Ch 14 Mechanisms of Infectious Disease Flashcards
Terminology of Infectious Disease
What is Host, Infection, Colonization, Microflora, commensalism, Mutualism, parasitic relationship, infectious disease, virulence, pathogens,
Host - any organism capable of supporting the nutritional and physical growth requirement of another.
Infection - describes the presence and multiplication within another living organism, with subsequent injury to the host.
Colonization describes the act of establishing a presence.
Microflora - the internal and external exposed surfaces of the human body are normally and harmlessly inhabited by a multitude of bacteria
commensalism - although the colonizing bacteria acquire nutritional support from the hose, the host is not adversely affected by the relationship.
Mutualism - is applied to an interaction in which the microorganism and the host both derive benefits from the interaction
Parasitic relationship - is one in which only the infecting organism benefits from the relationship and the host either gains nothing from the relationship or sustains injury from the interaction.
Infectious disease - occurs if the host sustains injury in a parasitic relationship.
Virulence - severity of an infectious disease can range from mild to life threatening depending on many variables, including the health of the host at the time of infection.
Pathogens - are so virulent that they are rarely found in the absence of disease.
What are prions? What are they? What are the characteristics? What are the treatment and disease?
Protein particles that lack any kind of a demonstrable genome, has never RNA or DNA that codes for the production of essential proteins.
Creutzfeldt-Jakob disease in humans, chronic wasting disease in deer and elk, scrapie in sheep, and bovine spongiform encephalopathy (mad cow) in cattle.
All have the same transmissible neurodegenerative diseases.
Characterized by slowly progressive, noninflammatory neuronal degeneration leading to loss of coordination (ataxia), dementia, and death over a period from months to years.
Because we dont understand how they multiply or are. They easily spread within the axons of the nerve cells causing progressively greater damage to host neurons and eventual incapacitation of the host. The current antimicrobial agents are useless against them.
What are viruses? What are their characteristics? What are retroviruses?.
Viruses are the smallest obligate intracellular pathogens. Have no organized cellular structures byt instead consist of a protein coat, or capsid, surrounding a nucleic acid core, or genome, of RNA or DNA, never both.
Enveloped means buds pinched from the cell membrane, are continuously shed from the infected cell surface. Such as herpsevirus group, influenza and poxviruses.
Viruses are incapable of replication outside of a living cell. Must penetrate a susceptible living cell and use the biosynthetic machinery of the cell to produce viral progeny.
Retroviruses are HIV - after entry into the host cell the viral RNA genome is first translated into DNA by the viral enzyme reverse transcriptase. It is then integrated into the host chromosome where it exists in a latent state. In HIV is regulates the immunologic defense system and leads to permanent suppression of the immune response.
What is bacteria? What are the classes? What is gram positive and negative?
Bacteria are autonomously replicating unicellular organisms known as prokaryotes because they lack an organized nucleus. Contain both DNA and RNA although it is considerably smaller and is typically encoded on a single chromosome. It replicates simply and divides. Usually produce structured communities called biofilms which permit access to available nutrients and elimination of metabolic waste. Ex human mouth, indwelling medical devices, on human cells.
They have a well defined set of growth parameters, including nutrition, temperature, light, humidity, and atmosphere and are fastidious. ex. aerobes cant live without oxygen, anaerobes cant survive in oxygen.
Gram positive stains purple by basic dye, if they dont stain then are counter stained by red and are gram negative. Another class is acid-fast stain which is where a acid is added to already stained bacteria. So many they have genus and then a species within. ex staphylococcus (genus) aureus (species).
What are spriochetes and mycoplasmas?
Are gramnegative, helical long bacteria. Many different varieties, but spread from urine, insect bite such as lyme disease or person to person contact such as syphilis .
Mycoplasmas are unicellular prokaryotes capable of independent replication. One third the size with no cell wall so can change its appearance.
What are rickettsiaceae, anaplasmataceae, chlamydiaceae, and coxiella?
Combines the characteristics of both viral and bacterial agents to produce disease. All are intracellular pathogens but produce a rigid cell wall, reproduce asexually by cellular division and contain RNA and DNA.
Rickettsiaceae and chlamydiaceae are structurally similar and are transmitted directly between susceptible vertebrates without an insect host. Include sexually transmitted disease, ocular infection and pneumonia in newborns, upper and lower respiratory infection in children to young adults.
Anaplamatceae are intracellular and produce a number of veternary and human diseases some of which have a tick vector. They are independent on the host cell for energy production. From mild to lifethreatening. Mani - malaise, anorexia and nausea, fever and headache. Dec WBC and platelets. Severe respiratory failure, encephalopathy and acute renal failure.
Coxiella only one, is gram negative intracellular infects animals. In humans produces a disease called Q fever, nonspecific febrile illness often with headache, chills, arthralgias and mild pneumonia. Transmitted to humans when animal tissue is aerosolized or ingested with milk.
What is fungi?
Free-living, eukaryotic saprophytes found in every habitat on earth. some members are part of the normal human flora, Most dont cause disease in humans. Most are skin and subcutaneous tissue. Serious infections are from puncture wounds or inhalation. They can be life threathening opportunistic when host defense have been disabled.
Yeast -(candida albicans) smooth waxy or creamy in texture
Molds are powdery or cottony colonies. Mycelium penetrate the growth surface and project roots and produce a rigid cell wall.
