Detection of E. coli O157:H7 in raw ground beef by Pathatrix™ immunomagnetic-separation, real-time PCR and cultural methods.

Detection of Escherichia coli O157:H7 by conventional cultural methods can be difficult in food matrices with a high background flora such as raw ground beef. Raw ground beef samples, artificially contaminated separately with five strains of E. coli O157:H7 at low (~0.2 cfu/g) and high (~2 cfu/g) levels, were enriched by two enrichment protocols; buffered peptone water (BPW) at 37 °C for 5h and 24h and modified buffered peptone water with pyruvate (mBPWp) for 5h at 37 °C followed by adding selective agents and incubating at 42 °C to 24h. Detection of added E. coli O157:H7 by real-time PCR (RTiPCR) and recovery on isolation agars was performed before and after PATHATRIX™ immunomagnetic separation (IMS). RTiPCR detection and cultural recovery of inoculated E. coli O157:H7 after 5h enrichment were poor at 0.21-0.24 cfu/g. The addition of IMS after 5h enrichment did not improve RTiPCR detection but markedly improved recovery by culturing. By extending enrichment to 24h, RTiPCR detection improved to 76% for either enrichment protocol without IMS. When 24h enrichment was followed by IMS, RTiPCR detection was also further improved. Cultural recovery after 24h enrichment was 56% and 84% without IMS and 100% and 92% after IMS for BPW and mBPWp respectively. Extended enrichment to 24h followed by IMS was found to be sensitive and reliable for detection and cultural recovery from raw ground beef using either enrichment method.

Comparison of Petrifilm Staph Express Count System with the bacteriological analytical manual direct-plating method for enumeration of Staphylococcus aureus in artificially contaminated hard cheese.

The 3M Petrifilm Staph Express Count System was compared with the U.S. Food and Drug Administration's Bacteriological Analytical Manual (BAM) direct-plate count method for the enumeration of Staphylococcus aureus in 6 types of artificially contaminated hard cheese (Asiago, Cheddar, Gruyère, Parmesan, Romano, and Swiss). Five different samples of each cheese type were inoculated with S. aureus (ATCC 25923) to achieve low, medium, and high inoculum levels. S. aureus was enumerated by the Petrifilm and BAM methods, and the results were compared. Multivariate analysis of variance revealed no significant differences (P<0.05) between the 2 methods. The Petrifilm method compared favorably with the BAM procedure. The rapid method was more convenient to use, considerably faster, and less expensive to perform than the BAM method.

Lack of therapeutic effect of a specially designed yogurt for the eradication of Helicobacter pylori infection.

BACKGROUND: Current antibiotic treatment for Helicobacter pylori infection is often associated with frequent adverse effects and resistance to antibiotics. Alternative treatment methods to control H. pylori infection are needed. Some specific strains of lactic acid bacteria (probiotics) in dairy products are known to inhibit the growth of H. pylori in vitro. A clinical trial was conducted to see the efficacy of a specially designed yogurt product containing specific probiotics on the eradication of H. pylori. METHOD: The yogurt was prepared using three Lactobacillus spp. (L. acidophilus and L. casei) and one commercial starter culture (L. acidophilus, L. bulgaricus and Streptococcus thermophilus). All these cultures were previously evaluated, and found to have strong in vitro inhibitory effects on the growth of H. pylori. Twenty-seven asymptomatic women positive for H. pylori on gastric biopsy and 13C urea breath test were recruited, and administered 175 ml of the yogurt three times a day for 30 days. The 13C urea breath test was administered again, one month after stopping the yogurt treatment to detect the presence of H. pylori. RESULTS: In 26 of 27 subjects, the urea breath test values remained positive, indicating that the consumption of the yogurt had no effect on the eradication of H. pylori. CONCLUSION: Although the designed fermented milk containing lactobacilli is very effective in the inhibition of H. pylori growth in vitro, eradication of this infection in humans is difficult to achieve by consuming this product.

Inhibition of Amino Acid Decarboxylase Activity of Enterobacter aerogenes by Active Components in Spices.

The water and ethanol extracts of several commercially available spices were examined for their inhibitory action on the decarboxylase activity of a crude extract of Enterobacter aerogenes . The water extracts had a negligible effect on histidine decarboxylase activity, except for water extract of cloves which reduced the activity by about 40%. However, the ethanol extracts had a rather higher inhibitory action upon histidine, lysine, and ornithine decarboxylases. Of the spices used, cloves, cinnamon, sage, nutmeg, and allspice were very effective in inhibiting the decarboxylases. Among the components of those spices, cinnamaldehyde and eugenol were found to be effective inhibitors.

Combined Effect of Sodium Chloride and Clove on Growth and Biogenic Amine Formation of Enterobacter aerogenes in Mackerel Muscle Extract.

The inhibitory effects of clove (0.5%) and sodium chloride (1-5%) on the growth and biogenic amine (histamine and cadaverine) production of Enterobacter aerogenes in mackerel muscle broth at 30°C were investigated. At 1% level, sodium chloride was favorable for growth, whereas higher levels slightly reduced the growth in comparison to the control. The maximum population numbers obtained in the presence of sodium chloride were essentially the same as that of the control. Amine production was remarkably enhanced by the presence of 1 % NaCl alone. Only a little increase was observed for higher levels, and sodium chloride at more than 3% had no stimulatory effect on the amine formation. Addition of clove at a level of 0.5% to the broth resulted in a delay in the growth and the amine formation. The presence of NaCl as low as 2% in combination with clove (0.5%) completely inhibited the growth and amine production of E. aerogenes in mackerel broth. Synergistic effects of clove essential oils and sodium chloride could be considered as the probable reason for the inactivation of the bacterium.