Characterization of genes involved in biosynthesis of a novel antibiotic from Burkholderia cepacia BC11 and their role in biological control of Rhizoctonia solani.

Genetic manipulation of fluorescent pseudomonads has provided major insight into their production of antifungal molecules and their role in biological control of plant disease. Burkholderia cepacia also produces antifungal activities, but its biological control activity is much less well characterized, in part due to difficulties in applying genetic tools. Here we report genetic and biochemical characterization of a soil isolate of B. cepacia relating to its production of an unusual antibiotic that is very active against a variety of soil fungi. Purification and preliminary structural analyses suggest that this antibiotic (called AFC-BC11) is a novel lipopeptide associated largely with the cell membrane. Analysis of conditions for optimal production of AFC-BC11 indicated stringent environmental regulation of its synthesis. Furthermore, we show that production of AFC-BC11 is largely responsible for the ability of B. cepacia BC11 to effectively control the damping-off of cotton caused by the fungal pathogen Rhizoctonia solani in a gnotobiotic system. Using Tn5 mutagenesis, we identified, cloned, and characterized a region of the genome of strain BC11 that is required for production of this antifungal metabolite. DNA sequence analysis suggested that this region encodes proteins directly involved in the production of a nonribosomally synthesized lipopeptide.

Double-blind randomized study of the effect of infusion rates on toxicity of amphotericin B.

Results of a double-blind randomized non-crossover study of rapid (45 min) versus slow (4 h) infusion of amphotericin B administered to 20 patients with proven or suspected fungal infection are reported. Toxicity was higher in the rapid infusion group than it was in the slow infusion group (mean total 7-day chill score, 173 +/- 276 versus 20 +/- 30 [P less than 0.01]; mean total 7-day dosage of meperidine required to abate rigors, 180 +/- 133 versus 58 +/- 78 mg [P less than 0.05]; and mean maximum total 7-day pulse rise, 225 +/- 64 versus 135 +/- 56 beats per min [P less than 0.02], respectively). When analyzed on a daily basis, the mean chill score, meperidine dosage, and pulse rise were also higher; and in addition, nausea and vomiting (5 of 11 patients who received a rapid infusion versus 0 of 9 patients who received a slow infusion [P less than 0.01]) appeared to be more common in those who received amphotericin B rapidly. The daily analysis approach proved that tolerance to these side effects developed with each subsequent infusion day, and by day 7 the incidence and severity were the same. This development of tolerance was significant for the mean chill score in the rapid infusion group (P less than 0.05) and for the proportion of patients with chills (P less than 0.005 for the slow infusion group; P less than 0.05 for the rapid infusion group). A decrease in creatinine clearance to greater than 51% of the baseline value was seen in two patients in each group. There were five deaths (four in the rapid infusion group, 1 in the slow infusion group) within 1 month, but none was clearly related to the amphotericin B infusion. The mean time to defervescence was similar for each group (10.8 +/- 4.1 days in the slow infusion group versus 9.9 +/- 5 days in the rapid infusion group). A rapid infusion regimen for amphotericin B cannot be recommended, at least during the first 5 to 7 days of treatment.

Intravenous nitroglycerin delivery: dynamics and cost considerations.

After determining initial nitroglycerin (NTG) concentrations, NTG solutions were infused through polyvinylchloride (PVC) and polyethylene intravenous (IV) administration sets at rates of 6, 12, and 24 ml/hour. Delivered NTG concentrations were determined using a high-performance liquid chromatographic technique at predetermined and fixed time intervals during a 24-hour infusion. The relative availability of NTG with each infusion was determined by dividing the area under the time concentration curve for delivered NTG by the area under the curve, assuming that the initial NTG concentration was delivered constantly over the 24-hour infusion period. For the PVC administration set, the relative availabilities of NTG were 41.5%, 62.9%, and 76.0% for the 6, 12, and 24 ml/hour infusions, respectively. Additionally, the concentration of NTG delivered varied considerably with time and infusion rate. For the polyethylene administration set, the relative availabilities of NTG were 97.3%, 96.8%, and 96.3% for the 6, 12, and 24 ml/hour infusions, respectively. Considerably less NTG solution was required to deliver the same amount of drug when polyethylene administration sets were used to infuse NTG. Polyethylene IV administration sets can be used to accurately deliver the labeled NTG concentration without resulting in increased cost.