L. Fodor

Investigation of the Ecology of Francisella tularensis During an Inter-Epizootic Period

A 1-year study of the ecological cycle of Francisella tularensis was performed in an enzootic area during an inter-epizootic period. The study was based on multiple sampling of all major constituents of the disease cycle. Seroprevalence of tularemia in the European brown hare (Lepus europaeus) population was 5.1% (10/197) with low antibody titers (1/10 and 1/20), and F. tularensis ssp. holarctica was isolated from four hares. F. tularensis was not detected in the 38 common voles (Microtus arvalis), 110 yellow-necked mice (Apodemus flavicollis), or 15 stripped field mice (Apodemus agrarius) trapped during the study, or the by-catch of 8 Eurasian pygmy shrews (Sorex minutus) or 6 common shrews (Sorex araneus). A total of 1106 Ixodes ricinus and 476 Haemaphysalis concinna ticks were collected from vegetation, and 404 I. ricinus, 28 H. concinna ticks, and 15 Ctenophtalmus assimilis and 10 Nosopsyllus fasciatus fleas were combed off small mammals. One H. concinna female and one nymph collected from the vegetation was found infected with F. tularensis ssp. holarctica by TaqMan polymerase chain reaction, thus resulting a 0.42% (2/476) prevalence. F. tularensis-specific DNA was not detected in environmental water samples, and the examined 100 sheep, 50 cows, and 50 buffalos grazed at the study area were all seronegative. During inter-epizootic periods, F. tularensis ssp. holarctica seems to persist only in the European brown hare--H. concinna cycle at the studied habitat. H. concinna may not serve exclusively as an arthropod vector, but it may also harbor bacteria for 3-4 years through multiple life stages and act as an important reservoir of F. tularensis. Rodent species probably do not serve as true reservoir hosts of tularemia.

Characterization of virulence plasmid types in Rhodococcus equi isolates from foals, pigs, humans and soil in Hungary

Rhodococcus equi isolates (204) obtained from foals (lung abscesses, lymph nodes, nasal discharge, rectal swabs) bred in 15 studs located throughout Hungary, isolates from soil samples, lymph nodes of pigs and from lesions of human patients were examined to determine genotypic diversity of virulence-associated plasmids. Isolates were tested for the presence of 15-17 kDa virulence-associated protein antigen (VapA) and 20k Da (VapB) genes by polymerase chain reaction (PCR). Plasmid DNAs were isolated and analysed by digestion with restriction endonucleases for estimation of size and comparison of polymorphisms. Of 146 clinical isolates from foals in 15 studs, 129 (88.3%) gave positive results for the VapA gene, showing a 564 bp product of the expected size in the PCR amplification. Of the 129 clinical isolates from foals, 123 contained an 85 kb type I plasmid and the remaining six contained an 87 kb type I plasmid. Of 48 soil isolates from two horse studs, 26 (54.2%) were positive for VapA gene and contained an 85 kb type I plasmid. Of three pig isolates, one was positive for VapA gene and contained an 85 kb type I plasmid, and the remaining two were positive for the VapB gene, showing a 827 bp product of the expected size in the PCR amplification and were R. equi of intermediate virulence which contained a 95 kb type S5 plasmid. Of the seven human isolates, five were positive for VapB gene by PCR, these were R. equi of intermediate virulence, which contained a 95 kb type S5 plasmid. These results revealed that virulent R. equi strains harbouring a virulence plasmid of 85 kb type I or 87 kb type I, which have been found in clinical isolates from Europe and North and South America, are widespread in Hungary. Furthermore, same intermediately virulence plasmid type was found in both human and pig isolates.

Phylogeography of Francisella tularensis subsp. holarctica, Europe

Francisella tularensis subsp. holarctica isolates from Austria, Germany, Hungary, Italy, and Romania were placed into an existing phylogeographic framework. Isolates from Italy were assigned to phylogenetic group B.FTNF002–00; the other isolates, to group B.13. Most F. tularensis subsp. holarctica isolates from Europe belong to these 2 geographically segregated groups.

