scholarly works

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Start date: 2010End date: 2019

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    MOLECULAR CHARACTERISATION OF METALLO-BETA LACTAMASE AND OTHER RESISTANCE GENES IN PSEUDOMONAS AERUGINOSA FROM SEVEN TERTIARY HOSPITALS IN SOUTHWESTERN NIGERIA
    (2019-06) OLANIRAN, O.B
    The emergence of resistance to carbapenems, a last resort antibiotic, among Pseudomonas aeruginosa is of great health concern. Detailed studies on the molecular basis of carbapenem resistance in clinical P. aeruginosa isolates are scanty in Nigeria. Therefore, this study was aimed at determining the incidence of Metallo-Beta Lactamase (MBL) and other mechanisms mediating carbapenem resistance, and evaluating clonal spread among carbapenem-resistant P. aeruginosa isolates. Four hundred and forty-seven presumptive P. aeruginosa isolates collected from seven tertiary hospitals laboratories in southwestern Nigeria were identified using biochemical tests and amplification of oprI and oprL genes. Antibiogram of the isolates and Minimum Inhibitory Concentrations (MIC) were determined by Kirby-Bauer disk diffusion and broth microdilution, respectively. Phenotypic detection of carbapenemases was carried out using Modified-Hodge and combined disc tests. Carbapenem-resistant P. aeruginosa isolates were screened for class A, B and D carbapenemases, integrons and type III secretion effectors by Polymerase Chain Reaction (PCR) followed by sequencing of amplified carbapenemase genes. Transferability of MBL genes was determined by transformation experiments. Quantitative reverse transcription PCR (RT-qPCR) was used to quantify expression levels of eight efflux pump genes, ampC cephalosporinase and outer membrane porin oprD. The isolates were further genotyped using three PCR-based fingerprinting techniques. Fisher’s exact test was used to determine the association between MBL and integrons at p ≤ 0.05. Four hundred and thirty isolates were identified as P. aeruginosa of which 185(43.0%) were multidrug resistant and 50(11.6%) were extensively drug resistant. All the isolates were resistant to ampicillin, cephalothin and cefuroxime, while sensitivity to polymyxin B was most common (96.3%). The MICs ranged from 0.125 to >64 µg/mL and 0.0625 to >64 µg/mL against imipenem and meropenem, respectively. All the isolates were negative for Modified-Hodge test, while combined disc test revealed the presence of MBL. Two class B carbapenemases were detected in 86.3% of the carbapenem resistant isolates: blaVIM and blaNDM in 35.6% and 38.4% isolates, respectively, co-existing in 12.3% isolates. Fifty-one (57.5%) carbapenem-resistant P. aeruginosa strains carried class 1 integrons while class 1 and 2 integrons were present concomitantly in 12.3%. Type III effector genes, exoY and exoT were found in all isolates, while exoU and exoS were present in 49.3% and 53.4%, respectively. Two isolates possessed both exoU and exoS. Sequence analysis of blaVIM and blaNDM revealed maximum identity with blaVIM-5 and blaNDM-1, respectively. MBL genes were successfully transferred into Escherichia coli DH5α. MexXY-OprM was the most overexpressed pump (5.0 - 996.3 fold increase) occurring in 58.3% of the isolates. The ampC was overexpressed in 27.1% isolates, while oprD porin down-regulation was observed in 77.1% of the isolates. Nine disseminated clones were identified across southwestern states. There was positive association between integrons and MBL (p = 0.0064). There is a high incidence of transmissible metallo-beta lactamase genes in Pseudomonas aeruginosa from tertiary hospitals in southwestern Nigeria with different mechanisms mediating carbapenem resistance. blaVIM-5 and blaNDM-1 were found co-occurring for the first time. There is a need for surveillance of resistance to carbapenems and associated resistance genes.
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    Prevalence of methicillin resistant staphylococcus aureus and resistance pattern of its clinical strains to beta-lactam antibiotics
    (2014-05) Ayeni, F. A.; Olatunji, D. F.||Ogunniran, M.
