Characterization of Finnish Campylobacter isolates: Species identification, survival on fresh produce and molecular epidemiology

    Tutkimustuotos: OpinnäyteVäitöskirjaArtikkelikokoelma

    Abstrakti

    Campylobacter jejuni and C. coli are the most frequent causes of bacterial gastroenteritis in Finland. Most Campylobacter infections are sporadic and the sources of infection remain unidentified. Risk factors for Campylobacter infections include eating undercooked meat, especially chicken, drinking unpasteurized milk or contaminated water, having contact with pets and foreign travel. The asaccharolytic nature and inertness in traditional biochemical tests makes the identification of Campylobacter spp. difficult. We studied the phylogeny of 12 Campylobacter spp. based on partial 593-bp groEL gene sequences. In general, lower interspecies sequence similarities were observed for groEL (range from 65% to 94%) than for the 16S rRNA gene (range from 90% to 99%). However, the intraspecies groEL sequence similarities were high (range from 95% to 100%) making groEL gene sequencing and the PCR-RFLP method developed in our study valuable for the identification of Campylobacter species. The minimum growth temperature of around 30°C makes multiplication of Campylobacter in foods highly unlikely. However, the survival in cool and humid conditions, such as chicken meat stored refrigerated, has been shown to be good. The survival of C. jejuni was investigated on iceberg lettuce, cantaloupe, cucumber, carrot and strawberries. Survival on strawberries was significantly lower than on the other produce, as was survival at 21°C compared to 7°C. Survival on the other produce was comparable with earlier reports in water and milk, but not as good as that observed on chicken meat. The association of Penner HS serotypes and pulsed-field gel electrophoresis (PFGE) SmaI/KpnI genotypes of 208 human and 30 chicken caecal C. jejuni isolates was studied during the seasonal peak in 1999 in Finland. Of the strains from humans, 46% had overlapping sero/genotypes with those from chicken. During the seasonal peak in 2003, C. jejuni and C. coli isolates from human fecal samples showed 5.7% and 61% PFGE (KpnI) profile overlap with cattle fecal and poultry retail meat isolates, respectively, demonstrating the importance of genotypes circulating in chicken as compared to those isolated from cattle in human infections. However, in 1999, human cases were also isolated prior to the slaughter of the chicken flock colonized by the same Campylobacter sero/genotype, suggesting that common environmental sources may exist for both human infections and chicken flock contamination. Multilocus sequence typing analysis of 361 Finnish C. jejuni and C. coli isolates from human patients, cattle, chicken and turkey samples, provided new information on the potential association of some clonal groups of this diverse organism with source of isolation as well as demographic characteristics.
    Alkuperäiskielienglanti
    JulkaisupaikkaHelsinki
    Kustantaja
    Painoksen ISBN978-952-92-2424-1
    Sähköinen ISBN978-952-10-4071-9
    TilaJulkaistu - 2007
    OKM-julkaisutyyppiG5 Tohtorinväitöskirja (artikkeli)

    Tieteenalat

    • 413 Eläinlääketiede
    • opinnäytteet
    • Campylobacter
    • bakteerit
    • elintarvikemikrobiologia
    • lajinmääritys
    • tuoretuotteet
    • epidemiologia
    • kampylobakteerit
    • henkiinjääminen

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