Genotypic heterogeneity of Pasteurella gallinarum as shown by ribotyping and 16S rRNA sequencing

Avibacterium endocarditidis sp. nov., isolated from valvular endocarditis in chickens

A novel species of the Pasteurellaceae, Avibacterium endocarditidis sp. nov., is proposed based upon characterization of 27 isolates from valvular endocarditis in adult broiler parents. All isolates shared the same PFGE type after digestion of DNA with SmaI and XbaI. In addition, all isolates meet the phenotypic characters for the genus Avibacterium. Separation of the novel species from other species of Avibacterium was possible by means of tests for catalase, symbiotic growth, aerobic growth on agar, acid production from glycerol, xylitol, (+)-L-arabinose, (-)-D-mannitol, (-)-D-sorbitol, (-)-L-fucose, (+)-D-galactose, maltose, trehalose, raffinose and dextrin in addition to reactions with ONPG (beta-galactosidase) and PNPG (alpha-glucosidase). The closest relationship was observed with Avibacterium gallinarum which, however, can be separated from Avibacterium endocarditidis in acid production from (-)-D-mannitol, (-)-D-sorbitol and (-)-L-fucose. The highest 16S rRNA gene sequence similarity (98.4 %) was found to strain Modesto, belonging to serogroup C of Avibacterium paragallinarum. recN gene DNA sequence similarities corrected by the formula of Zeigler (2003) (Int J Syst Evol Microbiol 53, 1893-1900) documented 85 % or less DNA sequence similarity between the type strain of Avibacterium endocarditidis and species of Avibacterium, confirming the separate species status of this taxon according to the multilocus sequence analysis method of Kuhnert & Korczak (2006) (Microbiology 152, 2537-2548). The type strain of Avibacterium endocarditidis sp. nov., strain 20186H4H1(T) (=CCUG 52860(T) =DSM 18224(T)), was isolated from valvular endocarditis of a chicken in Denmark in 2004.

Comparative sequence analysis of 16S rRNA gene of Pasteurella multocida serogroup B isolates from different animal species

The phylogenetic relationships of five isolates of Pasteurella multocida serotype B:2 belonging to buffalo, cattle, pig, sheep and goat were investigated by comparative sequence analysis of 16S rRNA gene. The 1468bp fragment of 16S rRNA gene sequence comparison showed that the isolates of cattle (PM75), pig (PM49) and sheep (PM82) shared 99.9% homology with the buffalo isolate (vaccine strain P52) whereas, the goat isolate (PM86) shared 99.8% homology with the vaccine strain. The 16S rRNA gene sequences of these isolates were also found monophyletic with type B reference strain NCTC 10323 of P. multocida subsp. multocida. The present study indicated the close relationships of haemorrhagic septicaemia causing P. multocida serotype B:2 isolates of buffalo and cattle with other uncommon hosts (pig, sheep and goat).

Host-specific bacterial lineages in the taxon 2 and 3 complex of Pasteurellaceae

The aim of the investigation was to determine the genetic relationship of a phenotypically diverse strain collection of epidemiologically unrelated strains from the taxon 2 and 3 complex of Bisgaard isolated from different hosts. A total of 325 isolates belonging to the taxon 2 and 3 complex of Bisgaard was characterized phenotypically in 82 characters. The genetic relationship among a subset of 60 isolates was investigated by amplified fragment length polymorphism (AFLP). The isolates were selected aiming at including the broadest diversity with regards to phenotype and host spectrum. The results suggested a statistically clear association between AFLP clusters and the host species families Columbidae (pigeon, dove), Anatidae (duck, goose) and Psittacidae (parrot, parakeet, budgerigar), respectively. This association was further supported by results from previous whole cell protein profiling and DNA:DNA hybridization studies. In conclusion, it appears that distinct genetic lineages within the taxon 2 and 3 complex of Bisgaard have evolved specificity for host bird species of different families. The observed host specificity of taxon 2 and 3 organisms may be used in future diagnostics and studies elucidating aspects of pathogenicity and epidemiology associated with the different lineages and their respective hosts.

