Research Articles (Medical Bioscience)

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Biosynthesis, Characterization, and Biological Activities of Procyanidin Capped Silver Nanoparticles
(Multidisciplinary Digital Publishing Institute, 2020-09-19) Badeggi, Umar M.; Badmus, Jelili A.; Botha, Subelia S.; Ismail, Enas; Marnewick, Jeanine L.; Africa, Charlene Wilma Joyce; Hussein, Ahmed A.
In this study, procyanidin dimers and Leucosidea sericea total extract (LSTE) were employed in the synthesis of silver nanoparticles (AgNPs) and characterized by ultraviolet-visible (UV-Visible) spectroscopy, high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), and dynamic light scattering (DLS) techniques. AgNPs of about 2-7 nm were obtained. DLS and stability evaluations confirmed that the AgNPs/procyanidins conjugates were stable. The formed nanoparticles exhibited good inhibitory activities against the two enzymes studied. The IC50 values against the amylase enzyme were 14.92 ± 1.0, 13.24 ± 0.2, and 19.13 ± 0.8 µg/mL for AgNPs coordinated with LSTE, F1, and F2, respectively. The corresponding values for the glucosidase enzyme were 21.48 ± 0.9, 18.76 ± 1.0, and 8.75 ± 0.7 µg/mL. The antioxidant activities were comparable to those of the intact fractions. The AgNPs also demonstrated bacterial inhibitory activities against six bacterial species. While the minimum inhibitory concentrations (MIC) of F1-AgNPs against Pseudomonas aeruginosa and Staphylococcus aureus were 31.25 and 15.63 µg/mL respectively, those of LSTE-AgNPs and F2-AgNPs against these organisms were both 62.50 µg/mL. The F1-AgNPs demonstrated a better bactericidal effect and may be useful in food packaging. This research also showed the involvement of the procyanidins as reducing and capping agents in the formation of stable AgNPs with potential biological applications.
Group B streptococcus serotypes in pregnant women from the Western Cape region of South Africa
(Frontiers, 2018-12-04) Africa, Charlene Wilma Joyce; Kaambo, Eveline
Background: Maternal colonization of Group B streptococci (GBS) during pregnancy is an important risk factor for neonatal morbidity and mortality. The aim of this study was to determine the prevalence and serotype distribution of GBS isolated from a cohort of pregnant women in the Western Cape, South Africa. Methods: Two ano-vaginal swabs were collected from 301 women at 28–37 weeks of gestation. Participants were recruited from four different antenatal clinics in the Western Cape, South Africa. GBS were detected by culture and PCR and serotypes confirmed by latex agglutination tests. Antibiotic sensitivity was performed using disc diffusion. Results: The GBS colonization rate was 16.6%. Serotype distribution revealed serotype V as the predominant serotype (66.67%) followed by serotype III (21.05%). Serotypes Ia, II, IV, and IX constituted 1.75% each and 3 GBS isolates were non-typeable. Serotype V demonstrated resistance to most of the antibiotics tested, while serotype III demonstrated better susceptibility, except for tetracycline. No significant differences were observed for GBS colonization or serotype distribution according to HIV status. Conclusion: Predominating serotypes differed from those previously reported from other regions in South Africa. Global surveillance of serotype distribution plays an important role in informing vaccine development and antibiotic prophylaxis.
HPLC-MS identification and expression of Candida drug-resistance proteins from African HIV-infected patients
(AIMS Press, 2021-09-10) Abrantes, Pedro Miguel dos Santos; Fisher, Randall; Bouic, Patrick J D; McArthur, Carole P; Fielding, Burtram C; Africa, Charlene Wilma Joyce
The objective of this study was to elucidate the proteomic mechanisms of drug resistance in HIV-infected African patients. Cell membrane fractions from forty oral Candida isolates isolated from African HIV-positive patients were analysed using HPLC-MS with the aim of identifying proteins associated with their pathogenicity and drug resistance. Heat shock proteins that mediate the fungicidal activity of salivary peptides were found in all tested Candida fractions, with pH-responsive proteins associated with increased pathogenicity only being present in the three most commonly isolated species. ABC multidrug transporter efflux pumps and estrogen binding proteins were only found in C. albicans fractions, while ergosterol biosynthesis proteins were identified in four species. The combination of various adherence, invasion, upregulation and efflux pump mechanisms appear to be instrumental for the Candida host colonization and drug resistance emergence in HIV-infected individuals.
Is human immunodeficiency virus (HIV) stage an independent risk factor for altering the periodontal status of HIV-positive patients? A South African study
(BMC, 2013) John, Cathy Nisha; Stephen, Lawrence Xavier; Africa, Charlene Wilma Joyce
The immunosuppresion in HIV patients makes them highly susceptible to microbial infections. The aim of the study was to establish whether HIV stage (as depicted by CD4+ T lymphocyte counts) could independently be associated with periodontal status (as revealed by the measurement of clinical indices). One hundred and twenty HIV-infected patients attending an infectious diseases clinic in the Western Cape, South Africa were included in the study. The periodontal clinical indices such as plaque index, gingival index, pocket probing depth and clinical attachment levels were measured on the mesial aspect of the six Ramfjord teeth. The CD4 + T cell counts were taken from the patients’ medical records and patients’ HIV stage determined and grouped according to their CD4+ T cell counts into A (<200 cells /mm3 ), B (200–500 cells /mm3 ) and C (>500 cells /mm3 ).
