Isolation, identification, antibiotic resistance profile and molecular analysis of Ornithobacterium rhinotracheal isolates from turkeys.

BACKGROUND: Ornithobacterium rhinotracheal (ORT) infects numerous birds, particularly chickens and turkeys. ORT is an emerging bacterial pathogen of global concern in the poultry industry. As ORT is rapidly spreading throughout commercial poultry, it requires intensive studies of its epidemiology, diagnostic procedures, molecular typing, virulence genes and antimicrobial resistance. OBJECTIVES: The present study was conducted in isolation and identification of ORT from slaughtered turkeys. METHODS: Cleft palate swabs of 200 were collected from slaughtered turkeys and cultured on blood agar. ORT was characterized using biochemical tests and PCR targeting the ORT 16S rRNA gene. Virulence genes of isolates were determined targeting adenylate kinase (adk), copA and virulence-associated protein D (vapD) genes. Additionally, diversity of ORT isolates was performed by enterobacterial repetitive intergenic consensus (ERIC) and RAPD PCR. Disk diffusion was used to determine the antibiotic sensitivity of the isolates. RESULTS: ORT was identified in 23 (11.5%) samples using both the biochemical tests and PCR. The result of detecting virulence genes showed that all the isolates (23: 100%) had the adk gene, whereas two (8.7%) isolates had the copA gene, and seven (30.43%) isolates had the vapD gene. Molecular typing of isolates revealed 21 different patterns by RAPD PCR assay using M13 primer and 20 distinct patterns by ERIC PCR test. Both ERIC and RAPD PCR were distinctive methods for investigating the genetic diversity of ORT isolates. The antibiotic resistance test showed that 18 (78.26%) isolates were resistant to gentamicin, amikacin, cefazolin, streptomycin and penicillin. All isolates (100%) were resistant to cloxacillin and fosfomycin. CONCLUSIONS: This study showed the prevalence of ORT in turkey and high resistance of this bacterium to many common veterinary antibiotics. Moreover, both ERIC and RAPD PCR are distinctive methods for investigating the genetic diversity of ORT isolates. These data may help monitor antibiotic resistance and typing of ORT in epidemiological studies and serve as the foundation for designing region-specific vaccines for future use.

Case reports involving coinfection with Avibacterium paragallinarum and Ornithobacterium rhinotracheale in broiler chickens and Avibacterium endocarditis in broiler breeding hens in Poland.

ABSTRACTThe study describes three clinical cases of infection with Avibacterium spp.. In case no. 1, respiratory clinical signs and high mortality (0.7-4.2% daily; total 21.2%) in Ross 308 broiler chickens were shown to be caused by coinfection with sequence type 9 of O. rhinotracheale presumptive serotype A and A. paragallinarum presumptive serotype B. The identical (pulsed-field gel electrophoresis) restriction pattern (pulsotype) of seven A. paragallinarum isolates indicated that infectious coryza in broilers was caused by the same clone. In cases 2 and 3, sudden increased deaths in Ross 308 broiler breeders (especially males) with lesions in the endocardium (valvular or mural endocarditis) were shown to be caused by A. endocarditis. Among nine antibiotics tested, florfenicol was the only antibiotic to which all A. paragallinarum and O. rhinotracheale isolates were susceptible. Out of the eight antibiotics tested, 11 A. endocarditis isolates from both clinical cases of infective endocarditis were susceptible to penicillin, amoxicillin, doxycycline and florfenicol. The A. endocarditis isolates tested in both clinical cases had different PFGE patterns (pulsotypes), but identical within a case. The causes of infectious coryza and infective endocarditis in the cases presented have not been determined. In the prevention of infectious diseases in large-scale livestock farming, it is very important to follow the rules of biosecurity.

Genetic Diversity of Ornithobacterium rhinotracheale Isolated from Chickens and Turkeys in the United States.

