Antimicrobial sensitivity of Avibacterium paragallinarum isolates from layers in the special region of Yogyakarta, Indonesia

Molecular detection and pyrG sequence analysis of Avibacterium paragallinarum using clinical samples of infraorbital exudates from layer chickens with infectious coryza symptoms in Indonesia

Background and Aim

Infectious coryza (IC) or snot, is caused by Avibacterium paragallinarum and leads to upper respiratory disease in poultry. Various diagnostic methods are available, including isolation and identification through bacterial culture and biochemical tests. However, the isolation and subsequent identification of A. paragallinarum are challenging because the bacteria are fastidious and require specific growth factors. This study aimed to detect A. paragallinarum in clinical samples taken from the exudate of the infraorbital sinus of layer hens showing clinical signs of IC.

Materials and Methods

Samples were collected from 10 layer hens with IC symptoms. Following DNA extraction, HPG-2 polymerase chain reaction (PCR) assays were performed. The PCR amplicons underwent electrophoresis to determine those of the correct target size (511 bp), and these were sequenced. The resultant sequences were analyzed using the National Center for Biotechnology Information (NCBI) basic local alignment search tool. MEGA X was used for bioinformatics analysis.

Results

The presence of A. paragallinarum was confirmed by HPG-2 PCR in 4/10 samples. Bioinformatics analysis showed that the amino acid sequence of the samples and the A. paragallinarum reference sequences in the NCBI database were grouped within the same cluster. Furthermore, the nucleotide sequences showed 98.64%-100% of similarity with the reference sequences. The phylogenetic reconstruction of partial pyrG sequences from 55 A. paragallinarum strains/isolates deposited in GenBank confirmed that the four HPG-2 PCR-positive samples fell within the A. paragallinarum cluster, separate from the Pasteurella multocida, Avibacterium spp., and Rodentibacter pneumotropicus clusters.

Conclusion

Avibacterium paragallinarum infection was molecularly confirmed in 4/10 (40%) samples by HPG-2 PCR amplicon detection. Clustering of the pyrG partial gene sequences revealed that the positive samples fell within the A. paragallinarum cluster.

Commensal bacteria contribute to the growth of multidrug-resistant Avibacterium paragallinarum in chickens

Avibacterium paragallinarum-associated infectious coryza (IC) is an important threat in commercial poultry. Previous studies about the characteristics of A. paragallinarum are succeeded in revealing the course of IC disease, but whether and how resident microbes contribute to the infection remains unclear. To understand the role of commensal bacteria, we isolated 467 commensal bacteria, including 38 A. paragallinarum, from the respiratory tract of IC chicken. The predominant commensal isolates were Gram-positive bacteria belonging to Staphylococcus spp. [33.19%, 95% confidence interval (CI): 28.93-37.66%], Enterococcus spp. (16.49%, 95% CI: 13.23-20.17%), and Bacillus spp. (16.27%, 95% CI: 13.04-19.94%). These isolates were closely correlated with the survival of A. paragallinarum. We examined and found that commensal bacteria aggravate A. paragallinarum-associated infections because certain commensal species (28.57%, 95% CI: 15.72-44.58%) induced hemolysis and promoted the growth of A. paragallinarum in vitro. Notably, A. paragallinarum showed high resistance to routine antibiotics such as erythromycin (84.21%, 95% CI: 68.75-93.98%), tetracycline (73.68%, 95% CI: 56.90-86.60%) and carried diverse mobile resistance gene clusters. Overall, we found commensal bacteria especially Gram-positive bacteria facilitate the survival of multidrug-resistant A. paragallinarum to exacerbate infections, suggesting that novel strategies may diminish A. paragallinarum-associated infections by modulating the population dynamics of commensal bacteria.

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.