Chapter 10: Mechanisms of Infectious Disease Flashcards
Learning Objectivess
1 Microorganisms that cause infectious disease.
2 Mechanisms of infection and transmission
3 Diagnosis and treatment of infectious diseases
Infectious disease
Infectious disease—the disease state caused by an organism
host has injury or pathologic damage
Host
Host—any organism capable of supporting the growth of an organism
`
Colonization
Colonization—the presence of a living organism on or within the host
isn’t always disease
Microflora
Microflora—bacteria inhabiting exposed surfaces of the body
Virulence
Virulence—the disease-inducing potential of a microorganism
“disease strength”
Pathogens
umbrella term for microorganisms so virulent that they are rarely found in the absence of disease
Saprophytes
microbio term: free-living organisms obtaining their growth from dead or decaying organic material from the environment
ie: yeast infection
Mutualism
an interaction in which the microorganism and the host both derive benefits from the interaction
ie: gut bacteria
Commensalism
an interaction in which colonizing bacteria acquire nutritional needs and shelter but the host body not affected
benefits bacteria, no effect on host
Parasitic Relationship
only the infectingorganism benefits from the relationship
benefits infecting organism
Agents of Infectious Disease: Viruses
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.
Agents of Infectious Disease: Bacteria
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)
Agents of Infectious Disease: Fungi
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
Agents of Infectious Disease: Parasites
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.
Epidemiology
the study of factors, events, and circumstances that influence thetransmission of infectious diseases among humans
Incidence
the number of new cases of an infectious disease that occur within a defined population
Prevalence
the number of active= cases at any given time
Endemic
found in a particular geographic region
Epidemic
Abrupt and unexpected increase inthe incidence of disease over endemic rates
Pandemic
Spread of disease beyond continentalboundaries
Source of ID: nosocomial
develop in hospitalized (any healthcare envt) patients
develop in hospitalized patients: community acquired
acquired outside of health care facilities
Modes of Transmission: Penetration
note: portals of entry do not dictate the site of infection
Modes of Transmission: Direct Contact
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.
Modes of Transmission: Ingestion
: 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.
Modes of Transmission: Inhalation
breathe
Factors Influencing the Site of an Infectious Disease: Agent
endogenous or exogenous origins of a pathogen
some are more virulent (strong)
Factors Influencing the Site of an Infectious Disease: Host
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
criteria of infectious disease diagnosis
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
Disease course in infection
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
Lab diagnosis
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.
Medication Treatment
remove pathogen from host and repair pathological function
sometimes medication isn’t needed due to body’s defenses
Antibacterials
Antivirals
Antifungals
Antiparasitic
