Role of Position 627 of PB2 and the Multibasic Cleavage Site of the Hemagglutinin in the Virulence of H5N1 Avian Influenza Virus in Chickens and Ducks

Highly pathogenic H5N1 avian influenza viruses have caused major disease outbreaks in domestic and free-living birds with transmission to humans resulting in 59% mortality amongst 564 cases. The mutation of the amino acid at position 627 of the viral polymerase basic-2 protein (PB2) from glutamic acid (E) in avian isolates to lysine (K) in human isolates is frequently found, but it is not known if this change affects the fitness and pathogenicity of the virus in birds. We show here that horizontal transmission of A/Vietnam/1203/2004 H5N1 (VN/1203) virus in chickens and ducks was not affected by the change of K to E at PB2-627. All chickens died between 21 to 48 hours post infection (pi), while 70% of the ducks survived infection. Virus replication was detected in chickens within 12 hours pi and reached peak titers in spleen, lung and brain between 18 to 24 hours for both viruses. Viral antigen in chickens was predominantly in the endothelium, while in ducks it was present in multiple cell types, including neurons, myocardium, skeletal muscle and connective tissues. Virus replicated to a high titer in chicken thrombocytes and caused upregulation of TLR3 and several cell adhesion molecules, which may explain the rapid virus dissemination and location of viral antigen in endothelium. Virus replication in ducks reached peak values between 2 and 4 days pi in spleen, lung and brain tissues and in contrast to infection in chickens, thrombocytes were not involved. In addition, infection of chickens with low pathogenic VN/1203 caused neuropathology, with E at position PB2-627 causing significantly higher infection rates than K, indicating that it enhances virulence in chickens

Serological evidence for a non-protective RHDV-like virus

The data were recorded during a Rabbit haemorrhagic disease outbreak that occurred in France in 2001 in a wild population of rabbits that we have been monitoring since 2000. These data suggested the existence of non-protective antibodies due to a putative RHDV-like virus. Twenty-one blood and 22 liver samples were taken from the 26 corpses of recently dead rabbits that were found. RHDV was found in all liver samples. A first screening for RHD antibodies, carried out using an ELISA based on the detection of VP60-RHDV antigen, showed that 20 of the rabbits were seropositive. Moreover, we determined antibody titres for 13 of these 20 seropositive samples. All were $\geq$ 1/400. Such titres normally indicate antibody levels sufficient to confer protection to all known RHDV or RHDV-like strains. For 16 samples, we determined whether these rabbits had died of a chronic or an acute form of the disease, by employing monoclonal antibody (Mabs) – based differential ELISA. All had died of an acute form of RHD. Because the antibodies detected by this VP60-ELISA test are known to appear 5–6 days after infection and since acute RHD generally kills the rabbits 2–3 days after infection, we assumed that the detected antibodies must have been present before the exposure to the virus that killed these rabbits. A second detection of antibodies was made with Mabs that are specific for RHDV. The results were negative, showing that the antibodies detected with the VP60 ELISA test were not specific for RHDV. We sequenced a portion of the VP60 gene of viruses isolated in 17 rabbits. All RHDV isolates were very similar to the RHDV strains commonly isolated in France during this period, suggesting that this viral strain was not a putative variant that is not neutralised by antibodies. Therefore we conclude that the detected antibodies were probably due to a RHDV-like virus that induces the production of detectable but non-protective antibodies

Appropriateness of blood culture testing parameters in routine practice. Results from a cross-sectional study.

International audienceWe aimed to assess the appropriateness of routine blood culture testing parameters and antimicrobial therapy for patients with suspected bloodstream infection. We conducted a cross-sectional study of blood cultures registered in the microbiological laboratory at a university-affiliated hospital from 4 to 15 June 2007. Using a structured implicit chart review, two infectious disease specialists assessed the appropriateness of the testing parameters and antimicrobial therapy. Overall, 2,696 blood culture bottles were collected from 260 patients during their stay, including 955 bottles that were evaluated during the study period. The indication of fungal and bacterial blood cultures was rated as appropriate for 75% (95% confidence interval [CI], 65-83) and 91% (95% CI, 87-95) of patients. Only 45% (95% CI, 39-52) of patients had an adequate number of blood cultures (i.e., two to four). An optimal volume of blood (i.e., ≥10 mL) was inoculated in 13% (95% CI, 11-15) of adult bottles. Empirical antimicrobial therapy was appropriate for 60% (95% CI, 43-76) of patients with positive blood cultures. There is room for improvement regarding routine blood culture testing parameters and antimicrobial therapy. The effectiveness of multifaceted interventions in altering the appropriateness of blood culture parameters deserves further research

Incidence and prevention of infective endocarditis and bacteraemia after transcatheter aortic valve implantation in a French university hospital: a retrospective study

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