Aims: To quantify the antibacterial properties of five essential oils (EO) on a non-toxigenic strain of Escherichia coli O157:H7 in the presence and absence of a stabilizer and an emulsifier and at three different temperatures. Methods and Results: Five EOs known to exhibit antibacterial properties were screened by disc diffusion assay and the most active were selected for further study in microdilution colorimetric assays. Oregano (Origanum vulgare) and thyme (Thymus vulgaris; light and red varieties) EO had the strongest bacteriostatic and bactericidal properties, followed by bay (Pimenta racemosa) and clove bud (Eugenia caryophyllata synonym: Syzygium aromaticum) EO. Oregano oil was colicidal at 625 ll l )1 at 10, 20 and 37°C. The addition of 0AE05% (w/v) agar as stabilizer reinforced the antibacterial properties, particularly at 10°C, whereas 0AE25% (w/v) lecithin reduced antibacterial activity. Scanning electron micrographs showed extensive morphological changes to treated cells. Conclusions: Oregano and thyme EO possess significant in vitro colicidal and colistatic properties, which are exhibited in a broad temperature range and substantially improved by the addition of agar as stabilizer. Bay and clove bud EO are less active. Lecithin diminished antibacterial properties. The bactericidal concentration of oregano EO irreversibly damaged E. coli O157:H7 cells within 1 min. Significance and Impact of the Study: Oregano and light thyme EO, particularly when enhanced by agar stabilizer, may be effective in reducing the number or preventing the growth of E. coli O157:H7 in foods.

The excretion of campylobacter by eight individually housed fattening pigs was monitored during 15 weeks. Rectal faeces samples were collected six times from these pigs and twice from their mothers (seven sows). Campylobacter was cultured from these samples on Preston medium. In some pigs, samples positive for campylobacter alternated with negative samples. Campylobacter was detected in at least four of the six samples collected per fattening pig. The average campylobacter count per sampling showed a decreasing trend (P < 0·001). of the seven sows, six were shown to excrete campylobacter. Campylobacter isolates of pigs and sows were typed using the Enterobacterial Repetitive Intergenic Consensus Polymerase Chain Reaction (ERIC‐PCR); 28 different campylobacter types were distinguished. Up to five different types were isolated from single faeces samples. Individual porkers could harbour up to eight types during their fattening period. The three types most frequently isolated from the fattening pigs were also present in the sows.

The effects of proline and caffeic acid on the survival of Shiga toxin-producing Escherichia coli (STEC) O157:H7 strain ATCC 43895 in a model apple juice medium were studied. It is hypothesized that the inhibitory effect of caffeic acid may explain why almost all outbreaks of STEC O157:H7 infections linked to apple juice or cider have occurred in October or November.

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Aim: To determine the sensitivity of methods for detection of injured and uninjured Escherichia coli O157:H7 (E. coli O157) in raw and pasteurized milk. Methods and Results: Raw milk, pasteurized milk with 1AE5% fat content and pasteurized milk with 3AE5% fat content were spiked with E. coli O157 at low levels. The samples were enriched in modified tryptone soya broth with novobiocin (mTSBn) at 37°C. Aliquots of the enriched culture were analysed either by manual immunomagnetic separation (MIMS) and culturing on sorbitol MacConkey agar with or without cefixime and potassium tellurite (SMACct or SMAC), or by automated immunomagnetic separation and integrated ELISA (EiaFoss TM ). Uninjured E. coli O157 organisms were detected in milk by both methods at 1 cfu 10 ml -1 sample). Injured organisms were detected at levels of about 4 cfu 10 ml -1 sample. Direct enrichment in mTSBn (22 h incubation) showed better sensitivity for injured cells than enrichment in buffered peptone water (BPW, 22 h incubation), or in a two-step enrichment consisting of BPW (6 h, 37°C) and mTSBn (16 h, 37°C), successively. Conclusions: The methods showed equal sensitivity in that they were both able to detect 1 cfu 10 ml -1 milk sample. Injured organisms can be detected and isolated at a level almost as low as this. A resuscitation step is not recommended for the detection and isolation of injured and non-injured E. coli O157 from milk. Significance and Impact of the Study: Due to the dilution of contamination in the bulk tank, analysis of milk for the presence of E. coli O157 requires a very sensitive method. Both methods described here are useful for such analysis.