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Screening and Characterization of Neurotransmitters Produced by Different Microbes

Thesis Info

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Author

Taj, Aneela

Program

PhD

Institute

University of Karachi

City

Karachi

Province

Sindh

Country

Pakistan

Thesis Completing Year

2018

Thesis Completion Status

Completed

Subject

Microbiology

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/12393/1/FINAL%20DATA%20%28DR.%20ANILA%29.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727137099

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Neuroinvasive microbes include a wide variety of microorganisms that can enter the Central Nervous System (CNS). They are capable of exerting influences on the autonomic nervous system of the host by releasing extracellular metabolites that may cause alterations in the biochemical and neurophysiological environment. Consequently, the host’s synaptic, neuroendocrine, peripheral immune, neuroimmune and behavioral response facilitate the progression of infection. The present study was conducted to screen and characterize bioactive peptides produced by neuroinvasive bacteria i.e. Listeria monocytogenes (Lm), Bacillus cereus (Bc), Neisseria meningitidis (Nm) and Clostridium tetani (Ct) that are commonly involved in CNS infections. Bacterial peptides were used to correlate the neurological, biochemical, immunological and neuroimmunolgical aspects of pathogenesis of CNS infections. Lm and Nm were isolated from cerebrospinal fluid (CSF) samples collected from 92 mentally compromised patients. Bc and Ct were also included in the study. All bacterial strains were identified by standard biochemical procedures. Collected CSF samples were also screened for the presence of herpes simplex virus (HSV) by polymerase chain reaction (PCR). Bacteria were cultured and filter sterilized cell free cultural broths (SCFBs) were prepared. Behavioral study and neurotransmitter analysis were performed after giving interaperitonieal (i.p.) shot of each bacterial SCFB to 4 groups (Test; n=7) of Sprague Dawely (SD) rats whereas 2 groups each (Control; n=7) received nutrient broth (NB) control and sterile physiological saline control respectively. Motor and behavioral activities were observed and biogenic amines were extracted from whole brain and analyzed by high performance liquid chromatography with electrochemical detection (HPLC-EC). Biogenic amines were detected in SCFBs of each bacterium. Extracellular bioactive peptides of these bacteria were screened and purified. Neuropathogenic effects of purified peptides were studied on BALB/c mice cohorts and correlated with CSF biogenic amines. BALB/c mice hippocampal neurons were cultured as per standard protocols and effects of bacterial peptides on the voltage dependent K+ and Na+ channels of these neurons were studied by patch clamp. Human peripheral blood mononuclear cells (PMBCs) and BALB/c mice microglial cells were separately cultured for comparative analysis, exposed to bacterial peptides and were observed for the cytopatheic effects (CPEs). Cellular RNA was extracted, purified and quantified. Reverse transcriptase polymerase chain reaction (RT-PCR) was done to study the expression of immunocytokines and toll like receptors (TLRs). Signal transduction precursors were also detected. Comparative analysis was done with the cellular RNA extracted from glial cells. Present study concludes with the detection of NO production induced by peptides both in immune and neuroimmune cells. The results indicated that Nm was found in 22% of the collected samples. Presence of HSV along with the co-infection of HSV1 and HSV2 was confirmed in most of the negative bacterial culture samples. Co-infection of both bacterial and viral etiology was also detected in some samples. Our study indicated that bacterial SCFBs shots induced promising behavioral changes including fever, swelling and hind paw paralysis in respective Sprague Dawely (SD) rat cohorts. Biogenic amine profile of SD rats revealed enhanced concentration of dopamine (DA) in the brains of all SD rat cohorts whereas profound elevation was found exclusively in rats treated with Lm SCFB. Comparative analysis of biogenic amines in SCFB with plain media control revealed that Bc, Ct and Nm showed the complete degradation of DA into its metabolic products whereas Lm showed negligible degradation of DA. Purified bacterial peptides of all bacteria used in present study elicited marked changes in behavior along with enhanced concentration of DA in the brains of BALB/c mice cohorts. Comparative analysis with CSF biogenic amines indicated the presence of DA, Dihydroxyphenyl acetic acid (DOPAC), Homovanillic acid (HVA) and 5-hydroxy Indol acetic acid (5HIAA) in HSV infected CSF samples exclusively whereas increased amount of DA was found in Lm. Extracellular peptides of Lm and Bc caused the irreversible blockage of both K+ and Na+ channels of BALB/c mice hippocampal neurons. Peptides of Bc, Ct, Lm and Nm caused aggregation leads to distortion of immune and neuro-immune cells. RT-PCR profile revealed that TLR2 and TLR4 were commonly expressed in PMBCs and microglial cells. However, TLR3 was additionally expressed in microglial cells which is an alternative to TLR9 of the PMBCs. Expression of the range of proinflammatory cytokines i.e. Interleukin 1 β (IL1β), Interleukin 6 (IL6) and Tumor necrosis factor alpha (TNFα) were found to be mediated via MyD88 dependent pathway. Production of Nitric Oxide (NO) was mainly found in Lm peptides. The most important finding is that the detection and diagnosis of neurological infections on the basis of clinical signs are unsatisfactory. Therefore, existence of both viral and bacterial etiological agents must be checked to avoid the misdiagnosis and wrong treatment of the CNS infections. The sequence indicated the small size of extracellular peptides of Bc, Ct, Lm and Nm. Our study demonstrated the intervention of these peptides in the biochemical, neurological, immunological and neuro-immunological processes of the host. Therefore, bacterial peptides would have far reaching implications in disease progression. It is significant to note that these peptides definitely carry certain pattern which is complimentary to the TLRs of PMBCs and microglial cells as both cells recognized and induced immune and neuro-immune processes. Present study initiates a new venue of research for screening and characterization of such bioactive peptides in other pathogens.
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Studies on the Isolation and Characterization of Secondary Metabolites from Dodonaea Viscosa and Quercus Baloot and Their Potential As Antibacterial Agents

