Walid Bakeer - Academia.edu (original) (raw)

Papers by Walid Bakeer

Iranian Journal of Microbiology

Background and Objectives: Dental caries is a breakdown of the teeth enamel due to harmful bacter... more Background and Objectives: Dental caries is a breakdown of the teeth enamel due to harmful bacteria, lack of oral hygiene, and sugar consumption. The acid-producing bacterium Streptococcus mutans is the leading cause of dental caries. Dextra- nase is an enzyme that can degrade dextran to low molecular weight fractions, which have many therapeutic and industrial applications. The purpose of the present study was to isolate a novel dextranase-producing bacteria from asource (molasses). The cell-free extracts containing dextranases were tested as antibiofilm agents. Materials and Methods: Dextranase-producing bacteria were identified using phenotypic and genotypic methods such as 16S rRNA gene sequencing and enzymatic characterization. Results: The highest six dextranase-producing bacterial isolates were Bacillus species. The best conditions for dextranase productivity were obtained after 72hours of culture time at pH 7. The addition of glucose to the medium enhanced the pro- duction o...

Egyptian Pharmaceutical Journal

Royal Society Open Science, 2022

Lack of new anti-cancer and anti-infective agents directed the pharmaceutical research to natural... more Lack of new anti-cancer and anti-infective agents directed the pharmaceutical research to natural products' discovery especially from actinomycetes as one of the major sources of bioactive compounds. Metabolomics- and dereplication-guided approach has been used successfully in chemical profiling of bioactive actinomycetes. We aimed to study the metabolomic profile of five bioactive actinomycetes to investigate the interesting metabolites responsible for their antimicrobial and anti-cancer activities. Three actinomycetes, namely, Streptomyces sp. SH8, SH10 and SH13, were found to exhibit broad spectrum of antimicrobial activities, whereas isolate SH4 showed the broadest antimicrobial activity against all tested strains. In addition, isolates SH8, SH10 and SH12 displayed potent cytotoxicity against the breast cancer cell line Michigan Cancer Foundation-7 (MCF-7), whereas isolates SH4 and SH12 exhibited potent anti-cancer activity against the hepatoma cell line hepatoma G2 (HepG2) ...

Additional file 1: Figure S1. 1H-1H COSY spectrum for the major compound in fraction 8, measured ... more Additional file 1: Figure S1. 1H-1H COSY spectrum for the major compound in fraction 8, measured in MeOD. Figure S2. 1H-13C HMBC spectrum for the major compound in fraction 8, measured in MeOD. Figure S3. 1H-13C HSQC spectrum for the major compound in fraction 8, measured in MeOD. Figure S4. Full 1H NMR spectrum of fraction 24, measured in MeOD. Figure S5. 1H-1H COSY spectrum for the major compounds in fraction 24, measured in MeOD. Figure S6. 1H-13C HMBC spectrum for the major compound in fraction 24, measured in MeOD. Figure S7. 1H-13C HSQC spectrum for the major compounds in fraction 24, measured in MeOD.

Journal of Pure and Applied Microbiology, 2021

Antimicrobial resistance gene profile characterization and dissemination offer useful detail on t... more Antimicrobial resistance gene profile characterization and dissemination offer useful detail on the possible challenge in treating bacteria. The development of aminoglycoside modifying enzymes (AMEs) is considered as the primary mechanism of resistance to aminoglycosides, in addition to the 16S rRNA methylases. This study aimed at isolation and characterization of aminoglycosides resistant clinical isolates of enterobacteriaceae family from different clinical samples. Over a period of 24 months, thirty samples were collected and 49 clinical isolates of E. coli [n=25], Klebsiella [n=13], Enterobacter species (n=7) and Proteus species (n=4) were isolated from Egyptian clinical laboratories. The identities of the cultures were confirmed following standard microbiological procedures. Resistance of the isolates to aminoglycosides was determined by the disc diffusion method and isolates with highest resistance (n=9) were selected and investigated for 16S rRNA methylase and AMES encoding g...

