Chapter 10: Mechanisms of Infectious Disease

Question 1

Learning Objectivess

Answer 1

1 Microorganisms that cause infectious disease.
2 Mechanisms of infection and transmission
3 Diagnosis and treatment of infectious diseases

Question 2

Infectious disease

Answer 2

Infectious disease—the disease state caused by an organism

host has injury or pathologic damage

Question 3

Host

Answer 3

Host—any organism capable of supporting the growth of an organism
`

Question 4

Colonization

Answer 4

Colonization—the presence of a living organism on or within the host

isn’t always disease

Question 5

Microflora

Answer 5

Microflora—bacteria inhabiting exposed surfaces of the body

Question 6

Virulence

Answer 6

Virulence—the disease-inducing potential of a microorganism

“disease strength”

Question 7

Pathogens

Answer 7

umbrella term for microorganisms so virulent that they are rarely found in the absence of disease

Question 8

Saprophytes

Answer 8

microbio term: free-living organisms obtaining their growth from dead or decaying organic material from the environment
ie: yeast infection

Question 9

Mutualism

Answer 9

an interaction in which the microorganism and the host both derive benefits from the interaction

ie: gut bacteria

Question 10

Commensalism

Answer 10

an interaction in which colonizing bacteria acquire nutritional needs and shelter but the host body not affected

benefits bacteria, no effect on host

Question 11

Parasitic Relationship

Answer 11

only the infectingorganism benefits from the relationship

benefits infecting organism

Question 12

Agents of Infectious Disease: Viruses

Answer 12

Smallest pathogens

Have no organized cellular structure

Consist of a protein coat surrounding a nucleic acid core of DNA or RNA

incapable of replication outside a living cell
Some viruses enter the host cell and insert their genome into the host cell chromosome, where it remains in a latent, nonreplicating state for long periods without causing disease (i.e., HSV- cold sores, shingles).

Certain viruses also can transform normal host cells into malignant cells during the replication cycle- (oncogenic)- includes certain retroviruses and DNA viruses, such as the herpesviruses, adenoviruses, and papovaviruses.
Human papillomaviruses (HPVs), members of the papovavirus family, cause cutaneous and genital warts, and several genotypes are associated with cervical cancer.

Question 13

Agents of Infectious Disease: Bacteria

Answer 13

Prokaryotes (Bacteria) :
The nucleus is not separated. no organelles

veryyy Adaptable and can live in a range of environments

Classification:
- Gram-positive organisms: stained purple by a primary basic dye (usually crystal violet)
- Gram-negative organisms: not stained by the crystal violet but are counterstained red by a second dye (safranin)

Question 14

Agents of Infectious Disease: Fungi

Answer 14

Eukaryotes (Fungi)
-Contain a membrane-bound nucleus

fungi: free-living, eukaryotic saprophytes found in every habitat on earth
ie: yeast infections are opportunistic - when normal bacteria are destroyed it takes over

Diseases:
Incidental
Self-limiting
Skin and subcutaneous tissue

Question 15

Agents of Infectious Disease: Parasites

Answer 15

intestinal parasites that have immuno-regulatory role in the body. (good)

Types:
Protozoa
Helminths- wormlike
Arthropods- vectors of infection such as ticks and mosquitos

Method of Infecting:
These members of the animal kingdom infect and cause diseases in other animals.
These animals then transmit disease to humans.

Question 16

Epidemiology

Answer 16

the study of factors, events, and circumstances that influence thetransmission of infectious diseases among humans

Question 17

Incidence

Answer 17

the number of new cases of an infectious disease that occur within a defined population

Question 18

Prevalence

Answer 18

the number of active= cases at any given time

Question 19

Endemic

Answer 19

found in a particular geographic region

Question 20

Epidemic

Answer 20

Abrupt and unexpected increase inthe incidence of disease over endemic rates

Question 21

Pandemic

Answer 21

Spread of disease beyond continentalboundaries

Question 22

Source of ID: nosocomial

Answer 22

develop in hospitalized (any healthcare envt) patients

Question 23

develop in hospitalized patients: community acquired

Answer 23

acquired outside of health care facilities

Question 24

Modes of Transmission: Penetration

Answer 24

note: portals of entry do not dictate the site of infection

Question 25

Modes of Transmission: Direct Contact

Answer 25

Some pathogens are transmitted directly from infected tissue or secretions to exposed, intact mucous membranes. This is especially true of certain sexually transmitted infections (STIs), such as gonorrhea, syphilis, or chlamydia.

Question 26

Modes of Transmission: Ingestion

Answer 26

: A lot of bacterial, viral, and parasitic infections, including , food poisoning, traveler’s diarrhea, and hepatitis A, we get through the ingesting contaminated food or water.

Question 27

Modes of Transmission: Inhalation

Answer 27

breathe

Question 28

Factors Influencing the Site of an Infectious Disease: Agent

Answer 28

endogenous or exogenous origins of a pathogen

some are more virulent (strong)

Question 29

Factors Influencing the Site of an Infectious Disease: Host

Answer 29

An object or substance from which the infectious agent was acquired
-viral lode: how much of an infectious agent is there

Portal of entry

Competence of the host’s immunologic defense system
-more difficult to fight infection if ur already sick

Question 30

criteria of infectious disease diagnosis

Answer 30

ID the bug!
The recovery of a probable pathogen or evidence of its presence from the infected sites of a diseased host (proof)

Symptomatology
Accurate documentation of clinical signs and symptoms compatible with an infectious process

Question 31

Disease course in infection

Answer 31

Incubation period: latent infection in body, colonozied but no symptoms\

Prodromal stage: mild symptoms

Acute stage: peak

Convalescent stage: downslide

Resolution stage: pretty much back to normal

Question 32

Lab diagnosis

Answer 32

Culture: grow sample in lab for ID

Serology: detection of characteristic antigens of particular pathogen
- Antigen testing:
Antigen tests search the sample for viral proteins instead of the virus’s genetic code. Antigen tests are typically offeredat places where groups of people need testing fast. They’re a nasal swab as well and can be run quick - you can get results in as little as 15 min.- these are the “rapid tests” and thought to be less accurate than the PCR tests run in the lab.

Genomic sequences or metabolites produced by the pathogen
- DNA or RNA
*PCR -PCR used for C-diff. Real time . can detect as little as one virus
-Covid PCR test searches for the virus’s genetic material in a nasal swab or saliva sample, and it is often processed in a highly complex laboratory. There are two ways to collect a nasal sample: from the inside of a nostril, or from the back of the nose and throat. The second way, called a nasopharyngeal swab, requires a professional to probe more deeply into the nasal cavity to get the sample. Some testing sites may ask you to swab your nose or cheek yourself, or spit into a tube. Each of these collection methods creates a sample that can be analyzed with a PCR test.

Question 33

Medication Treatment

Answer 33

remove pathogen from host and repair pathological function

sometimes medication isn’t needed due to body’s defenses

Antibacterials
Antivirals
Antifungals
Antiparasitic