SACM - United States of America
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Item Restricted THE ANTIM ICROBIAL ACTIVITY OF COMMIPHORA MOLM OL (MYRRHA) EXTRACT(Long Island University, 0019-07-15) Alenezi, Tahrir; Bhattacharjee, MrinalThe Commiphoramolmol (myrrha) has been used as a traditional medicine for centuries in different cultures. An ethanol extract o f myrrha was evaporated under vacuum to obtain an oil. A 20% solution o f this oil in ethanol was used to determine antimicrobial activity against the Gram-positive bacteria S. aureus, the Gram-negative bacteria, E. coli, MVlONal, and fungi, (yeast), Saccharomyces cerevisiae. The MIC forÆ’. coli and S. aureus were determined on phosphate buffer since the oil did not show antibiotic activity on growing cells. The MIC o f myrrha oil in phosphate buffer for E. coli was 0.56% (5.6 mg/ml) and for S. aureus was 0.1% (1 mg/ml). However, the oil could be used to kill cells in a nutrient-rich medium provided growth o f the bacteria is first stopped using a bacteriostatic antibiotic such as Chloramphenicol. The results show that chloramphenicol enhanced the antimicrobial activity o f myrrha oil. Zone o f inhibition test shows myrrha extract has antibacterial property against S. aureus. Furthermore, the antifungal activity of myrrha extract was prodigious since most o f the cells were killed in 10 minutes at a dose o f 0.05% (0.5 mg/ml) o f myrrha extract. Repeated attempts to obtain an E. coli or S. aureus strain that is resistant to myrrha oil were unsuccessful. A possible explanation o f this can be that myrrha oil is a membrane acting antibiotic. In conclusion, the results o f this study suggest that myrrha extract could be a prom ising antibacterial and antifungal drug.39 0Item Restricted Identification of Antimicrobial Peptides against Gram-negative Bacteria(Saudi Digital Library, 2023-12-20) Alsaab, Fahad; Van Hoek, MoniqueAntibiotic resistance in bacteria has been rising due to excessive and improper use of antibiotics. There is a pressing need to find alternative approaches to tackle this issue. Unconventional antimicrobials have been proposed to combat multidrug resistant (MDR) bacteria. Antimicrobial peptides (AMPs) are promising compounds for fighting bacterial infections. AMPs are a cationic polypeptide chain that can target microorganisms, including bacteria. In this work, three approaches of peptide design have been implemented to generate novel peptides with a focus on gram-negative bacteria. Computational-aided positional analysis method was utilized to generate peptides based on pre-existing dataset of Acinetobacter (A.) baumannii-active peptides to target multidrug resistant (MDR) A. baumannii. The output resulted in the generation of five peptides, HRZN-13 to -17. HRZN-15 peptide had the strongest antibacterial and antibiofilm activity against MDR A. baumannii among HRZN peptides. However, it was toxic to human red blood cells (RBCs) and Galleria mellonella (waxworms). Rational design created a novel sequence GATR-3 from a cryptic peptide that was isolated from American alligator, which we characterized in this study against A. baumannii. GATR-3 exhibited potent antimicrobial activity against a panel of MDR A. baumannii strains. The most exciting finding was that it inhibited biofilm formation as well as eradicated preformed biofilm in this wound-infecting pathogen. GATR-3 did not cause toxicity in hepatocytes, human RBCs and G. mellonella. It also demonstrated host-directed activity, inducing migration of macrophages. The third method that was employed in this study is chemical modification of naturally occurring peptides. The human cathelicidin LL-37 peptide was dissected to find smaller fragments that have antibiofilm activity against Francisella novicida. KR-12 was the smallest fragment tested that exhibited antibiofilm activity but failed to inhibit growth of F. novicida, indicating it’s antibiofilm activity. Therefore, chemical staples were introduced on KR-12 and KR-16 fragments to support their secondary structure conformations and potentially increase their stability or activity. Stapled peptides successfully demonstrated improved growth-inhibitory effect of F. novicida, compared to the native peptides, with minimal toxicity towards human RBCs. All the peptide design methods presented in this dissertation led to the production of novel peptides with activity against gram-negative bacteria.52 0