Chapter 10, Infection Flashcards
What are significant causes of death and morbidity related to infections?
Emergence of previously unknown infections, reemergence of old infections thought to be controlled, and the development of infections resistant to multiple antibiotics or vaccination.
What constitutes the normal microbiome of the human body?
Microorganisms that grow and flourish in the human body.
How is beneficial homeostasis maintained between humans and microorganisms?
Through the physical integrity of the gut and mechanisms that sequester microorganisms on the mucosal surface.
What can alter the symbiotic relationship with the normal microbiome?
Injury that compromises protective barriers including the skin and mucous membranes.
What are the four distinct stages of clinical infectious disease?
- Incubation period 2. Prodromal state 3. Invasion period 4. Convalescence.
What is the hallmark of most infectious diseases?
Fever, with body temperature regulated at a higher than normal level.
What factors influence a pathogen’s capacity to cause disease?
Communicability, immunogenicity, infectivity, mechanisms of action, pathogenicity, entry portal, toxigenicity, and virulence.
How are infectious diseases classified by prevalence and spread?
As endemic, epidemic, and pandemic.
What are the steps involved in the process of infection?
Colonization, invasion, multiplication, and dissemination.
What type of infections can occur when an individual’s immune system is deficient?
Opportunistic infections.
What can true pathogens do in adequate numbers?
Circumvent an individual’s defenses and directly cause infection.
Where do infectious microorganisms usually exist?
In reservoirs such as contaminated soil, contaminated water or food, breast milk, animals, or other humans.
How can pathogens be transmitted directly?
Through direct physical contact, ingestion or inhalation, or placental transfer.
What is indirect transmission of pathogens?
Occurs from contact with contaminated materials, ranging from towels to food or through a vector.
How do microorganisms stabilize adherence to tissue?
Through surface receptors during colonization.
Why do most microorganisms undergo rapid multiplication in tissue?
Because tissue is warm and nutrient-rich.
What are some virulence factors required for successful spreading?
Adhesion molecules, toxins, and the ability to evade immunity.
What can mixed species of microorganisms form?
Slimy biofilms that anchor themselves to surfaces and resist immune defenses.
What is required for stable colonization of bacteria?
Adhesion, often through pili, surface glycoproteins, or complement-related receptors.
What happens during invasion regarding defense mechanisms?
Direct confrontation with an individual’s defense mechanisms can result in bacteremia, viremia, or fungemia and sepsis.
How can bacteria protect against phagocytosis?
By producing toxins that destroy phagocytic cells and extracellular enzymes that digest immune molecules.
What classes of infectious microorganisms exist?
Bacterial, fungal, parasitic, protozoal, and viral.
How are bacteria categorized?
Into groups such as true bacteria, filamentous, spirochetes, mycoplasma, rickettsia, and chlamydia, and as gram negative or gram positive.
What specialized surface structures do many bacteria have?
Pili and flagella that promote adhesion and tissue invasion.
What types of toxic molecules can bacteria produce?
Toxins that may kill cells, disrupt tissue, and protect against inflammation.
What are exotoxins?
Toxins released by bacteria during growth that can damage cell membranes and inhibit protein synthesis.
What are endotoxins?
Contained in the cell walls of gram-negative bacteria and released during lysis, activating inflammation and producing fever.
What can excessive inflammatory and immune responses cause?
Tissue damage through excessive cytokine production and infiltration of immune cells.
What self-protective mechanisms do bacteria have?
Degradation of immune molecules, neutralization of immune molecules, complement evasion, immune suppression, and escape from the phagosome.
How can some bacteria proliferate rapidly?
More rapidly than the development of immune defenses, causing severe clinical disease.
How do some bacteria evade immune defenses?
By surviving inside immune cells.
What can some bacteria do to the Fc portion of antibodies?
Coat it, preventing complement activation or phagocytosis.
What is antigenic variation?
The ability of pathogens to alter surface molecules to evade immune responses.
How can some bacteria damage tissue?
By releasing molecules that bind to and neutralize antibodies or form immune complexes that deposit in tissue.
What can some bacteria degrade?
Immunoglobulins or components of the complement system.
How can some bacteria suppress immune responses?
By blocking T cells or impairing inflammatory signals.
What is a major cause of hospital-acquired infections?
S. aureus, which has numerous virulence factors promoting invasive infection.
What is a fungal infection called?
Mycosis.