Essential oils are commonly used in herbal cough mixtures as antitussive and antimicrobial prepar... more Essential oils are commonly used in herbal cough mixtures as antitussive and antimicrobial preparations, for instance Thyme oil is used in many cough preparations in the Egyptian market and also Boswellia oil is traditionally used as an antitussive. The aim of this study is to compare the antitussive and antimicrobial activity of essential oils of Boswellia carterii and Thymus vulgaris referring to their chemical components which were studied by using different methods of analysis (UV, HPTLC, HPLC, GC and GC/MS). HPLC technique was used for the first time for analysis of Boswellia oil. Results showed that the principal component of Boswellia oil was octyl acetate (35.1%), while the major constituent of Thyme oil was thymol (51%). Both oils were effective as antitussives but Thyme oil was more efficient (89.3%) than Boswellia oil (59%) and also as antimicrobial. It could be concluded that Thyme and Boswellia oils are effective as antitussives but less with Boswellia oil which could s...

Ventilator-associated pneumonia (VAP) is a major health problem for people intubated in intensive... more Ventilator-associated pneumonia (VAP) is a major health problem for people intubated in intensive care units (ICUs), leading to increased mortality rates, hospital stay, and treatment costs. In the present study, the core pathogens causing VAP in Beni-Suef University's Hospital, Egypt, was investigated over a study period of 2 years (2017–2019). Of a total of 213 patients subjected to mechanical ventilation, 60 have developed VAP during their stay in the ICU. The mortality rate reached 41.7% among VAP patients. Sixty bacteria were isolated from an endotracheal aspirate of hospitalized patients. The different isolates were cultured followed by running biochemical tests, sensitivity assays, and automated VITEK®2 System analysis. Unexpectedly, all the isolates were Gram-negative bacteria. Klebsiella pneumoniae were the main pathogen encountered (27/60 isolates) followed by Acientobacter baumannnii (7/60) and other microorganisms belonging to the genera Moraxella, Escherichia, and P...

Journal of Pure and Applied Microbiology, 2020

Acinetobacter baumannii is an opportunistic microorganism commonly found in intensive care units ... more Acinetobacter baumannii is an opportunistic microorganism commonly found in intensive care units (ICUs), and it is responsible for a broad span of hospital-acquired infections. Persistence of nosocomial infection caused by multidrug-resistant (MDR) A. baumannii is an alarming health care issue in Egypt, and at present, colistin remains the treatment of choice for the management of MDR A. baumannii infections. A. baumannii possesses great capacity to develop and acquire resistance to a broad range of antibiotics. The acquisition and dissemination of antibiotic-resistant determinants in A. baumannii strains are mediated by integrons, especially class I integrons. This study focuses on the characterization of some genetic mechanisms underlying the multidrug-resistant phenotypes of A. baumannii isolates in Egypt. Forty-eight A. baumannii specimens were isolated from different hospitalized patients; least resistance was observed against amikacin and tigecycline, with 60% and 58.5% of the...

Scientific Reports, 2021

Fungal endophytes are a major source of anti-infective agents and other medically relevant compou... more Fungal endophytes are a major source of anti-infective agents and other medically relevant compounds. However, their classical blinded-chemical investigation is a challenging process due to their highly complex chemical makeup. Thus, utilizing cheminformatics tools such as metabolomics and computer-aided modelling is of great help deal with such complexity and select the most probable bioactive candidates. In the present study, we have explored the fungal endophytes associated with the well-known antimalarial medicinal plant Artemisia annua for their production of further antimalarial agents. Based on the preliminary antimalarial screening of these endophytes and using LC-HRMS-based metabolomics and multivariate analyses, we suggested different potentially active metabolites (compounds 1–8). Further in silico investigation using the neural-network-based prediction software PASS led to the selection of a group of quinone derivatives (compounds 1–5) as the most possible active hits. S...

Beni-Suef University Journal of Basic and Applied Sciences, 2021

Background The rapid spread of antibiotic resistance has increased research interest in the disco... more Background The rapid spread of antibiotic resistance has increased research interest in the discovery of natural products, mainly from actinomycetes, which have been the primary source of antimicrobial compounds. This study aimed to isolate, characterize, and optimize the production of some of the bioactive compounds from bioactive soil actinomycetes. Results One promising soil actinomycete, which was molecularly identified as Streptomyces sp. and designated as Streptomyces sp. MS. 10, showed broad-spectrum antimicrobial activity, including activity against methicillin-resistant Staphylococcus aureus. Thus, it was selected for isolation of its major bioactive compounds. Polymerase chain reaction amplification of the genes responsible for antibiotic biosynthesis showed the presence of genes encoding type I and type II polyketide synthase. Liquid chromatography-mass spectrometry analysis found that the major antimicrobial compounds produced by Streptomyces sp. MS. 10 were weakly ioniz...