Investigations on the clonality of isolates ofPasteurella gallinarumobtained from turkeys in Germany

Pasteurella gallinarum has been considered an opportunistic pathogen rather than a primary pathogen for chickens. As P. gallinarum has been found to have a high genotypic diversity, one would expect a polyclonal distribution among isolates from different farms if this organism is a secondary invader. The aims of this investigation were to genetically characterize isolates obtained from outbreaks affecting several turkey farms to confirm the existence of the infection in turkeys and to investigate the genetic relationship between isolates from affected farms. A total of 17 isolates from 14 outbreaks of respiratory disease in Germany were subjected to extended phenotypic and genotypic characterization. All isolates were of the same phenotype, typical of P. gallinarum. Ribotyping of three isolates using either HpaII or HindIII showed that they had identical profiles and indicated that the isolates all originated from the same clone. Comparison with HpaII ribotypes from a previous study showed that the pattern was identical to that obtained with isolates from a Zimbabwean outbreak in chickens during 1999 to 2000. Restriction endonuclease analysis typing of 14 isolates from all 14 farms showed that they had identical profiles but these differed from those obtained with isolates from the Zimbabwean outbreak. Sequencing of the 16S rRNA gene and sequence comparisons with other Pasteurellaceae confirmed their classification as P. gallinarum. Identification of the same clone of P. gallinarum from 14 outbreaks of acute respiratory disease in turkeys within a time period of 2 months suggests a common source of infection, and that P. gallinarum probably played a primary role rather than a secondary role in the outbreaks.

Characterization of sucrose-negative Pasteurella multocida variants, including isolates from large-cat bite wounds

To validate the identification of Pasteurella multocida-like bacteria negative for acid formation from sucrose, including isolates from bite wounds caused by large cats, 17 strains were phenotypically and genotypically characterized. Phylogenetic analysis of partially sequenced rpoB and infB genes showed the monophyly of the strains characterized and the reference strains of P. multocida. The sucrose-negative strains formed two groups, one related to reference strains of P. multocida and the other related to a separate species-like group (taxon 45 of Bisgaard). DNA-DNA hybridization further documented the species-like nature of this group. Ribotyping showed the heterogeneity of all strains except four strains that shared the same ribotype and that were isolated from bovine lungs. Phylogenetic analysis by 16S rRNA sequence comparison showed the monophyly of the strains characterized and the reference strains of P. multocida. Two strains isolated from leopard bite wounds were related to the type strain of P. dagmatis; however, they represented a new taxon (taxon 46 of Bisgaard), in accordance with their distinct phenotypic and genotypic identifications. The present study documents that sucrose-negative strains of P. multocida-like bacteria belong to two genotypically distinct groups. The study further confirms the phenotypic heterogeneity of P. multocida strains and documents two new species-like taxa of Pasteurella related to P. multocida. Until diagnostic tools have been further elaborated, special care should be taken in the identification of Pasteurella-like bacteria isolated from bite wounds caused by large cats. The evidence of phenotypic and genotypic divergence calls for the further development of PCR tests and DNA sequencing to document doubtful isolates.

Reclassification of Pasteurella gallinarum, [Haemophilus] paragallinarum, Pasteurella avium and Pasteurella volantium as Avibacterium gallinarum gen. nov., comb. nov., Avibacterium paragallinarum comb. nov., Avibacterium avium comb. nov. and Avibacterium volantium comb. nov

This paper describes a phenotypic and genotypic investigation of the taxonomy of [Haemophilus] paragallinarum, Pasteurella gallinarum, Pasteurella avium and Pasteurella volantium, a major subcluster within the avian 16S rRNA cluster 18 of the family Pasteurellaceae. An extended phenotypic characterization was performed of the type strain of [Haemophilus] paragallinarum, which is NAD-dependent, and eight NAD-independent strains of [Haemophilus] paragallinarum. Complete 16S rRNA gene sequences were obtained for one NAD-independent and four NAD-dependent [Haemophilus] paragallinarum strains. These five sequences along with existing 16S rRNA gene sequences for 11 other taxa within avian 16S rRNA cluster 18 as well as seven other taxa from the Pasteurellaceae were subjected to phylogenetic analysis. The analysis demonstrated that [Haemophilus] paragallinarum, Pasteurella gallinarum, Pasteurella avium and Pasteurella volantium formed a monophyletic group with a minimum of 96·8 % sequence similarity. This group can also be separated by phenotypic testing from all other recognized and named taxa within the Pasteurellaceae. As both genotypic and phenotypic testing support the separate and distinct nature of this subcluster, the transfer is proposed of Pasteurella gallinarum, [Haemophilus] paragallinarum, Pasteurella avium and Pasteurella volantium to a new genus Avibacterium as Avibacterium gallinarum gen. nov., comb. nov., Avibacterium paragallinarum comb. nov., Avibacterium avium comb. nov. and Avibacterium volantium comb. nov. The type strains are NCTC 1118T (Avibacterium gallinarum), NCTC 11296T (Avibacterium paragallinarum), NCTC 11297T (Avibacterium avium) and NCTC 3438T (Avibacterium volantium). Key characteristics that separate these four species are catalase activity (absent only in Avibacterium paragallinarum) and production of acid from galactose (negative only in Avibacterium paragallinarum), maltose (negative only in Avibacterium avium) and mannitol (negative in Avibacterium gallinarum and Avibacterium avium).