Survival of Acid Adapted Escherichia coli O157:H7 in Some Acidic Foods (in English)

Abstract

This study examined the effect of adaptation to acid on the survival of Escherichia coli O157:H7 in Ayran, turnip juice, apple juice and orange juice.E. coli O157:H7 was adapted to acid at pH 4.5 in tryptic soy broth (TSB) for 2 h. Commercial products of Ayran (pH 3.95), turnip juice (pH 3.6), orange juice (pH 3.0) and apple juice (pH 3.3) were inoculated with acid adapted or nonadapted cells of E. coli O157:H7. Survival of the inoculated E. coli O157:H7 in these commercial food products during storage periods was examined. Orange juice, apple juice and turnip juice were stored at 4 °C or 20 °C. Ayran was stored at 4 °C. In general, low temperature enhanced the survival of E. coli O157:H7 in the commercial juices tested (p<0.05). Acid adaptation enhanced the survival of E. coli O157:H7 in turnip juice and apple juice stored at 4°C. It was found that survival of the acid adapted and nonadapted E. coli O157:H7 in orange juice during storage at 4 °C or 20 °C and Ayran during storage at 4 °C did not show any significant differences (p<0.05). This study showed that adaptation to acid might increase survival of E. coli O157:H7 in some acidic foods. Therefore acid adaptation is an important mechanism in E. coli O157:H7 and should be considered in food challenges studies.

Keywords

• E. coli O157:H7, acidic foods, acid adaptation.   

Aside Adapte Edilen Escherichia coli O157:H7'nin Bazı Asidik Gıdalardaki Canlılığı (İngilizce)

Abstract

Bu çalışmada Escherichia coli O157:H7'ninaside adaptasyonunun Ayran, şalgam suyu, elma suyu ve portakal suyundaki canlılığına etkisi araştırılmıştır.Escherichia coli O157:H7 pH 4,5'te Tryptic Soy Broth besiyerinde 2 saat tutularak aside adapte edilmiştir. Ticari olarak satılan Ayran (pH 3,95), şalgam suyu (pH 3,6), portakal suyu (pH 3,0) ve elma suyu (pH 3,3) aside adapte edilen ve edilmeyen Escherichia coli O157:H7 kültürü ile inoküle edilmiştir. Bu ürünlerde inkübasyon süresince Escherichia coli O157:H7'nin canlılığı saptanmıştır. Elma, portakal ve şalgam suyu 4 °C ve 20 °C'de depolanırken Ayran yalnızca 4 °C'de depolanmıştır. Genel olarak aside adaptasyondan bağımsız olarak düşük sıcaklık, test edilen tüm örneklerde Escherichia coli O157:H7'nin canlılığını artırmıştır. Aside adaptasyon 4 °C'de depolanan şalgam suyunda Escherichia coli O157:H7'nin canlılığını artırmıştır (p<0,05). Ayrıca aside adaptasyon 4 °C'de depolanan elma suyunda da Escherichia coli O157:H7'nin canlılığını artırmıştır ancak bu etki istatistiksel olarak önemli bulunmamıştır (p<0,05). 4 °C ve 20 °C'de depolanan portakal suyu ve 4 °C'de depolanan elma suyunda ise aside adapte edilen ve edilmeyen Escherichia coli O157:H7 kültürlerinin canlılıkları arasında önemli bir fark tespit edilememiştir. Bu çalışma Escherichia coli O157:H7'nin asidik gıdalarda uzun süre canlı kalabileceğini ve aside adaptasyonun bazı asidik gıdalarda bu patojenin canlılığını artırdığını göstermiştir. Sonuç olarak aside adaptasyon Escherichia coli O157:H7'nin asidik gıdalarda canlı kalmasını sağlayan önemli bir mekanizma olup gıda güvenliği çalışmalarında mutlaka göz önüne alınmalıdır.

Keywords

• E. coli O157:H7, asidik gıdalar, aside adaptasyon.

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