Comparison of Polymerase Chain Reaction and Conventional Methods for Diagnosis of Listeria monocytogenes Isolated from Different Clinical Specimens and Food Stuffs

Background: Listeria monocytogenes has emerged as a significant food borne pathogen in recent decades. Polymerase chain reaction (PCR) is deemed to be more reliable than conventional methods of identification. This work aimed to evaluate the accuracy of PCR in comparison to conventional methods for the diagnosis of L. monocytegenes from different clinical specimens and food stuffs. Methods: This study was conducted on 66 clinical specimens and 100 different food stuffs. On the basis of colonial morphology, Gram's stain, catalase test, haemolysis on sheep blood agar, and motility test, Listeria isolates were further identified to species level by 10300 API Listeria strips. PCR was done directly for all specimens to evaluate its accuracy in comparison to conventional methods of diagnosis. Results: A total of 5 (7.6 %) same L. monocytogenes isolates were identified both by the conventional method and PCR in different clinical samples. However, PCR identified 6 (6 %) L. monocytogenes isolates from food stuffs versus 4 (4 %) isolates were identified by conventional methods. Conclusions: PCR is a rapid procedure with both sensitivity and specificity for quick detection and identification of L. monocytogenes either from clinical specimens or food stuffs. (Clin. Lab. 2011;57:919-924)