In vitro antibacterial activity of florfenicol against Actinobacillus pleuropneumoniae

A total of 90 strains of Actinobacillus pleuropneumoniae isolated from porcine pneumonic lungs in Japan during 1989 to 1993 were investigated for their in vitro susceptibility to florfenicol (a derivative of thiamphenicol) and other drugs. The minimal inhibitory concentrations of florfenicol against A. pleuropneumoniae ranged from 0.2 to 1.56 micrograms/ml with a peak at 0.39 microgram/ml. Florfenicol showed a high antibacterial activity against A. pleuropneumoniae regardless of the sensitivity of the strains to thiamphenicol.

[Arterial redistribution to prevent hepatic arterial occlusion and gastric ulcer using hepatic arterial infusion chemotherapy with percutaneous catheterization]

Clinical usefulness of arterial redistribution using steel coils to prevent hepatic arterial occlusion and gastric ulcer was compared with the conventional method. Fifty-two patients with liver malignancies were inserted with steel coils into the common hepatic artery after percutaneous hepatic catheterization (CHA-coil) to prevent hepatic arterial occlusion. The tip of the indwelling catheter was fixed to the vascular wall, and the contact area between the catheter and blood into the liver became smaller. Fifty-nine other patients were inserted with steel coils into the right gastric artery (RGA-coil) to prevent gastric ulcer. The CHA-coil succeeded in 84% of the patients, and hepatic arterial occlusion occurred in only 4% of these patients. The RGA-coil succeeded in 88%, and gastric ulcer occurred in 2%. The rates of hepatic arterial occlusion (4%) and gastric ulcer (2%) were much decreased in comparison with 25% and 16%, respectively, in the previous cases undergoing percutaneous hepatic catheterization without such arterial redistribution. In conclusion, these procedures are highly effective to prevent complications of hepatic arterial infusion employing percutaneous hepatic catheterization and to allow continuation of arterial infusion chemotherapy for longer periods.

Role of Bacteroides uniformis in susceptibility of Ta:CF# 1 mice to infection by Treponema hyodysenteriae

Among the various strains and colonies of mice tested specific-pathogen-free (SPF) Ta:CF#1 mice exhibited the highest susceptibility to Treponema hyodysenteriae infection. Staphylococcus epidermidis 1047, Streptococcus faecalis 2039, Lactobacillus murinus 3010, Escherichia coli 1049, and Bacteroides thetaiotaomicron 3008 were administered to the Ta:CF#1 mice. B. uniformis IK, which appeared to colonize in the breeding facility under SPF conditions, was isolated from the cecal content of a Ta:CF#1 mouse and identified in the mouse flora. Germfree mice were infected with these six bacteria and challenged with T. hyodysenteriae DJ70P3 to elucidate the causal relationship between these bacteria and the sensitivity of mice to T. hyodysenteriae infection. No cecal lesions were observed in gnotobiotic mice either monoassociated with T. hyodysenteriae DJ70P3 or B. uniformis IK or inoculated with T. hyodysenteriae DJ70P3 combined with the 5 a.m. strains. Gross cecal lesions appeared only in mice inoculated with T. hyodysenteriae DJ70P3 combined with B. uniformis IK. A new SPF mouse colony (CF#1/b Ta) established from gnotobiotic mice by inoculation with B. uniformis IK and the 5 laboratory stock cultures was as susceptible to T. hyodysenteriae as the original Ta:CF#1 mice. This suggests that B. uniformis IK plays an important role in the high susceptibility of Ta:CF#1 mice to T.hyodysenteriae.

In vitro and in vivo activities of sedecamycin against Treponema hyodysenteriae

Sedecamycin (lankacidin A), one of the lankacidin-group antibiotics, showed potent activity against Treponema hyodysenteriae. The MICs of sedecamycin against 79 field isolates of T. hyodysenteriae ranged from 0.78 to 12.5 micrograms/ml, the MIC for 90% of the strains tested (MIC90) being 3.13 micrograms/ml. The protective and therapeutic effects of sedecamycin were compared with those of carbadox, tiamulin, and lincomycin against experimental infection with T. hyodysenteriae in mice. The protective effect of sedecamycin was similar to that of carbadox, two times more potent than that of tiamulin, and three times greater than that of lincomycin. In the therapeutic test, sedecamycin showed activity similar to that of carbadox and was two times more active than both tiamulin and lincomycin. At doses of 10 mg or more of sedecamycin per kg, the recurrence of shedding of T. hyodysenteriae into the feces of mice was not detected for at least 8 weeks postmedication.

Eliminating organisms against Treponema hyodysenteriae in the gut of mice

Ta:CF#1 mice lost their high susceptibility to Treponema hyodysenteriae infection after being mingled with Slc:ICR mice which had no susceptibility to the infection. Ta:CF#1 mice also lost susceptibility to the infection after being treated orally with fecal suspensions from Slc:ICR mice; treatment with heated (70 degrees C, 15 min) or filtered (pore size 0.2 micron) fecal suspensions did not cause a loss of susceptibility. Furthermore, even after the infection had established, Ta:CF#1 mice became free from T. hyodysenteriae and cecal lesions by oral treatment with the fecal suspensions. When Slc:ICR mice were treated with spectinomycin throughout the experiment, they became susceptible to the infection. These studies indicate that there exist eliminating organisms against T. hyodysenteriae in the gut of mice.

Experimental Treponema hyodysenteriae infection of mice

Factors such as strain, fasting period, sex and age of the animals, and challenge dose were examined for their effects on the development of infection with Treponema hyodysenteriae in mice. Among mice tested, Ta:CF#1 mice were the most susceptible to the infection. Ta:CF#1 mice developed gross cecal lesions by a single oral dose ranging 10(2)-10(7) colony-forming units of T. hyodysenteriae without preinoculation fast. Oral challenge with 10(7) colony-forming units of the treponeme resulted in the development of gross lesions in all the mice at day 10. The number of T. hyodysenteriae in the feces and cecum of the mice reached the highest level at day 7 and 10, respectively; the levels lasted until day 21, the termination of the experiment. Macroscopic, microscopic and scanning electron microscopic findings of the lesions were similar to those of swine dysentery. These studies indicate that the Ta:CF#1 mice may be used as an excellent in vivo model system for swine dysentery.

Experimental infection with Treponema hyodysenteriae in nude mice

Compared with phenotypically normal heterozygous (nu/+) littermates, congenitally athymic, BALB/c nude (nu/nu) mice inoculated with a single oral dose of Treponema hyodysenteriae had a higher incidence of cecal lesions.