Molecular characterization of isolates ofHaemophilus paragallinarumfrom China by ribotyping

Identification, HPG2 Sequence Analysis, and Antimicrobial Susceptibility of Avibacterium paragallinarum Isolates Obtained from Outbreaks of Infectious Coryza in Commercial Layers in Sonora State, Mexico

This is the first extensive report on the identification and characterization of Avibacterium paragallinarum (AVP) isolates obtained from outbreaks of infectious coryza (IC) in IC-vaccinated layer flocks from Sonora State in Mexico. Isolates obtained from IC outbreaks during the years 2007, 2014, 2015, 2017, and 2019 were identified by conventional PCR test and 16S rRNA gene analysis, serotyped by Page serotyping and genotyped by the recently described partial sequence analysis of the HPG2 region. Furthermore, antimicrobial susceptibility profiles were determined by a recently improved minimal inhibitory concentration (MIC) test. The conventional PCR test and the 16S rRNA analyses confirmed the isolates as AVP. Serotyping results showed the involvement of isolates belonging to serotypes A, B, and C in the IC outbreaks. Genotyping of the HPG2 region revealed the presence of sequence type (ST)1, ST4, and ST11, of which the latter has also been identified in Europe. The MIC susceptibility test showed that all tested isolates were susceptible for the majority of tested antimicrobials, including erythromycin and tetracycline, which are important antibiotics for the treatment of IC. The IC situation in Sonora State, Mexico, is complex because of the presence of serotypes A, B, and C. This finding emphasizes the importance of biosecurity in combination with the application of the most optimal vaccination programs in the control of IC in Sonora State, Mexico.

Genotypic divergence of Avibacterium paragallinarum isolates with different growth requirements for nicotinamide adenine dinucleotide

In 2017, for the first time in Asia, we reported the isolation of variants of Avibacterium paragallinarum with atypical NAD dependency. The present study was conducted to characterize the genotypes of 24 isolates of Av. paragallinarum in Korea, including the four variants reported previously. Most of the typical isolates (19/20) showed a unique ERIC-PCR pattern with no ERIC-PCR patterns in common between the typical isolates and the variants. Furthermore, the variants shared no ERIC-PCR patterns among themselves. All the typical NAD-dependent isolates belonged to the same phylogenetic group based on both 16S rRNA and hagA gene sequences. The four variants were placed in several groups distinct from the typical isolates. In the 16S rRNA phylogenetic analysis, two of the variants were not closely aligned to any other Av. paragallinarum, isolate although they were clearly members of the genus Avibacterium. The other variants were clustered together with NAD atypical isolates from geographically diverse global locations. Compared with the Modesto reference strain AY498870, all the variants lacked a TTTTT stretch at positions 182-186 in the 16S rRNA gene and the same deletion was shown in most of the reported variants. The typical isolates and variants shared 97.3-98.2% and 95.2-97.2% nucleotide sequence similarity, for 16S rRNA and hagA, respectively. In addition, the similarities among variants were within 98.3-100% and 96.5-98.4% for the two genes, respectively. Our results indicate that the Av. paragallinarum variants with altered NAD growth requirements were genetically different and highly divergent from the typical NAD-dependent isolates.RESEARCH HIGHLIGHTS NAD variant Korean Av. paragallinarum isolates show genetic diversity, whereas typical Korean Av. paragallinarum isolates do not.The Korean variants were not closely aligned to all other Av. paragallinarum in the 16S rRNA phylogeny.NAD atypical isolates from geographically diverse global locations clustered together.Almost all variants, including all Korean variants of Av. paragallinarum, lack a specific fragment of the 16S rRNA gene.

Identification and characterization of Dutch Avibacterium paragallinarum isolates and the implications for diagnostics

This study reports the results of diagnostic and molecular typing methods for 18 Avibacterium paragallinarum isolates obtained from outbreaks of infectious coryza in commercial layer flocks in the Netherlands. Isolation, biochemical identification, species-specific PCR tests and classical serotyping were performed. In addition, molecular typing by Enterobacterial Repetitive Intergenic Consensus-Based Polymerase Chain Reaction (ERIC-PCR) and sequence analysis of the partial HPG2 region of A. paragallinarum were applied and results of both techniques were compared. Moreover, the pathogenicity of an isolate of the most common genotype detected in the Netherlands was determined in an animal experiment. All 18 Avibacterium isolates were nicotinamide adenine dinucleotide-dependent. All isolates were detected by the species-specific conventional PCR while 33% of the isolates were missed by the species-specific real-time PCR. Sequence analysis showed a probe mismatch as a result of a single nucleotide polymorphism (G1516A). Modification of the probe of the real-time PCR was necessary to overcome false negative results. Molecular typing showed that sequence analysis of the partial HPG2 region was in concordance with ERIC-PCR results and indicated the presence of two major genotypes. Serotyping showed the presence of serovars A-1, A-2 and B-1. There was no correlation between genotyping results and serotyping results. Inoculation of an isolate of the most prevalent genotype, and belonging to serovar A-1, into brown layer hens demonstrated the pathogenicity of this isolate.

