Detection of Gallibacterium spp. in chickens by fluorescent 16S rRNA in situ hybridization

First Report of Isolation of Gallibacterium anatis from Layer Chickens in Morocco with Decrease in Laying Performance

Gallibacterium is a genus of the family of Pasteurellaceae. It is well known as a commensal inhabitant of the respiratory and reproductive tract of healthy chickens. But in the last years, Gallibacterium anatis is increasingly reported in field cases with a decrease in laying performance due to infections of the reproductive tract. The aim of the present study was to investigate the implication of G. anatis infection in layer flocks facing a decrease in laying performance in Morocco. Birds were received from five different laying hen farms in two regions in Morocco showing a drop of egg production. Necropsy revealed 46.1 % (24/52) of sampled birds showed variable lesions in ovaries, salpinx, and trachea. In fact, 24 birds were affected by salpingitis, 18 by oophoritis, and 11 birds by atrophy of ovaries. Furthermore, tracheitis was observed in 24 birds. Bacteriological investigation was done from different organs, and G. anatis was found in ovaries (n = 20), trachea (n = 17), and cloaca (n = 3). Identification was based on growth morphology, Gram staining, and biochemical properties. Additionally, polymerase chain reaction test using specific primers for the genus identification was carried out. All isolates showed bands of 925 bp specific for G. anatis expressing the virulent toxin GtxA. Antibiotic resistance testing was performed and revealed that isolates were sensitive to enrofloxacin, florfenicol, and gentamycin but resistant to ampicillin, erythromycin, oxytetracycline, and sulfamethoxazole-trimethoprim. The present study is the first report of G. anatis in Morocco, demonstrating the need for further epidemiologic investigations as well as in regard to antibiotic resistance development.

Etiology, epidemiology, pathology, and advances in diagnosis, vaccine development, and treatment of Gallibacterium anatis infection in poultry: a review

Gallibacterium anatis is a Gram-negative bacterium of the Pasteurellaceae family that resides normally in the respiratory and reproductive tracts in poultry. It is a major cause of oophoritis, salpingitis, and peritonitis, decreases egg production and mortality in hens thereby severely affecting animal welfare and overall productivity by poultry industries across Europe, Asia, America, and Africa. In addition, it has the ability to infect wider host range including domesticated and free-ranging avian hosts as well as mammalian hosts such as cattle, pigs and human. Evaluating the common virulence factors including outer membrane vesicles, fimbriae, capsule, metalloproteases, biofilm formation, hemagglutinin, and determining novel factors such as the RTX–like toxin GtxA, elongation factor-Tu, and clustered regularly interspaced short palindromic repeats (CRISPR) has pathobiological, diagnostic, prophylactic, and therapeutic significance. Treating this bacterial pathogen with traditional antimicrobial drugs is discouraged owing to the emergence of widespread multidrug resistance, whereas the efficacy of preventing this disease by classical vaccines is limited due to its antigenic diversity. It will be necessary to acquire in-depth knowledge on important virulence factors, pathogenesis and, concerns of rising antibiotic resistance, improvised treatment regimes, and novel vaccine candidates to effectively tackle this pathogen. This review substantially describes the etio-epidemiological aspects of G. anatis infection in poultry, and updates the recent development in understanding the pathogenesis, organism evolution and therapeutic and prophylactic approaches to counter G. anatis infection for safeguarding the welfare and health of poultry.

Post mortem Survival of Gallibacterium anatis in a Laying Hen Experimental Infection Model

