Micro Exam 3

Chapter 13



13.1 - 



Holobiont- a human plus all of its resident microbiota 



Human Microbiome project - a project of the National Institutes of Health to identify microbial inhabitants of the human body and their role in health and disease

*we only knew about bacteria and fungi because we could grow it in a lab, with the project we discovered hundreds of microbes that cannot be cultured 



Microbial antagonism- relationship in which microorganisms compete for survival in a common environment by taking actions that inhibit or destroy another organism 



Endogenous- originating or produced within an organism or one of its parts 

*an endogenous infection is a infection caused by biota already present in the body 



Opportunistic- ordinarily non pathogenic or weakly pathogenic microbes that cause disease primarily in an immunologically compromised host 



Virulence- in infection, the relative capacity of a pathogen to invade and harm host cells 

*is the accurate term for describe the degree of pathogenicity 



Virulence factor- a microbes structures or capabilities that allow it to establish itself in a host and cause damage 



Infectious dose- infections will only occur is a minimum number is present

*numbers below the ID will not cause infection, numbers above the ID will 



Portal of entry- route of entry for an infectious agent; typically a cutaneous or membranous route 



Polymicrobial: Infections from more than one microbe 



Portals of Entry; Becoming establish

Step 1: Finding a portal of entry



Exogenous: originating outside the body 

*opposite of endogenous



Types of portals of entry: 

  1. Skin - through abrasions, broke skin, or bites 

  2. Gastrointestinal tract - by contaminated food, drink, or ingested substances

  3. Respiratory tract - oral and nasal cavities 

  4. Urogenital - contracted by sexual means 

Pathogens that infect during birth

T -toxoplasmosis

O -other diseases

R -rubella

C -cytomegalovirus

H - herpes



Step 2: Attaching to the host and interacting with the microbiome 



Adhesion- process where microbes gain a more stable foothold on host tissues 



-Bacteria, fungi, and protozoal pathogens attach by fimbriae, surface proteins, and adhesive slimes or capsules 



-Viruses attach by specialized spikes and glycoproteins



-Helminths attach by suckers, hooks, and barbs 



Step 3: Surviving Host Defenses 



Phagocytes- a class of white blood cells capable of engulfing other cells and particles 

*engulf and destroy pathogens by means of enzymes and antimicrobial chemicals 



Leukocidin- a heat-labile substance formed by some pyogenic cocci that impairs and sometimes lyses leukocytes 



Epigenetic- referring to changes in the way DNA is transcribed, not actual changes in the DNA sequence 



Step 4: Causing Disease



The three main ways microbes can cause disease to the host are

  1. By secreting proteins (enzymes or toxins) that directly damage host cells 

  2. Causing an overreaction by the body's defenses and those defenses cause host damage 

  3. Altering the host cell genome or transcription process through epigenetic changes



  1. Direct damage via enzyme and toxins 



Exoenzymes- break down and inflict damage on tissues, extracellular enzyme 



Examples of exoenzymes are: 

-Mucinas: digests the protective coating on mucous membranes

-Keratinase: digests keratin 

-Hyaluronidase: digests hyaluronic acid



Toxigenicity- the power to produce toxins 



Toxinoses- disease whose adverse effects are primarily due to the production and release of toxins 



Toxemia- condition in which a toxin is spread throughout the bloodstream 



Intoxications- poisoning that results from the introduction of a toxin into body tissues through ingestion or injection 



Types of toxins 

-Neurotoxins: act on the nervous system 

-Enterotoxins: act on the intestines 

-Hemotoxins: act on red blood cells 

-Nephrotoxins: damage the kidneys 



Exotoxin- a toxin that is secreted by a living bacterial cell into infected tissues 

*causes more harm than endotoxin 



Endotoxin- a toxin that is not actively secreted but is shed from the outer membrane 

*found on all gram-negative bacteria 

*lipopolysaccharide



Hemolysins- class of bacterial exotoxin that disrupts the cell membrane of red blood cells 




  1. Inducing an excessive host response



N/A on info 



  1. Epigenetic changes in host cells 



N/A on info 



Patterns of Infection 



Localized infection- the microbe enters the body and remains confined to a specific tissue 

-boils, fungal infections, and warts



Systematic infection- infection spreads to several sites and tissue fluids, usually in the bloodstream



Focal infection- infectious agent breaks loose from a local infection and is carried into other tissues 