16S ribosomal RNA sequencing and molecular serotyping of Avibacterium paragallinarum isolated from Indian field conditions

AIM

This study was aimed at identifying Indian field isolates of Avibacterium paragallinarum on both molecular as well as serological levels that cause infectious coryza in chickens.

MATERIALS AND METHODS

Species-specific polymerase chain reaction (HPG-2 PCR), and 16S ribosomal RNA (rRNA) sequencing were employed for molecular identification. Whereas, multiplex PCR technique was used for serological identification of Indian field isolates of A. paragallinarum.

RESULTS

All three field isolates were identified as A. paragallinarum using HPG-2 PCR. The species-specific PCR results were validated using 16S rRNA sequencing. The partial 16S rRNA sequences obtained from all three isolates showed 96-99% homology with the NCBI database reference strains of A. paragallinarum. The aligned partial sequences of 16S rRNA were submitted to GenBank, and accession numbers were obtained. Multiplex PCR-based molecular serotyping showed that there are three serotypes of field isolates of A. paragallinarum, namely, strain IND101 is serovar A, strain IND102 is serovar B, and strain IND103 is serovar C.

CONCLUSION

HPG-2 PCR, 16S rRNA sequencing, and multiplex PCR are proved to be more accurate, sensitive, and reliable diagnostic tools for molecular and serological identification of A. paragallinarum field isolates. These diagnostic methods can substitute conventional cultural characterization and would be much valuable to formulate quick and correct prevention and control measures against this detrimental poultry pathogen.

The development and application of a blocking ELISA kit for the diagnosis of infectious coryza

A blocking enzyme-linked immunosorbent assay (B-ELISA) kit for the diagnosis of infectious coryza was developed in this study. The kit was based on a recently described blocking ELISA that uses monoclonal antibodies to achieve specificity for antibodies to either Haemophilus paragallinarum serovar A or serovar C. The results showed that the B-ELISA kit detected 96 and 90%, respectively, of chickens vaccinated or challenged with H. paragallinarum serovar A. When used on chickens vaccinated or challenged with H. paragallinarum serovar C, the kit detected 77 and 40%, respectively, as positive. The majority of sera from vaccinated chickens were still positive on the serovars A and C ELISAs 4 months after vaccination. Based on pen trial data, the serovar A B-ELISA kit had a sensitivity of 95% and a specificity of 100%. The serovar C B-ELISA kit had a sensitivity of 73% and a specificity of 100%. A range of field sera was examined with the kit, generating results that correlated with the known vaccination/disease history of the flocks examined. As freeze drying the monoclonal antibodies and the conjugate had some effect on optimal working concentration, the kit used liquid solutions of these two reagents. The kit could be stored for 7 days at 37 degrees C, 10 months at 4 degrees C and more than 1 yearat -20 degrees C. Our results suggest that the kit would be a useful aid in the diagnosis of infectious coryza in China and other countries where H. paragallinarum serovars A and C are the predominant or sole serovars.

Typing of Haemophilus paragallinarum Strains by Using Enterobacterial Repetitive Intergenic Consensus-Based Polymerase Chain Reaction

The enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) technique was used for fingerprinting of reference strains and Mexican isolates of Haemophilus paragallinarum. A total of nine ERIC patterns were given by the nine serovar reference strains of this bacteria. Two Modesto (C-2) reference strains from different sources showed the same ERIC pattern. Seventeen ERIC patterns were obtained among 29 Mexican isolates included in the study, belonging to serovars prevalent in Mexico (A-1, A-2, B-1, and C-2). Obtained results indicate that the ERIC-PCR technique could be used as a molecular laboratory tool for subtyping of H. paragallinarum.

Characterisation of isolates of Haemophilus paragallinarum from Indonesia

OBJECTIVE

To characterise 18 isolates of Haemophilus paragallinarum isolated from chickens in Indonesia.

PROCEDURE

The isolates were identified to species level by traditional phenotypic methods. Six of the isolates were also identified by a species-specific polymerase chain reaction. Fourteen of the isolates were examined for resistance to a panel of seven antimicrobial agents using a disc diffusion method. All 18 isolates were serotyped according to the Page scheme using reference antisera in a haemagglutination inhibition test.

RESULTS

Four of the 18 isolates were obtained from indigenous (kampung) chickens, with the remainder being from typical intensive poultry production systems. The 18 isolates were obtained from 11 outbreaks that showed the typical clinical signs of infectious coryza and 11 of the isolates were obtained from chickens that had been vaccinated with infectious coryza vaccines. All 18 isolates were confirmed as H paragallinarum by biochemical testing and six isolates were also identified as H paragallinarum by the polymerase chain reaction test. Eleven isolates were resistant to erythromycin and streptomycin, 10 to neomycin, eight to oxytetracycline, five isolates to doxycycline, three to sulphamethoxazoltrimethoprim but only one to ampicillin. Seven isolates were Page serovar A, four were Page serovar B and seven were Page serovar C.