To assess the survival of Gallibacterium anatis in dead laying hens, 21-wk-old laying hens were injected intraperitoneally with 0.5 ml brain hearth infusion broth containing 10⁸ colony-forming units (CFU) of G. anatis 12656-12 liver ( n = 16), Escherichia coli ST141 ( n = 16), or a mix of G. anatis 12656-12 liver and E. coli ST141 ( n = 16), respectively. Birds were euthanatized 24 hr post injection. From each group eight dead birds were kept at 4 C and eight at room temperature. Swab samples were taken at different time points post euthanatization and streaked on blood agar plates. From the birds kept at 4 C, G. anatis was reisolated from the G. anatis and the G. anatis- E. coli co-injected groups at least 12 days post euthanization. From birds kept at room temperature, G. anatis was reisolated up to 2 days post euthanatization. When using the gyrB-based G. anatis-specific quantitative PCR (qPCR), G. anatis was detected within at least 5 days, and up to 5 days post euthanatization, from birds kept at room temperature and 4 C, respectively. Escherichia coli was reisolated from all the time points independent of how the birds were kept. No difference was observed between the reisolation rates for G. anatis or E. coli when comparing similar detection methods. For birds kept at 4 C, bacterial cultivation was a more sensitive method for detecting G. anatis ( P < 0.05), whereas for birds kept at room temperature, the G. anatis-specific qPCR outperformed bacterial culture ( P < 0.05). In conclusion, we demonstrated that G. anatis has a poorer survival rate than does E. coli in dead chickens kept at room temperature. That finding may affect the overall diagnostic sensitivity and lead to underdiagnosis of G. anatis in a normal production setting.

Presence of Avibacterium paragallinarum and Histopathologic Lesions Corresponds with Clinical Signs in a Co-infection Model with Gallibacterium anatis

Recently we demonstrated that co-infection with Avibacterium paragallinarum and Gallibacterium anatis leads to increased severity of clinical signs of infectious coryza in birds. The present study examined the interaction of these two pathogens in chickens by evaluation of histologic lesions in sinus infraorbitalis and nasal turbinates, applying a defined scoring scheme ranging from 0 to 3. Furthermore, for the first time, an in situ hybridization (ISH) technique was applied to detect A. paragallinarum in tissues. The samples were received from vaccinated and nonvaccinated birds that were infected with A. paragallinarum and/or G. anatis. Vaccinated birds were mostly devoid of any histopathologic lesions except a few birds with lesion score 1 at 7 and 14 days postinfection (dpi). Likewise, nonvaccinated birds infected with G. anatis only did not present microscopic changes in the sinus infraorbitalis, except in a single bird at 7 dpi. Interestingly, median lesion scores caused by G. anatis infection were significantly higher in the nasal turbinates of infected birds than in negative control at 7 and 14 dpi. The most prominent histologic changes were recorded from sinus infraorbitalis and nasal turbinates of nonvaccinated birds that were infected either with A. paragallinarum only or together with G. anatis. ISH demonstrated positive signals for A. paragallinarum in exudates present in the lumen or attached to the epithelial layer of investigated tissues. Such signals were mainly detected in tissues from birds with the highest histopathologic lesion scores.

Transmission and pathogenicity of Gallibacterium anatis and Escherichia coli in embryonated eggs

In laying hens, Escherichia coli (E. coli) and Gallibacterium anatis (G. anatis) are considered the two major pathogens causing reproductive tract disorders, either as single infections or as co-infections. Vertical transmission has been confirmed for E. coli but remains to be clearly demonstrated for G. anatis. The aim of the present study was to investigate the ability of both G. anatis and E. coli at eggshell transmission using an embryonated egg dipping model, and to investigate the possible interaction between the two organisms in an embryonated egg injection model. Embryonated eggs were dipped into brain heart infusion broth containing 10⁸ CFU/ml either of G. anatis 12656-12 liver, E. coli ST95 or E. coli ST141, respectively. E. coli ST95 and ST141 were re-isolated from the interior egg contents in 60% (12/20) and 85% (17/20) of the eggs, respectively, while G. anatis 12656-12 was only re-isolated from the interior egg contents in 6.7% (3/45) eggs. Eggs were injected with 10-1000 CFU of either G. anatis 12656-12, E. coli ST95 or ST141 into the allantoic cavity. As few as 10 CFU of G. anatis 12656-12 resulted in 100% mortality within 24 h post injection whereas the E. coli injected embryos all died at 48 h post injection. Significant difference in CFU counts were observed for G. anatis when compared G. anatis injection group with either of the two G. anatis - E. coli co-injection groups. Sixteen hours post injection, a significant difference in embryo mortality could be observed when comparing co-injected embryonated eggs (G. anatis and E. coli) and single-injected (G. anatis or E. coli) embryonated eggs. In conclusion, bacterial transmission via the eggshell was demonstrated for both G. anatis and E. coli although at different magnitudes. The embryonated egg injection model revealed that G. anatis in particular was highly pathogenic when exposed directly to the developing embryo.

