www.scholarsresearchlibrary.com t Available online a Scholars Research Library Annals of Biological Research, 2010, 1 (4) : 145-147 (http://scholarsresearchlibrary.com/archive.html) ISSN 0976-1233 CODEN (USA): ABRNBW 145 Scholars Research Library Antimicrobial activity of nine medicinal plants growing in the south of Algeria Kendour Zaouia 1 , Ladjel Segni 1 , Gherraf Noureddine 2 , and Ouahrani Mohamed Redha 1 UKMO university Ouargla, Algeria Larbi ben M’hidi University, Oum El Bouaghi, Algeria ___________________________________________________________________________ ABSTRACT Methanolic and aqueous extracts of nine Algerian plant species used in folk medicine were investigated for their antimicrobial activities against five bacteria strains: Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Enterobacter aerogenes and one fungus: Candida albicans . The plants exhibited important antimicrobial activity with a significant difference between the different plants. The most active plants were Tamarix gallica, Rhetinolepis sp and Muscari Comosun. Most of the tested plant extracts were active against Candida albicans. Of all extracts, the Methanolic extract of Rhetinolepis sp was the most active (diameter ranges between 15mm and 22mm) whereas, the aqueous extract of Tamarix Gallica was the most active of all tested aqueous extracts (Diameter ranges between 10 mm and 17 mm). Keywords: Antibacterial activity; methanolic extract; aqueous extract ___________________________________________________________________________ INTRODUCTION The development of microbial resistance towards antibiotics makes it necessary to search for new potential effective compounds against pathogenic bacteria. There have been numerous broad based screening programmers initiated over the past years, in which large numbers of plant species have been evaluated for their antimicrobial activities [1-3]. In the constant effort to improve the efficacy and ethics of modern medical practice, researchers are increasingly turning their attention to folk medicine as a source of new drugs [4]. Nowadays, the development of resistance by a pathogen to many of the commonly used antibiotics provides an impetus for further attempts to search for new antimicrobial agents to combat infections and overcome the problems of resistance and side effects of the currently available antimicrobial agents. Hence, this in vitro study was aimed at screening selected Algerian medicinal plants for