Drug-susceptibility and isolation of a plasmid in Haemophilus (Actinobacillus) pleuropneumoniae.

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Abstract
We isolated 56 Haemophilus (Actinobacillus) pleuropneumoniae strains from the pneumonic porcine lung tissues and tested them for antimicrobial susceptibility. Two drug-resistant strains were obtained. One, named KH-265, was resistant to streptomycin (SM) and sulfonamide (SA), and the other, named KH-195, was resistant to tetracycline (TC). The minimum inhibitory concentrations (MICs) of drugs for resistant strains were 100 .mu.g/ml for SM, 3200 .mu.g/ml for SA, and 12.5 .mu.g/ml for TC. KH-265 possessed a 8.3Kb nonconjugative plasmid, pMS260, encoding SM and SA resistance, which was transformable to Escherichia coli strains. pMS260 belonged to ine of 14 incompatibility groups including Inc. P and Inc. Q, so far tested. It was mobilizable to various causative strains for respiratory infections, Pseudomonas aeruginosa, Bordetella bronchiseptica, Pasteurella multocida and Haemophilus pleuropneumoniae, by RP4 (Inc. P) plasmid.