10.22376/ijpbs.2019.10.1.p1-12 Volume 11 Issue 4 2020 (October-December) The global health community is concerned about the rise and spread of antibiotic resistance and evolution of new strains of disease-causing agents. As a result of restricted access to proper medicine, in many developing countries, people are still using plants to treat the most prevalent infections. In this study, antimicrobial activities of methanol (75%), ethanol (95%) and aqueous extracts from leaves, raw fruit as well as ripe fruit of lessThan i greaterThan Psidium lessThan /i greaterThan lessThan i greaterThan guajava lessThan /i greaterThan extracts were investigated against lessThan i greaterThan Escherichia coli lessThan /i greaterThan MTCC45, lessThan i greaterThan Klebsiella pneumoniae lessThan /i greaterThan MTCC9544 and lessThan i greaterThan Bacillus subtilis lessThan /i greaterThan MTCC121. The antimicrobial activities of the extracts against bacteria were tested by using agar well diffusion and agar disc diffusion method. The ethanolic and methanolic extract of lessThan i greaterThan P. lessThan /i greaterThan lessThan i greaterThan guajava lessThan /i greaterThan leaves shows activity against lessThan i greaterThan K. pneumonia lessThan /i greaterThan lessThan i greaterThan ( lessThan /i greaterThan MIC= 25 mg/ml and 75 mg/ml respectively lessThan i greaterThan ) lessThan /i greaterThan . The methanolic and ethanolic extract of raw fruit shows activity against lessThan i greaterThan K. pneumonia lessThan /i greaterThan and lessThan i greaterThan E. coli lessThan /i greaterThan (MIC= 50 mg/ml and 75 mg/ml respectively). The aqueous, methanolic and ethanolic extract of ripe fruit shows a significant MIC value of 50 mg/ml, 25 mg/ml and 25 mg/ml respectively against lessThan i greaterThan E. coli lessThan /i greaterThan . The ethanolic extract of leaves and aqueous extract of ripe fruit shows activity against lessThan i greaterThan B. subtilis lessThan /i greaterThan (MIC= 50 mg/ml and 75 mg/ml respectively) lessThan i greaterThan . lessThan /i greaterThan The ethanolic and methanolic extracts showed higher antimicrobial activity as compared to aqueous extracts. The phytochemical analysis shows that various extracts from leaves, raw fruits and ripe fruits of lessThan i greaterThan P. lessThan /i greaterThan lessThan i greaterThan guajava lessThan /i greaterThan contains tannin, phlobatannins, saponins, terpenoids , flavonoids, polyphenols, reducing sugar and alkaloid. Results from the present study showed that lessThan i greaterThan P. lessThan /i greaterThan lessThan i greaterThan guajava lessThan /i greaterThan extracts possess potent antibacterial activity against pathogenic microbes such as lessThan i greaterThan B. subtilis lessThan /i greaterThan , lessThan i greaterThan K. pneumonia lessThan /i greaterThan and lessThan i greaterThan E. coli. lessThan /i greaterThan These extracts can become good sources for isolation and purification of natural antibiotic compounds and hence may yield natural alternative therapeutics. Saraswati Gupta, Nirali Budhbhatti, Rohini Keshava* Psidium guajava, Ripe fruit, Raw fruit, Antimicrobial, Phytochemical study 162-167