject(s)
Erythromycin/analogs & derivatives , Erythromycin/pharmacology , Ketolides , Methyltransferases/genetics , Streptococcus pneumoniae/drug effects , Streptococcus pneumoniae/genetics , Amoxicillin-Potassium Clavulanate Combination/pharmacology , Cefuroxime/pharmacology , Cephalosporins/pharmacology , Culture Media , Drug Therapy, Combination/pharmacology , Humans , Kinetics , Microbial Sensitivity Tests , Pneumococcal Infections/microbiologyABSTRACT
The influence of bacterial strain and antibiotic concentration on the time to achieve in vitro bactericidal activity was determined for gatifloxacin and ciprofloxacin using time-kill methodology. Killing rates were significantly affected by bacterial strain, antibiotic concentration, and type of fluoroquinolone. The most rapid bactericidal activity was seen against members of the Enterobacteriaceae and with fluoroquinolone concentrations of 8-16 X MIC. In general, gatifloxacin demonstrated faster killing against Acinetobacter baumanii, Legionella pneumophila, Staphylococcus aureus, and Streptococcus pneumoniae.
Subject(s)
Anti-Infective Agents/pharmacology , Ciprofloxacin/pharmacology , Fluoroquinolones , Gram-Negative Bacteria/drug effects , Gram-Positive Bacteria/drug effects , Blood Bactericidal Activity , Dose-Response Relationship, Drug , Gatifloxacin , Humans , Microbial Sensitivity Tests , Sensitivity and SpecificitySubject(s)
Amoxicillin-Potassium Clavulanate Combination/pharmacology , Bacteria, Anaerobic/drug effects , Drug Therapy, Combination/pharmacology , Erythromycin/analogs & derivatives , Erythromycin/pharmacology , Ketolides , Bacteroides fragilis/drug effects , Kinetics , Microbial Sensitivity Tests , Peptostreptococcus/drug effectsABSTRACT
The bactericidal activity of ABT-773 was compared with amoxicillin against 10 clinical isolates of S. pyogenes (six erythromycin susceptible and four erythromycin resistant). The MIC ranges (mg/L) were 0.004-0.25 of ABT-773 and 0.015-0.12 of amoxicillin. At 24 h, ABT-773 concentrations of 2 x MIC and 8 x MIC were bactericidal against three and six organisms, respectively. In comparison, amoxicillin was bactericidal against all 10 organisms at both test concentrations.