Ornithobacterium rhinotracheale (ORT) is an important bacterial pathogen of great economic significance to poultry production. This bacterium causes severe disease in chickens and turkeys worldwide. The objective of this study was to characterize ORT isolates from two different geographic locations in the United States by multilocus sequence typing (MLST). A total of 60 isolates were included in this study; 36 from California and 24 from Minnesota. All 60 isolates were confirmed to be ORT by PCR that targeted the 16S rRNA gene. The results of MLST revealed eight different sequence types (ST) of ORT. Out of these, four were novel and were assigned numbers ST-32, ST-33, ST-34, and ST-35. ST-1 was the predominant sequence type among all isolates followed by ST-9 and ST-8. Only one isolate was identified as ST-2. No significant variation was seen in STs in ORT isolated from different years. In turkeys, 76.3% (29/38) of isolates belonged to ST-1 and 7.9% (3/38) to ST-8. Of the chicken isolates, 72.2% (13/18) belonged to ST-1 and 16.6% (3/18) to ST-9. Isolates from both states showed low genetic variability. Of the 32 isolates from California, 24 (75%) were identified as ST-1 and 4 (12.5%) were identified as ST-9. The most prevalent sequence type was ST-1 (17/24) followed by ST-8 (3/24) in Minnesota. Three isolates from turkeys in Minnesota belonged to the same ST (ST-8) as the already known ORT strain RefO, which isolated from a rook in Germany in 2000. Whether this sequence type had evolved from wild birds could not be ascertained in this study.

Genomic Landscape of Ornithobacterium rhinotracheale in Commercial Turkey Production in the United States.

Ornithobacterium rhinotracheale is a causative agent of respiratory tract infections in avian hosts worldwide but is a particular problem for commercial turkey production. Little is known about the ecologic and evolutionary dynamics of O. rhinotracheale, which makes prevention and control of this pathogen a challenge. The purpose of this study was to gain insight into the genetic relationships between O. rhinotracheale populations through comparative genomics of clinical isolates from different U.S. turkey producers. O. rhinotracheale clinical isolates were collected from four major U.S. turkey producers and several independent turkey growers from the upper Midwest and Southeast, and whole-genome sequencing was performed. Genomes were compared phylogenetically using single nucleotide polymorphism (SNP)-based analysis, and then assembly and annotations were performed to identify genes encoding putative virulence factors and antimicrobial resistance determinants. A pangenome approach was also used to establish a core set of genes consistently present in O. rhinotracheale and to highlight differences in gene content between phylogenetic clades. A total of 1,457 nonrecombinant SNPs were identified from 157 O. rhinotracheale genomes, and four distinct phylogenetic clades were identified. Isolates clustered by company on the phylogenetic tree, however, and each company had isolates in multiple clades with similar collection dates, indicating that there are multiple O. rhinotracheale strains circulating within each of the companies examined. Additionally, several antimicrobial resistance proteins, putative virulence factors, and the pOR1 plasmid were associated with particular clades and multilocus sequence types, which may explain why the same strains seem to have persisted in the same turkey operations for decades.IMPORTANCE The whole-genome approach enhances our understanding of evolutionary relationships between clinical Ornithobacterium rhinotracheale isolates from different commercial turkey producers and allows for identification of genes associated with virulence, antimicrobial resistance, or mobile genetic elements that are often excluded using traditional typing methods. Additionally, differentiating O. rhinotracheale isolates at the whole-genome level may provide insight into selection of the most appropriate autogenous vaccine strain, or groups of strains, for a given population of clinical isolates.

Whatman® FTA® Cards Performance for Ornithobacterium rhinotracheale DNA Amplification.