    Staphylococcus aureus is the leading overall cause otf nosocomial infections with increasing resistance to β lactam antibiotics. This study was carried out to study the current resistant/susceptibility pattern of S. aureus to β lactam antibiotics and prevalence of Methicillin Resistant S. aureus (MRSA) in the studied population. Clinical isolates of S. aureus strains were collected from Medical Microbiology Unit of University College Hospital, Ibadan between May and October, 2012. The isolates were confirmed through growth on Mannitol Salt Agar (MSA) and tube coagulase test. The susceptibility / resistance pattern of the S. aureus strains to antibiotics were tested by disc diffusion method. Fifty studied S. aureus strains were highly resistant to Amoxycillin (92%), Aztreonam (70%), but high susceptibility was observed to Imipenem (90%), Cefotaxime (62%), Ceftazidine (50%), Cefoxitin (66%), Ceftriazone (52%), Amoxycillin/Clavulanic acid (50%), S. aureus strains (42%) that were resistant to amoxicillin were susceptible to amoxicillin/clavulanic acid while 34% of the studied S. aureus strains were MRSA. The relatively high prevalence of MRSA in the studied S. aureus strains call for surveillance studies and implementation policies in control of MRSA. Cephalosporins are still relatively effective for treatment of S. aureus infections. The observed synergy in this study between imipenem and aztreonam is an indication that combine therapy of imipenem and aztreonam will lead to enhanced antimicrobial activity of aztreonam.
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    In-Vitro Susceptibility of Mycobacterium Tuberculosis to Extracts of Uvaria Afzelli Scott Elliot and Tetracera Alnifolia Willd
    (2011-01) Lawal, T. O.; Adeniyi, B. A.; Wan, B.; Franzblau, S. G.; Mahady, G. B.
    Tuberculosis is a global burden with one –third of the world’s population infected with the pathogen Mycobacterium tuberculosis and an annual 2 million deaths from the disease. This high incidence of infection and the increased rate of resistant strains of the organism (MDR- and XDR- TB) have called for an urgent need to develop new anti-tuberculosis drugs from plants. The crude extract of Uvaria afzelli Scott Elliot (Annonaceae) root bark, and leaves and root bark of Tetracera alnifolia Willd. (Dilleniaceae) were investigated for anti-Mycobacterium tuberculosis activity using the MABA assay method. Anti- Mtb activity was determined against Mtb H37RvATCC 27294 at concentrations of 100- 0.390μg/mL. The hexane and chloroform extracts of the root bark of Tetracera alnifolia and the chloroform extract of Uvaria afzelli had anti- Mtb activity with MIC <100 μg/mL. Phytochemical screening for secondary metabolites revealed the presence of tannins, triterpenoid saponins, cardiac glycoside and alkaloids. The anti- Mtb activity demonstrated by the crude extracts is attributed to the presence of tannins and other secondary metabolites which are known to have strong antimicrobial activity. The results therefore support the local use of Uvaria afzelli and Tetracera alnifolia in the treatment of cough associated with tuberculosis and other microbial infections of the respiratory tract and suggest that these plants may be of therapeutic importance in the treatment of tuberculosis.
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    In-vitro Bactericidal Kinetics of Chlorhexidine Gluconate Disinfectant/ Antiseptic Formulations Containing Different Additives
    (2014-01) Idowu, P. A.; Idowu, O. S.
    Chlorhexidine gluconate(CHG) is a popular disinfectant/antiseptic which is often formulated with additives. We investigated the effect of additives type on the in vitro bactericidal kinetics of CHG in three commercially available formulations: Hibiscrub®, Savlon® and Purit® commonly used as household and hospital disinfectants/antiseptics. The bactericidal kinetics of the products was determined by time-survival curve method using Pseudomonas aeruginosa NCTC 6750 and Staphylococcus aureus NCTC 6571 as model organisms. Best-fit rate constant and half-life was computed by exponential decay curve-fitting. Half-life was; 76.5, 65.5, 66 and 74 (min) for Control solution, Hibiscrub®, Savlon® and Purit® respectively, against Ps. aeruginosa. The corresponding values obtained against Staph. aureus are 51.0, 61.7, 29.3, and 49.0 (min) (95% CI). Presence of alcohol (e.g. Hibiscrub® and Savlon®) caused an insignificant increase in the rate of killing of Ps. aeruginosa relative to preparations that are devoid of alcohol. (p>0.05, 1-way ANOVA). Toward Staphylococcus aureus, the combined effect of cetrimide and alcohol (e.g. Savlon®) is higher than any enhancement due to combination of alcohol and surfactant (e.g. Hibiscrub). Savlon® show a significantly higher bactericidal effect of all the preparations (P<0.0001, 1-way ANOVA). The choice of additives in the formulation of chlorhexidine antiseptic solutions significantly alters the kinetics and overall bactericidal effect of CHG towards Staphylococcus aureus but not Pseudomonas areruginosa.
