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General Microbiology - NEETMDS- courses
NEET MDS Lessons
General Microbiology

Types of microscopy used in bacteriology

Light microscopy
Phase contrast microscopy
Fluorescence microscopy
Darkfield microscopy
Transmission electron microscopy
Scanning electron microscopy

Fluorescent microscopy in which ultraviolet rays are used to examine cells after treatment with fluorescent days.

Phase contrast microscope enhances the refractive index differences of the cell components. This microscopy can be used to reveal details of the internal structures as well as capsules, endospores and motility

Electron microscope The resolving power is more than 200 times that of light microscope.
 

DISINFECTION AND STERILIZATION

•    Sterilization is the best destruction or com removal_of all forms of micro organisms.
•    Disinfection is the destruction of many microorganisms but usually the b spores.
•    Antisepsis is the destruction or inhibition of microorganisms in living tissues thereby limiting or preventing the harmful effect of infection.
•    Astatic Agent  would only inhibit the growth of microorganisms (bacteriostatic, fungistatic, sporostatic).
•    Acidal agent would kill the microorganism (bactericidal. virucidal, fungicidal)
•    Sterilants are the chemicals which under controlled conditions can kill sporinQ bacteria.
 

Radioimmunoassays (RIA)

It is an extremely sensitive technique in which antibody or antigen is labelled with a radioactive material. The amount of radioactive material in the antigen-antibody complex can be measured with which concentration of antigen or antibody can be assayed. After the reaction ‘free’ and ‘bound’ fractions of antigen are separated and their radioactivity-measured.
 

Autoantibodies

Anti-nuclear antibodies (ANA)    Systemic Lupus
Anti-dsDNA, anti-Smith               Specific for Systemic Lupus
Anti-histone                                 Drug-induced Lupus
Anti-IgG                                       Rheumatoid arthritis
Anti-neutrophil                             Vasculitis
Anti-centromere                           Scleroderma (CREST)
Anti-Scl-70                                   Sclerderma (diffuse)
Anti-mitochondria                         1oary biliary cirrhosis
Anti-gliadin                                   Celiac disease
Anti-basement membrane            Goodpasture’s syndrome
Anti-epithelial cell                          Pemphigus vulgaris
Anti-microsomal                            Hashimoto’s thryoiditis

Cell Functions:
-> Autolysis

- degradative reactions in cells caused by indigenous intracellular enzymes – usually occurs after cell death
- Irreversible (along with Coagulative necrosis or infarcts) – reversible: fatty degeneration, & hydropic degeneration

-> Autolysin:
•    Ab causing cellular lysis in the presence of complement
•    Autolytic enzymes produced by the organism degrade the cell’s own cell wall structures

-> In the presence of cephalosporins & penicillins, growing bacterial cells lyse
•    W/o functional cell wall structures, the bacterial cell bursts

-> Heterolysis: cellular degradation by enzymes derived from sources extrinsic to the cell (e.g., bacteria)

-> Necrosis: sum of intracellular degradative reactions occurring after individual cell death w/in a living organism

Immunology:

The branch of life science which deals with immune reaction is known as immunology.

Components of Immune System:

The immune system consists of a network of diverse organs and tissue which vary structurally as well as functionally from each other. These organs remain spreaded throughout the body. Basically, immune system is a complex network of lymphoid organs, tissues and cells.

These lym­phoid organs can be categorized under three types depending upon their functional aspects:

i.  Primary lymphoid organ.

ii. Secondary lymphoid organ.

iii.Tertiary lymphoid organ.

White blood cells or leukocytes are the basic cell types which help to give rise to different types of cells which participate in the development of immune response . WBC are classified into granulocytes and agranulocytes depending on the presence or absence of granules in the cyto­plasm.

Agranular leukocytes are of two types, viz., lymphocytes and monocytes. Lymphocytes play pivotal role in producing defensive molecules of immune system. Out of all leukocytes, only lymphocytes possess the quality of diversity, specificity, memory and self-non self recognition as various important aspects of immune response.

Other cell types remain as accessory one; help to activate lymphocytes, to generate various immune effector cells, to increase the rate of anti­gen clearance 

All cells of the immune system have their origin in the bone marrow 

myeloid (neutrophils, basophils, eosinpophils, macrophages and dendritic cells) 

lymphoid (B lymphocyte, T lymphocyte and Natural Killer) cells .

The myeloid progenitor (stem) cell in the bone marrow gives rise to erythrocytes, platelets, neutrophils, monocytes/macrophages and dendritic cells whereas the lymphoid progenitor (stem) cell gives rise to the NK, T cells and B cells. 

For T cell development the precursor T cells must migrate to the thymus where they undergo differentiation into two distinct types of T cells, the CD4+ T helper cell and the CD8+ pre-cytotoxic T cell. 

Two types of T helper cells are produced in the thymus the TH1 cells, which help the CD8+ pre-cytotoxic cells to differentiate into cytotoxic T cells, and TH2 cells, which help B cells, differentiate into plasma cells, which secrete antibodies. 

Function of the immune system is self/non-self discrimination. 

This ability to distinguish between self and non-self is necessary to protect the organism from invading pathogens and to eliminate modified or altered cells (e.g. malignant cells). 

Since pathogens may replicate intracellularly (viruses and some bacteria and parasites) or extracellularly (most bacteria, fungi and parasites), different components of the immune system have evolved to protect against these different types of pathogens.

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