Research Article An Evaluation of the Antibacterial Properties of Tormentic Acid Congener and Extracts From Callistemon viminalis on Selected ESKAPE Pathogens and Effects on Biofilm Formation Tafadzwa Chipenzi, 1 Genuine Baloyi, 1 Tatenda Mudondo, 1 Simbarashe Sithole , 2 Godloves Fru Chi, 3 and Stanley Mukanganyama 2 1 School of Pharmacy, College of Health Sciences, University of Zimbabwe, Mt. Pleasant, Harare, Zimbabwe 2 Department of Biochemistry, University of Zimbabwe, Mt. Pleasant, Harare, Zimbabwe 3 University of YAOUNDE 1, P.O. Box 812, Yaound´ e, Cameroon Correspondence should be addressed to Stanley Mukanganyama; smukanganyama01@gmail.com Received 15 August 2020; Revised 26 October 2020; Accepted 28 October 2020; Published 9 November 2020 Academic Editor: Heng Yen Khong Copyright © 2020 Tafadzwa Chipenzi et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ESKAPE pathogens, namely, Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species, are responsible for a majority of all healthcare-acquired infections (HAI). e bacteria cause nosocomial infections in immunocompromised patients. Extracts from Callistemonviminalis have been shown to have antibacterial, antifungal, and anti-inflammatory activities. Tormentic acid congener, a pentacyclic triterpene saponin, was isolated from C. viminalis leaves. is study aimed to investigate the antibacterial effects of tormentic acid congener and leaf extracts on biofilm formation by A. baumannii, S. aureus, S. pyogenes, and P. aeruginosa. e antibacterial effects were determined by the microbroth dilution method, and ciprofloxacin was used as the standard antibacterial drug. Biofilm formation and detachment assays were performed using crystal violet staining. Production of extracellular polymeric DNA and polysaccharides from biofilms was also determined. Tormentic acid congener showed time-dependent antibacterial activity against P. aeruginosa with a MIC of 100 µg/ml and caused significant protein leakage. Antibacterial activity was found when tormentic acid congener was tested against both S. aureus and P. aeruginosa. e MICs were found to be 25 µg/ml and 12.5 µg/ml for P. aeruginosa and S. aureus cells, respectively. S. pyogenes was found to be susceptible to tormentic acid congener and the hydroethanolic extract with an MIC of 100 µg/ml and 25 µg/ml, respectively. A. baumannii was found not to be susceptible to the compound or the extracts. e compound and the extracts caused a significant decrease in the biofilm extracellular polysaccharide content of S. pyogenes. e extracts and tormentic acid congener caused detachment of biofilms and decreased the release of extracellular DNA and capsular polysaccharides from biofilms of P. aeruginosa and S. aureus. Tormentic acid congener and extracts, thus, have significant antibacterial and antibiofilm activities on these selected ESKAPE bacteria and can act as source lead compounds for the development of antibacterial triterpenoids. 1. Introduction ESKAPE pathogens are responsible for two-thirds of all healthcare-associated infections [1]. e Infectious Dis- eases Society of America (ISDA) formulated an acronym ESKAPE to emphasize the group of pathogens that cause hospital infections and effectively “escape” the effects of antibacterial drugs [2]. Gram-positive pathogens, vanco- mycin-resistant enterococci (VRE) and methicillin- resistant Staphylococcus aureus (MRSA), and Gram-neg- ative pathogens, Pseudomonas aeruginosa and Acineto- bacter baumannii as well as extended spectrum-lactamase producing (RSBL) or carbapenem-resistant Enter- obacteriaceae (CRE) were used [2]. Approximately 10–15% of the nosocomial infections on a worldwide scale are caused by P. aeruginosa [3]. Nosocomial infections are responsible for hospital-acquired infections largely in immunocompromised patients [4]. Hindawi Advances in Pharmacological and Pharmaceutical Sciences Volume 2020, Article ID 8848606, 14 pages https://doi.org/10.1155/2020/8848606