Sait Aykut Aytac

Rapid detection of Salmonella in milk by combined immunomagnetic separation-polymerase chain reaction assay.

During the past few years, milk has presented a risk of Salmonella contamination; it has been implicated as the cause in several outbreaks of salmonellosis. Because conventional detection methods require 5 to 7 d for completion and involve several subcultivation stages followed by biochemical and serological tests, rapid and sensitive methods have been sought, mainly at the DNA level. Therefore, a study including milk samples was conducted to evaluate the performance of a combination of 2 techniques--immunomagnetic separation and polymerase chain reaction (PCR)--for the detection of Salmonella. The 16-, 14-, 12-, 10-, and 8-h nonselective pre-enrichment steps before immunomagnetic separation and the high-pure DNA preparation method before PCR were used in a combined assay. Milk samples, which were found to be Salmonella-negative by a reference method, were first inoculated with Salmonella Enteritidis. Next, the shortest pre-enrichment time that is required for detection of 1 or 10 cfu of Salmonella/mL by combined immunomagnetic separation-PCR assay was found by using 16-, 14-, 12-, 10-, and 8-h incubation periods. The detection limit using a 16-, 14-, or 12-h nonselective pre-enrichment was 1 to 10 cfu/mL. However, the sensitivity decreased to 10(1) and 10(2) cfu/mL, respectively, when 10- and 8-h pre-enrichments were used. This assay, in conjunction with a 12-h pre-enrichment, proved to be rapid (overall 16 h) and sensitive (1-10 cfu/mL) for the detection of Salmonella in milk samples and promising for routine use in the detection of Salmonella in milk.

Effects of modified atmosphere and vacuum packaging on the growth of spoilage and inoculated pathogenic bacteria on fresh poultry

Fresh chicken breast meats inoculated withYersinia enterocolitica andAeromonas hydrophila were packaged in glass jars either containing different compositions of modified atmospheres (MA) (100% CO2; 80% CO2/20% N2), or in vacuo or containing air, and were stored at 3±1°C and 8±1°C. The changes in gas composition as well asY. enterocolitica, A. hydrophila, total aerobic bacterial, total psychrotrophic, Lactobacilli and Enterobacteriaceae counts were determined after 0,1,3,7,9,11 and 14 days of storage. The results show that while the growth ofY. enterocolitica andA. hydrophila were retarded following MA storage, the pathogens were capable of growth in MA and vacuum storage at both temperatures, for the inoculation levels studied. For total aerobic bacterial counts, there were no differences between the values for chicken breast meats kept in different atmospheres. Being packaged in CO2 had the greatest inhibitory effect on the growth of psychrotrophic aerobic bacteria during the first 3 days. Lactic acid bacteria levels of samples stored in MA conditions and in vacuo increased rapidly when compared to those levels of samples stored in air. It was also found that the effect of MA storage increased at 3±1°C.

Characterization of antibiotic resistance in Salmonella enterica isolates determined from ready-to-eat (RTE) salad vegetables

In the last decade, ready-to-eat (RTE) salad vegetables are gaining increasing importance in human diet. However, since they are consumed fresh, inadequate washing during processing can bring on some foodborne illnesses, like salmonellosis, since these food items have natural contamination from soil and water. During 2009–2010, a total of 81 samples were purchased arbitrarily from local markets in Ankara, and were examined for Salmonella contamination. Salmonella screening was performed by using anti-Salmonella magnetic beads system and polymerase chain reaction (PCR) identification of the suspected colonies. Then, the antibiotic resistance profiles of four Salmonella strains identified (strains RTE-1, RTE-2, RTE-3, and RTE-4) were also investigated, since the mechanism by which Salmonella spp. have accumulated antibiotic resistance genes is of interest. All strains showed resistance against sulfonamides (MIC > 128 mg/L). Further results suggested that associated sulfonamide resistance genes were encoded by the 55.0 kb plasmid of strain RTE-1 that involves no integrons. As a result of using two primers (P1254 and P1283) in randomly amplified polymorphic DNA-PCR (RAPD-PCR) analysis, two common amplicons (364 bp and 1065 bp) were determined. The findings of this study provide support to the adoption of guidelines for the prudent use of antibiotics in order to reduce the number of pathogens present on vegetable and fruit farms. Besides, since it is shown that these bacteria started to gain resistance to antibiotics, it is necessary to further investigate the prevalence of them in foods.

