Genetic relationships among Pasteurella trehalosi isolates based on multilocus enzyme electrophoresis

Abstract

Genetic diversity among 60 British Pasteurella trehalosi isolates representing the four recognized capsular serotypes, T3, T4, T I 0 and T15, and recovered predominantly from sheep suffering from systemic pasteurellosis, was estimated by analysing electrophoretically demonstrable allelic variation a t structural genes encoding 19 enzymes. Thirteen of the loci were polymorphic and 20 distinctive multilocus genotypes (electrophoretic types, ETs) were identified. The population structure of P. trehalosi is clonal and its genetic diversity is limited compared with most other pathogenic bacteria. ETs represent clones, and isolates of the same ET were generally associated with the same combination of serotype, LPS type and outer-membrane protein (OMP) type. The genetic diversity of isolates within each of the capsular serotypes varied. Serotype TI0 was represented b y 18 isolates in two related ETs and exhibited little diversity. By contrast, serotype TI5 was represented by 18 isolates in nine ETs and was almost as diverse as the species as a whole. Serotype T4 was represented by 18 isolates in five ETs and was less diverse than serotype T15. Although serotype T3 was more diverse than serotype TI5 it was represented by only three isolates. With the exception of the TI0 isolates and those recovered from healthy sheep, 35 disease isolates belonged to 16 ETs, each of which was represented by only one to four isolates. The fact that a high proportion of disease is caused by a relatively large number of clones suggests that P. trehalosi is essentially an opportunistic pathogen. In addition to having the same capsular structure, isolates belonging to the two TI0 clones were characterized by possession of similar, if not identical, O-antigens (LPS types 2 and 4). The occurrence of 18 serotype T I 0 isolates in only two ETs suggests that the TI0 capsule and type 2/4 O-antigen confer enhanced virulence on members of these two clones. Multilocus enzyme electrophoresis (MLEE) had greater resolving power than did capsule/LPS/OMP analysis, being able to distinguish 20 rather than 14 sub-divisions within P. trehalosi. The technique demonstrated genetic identity or non-identity among strains of the same or different serotypes from different geographic localities within the UK and was a useful epidemiological tool.

Sequence Diversity and Molecular Evolution of the Leukotoxin ( lktA ) Gene in Bovine and Ovine Strains of Mannheimia ( Pasteurella ) haemolytica

“…The complete nucleotide sequence of the lktA gene was determined for 31 isolates of M. haemolytica representing 12 capsular serotypes and the 22 electrophoretic types (ETs) previously defined by multilocus enzyme electrophoresis (MLEE) (13). The lktA gene was also sequenced for six isolates representing different ETs of M. glucosida (13) and for four isolates that each represent one of the capsular serotypes (T3, T4, T10, and T15) of P. trehalosi (14). Part of the lktA gene was also sequenced for an additional 13 serotype A2 isolates of M. haemolytica recovered from cattle and sheep in order to identify the allele type.…”

“…Partial lktA sequences were obtained for a further 13 serotype A2 M. haemolytica isolates of bovine and ovine origin. The 54 isolates have been well characterized in previous studies (10)(11)(12)(13)(14) and were chosen to represent selected evolutionary lineages, serotypes, and hosts of origin. Properties of these isolates are presented in Table 1.…”

The comparative pathogenicity of strains of eight serovars and untypable strains of Mannheimia haemolytica in experimental pneumonia of sheep

“…The UT isolates may represent either capsule-deficient strains or distinct species [6,19]. Furthermore, extensive epidemiological studies of M. haemolytica strains using molecular typing techniques have shown some significant level of heterogeneity even within strains of the same serovar isolated from various hosts and also from different geographical areas [7,8,16].…”

Sequence Diversity and Molecular Evolution of the Heat-Modifiable Outer Membrane Protein Gene ( ompA ) of Mannheimia ( Pasteurella ) haemolytica , Mannheimia glucosida , and Pasteurella trehalosi

“…The ompA genes from 31 M. haemolytica isolates representing 12 capsular serotypes and 22 electrophoretic types (ETs) previously defined by multilocus enzyme electrophoresis (11) were sequenced. The ompA genes from six isolates representing different ETs of M. glucosida (11) and from four isolates representing each of the capsular serotypes T3, T4, T10, and T15 of P. trehalosi (12) were also sequenced. PCR errors were shown to be insignificant by duplicate amplification and sequencing of ompA for strains PH2, PH376, and PH344.…”

“…The ompA genes from 31 M. haemolytica, 6 M. glucosida, and 4 P. trehalosi isolates were sequenced. The 41 strains were well characterized in previous studies (11)(12)(13)(14)(15)(16)(17) and were selected to represent specific evolutionary lineages, capsular serotypes, and hosts of origin. Some properties of these isolates are presented in Table 1.…”