How are most pathologic fungi transmitted?
By human-to-human contact, inhalation, or contamination of wounds.
What do fungi have that promotes adhesion to epithelial tissue?
Polysaccharide surface molecules.
What toxins can fungi produce?
Toxins that promote infection, evade immune responses, or cause cancer (e.g., aflatoxins).
What can some fungi secrete that damages tissue?
Enzymes that initiate pathogenic inflammatory responses, including hypersensitivity reactions.
How do some fungi resist lysosomal destruction?
By surviving in phagocytes.
What is the most common cause of fungal infections in humans?
C. albicans, which resides in various body sites and can remain localized in individuals with an intact immune system.
What do parasitic organisms establish with another species?
A symbiosis where the parasite benefits.
How do parasites penetrate and enter the circulatory system?
By adhering to and breaking down connective tissue and basement membranes.
What are obligatory intracellular parasites?
Parasites that only reproduce within host cells.
How do some parasites evade immune defenses?
By secreting cytotoxic molecules or through antigenic variation.
What is malaria and how is it transmitted?
One of the most common infections worldwide, transmitted through the bite of an infected Anopheles mosquito.
What is the viral life cycle?
Attachment, penetration, uncoating, replication, assembly, and release of new virions.
How are viruses classified?
By the format of nucleic acid in the virion (RNA or DNA) and whether they use reverse transcriptase for replication.
What mechanisms do successful viruses use to bypass immune rejection?
Rapid division, intracellular survival, coating with self-proteins, antigenic variation, neutralization, complement evasion, and immune suppression.
What harmful effects can viruses have inside infected cells?
Inhibition of DNA, RNA, or protein synthesis; disruption of lysosomal membranes; promotion of apoptosis; and alteration of antigenic properties.
What is an example of a viral infection?
Influenza, an ssRNA virus transmitted through aerosol and body fluids, with variant forms that undergo antigen shifts.
What is AIDS?
AIDS is a viral disease caused by HIV.
How does HIV affect the immune system?
HIV infects and depletes a portion of the immune system (Th cells), making individuals susceptible to life-threatening infections and malignancies.
What is the global impact of HIV/AIDS?
HIV/AIDS remains a major cause of death worldwide.
What has helped stabilize HIV/AIDS cases in the U.S.?
Aggressive antiretroviral therapy and public health campaigns have stabilized the number of new cases and deaths in the United States from HIV/AIDS.
How is HIV transmitted?
HIV is a blood-borne pathogen present in body fluids with typical routes of transmission: blood or blood products, intravenous drug abuse, heterosexual and homosexual activity, and maternal-child transmission before or during birth.
What is the primary surface receptor on HIV?
The primary surface receptor on HIV is the envelope glycoprotein gp120, which binds to the CD4 molecule found mostly on the surface of T-helper cells.
What family does HIV belong to?
HIV is a member of the retrovirus family, which carries genetic information in the form of RNA.
What enzymes are involved in HIV replication?
An enzyme, reverse transcriptase (RT), converts RNA into double-stranded DNA, and another enzyme, integrase, inserts the new DNA into the infected cell’s genetic material.
What is a major immunologic finding in AIDS?
The major immunologic finding in AIDS is the striking decrease in the number of CD4+ Th cells.
What indicates infection by HIV?
The presence of circulating antibody against HIV indicates infection by the virus, although many individuals are asymptomatic.
What is the current treatment for HIV infection?
The current treatment for HIV infection is a combination of drugs called highly active antiretroviral therapy (HAART) that attacks different portions of the viral replication pathway.
How has mother-to-child transmission of HIV been reduced?
Mother-to-child transmission has been reduced to 1% with prenatal treatment of HIV infection.
How can neonates become HIV infected?
Neonates become HIV infected by placental transmission or through breast-feeding.
What increased risk do children with HIV face?
Children with HIV are at increased risk of coronary artery disease.
What are effective means of countering infectious microorganisms?
Effective means include rigorous use of environmental infection control measures, control of insect vector populations, modern sanitation facilities, and provision of clean water and uncontaminated food supplies.
What is passive immunotherapy?
Passive immunotherapy has been effective using previously formed human immunoglobulin for diseases such as hepatitides A and B, rabies, and ebola.
What is the focus with antibiotic-resistant pathogens?
With antibiotic-resistant pathogens, a greater emphasis is placed on the development of new vaccines.
