title: The effect of antibiotics on mannose-resistant haemagglutination by K88- and K99-positive Escherichia coli strains.
abstract: Five E. coli strains carrying K99 antigen isolated from the intestines of calves which had succumbed to diarrhoea and six K88-positive strains isolated from fatal cases of diarrhoea in piglets were examined for their mannose-resistant haemagglutination (MRHA) capacity against pig erythrocytes. The bovine strains showed a geometric mean MRHA-titre of 1/18 and the porcine strains one of 1/45. Similar experiments were carried out after addition of the following antibiotics in doubling dilutions: ampicillin, chloramphenicol, colistin, dihydrostreptomycin, gentamicin, neomycin, polymyxin B and oxytetracycline. Colistin and polymyxin B had a marked concentration-dependent inhibitory effect on MRHA. Neomycin and gentamicin also inhibited MRHA but to a lesser degree. Chloramphenicol, dihydrostreptomycin and oxytetracycline showed no effect. With ampicillin, a trend was found for the ratio values to be inversely proportional to the concentration. This suggests that this antibiotic has an enhancing effect on the haemagglutination.
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000942:Antigens, Bacterial / Q000032:analysis*; D002417:Cattle / Q000382:microbiology*; D004926:Escherichia coli / Q000187:drug effects / Q000276:immunology* / Q000302:isolation & purification; D006384:Hemagglutination / Q000187:drug effects*; D006386:Hemagglutination Tests; D008358:Mannose / Q000494:pharmacology*; D013552:Swine / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D000942:Antigens, Bacterial; D008358:Mannose