Leukocytosis- increase in white blood cells 

Leukopenia- decrease in white blood cells 



Step 5: Vacating the Host- Portals of Exit 



Types of portals of exit

  1. Respiratory and salivary portals - mucus, sputum and nasal drainage 

  2. Skin scales - shed skin and scalp 

  3. Fecal exit - poop 

  4. Urogenital tract - vaginal discharge or semen and urine 

  5. Removal of blood or bleeding- blood removed or released from a puncture 




Latency- The state of being inactive 



*There are four phases of infection and disease

  1. Incubation period -from time of contact of disease to first symptoms 

  2. Prodrome stage - start of mild symptoms indicating the onset of disease

  3. Acute period - the disease becomes well established and multiples

  4. Convalescent period - immune system responds and you start to get better




*There can be a fifth stage that some diseases have which is the continuation phase in which the organism lingers or the symptoms linger 



Passive carrier- person who mechanically transfers a pathogen without ever being infected by it; like a healthcare worker not washing their hands in between patients 



Horizontal pattern of transmission: disease is spread through a population from one infected individual to another 



Vertical pattern of transmission: transmission from parent to offspring via ovum, sperm, placenta, or milk



Vehicle: an inanimate material that serves as a transmission agent for pathogens 



Fomite: inanimate object that harbors or transmits pathogens and is not a continuous source of infection 






Kochs Postulates to Determine Etiology 

  1. The agent must be found 

  2. Inoculations of a pure culture must reproduce the same disease in animals 

  3. The agent must again be present in experimental animal 

  4. A pure culture must again be obtained 



*Epidemiologists focus their work on the 5 W’s… Who, what, where, when, and why, and focuses on population more than individuals 



Florence Nightingale: She is the first to collect and use health, disease, and death statistics for the purpose of improving public health 



John Snow: Was the first to use a map to see the cause and events of a disease 



Point-source: infectious agent came from one source and everyone that was exposed, was exposed of the same source at the same time. 



Common-source: outbreak resulting from common exposure to a single source of infection that can occur over a period of time 



Propagated epidemic: results from an infectious agent that is communicable from person to person and is therefore sustained over time in a population 



Healthcare associated infection: any infection acquired as a direct result of a patient's presence in a hospital or health care setting 



Herd immunity: the status of a collective acquired immunity in a population that reduces the likelihood that non immune individuals will contract and spread infection. 



The lines of defense 



-The first line of defense includes any barriers that block invasion at the portal of entry, and limits access to the internal tissues of the body 

*the skin, hair follicles, and skin glands



-The second line of defense is an internalized system of protective cells and fluids and includes inflammation, phagocytosis, fever, and antimicrobial products. 

  • The three main types of phagocytes are neutrophils, monocytes, and macrophages. 



Neutrophils- react early in inflammatory response to bacteria and foreign materials 

Eosinophils- are attached to sites of parasitic infections, play a minor phagocytic role 

Monocytes-transformed into macrophages, the biggest leukocyte






-The third line of defense is acquired on an individual basis as each foreign substance is encountered by white blood cells called lymphocytes 



Stages of the network of immunology

  1. Lymphocyte development and differentiation 

  2. The presentation of markers (antigens) 

  3. Antigen challenge of B and T cells

  4. B cell response and T cell response 



Major Histocompatability complex (MHC)- a set of genes in mammals that produces molecules on surfaces of cells that differentiate among different individuals in the species. Has three classes

  1. Class 1- gene codes for markers that appear on all nucleated cells 

  2. Class 2- gene code for immune regulatory markers 

  3. Class 3- genes encode proteins involved with the complement system 



Thee immune system is responsible for…

  • Surveillance of the body 

  • Recognition of foreign material 

  • Destruction of anything foreign 



Antigen- any cell that induces a specific immune response by B cells or T cells and can stimulate resistance to an infection or toxin. 



Pathogen-associated molecular patterns (PAMP)- molecules on the surface of many types of microbes that are not present on host cells that mark the microbes as foreign.



Pattern recognition receptors (PRR)- molecules on the surface of host defense cells that recognize pathogen associated molecular patterns on microbes



Mononuclear phagocyte system- a collection of monocytes and macrophages scattered throughout the extracellular spaces that function to engulf and degrade foreign molecules 



Lymph- a plasma like fluid carried by the lymphatic circulation 



Skin-associated lymphoid tissues (SALT)- discrete bundle of lymphatic tissue located just under the surface of the skin 



Mucosa-associated lymphoid tissue (MALT)- small patches of lymphoid tissue situated in and on mucosal surfaces, containing T cells, B cells, phagocytes, and other immune cells 



Gut associated lymphoid tissue (GALT) - A collection of lymphoid tissue in the gastrointestinal tract that includes the appendix, the lacteals, and Peyer’s patches.