The avian pathogen Ornithobacterium rhinotracheale (ORT) has been implied in the etiology of poultry respiratory disease in recent years. To evaluate whether Whatman® Flinders Technology Associates (FTA®) cards can be used for hazard-free transport and storage of ORT samples for posterior DNA amplification, a controlled assay was performed. Three 10-fold dilutions of an ORT culture suspension were spotted on FTA cards and stored at room temperature (RT) for 6 mo. Sterile swabs were immersed in the same three 10-fold culture dilutions and stored at RT and 4 and -20 C without storage medium for the same time. DNA was extracted from both the FTA cards and swabs 1 day, 1 and 6 wk, and 6 mo following sample preparation and stored at -20 C. At the end of the experiment, real-time PCR amplification of the 16S ribosomal RNA gene was performed from DNA extracted throughout a 6-mo period from all ORT samples stored on both FTA cards and swabs. The obtained threshold cycle values for each ORT DNA extraction date were within the same range for all samples in a dilution-dependent fashion, regardless of storage temperature or used material. Pure ORT colonies could be reisolated 1 day after sample preparation from the swab dilutions stored at all temperatures but not from the FTA cards. We conclude that the efficiency of ORT DNA amplification from samples stored on FTA cards or in swabs is similar. However, FTA cards have the advantage of preventing microorganism growth, thus allowing safe transport and storage, for at least 6 mo, for bacterial dilutions down to at least 104-105 colony-forming units/ml.

Method for culturing Candidatus Ornithobacterium hominis.

Candidatus Ornithobacterium hominis has been detected in nasopharyngeal microbiota sequence data from around the world. This report provides the first description of culture conditions for isolating this bacterium. The availability of an easily reproducible culture method is expected to facilitate deeper understanding of the clinical significance of this species.

'Candidatus Ornithobacterium hominis': insights gained from draft genomes obtained from nasopharyngeal swabs.

'Candidatus Ornithobacterium hominis' represents a new member of the Flavobacteriaceae detected in 16S rRNA gene surveys of people from South-East Asia, Africa and Australia. It frequently colonizes the infant nasopharynx at high proportional abundance, and we demonstrate its presence in 42 % of nasopharyngeal swabs from 12-month-old children in the Maela refugee camp in Thailand. The species, a Gram-negative bacillus, has not yet been cultured, but the cells can be identified in mixed samples by fluorescent hybridization. Here, we report seven genomes assembled from metagenomic data, two to improved draft standard. The genomes are approximately 1.9 Mb, sharing 62 % average amino acid identity with the only other member of the genus, the bird pathogen Ornithobacterium rhinotracheale. The draft genomes encode multiple antibiotic-resistance genes, competition factors, Flavobacterium johnsoniae-like gliding motility genes and a homologue of the Pasteurella multocida mitogenic toxin. Intra- and inter-host genome comparison suggests that colonization with this bacterium is both persistent and strain exclusive.

Characterization of Ornithobacterium rhinotracheale field isolates from Hungary.

Ornithobacterium rhinotracheale is a widely distributed rod-shaped Gram-negative bacterium that infects several avian species including chickens and turkeys. It is associated with respiratory signs, growth retardation, mortality, and reduced egg production, thus causing severe economic losses to the poultry industries. In this study, 37 field isolates of O. rhinotracheale, collected from various locations in Hungary between 1997 and 2015, were identified and characterized by the analysis of partial 16S rRNA gene sequences, enterobacterial repetitive intergenic consensus (ERIC)-PCR, and random amplified polymorphic DNA (RAPD) PCR assays with the OPG11, OPH19, and M13 primers. Most of the field isolates were serotype A, one was serotype B, and four were serotype D. One isolate could not be typed with antisera against serotypes A-E. In a phylogenetic analysis of the 16S rRNA sequences, the isolates formed two clusters. Thirteen distinct patterns were identified with ERIC-PCR, and the RAPD assay with the M13 primer assigned the isolates to 10 different patterns. The other two RAPD assays were unsuitable for distinguishing and grouping the isolates. Neither ERIC type nor RAPD pattern correlated with the place or year of isolation. However, the strains isolated from chickens were more heterogeneous on ERIC-PCR than the isolates recovered from turkeys. In this study, ERIC-PCR was the most discriminatory method for investigating the genetic diversity of O. rhinotracheale isolates.

