BIO 2440 Exam 2

What is one major difference between virus and bacterium?

A virus needs a living host cell to multiply, bacterium does not

Do viruses have a plasma membrane?

No, but bacteria does

Does viruses contain both DNA and RNA?

No, they contain either but not both

Can viruses pass through bacteriological filters?

Yes, but bacteria cannot

Define Host Range

The spectrum of host cells in which a virus can multiply

What is host range determined by?

The specific receptor site on the host cell’s surface and the availability of host cellular factors

What to use to see viral size?

Electron microscopy

Virus range in length

20 to 1000 nm

Virion

extracellular infectious form of a virus

Capsid

Protein coat surrounding nucleic acid of a virus for protection

Envelope

lipid membrane that encloses capsids of some viruses made up of lipids, proteins, and carbohydrates

Spikes

carbohydrate-protein complexes that attach to host cells for replication

Pathology

scientific study of disease

Etiology

study of cause of disease

Infection

invasion or colonization of the body by pathogenic microorganisms

Disease

An abnormal state in which part or all of body is incapable of performing its normal function

Objectives of pathology?

Etiology, pathogenesis, morphology determine functional consequences

Microbial antagonism

Growth of some microbes prevent growth of other microbes

Commensalism

One organism benefits, other is unaffected

Mutualism

Both organisms benefit

Parasitism

One organism benefits at the expense of the other

Symbiosis

Relationship between normal microbiota and host

List Koch's postulates

• The same pathogen must be present in every case of the disease

• The pathogen must be isolated from the diseased host and grown in pure culture

• The pathogen from the pure culture must cause the disease when its inoculated into a healthy susceptible laboratory animal

• The pathogen must be isolated from the inoculated animal and must be shown to be the original organism

Exceptions to Koch's postulates

• Some pathogens can cause several disease conditions

• Some pathogens cause disease only in humans

• Some microbes have never been cultured

Symptoms

Changes in body function that are felt by a patient as a result of a disease

Signs

Changes in a body that can be measured or observed as a result of disease

Syndrome

Specific group of signs and symptoms that accompany a disease

Communicable disease

A disease that is spread from one host to another

Contagious disease

Diseases that are easily and rapidly spread from one host to another

Noncommunicable disease

Disease that is not spread from one host to another

Incidence

Number of people who develop a disease during a particular time period

Prevalence

Number of people who develop a disease at a specified time, regardless of when it first appeared

Sporadic disease

Disease that occurs only occasionally

Endemic disease

Disease constantly present in a population

Epidemic disease

Disease acquired by many people in a given area in a short time

Pandemic disease

Worldwide epidemic

Acute disease

Symptoms develop rapidly but disease lasts only a short time

Chronic disease

Symptoms develop slowly

Subacute disease

Intermediate between acute and chronic

Latent disease

Causative agent is inactive for a time but then activates and produces symptoms

Herd immunity

Immunity in most of population

Local infection

Pathogens are limited to a small area of the body

Systemic infection

Infection throughout the body

Focal infection

Systemic infection that began as local

Sepsis

Toxic inflammatory condition arising from spread of microbes, especially bacteria or their toxins, from a focus of infection

Bacteremia

Bacteria in the blood

Septicemia

Growth of bacteria in blood

Toxemia

Toxins in blood

Viremia

Viruses in blood

Primary infection

Acute infection that causes initial illness

Secondary infection

Opportunistic infection after a primary infection

Subclinical disease

No noticeable signs or symptoms

What makes the body more susceptible to disease?

Gender, age, genetics, climate, lifestyle

Incubation period

Interval between initial infection and first signs and symptoms

Prodromal period

Short period after incubation; early, mild symptoms

Period of illness

Disease is most severe

Period of decline

Signs and symptoms subside

Period of convalescence

Body returns to its original state

Indirect contact transmission

Spreads to a host by a nonliving object called a famine

Vehicle transmission

Transmission by an inanimate reservoir

• waterborne, roodborne, airborne

Vectors

Fleas, ticks, mosquitoes

Mechanical transmission

Pathogen is carried on vector's feet

Biological transmission

Pathogen reproduces in vector (bite)

Compromised host

Individual whose resistance to infection is impaired by disease, therapy, or burns

Contributing to emerging infectious diseases?

• Genetic recombination

• New strains

• Widespread use of antibiotics and pesticides

• Changes in weather

Epidemiology

Study of where and when diseases occur and how they aretransmitted in populations

Descriptive epidemiology

Collection and analysis of data

Analytical epidemiology

Analyzes a particular disease to determine its probable cause

Experimental epidemiology

Involves a hypothesis & controlled experiments

Morbidity

Incidence of a specific notifiable disease

Mortality

Deaths from disease

Notifiable infectious disease

Disease in which physicians are required to report occurrence

Where is normal microbiota usually found?

Most directly exposed areas

Health care professionals who fail to use aseptic techniques can cause__

Nosocomial infections

What period is shortened if more microorganisms are present in the infective dose

Incubation period

An example of descriptive epidemiology is

John Snow’s study of the London cholera outbreak from 1848 to 1849

Pathogenicity

the ability to cause disease

Virulence

the degree of pathogenicity

Pathogenicity

Ability to cause disease by overcoming host defenses

Portals of entry for pathogens

• Mucous membranes

• Skin

• Direct deposition beneath the skin or membranes

ID 50

Infections dose for 50% of sample population

LD 50

Lethal dose for 50% of sample population

Adherence

Pathogens attach to host tissues

How to know what toxin is the most lethal?

More toxin it takes to cause disease, less potent toxin is

What does m protein do in cell wall?

Resists phagocytosis

What does opa protein do in cell wall?

Allows attachment to host cells

What does waxy lipid do in cell wall?

Resists digestion

Enzyme coagulates

Coagulate fibrinogen

Enzyme kinases

Digest fibrin clots

Hyaluronidase enzyme

Digests polysaccharides that hold cells together

Enzyme collagenase

Breaks down collagen

Enzyme lgA proteases

Destroy IgA antibodies

Invasions

Surface proteins produced by bacteria that rearrange actin filaments of cytoskeleton

Siderophores

Proteins secreted by pathogens that bind iron more rightly than host cells

Direct damage of Siderophore's

• Disrupts host cell function

• Uses host cell nutrients

• Produces waste products

• Multiplies in host cells and causes ruptures

Toxins

Poisonous substances produced by microorganisms

Toxigenicity

Ability of a microorganism to produce a toxin

Toxemia

Presence of toxin in host's blood

Intoxication

Presence of toxin without microbial growth

Exotoxins

Proteins produced and secreted by bacteria