Good physical health

Mental health – if you believe that you’re not healthy you are more susceptible to getting sick.

Spiritual – people who are religious/spiritual tend to be more upbeat, positive, optimistic etc…

Pathogenic – disease causing Opportunistic pathogen – isgenerally harmless in its normal habitat but can become

pathogenic in a host who is seriously debilitated or has a weak immune system.

◦ Ex. – pneumocytsis carnii – will cause pneumonia in AIDS patients

 

Virulent – Has a very high degree to cause infection

◦ Ex. – Ebola (80% mortality)

Which is more virulent?  

E. coli 0157H7 – pathogen (found in burgers at Jack-in-the-Box)

or

E. coli in Felix’s gut

Note: E. coli in Felix’s gut is an opportunistic pathogen. Has the ability to cause an infection but it has to be in the right conditions/environment like a sterile site.

The area in which a microorganism enters the body. They may be cuts, lesions, injection sites, or natural body orifices

◦ Four major pathways Skin Mucous membranes Placenta Parenteral route

◦ Contamination – the mere presence of microbes in or on the body

◦ Infection – results when the organism has evaded the body’s external defenses, multiplied, and become established in the body

◦ Skin Outer layer of packed,

dead, skin cells usually acts as a barrier to pathogens

Some pathogens can enter through openings or cuts

Others enter by burrowing into or digesting the outer layers of skin

◦ Mucous membranes Line the body cavities

that are open to the environment

Provide a moist, warm environment that is hospitable to pathogens

Respiratory tract is the most common site of entry – entry is through the nose, mouth, or eyes

Pathogens able to survive the acidic pH of the stomach may use the gastrointestinal tract as a route of entry

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Diseases

Cystic fibrosis Cancer Diabetes Cardiovascular heart disease

(CHD) Mental diseases (depression) Alcoholism Autoimmune (Lupus)

Infection

Cellulitis (pyoderma) pharyngitis conjuctivitis pneumonia cystitis otitis media vaginitis Colitis Gastritis encephalitis

A harmful alteration of host tissues (arthritis) or metabolic processes(Diabetes/hyperglycemia.)

Causation of Disease: Etiology◦ Study of the cause of

disease◦ Germ theory of disease –

disease caused by infections of pathogenic microorganisms

◦ Robert Koch developed a set of postulates one must satisfy to prove a particular pathogen causes a particular disease

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Entry, manifestation, proliferation of an infectious agent within a host.

Infectious agent has to enter, begin to grow and continue grow in host tissues.

Infectious diseases have been linked to otherDiseases

HPV cervical cancer H. Pylori gastric cancer Hepatitis B liver cancer

Microorganism must enter host tissues.

Microorganism must establish itselfand begin to propagate (grow)

Microorganism must have access to Nutrients

If one of these three processes is not

met an infection will not manifest In host tissues.

◦ Ex. – HIV needs nutrients (T4 helper) in order to propagate.

Effects on the body by a toxin produced by a biological agent.

Enterotoxin F is produced by Staphylococcus aureus, causes toxic shock

syndrome.

Difference Between food Poisoning and Foodborne Infecton

 Condition Time until sick Length (process)

Symptoms  

Intoxication by S. aureus 4 hours 24 hours Vomitingfood poisoning) Infection by Salmonella 3-14 days until treated Cramps(food borne illness) Fever

Diarrhea

Dehydration

Tenesmus

Stool sample is taken to look for infectious agent then treated with antibiotics.

A pathogen (infectious agent) or (more commonly) germ, is a biological agent that causes disease or illness to its host.

There are several molecules that microorganisms produce that allows invasion into tissues or a means to exert its pathological affect on the body.

Virulence factors are molecules expressed and secreted by pathogens (bacteria, viruses, fungi and protozoa) that enable them to achieve the following:

colonization of a niche in the host (this includes adhesion to cells)

evasion of the host's immune response

entry into and exit out of cells (if the pathogen is an intracellular one)

obtain nutrition from the host.

◦ Pathogenicity – ability of a microorganism to cause disease

◦ Virulence – degree of pathogenicity Virulence factors

contributing to an organism’s virulence Adhesion factors Biofilms Extracellular enzymes Toxins Antiphagocytic factors

Virulence factors are very often responsible for causing disease in the host as they inhibit certain host functions.

Pathogens possess a wide array of virulence factors.