The First Detection of Ornithobacterium rhinotracheale in New Zealand.

Ornithobacterium rhinotracheale (ORT) has been considered exotic to New Zealand and thus, any samples from poultry suspected of ORT infection are submitted as part of an exotic disease investigation managed by Ministry for Primary Industries (MPI) and subjected to standardized test protocols carried out in the physical containment level 3+ laboratory at MPI's Animal Health Laboratory (AHL). All previous exotic disease investigations concerning ORT produced negative results by bacterial culture and conventional PCR. Following the recent introduction of a real-time PCR for ORT at the AHL, several tracheal wash fluids from backyard chickens ( Gallus gallus domesticus ) were tested positive. This identification constituted the first detection of ORT in New Zealand poultry. As a result, a second premise was investigated with further samples testing positive for ORT by molecular assays. This paper describes the two exotic disease investigations associated with the first detection of ORT in New Zealand poultry and its implications.

Serotyping, Genotyping, and Antimicrobial Susceptibility of Ornithobacterium rhinotracheale Isolates from Mexico.

The bacterium Ornithobacterium rhinotracheale is associated with respiratory disease and septicemia in poultry. In this study, 9 reference strains and a total of 23 isolates of O. rhinotracheale from respiratory diseased poultry from Mexico were serotyped and genotyped. Furthermore, the antimicrobial susceptibility of isolates and reference strains of O. rhinotracheale were determined. All isolates belong to serotype A and showed a clonal relationship. All reference strains and isolates were resistant to colistin, fosfomycin, gentamicin, kanamycin, streptomycin, and trimethoprim-sulfamethoxazole. These results should eventually be helpful in planning strategies for the control of O. rhinotracheale infections in poultry in Mexico.

Coinfection of Avibacterium paragallinarum and Ornithobacterium rhinotracheale in Chickens from Peru.

The coinfection of Avibacterium paragallinarum and Ornithobacterium rhinotracheale in two outbreaks of infectious coryza from Peru is reported. The diagnosis was confirmed by bacteriologic isolation, PCR testing, and sequencing of the 16S rRNA gene. The susceptibility of the isolates to 12 antimicrobial agents was tested by a disk diffusion method. The isolates were susceptible to amoxicillin/clavulanic acid and florfenicol and were resistant to oxacillin and sulfamethoxazole/trimethoprim. The coinfection of Av. paragallinarum and O. rhinotracheale and the severity of clinical signs were evaluated by experimental infection of specific-pathogen-free chickens. The group inoculated with O. rhinotracheale alone presented minimal clinical signs in 3 of 10 chickens. However, the groups inoculated with both Av. paragallinarum and O. rhinotracheale induced the most-severe clinical signs compared with the group inoculated with Av. paragallinarum alone. In conclusion, coinfections with Av. paragallinarum and O. rhinotracheale may occur, and these outbreaks could be more severe than single infections. Hence, the prevention, control, and diagnosis of Av. paragallinarum with O. rhinotracheale are important in outbreaks of infectious coryza.

Molecular Characterization of the Recently Emerged Poultry Pathogen Ornithobacterium rhinotracheale by Multilocus Sequence Typing.

Ornithobacterium rhinotracheale (ORT) is an economically important bacterial pathogen of turkeys and chickens worldwide. Since its first detection, a variety of typing methods have been used to gain basic knowledge about the bacterial population structure, an issue that still needs to be addressed. Serological characterization revealed at least 18 different serotypes (A-R) with ORT of serotype A to be predominate among poultry. This study aimed to establish a multilocus sequence typing (MLST) scheme for ORT that could easily be used by other laboratories and allows for worldwide comparison of sequence data. For this purpose, 87 ORT strains from different poultry hosts, geographical origins, years of isolation and serotypes were included in the analysis to identify correlations. Fourteen different sequence types (ST) were found. The most common ST1 was identified in 40 ORT strains from turkeys and chickens on 4 continents and in 3 different European countries. Together with ST9, both STs represented over three quarters (77%) of ORT strains used in the MLST analysis and included strains of frequently cross-reacting ORT serotypes A, E and I. Nine STs were only represented by one ORT strain and might indicate possible avian host, disease or serotype-specific relationships. In contrast, discrepancies between serotype and phylogenetic relatedness were clearly demonstrated by ORT strains that belonged to identical serotypes but differed in their ST. The overall identified low genetic diversity among strains isolated from turkeys and chickens independent of host and geographical origins suggests that ORT has only recently been introduced into domestic poultry and dispersed worldwide.

