Plasma concentration/time curve of erythromycin after a 12-hour intravenous infusion of erythromycin lactobionate in man

Real time monitoring of Staphylococcus aureus biofilm sensitivity towards antibiotics with isothermal microcalorimetry

Biofilm-associated infections with Staphylococcus aureus are difficult to treat even after administration of antibiotics that according to the standard susceptibility assays are effective. Currently, the assays used in the clinical laboratories to determine the sensitivity of S. aureus towards antibiotics are not representing the behaviour of biofilm-associated S. aureus, since these assays are performed on planktonic bacteria. In research settings, microcalorimetry has been used for antibiotic susceptibility studies. Therefore, in this study we investigated if we can use isothermal microcalorimetry to monitor the response of biofilm towards antibiotic treatment in real-time. We developed a reproducible method to generate biofilm in an isothermal microcalorimeter setup. Using this system, the sensitivity of 5 methicillin-sensitive S. aureus (MSSA) and 5 methicillin-resistant S. aureus (MRSA) strains from different genetic lineages were determined towards: flucloxacillin, cefuroxime, cefotaxime, gentamicin, rifampicin, vancomycin, levofloxacin, clindamycin, erythromycin, linezolid, fusidic acid, co-trimoxazole, and doxycycline. In contrast to conventional assays, our calorimetry-based biofilm susceptibility assay showed that S. aureus biofilms, regardless MSSA or MRSA, can survive the exposure to the maximum serum concentration of all tested antibiotics. The only treatment with a single antibiotic showing a significant reduction in biofilm survival was rifampicin, yet in 20% of the strains, emerging antibiotic resistance was observed. Furthermore, the combination of rifampicin with flucloxacillin, vancomycin or levofloxacin was able to prevent S. aureus biofilm from becoming resistant to rifampicin. Isothermal microcalorimetry allows real-time monitoring of the sensitivity of S. aureus biofilms towards antibiotics in a fast and reliable way.

The proarrhythmic effects of hypothermia in atria isolated from 5-HT4-receptor-overexpressing mice

We investigated whether hypothermia would be arrhythmogenic in mice that overexpress the human 5-HT₄ receptor only in their cardiac myocytes (5-HT₄-TG). Contractile studies were performed in isolated, electrically driven (1 Hz) left and spontaneously beating right atrial preparations of 5-HT₄-TG and littermate wild-type control mice (WT). Hypothermia (23 °C) decreased the force of contraction in the mouse right and left atrial preparations. Moreover, the concentration-dependent positive inotropic effects of 5-HT were blunted but still shifted to lower 5-HT concentrations in the left 5-HT₄-TG atria in hypothermia compared to normothermia (37 °C). Furthermore, hypothermia increased the incidence of right atrial arrhythmias in 5-HT₄-TG more than in WT mice. In contrast, at 37 °C, lowering the potassium concentration from 5.2 to 2.0 mM also induced arrhythmias in the right atrium, but with a similar incidence in WT and 5-HT₄-TG mice. In contrast, 10 μM d,l-sotalol and 300 μM erythromycin did not induce arrhythmias. Hypothermia was accompanied by the increased expression of heat shock protein 70 (HSP70) in WT but not in 5-HT₄-TG mice. We concluded that without the stimulation of 5-HT₄-receptors by exogenous agonists, a simple temperature reduction can increase arrhythmias in 5-HT₄-TG mice. It is tempting to speculate that in human patients, 5-HT₄ receptors might contribute to potentially deadly hypothermia-induced arrhythmias.

