Isolation and identification of NAD‐independent bacteria from chickens with symptoms of infectious coryza

Novel NAD-independent Avibacterium paragallinarum: Isolation, characterization and molecular identification in Iran

BACKGROUND

Infectious coryza (IC) is an invasive upper respiratory disease caused by Avibacterium paragallinarum that affects birds, particularly chickens. The objective of this study is to isolate, characterize and molecularly identify the bacterium A. paragallinarum in poultry birds, as well as to determine its antibiotic sensitivity and resistance.

METHODS

A total of 10 chickens from four different Iranian farms with typical IC symptoms were used in this study. The nasal swabs were streaked onto chocolate agar plates and blood agar plates and incubated at 37°C in 5% CO2 for 24 to 48 h. As part of the identification of bacteria, bacteriological observations and polymerase chain reaction (PCR) testing are conducted. The antibiotic sensitivity tests were also performed using the disk diffusion method against A. paragallinarum and the prevalence in different farms was determined.

RESULTS

By using biochemical assays and PCR analyses, seven strains of A. paragallinarum were isolated from samples of four chicken farms with typical IC clinical signs. Most isolates (4/7) showed the typical requirement for nicotinamide adenine dinucleotide (NAD) and an enriched CO2 atmosphere for growth. Three of the seven strains of A. paragallinarum were found to be novel NAD-independent under anaerobic conditions. There was one biochemical biovar identified in terms of carbohydrate fermentation patterns, although changes in maltose carbohydrate fermentation patterns were detected in the No. 5 strain. All isolates were sensitive to gentamicin and spectinomycin. Three novel NAD-independent strains (Nos.1, 5 and 7) were found to be multidrug-resistant (MDR) and resistant to at least three classes of antibiotics. There was greater antibiotic resistance in the three NAD-independent isolates than in normal NAD-dependent bacteria.

CONCLUSION

By discovering NAD-independent forms of A. paragallinarum, these species have a greater range than previously believed. A clear, cautious approach should be taken in diagnosing and possibly controlling IC.

An updated comprehensive review on ornithobacteriosis: A worldwide emerging avian respiratory disease

Ornithobacteriosis is an important emerging respiratory disease of domestic and wild birds caused by Ornithobacterium rhinotracheale (ORT) bacterium. The disease has been detected in some countries since 1980, which rapidly spread worldwide later on. Ornithobacteriosis can transmit either horizontally or even vertically. Infection with ORT is mainly characterized by respiratory distress, poor performance, acute death, and a drop in egg production. However, the most characteristic necropsy lesions of dead turkeys and chickens are yoghurt like airsacculitis and pneumonia, usually unilateral. Unfortunately, infection with ORT was misdiagnosed in most of the poultry flocks due to similarity with other respiratory pathogens and the lack of the ideal protocols for diagnosis. Recently, some molecular and serological techniques have been used to detect the infection. Treatment of ORT with antibiotics is very difficult and variable as a result of acquired resistance. Many vaccines have been developed to counteract such infection in broiler, layers, and breeder chicken and turkey flocks. Inactivated, live, and sub-unit vaccines have been used with satisfactory results. Thus, this review paper aimed to address ornithobacteriosis, emphasizing the distribution, transmission, clinical picture, diagnosis, and disease control.

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.

Isolation and characterization of Avibacterium paragallinarum with different nicotinamide adenine dinucleotide requirements

Twenty field isolates of Avibacterium paragallinarum were obtained from chickens in South Korea during 2011-2015. The isolates were identified by a HPG-2 PCR assay specific for A. paragallinarum and by biochemical tests. Growth requirements, Page serovars, carbohydrate fermentation patterns, and antimicrobial susceptibility were also examined. Most isolates (16/20) showed the typical requirement for nicotinamide adenine dinucleotide (NAD) and an enriched CO₂ atmosphere for growth. One isolate needed increased levels of NAD and serum for good growth. Three isolates showed NAD-independent growth on blood agar under aerobic conditions. In terms of carbohydrate fermentation patterns, three biochemical biovars were recognized; these varied with respect to acid production from maltose and D-xylose. The 16 typical NAD-dependent isolates were serovar A while the variants, both NAD-independent isolates and the isolate with increased NAD dependency were non-typeable. All isolates were sensitive to amoxicillin-clavulanic acid, ceftiofur, gentamicin, and spectinomycin. High rates of resistance, including intermediate resistance, to lincomycin (100%), cloxacillin (75%), and erythromycin (70%) were observed. The four variant strains (the three NAD-independent isolates and the isolate showing unusual growth requirements) were more resistant to antibiotics than the typical NAD-dependent strains. The finding of NAD-independent forms of A. paragallinarum extends the known distribution of this form, previously only reported in South Africa, Mexico and Peru. There is clearly a need for increased caution in the diagnosis and, possibly, the control of infectious coryza.

Naturally Occurring β-Nicotinamide Adenine Dinucleotide-Independent Avibacterium paragallinarum Isolate in Peru

The β-nicotinamide adenine dinucleotide (NAD) requirement has been considered to be essential for the isolation of the causal agent of infectious coryza, Avibacterium paragallinarum. Nevertheless, NAD-independent reports from South Africa and Mexico dismissed this paradigm. It is now accepted that both NAD-dependent and NAD-independent agents are able to cause infectious coryza and thus belong to the species A. paragallinarum. Here, we report for the first time in Peru a NAD-independent isolate from broiler chickens with typical signs of infectious coryza that have received a trivalent inactivated vaccine against infectious coryza. The isolate was identified based on its morphology, biochemical and serologic tests, and PCR results. Partial 16S rRNA gene sequence analysis confirmed the isolate as A. paragallinarum. There have been no cases of NAD-independent A. paragallinarum isolates reported in South America. Increasing reports around the world highlight not only the need to reconsider the in vitro nutritional requirements of this species for its correct isolation but also the cross-protection conferred by commercial infectious coryza vaccines against NAD-independent isolates.