[Amyloidosis in turkeys (Meleagris gallopavo f. domestica)--a case report]. / Amyloidose beim Truthuhn (Meleagris gallopavo f. domestica)--ein Fallbericht.

High prevalence of leg disorders in fattening meat turkey farm was observed. Four birds as well as tracheal and joint swabs were submitted to the Bavarian Health and Food Safety Authority in Oberschleissheim and to the Institute of Poultry Diseases, Faculty of Veterinary Medicine, Free University of Berlin. At the post-mortem, all birds showed an inflammation of the hock joints (intertarsal joint). The histopatholical investigations revealed a chronic inflammation of the joint and amyloid deposits in the joints in two cases as well as in different tissues (liver, spleen and kidneys) in another two cases. Using polymerase chain reaction, Ornithobacterium rhinotracheale-DNA could be detected in the examined tracheal and joint swabs. On the other hand, Mycoplasma gallisepticum- and Mycoplasma synoviae-DNA could not be detected. A causal correlation between the detected infectious agent and amyloidosis in relation to the leg disorders were discussed.

Experimental comparison of hemolytic and nonhemolytic Ornithobacterium rhinotracheale field isolates in vivo.

Ornithobacterium rhinotracheale (ORT) is a nonhemolytic, gram-negative, pleomorphic, rod-shaped bacterium that causes upper and lower respiratory tract disease in poultry. Recently, hemolytic strains of ORT have been isolated with increasing frequency from field outbreaks. A study was conducted to determine whether the hemolytic phenotype is associated with any change in virulence. Briefly, 225 turkey poults, vaccinated against hemorrhagic enteritis at 4 wk of age, were randomly divided into nine replicates housed in separate rooms: three sham treatment controls (25 poults/replicate), three challenged with a nonhemolytic (NH) field isolate (24 poults/replicate), and three challenged with a hemolytic (H) field isolate (24 poults/replicate). Nine days postvaccination, poults were inoculated intratracheally with either 0.2 ml sterile phosphate-buffered saline (PBS), 2 x 10(8) colony-forming units (CFU) of the NH isolate in 0.2 ml PBS, or 2 x 10(8) CFU of the H isolate in 0.2 ml PBS. Serum and body weights were obtained at 0, 7, 14, and 21 days postinoculation (dpi). Tissues were taken for culture and histopathology from five randomly selected poults/replicates at 7, 14, and 21 dpi. When compared with poults inoculated with the H isolate or controls, those inoculated with the NH isolate showed a highly significant depression in weight gain at 7 dpi. NH poults also had significantly higher levels of antibody against ORT at 14 and 21 dpi. Reisolations decreased over time and, by 21 dpi, only the NH phenotype could be found. Based on a Likert-type scale, poults inoculated with the NH isolate had significantly higher histopathologic lesion scores in lung tissue at 7, 14, and 21 dpi. Results suggest that nonhemolytic field isolates are more virulent then hemolytic ones. These findings are unusual because hemolytic phenotypes are often more virulent in other bacterial species.

Development of real-time polymerase chain reaction assay for detection of Ornithobacterium rhinotracheale in poultry.

