Omar B. Ahmed

Comparison of three DNA extraction methods for polymerase chain reaction (PCR) analysis of bacterial genomic DNA

Rapid isolation of high-purity microbial genomic DNA is necessary for genome analysis. In this study, the authors compared a one-hour procedure using a microwave with enzymatic and boiling methods of genomic DNA extraction from Gram-negative and Gram-positive bacteria. High DNA concentration and purity were observed for both MRSA and ESBL strains (80.1 and 91.1 µg/ml; OD260/280, 1.82 and 1.70, respectively) when the extraction protocol included microwave pre-heating. DNA quality was further confirmed by PCR detection of mecA and CTX-M. In conclusion, the microwave-based procedure was rapid, efficient, cost-effective, and applicable for both Gram-positive and Gram-negative bacteria. Key words: DNA, MRSA, ESBL, gene, enzymatic, boiling, microwave.

Detection of Salmonella in Food Samples by Culture and Polymerase ChainReaction Methods

Conventional culture methods for the isolation and identification of food borne bacterial pathogens are rather sensitive and quite inexpensive, but at the same time they are labor-intensive and time-consuming. Molecular techniques are more rapid and highly sensitive for identification of food pathogens. This study was carried out to evaluate a 12 hour PCR method for detection of Salmonella in food samples. The results showed that out of 150 food samples, 32 (21.3%) were positive by culture, 35 (23.3%) were positive by PCR, the sensitivity of PCR was 100% while specificity was 97.5%. The study concluded that the 6-h enrichment followed by PCR was rapid, simpler method that allowed the detection of Salmonella spp. within a maximum of 12 h.