Effects of intravenous erythromycin lactobionate in respiratory infections

The antibiotic erythromycin lactobionate given intravenously acts almost exclusively on Gram-positive bacteria. Even at high plasma and tissue concentrations there is an almost total absence of side-effects. It could be considered, therefore, as first choice in the treatment of patients with infectious respiratory diseases. Most of the 40 patients admitted to the present study were elderly and all had either acute or chronic and becoming acute respiratory disease. Their clinical symptoms and levels of phlogosis improved on treatment with erythromycin lactobionate without any interruption of therapy due to side-effects and toxicity. The absence of unfavourable pharmacological interactions further enhances the usefulness of the drug. In view of the excellent response to monotherapy with erythromycin lactobionate and the few groups of resistant bacteria found in those cases when it was possible to check, it was not considered necessary to investigate any synergistic association with other antibiotics. It can be concluded, therefore, that therapy with erythromycin lactobionate in patients with infective respiratory disease is favourable and patients show excellent tolerability.

Study of serum levels, venous irritation and gastrointestinal side-effects with intravenous erythromycin lactobionate in patients with bronchopulmonary infection

Sixteen patients with bronchopulmonary infection received 500 mg erythromycin lactobionate by intravenous infusion every 8 h for 2 days. The duration of infusion was either 30 (8 patients) or 60 min (8 patients). An inline filterset (0.22 micrometer) was included in the intravenous administration set in 4 patients of each infusion group. Serum erythromycin levels were obtained before and at various times for 8 h after the first and fourth doses and before and immediately after the other doses. The incidence and severity of venous irritation and gastrointestinal side-effects were assessed. Mean (S.D.) peak erythromycin levels for the 30 min infusion were 26.31 (6.89) micrograms/ml (first dose) and 26.85 (6.11) micrograms/ml (fourth dose) and for the 60 min infusions, 23.96 (7.91) micrograms/ml (first dose) and 23.65 (6.55) micrograms/ml (fourth dose). Venous irritation was experienced by 12 patients, ranging from localized discomfort to thrombophlebitis, but the severity was significantly reduced by inline filtration (P less than 0.005). Gastrointestinal side-effects were reported by 8 patients and 1 patient withdrew because of severe abdominal pain and nausea. These symptoms were usually relieved by spasmolytic agents and possibly could be explained by high concentrations reaching the gut wall either by biliary excretion or direct transport from blood and stimulating smooth muscle motility.

Plasma, bone, hip capsule and drain fluid concentrations of ampicillin and flucloxacillin during total hip replacement after intravenous bolus injection of magnapen

1. A rapid intravenous bolus injection of 4.0 g Magnapen (which contains 2.0 g of ampicillin and 2.0 g of flucloxacillin) was to seven patients undergoing total hip replacement immediatly before induction of general anesthesia. Postoperatively the patients patients received 2.0 g Magnapen by intramuscular injection every 6 h for up to 72 h until removal of the wound drains. 2. The plasma, bone, hip capsule and drain fluid concentrations of ampicillin and flucloxacillin were measured by a differential small plate microbiological assay method using Sarcina lutea and a penicillinase producing Staph. aureus Russell as the test organisms. 3. The mean +/- s.e. mean concentrations of ampicillin after this regimen were 4222.2 +/- 285.0 microgram/ml (plasma), 65.6 +/- 1.3 microgram (g (hip capsule), 19.1 +/- 3.8 microgram/g (cancellous bone), and 211.1 +/- 65.6 microgram/g (ground up bone) respectively. 4. The mean +/- s.e. mean flucloxacillin concentrations after this regime were 137.2 +/- 28.4 microgram/ml (plasma), 61.8 +/- 15.0 microgram/g (hip capsule), 47.1 +/- 9.5 microgram/g (cancellous bone) and 139.4 +/- 21.8 microgram/g (ground up bone) respectively. 5. An intravenous bolus injection of Magnepen (4.0 g), given immediately before induction of general anaesthesia, provides concentrations of ampicillin and flucloxacillin in plasma, hip capsule, cancellous and ground up bone, and drain fluid that exceed the MICs of these antibiotics against Staph. aureus and E. coli. 6. The plasma, hip capsule, cancellous and ground up bone concentrations of ampicillin after this dose of Magnapen do not, however, exceed the MICs of the Gram negative anaerobes that sometimes cause postoperative wound infections in these patients.