Clostridium difficile in vegetables, Canada.

BACKGROUND: Clostridium difficile is an important gastrointestinal pathogen of humans and animals. It has been isolated from various foods, including meat and ready-to-eat salads, and concern has been expressed regarding food as a possible source of human C. difficile infection (CDI). AIMS: We sought to isolate C. difficile from a variety of vegetables obtained from local grocery stores and to characterize these isolates. MATERIALS AND METHODS: Vegetables were purchased from 11 different grocery stores in Guelph, Ontario, Canada between May and August 2009. Enrichment culture was performed and isolates were characterized by ribotyping, PFGE, toxinotyping and PCR detection of toxin genes. RESULTS: Clostridium difficile was isolated from 4.5% (5/111) of retail vegetables. Two different ribotypes and two different toxinotypes were identified. Three isolates were ribotype 078/NAP 7/toxinotype V, possessing all three toxin genes. The other two isolates shared a ribotype with a toxigenic strain previously found in humans with CDI in this region. DISCUSSION: Contamination of vegetables was found at relatively low levels, however, all isolates were toxigenic and belonging to ribotypes previously associated with CDI. CONCLUSIONS: Contamination of vegetables with CDI-associated isolates can occur and although the implications for food safety practices remain elusive, the presence of toxigenic isolates suggests vegetables could be a source of C. difficile in humans.

A search for virulence genes of Haemophilus parasuis using differential display RT-PCR.

Although Haemophilus parasuis is an important bacterial pathogen of swine, little is known about its pathogenesis or why some strains seem to be more virulent than others. Therefore, we used differential display reverse transcription-polymerase chain reaction (DDRT-PCR) to search for virulence-associated genes in a pathogenic serotype 5 strain, H. parasuis 1185. Gene expression was evaluated following growth in conditions chosen to begin to approximate those found in the upper respiratory tract and those encountered by the organism during acute infection. Seven different differentially expressed gene fragments were identified in cells grown at 40 degrees C in both the presence and absence of swine serum. Based on the deduced amino acid sequences, the most strongly up-regulated genes were homologs of fadD (a fatty acyl-CoA synthetase), apaH (diadenosine tetraphosphatase), pstI (enzyme I of the phosphoenolpyruvate-protein phosphotransferase system), and cysK (cysteine synthetase). Homologs of Std (Na(+)- and Cl(-)-dependent ion transporter), HSPG (a mammalian basement membrane-specific heparin sulphate core protein precursor) and PntB (pyridine nucleotide transhydrogenase) were also up-regulated, but to a much lower extent. Sequences homologous to all of the differentially expressed genes were detected in the reference strains of all 15 H. parasuis serotypes. This is the first report of a global search for virulence factors of H. parasuis.