The present studies were aimed to isolate and characterize the secondary metabolites responsible for antibacterial activity from medicinal plants present in Pakistan. Two plant species Dodonaea viscosa (L.) Jaeq. and Quercus baloot Griff. were selected on the basis of literature review and their traditional uses in ailments related to microorganisms. The n-hexane, dichloromethane, ethyl acetate, n-butanol and aqueous fractions of Dodonaea viscosa were analyzed for antimicrobial potential against four Gram positive bacteria: Bacillus subtilis (MRL M 1), Bacillus cereus (MRL M 52), Micrococcus luteus (ATCC 10240), Staphylococcus aureus (ATCC 6538); three Gram negative bacteria: Escherichia coli (ATCC 25922), Salmonella typhi (Cl. I. 140), Pseudomonas aeruginosa (ATCC 9721) and the yeast Candida albicans (Cl. I. 4043). It showed inhibition against S. aureus, M. luteus, B. subtilis, E. coli, P. aeruginosa and C. albicans. The TLC solvent systems for each of the fraction were developed and the resulting chromatograms of the fractions were sterilized using ethylene oxide or dioxane, which were then subjected to contact bioautography. Multiple inhibition zones were observed at different R f values against B. subtilis, M. luteus, E. coli, S. typhi, P. aeruginosa, and C. albicans indicating the presence of antimicrobial components. Isolation of the active principles responsible for the antimicrobial activities was attempted through preparative TLC, but it was unable to yield the compounds. The results from the preliminary screening and contact bioautography indicated n-hexane, ethyl acetate and n-butanol fractions having good potential in terms of antimicrobial activities, therefore, they were chosen for further investigations. HPLC revealed the presence of large number of metabolites; therefore, further isolation was done using preparative HPLC that resulted in 52 sub-fractions each for n-hexane and n-butanol fractions while 48 sub-fractions were obtained from ethyl acetate fraction. XTT-Bioassay was used in hyphenation with preparative HPLC to mark the antibacterial potential of the emerging sub-fractions. S. aureus (NCIMB 6571) and E. coli (NCIMB 8797) were used in all XTT based bioassays. On the basis of bioassay results, six sub-fractions from n-hexane fraction were selected and analyzed upon HPLC in analytical mode, which indicated multiple numbers of compounds in them, thereby, necessitating further isolation. Further fractionation gave 218 sub-sub fractions that were tested against the same two bacteria. The sub-sub fractions indicating antibacterial activity were analyzed upon HPLC and isolation of the compound was possible from the sub-sub fraction no. 12 of sub-fraction 42 of n-hexane fraction of D. viscosa’s crude ethanolic extract. The compound’s MIC’s against S. aureus (NCIMB 6571) and E. coli (NCIMB 8797) were 64 μg/ml and 128 μg/mlxviii respectively. The MBC’s against these organisms were 128 μg/ml and 256 μg/ml, respectively, which indicated a moderate activity against the Gram-positive bacterium. The structure analyses revealed the compound to be 15, 16-epoxy-cis-cleroda-3, 13(16),14- trien-18-oic acid-18,6-olide, a clerodanefuranolactone, previously known for its structure but this is the first report of its antibacterial potential and its presence in D. viscosa. Quercus baloot fractions were processed in the same manner and were subjected to antimicrobial analysis using similar panel of microorganisms. Preliminary screening using disk diffusion and agar well diffusion methods showed inhibition zones against S. aureus, M. luteus, B. subtilis, E. coli, P. aeruginosa and C. albicans. TLC chromatograms and subsequent contact bioautography showed inhibition zones at different R f values against B. subtilis, M. luteus, E. coli, and S. aureus indicating the presence of antimicrobial components. On the basis of these findings QDM fraction underwent HPLC evaluations that indicated a good number of metabolites; therefore, preparative HPLC was carried out that yielded 52 sub-fractions that were subjected to XTT bioassay to mark the antibacterial potential from which five potential sub-fractions were again analyzed upon HPLC. Each sub-fraction had several compounds, thereby; preparative HPLC was applied that resulted in 175 sub-sub fractions, which were subjected to XTT bioassay using same two bacteria. The sub-sub fractions indicating antibacterial activity were analyzed upon analytical HPLC and isolation of a semi-purified compound was made from the sub-sub fraction no. 15 and 16 of sub-fraction 39 of dichloromethane fraction obtained from Q. baloot’s crude methanolic extract. Its MIC’s against S. aureus (NCIMB 6571) and E. coli (NCIMB 8797) were 16 μg/ml and 128 μg/ml respectively while MBC’s were 64 μg/ml and 256 μg/ml, respectively. This compound requires further purification and characterization. This is the first report of such an activity in Q. baloot.