Ornithobacterium rhinotracheale (ORT) is an emerging bacterium causing severe economic losses in poultry mostly due to respiratory and locomotory disturbances. Due to the fastidious nature of the organism, ORT is often overgrown by faster-growing commensal and pathogenic bacteria. In this study we developed a real-time polymerase chain reaction (qPCR) assay for rapid and sensitive detection of ORT in samples collected from chickens and turkeys. The qPCR assay developed was able to detect 17 reference strains of ORT (serotypes A to Q) tested in this study, and no false-positive results were obtained from other organisms associated with respiratory tract infections. The qPCR assay was 100 times more sensitive than the modified conventional PCR. Using tenfold serial dilutions of the recombinant plasmid DNA containing the target gene fragment, the detection limit of the qPCR was estimated to be > or = 100 plasmid copies per reaction. Out of 42 examined poultry flocks, 26 cases were tested positive by both assays. The qPCR assay reduces turnaround time to about 2 hr, two times faster than the modified conventional PCR.

Adherence of five serovars of Ornithobacterium rhinotracheale to chicken tracheal epithelial cells.

1. Interaction between bacteria and host tissue is important, both for primary adhesion and tissue-specific colonisation, as well as for pathogen invasion for different host tissues. 2. Ornithobacterium rhinotracheale is a bacterium associated with respiratory tract infections in poultry. The mechanisms by which O. rhinotracheale causes infection are not known. To date, at least 18 serovars of this bacterium, with or without the ability to agglutinate erythrocytes of chicken and other species, have been identified. 3. The purpose of this work was to evaluate the ability of five references strains, belonging to serovars A, B, C, D and E, to adhere to a culture of primary chicken tracheal cells. 4. Serovars A and B adhered to less than 20% of tracheal cells with no specific adherence pattern. Serovars C, D and E gave adherence values greater than 70%. Serovars C and E showed a diffuse adherence pattern, while serovar D had an aggregated adherence pattern. 5. The adherence ability and pattern could be associated with different pathogenicity mechanisms in the various serovars but more studies are needed to understand the reasons for these differences.

Isolation and characterization of small-colony variants of Ornithobacterium rhinotracheale.

Ornithobacterium rhinotracheale is a Gram-negative bacterium associated with respiratory diseases in many avian species, with worldwide distribution, and it causes significant economic loss to the poultry industry. In this study, the isolation and characterization of O. rhinotracheale small-colony variants (SCVs) are described for the first time. O. rhinotracheale isolates (n = 27) were recovered from tracheal samples (n = 321) collected from different avian species with clinical signs of respiratory disease. Of the 27 O. rhinotracheale isolates, 21 (77.8%) showed SCVs in their primary cultures. Five O. rhinotracheale SCV isolates showed high levels of stability and were chosen for further characterization with their wild-type (WT) isolates. Stable O. rhinotracheale SCVs were oxidase negative, while their WT isolates were positive. Growth curves for stable O. rhinotracheale SCVs indicated lower growth rates and longer lag phases than for their WT isolates. Furthermore, it was possible to increase the efficacy of the broth medium in supporting the growth of O. rhinotracheale WT isolates by supplementing it with 5% fetal bovine serum (FBS) and 2% IsoVitaleX Enrichment. Antibiotic susceptibility tests showed that O. rhinotracheale SCVs had higher MIC values than their WT isolates. This study suggests that successful antibiotic treatment of respiratory diseases associated with O. rhinotracheale must take into consideration the resistance patterns of O. rhinotracheale SCVs. Intracellular persistence in murine RAW 264.7 macrophages revealed that O. rhinotracheale SCV28 had higher survival rates than its WT isolate. Finally, small-colony variants may be important contributors to the pathogenesis of O. rhinotracheale.

Ornithobacterium rhinotracheale has neuraminidase activity causing desialylation of chicken and turkey serum and tracheal mucus glycoproteins.