CONCLUSION

The presence of all three Page serovars (A, B and C) has been confirmed for the first time in Indonesian chickens. As the majority of the infectious coryza vaccines in use in Indonesia contain only serovar A and C, the presence of serovar B in chickens indicates that the protection by these bivalent vaccines would be reduced. The use of trivalent infectious coryza vaccines that contain serovars A, B and C is recommended for use in Indonesia.

Production and evaluation of a panel of monoclonal antibodies against Haemophilus paragallinarum

We report on the production and characterisation of monoclonal antibodies (MAbs) against Haemophilus paragallinarum, the causative agent of infectious coryza. A bank of 8 MAbs were produced by traditional techniques - four against the reference strain for Page serovar A (0083) and four against the reference strain for Page serovar C (Modesto). Seven of the eight MAbs were shown to be IgG(1) with one being nontypable. None of the MAbs had HI activity and none gave any detectable reaction when examined by Western blotting. None of the MAbs gave a positive reaction in the indirect ELISA with any of the eight type strains of Pasteurella species or sub-species. None of our 8 MAbs gave serovar specific reactions when used in an indirect ELISA format. There was a trend for the serovar A MAbs to give a higher titre with serovar A isolates/strains and a similar trend for the serovar C MAbs to give higher titres with the serovar C isolates/strains.

Ribotype diversity of porcine Pasteurella multocida from Australia

OBJECTIVE

To use the technique of ribotyping to investigate the genetic diversity of Australian isolates of Pasteurella multocida associated with outbreaks of clinical disease in Australian pigs.

DESIGN

One hundred and seven porcine P multocida isolates were analysed by ribotyping using the restriction enzymes HpaII and HindIII. The genetic population structure of the Australian porcine P multocida isolates was determined through statistical analysis of the joint ribotype patterns, and this was then compared with biochemical and epidemiological data available for the population.

RESULTS

A total of 25 combined ribotypes were recognised, which were grouped into five ribotype clusters. Despite the deliberate selection of diverse isolates, the study revealed only a limited degree of genetic diversity. Fourteen of the ribotypes contained multiple isolates, and 12 of these ribotypes were present on more than one farm. Three of the seven biovars analysed in the study showed very limited diversity. All fifteen biovar 2 isolates (subsp multocida) were found in a single cluster (III), while all four biovar 8 isolates, which correspond to P multocida subsp gallicida, were allocated by themselves to a single cluster (IV). All nine of the biovar 12 isolates (lactose-positive subsp multocida) were assigned to a single cluster (I), together with the single biovar 14 isolate, which was the only other lactose-positive isolate in the population (ODC-negative).

CONCLUSION

A limited number of ribotypes of P multocida are associated with Australian pigs. The majority of these ribotypes are widely distributed across multiple farms, and across multiple states. Individual farms can possess multiple ribotypes of P multocida. Some of the unusual biochemical variants of P multocida present in Australian pigs have a very limited genetic diversity. The nature of pig production in Australia, primarily involving continuous flow systems with few closed herds, has possibly contributed to the widespread distribution of a limited number ribotypes.

The molecular epidemiology of four outbreaks of porcine pasteurellosis

Biochemical profiles, restriction endonuclease analysis (REA) and ribotyping were used to investigate a total of 38 Pasteurella multocida isolates from four separate outbreaks of pasteurellosis in Australian piggeries. Six isolates were obtained from Outbreak 1, 16 from Outbreak 2 and eight each from outbreaks 3 and 4. Outbreaks 1 and 2 were cases of pneumonic pasteurellosis while outbreaks 3 and 4 involved systemic pasteurellosis. Biochemical characterisation established that a number of different types of P. multocida were present in outbreaks 1 and 3 while outbreaks 2 and 4 were associated with a single type of P. multocida. Outbreaks 1 and 3 yielded isolates of P. multocida that belonged to the subspecies multocida and gallicida, with the subspecies multocida isolates being identified as biovar 3 (6 in total) or 12 (1 in total) and the subspecies gallicida isolates (7 in total) being identified as biovar 8. All 24 isolates from outbreaks 2 and 4 belonged to the subspecies multocida and were all biovar 3. REA and ribotyping showed that, in outbreaks 1 and 3, there were three different types of P. multocida in each outbreak with no common strains between the outbreaks. The molecular methods showed that only a single strain of P. multocida was associated with outbreaks 2 and 4, although the outbreaks were associated with strains that differed in REA profiles but shared a ribotype profile. This study has shown that both, systemic and pneumonic pasteurellosis can be associated with either a single strain or multiple strains of P. multocida. The results also indicate that the molecular typing methods of REA and ribotyping are superior to biochemical characterisation for epidemiological investigation of porcine pasteurellosis.