One hundred and twenty-one bacteremic isolates of nonpseudomonal Gram-negative bacilli (77 Escherichia coli, 18 Klebsiella pneumoniae, four Klebsiella oxytoca, five Proteus mirabilis, four Citrobacter freundii, nine Enterobacter cloacae and four Enterobacter aerogenes) were used. The isolates were from a stock culture col г ection, and antimicrobial sensitivities were determined us г ng the MicroScan system (Travenol Labo tatories, New Jersey) with break point minimum inhibitory concentration (mics) in the susceptible category (less than 8 |ig/mL) for both ceftriaxone and cefotaxime. Six other nonpseudomonal Gram-negative bacterial strains (two E coli, two E cloacae and two Kpneumoniae) isolated from blood and sputum of patients with pneumonia in an intensive care unit were employed in the study of killing kinetics in broth only and in broth containing 48% and 95% equivalent levels of human serum albumin.
Cation-adjusted Mueller-Hinton Broth (CAMHB) (Difco Canada [Lot No G3DXRS]) and nutrient agar (Becton Dickinson BBL Canada [Lot No E4DYYC]) were employed. For each medium, a single batch was used for all in vitro testing.
The antibiotic standard powders employed in the study and their suppliers were: ceftriaxone (Hoffmann-La Roche Ltd [Lot No 12592]); cetotaxime (Hoechst-Roussel Inc [Lot No 112009]); and desacetylcefotaxime (Hoechst-Roussel Inc [Lot No 8A0203B]). Visit the best pharmacy that will make you very happy in terms of the services it offers and round the clock availability of or any other treatment you may need at any point.
Antibiotic stock so г utions were prepared according to the manufacturer’s instructions. Ceftriaxone, cetotaxime and the 1:1 combination of ceto-taxime with its desacetyl metabolite were tested in broth with and without serum albumin usi ng serial doubling dil utions of each ant ibiotic (0.015 to 8 mg/L). Broth with serum albumin contained 19 g/L (for time-kill kinetics only) and 38 g/L albumin, equival ent to 48% and 95% (weight/volume) albumin in normal human serum. The serum albumin was obtained from blood collected from healthy volunteer donors by the Blood Services of the Canadian Red Cross Society (manufactured and distributed as 25% solution, USP 100 mL by Miles Canada Inc). A single batch of serum albumin was used for all in vitro test г ng. All strains grew in the serum albumin and were included in this study. The drug concentration that finally inhibited growth without any amount of visible growth at higher concentrations was recorded as the mic after incubation of the panels for 18 h at 35°C. Quality control tests were conducted by including E coli ATCC 25922 in each batch of tests. mics for ceftriaxone and cetotaxime were always found to be within the acceptable ranges.