Comparison of virulence of Francisella tularensis ssp. holarctica genotypes B.12 and B.FTNF002-00.
BACKGROUND
Two main genetic groups (B.12 and B.FTNF002-00) of Francisella tularensis ssp. holarctica are endemic in Europe. The B.FTNF002-00 group proved to be dominant in Western European countries, while strains of the B.12 group were isolated mainly in Northern, Central and Eastern Europe. The clinical course of tularemia in the European brown hare (Lepus europaeus) also shows distinct patterns according to the geographical area. Acute course of the disease is observed in hares in Western European countries, while signs of sub-acute or chronic infection are more frequently detected in the eastern part of the continent. The aim of the present study was to examine whether there is any difference in the virulence of the strains belonging to the B.FTNF002-00 and B.12 genetic clades.


RESULTS
Experimental infection of Fischer 344 rats was performed by intra-peritoneal injection of three dilutions of a Hungarian (B.12 genotype) and an Italian (B.FTNF002-00 genotype) F. tularensis ssp. holarctica strain. Moderate difference was observed in the virulence of the two genotypes. Significant differences were observed in total weight loss values and scores of clinical signs between the two genotypes with more rats succumbing to tularemia in groups infected with the B.FTNF002-00 genotype.


CONCLUSIONS
Results of the experimental infection are consistent with previous clinical observations and pathological studies suggesting that F. tularensis ssp. holarctica genotype B.FTNF002-00 has higher pathogenic potential than the B.12 genotype.
Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Hungária körút 21, H-1143, Budapest, Hungary.
Zsuzsa
Z
Kreizinger
Veterinary Diagnostic Directorate, National Food Chain Safety Office, P.O. Box 21581, Budapest, Hungary.
Károly
K
Erdélyi
Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Hungária körút 21, H-1143, Budapest, Hungary.
Orsolya
O
Felde
Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna Bruno Ubertini, National Reference Laboratory for Tularemia, Pavia, 27100, Italy.
Massimo
M
Fabbi
Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Hungária körút 21, H-1143, Budapest, Hungary.
Kinga M
KM
Sulyok
Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Hungária körút 21, H-1143, Budapest, Hungary.
Tibor
T
Magyar
Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Hungária körút 21, H-1143, Budapest, Hungary. m.gyuranecz@gmail.com.
Miklós
M
Gyuranecz
D000818:Animals; D005060:Europe; D005260:Female; D005604:Francisella tularensis / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity*; D005838:Genotype; D051381:Rats; D014406:Tularemia / Q000469:parasitology* / Q000473:pathology; D014774:Virulence / Q000235:genetics; D015431:Weight Loss
B.12; B.13; B.FTNF002-00; Brown hare; Experimental infection; Fischer 344 rat; Tularemia