Saudi Cultural Missions Theses & Dissertations
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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.33 0Item Restricted Exploring diagnostic approaches and quality assurance data for improved management of gonorrhoea antimicrobial resistance(The University of Queensland, 2023-05-03) Alharbi, Bushra; Trembizki, Ella; Whiley, David; Sweeney, Emma; Lord, MaggyNeisseria gonorrhoeae (NG), the etiological agent of gonorrhoea, accounts for 82 million cases among the 374 million new sexually transmitted infections recorded in 2020. NG is associated with high rates of antimicrobial resistance (AMR), with the World Health Organization designating it as an urgent AMR threat. There are several important factors when it comes to the ideal management of NG. One important approach to NG management entails enhancing AMR surveillance capabilities. Another involves applying accurate and specific diagnostics to detect both NG and related AMR genes/mutations directly from clinical samples, which can then guide treatment and/or inform surveillance. To effectively enhance surveillance of NG and associated AMR, it is crucial to comprehensively understand the factors that influence NG’s infection rates, distribution, and prevalence throughout geographic regions. Such knowledge contributes to effective public health interventions. Among the various public health concerns relevant to NG, COVID-19 has been a significant recent event to indirectly impact NG prevalence and transmission. Consequently, this thesis included an examination of the impact of COVID-19-related public health measures on the prevalence of NG and the distribution of NG genotypes among the population of Queensland (QLD) during the first half of 2020 (Chapter 2). The results of this chapter showed that there is a decrease in NG genotypic diversity post COVID-19 in 2020 in QLD, and the proportion of the isolates carrying an azithromycin AMR specific determinant have almost doubled post COVID-19. In Australia, NG treatment guidelines in most settings indicate 500 mg of ceftriaxone intramuscularly and 1 g of azithromycin orally to be the standard of care. However, the increase in azithromycin resistance has prompted a re-evaluation of this therapy regimen elsewhere, with 1 g of azithromycin no longer being recommended as a first-line therapy in many countries worldwide. This shift emphasises the importance of further understanding the spread of azithromycin resistance in Australia to inform its use as a first-line therapy. To do so, complementing culture-based surveillance by directly applying molecular AMR tests on clinical samples is required. As NG is known to constantly evolve, target testing variations may arise. It is therefore important to ascertain which genes and mutations are most prevalent and informative of azithromycin AMR. Accordingly, as part of this study (Chapter 3), the Pathogen-Watch online genomic database was explored to determine the prevalence of mutations known to be associated with azithromycin resistance within the global collection of NG isolate sequences. These outcomes then informed which diagnostic targets are most relevant when it comes to molecular assay targets; the meningococcal-mtrR and 23S-rRNA were found most significant. Following the above, real-time polymerase chain reaction (PCR) assays were developed and applied on NG-nucleic acid amplification test (NAAT)-positive clinical samples to enhance culture-based surveillance and better elucidate the distribution and prevalence of azithromycin resistance in QLD (Chapter 4). The results of this chapter indicated that there is a reduction in 23S rRNA determinants, while an increase the prevalence of meningococcal-mtrR harbouring strains (reinforcing Chapter 2 isolate data post COVID-19) which could put azithromycin treatment at risk in QLD. Molecular assay design complexities arose due to cross-reactivity with commensal Neisseria species, particularly for pharyngeal clinical samples. As routine molecular NG-AMR testing is on the horizon, I explored potential testing bias that may arise if patient pharyngeal clinical samples are excluded from the testing algorithm (Chapter 5). The results of this chapter suggested that excluding pharyngeal samples from N. gonorrhoeae AMR molecular testing in QLD will be of minimal impact with a loss of 13.17% of samples with the majority of infections appearing in two or more anatomical sites, therefore mostly accounted for. Finally, rapid and cost-effective diagnosis of both NG and AMR represents an important measure for controlling and managing gonococcal infection. Diagnostic tools such as PCR and culture require access to laboratory facilities and are associated with high costs and expertise, unfeasible in resource-poor settings with syndromic patient management. Therefore, alternative cost-effective diagnostic tools are urgently required. To further explore the latter as well as attempt to resolve commensal Neisseria cross-reactivity, I investigated the utility and feasibility of near-infrared spectroscopy (NIRS), for the identification and differentiation of NG from commensal Neisseria and detection of AMR (Chapter 6). This proof-of-concept study demonstrated the capability of the NIRS to distinguish N. gonorrhoeae from Neisseria commensals with accuracy of 98% for N. gonorrhoeae and 96% for commensals. Further, N. gonorrhoeae fully-susceptible strains were distinguished from resistant strains with an accuracy of 86% and 90%, respectively. The data from this work reinforces how molecular methods enable to enhance culture-based surveillance in QLD to capture less represented regions and populations. Importantly, this data demonstrated that azithromycin use as a blanket therapy for NG in QLD may be undermined due to a significant increase of AMR determinants in local NG. The exclusion of pharyngeal samples from molecular AMR testing is unlikely to affect the representativeness of AMR in our population, yet this needs to be carefully monitored. The exploration of NIRS technology as an alternative test for NG and AMR detection is feasible, yet further validations are required. This body of work represents better understanding of the spread of NG-AMR in QLD and further informing potential gaps when rolling out molecular AMR testing in our population. Finally, paving the way for the development of alternative, rapid and cost-effective diagnostics to be further explored.43 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.51 0Item Restricted The antibacterial efficacy of isolated bacteriophages against periodontal biofilms: A systematic review of in vitro studies(Saudi Digital Library, 2023-08-07) Binsaif, Nasser; Ramage, GordonBackground and aim: Periodontitis is a widespread, irreversible disease that threatens the oral health and quality of life of adult individuals. Antibiotics have been used to systemically treat periodontitis in combination with mechanical therapy, but they are increasingly resisted by the human microbiome. Phage therapy has been proposed to exhibit antibacterial activity, consequently, replace the use of antibiotic drugs. This study aimed to identify and summarise the current in vitro evidence of phage therapy’s effectiveness against periodontal biofilm. Methods: The PubMed, Web of Science, and Ovid (Embase) databases were searched to identify in vitro literature that investigated phage therapy as a treatment for periodontal biofilm using search terms referring to periodontal biofilm and bacteriophages. The literature was screened by reading the titles and abstracts to identify studies to be read fully, and inclusion and exclusion criteria were also applied. Thereafter, the included studies were processed to extract relevant study characteristics and general outcomes before performing quality assessments. Results: Ten publications were found to meet the inclusion criteria. All of these studies indicated that bacteriophages exhibited significant antibacterial activity against monospecies biofilms comprised of the micro-organisms F. nucleatum, E. faecalis, S. mutans, or A. actinomycetemcomitans. Regarding bacteriophage resistance, only one study reported resistance of E. faecalis biofilm after 24 hours, and the remaining studies did not report resistance activity. Discussion and conclusion: Recent in vitro studies suggest the use of phage therapy as a novel systemic periodontal treatment. However, a specific phage for use against P. gingivalis remains undetected. Moreover, the antibacterial efficacy of phage therapy against complex periodontal biofilms is still unclear.70 0