Bacterial Morphology and Structure

Bacterial Morphology

• Bacteria can be spherical, filiform, or cubic in shape.
• Formation of spores can be triggered by adverse external environments.

Bacterial Structure

• Mycoplasma and Rickettsia lack a cell wall.
• The bacterial cell wall is characterized by the presence of a complex biopolymer called peptidoglycan.

Bacterial Movement

• Peritrichous bacteria have flagella distributed over the entire cell surface.

Staining Techniques

• Gram staining differentiates gram-negative from gram-positive bacteria.
• Smears are fixed with a flame burner or methylene alcohol.
• Dark field microscopy allows studying bacteria in a living state.

Bacterial Cell Function

• Cell wall provides defense, cell shape, and protection.
• Gram staining reagents include crystal violet, iodine, decolorizing agent, and safranin.
• The nucleoid is the bacterial chromosome, containing a double-stranded DNA molecule.

Medical Microbiology

• Medical microbiology studies microorganisms that cause disease and their role in human health.

Infectious Processes

• Infectious processes require a pathogen, a susceptible host, and an environment conducive to the pathogen's survival.
• Septicemia is defined as the presence of bacteria in the bloodstream without any multiplication.

Virulence Factors

• Virulence refers to the degree of pathogenicity of a microorganism.
• Adhesion factors, invasion factors, and toxins contribute to virulence.
• Invasion factors include hyaluronidase and fibrinolysin.
• Pathogenicity enzymes include coagulase.
• Adhesion factors of gram-positive bacteria include teichoic acid and lipoproteins.

Bacterial Toxins

• Exotoxins are proteins released by bacteria.
• Endotoxins are lipopolysaccharides found in the cell wall of gram-negative bacteria.

Immunity

• Natural immunity is present at birth and is not specific.
• Artificial passive immunity is acquired through injection of antibodies.
• Barrier function of the skin and mucous membranes provide the first line of defense against pathogens.
• Normal microflora plays a protective role by competing with pathogens.
• Cellular protective factors include phagocytes and complement.
• Lysozyme, an enzyme, breaks down bacterial cell walls.
• Phagocytosis is the process of engulfing and destroying pathogens by phagocytic cells.
• Incomplete phagocytosis can occur in infections caused by certain bacteria like Salmonella Typhi.

Immune System Components

• T cells are responsible for cell-mediated immunity.
• B cells produce antibodies.
• Plasma cells are antibody-producing cells.
• Antibodies are proteins that bind to specific antigens.
• CD4 antigen is found on T helper cells.
• CD8 antigen is present on T suppressor cells.

Vaccines

• Adjuvants are substances added to vaccines to enhance their immunogenicity.
• Attenuated vaccines contain weakened forms of the pathogen.
• Inactivated vaccines contain killed pathogens.
• BCG is a vaccine against tuberculosis.

Immunological Reactions

• Immunofluorescence reaction uses antibodies labeled with fluorescent dyes to detect antigens.
• Complement fixation reaction is based on the interaction of antigen-antibody complexes with complement.
• Enzyme-linked immunosorbent assay (ELISA) is a sensitive method for detecting antibodies.

Serological Reactions

• Serological reactions are used to diagnose infectious diseases by detecting antibodies or antigens in blood serum.
• Agglutination reactions involve the clumping of antigen-coated particles by specific antibodies.

Antigens

• H antigen is associated with bacterial flagella.
• O antigen is found in the bacterial cell wall.
• Autoantigens are antigens from the host's own body that trigger autoimmune responses.
• Autoimmune reactions occur when the immune system attacks its own tissues.