Question

Highlight the important concepts of microbe-human interaction in health and in infection and disease.

Outline and discuss the body’s immune system: 1st Line of Immunity, 2nd Line of Immunity and 3rd Line of Immunity (specific or acquired immunity).

Explain the phenotypic, genotypic, and immunologic methods to identify pathogens and diagnose infections.

Discuss in detail the structure and disease process of the pathogens associated with human disease including Gram (+) and Gram (-) cocci, Gram (+) and Gram (-) bacilli and miscellaneous bacterial pathogens.

Discuss in detail the structure and disease process of the pathogens associated with human disease including fungi, parasites, and viruses.

Discuss at least 3 important topics related to the course content.

Answer 1

1)Microbe-human interaction:

99% of human cells are of microbial origin.It has been considered that there are about 100 trillion cells in a human body. However, even one tenth are hardly real human cells and these are microbes.Нe human microbiome is a source of genetic diversity and no two human microbiomes are considered to be the same. Microbiome is an essential component of immunity and a functional entity that influences metabolism and modulates drug interactions.Microbes are present on skin,nose ,digestive tract and urinary tract.

HUMAN MICROBIOME PROJECT

skin: example Staphylococcus epidermidis

nasal cavity: example Staphylococcus

Human gut :Lactobacillus

MECHANISMS OF DEFENCE AGAINST INVADING PATHOGENS

Competition for space,nutrients and other resources for growth.

Probiotics: Probiotics are live bacteria and yeasts that are good for you, especially your digestive system (good bacteria).Popular probiotic drink yakult contains lactobacillus and bifidobacterium and aids in digestion.

However sometimes potential pathogenic bacteria come in close contact with the host and are responsible for opportunistic infections in immune-compromised hosts.example: E coli can cause urinary tract infections in females.

2) Immune system is a defence system against invading pathogens.It is divided into non specific defence (against all infections ) which is innate immunity and specific defence(adaptive immunity)

First line of immunity : physical barrier and guards against all infections: example: skin and tear .Tear contain lysozyme enzyme to lyse bacterial cell walls.

sec line of defence :if a pathogen makes a way into body can inflammation occurs and body temperature rises .An inflammatory response begins when a pathogen stimulates an increase in blood flow to the infected area. Blood vessels in that area expand, and white blood cells leak from the vessels to invade the infected tissue. These white blood cells, called phagocytes engulf and destroy bacteria. The area often becomes red, swollen, and painful during an inflammatory response.Increased temperature stops or slows the growth of microbes .

Third line of defence: If non specific immunity fails specific immunity( adaptive) acts.

HUMORAL IMMUNITY:

The immune system responds to antigens by producing cells that directly attack the pathogen, or by producing special proteins called antibodies. Antibodies attach to an antigen and attract cells that will engulf and destroy the pathogen.B cells release antibodies into the bloodstream example: IgA, IgE,IgM

CELL MEDIATED IMMUNITY:T cells are responsible for cell-mediated immunity. Killer T cells (cytotoxic T cells)assist with the elimination of infected body cells by releasing toxins into them and promoting apoptosis. Helper T cells act to activate other immune cells.

Vaccines are specific adaptive immune responses to a pathogen and work by ork by taking advantage of antigen recognition and the antibody response.

3) phenotypic : what can be seen example: mIcroscopy:

see morphology, arrangement patterns by the interaction of microbes with stain.example : gram negative staining: gram negative E. coli bacteria appears rod shaped pink with counterstain safranin.

culture and biochemical characteristics: growth on media and utilisation of different enzymes.

Genetic: they use genetic material DNA/RNA to identify bacteria. example : PCR( polymerase chain reaction) mediated sequencing of H.influenza.

Immunologic Methods

Microbes have antigens that stimulate the immune response by producing antibodies. Antibodies can be tested using a blood sample. Since antibodies are specific to their antigens, this can be very determinative to identifying the infectious agent.example : ELISA technique is an immunoassay technique for antigen- antibody reactions. Others are western blotting, agglutination testing .

WIDAl TEST: presumptive serological test for enteric fever or undulant fever. WIdal agglutination was introduced as a serologic technique to aid in diagnosis of typhoid fever. Testing was based on demonstrating the presence of agglutinin (antibody) in the serum of an infected patient, against the H (flagellar) and O (somatic) antigens of Salmonella typhi.