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Background and Aims: Many bacteria including Escherichia coli may enter into a viable but non-culturable (VBNC) state under unfavorable stresses, which are unable to be detected by culture-based methods. In this study, the use of Reverse Transcription PCR (RT-PCR) for detection of VBNC state of E. coli O157:H7 was investigated. Materials and Methods: Escherichia coli O157:H7 was inoculated in distilled water and 30 percent salt water at room temperature. The cultivability of bacteria was determined using routine culture and colony counting on MacConkey agar. The RT-PCR of 16S rRNA gene involved direct extraction and purification of RNA, DNase I treatment for removing DNA contamination, cDNA synthesis and electrophoresis of PCR products of cDNA was used to detect viable E. coli O157:H7 under studied treatments and was compared with the results of RT-PCR of 16S rRNA gene of heat- killed bacteria. Results: The cultivability of bacteria was maintained during the study period in distilled water; however, the use of 30% NaCl caused the bacteria to be non-cultivable on day 4. The RTPCR of 16S rRNA showed the positive expression of this gene in cultivable and non-cultivable bacteria during the study period, whereas heat-killed bacteria were negative for this gene, which indicated the efficacy of RT-PCR of 16S rRNA in differentiation of alive from dead bacteria. Conclusions: Escherichia coli O157:H7 entered into the VBNC under 30 percent NaCl which can be associated with serious human health problems. RT-PCR can be used to detect bacteria in the VBNC state. [ABSTRACT FROM AUTHOR]

Background and Aims: Brucellosis is an infectious zoonotic disease responsible for reproductive disorders among animals and significant economic losses to the meat and milk supplychain. The purpose of this study was therefore to evaluate and diagnose the species and strains of Brucella isolates among cattles via multiplex polymerase chain reaction. Materials and Methods: In this study, blood samples were taken from 22 cows diagnosed as having brucellosis by PCR test. Blood samples were cultured in BACTEC vials and incubated at 37 degrees Celsius for 5 days following which each sample was cultured on Brucella agar and kept for 3 days under Co2 condition.The 16SrRNA gene was used as the target for the detection of Brucella genus and the bcsp31 gene was used for the detection of Brucella biovars. The PCR products were electrophoresed on %1 agarose and compared with standard strains. Results: The PCR results showed a total of 22 positive samples for Brucella among cattles. Out of the 22 cattle positive samples, 19 were identified as B.abortus (biovars 1, 2, 3, 4, 5) and 3 as B. melitensis (biovars 1, 2, 3). Conclusions: Brucella abortus biovars 1 and 3 and B .melitensis biovar 1 are the most prevalent biovars among cattles in Lorestan province, Iran. Moreover, multiplex PCR method could be used to improve the qualitative level and the Brucella diagnosis speed in laboratories. [ABSTRACT FROM AUTHOR]