For minimum bactericidal concentration (mbc) determinations, duplicate 0.01 mL samples were removed from each well without growth and dispensed by spread г ng across the surface of nutrient agar plates. Results were recorded after incubation of plates for 18 h at 35°C. The initial inocula were determined and ranged from 3 to 4×105 colony-forming units (cfu)/mL. The mbc was detined as the lowest concentration producing at least 99.9% killing of the original inoculum, using the appropriate rej ection values described by Pearson et al.
Bactericidal activity of ceftriaxone and cefotaxime against six nonpseudomonal Gram-negative bacteria was also measured using the time-kill kinetic method. The antibiotic concentrations that were used rep resented the mbc for each strain tested. Inoculated broths containing approximately 3.5×105 cfu/mL and antibiotic were incubated, and at 0, 1, 2, 4, 6, 18 and 24 h intervals, a 0.01 mL aliquot was removed from each of the sample tubes and serially di г uted (1:10). A 0.1 mL of di г uent was plated on nutrient agar. Viable counts were det ermined after incubation of the plates for 18 h at 35°C. The bacterial survival measured as log10 cfu was plotted against time (hours). A time-kill curve was established for each strain. The negative effect of serum albumin on bacterial killing was assessed by a 2log10 or greater increase in cfu (100-fold decrease in killing) at 6 h instead of 24 h for the convenience of plotting and extrapolation. Best quality drugs are something you have been looking for all this time? Then you will be happy to find out you can purchase easily and for very little money now that you have the best pharmacy at your service.
For data analyses, mic and mbc results less than 0.015 and greater than 8 mg/L were converted to 0.007 and 16 mg/L. Parametric tests were used to test for differences among the means of the natural logarithmic transformed measurements (ie, geometric means). Two-way analysis ol variance (anova) was used to determine whether there was an interaction between antibiotic and serum albumin concentration. One-way anova was used to determine whether there were differences among antibioti cs at each of the serum albumin concentrations. When differences occurred, the Scheffe post-hoc test indicated which mean(s) differed significantly from the others.