Whole blood- A liquid connective tissue consisting of blood cells suspended in plasma.


Pluripotential stem cells-  is a primary precursor of new blood cells, is a pool of undifferentiated cells 


Types of white blood cells 

Granulocytes- a mature leukocyte that contains noticeable granules in a wright stain 

*Neutrophils, eosinophils, and basophils

Agranulocytes- one form of a leukocyte having globular, non lobed nuclei and lacking prominent cytoplasmic granules. 




Cytokines- a chemical substance by white blood cells and tissue cells that regulates development, inflammation, and immunity 



  • B cells mature in red bone marrow, and T cells mature in the thymus 



Lysozyme- an enzyme found in sweat, tears, and saliva that breaks down bacteria peptidoglycan



Rubor- redness

Calor- warmth 

Tumor-swelling 

Dolor-pain 



Diapedesis- the migration of intact blood cells between endothelial cells of a blood vessel such as a venule 



Interferon- is a small protein produced naturally by certain white blood and tissue cells, is a type of cytokine

*three types, alpha, beta(stimulate phagocytes) and gamma (regulator of macrophages and T and B cells)



Natural killer cells- type of lymphocyte related to T cells that lack specificity for antigens. 



Dendritic cells- a type of phagocyte and immune cell that is found in tissues and boost immune responses by showing antigens on its surface 



Antimicrobial peptides- short protein molecules found in epithelial cells, have the ability to kill bacteria 



Immunogens- any substance that induces a state of sensitivity or resistance after processing by the immune system of the body 



B cells- a type of lymphocyte or white blood cell, produce antibodies and neutralize pathogens 



T cells- a type of lymphocyte or white blood cell, destroy infected or cancerous cells.



Major Histocompatibility complex (MHC)- a set of genes in mammals that produces molecules on surfaces of cells that differentiate among different individuals in the species 

-gives rise to glycoproteins called MHC molecules and is found on all cells but red blood cells 



Three classes of MHC genes have been identified:

  1. Class 1 genes- markers that appear on all nucleated cells 

  2. Class 2 genes- genes code for immune regulatory markers 

  3. Class 3 genes- genes encode proteins involved with the complement system 



Clone- a group of genetically identical cells



How T cells respond to antigens 

  1. Helper t cells help B cells to activate cytotoxic T cells (CD4 cells). The most prevalent type of T cell. 

  2. Regulatory T cells guard against excessive or inappropriate inflammation. Also carry CD4 markers.

  3. Cytotoxic T cells lead to the destruction of infected host cells. Can kill virally infected cells, cancer cells, and cells from other animals and humans  



How B cells respond to antigens

  • A B cell divides giving rise to plasma that releases the five classes of antibodies. 

  • Regulatory B cells regulate the degree of response from T cells 



Characteristics of good antigens 

-their chemical composition 

-their context

-their size 



Epitope- primary signal that the molecule is foreign 

Haptens-  a partial antigen, constitutes the determinative group and cannot stimulate a full immune response 

Alloantigens- cell surface markers that occur in some species but not others

Superantigens- bacterial toxins that are potent stimuli for T cells 

Cytokine storm- an overwhelming release of immune-modulating chemicals known as cytokines 



3 different cells that can serve as Antigen-presenting cells: APC

  1. Macrophages 

  2. B cells 

  3. Dendritic cells 



Cytotoxicity- is the capacity of certain T cells to kill a target cell



Apoptosis- genetically programmed death of cells that is both a natural process of development and the body’s means of destroying abnormal cells.  



Classes of Antibodies: 

IgG- a monomer of immunoglobulin, it is the most prevalent antibody, and  neutralizes toxins. The only antibody capable of crossing the placenta 



IgA- coats the surface of membranes and is found in saliva, tears, colostrum, and mucus 



IgM- composed of five monomers, binds antigens, circulates mainly in the blood 



IgD- found in miniscule amounts, main function is that it is the receptor for antigen on B cells



IgE- its role is to stimulate an inflammatory response, can lead to asthma and certain other allergies



Active Immunity- occurs when an individual received an immune stimulus that activates the B and T cells, causing the body produce antibodies 



Passive Immunity- occurs when an individual receives immune substances that were produced actively in the body of another human. 

Natural Immunity- ecompasses any immunity that is acquired during the normal biological experiences of an individual 


Artificial Immunity- protection from infection obtained through medical procedures