Antibiotics, 2020

In the present study, we investigated the actinomycetes associated with the Red Sea-derived soft ... more In the present study, we investigated the actinomycetes associated with the Red Sea-derived soft coral Sarcophyton glaucum in terms of biological and chemical diversity. Three strains were cultivated and identified to be members of genera Micromonospora, Streptomyces, and Nocardiopsis; out of them, Micromonospora sp. UR17 was putatively characterized as a new species. In order to explore the chemical diversity of these actinobacteria as far as possible, they were subjected to a series of fermentation experiments under altering conditions, that is, solid and liquid fermentation along with co-fermentation with a mycolic acid-containing strain, namely Nocardia sp. UR23. Each treatment was found to affect these actinomycetes differently in terms of biological activity (i.e., antitrypanosomal activity) and chemical profiles evidenced by LC-HRES-MS-based metabolomics and multivariate analysis. Thereafter, orthogonal projections to latent structures discriminant analysis (OPLS-DA) suggeste...

RSC Advances, 2020

Application of Streptomyces glaucescens as a whole-cell oxidative biocatalyst without using an ex... more Application of Streptomyces glaucescens as a whole-cell oxidative biocatalyst without using an external cofactor.

PLOS ONE, 2019

Literature surveys, taxonomical differences, and bioassay results have been utilized in the disco... more Literature surveys, taxonomical differences, and bioassay results have been utilized in the discovery of new natural products to aid in Actinomycetes isolate-selection. However, no or less investigation have been done on establishing the differences in metabolomic profiles of the isolated microorganisms. The study aims to utilise bioassay-and metabolomics-guided tools that included dereplication study and multivariate analysis of the NMR and mass spectral data of microbial extracts to assist the selection of isolates for scaling-up the production of antimicrobial natural products. A total of 58 actinomycetes were isolated from different soil samples collected from Ihnasia City, Egypt and screened for their antimicrobial activities against indicator strains that included Bacillus subtilis, Escherichia coli, methicillin-resistant Staphylococcus aureus and Candida albicans. A number of 25 isolates were found to be active against B. subtilis and/or to at least one of the tested indicator strains. Principal component analyses showed chemical uniqueness for four outlying bioactive actinomycetes extracts. In addition, Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA) and dereplication study led us to further select two outlying anti-MRSA active isolates MS.REE.13 and 22 for scale-up work. MS.REE.13 and 22 exhibited zones of inhibition at 19 and 13 mm against MRSA, respectively. A metabolomics-guided approach provided the steer to target the bioactive metabolites (P<0.01) present in a crude extract or fraction even at nanogram levels but it was a challenge that such low-yielding bioactive natural products would be feasible to isolate. Validated to occur only on the active side of OPLS-DA loadings plot, the isolated compounds exhibited medium to weak antibiotic activity with MIC values between 250 and 800 μM. Two new compounds, P_24306 (C 10 H 13 N 2) and N_12799 (C 18 H 32 O 3) with MICs of 795 and 432 μM, were afforded from the scale-up of MS. REE. 13 and 22, respectively.

Biomolecules, 2019

Mycobacteriophage endolysins have emerged as a potential alternative to the current antimycobacte... more Mycobacteriophage endolysins have emerged as a potential alternative to the current antimycobacterial agents. This study focuses on mycolylarabinogalactan hydrolase (LysB) enzymes of the α/β-hydrolase family, which disrupt the unique mycolic acid layer of mycobacterium cell wall. Multiple sequence alignment and structural analysis studies showed LysB-D29, the only enzyme with a solved three-dimensional structure, to share several common features with esterases (lacking lid domain) and lipases (acting on long chain lipids). Sequence and structural comparisons of 30 LysB homology models showed great variation in domain organizations and total protein length with major differences in the loop-5 motif harboring the catalytic histidine residue. Docking of different p-nitrophenyl ligands (C4-C18) to LysB-3D models revealed that the differences in length and residues of loop-5 contributed towards wide diversity of active site conformations (long tunnels, deep and superficial funnels, shall...

Journal of Pure and Applied Microbiology, 2019