Porcine circovirus type 3 (PCV3) is a newly identified circovirus from swine in the USA, China and Poland. This novel circovirus has been associated with porcine dermatitis and nephropathy syndrome (PDNS), reproductive failure and multisystemic inflammation; moreover, PCV3 poses a potential threat to the swine industry. In this retrospective study, a phylogenetic analysis was conducted to address the epidemiology and evolutionary dynamics of this novel circovirus. The total positive sample rate of PCV3 was 26.7% (76/285) and has increased gradually over the past 3 years. Of these PCV3-positive samples, 22.3% (17/76) were coinfected with PCV2. PCV3 can be detected in multiple sample types with different positive rates, and the positive rate is highest among stillborn. We also divide PCV3 into three clades (PCV3a, PCV3b and PCV3c) based on two amino acid mutations (A24V and R27K) on the cap protein in this study. In addition, the origin of PCV3 was approximately 1966 and may have originated from a bat-associated circovirus. Our results suggested that PCV3 is widely distributed in southern China and has been circulating in swine herds for nearly half a century. PCV3 has evolved into different clades caused by mutations in cap proteins; thus, further research on PCV3 epidemiology should be conducted.

As a cause of community-acquired infections, extended-spectrum β-lactamase (ESBL)-producing Escherichia coli constitute an emerging public-health concern. Few data on the molecular epidemiology of ESBL-producing E. coli isolates from pets are available in China. Detection and characterization of ESBL genes (bla(CTX-M), bla(SHV) and bla(TEM)) was conducted among 240 E. coli isolates recovered from healthy and sick pets in South China from 2007 to 2008. The clonal relatedness of ESBL-producing E. coli isolates was assessed by pulsed field gel electrophoresis. ESBL-encoding genes were identified in 97 (40.4%) of the 240 isolates and 96 (40.0%) of them harbored CTX-M. The most common CTX-M types were CTX-M-14 (n = 45) and CTX-M-55 (n = 24). The recently reported CTX-M-64 was identified in three isolates. Isolates producing CTX-M-27, -15, -65, -24, -3 and -9 were also identified. Ten isolates carried two or three CTX-M types, with the combination of CTX-M-14 and CTX-M-55 being the most frequent (n = 6). ISEcp1 was identified in the upstream region of 93 out of the 107 bla(CTX-M) genes (86.9%). The sequence of the spacer region (45 bp) between ISEcp1 and the start codon of all bla(CTX-M-55) genes (except four) was identical to that of bla(CTX-M-64). No major clonal relatedness was observed among these CTX-M producers. It is suggested that the horizontal transfer of bla(CTX-M) genes, mediated by mobile elements, contributes to their dissemination among E. coli isolates from pets. Our finding of high prevalence of ESBL in E. coli of companion animal origin illustrates the importance of molecular surveillance in tracking CTX-M-producing E. coli strains in pets.

Summary Porcine circovirus type 3 (PCV3) is a novel circovirus that was associated with porcine dermatitis and nephropathy syndrome, reproductive failure, and multisystemic inflammation. Recently, a PCV3 strain was identified from pyretic and pneumonic piglets in Guangdong province, China. This virus strain was sequenced and designated PCV3‐China/GD2016. The complete genome of PCV3‐China/GD2016 is 2,000 bp in length and shared 99.1% and 99.1% nucleotide identities with PCV3/29160 and PCV3/2164, respectively. [Corrections added after initial online publication on 13 March 2017: The numbers ‘98.5%’ and ‘97.4%’ has been changed to ‘99.1%’ and ‘99.1%’ in the previous sentence.] Phylogenetic analysis based on the complete genome showed that PCV3‐China/GD2016 clustered with the emerging PCV3 and separated with other virus in genus Circovirus. The results of this study suggest that PCV3 has existed within the pigs of China. It is urgent to investigate the pathogenicity and epidemiology of this novel circovirus China.

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