Host-Specific and pH-Dependent Microbiomes of Copepods in an Extensive Rearing System

Copepods are to an increasing extent cultivated as feed for mariculture fish larvae with variable production success. In the temperate climate zone, this production faces seasonal limitation due to changing abiotic factors, in particular temperature and light. Furthermore, the production of copepods may be influenced by biotic factors of the culture systems, such as competing microorganisms, harmful algae, or other eukaryotes and prokaryotes that may be non-beneficial for the copepods. In this study, the composition of bacteria associated with copepods was investigated in an extensive outdoor copepod production system. Light microscopy and scanning electron microscopy revealed that bacteria were primarily found attached to the exoskeleton of copepods although a few bacteria were also found in the gut as well as internally in skeletal muscle tissue. Through 16S rRNA gene-targeted denaturing gradient gel electrophoresis (DGGE) analysis, a clear difference was found between the microbiomes of the two copepod species, Acartia tonsa and Centropages hamatus, present in the system. This pattern was corroborated through 454/FLX-based 16S rRNA gene amplicon sequencing of copepod microbiomes, which furthermore showed that the abiotic parameters pH and oxygen concentration in rearing tank water were the key factors influencing composition of copepod microbiomes.

FISH methods in cytogenetic studies

This chapter describes the various methods derived from the protocol of standard fluorescent in situ hybridization (FISH) that are used in human, animal, plant, and microbial studies. These powerful techniques allow us to detect and physically map on interphase nuclei, chromatin fibers, or metaphase chromosomes probes derived from single-copy genes to repetitive DNA sequences. Other variants of the technique enable the co-localization of genes and the overall comparison of the genome among individuals of the same species or of different taxa. A further variant detects and localizes bacteria on tissues and cells. Overall, this offers a remarkable multiplicity of possible applications ranging from strict physical mapping, to clinical and evolutionary studies, making it a powerful and informative complement to other molecular, functional, or genomic approaches.

Draft Genome Sequence of Gallibacterium anatis bv. haemolytica 12656-12 Liver, an Isolate Obtained from the Liver of a Septicemic Chicken

We report the draft genome sequence of Gallibacterium anatis bv. haemolytica strain 12656-12 Liver. This strain was isolated from the liver of a septicemic layer chicken in Denmark in 1981. The strain has been used extensively for experimental purposes.

Assessing pathogenicity of Gallibacterium anatis in a natural infection model: the respiratory and reproductive tracts of chickens are targets for bacterial colonization

Two separate bird trials were performed to establish a reliable route of infection for Gallibacterium anatis in chickens, comparing intranasal (i.n.) and intravenous (i.v.) applications. Additionally, three mutually divergent isolates from three geographical locations, as shown by MALDI-TOF-MS and partial rpoB gene sequence analysis, were compared. In the first trial, birds were infected with one of the selected isolates by the i.v. or i.n. route. Subsequently, birds were killed 3, 12 and 24 h post infection following i.v. infection while at 3, 7 and 10 days post infection (dpi) in the case of i.n. infection along with birds of the control group. As a result, i.n. infection showed prominent and consistent bacterial tissue distribution in different organs persisting until 10 dpi, which was a striking contrast to the i.v. infection route. Likewise, histopathology revealed mild to severe tracheal lesions following i.n. infection. The second trial was set up to confirm both the achieved results and the robustness of i.n. infection but with an extended observation period, until 28 dpi In agreement with the preceding trial, identical results for bacteriological and histopathological examinations were obtained with persistency of bacteria until 28 dpi Comparing the three different isolates from Mexico, China and Austria, the Mexican isolate showed a somewhat higher pathogenicity than the other strains. Consequently, pathogenesis of G. anatis strains was studied in chickens elucidating i.n. infection as the most reliable route characterized by a long-lasting bacteraemia, targeting the respiratory and reproductive tract.

