Serotypes and virulence genes of Pseudomonas aeruginosa isolated from mink and its pathogenicity in mink.

In this study, 20 P. aeruginosa strains were isolated from 112 farmed mink exhibiting hemorrhagic pneumonia in mideastern Shandong province, China. Serotype G (18/20) was the dominant serotype among the isolates with prevalence in mink, followed by serotype B (1/20), serotype C (1/20). The 9 virulence-associated genes of P. aeruginosa were tested using PCR. The prevalence of the virulence genes for the isolates were algD 95% (19/20), plcH 85% (17/20), exoY 80% (16/20), aprA 75% (15/20), lasB 70% (14/20), exoS 65% (13/20), exoT 60% (12/20) and toxA 60% (12/20), respectively. The 20 isolates were negative for exoU gene. The isolates exhibited multidrug resistance and cross resistance, using antimicrobial disc susceptibility assays. The animal experiments demonstrated that LD50% of the P.aeruginosa-CS-2 in the intratracheally challenged mink was 2.2 × 107.0 CFU, and 6.8 × 104.0 CFU in the intraperitoneally challenged mink. It implied that both the inoculation doses and the routes of inoculation could have influences on the pathogenicity of P. aeruginosa in mink. Therefore, the evolutionary and epidemiological surveillance of P. aeruginosa in mink should be further strengthened for public health.

Serotype and virulence genes of Klebsiella pneumoniae isolated from mink and its pathogenesis in mice and mink.

In the study, 15 K. pneumoniae strains were isolated from the mink experiencing respiratory distress in mideastern Shandong province, China, and the prevalence of K. pneumoniae in the sampled mink was 11.9% (15/126). Fourteen (93.33%) of the 15 K. pneumoniae isolates were identified as serotype K2 and hypermucoviscosity phenotype. The 12 virulence-associated genes of the K. pneumoniae isolates were tested. The prevalence of the wabG gene for the isolates were 100% (15/15), the ureA gene 100% (15/15), the rmpA gene 93.33% (14/15), the aerobactin gene 93.33% (14/15), the uge gene 93.33% (14/15), the IucB gene 80% (12/15) and the ybtA gene 13.33% (2/15). But the other five genes, fim, iroNB, wcaG, alls and kfuBC, gave a negative PCR reaction in the 15 isolates, respectively. The animal experiments using K. pneumoniae-SD-12 and K. pneumoniae-SD-21 demonstrated that the serotype K2 was high virulence for mice and mink. These finding implied there exist potential threat that K. pneumoniae pathogens could transmit to human, especially the fur animal farm workers and residents lived near the fur animal farms. Therefore, the etiology and epidemiological surveillance of K. pneumoniae in mink should be strengthened for people's public health.

Molecular characterization of H9N2 influenza virus isolated from mink and its pathogenesis in mink.

In mid-August 2013, two H9N2 influenza viruses, named A/mink/Shandong/F6/2013 (Mk/SD/F6/13) and A/mink/Shandong/F10/2013 (Mk/SD/F10/13), were isolated from lung samples of 2 of 45 farmed mink exhibiting respiratory signs in mideastern Shandong province, China. The seroprevalence of antibodies to H9N2 in mink was 20% (53/265). Based on sequence analysis, the eight nucleotide sequences showed 99.7-100% identity between Mk/SD/F6/13 and Mk/SD/F10/13. The HA, NP and NS genes of Mk/SD/F6/13 and Mk/SD/F10/13 were close to A/chicken/Zhejiang/329/2011 (H9N2), the NA and PB1 genes to A/duck/Hunan/S4111/2011 (H9N2), the PA and M genes to A/chicken/Shanghai/C1/2012 (H9N2). However, the PB2 genes had a close relationship with A/Turkey/California/189/66 (H9N2). Based on Sialic acid (SA) receptor detection, a range tissues of the mink demonstrated staining for MAA and/or SNA, and mink could serve as an intermediate host for influenza viruses with pandemic potential for the other animals. Experimental infection of mink demonstrated that mink could be infected by H9N2 influenza viruses and presented mild clinical signs, virus shedding and seroconversion, but no animals died of the disease. It implied that mammalian host-adapted avian H9N2 strains infected mink.