Food-Borne Microbial Diseases and Control: Food-Borne Infections and Intoxications

Food and water are excellent vehicles by which many bacterial, fungal, viral, and protozoal pathogens can reach a suitable colonization site in a new host. Although food manufacturing and production practices change, foods can be contaminated at any point in the farm to table continuum, even in consumers’ kitchens. Increased urbanization and travel contribute to an increase in large-scale production, wide distribution of food, and eating food prepared outside the home such as from street-food vendors or in small corner restaurants in which there is an inadequate application of good hygiene practices (GHP), and ultimately people being infected abroad possibly transmit the food-borne pathogen to the others at home. These circumstances cause an increased risk of food-borne microbial illnesses and also outbreaks. A change in the diet, as a result of international trade in food, and the increase in the number of people with a compromised immune system have also influenced the increase in food-borne microbial diseases. Centers for Disease Control and Prevention (CDC) reported 13,405 food-borne disease outbreaks, which resulted in 273,120 reported cases of illness, 9,109 hospitalizations, and 200 deaths between the years 1998 and 2008. Of the 7,998 outbreaks with a known etiology, 3,633 (45 %) were caused by viruses, 3,613 (45 %) were caused by bacteria, 685 (5 %) were caused by chemical and toxic agents, and 67 (1 %) were caused by parasites. Correspondingly, food-borne microbial diseases still represent an important global public health issue. Therefore, in this chapter we shall focus on bacterial, fungal, viral, and protozoal pathogens in the food chain and indicate their prevention and control ways throughout the food preparation process.

Antimicrobial effect of Helichrysum plicatum subsp. plicatum.

The objective of the present study was to investigate the in vitro antibacterial activity of the extracts and their fractions obtained from either the flowers or the leaves of Helichrysum plicatum DC. subsp. plicatum (Asteraceae), by studying inhibition of the growth of a dangerous food pathogen, Escherichia coli O157:H7. The antibacterial effects of the ethanol and water extracts of the flowers and leaves were examined first. Subsequently sub-extracts of the flower ethanol extract (FEE), which was found to be the most effective extract, were examined. As a result, the antibacterial effect of FEE was found to be stronger than that of the chloroform and ethyl acetate sub-extracts. This may due to synergistic activity of several components of the ethanol extract of the flowers.

Combined effect of gamma-irradiation and conventional cooking on Aeromonas hydrophila in meatball.

Irradiation combined with a conventional cooking procedure was applied to meatball and the effects on bacterial load and inoculatedAeromonas hydrophila were determined. Meatball samples were irradiated by using a60Co source at the dose levels of 0, 0.30,0.75,1.50,2.50 kGy and cold stored at 4±1°C for 7 days. Bacterial load and the count ofA. hydrophila decreased when the irradiation dose level increased. A minimum inhibition effect was found at the dose of 0.30 kGy. Irradiation in combination with a conventional cooking procedure was found to be more effective in reducingA. hydrophila and the bacterial load in meatball. This study indicated that a dose of 0.75 kGy was sufficient to destroy approximately 104 cfu/g ofA. hydrophila in meatball.

Microbiological Quality Systems and Microbial Risk Analysis

The consumer expects to receive safe foods that meet the expectations of quality. It is a shared responsibility of the food industry and the government to ensure that food provided to the consumer is safe and does not become a vehicle in a disease outbreak or in the transmission of communicable disease. Whereupon the food business is responsible for producing not only safe foods but also for demonstrating in a transparent modus that how food safety has been planned and implemented. This is done through the development of the food safety management systems (FSMS) which have been designed and established over the last four decades with several revisions. Hazard Analysis and Critical Control Point (HACCP) is a systematic approach seemed to be enough for the identification, evaluation, and control of hazards in food manufacturing and processing plants since it fits very well in the field of application of a specific quality assurance plan. However, it is observed that certifying it does not guarantee the optimum level of managing food safety hazards and consequently absolute food safety and the quality of the end product. The integration of HACCP with the development of dynamic risk assessment system, which is a top priority issue on the basic food legislation document, offers a means for considering the entire farm to fork spectrum and for relating food manufacturing and processing operations to public health objectives. It is so apparent that no food can be considered to be risk free and each step in the processing of food from farm to fork has a role in assuring its safety.