Genetic and antigenic dynamics of influenza A viruses of swine on pig farms in Thailand.

Surveillance studies of influenza A virus of swine (IAV-S) have accumulated information regarding IAVs-S circulating in Thailand, but how IAVs-S evolve within a farm remains unclear. In the present study, we isolated 82 A(H1N1)pdm09 and 87 H3N2 viruses from four farms from 2011 through 2017. We then phylogenetically and antigenically analyzed the isolates to elucidate their evolution within each farm. Phylogenetic analysis demonstrated multiple introductions of A(H1N1)pdm09 viruses that resembled epidemic A(H1N1)pdm09 strains in humans in Thailand, and they reassorted with H3N2 viruses as well as other A(H1N1)pdm09 viruses. Antigenic analysis revealed that the viruses had acquired antigenic diversity either by accumulating substitutions in the hemagglutinin protein or through the introduction of IAV-S strains with different antigenicity. Our results, obtained through continuous longitudinal surveillance, revealed that IAV-S can be maintained on a pig farm over several years through the generation of antigenic diversity due to the accumulation of mutations, introduction of new strains, and reassortment events.

National antimicrobial resistance surveillance among clinical isolates of Streptococcus pneumoniae in Thailand.

As part of the continuing national antimicrobial surveillance, the national antimicrobial resistance surveillance thailand (NARST), data of all clinical isolates of Streptococcus pneumoniae were collected from 28 hospitals in Thailand from 2000 to 2005. Epidemiological and microbiological data were obtained and analyzed using the WHONET software program. Among all isolates tested for antimicrobial susceptibility, the rates of penicillin resistance were constantly high, ranging from 42.4% in 2000 to 47.7% in 2005. The third-generation cephalosporin resistance rate, determined by Epsilon test (E-test) in 10% to 15% of all isolates each year, ranged from 2.1% to 8.4%. The rates of erythromycin resistance ranged from 24.2% to 30.3%. Surprisingly, one isolate in 2005 was resistant to levofloxacin. The rates of multi-drug resistance ranged from 14.8% to 34.3%. In conclusion; the present (NARST) study documents remarkable increase of penicillin, erythromycin, and multi-drug resistance rates in Thailand, especially among isolates from the North, the Center, the East, and Bangkok; from university hospitals; from young children; and from non-sterile specimens.

Co-infection of influenza A viruses of swine contributes to effective shuffling of gene segments in a naturally reared pig.

Following the 2009 H1N1 pandemic, surveillance activities have been accelerated globally to monitor the emergence of novel reassortant viruses. However, the mechanism by which influenza A viruses of swine (IAV-S) acquire novel gene constellations through reassortment events in natural settings remains poorly understood. To explore the mechanism, we collected 785 nasal swabs from pigs in a farm in Thailand from 2011 to 2014. H3N2, H3N1, H1N1 and H1N2 IAVs-S were isolated from a single co-infected sample by plaque purification and showed a high degree of diversity of the genome. In particular, the H1N1 isolates, possessing a novel gene constellation previously unreported in Thailand, exhibited greater variation in internal genes than H3N2 IAVs-S. A pair of isolates, designated H3N2-B and H1N1-D, was determined to have been initially introduced to the farm. These results demonstrate that numerous IAVs-S with various gene constellations can be created in a single co-infected pig via reassortment.