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Introduction & Objective: Listeria monocytogenes is considered as a ubiquitous foodborne pathogen which can lead to serious infections, especially in newborns, elderly, pregnant, and immunocompromised people. The organism has been isolated from many foods and may cause meningitis, septicemia and abortion in pregnant women. Also L. monocytogenes forms biofilms on many food contact surface materials and medical devices. Development of biofilms on many surfaces is a potential source of contamination of foods that may lead to spoilage or transmission of foodborne pathogens. Materials & Methods: Biofilm formation of L. monocytogenes (RITCC 1293 serotype 4a) was investigated. Hydrophobicity of L. monocytogenes was measured by MATH method. Then biofilm formation of the organism was assessed at 2, 4, 8, 16 and 20 hours on stainless steel (type 304 no 2B), polyethylene and glass by drop plate method. Results: Results indicated that L. monocytogenes with 85% of hydrophobicity formed biofilm on each of three surfaces. Biofilm formation on stainless steel surfaces was significantly more than other surfaces (p<0.05). Conclusion: The ability of biofilm formation of L. monocytogenes on medical devices and food containers is very important as far as hygiene and disease outbreaks are concerned.

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Introduction & Objective: Rosmarinus officinalis L. as a member of the Lamiaceae family and lysozyme as a natural antibacterial agent is important in food microbiology, because of its characteristics. The aim of the present study was to determine the chemical composition and anti-listerial activity of Rosmarinus officinalis essential oil (REO) alone and in combination with lysozyme for enhancement of anti-listerial activity of both substances. Materials & Methods: Rosmarinus officinalis L. was purchased from a local grocery store at Shahrekord and was identified by the Institute of Medicinal Plants, ACECR. The air-dried aerial parts were subjected to hydrodistillation using a Clevenger apparatus to obtain essential oil and yielded oil was analyzed by GC/MS. Antibacterial activity (on basis of Minimum Inhibitory Concentration (MIC) of REO was studied separately and in combination with unheated lysozyme (L) and heat-treated lysozyme (HTL) on Listeria monocytogenes at different pH (5, 6 and 7) by a micro-broth dilution assay. The collected data were analyzed by SPSS software. Results: In the current study, 98.05% of constituents of the essential oil were identified. The major components were α-pinene (14.06%), 1,8-cineole (13.62%), verbenone (11.2%), camphor (10.51%), borneol (7.3%), 3-octanone (7.02%), camphene (5.46%) and linalool (5.07%). The inhibitory action of REO was stronger at lower pH especially 5 (MIC=225 μg/mL). Inhibition by L at pH 5 was 640 μg/mL but no inhibition was seen at pH 7. HTL resulted in more effective inhibition than L, especially at pH 5 and heat-treatment 80˚C (MIC: 160 μg/mL). Conclusion: Combination of L + REO and particularly HTL + REO was led to enhancement of bacterial inhibition. It was concluded that REO by the identified chemical composition was effective alone or in combination with L or HTL on Listeria monocytogenes as a food-borne pathogen.

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Background & Aim: Listeriosis is mainly caused by consuming unpasteurized dairy products, especially soft cheese which is contaminated with listeria monocytogenes in people with a damaged immune system. The purpose of this study was to evaluate the possibility of using natural preservatives to control the growth of Listeria monocytogenes in dairy products. Methods: In the present experimental study, plants (Thymus denaensis, Jaft and green hull Pistacia atlantica) were collected from the mountains of Kohgiloyeh & Boyerahmad province and their hydroaloholic extract were prepared. Antibacterial activities, MIC and MBC, were determined by disc diffusion and microwell dilution methods. The Ampicilin disk (10µg) was used as positive control in disc diffusion. The data were analyzed by the SPSS software using One-way ANOVA. Results: The most anti-bacterial activities were found with hydroalcoholic extracts of Jaft and green hull Pistacia atlantica. Inhibition zone for the Jaft concentration was 32 mg/ml which was equal to the ampicillin disk. The minimum inhibitory concentration and minimum bactericidal concentration of Jaft extract were 125 and 250 μg/ml respectively. Conclusion: Based on the results of current study, hydroalcoholic extract of Jaft might be a suitable candidate to be used as a preservative in the food industry which is able to prevent the growth of Listeria monocytogenes.

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Background & aim: Listeria monocytogenes is one of the causes of miscarriage and stillbirth. The aim of the present study was to compare the results of the standard culture method and polymerase chain reaction in pregnant women. Methods: This is an experimental study which was carried out at Imam Sajjad hospital in 2009 on 107 pregnant women. Specimens (311) including urine, blood, placenta and cervix swabs were collected. After enrichment course, for a period of 4 weeks in cold condition, ulture was performed for all specimens. The samples were also evaluated by polymerase chain reaction (PCR). Collected data were analyzed using SPSS, using McNemar and Capa statistical tests. Results: Participants of this study were 15 to 38 years old women, with a mean age of 26.7 years. Frequencies of first and second abortion in the subjects were 59.8% and 12.1% respectively. No culture positive cases were found among the samples while PCR detected hly gene in 10.28% of the subjects. A significant different was observed between the two methods (p=0.022). Conclusion: Findings of this study demonstrated that PCR is more sensitive than culture method for diagnosis of Listeria infection in pregnant women.