Tularemia of European Brown Hare (Lepus europaeus) A Pathological, Histopathological, and Immunohistochemical Study

The European brown hare (Lepus europaeus) plays an important role in the ecology of tularemia, and it may serve as a significant source of human infection. The aim of the present study was to examine the lesions induced by Francisella tularensis in 50 cases of naturally infected seropositive European brown hares. Gross pathological examination revealed scant to numerous grayish-white foci with diameters of 0.1 to 1.0 cm in single organs (24 cases) or multiple organs (20 cases) in 44 of 50 cases (88%). These lesions proved to be areas of granulomatous inflammation, frequently encompassing necrosis. F tularensis antigen was detected with immunohistochemistry in 46 of 50 cases (92%), whereas F tularensis ssp holarctica was isolated by culture and identified by polymerase chain reaction from 35 of 50 cases (70%). Infection by the respiratory route is suggested by the presence of the tissue lesions in thoracic organs of 44 of 50 cases (88%). These results emphasize the importance of the European brown hare as a reservoir of tularemia.

Characterization of Virulence Plasmids and Serotyping of Rhodococcus equi Isolates from Submaxillary Lymph Nodes of Pigs in Hungary

ABSTRACT The plasmid types and serotypes of 164 Rhodococcus equi strains obtained from submaxillary lymph nodes of swine from different piggeries in 28 villages and towns located throughout the country were examined. The strains were tested by PCR for the presence of 15- to 17-kDa virulence-associated protein antigen (VapA) and 20-kDa virulence-associated protein antigen (VapB) genes. Plasmid DNAs were isolated and analyzed by digestion with restriction endonucleases to estimate size and compare their polymorphism characteristics. None of the 164 isolates contained the vapA gene, and 44 (26.8%) isolates were positive for the vapB gene, showing a product of the expected 827-bp size in the PCR amplification. The 44 isolates of intermediate virulence contained virulence plasmids that were identified as types 1 (3 isolates), 4 (1 isolate), 5 (36 isolates), 6 (1 isolate), and 7 (2 isolates) and as a new variant (1 isolate). On the basis of restriction digestion patterns of plasmid DNAs, we tentatively designated the variant as type 17. Use of the serotyping method of Prescott showed that 110 (67.1%) out of the 164 isolates were typeable and that serotype 2 predominated (83 isolates [50.6%]), followed by serotype 1 (26 strains [15.9%]). Only one isolate belonged to serotype 3. A total of 54 (32.9%) isolates were untypeable in Prescotts system. The prevalence of R. equi strains of intermediate virulence among the isolates that came from the submaxillary lymph nodes of swine in Hungary was lower than that seen with isolates obtained elsewhere.

Identification of a proposed new serovar of Actinobacillus Pleuropneumoniae: Serovar 16

Five Actinobacillus pleuropneumoniae strains isolated from pathological lesions of porcine pleuropneumonia in Hungary could not be assigned to any of the accepted 15 serovars. Using hyperimmune serum raised against these unty-pable-serovar A. pleuropneumoniae strains in rabbits, indirect haemagglutination tests proved that they form a distinct group and there is no cross-reaction between them and the type strains of A. pleuropneumoniae. All five strains harboured the toxin-associated genes for the production (apxIA) and secretion (apxIB) of ApxI, the gene for the expression of ApxII and the largest-size (2800 bp) apxIV gene. The carbon source utilisation pattern and the sequence analysis of the 16S rRNA gene confirmed the species identification of the suggested type strain, A. pleuropneumoniae A-85/14. A new serovar of A. pleuropneumoniae - serovar 16 - is proposed with A. pleuropneumoniae A-85/14 as reference strain.

Isolation and characterisation of Rhodococcus equi from submaxillary lymph nodes of wild boars (Sus scrofa)