Neuraminidases (sialidases) are virulence factors of several poultry pathogens. Ornithobacterium rhinotracheale is a well known poultry pathogen causing respiratory disease in chickens and turkeys all over the world. We investigated whether O. rhinotracheale has neuraminidase enzymatic activity (NEAC). We tested NEAC in 47 O. rhinotracheale strains isolated from turkeys and chickens in eight countries. All strains showed relatively strong NEAC and considerable levels of NEAC were detected also in "cell-free supernatants" of their pelleted cells. Zymography using neuraminidase-specific chromogenic substrate indicated that a protein with molecular mass of ~40kDa and isoelectric point (pI) of ~8.0 is a putative neuraminidase of O. rhinotracheale. Notably, the genome of the type strain of O. rhinotracheale, DSM 15997 contains a gene (Ornrh_1957) encoding a putative neuraminidase with such Mw (39.5 kDa) and pI (8.5). We sequenced a corresponding genomic region of 20 O. rhinotracheale strains and found five distinct types of the neuraminidase gene (termed nanO) sequences. Most diversified nanO sequence was found in two strains isolated from chickens in Hungary in 1995. Their nanO sequences differ from that of the type strain (LMG 9086(T)) in 27 nucleotides. O. rhinotracheale neuraminidase showed capacity to cleave sialic acid from chicken and turkey glycoproteins. It cleaved sialic acid from SAα(2-6)gal moiety of their serum proteins, including immunoglobulin G (IgG) and transferrin. O. rhinotracheale also desialylated chicken and turkey tracheal mucus glycoprotens with SAα(2-3)gal moieties. This study provides the first evidence that O. rhinotracheale has neuraminidase which can desialylate glycoproteins of its natural hosts.

[Relevance and diagnostics of selected bacterial pathogens of poultry]. / Bedeutung und Diagnostik ausgewählter bakterieller Erreger des Geflügels.

This paper provides an overview of diseases caused by Bordetella avium, Gallibacterium anatis, Ornithobacterium rhinotracheale, Riemerella anatipestifer and Enterococcus cecorum in poultry flocks. These bacterial species are almost exclusively found in birds. Their identification with biochemical methods is described and alternative molecular biological methods are discussed.

Detection and typing of Ornithobacterium rhinotracheale from German poultry flocks.

Ornithobacterium rhinotracheale (ORT) is a gram-negative staining rod. In chickens and turkeys ORT causes a respiratory disease. Between 2009 and 2011 some 714 dry swabs taken from diseased turkeys, broilers, broiler breeders, layers, or from unknown origin were investigated by PCR for the presence of ORT. Swabs that tested positive numbered 197 out of 481 from turkeys (41.0%), 10 out of 144 from broilers or broiler breeders (6.9%), 17 out of 28 from layers (60.7%), and 26 out of 61 from unknown origin (42.6%). The results of three swabs from turkeys were suspect. Furthermore, 310 isolates from turkeys and 62 isolates from unknown origin were typed using an agar gel precipitation (AGP) test. Of the isolates from turkeys, 56.1% belonged to serotype A and 20.6% to serotype E. The prevalence of other isolates was below 10%. Serotypes D, F, and K were not detected. Eleven isolates were not typable with reference sera against serotypes A-L. The three serotypes most often found in the isolates from unknown origin were A (35.5%), B (19.4%), and C (12.9%). The prevalence of other isolates was below 10%. Serotypes F and K were not detected. Seven isolates were not typable with reference sera A-L. Cross-reactions, especially of serotype A isolates with serotypes I, H, and J, were common. Additionally, the partial 16S ribosomal RNA (rRNA) and the complete Or01 genes of reference strains A-H and of nine field isolates were cloned and sequenced. Identity scores of 16S rRNA fragments were between 98% and 100%. Identities of the Or01 sequences were between 94% and 100%. Phylogenetic trees of both genes showed similarities. However, there was no apparent correlation between reference strains and isolates belonging to one serotype, so sequencing of 16S rRNA or of the Or01 gene does not seem to be a suitable method to replace the AGP for serotyping. Further investigations are necessary to clarify the cross-reactions between different serotypes and their real role in the pathogenicity and in consideration of vaccine production.