Minimum bactericidal concentration determination

In severe bacterial infections that are difficult to eradicate, such as endocarditis or osteomyehtis, it may be important to ensure that the patient s serum remains bactericidal at the lowest, or trough, concentration in the dosing interval. Dilutions of patient s serum can be incubated with the organism isolated from the patient and the minimum bactericidal concentration determined through serial dilutions. Treatment is considered adequate if the serum remains bactericidal at a dilution of 1 8. 

Antibacterial activity testing. Determined using the broth microdilution method. Incubations were performed for 18 h using an Ominolog automated incubator (Biolog Inc. 21,124 Cabot Boulevard, Hayward, CA 94545, USA). After this period MIC were checked by eye-ball observation and all weUs plated to determine the minimum bactericidal concentration (MBC). 

The toxicity of 44 metals to the biofilms and planktonic cells of Pseudomonas fluorescens was measured and expressed as minimum inhibitory concentration, minimum bactericidal concentration, and minimum biofilm eradication concentration. Linear regression analyses wa-e conducted to determine the relationships between the measured toxicity values and the following physicochemical parameters standard reduction-oxidation potential, electronegativity, the solubility product of the corresponding metal-sulfide complex, the Pearson softness index, electron density, and the covalent index. Each of the physicochemical parameters was significantly (P < 0.05) correlated with one or more of the toxicity measurements. Heavy metal ions were found to show the strongest correlations between toxicity and physicochemical parameters. 

Aminoglycosides are most useful for bacteraemias (especially Gram-negative septicaemia) since their volume of distribution is relatively low. With the exception of patients with renal failure or endocarditis they should be administered once-daily. This is because they exhibit a dose-dependent pharmacodynamic effect. This means that bactericidal activity is determined more by the peak plasma concentration than by the time that the plasma concentration is above the minimum required to achieve bacterial killing. The converse is true of p-lactams, which exhibit t/me-cfepenofent bacterial killing. 

---