Interspecies transmission of canine influenza virus H5N2 to cats and chickens by close contact with experimentally infected dogs.

The novel H5N2 influenza virus, CA/SD/JT01/09, was isolated from the dog exhibiting respiratory signs in China in 2009. Dog to dog transmission of the novel H5N2 was previously confirmed. But interspecies transmission of the virus between dogs and the other animals has still remained unclear. To determine whether the virus can be transmitted directly from dogs to cats and chickens, we conducted contact exposure experiments. Susceptible cats and chickens were housed in the room which the novel H5N2 infected dogs were housed in, respectively. As a result, only one cat showed clear manifestations of H5N2 infection, but susceptibility of the other cats to H5N2 was confirmed by seroconversion. Eight of the exposure chickens showed clear manifestations of illness and 2 chickens died, and it demonstrates that chickens are susceptible to the recombinant H5N2. It implied that close contact between the H5N2-infected dogs and the cats and chickens resulted in spread of the virus to the sentinel animals.

Sequence analysis of VP1 gene of the duck hepatitis A virus type 3 strains isolated from Shandong Province of China in 2012 / 病毒学报

To reveal the genetic variation of the viral protein 1 (VP1) gene of the duck hepatitis A virus type 3 (DHAV-3), the VP1 gene of 13 virulent DHAV-3 strains isolated from Shandong province of China in 2012 were amplified by RT-PCR, sequenced and analyzed. The results showed that all the VP1 genes of the 13 isolates contained 720 nucleotides encoding 240 amino acids, and shared with nucleotide identities of 94. 6%-99.9% and amino acid identities of 95.0%-100%. The nucleotide and amino acid sequence homologies between the 13 DHAV-3 isolates and other 31 DHAV-3 reference strains were 92.5%-100% and 90. 8%-100%, respectively. Phylogenetic analysis showed that the VP1 gene of DHAV-3 had distinct geographical characteristics. Distribution of genotypes of the 44 DHAV-3 strains was as follows: except the vaccine strain B63, all the other Chinese isolates belonged to genotype I (GI), Vietnamese wild isolates mainly belonged to subtype 1 (S1) of genotype II (GII), and all Korean isolates belonged to subtype 2 (S2) of GII.

The Research on Stability of an Isolate of Riemerrella anatipestifer / 微生物学通报

The isolate GN52 of Riemerrella anatipestifer was passaged on the Martin Medium successively according to the optimum condition. The experiments included Gram staining, biochemical test, drug sensitivity test and animal experiments were carried out on the bacteria of 3rd, 11th, 21st, 31st, 41st, 51st and 61st generations. It indicated that the bacterial morphs, biochemical character, drug resistance of the strain had no obvious change, but the virulence showed a trend of reduction.

Sequence analysis for the complete provial genome of endogenous avian leukosis virus strain SD0501 / 病毒学报

The genomic DNA extracted from chicken embryo fibroblasts (CEF) of SPF chickens from three chicken farms was used as template to amplify the ALV proviral DNA by PCR with four pairs of primers, high positive detection rates of gag - gene (29/46), pol - gene (27/46), env - gene (24/46) and LTR fragment (31/46) were achieved. Eight continuous and overlapping fragments were amplified from one DNA sample with 8 pairs of primers according to published sequences, then cloned into the TA vector and se quenced. The complete sequence of the whole genome of ALV strain SD0501 was established and analyzed with DNAstar software. Comparisons of SD0501 sequence with that of other representative endogenous avian virus strains demonstrated that the genomes of ALV were relatively conservative, the nucleotide identity of all the strains was over 99.1%, and env - gene was over 98.5%. However, a low identity was demonstrated among the representative strains of different subgroups, especially, the env - gene showed obvious difference, the corresponding identity was as low as 56.3% - 91.5%.