What are parasites? What are protozoa, helminths and arthropods?
Parasites have changed to member of the animal kingdom that infect and cause disease.
Protozoa - are unicellular animals with a complete complement of eukaryotic cellular machinery. Reproduction may be sexual or asexual. Most are saprophytes but a few have adapted to human environment and produce diseases, malaria, amebic dysentery, and giardiasis. Can be passed sexually, contaminated water or food, or insect. Most are ingestion of contaminated by feces of infected host. They are usually motile by means of flagella, cilia or ameboid motion.
Helminths - wormlike parasites, they reproduce sexually within the definitive host, some require immediate host for maturation of offspring. Through ingestion of fertilized eggs or the penetration of infectious larval stages through the skin with insect.
Arthropods - mosquitoes, mites, chiggers, lice and fleas. Directly by contact with mature or immature forms of the insect and its eggs by clothing, bedding or grooming articles. Are vectors for infectious diseases typhus and bubonic plague.
The epidemiology of infectious diseases? Portal of entry? Source?
Epidemiologists working in infectious disease study the factors, events, and circumstances that influence the transmission of infectious diseases among humans. To devise strategies that interrupt or eliminate the spread.
Penetration - any disruption in the bodys surface barrier is a potential site for invasion
Direct contact - from infected tissue or secretions to exposed, intact mucous membranes.
Ingestion - through the oral cavity of gi tract.
Inhalation- respiratory tract
Source refers to location, host, object or substance from which the infectious agent was acquired. Can be from inside the host own microbial flora or outside from the environment. Zoonoses are from animal to human.
What are mechanisms of disease production? Virulence factors?
Toxins- substancs that alter or destroy the normal function of the host or host’s cells. two types endotoxins and exotoxins. LPS lipopolysaccharides in the cell wall of gram negative bacteria. Can induces many important cytokines, but at high levels can precipitate septic shock, DIC and ARDS. Exotoxins - proteins released from the bacterial cell during growth. Inactivate or modify key aspects of host cell structure or function.ex diptheria, botulism - dec the release of neurotransmitter causing flaccid paralysis. Some enterotoxins produce vomiting and diarrhea.
Adhesion factors - the pathogen must be able to attach and colonize the host. Many viral agents, such as influenza, mumps, measles, and adenovirus produce hair like appendages.
Evasion Factors - evading the host immune system. extracellular polysacchaarides, capsules, slime and mucous layers like influenza B. Some excrete leukicidin C toxins which causes specific and lethal damage to the cell membrane of the host neutrophils and macrophages. Salmonellosis and others can survive and reproduce within the WBC phagocytic. Some surface protein to evade IgG. Lyme disease alter surface antigens to avoid detection.
Invasion factors - enzymes capable of destroying cell membranes, connective tissue, intercellular matrices, and structural protein.
What are clinical presentation? Signs or symptoms? Sites of infection? Disease course?
Symptoms are the outward expression of the struggle between invading organisms and the retaliatory inflammatory immune responses of the host.
Site of infection is usually designated by adding the suffix itis to the name like bronchitis. These are usually applied to inflammation from infectious and noninfectious agents. -emia is used to designate the presence of a substance in the blood ex bacteremia, viremia. Determined by the type of pathogen, portal of entry and competence of the host’s immune defense system.
Disease course - are the stages after the potential pathogen enters the host. Incubation - the pathogen begins active replication without producing recognizable symptoms in the host. Prodromal stage - is the symptoms in the host - mild fever, myalgia, headache, and fatigue. Acute Stage - experiences the max impact of the infectious process. Convalescent period - by containment of infection, progressive elimination of pathogen and repair of damaged tissue. Resolution
What is diagnosis of infectious diseases?
Culture refers to the propagation of the microorganism outside of the body, usually on or in artificial growth media. Identification based on a microscopic appearance and gram stain reaction, shape, texture and color, by a panel of biochemical r
Serology - the study of serum - antibody titer - against a specific pathogen rises during the acute phase and falls during convalescence.
Protein detection - mass spectrometry is a technique for determining composition of a sample
DNA and RNA detection - DNA probe hybridization - small fragments of DNA are cut from the genome of a specific pathogen and labeled with compounds that allow detection. polymerase chain reaction allow technicians to tag a segment of pathogen DNA and then multiply it to detectable levels.
DNA sequencing - is Sanger sequencing uses nucleotides to build a chain of DNA
Treatment of infectious diseases Antibacterial agents? Antiviral agents? antifungal agents? surgical interventions?
Antibiotics are actually produced by other microorganisms, primarily bacteria and fungi, as by products of metabolism and usually only effective against other prokaryotic organisms. Bactericidal if it causes irreversible and lethal damage to the bacterial pathogen. Bacteriostatic if its inhibitory effects on bacterial growth are reversed when the agent is eliminated.
4 mechanisms interference in bacterial cell wall synthesis, inhibition of bacterial protein synthesis interruption of nucleic acid synthesis and interference with normal metabolism.
Antiviral- only recent, biggest is host toxicity. All are synthetic and target viral RNA or DNA synthesis. Like acyclovir. These mimic the nucleoside building blocks of RNA and DNA. In response to the AIDS epidemic.
ANtifungal agents - target two most important families is cytoplasmic membranes of yeasts or molds.
Surgical - as a last resort option to prevent demise of the host. By drainage of an abscess, debridement, or removing infected organs appendectomy.
