Association of virulence genotype with phylogenetic background in comparison to different seropathotypes of Shiga toxin-producing Escherichia coli isolates.

The distribution of virulent factors (VFs) in 287 Shiga toxin-producing Escherichia coli (STEC) strains that were classified according to Karmali et al. into five seropathotypes (M. A. Karmali, M. Mascarenhas, S. Shen, K. Ziebell, S. Johnson, R. Reid-Smith, J. Isaac-Renton, C. Clark, K. Rahn, and J. B. Kaper, J. Clin. Microbiol. 41:4930-4940, 2003) was investigated. The associations of VFs with phylogenetic background were assessed among the strains in comparison with the different seropathotypes. The phylogenetic analysis showed that STEC strains segregated mainly in phylogenetic group B1 (70%) and revealed the substantial prevalence (19%) of STEC belonging to phylogenetic group A (designated STEC-A). The presence of virulent clonal groups in seropathotypes that are associated with disease and their absence from seropathotypes that are not associated with disease support the concept of seropathotype classification. Although certain VFs (eae, stx(2-EDL933), stx(2-vha), and stx(2-vhb)) were concentrated in seropathotypes associated with disease, others (astA, HPI, stx(1c), and stx(2-NV206)) were concentrated in seropathotypes that are not associated with disease. Taken together with the observation that the STEC-A group was exclusively composed of strains lacking eae recovered from seropathotypes that are not associated with disease, the "atypical" virulence pattern suggests that STEC-A strains comprise a distinct category of STEC strains. A practical benefit of our phylogenetic analysis of STEC strains is that phylogenetic group A status appears to be highly predictive of "nonvirulent" seropathotypes.

Antimicrobial resistance in Campylobacter from broilers: association with production type and antimicrobial use.

The isolation and antimicrobial resistance of Campylobacter jejuni and Campylobacter coli strains from broilers arriving in French slaughterhouses, were analysed according to production types (i.e. standard, export or free-range) and antimicrobial (i.e. coccidiostats, growth promoters or therapeutic agents) administration in flocks. Prevalence was 56.6% in standard, 51.3% in export and 80.0% in free-range broilers. Three hundred and ninety-three strains were identified. Two-thirds of the strains belonged to the species C. jejuni. The others were C. coli. Antimicrobial susceptibility testing was carried out for ampicillin, nalidixic acid, enrofloxacin, tetracycline, erythromycin and gentamicin according to a dilution method. The percentages of resistant strains were, 23, 25, 17, 57, 0.3 and 0% for C. jejuni and 29, 43, 40, 70, 31 and 0% for C. coli. Statistical analysis revealed significant difference in distribution of C. jejuni and C. coli and antimicrobial resistance according to production type or antimicrobial administration.

Disinfectant susceptibility testing of avian and swine Campylobacter isolates by a filtration method.

The susceptibility testing of disinfectants against Campylobacter jejuni and Campylobacter coli strains from broilers and pigs was investigated. The filtration method European standard EN 1040 was adapted to Campylobacter cultures and validated with reference strains. Two disinfectants were tested: 1% benzalkonium chloride active matter, as quaternary ammonium compound, and 0.63% sodium hypochlorite as chlorine-releasing agent. Both disinfectants were effective against the 34 Campylobacter strains tested after 5 min exposure under in vitro conditions. No link between resistance to disinfectants and antibiotics could be observed.