Bacterial killing by use of once daily gentamicin dosage in guinea pigs with Escherichia coli infection.

OBJECTIVE: To determine whether the antibacterial activity of 6 mg of gentamicin/kg of body weight given SC once daily, is equivalent to the standard gentamicin dose of 2 mg/kg given SC every 8 hours. ANIMALS: Guinea pigs with infected thigh wound: 5 in an untreated control group and 12 in 6 and 2 mg/kg gentamicin treatment groups. PROCEDURE: Guinea pigs were inoculated with 10(9) Escherichia coli in the thigh muscle. Gentamicin treatment (2 mg/kg, SC, q 8 h or 6 mg/kg, SC, q 24 h) was begun 4 hours after E coli inoculation and continued for 72 hours. Four hours after the last gentamicin treatment, all guinea pigs were euthanatized and the cranial thigh muscle containing the entire inoculum was removed. Colony-forming units were counted to determine the E coli concentration in each thigh. RESULTS: Mean +/- SD log10 colony-forming units was 9.293 +/- 0.074 in the control group, 8.161 +/- 0.478 in the 2 mg/kg treatment group, and 7.796 +/- 0.182 in the 6 mg/kg treatment group. One-way ANOVA revealed a significant (P < 0.05) difference between the control group and both treatment groups, and between both treatment groups. CONCLUSION: Bacterial killing did not differ between gentamicin given at a dosage of 6 mg/kg once daily, compared with 2 mg/kg every 8 hours in guinea pigs infected with E coli. CLINICAL RELEVANCE: Gentamicin dosage regimens with high peak concentration and long dosing interval are as efficacious as divided dosage regimens. These data support the concept that once daily administration of gentamicin for treatment of E coli infection should be investigated clinically.

Effect of implant variables on temperatures achieved during ferromagnetic hyperthermia.

Effects of ferromagnetic implant variables on steady-state temperature were studied in both in vitro (phantom) and in vivo (rabbit hind limb musculature) models. Thermoseed implant variables included: (1) the presence and number of thermoseed sleeves; (2) variations in thermoseed alignment within the oscillating electromagnetic field; (3) generator power levels of 300 W, 600 W, and 1200 W; and (4) separation of thermoseed tracks by 0.8 cm versus 1 cm. When the thermoseeds were aligned parallel to the electromagnetic field, temperature distributions in the in vivo model using bare thermoseeds and thermoseeds encased in a single sleeve (0.1 mm wall thickness) of polyethylene tubing were statistically higher than in tests performed with thermoseeds encased in a double sleeve (0.25 mm over 0.1 mm wall thickness) of tubing (p = 0.006). Nonetheless, average steady-state temperatures above a therapeutic minimum (greater than or equal to 42 degrees C) were achieved at all generator power levels using thermoseeds encased in a double sleeve of tubing and aligned parallel to the electromagnetic field. Gross misalignment of thermoseeds with the electromagnetic field was partly compensated for by utilizing higher generator power levels. Thermoseed tracks separated by 0.8 cm and aligned parallel to the electromagnetic field yielded average steady-state temperatures that were 0.4-2.2 degrees C higher than those obtained with a thermoseed track separation of 1 cm.