Molecular detection of staphylococcus aureus and escherichia coli contamination in a select sample of herbal medicines sold in Kampala.

Abstract

Introduction Herbal medicines are used by a large portion of the world population for their primary health care. Currently, pharmacopoeia culture and biochemical methods for regulation of HM have been adapted across the world. These methods have several shortcomings such as having low sensitivity and being time-consuming. This creates a need to develop molecular techniques for detecting of contamination in HM which have proved to be quicker, more sensitive and less labour intensive; such as the Polymerase Chain Reaction (PCR). The objective of this study was to develop and optimise a PCR based method for the detection of S. aureus and E. coli in a select sample of HM sold in Kampala and to compare the effectiveness of such a method with the standard culture and biochemical methods used. Methods Species specific primers targeting nucA and uidA genes for S. aureus and E. coli respectively were designed. PCR was then optimised using DNA extracted from the pure cultures of S. aureus and E. coli. The optimal conditions obtained were thereafter used to run PCR with the DNA extracted from the HM samples. Samples were subjected to culture and biochemical methods in order to detect presence of the S. aureus and E. coli for comparison with the PCR technique. Results The PCR based method identified E. coli from 2 out of 10 HM samples. Culture and biochemical methods identified E. coli from 1 out of 10 HM samples. S. aureus was not identified from the samples using both methods. Conclusion Optimal amplification of nucA and uidA genes was done at an annealing temperature of 54oC for 30 seconds, an extension temperature of 72oC for 13 and 33 seconds for nucA and uidA gene respectively. The PCR based method is equally as effective as standard culture and biochemical methods in detecting S. aureus and E. coli or even better, however the later cannot be concluded upon unless reverse transcriptase PCR is done.