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ABSTRACT Background and Aim: Salmonella enterica subspecies enterica serotype enteritidis is one of the most frequent serotypes that cause gastroenteritis and bacteremia in human. The aim of the present study was to study the molecular types of Salmonella enteritidis strains isolated from different laboratory centers in Tehran by ERIC-PCR. Materials and methods: In this descriptive study from April 2008 to December 2011, Salmonella isolates were obtained from the patients admitted to several hospitals in Tehran. Salmonella isolates were identified by the standard microbiological methods and were serotyped by slide agglutination with commercial mono and polyvalent antisera. Molecular typing of the strains and their genetic relationship were investigated by using ERIC-PCR. Results: All Salmonella enteritidis strains investigated by ERIC-PCR were type able. This technique produced 6 to 17 amplified DNA bands with 200 to 3200 different bp. In general, ERIC-PCR differentiated all Salmonella enterica serotype enteritidis isolates into nine distinct clusters (E1-E9), however the majority of the strains (35%) belonged to cluster E1. Conclusion: In this study the most common serotype was Salmonella enteritidis and ERIC-PCR showed that the strains belonged to diverse genotypic clusters. Conflict of Interest: Nil Received: Feb8, 2012 Accepted: Mar11, 2013

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Background and Aim: There are several methods for genotyping single nucleotide polymorphisms (SNPs). Polymerase chain reaction with confronting two-pair primers (PCR-CTPP) is an inexpensive, quick, reliable, time saving and cost effective method that is applicable for SNPs genotyping compared to other related methods. In the PCR-CTPP technique, allele-specific products of the genes are selectively amplified by adding two pairs of four primers and ordinarily prepared PCR mixture in a single PCR tube. Four allele-specific primers are F1 (sense) and R1 (antisense) primers for one allele that R1 has an anti-sense nucleotide at the 3′ end and F2 (sense) and R2 (antisense) for the other allele that F2 has a sense nucleotide at the 3′ end. PCR-CTPP produces three products with different sizes which can make possible genotyping of SNP by gel electrophoresis. To increase the reproducibility and accuracy of the PCR-CTPP results, it is better to optimize protocol before sample genotyping. The aim of this study was to review the currently used strategies for optimum application and determination of advantages and disadvantages of the PCR-CTPP method in SNPs genotyping.
 Materials and Methods: The articles related to the PCR-CTPP method were searched from databases such as ISI Web of science, Science direct, Pubmed, Google Scholar, SID, and Scopus.
Results: For more efficiency and reproducibility of the PCR-CTPP method, we should consider the specificity and similarity of melting temperatures of the designed primers by using algorithms  and specific primer design softwares.
Conclusion: Strategies for optimizing the concentration ratio of internal and external primers, adding amplification additives to the PCR reaction mix, and use of the touchdown program are also recommended.