Identification and characterization of potential performance-related gut microbiotas in broiler chickens across various feeding trials

Three broiler feeding trials were investigated in order to identify gut bacteria consistently linked with improvements in bird performance as measured by feed efficiency. Trials were done in various geographic locations and varied in diet composition, broiler breed, and bird age. Gut microbial communities were investigated using microbial profiling. Eight common performance-linked operational taxonomic units (OTUs) were identified within both the ilea (180, 492, and 564-566) and ceca (140-142, 218-220, 284-286, 312, and 482) across trials. OTU 564-566 was associated with lower performance, while OTUs 140-142, 482, and 492 were associated with improved performance. Targeted cloning and sequencing of these eight OTUs revealed that they represented 26 bacterial species or phylotypes which clustered phylogenetically into seven groups related to Lactobacillus spp., Ruminococcaceae, Clostridiales, Gammaproteobacteria, Bacteroidales, Clostridiales/Lachnospiraceae, and unclassified bacteria/clostridia. Where bacteria were identifiable to the phylum level, they belonged predominantly to the Firmicutes, with Bacteroidetes and Proteobacteria also identified. Some of the potential performance-related phylotypes showed high sequence identity with classified bacteria (Lactobacillus salivarius, Lactobacillus aviarius, Lactobacillus crispatus, Faecalibacterium prausnitzii, Escherichia coli, Gallibacterium anatis, Clostridium lactatifermentans, Ruminococcus torques, Bacteroides vulgatus, and Alistipes finegoldii). The 16S rRNA gene sequence information generated will allow quantitative assays to be developed which will enable elucidations of which of these phylotypes are truly performance related. This information could be used to monitor strategies to improve feed efficiency and feed formulation for optimal gut health.

Antimicrobial susceptibility and tetracycline resistance determinant genotyping of Gallibacterium anatis

The present investigation was undertaken to assess the antimicrobial susceptibility of a collection of 58 Gallibacterium isolates. All strains were tested by the broth dilution method using the veterinary fastidious medium. A total of 46 field strains were tested, whereof 23 were clinical isolates from 10 Mexican layer flocks and another 23 isolates originated from 13 clinically healthy poultry flocks in Denmark. In addition, 12 Gallibacterium reference strains that had been isolated some 30-40 years ago were included. The 58 strains were tested against 23 compounds of different classes. Multidrug resistance (resistance towards≥three drugs) was observed for 65% of the field strains and only two strains were susceptible to all compounds. Most prominently, resistance to tetracycline and sulfamethoxazole was observed in 92% and 97% of the field strains, respectively. For comparison these figures were 67% and 42%, respectively, for the reference strains. Genotyping of tetracycline resistance determinants was performed with primers specific for tet(A-E, H, K-M, O). Strains positive for tet(B), tet(H) and tet(L) were identified, however, in 20 out of 49 tetracycline resistant strains no determinant was identified. This is the first study to determine the antimicrobial susceptibility of Gallibacterium anatis by MIC revealing that multidrug resistance is very common among G. anatis field isolates. tet(B) was by far the most common determinant identified but future work should aim at identifying the tetracycline resistance determinants in the remaining 41% of strains where no determinant was assigned.

In vivo studies of Gallibacterium anatis infection in chickens

The aim of the present study was to investigate the pathology in normal or immunosuppressed chickens followed intravenous or intraperitoneal inoculation with a well-characterized strain of Gallibacterium anatis. Two groups of 30 15-week-old commercial brown laying chickens were used, having been screened and found negative for Gallibacterium organisms. One group was treated with 5-fluorouracil to promote heterophil depletion, while the other was saline treated. Ten days later 15 chickens from each group were inoculated either intravenously or intraperitoneally with 3.3 x 10(7) colony-forming units of G. anatis strain 12656-12. Subsets of chickens were sacrificed at 3, 12 or 24 h post-infection and examined for lesions. Livers and spleens were examined by culture and by fluorescent in situ hybridization. Intravenously infected birds showed severe septicaemic lesions in both the normal and immunosuppressed birds. Mortality was recorded only in the latter, with an overall rate of 73%. The intraperitoneally infected chickens of normal immune status showed various degrees of localized purulent peritonitis at the inoculation site, but in the immunosuppressed birds the entire peritoneum tended to be involved along with the abdominal organs. This was similar to previous descriptions of natural infections and may represent a useful infection model for detailed analysis of Gallibacterium virulence factors and pathogenesis.