Characterization of Haemophilus paragallinarum isolates from Mexico.

The carbohydrate fermentation, antimicrobial drug resistance and serological properties of 40 isolates of Haemophilus paragallinarum from outbreaks of infectious coryza in Mexico are described. Four biochemical biovariants and five antimicrobial drug resistance patterns were recognized. All isolates were serotyped by the Page scheme, with 21 isolates being assigned to serogroup A, five isolates to serogroup B and 14 isolates to serogroup C.

Serotyping of Haemophilus paragallinarum isolates from Mexico by the Kume hemagglutinin scheme.

A total of 42 isolates of Haemophilus paragallinarum from Mexico were serotyped by the Kume hemagglutinin scheme. Serovars A-1, A-2, B-1, and C-2 were recognized among 11 (26.2%), 7 (16.6%), 4 (9.5%), and 14 (33.3%) isolates, respectively. A further six isolates (14.3%) showed hemagglutinating activity but could not be classified into any serovar. Commercial vaccines containing Kume serovars A-1, A-2, B-1, and C-2 may provide better protection than those bi- or trivalent infectious coryza vaccines currently used in Mexico.

Adherence of Pasteurella multocida to rabbit respiratory epithelial cells in vitro.

Adult clinically healthy New Zealand rabbits were sampled bacteriologically to detect carriers and non-carriers of Pasteurella multocida. Both groups of rabbits were killed separately to obtain samples of nasal, buccal, pharyngeal and tracheal epithelial cells. The cells were tested for adherence in vitro to 18 isolates of P. multocida from healthy and sick rabbits, from ovine, bovine, cat and swine. The number of bacteria adhered per cell up to 25 cells per preparation were registered. Analysis of variance was used to interpret the significance of results. Adherence of P. multocida was significantly higher to carrier rabbit cells than to non-carrier rabbit cells. Bacterial isolates from rabbits were more adherent to rabbit cells than to isolates from other species. The frequency was higher to buccal and pharyngeal cells than to nasal and tracheal cells. Isolates from healthy animals adhered better to rabbit cells than isolates from sick animals, except the isolates from sick animals which adhered better to nasal cells of non carriers than did isolates from healthy rabbits.

A comparison of various Haemophilus somnus strains.

Sixty-eight Haemophilus somnus strains isolated from the bovine in Canada and the U.S.A. were compared. In media enriched with 5% ovine serum, 5% bovine serum and 10% yeast extract, H. somnus fermented glucose, levulose, maltose, mannitol, mannose, sorbitol, trehalose and xylose, but failed to ferment arabinose, dulcitol, galactose, inositol, lactose, raffinose, rhamnose, salicin and sucrose. The organisms acidified litmus milk, produced cytochrome oxidase, indole and hydrogen sulfide (H(2)S) and reduced nitrates to nitrites. The motility, methyl-red, acetylmethyl-carbinol urease catalase, citrate, malonate, lysine, ornithine and arginine tests were negative. Haemophilus somnus was resistant to lincomycin, neomycin and triple sulfa, but susceptible to ampicillin, chloramphenicol, streptomycin, penicillin and tetracycline. No antigenic differences were noted between strains when tested against rabbit antisera of eight strains using agglutination, complement-fixation, immunodiffusion and counterimmunoelectrophoresis tests. Low titre cross-reactions were found in the agglutination tests with some of the anti-H. somnus rabbit sera with Actinobacillus lignieresi and Moraxella bovis. No distinct antigenic similarities to nine other species of pathogenic bacteria of animal origin were found. No difference was observed between H. somnus isolates from Ontario and those from western Canada and the U.S.A.