Some are intrinsic to the bacteria (e.g. capsules and endotoxin) whereas others are obtained from plasmids (e.g. some toxins).

◦ Process by which microorganisms attach themselves to cells

◦ Required to successfully establish colonies within the host

◦ Uses adhesion factors Specialized structures Attachment proteins

◦ Toxins Chemicals that harm

tissues or trigger host immune responses that cause damage

Toxemia refers to toxins in the bloodstream that are carried beyond the site of infection

Two types Exotoxins Endotoxins

The endotoxin is the lipopolysaccharide

(LPS), which is part of the bacterial cell wall of Gram-negative bacteria.

It is the Lipid A component of the LPS that has the toxic properties.

The LPS is a very potent antigen and, as a result, stimulates an intense host immune response. As part of this immune response cytokines are released which cause the fever and other symptoms seen during disease.

If a high amount of LPS is present then septic shock (or endotoxic shock) may result which, in severe cases, can lead to death.)

Exotoxins, on the other hand, are actively secreted by some bacteria and have a wide range of affects including inhibition of certain biochemical pathways in the host.

The two most potent exotoxins known to man

are the tetanus toxin (tetanospasmin) secreted

by Clostridium tetani and the botulinum toxin secreted by Clostridium botulinum.

Exotoxins are also produced by a range of other bacteria including Escherichia coli; Vibrio cholerae (causative agent of cholera); Clostridium perfringens (causative agent of food poisoning as well as gas gangrene) and Clostridium difficile (causative agent of pseudomembranous colitis).

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Microorganisms can producenumerous enzymes (proteins that break down substances)

Lipase – breaks down oleic acids which has many antimicrobial properties and protects our skin.◦ Produced by Staphylococcus

Coagulase – coagulates plasma◦ produced by Staphylococcus aureus

Hyaluronidase – known as “spread factor.” Hyaluronic acids holds cells together and Hyaluronidase destroys the cement that holds the tissues together.◦ Produced by Streptococcus pyogenes

and Staphylococcus aureus

◦ Extracellular enzymes Secreted by the

pathogen Dissolve structural

chemicals in the body Help pathogen

maintain infection, invade further, and avoid body defenses

The body contains many natural orders of defense against some of the common pathogens in the form of the human immune system and

bysome "helpful" bacteria present in

the human body's normal flora.

Figure 14.1

◦ Skin (largest organ of the body)

◦ Mucous membranes – openings to body (ears, mouth, anus, urethra)

Figure 14.2

Sneeze Cough Lacrimation (tears) Sweat Ear wax Salivation Defecation Peristalsis –

movement of food material in the intestinal tract

Figure 14.3

• Sebaceous secretions and specialized glands- antimicrobial

• Lysozyme in tears• Lactic acid and electrolyte

concentrations of sweat• Skin’s acidic pH and fatty

acid content• HCl in the stomach• Digestive juices and bile in

the intestine• Semen- antimicrobial

chemical• Acidic pH in the vagina

Complement cascade – entire immune system is turned on

Functions – neutralizes viruses, enhances phagocytosis, damages plasma membrane, can destroy (lyse) microorganism

At least 26 blood proteins that work in concert to destroy bacteria and certain viruses

Cascade reaction Three different pathways that all yield

similar end results◦ Classical pathway◦ Lectin pathway◦ Alternative pathway

Antiviral properties – good in fighting cancer and viruses

Body produces minute amounts

Interferes with transcription and translation of mRNA

• Interferon (IFN): involved against viruses, other microbes, in immune regulation and intercommunication

• Three major types– Interferon alpha– Interferon beta– Interferon gamma

• All three classes produced in response to viruses, RNA, immune products, and various antigens

• Bind to cell surfaces and induce changes in genetic expression• Can inhibit the expression of cancer genes and have tumor

suppressor effects

Figure 14.18

Normal flora – bacteria or plants. These organisms are with you for your entire life. They keep infectious pathogens in check.

Natural resistance –resistance you’ve acquired throughout your life (adult) Resistance acquired from mother (child.)

Immunology: the study of all features of the body’s second and third lines of defense

Healthy functioning immune system is responsible for:◦ Surveillance of the body◦ Recognition of foreign material◦ Destruction of entities deemed to be foreign

White blood cells must distinguish self from nonself cells

Evaluates cells by examining markers on their surfaces

Figure 14.4

White blood cells

◦ B lymphocytes◦ T lymphocytes