Dilution technique for isolation of Haemophilus from swine lungs collected at slaughter

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Abstract
A total of 307 lungs obtained from a slaughterhouse were cultured by a dilution technique for the isolation of Haemophilus spp. The technique consisted of serial (10-fold) dilutions of the tissue samples to a dilution of 10-5. Two selective media were used. L broth consisted of a basal brain heart infusion broth containing 5% horse serum, 5% yeast extract, 100 .mu.g of NAD and 0.5 .mu.g of lincomycin/ml. L-B broth was identical to L broth, except 1.5 .mu.g of bacitracin/ml was included. The broths were incubated overnight and then plated onto blood agar. A total of 83 (27%) isolates were obtained and both media were necessary, as a proportion of isolates grew in 1 medium but not in the other. Of the isolates, 66.3% were urease positive and most of these (98%) were classified as minor group strains. Urease-negative strains (27.7%) were classified as H. parasuis.