Comparison of real-time PCR and conventional cultural methods to detect Escherichia coli O157:H7 in spices in Turkey

Year 2012, Volume: 71 Issue: 2, 113 - 120, 25.12.2012

Asli Ozkizilcik , Mustafa Ates Burcu Cerci

Abstract

In this study, 66 different spice samples were analyzed in order to compare Real-Time PCR and conventional
cultural methods for the detection of E. coli O157:H7 in spices. Thus, 66 different spice samples
(raw materials) were collected from various places in Izmir, Turkey. Conventional cultural methods
included pre-enrichment step, selection step and confirmation step. The molecular method included
two steps: pre-enrichment and Real-Time PCR step. Beside these methods, total aerobic mesophilic
bacteria, coliform, fecal coliform in samples, were also counted and the presence of Salmonella sp.
was investigated in order to determine total microbial load in samples. The results showed that aerobic
mesophilic bacteria counts were 5.1x103 -2.0x108 CFU/g, coliform counts were 8.0 x 102 CFU/g for the
average values of all samples. Salmonella sp. was not found in any of the samples.In four samples E.
coli O157:H7 positive by Real-Time PCR were found while all of the samples were negative by cultural
methods. We observed that the results of Real-Time PCR were more reliable than conventional methods.
Furthermore, the results were obtained in only 20 hours by Real-Time PCR method whereas conventional
cultural method was completed in 4 days.
Keywords: Cultural method, E. coli O157:H7, real-time PCR, spice

Keywords

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Türkiye’de baharatlarda Escherichia coli O157:H7’nin belirlenmesinde real-time PCR ve konvansiyonel kültürel yöntemin karşılaştırılması

Abstract

Bu çalışmada, baharatlarda E. coli O157:H7’nin belirlenmesinde Real-Time PCR ve kültürel yöntemlerinin karşılaştırılması için 66 farklı baharat örneği analiz edilmiştir. Bunun için 66 farklı baharat örneği (ham madde) İzmir’in çeşitli yerlerinden temin edilmiştir. Örneklerdeki toplam mikrobiyal yükün belirlenmesi için E. coli O157:H7 yanında toplam aerobik mezofilik bakteri, koliform, fekal koliform sayımları yapılmıştır ve Salmonella sp. varlığına bakılmıştır. Bütün örneklerde ortalama değerler aerobik mezofilik bakteri sayımı 5.1x103 -2.0x108 CFU/g ve koliform sayımı 8.0 x 102 CFU/g olarak bulunmuştur. Hiçbir örnekte Salmonella sp. bulunmamıştır. Kültürel yöntemle bütün örnekler E. coli O157:H7 bakımından negatif bulunurken Real-Time PCR yöntemiyle 4 tane örnek pozitif bulunmuştur. Bu çalışmada RealTime PCR yönteminin kültürel yönteme göre daha güvenilir olduğu gözlenmiştir. Bunun yanında kültürel yöntemle sonuç 4 günde alınırken Real-Time PCR yöntemiyle sadece 20 saatte sonuç alınmıştır

Keywords

Kültürel yöntem, E. coli O157:H7, real-time PCR, baharat

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