The effect of antibiotics on mannose-resistant haemagglutination by K88- and K99-positive Escherichia coli strains |
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Authors: | H SØGAARD J L LARSEN† |
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Institution: | *R&D Section, Antibiotic Division, Dumex Ltd., Copenhagen;†Institute of Hygiene and Microbiology, Royal Veterinary and Agricultural University, Copenhagen, Denmark |
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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, dihydro-streptomycin, 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. |
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