Chapter 24, 25, 26, 27, 30 (Selected topics - Microbe-Human Interactions)

Location of normal microbiota in/on the body

EVERYWHERE. Nose, eyes, ear, stomach, mouth, skin, small intestine, large intestine

Role of microbiota in the body

Normal microbiota protect us by competing with pathogens for space and nutrients, producing antimicrobial substances, helping digest food, making vitamins (such as vitamin K and some B vitamins), strengthening the immune system, and preventing harmful microbes from establishing infections.

Three microenvironments of the skin

Dry skin, Moist skin and Oily (sebaceous) skin

Skin microflora types

Resident and transient

Characteristics of mouth bacteria

Microbes colonize teeth and gums. Facultative anaerobes or obligate anaerobes

Bacterial growth in the mouth can lead to

Dental cavities, gingivitis, periodontal disease

Charactersitics of stomach bacteria

Most die by the 2 pH, a small number of microbes can survive if they pass through quickly or ingested in food particles

Characteristics of bacteria for small intestine

Increase of bacteria as we move down

Characteristics of bacteria in large intestine

Most are obligate anaerobes, 10^13 bacteria shed daily in feces, growt rapidly (1-2 doublings per day), largest microbial population in body, Bacteria make up ⅓ of the weight of fecal matter

Example of skin bacteria

Propionibacterium acnes

Example of mouth bacteria

Streptococcus spp.

Example of Stomach bacteria and what it causes

Helicobacter pylori, which causes ulcers

Example of Small intestine bacteria

Entrococcus faecalis and Lactobacili

Example of large intestine bacteria

Bacteroides, Clostridium,

C diff

spore former and difficult to treat

Example of bacteria found in upper respiratory tract

staphylococcus and streotococci

Example of bacteria found in lower respiratory track

None, there is no normal microbiota

Skin conditions that dont support growth of microbes

Inhospitable environment, mechanically strong barrier, slightly acidic PH, high concentration of NaCl, Many areas low in moisture, sweat

Conditions that limit growth in mouth

Saliva contains antimicrobial enzymes such as lysozyme, constant flushing of saliva

Conditions that promote growth in mouth

Many surfaces to attach to, ability to form biofilms (dental plague) protects microbes.

Conditions of stomach that limit microbial growth

Extremely acidic pH (2) which kills most microbes

Conditions of small intestine that support growth

Increasing pH as you move downward

Respitory track conditions that limit microbial growth

Continuous stream of mucus which contains lysozyme. Ciliated epithelial cells, phagocytic action of macrophages

Lower respiratory track conditions that limit microbial growth

Only very small particles can physically enter. Less than 10 um

Kidneys ureter and bladder

may harbor residental microbes

Distal portions of urethra

few mcrobes found. Urinary tract infection (E. Coli)

Female gential tract

complex microbiota in a state of flux due to menstrual cycle

Lactobacillus acidpphilus

Bacteria that predominates in vagina and maintains acidic conditons

Infection

The entry and multiplication of a microorganism (such as a virus, bacteria, or fungus) inside the body. The microbe is present, but symptoms may or may not occur.

Disease

The condition that results when an infection causes damage to the body and produces signs and symptoms. Not all infections lead to disease.

How normal microbiota can cause infection and disease

Normal microbiota usually protect us, but if they enter a part of the body where they don’t belong (such as gut bacteria entering the bloodstream), increase in number due to weakened immunity, or if the balance of microbes is disrupted (for example, after antibiotics), they can overgrow and cause infections. This overgrowth or movement to new sites can lead to tissue damage and symptoms—turning a normally harmless organism into a cause of disease.

Incubation period

Time between entering the body and first symptoms; microbes multiply but no signs are noticeable.

Prodromal phase

Early, mild symptoms appear (fatigue, low fever, discomfort).

Illness phase

Symptoms are most severe; pathogen is at peak activity.

Decline phase

Immune system or treatment reduces the number of pathogens; symptoms begin to decrease.

Convalescence

Recovery period; body repairs damage and returns to normal.

What factors will influence the outcome of an infectirous disease

Agent, Virulence, Exposre, Dose, Susceptibility.

Immune system

Composed of widely distributed cells, tissues and organs. Recognizes foreign substances or microbes and acts to neutralize or destroy them

Immunity

ability of host to resist a particular disease or infection

Immunology

the study of immune response

Examples of Innate immunity cells

Dendrite cell, neutrophil, and macrophage

Examples of adaptive immunity cells

B and T lymphocytes

Innate Immunte response

Acts as a 1st line of defense. The bodys ability to recongize and destroy pathogens or their products. Resistance to any microbe or foreign material. Lacks immunological memory. Includes physical and chemical barriers and phagocytes

Phagocytes

One of the several leukocytes with the capacity to engulf and destroy foreign substances. A non specific response, results in inflammation, some act as antigen presenting cells APC’s

Adaptive Immune response

Acts as 2nd line of defense, recongize angitgens from pathogens, very specific, have memory, can discriminate between self and nonself. Includes B and T cells and antibodies.

T cells (cell mediated)

Most in blood, mature in thymus, mobile, require antigen binding to T cell receptors TCR for activation and continued replication. Differentiate into effector cells (helper and cytotoxic) and memory. Play a major role in B cells

B cells (antibody mediated)

mature in bone marrow, not very mobile, activated by binding of specific antigen but usually require Th triggering as well. Differentiate into Plasma cells and memory B cells

Natural immunity

Is acquired through the normal life experiences of a human and is not induced through medical means

Artificial immunity

Is that produced purposefully through medical procedures

Active natural immunity

a person developing their own immune response to a microbe

Passive natural immunity

a person receiving preformed immunity made by another person (breast feeding)

Active Artificial immunity example

Vaccine

Passive artificial immunity example

Chemo/medicine