Biofilm removal potential of neutral electrolysed water on pathogen and spoilage bacteria in dairy model systems.

AIMS: This study aimed to investigate the efficacy of neutral electrolysed water (NEW) on biofilm and planktonic forms of Listeria monocytogenes, Escherichia coli and Pseudomonas aeruginosa in Luria-Bertani (LB) broth, 0·5 and 3% w/w fat pasteurized and ultra high temperature (UHT) milk. METHODS AND RESULTS: Biofilm was established on stainless steels in a simulated industrial model biofilm reactor. NEW had a bactericidal effect on planktonic forms of all bacteria at 25 µg ml-1 concentration. Biofilm production index (BPI) was affected by the type of media and micro-organisms and incubation temperatures. In general, biofilms were more intense at 22°C in milk containing 3% fat than 0·5% fat and LB. The highest BPI (1·12) was reported for the biofilm of E. coli at 22°C in 3% fat pasteurized milk. No significant change in biofilm formation for any bacteria at UHT and pasteurized milk was obtained. NEW at 75 µg ml-1 concentration had more significant biofilm removal activity on all the tested bacteria. The biofilm removal property of NEW in high-fat milk was lower than that in low-fat milk and LB broth. CONCLUSIONS: NEW can be used at 75 µg ml-1 concentration as a sanitizing and biofilm removal compound in dairy plant facilities. SIGNIFICANCE AND IMPACT OF THE STUDY: This study highlighted the effect of different growth media, including culture media and different types of milk, and the biofilm removal activity of NEW on foodborne pathogens and spoilage bacteria which could be considered in plant sanitation schedule.

Novel in Vitro Efficiency of Chitosan Biomolecule against Trichomonas gallinae.

BACKGROUND: Development of new natural agents for parasitic diseases treatment has unexpectedly increased to overcome effectively against emergence and re-emergence of parasitic diseases, the appearance of drug resistant organisms and toxic side effects of current agents. The aim of the study was to evaluate antiprotozoal activities of chitosan biomolecule on trophozoites of Trichomonas gallinae. METHODS: The antitrichomonal activity of various low molecular weight chitosan concentrations including 125, 250, 500 and 1250 µg ml(-1) against T. gallinae trophozoites cultured in trypticase-yeast extract-maltose medium supplemented with heat-inactivated cold horse serum was evaluated in vitro. Samples containing medium without chitosan were also assayed as controls. RESULTS: The mortality rates at 0, 3 and 6 h post treatment with all concentrations were significantly different from control group (P<0.05). Treated trophozoites showed more susceptibility to the highest concentration reaching mortality rate of 100% at 3h post inoculation. However, at this time, results for 125, 250 and 500 µg ml(-1) were 93%, 95% and 96.7%, respectively. CONCLUSION: The results demonstrate that the application of chitosan biomolecule is a promising option for treatment of trichomoniasis in pigeons.

Essential oil of tarragon (Artemisia dracunculus) antibacterial activity on Staphylococcus aureus and Escherichia coli in culture media and Iranian white cheese.

BACKGROUND AND OBJECTIVES: In this study, the antibacterial effect of essential oil of tarragon (Artemisia dracunculus) on Staphylococcus aureus and Escherichia coli was evaluated in culture media and Iranian white cheese. MATERIALS AND METHODS: The tarragon essential oil (EO) obtained by the steam distillation method and its antibacterial activity was evaluated in 96-well microtiter plates containing brain heart infusion broth. The enumeration of S. aureus and E. coli in cheese samples were carried out on the following media: Baired parker agar for S.aureus, incubated at 37°C for 24 h; and MacConkey sorbitol agar for E. coli, incubated at 37°C for 24 h. Iranian white cheese was produced from fresh and whole pasteurized cow milk (2.5%). Bacteria (10(3) cfu/mL) were inoculated to different batches. Cheese was treated with different concentrations of EO (15 and 1500 µg/mL) and separated into four parts in an equal manner. The sensory evaluation was done by a panel of four judges. RESULTS: According to the results obtained, minimum inhibitory concentrations (MIC) for E. coli and S. aureus were 2500 and 1250 µg/mL, respectively. Also, minimum bactericidal concentration (MBC) for the mentioned microorganisms were 5000 and 2500 µg/mL, respectively. All the EO concentrations for each bacteria result in reducing bacterial count of cheese samples compared to control (P<0.05). Also, with increasing concentration of EO in cheese samples, the bacterial count was reduced further (P<0.05). CONCLUSION: Based on our findings, tarragon essential oil has antibacterial effect on two important pathogen bacteria (S. aureus and E. coli) and can be applied as a preservative in foods such as cheese.

Synergistic antibacterial activity of the essential oil of Cuminum cyminum L. seed and nisin in a food model.

AIMS: To investigate effects of various concentrations of the essential oil of Cuminum cyminum L. seed alone and in combination with nisin on survival of vegetative forms of Bacillus cereus and Bacillus subtilis in a food model (commercial barley soup) and their ultrastructure. METHODS AND RESULTS: Gas chromatography-mass spectrometry analysis indicated that cumin aldehyde (29·02%) and α-terpinen-7-al (20·70%) constituted the highest amount of the essential oil. The lowest concentration of the essential oil significantly affected the growth of the bacteria at 8°C but not at 25°C. Synergistic effect of the essential oil in combination with the lowest concentration of nisin was observed on the bacteria at 8°C. Evaluation of the sensory properties showed that concentration of 0·15 µl ml−1 of the essential oil was the most acceptable. CONCLUSIONS: The essential oil of C. cyminum L. seed showed the most bactericidal effects on B. cereus at 8°C. Ultrastructural studies of vegetative cells confirmed the synergistic destructive effects of the essential oil and nisin on membrane and cell wall of the bacteria.

Chloramphenicol residues in chicken liver, kidney and muscle: a comparison among the antibacterial residues monitoring methods of Four Plate Test, ELISA and HPLC.

There are many concerns about safety of food contaminated with antibacterial residues. This study was designed to investigate the occurrence of chloramphenicol (CAP) residue in broiler chickens tissues, namely liver, kidney and muscle. One hundred and sixty broiler chickens carcasses were collected from three provinces of Iran. Four Plate Test (FTP), ELISA and HPLC were used to qualify and quantify the contamination of the samples with CAP. The results of FPT revealed that up to 17.5% of the samples were contaminated with the antibiotic. The ELISA assay showed that out of 28 positive samples in FPT, 22 liver, 21 kidney and 14 muscle samples were positive for CAP. ELISA analyses demonstrated that the minimum and maximum levels of 0.54 and 155.2 ng/g were detected in the kidney and liver, respectively. HPLC analyses confirmed the ELISA findings although the level of contamination was lower than that of ELISA. These data showed that despite the prohibition of CAP application in food animals including poultry, the CAP residue was detectable indicating an illegal use of this antibiotic. Our findings also demonstrated the application of sensitive and more specific analytical assays in screening and quantitation of CAP residues in food products.