[Immunoprophylaxis of Salmonella infection caused by S. dublin in calves]. / Vurkhu imunoprofilaktikata na salmonelozata po teletata, prichiniavana ot S. dublin.

Studied is the active immunoprophylaxis of calves on farms with a Salmonella dublin infection, using a live vaccine produced with a S. dublin attenuated strain. The disease was fully suppressed among calves through vaccination after the tenth day following birth. However, the source of infection was not done away with, and it was most likely to be found in adult cattle. This was reasonable to believe as there was a second outbreak of the disease in a group of unvaccinated, newborn calves. The regular vaccination is suggested of all newborn calves up to the time when the adult population would occasionally be replaced.

[Streptococcal infection in newborn lambs]. / Streptokokova infektsiia po novorodeni agneta.

A disease was observed in newborn lambs with a high mortality rate. Streptococcus zooepidemicus was isolated from dead lambs. The disease was reproduced through the intratracheal infection of lambs with a culture of the isolated organism. The picture of septicaemia was observed, strong symptoms of the disease being noticed with the involvement of the respiratory system. The morphologic changes were mainly seen within the region of the lungs, pleura, and pericardium. Histologically, there were lesions characteristic of an acute septic process. It was concluded that Streptococcus zooepidemicus was highly pathogenic for young lambs.

[Transmissible drug resistance in strains of E. coli isolated from birds]. / Prenosima lekarstvena ustoichivost pri shtamove E. coli, izolirani ot ptitsi.

A total of 97 strains of Escherichia coli, resistant either to one or to several theraupeutic agents and isolated from young and adult birds, were studied for the presence of transmissible R plasmids. Transmissible drug resistance was demonstrated with 37 per cent of the strains. The transmission of such resistance was manifested in highest percent in the case of ampicillin and chloramphenicol, followed by sulphathiazole and tetracycline. The R plasmids established in multi-drug resistant strains with three markers and more, were found to bear high percent determinants of resistance to chloramphenicol and in lower percent such to sulphathiazole and tetracycline. The same strains presented R plasmids that bore determinants of resistance to five therapeutic agents (Tc, Su, Cm, Mm, Nm) and to three therapeutic agents (Cm, Ap, Tc) and (Cm, Su, Km).

[Changes in the drug resistance of coliform bacteria in the digestive tract of poultry under the influence of antibiotics at different dosages]. / Izmeneniia v lekarstvenata chuvstvitelnost na koliformnite bakterii v khranosmilatelniia trakt na ptitsi pod vliianie na antibiotitsi v razlichni dozi.

Changes in drug-sensitivity of hen intestinal flora following various chloramphenicol, kanamycin and gentamycin dose applications to the fodder rations were studied under experimental conditions. Selection of resistant strains was observed following chloramphenicol application of "nutrient", prophylaxis and medicative doses as well as selection of strains resistant to 6 antibiotics following chloramphenical, kanamycin and gentamycin application in medicative doses. It was proven that some of these strains are carriers of conjugative plasmides possessing markers of tetracycline-, chrloamphenical-, kanamycin-, spectinomycin-, ampicylin- and gentamycin-resistance.

[Drug resistance of the Salmonella isolated from poultry]. / Vurkhu lekarstvenata ustoichivost na salmoneli, izolirani

A total of 92 Salmonella strains, isolated from birds, were studied through graded dilutions in a solid nutrient medium for their resistance to penicillin, streptomycin, chloramphenicol, tetracycline, furazolidon and norsulfazol. Greatest was the number of strains resistant to penicillin (81.5 per cent), and lowest was it of strains resistant to tetracycline (27.1 per cent), norsulfazol (21.7 per cent), streptomycin (15.2 per cent), and furazolidon (1.08 per cent). No resistant strains were found to chloramphenicol. Both furazolidon and chloramphenicol are suggested for the control of Salmonella infections in birds.