K21 compound, a potent antifungal agent: Implications for the treatment of fluconazole-resistant HIV-associated Candida species
(Frontiers, 2019-05-24) John, Cathy Nisha; Abrantes, Pedro Miguel dos Santos; Prusty, Bhupesh; Ablashi, Dharam; Africa, Charlene Wilma Joyce
Background/objectives: With mucocutaneous candidiasis being highly prevalent in HIV patients, the emergence of fluconazole-resistant Candida species forms a major challenge in treating and eradicating these infections. The objective of this study was to establish the antifungal activity of K21, a membrane-rupturing antimicrobial compound derived from a silica quaternary ammonium compound (SiQAC) with tetraethoxysilane (TEOS). Methods: The study sample included 81 Candida species of which 9 were type strains and 72 were clinical isolates. Minimum inhibitory concentrations, synergy, fractional inhibitory concentration index (FICI) and time kill assays were determined by broth microdilution. Electron microscopy (EM) was used to determine the qualitative changes brought about after treatment with K21. Results: K21 inhibited the growth of all fluconazole-resistant and susceptible Candida strains with only 2 hours of exposure required to effectively kill 99.9% of the inoculum, and a definite synergistic effect observed with a combination of K21 and fluconazole. EM demonstrated the presence of two forms of extracellular vesicles indicative of biofilm formation and cell lysis. Conclusion: The study established the efficacy of K21 as an antifungal agent and with fluconazole-resistant candidiasis on the increase, the development of K21 can provide a promising alternative to combat acquired drug resistance.
Measuring Streptococcus mutans, Streptococcus sanguinis and Candida albicans biofilm formation using a real-time impedance-based system
(Elsevier, 2019-12-20) Abrantes, Pedro Miguel dos Santos; Africa, Charlene Wilma Joyce
Candida albicans and streptococci are amongst the most common fungal and bacterial organisms present in the oral cavity, with a growing body of evidence implicating C. albicans in increased caries severity and in the formation of the cariogenic biofilm. However, the interactive mechanisms between cariogenic streptococci and Candida are yet to be elucidated. In this study, the real-time biofilm formation of C. albicans, S. mutans and S. sanguinis was assessed individually and in combination using the xCELLigence system, an impedance-based microbial biofilm monitoring system. The impedance signal was the highest for C. albicans, followed by S. mutans and S. sanguinis. Although the streptococcal mixed adhesion was found to follow a similar trend to that of S. sanguinis, the introduction of C. albicans resulted in higher adhesion patterns, with the combined growth of S. sanguinis and C. albicans and the combination of all three species resulting in higher biofilm formation than any of the individual organisms over time. This study, the first to use impedance for real-time monitoring of interkingdom biofilms, adds to the body of evidence that C. albicans and oral streptococcal adhesion are interlinked and suggests that interkingdom interactions induce changes in the oral biofilm dynamics over time.
Oral health status and treatment needs of pregnant women attending antenatal clinics in KwaZulu-Natal, South Africa
(Hindawi, 2019) Africa, Charlene Wilma Joyce; Turton, Mervyn
During pregnancy, the oral cavity is characterised by an acidic environment and an inflammatory response brought about by vomiting and changes in hormonal levels, respectively, thereby increasing the mother’s risk of developing caries. Although evidence exists to support an association between pregnancy-associated periodontal disease and adverse pregnancy outcomes, there is a paucity of studies which focus on the caries prevalence and other oral manifestations of pregnant women. The aim of this study was to assess the oral health status and treatment needs of pregnant women attending antenatal clinics in KwaZulu-Natal, South Africa. Randomly selected mothers (n = 443) attending a maternal obstetrics unit participated in the study. A questionnaire elicited demographic information about the participants, while the measurement of decayed, missing, and filled indices (DMFT) determined their caries status. Oral lesions were noted if present. Descriptive statistics for independent variables described frequencies in the various categories of race, location, pregnancy stage, etc., with the association between 2 independent variables tested by chi-square. Dependent variables such as DMFT were expressed as means and standard deviations, and ANOVA was used to examine whether independent variables significantly influenced the DMFT. The mean DMFT was 7.18 (±4.22) with significant correlations observed between DMFT, D, M, and age. F scores differed significantly between races, location, and educational levels and showed a significant correlation with pregnancy stage. Pregnancy epulis was diagnosed in 38 (8.5%), oral lesions in 65 (14.7%), and tooth mobility in 26 (5.9%) mothers. Early oral health screening during pregnancy can ensure the overall well-being of both the mother and the foetus.
A population model for the 2017/18 listeriosis outbreak in South Africa
(PLoS One, 2020-03-12) Witbooi, Peter Joseph; Africa, Charlene Wilma Joyce; Christoffels, Alan; Ahmed, Ibrahim Hussin Ibrahim
We introduce a compartmental model of ordinary differential equations for the population dynamics of listeriosis, and we derive a model for analysing a listeriosis outbreak. The model explicitly accommodates neonatal infections. Similarly as is common in cholera modeling, we include a compartment to represent the reservoir of bacteria. We also include a compartment to represent the incubation phase. For the 2017/18 listeriosis outbreak that happened in South Africa, we calculate the time pattern and intensity of the force of infection, and we determine numerical values for some of the parameters in the model. The model is calibrated using South African data, together with existing data in the open literature not necessarily from South Africa. We make projections on the future outlook of the epidemiology of the disease and the possibility of eradication.

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