Investigations on the species specificity of Mannheimia (Pasteurella) haemolytica serotyping

Eleven serotypes (1, 2, 5-9, 12-14 and 16) have been demonstrated within Ma nnheimia haemolytica. Subsequent serotyping of 166 Mannheimia haemolytica-l ike strains, genetically and phenotyphically distinct from Mannheimia haemo lytica, and isolated from ruminants, pigs, hares and rabbits showed that 13 .2% were typeable, 19 of which were serotype 11 representing strains now be ing classified as M. glucosida. In addition, three strains belonged to sero types 6, 9 and 16, respectively. Additionally, the serotyping results of 98 (P.) haemolytica-like isolates from non-ruminant sources collected by the UK Veterinary Investigation Centres during the period 1982-1996 were invest igated. None of these isolates have been kept, making further genetic chara cterization impossible. Among these isolates, 25.5% were typeable represent ing serotypes 1, 2, 3, 5, 6, 9, 10, 13 and 15. Substantial evidence has bee n reported indicating that M. haemolytica-like isolates from non-ruminant s ources represent species different from M. haemolytica. The present investi gation underlines that serotyping does not represent a reliable method for the identification of M. haemolytica or M. glucosida. These observations em phasize that extended phenotypic and genetic characterization is necessary for the proper identification of these organisms. (C) 1999 Elsevier Science B.V. All rights reserved.