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    In-vitro antimicrobial activities of methanol extracts of
    (2010-01) Adeniyi, C. B. A.; Odumosu, B. T.; Ayelaagbe, O. O.; Kolude, B.
    The antimicrobial activities of two Nigerian medicinal plant commonly used as chewing sticks Zanthoxylum xanthoxyloides and Pseudocedrela kotschyi antimicrobial activities were investigated against 7clinical strains of Streptococcus mutans, Staphylococcus aureus ATCC 29213, Candida albicans, Candida tropicalis and Candida krusei ATCC 6825. The antibacterial and antifungal activities of the extracts were determined using the agar well diffusion and surface plate method respectively. Zanthoxylum xanthoxyloides, was active against all the isolates especially on the bacteria with a MIC and MBC of 12.5mg/mL and 25mg/mL respectively. Pseudocedrela kotschyi showed no activity on all the tested isolates except on C. krusei ATCC 6825 with a MIC of 6.25mg/mL. . Streptococcus mutans, S. aureus ATCC 29213 and C. albicans were completely killed within the time period of4hrsbyZ. xanthoxyloides extracts in time kill study. A good correlation was foundbetween the killing curves and the MIC of Z. xanthoxyloides against the tested isolates. Phytochemical screening revealed the presence of alkaloids, tannins, flavonoids, saponins and traces of terpenoids. Ability of Z. xanthoxyloides crude extracts to inhibit the growth of the bacteria and fungi used in this study is an indication that the plant can be used as a source foranti microbial agent in the development and formulation of toothpaste, thus justifying the use of the plant in locally as chewing sticks..
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    In vitro anti-mycobacteria sensitivity and Kill-kinetics of allium ascalonicum L. (whole plant) on nontuberculous mycobacteria species
    (2014-05) Igbokwe, C. O.; Lawal, T. O.; Adeniyi, B. A.
    Allium ascalonicum L. (Shallot) was one of the herbs repeatedly identified from the result of our ethnobotanical survey for the treatment of tuberculosis and nontuberculous mycobacteria diseases. It has been reported to show inhibitory potentials against several pathogens. This plant is also known to form part of the diet of many people across the world. In the quest for a more active and body-friendly therapeutic agents, extracts of Allium ascalonicum (whole plant) were screened against four nontuberculous mycobacteria species namely, Mycobacterium fortuitum ATCC 684, Mycobacterium smegmatis ATCC 19420, Mycobacterium abscessus and Mycobacterium phlei ATCC 19240. In vitro susceptibilities testing was done using agar diffusion method with the concentrations of extracts ranging between 25 to 200 mg/mL. The minimum inhibitory concentration (MIC) was determined by agar dilution methods while the kill or bactericidal kinetics was measured by viable counting technique. Methanolic extract demonstated significant inhibitory potentials against three of the organisms at the test concentrations with a minimum inhibitory concentration (MIC) of 100 mg/mL, and 72-98 % kill of susceptible organisms in 24 hours. This significant activity may be due to the presence and right combination of the secondary metabolites in the plant such as alkaloids, flavonoids saponins, cardiac glycosides and essential oil, as revealed from our phytochemical screening. This study therefore confirms the scientific bases and justifies the use of Allium ascalonicum L. in traditional medicine practice in Nigeria and other parts of the world; and encourages its consumption as a natural prophylaxis against tuberculosis and nontuberculous mycobacteria diseases.
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    Antifungal capacity of lactic acid bacteria isolated from salad vegetables
    (2011-05) Adeniyi, B.; Damsa, I.
    This study explores the use of lactic acid bacteria from fresh salad vegetables to inhibit fungal growth. The antifungal assay was done using the agar well diffusion method as reported by Schillinger and Lucke (1989). The largest zone of inhibition (25mm) was recorded by the antagonistic activity of the isolate identified to Lactobacillus plantarum against Candida albicans ATCC 90029. No activity was recorded against Candida parapsilosis ATCC 22019, C. valida UCH 1508, C. pseudotropicalis UCH1408, C. tropicalis UCH 1308 and Trichophyton interdigitalis UCH1708. The cell free supernatant (CFS) of the isolate described to be Lactobacillus brevis was exceptional as it was the only CFS that inhibited the growth of Epidermophyton floccosum UCH 1908. The results show that LAB isolated from salad vegetables can inhibit some fungi pathogens by developing zones around agar well that contain LAB metabolites and can probably be a feasible option for the chemotherapy of fungal infections given the drug resistance exhibited to antifungal agents currently in use.