Detection of Avibacterium paragallinarum by Polymerase chain reaction from outbreaks of Infectious coryza of poultry in Andhra Pradesh

Aim:

This study was carried out for the detection of Avibacterium paragallinarum from outbreaks of infectious coryza of poultry

Materials and Methods:

The polymerase chain reaction (PCR) was standardized for the diagnosis of infectious coryza by using infectious coryza Killed vaccine, ventri biologicals, Pune as source of DNA of A. paragallinarum. Five outbreaks of infectious coryza from Andhra Pradesh were investigated in the present study. A total of 56 infra orbital sinus swabs and 22 nasal swabs were tested by PCR.

Results:

PCR analysis showed 56 positives (71.7%) for infectious coryza out of total 78 samples tested. Of 56 infra orbital sinus swabs tested, 47 were positive (83.9%) and 9 nasal swabs (40.9%) out of 22 tested had given positive results for infectious coryza. Samples collected from birds at acute stage of disease and samples collected before treatment with antibiotics were given better results on PCR.

Conclusion:

For preventing the economic losses associated with the disease, an early, accurate and rapid diagnosis is essential. PCR is a rapid and highly sensitive diagnostic technique which can substitute conventional cultural examination.

Further studies on the use of a polymerase chain reaction test for the diagnosis of infectious coryza

Further information is reported on the use of a polymerase chain reaction (PCR) test for the diagnosis of infectious coryza in China. The majority of sinus swabs taken from artificially infected chickens and stored in glycerol-enriched phosphate-buffered saline were still positive by PCR after storage for 180 days at either 4 degrees C or - 20 degrees C. Storage of swabs in either saline or nutrient broth was not as effective. Traditional culture failed to detect H. paragallinarum after storage for 3 days, regardless of storage medium or storage temperature. With dry swabs, the PCR could detect H. paragallinarum after storage for 7 days or longer at either 4 degrees C or - 20 degrees C, while traditional culture could not. In PCR tests on 64 artificially-challenged chickens, all were positive by PCR at the six sampling dates up to 18 days post-challenge. Traditional culture gave a similar result. Both PCR and culture detected 50% or less of chickens as positive at 21 and 24 days post challenge. Antibiotic treatment reduced the ability of both culture and the PCR test to detect H. paragallinarum. The value of the PCR test and its superiority over traditional culture for the diagnosis of infectious coryza has been confirmed in these experiments.

The presence of nicotinamide adenine dinucleotide-independent Haemophilus paragallinarum in México

Two isolates of Haemophilus paragallinarum were obtained from a layer chicken in Mexico. The isolates were confirmed as H. paragallinarum by polymerase chain reaction and conventional biochemical identification. The isolates were nicotinamide adenine dinucleotide (NAD) independent-growing on blood agar without the need of a nurse colony as well as on a complex medium that lacked both NAD and chicken serum. Both isolates were pathogenic, causing the typical clinical signs of infectious coryza in susceptible chickens. One isolate was Page serovar B/Kume serovar B-1 and the other isolate was Page serovar C/Kume serovar C-2. The isolates were associated with a field outbreak that involved an egg drop of 20% over a 3-wk period and a doubling of weekly mortality (from 0.1% to 0.2%). This is the first report of NAD-independent H. paragallinarum outside South Africa and is the first time that NAD-independent H. paragallinarum of serovar B has been reported.

Development of a 23S rRNA-based PCR assay for the identification of Pasteurella multocida

AIMS

The aim of this work was to develop a rapid diagnostic test for Pasteurella multocida.

METHODS AND RESULTS

A polymerase chain reaction (PCR) assay using primers derived from the 23S rRNA gene sequence of Past. multocida was developed. The PCR assay correctly identified all 144 isolates of Past. multocida tested, including type strains of the three subspecies as well as the reference strains for the Heddleston and Carter typing schemes. Of 20 closely related bacteria from the family Pasteurellaceae tested, only the type strains of Past. canis biovar 2 and Past. avium biovar 2 were positive. These two bacteria, formerly known as Bisgaard Taxon 13, are the closest phylogenetic relatives of Past. multocida based on 16S ribosomal rRNA. All phylogenetically unrelated avian and porcine organisms tested were negative.

CONCLUSION

This PCR enables rapid identification of Past. multocida colonies from avian or porcine origin.

SIGNIFICANCE AND IMPACT OF THE STUDY

Veterinary diagnostic laboratories can use this PCR to rapidly and accurately diagnose fowl cholera and porcine pasteurellosis.

Infectious coryza: overview of the disease and new diagnostic options

Infectious coryza is a well-recognized and commonly encountered upper respiratory tract disease of chickens that is caused by the bacterium Haemophilus paragallinarum. The occurrence of recent outbreaks in North America has emphasized that the disease can be significant in meat chickens as well as layer chickens. In developing countries, coryza is commonly complicated by the presence of a range of other infections, resulting in severe disease and significant economic losses. Unusual forms of the disease, involving arthritis and septicemia, again associated with the presence of other pathogens, have been found in South America. Newly recognized bacteria such as Ornithobacterium rhinotracheale and phenotypic variant forms of both H. paragallinarum and close relatives (variant in that they no longer require V-factor for growth in vitro) have increased the difficulty associated with diagnosing the disease. There have been suggestions in both South America and South Africa that new serovars or serovar variants, associated with unusual clinical manifestations and causing vaccine failures, are emerging. Definitive evidence to confirm or deny the role of these "variants" in vaccine failures is currently not available. A new DNA-based diagnostic technique, involving PCR, has been recently described and will greatly assist in the diagnosis of infectious coryza.