Abdullah Dikici

Antimicrobial resistance of emerging foodborne pathogens: Status quo and global trends

Emerging foodborne pathogens are challenging subjects of food microbiology with their antibiotic resistance and their impact on public health. Campylobacter jejuni, Salmonella spp. and Verotoxigenic Escherichia coli (VTEC) are significant emerging food pathogens, globally. The decrease in supply and increase in demand lead developed countries to produce animal products with a higher efficiency. The massive production has caused the increase of the significant foodborne diseases. The strict control of food starting from farm to fork has been held by different regulations. Official measures have been applied to combat these pathogens. In 2005 EU declared that, an EU-wide ban on the use of antibiotics as growth promoters in animal feed would be applied on 1 January 2006. The ban is the final step in the phasing out of antibiotics used for non-medical purposes. It is a part of the Commission’s strategy to tackle the emergence of bacteria and other microbes resistant to antibiotics, due to their overexploitation or misuse. As the awareness raises more countries banned application of antibiotics as growth promoter, but the resistance of the emerging foodborne pathogens do not represent decrease. Currently, the main concern of food safety is counter measures against resistant bugs.

Survival of Listeria monocytogenes during Production and ripening of traditional Turkish Savak tulum cheese and in synthetic gastric fluid.

This study investigated the survival and acid tolerance of Listeria monocytogenes during the 2-day processing stage and 90-day ripening of Savak tulum cheese, a traditional cheese in Turkey. Experimental Savak tulum cheese was produced from raw sheeps milk that was inoculated with a L. monocytogenes mixture consisting of five strains (average 7.0 log CFU/ml) and was ripened at 6°C for 90 days. Microbiological and chemical analyses and acid exposure experiments in synthetic gastric fluid (SGF) (pH 1.5 to 2.5) were carried out on days 1 and 2 during processing and on days 0, 15, 30, 45, 60, and 90 during ripening. The numbers of L. monocytogenes did not decrease during processing, but a total of 4.1 log CFU/g reduction was observed during ripening. Throughout the ripening period, L. monocytogenes cells survived direct 90-min exposures of the cheese samples to SGF. These results suggest that, although the pathogen numbers decreased in Savak tulum cheese ripened at 6°C for 90 days, a sublethal environment may have occurred in the cheese during the production stage, activating the acid-tolerance mechanisms of the pathogen and allowing L. monocytogenes to maintain its viability in the SGF for 90 min.

Effect of Nisin and Gamma Irradiation Treatments on Listeria monocytogenes on Some High Economic Valued Aquaculture Products

Küresel tüketimde balık ve diğer su ürünleri önemli rol oynamaktadır. Deniz ürünleri diğer ürünlerle kıyasla daha fazla Listeria monocytogenes kontaminasyonu riski taşımaktadır. L. monocytogenes riski belirli üretim yöntemleri ile düşürülmelidir. Çeşitli çalışmalar Nisin uygulamasının tek veya kombine olarak farklı koşullardaki farklı gıdalarda etkili olduğunu göstermiştir. Bunlara ek olarak, gama ışınlama su ürünlerinde raf ömrünün uzatılması ve patojenlerin dekontaminasyonu için belirgin bir potansiyele sahiptir. Farklı dört adet ekonomik değeri yüksek ürüne gama ışınlaması Nisin içerecek veya içermeyecek şekilde uygulandı. Sonuçlara göre Nisin uygulanmamış gruplarda L. monocytogenes 5 kGy ışın dozu ile eradike edilebilirken, Nisin kombinasyonu uygulanması gereken dozu 3 kGy seviyesine çekmiştir. Buna bağlı olarak farklı su ürünlerinde, Nisin ve ışınlama kombinasyonlarının L. monocytogenes kontaminasyonunun giderilmesinde beraber uygulanmasının verimli olacağı düşünülmüştür.

Effect of cooking procedures of kiymali pide, a traditional Turkish fast-food, on destruction of Escherichia coli O157:H7

The objective of the present study was to obtain data about cooking time and temperature of kiymali pide in the restaurants and to investigate thermal inactivation of E. coli O157:H7 during experimental kiymali pide making. A field study was conducted in randomly selected 23 of 87 pide restaurants. Processing parameters including oven temperature, cooking period and post-cooking temperature were determined. Kiymali pide samples were prepared using ground beef filling experimentally inoculated with E. coli O157:H7 (7.6 log10 CFU/g). Pide samples were cooked at a conventional oven at 180 °C for 180, 240, 270, 300 and 330 s. Results of the current study suggest that cooking kiymali pide at 180 °C for at least 330 s (5.5 min) may provide sufficient food safety assurance (≥6 log10 CFU/g) for E. coli O157:H7.