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

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