Rhodococcus equi has been isolated from the submaxillary lymph nodes of domesticated pigs, but little is known about the presence of R. equi in wild boars. The aim of the study was the evaluation of the incidence of R. equi in wild boars and the characterisation of them. Of 482 submaxillary lymph nodes of wild boars shot in 39 settlements throughout Hungary, R. equi was isolated from 60 specimens, and plasmid types of 82 isolates were examined. The isolates were tested for the presence of 15-17-kDa (VapA) and 20-kDa virulence-associated protein antigen (VapB) genes by polymerase chain reaction (PCR). Plasmid DNAs were isolated and analysed by digestion with restriction endonucleases to estimate size and compare their polymorphisms. None of the 82 isolates contained vapA gene but 21 isolates (25.6%) were positive for vapB gene showing 827bp product of the expected size in the PCR amplification. Sixty-one strains (74.4%) did not contain plasmid. The 21 isolates of intermediate virulence contained virulence plasmids that were identified as types 1 (1 isolate), 5 (16 isolates), 21 (1 isolate), and three new distinct plasmid variants (1-1-1 isolate), respectively. On the basis of restriction digestion patterns of plasmid DNAs, we tentatively designated the new variants as types 25-27, respectively. The prevalence of R. equi strains of intermediate virulence among the isolates originated from the submaxillary lymph nodes of wild boars (25.6%) is very similar to those of domestic pigs (26.8%) in Hungary, and plasmid type 5 is the predominating one in both groups. This is the first report of isolation of VapB-positive R. equi from wild boars in the world.

A Unique Capsule Locus in the Newly Designated Actinobacillus pleuropneumoniae Serovar 16 and Development of a Diagnostic PCR Assay

ABSTRACT Actinobacillus pleuropneumoniae causes pleuropneumonia, an economically significant lung disease of pigs. Recently, isolates of A. pleuropneumoniae that were serologically distinct from the previously characterized 15 serovars were described, and a proposal was put forward that they comprised a new serovar, serovar 16. Here we used whole-genome sequencing of the proposed serovar 16 reference strain A-85/14 to confirm the presence of a unique capsular polysaccharide biosynthetic locus. For molecular diagnostics, primers were designed from the capsule locus of strain A-85/14, and a PCR was formulated that differentiated serovar 16 isolates from all 15 known serovars and other common respiratory pathogenic/commensal bacteria of pigs. Analysis of the capsule locus of strain A-85/14 combined with the previous serological data show the existence of a sixteenth serovar—designated serovar 16—of A. pleuropneumoniae.

Susceptibility of the common hamster (Cricetus cricetus) to francisella tularensis and its effect on the epizootiology of tularemia in an area where both are endemic

Francisella tularensis is a highly infectious zoonotic agent causing the disease tularemia. The common hamster (Cricetus cricetus) is considered a pest in eastern Europe, and believed to be a source of human tularemia infections. We examined the role of the common hamster in the natural cycle of tularemia using serologic methods on 900 hamsters and real-time polymerase chain reaction (PCR) on 100 hamsters in an endemic agricultural area. We collected 374 Ixodes acuminatus ticks from the hamsters and tested them by real-time PCR. All tests were negative. To examine clinical signs, pathology, and histopathology of acute tularemia infection similar to the natural infection, two hamsters were infected with a large dose of a wild strain of F. tularensis ssp. holarctica. After a short period of apathy, the animals died on the eighth and ninth days postinfection. The pathologic, histopathologic, and immunohistochemical examination contributed to the diagnosis of septicemia in both cases. Our results confirmed previous findings that common hamsters are highly sensitive to F. tularensis. We conclude that although septicemic hamsters may pose substantial risk to humans during tularemia outbreaks, hamsters in interepizootic periods do not act as a main reservoir of F. tularensis.

First isolation of Histophilus somni from goats.

Histophilus somni (former name: Haemophilus somnus) is a Gram-negative, facultative pathogen bacterium that colonises the mucous membranes of cattle and sheep, however it was also described in American bison and bighorn sheep. It can cause local or generalised diseases and asymptomatic carriers can also occur. The presence and the etiological role of this microorganism have not been confirmed in any other domesticated species yet. The purpose of this study was to prove the presence of H. somni in goats by bacterial isolation. Nasal, vaginal or praeputial swab samples were collected from 205 goats in 10 flocks. H. somni strains were isolated from 2 out of 10 flocks; in one flock 10 H. somni strains were isolated from the genital mucosa of 17 goats, while a single H. somni strain was cultured from a vagina of 26 animals in the other flock. Partial amplification and sequencing of the 16S rRNA gene of three H. somni strains verified the identification. The comparative examination of carbon source metabolism using the Biolog Microstation ID System (Biolog, Ca) showed a close relationship of the caprine strains, while they were less related to H. somni type strain CCUG-36157 of bovine origin. H. somni strains were isolated only in the oestrus season from goat flocks with sheep contact. This is the first paper on isolation of H. somni from goats.