_____________________________________________________________________________________________________ *Corresponding author: E-mail: alimuhd4real@gmail.com; Journal of Advances in Medical and Pharmaceutical Sciences 12(3): 1-7, 2017; Article no.JAMPS.31126 ISSN: 2394-1111 SCIENCEDOMAIN international www.sciencedomain.org In-vitro Antibacterial Activity and Phytochemical Screening of Psidium guajava on Some Enteric Bacterial Isolates of Public Health Importance M. Ali 1* , A. Yahaya 2 , A. U. Zage 1 and Z. M. Yusuf 1 1 Department of Microbiology, Kano University of Science and Technology, Wudil, Kano State, Nigeria. 2 Department of Biological Science, Kano University of Science and Technology, Wudil, Kano State, Nigeria. Authors’ contributions This work was carried out in collaboration between all the authors. Authors MA and AY designed the research. Conduct of the experiment and writing of the script was done by all the authors. All authors read and approved the final manuscript. Article Information DOI: 10.9734/JAMPS/2017/31126 Editor(s): (1) Palmiro Poltronieri, National Research Council of Italy, CNR-ISPA, Italy and Institute of Sciences of Food Productions, Operative Unit in Lecce, Italy. (2) Jinyong Peng, College of Pharmacy, Dalian Medical University, Dalian, China. Reviewers: (1) P. Ghosh, North Bengal University, India. (2) Charu Gupta, Amity University UP, India. (3) Monthon Lertcanawanichakul, Walailak University, Thailand. Complete Peer review History: http://www.sciencedomain.org/review-history/18334 Received 21 st December 2016 Accepted 25 th January 2017 Published 24 th March 2017 ABSTRACT Aim: The study was conducted to investigate the antibacterial activity of Psidium guajava and its major antibacterial constituents (Phytochemicals). Materials and Methods: The aqueous and ethanol extracts from the leaves and stem bark of the plant was tested using well diffusion method for their antibacterial activity against some members Enterobacteriaceae family isolated from diarrheic stool sample (Escherichia coli, Shigella spp, Salmonella typhi and Pseudomonas aeruginosa). Results: The result shows that the extracts were active against the microorganisms. The ethanolic extract of stem bark showed the highest zones of inhibition against tested organisms compared to aqueous extract. Statistical analysis of the result shows that the extracts demonstrated higher antibacterial activity against the isolates tested with the average zone of inhibition of 15.44 mm, Original Research Article