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ch 8
Infection and Infectious Diseases
| p | |
|---|---|
| Symbiosis | to two or more different organisms that live together in close physical association |
| Host | A larger organism that harbors smaller organisms and provides a living environment for those organism |
| Humans have symbiotic relationships with many different types of microbes. | True |
| different type of symbiosis | Mutualistic, Commensalism, Amensalism, Parasitism |
| Pathogens | Disease causing parasites (bacteria, viruses, protozoa, fungi, helminths) |
| true pathogens | Pathogens that can cause disease even in healthy adults |
| opportunistic pathogens | Pathogens that can only cause disease under certain circumstances |
| A human host has ingested Salmonella enterica bacteria which colonize in the small intestines but in the process secrete toxins that destroys the human enterocytes causing fever, chills, and gastroenteritis. | Parasitism |
| Bacteria found on human skin that feed on dead skin cells without harming the human host is an example of which type of symbiosis? | commensalism |
| Bacteria living in the human colon that help with food metabolism and provide microbial antagonism to prevent pathogens from colonizing that region is an example of which type of symbiosis? | mutualism |
| What are the two origins of microbes as they relate to humans | Exogenous and Endogenous |
| Endogenous | found in the body, normal microbiota (all microbiota found in nonsterile areas of body) different types of microorganisms. Skin, digestive tract, eyes, ears, nose, anything that is exposed to outside environment is non sterile |
| Exogenous | Found outside of body in one of major reservoirs, more pronounced causing disease, body not acclimating to dealing with them |
| Microbes that are found already inside the body are considered | endogenous microbes |
| Organisms that colonize the body’s surfaces without normally causing disease | normal human microbiota/ normal flora, endogenous microbiota |
| The collection of all the normal microbiota in a human that normally do not cause disease | Human microbiome |
| types of microbiota | resident and transient |
| resident | Type of endogenous microbiota, may inhabit host body for many years to a lifetime, are commensals (although can be mutualistic or opportunistic) found in non-sterile sites |
| transient | short lived, under right circumstances lead to disease both of these. Some can produce virulence factors, type of endogenous microbiota |
| sterile site | internal organs, tissue, and body fluids |
| non-sterile site | ex: skin and mucous membranes: URT, DI, UG tract, Eyes, Ear canals |
| Resident microbiota typically last how long in their host | years to an entire ;lifetime |
| Most resident microbiota exhibit which type of symbiosis with humans | commensalism, but can be mutualistic or opportunistic |
| Are resident microbiota found in sterile sites or non-sterile sites of the body | non-sterile |
| five major location where resident microbiota are found | skin and mucous membranes: eyes, GI tract, ear canals, UI, URT |
| four main ways that resident microbiota is obtained | rupture of placenta/ amniotic sac is breached, first breath, first meal, first contact with humans |
| Transient microbiota typically last how long in their host | Minute to weeks at most |
| Most transient microbiota exhibit which type of symbiosis in human | commensalism, although some may be mutualistic or opportunistic |
| Are transient microbiota found in sterile sites or non-sterile sites of the body | non-sterile sites |
| five major location where transient microbiota are located | same as resident (skin, mucous membrane: eyes, ear canals, UGI, GI, URT) |
| three main ways that transient microbiota is obtained | 1. Breathing 2. Eating 3. Physical contact |
| three reasons why transient microbiota cannot persist in the body for long periods of time | 1. Because they are outcompeted with other microorganisms ex: microbiota taking up attachment sites 2. Elimination of body defense cells, are not able to bypass immune system 3. Chemical or physical changes in body kill off such as pH |
| Both resident and transient microbiota are | opportunistic pathogens: |
| microbiota that don’t typically cause disease but may cause disease under the right circumstances | opportunistic pathogens: |
| What are four conditions how normal microbiota can become opportunistic pathogens? | 1. introduction into unusual sites in the body ex: sterile sites, 2. Immune suppression 3. Changes in normal microbiota: issue with taking broad range antibiotic that wipe out many healthy bacteria 4. Underlying diseases 5. Old age |
| exogenous microbes | Microbes that are originate outside the body in reservoirs |
| Sites where pathogens are maintained as a source of infection | reservoirs of infection, pathogens cannot survive long outside of host |
| the three types of reservoirs of infection | 1. Animal reservoirs 2. Human carriers: sick humans 3. Nonliving reservoirs |
| Diseases that naturally spread from animal host to humans | zoonoses or zoonotic |
| three ways that humans may acquire a zoonoses | 1. Direct contact w animal or waste (urine feces blood 2. Eating animals, raw or undercooked 3. Bloodsucking arthropods: can be vectors |
| Human carriers may be classified by what two ways | Asymptomatic and Symptomatic |
| Symptomatic | develop disease and have many symptoms characteristic to disease, eventually develop illnesses |
| Asymptomatic | subclinical, not showing any symptoms of the disease, not feeling any malaise, so not develop illness, can still be infective to others, may have defensive systems that protect them |
| Humans that carry infectious microbes that do not get sick or show any signs or symptoms of disease | asymptomatic carriers |
| Humans that carry infectious microbes that do get sick and show signs and symptoms of disease are called | symptomatic carriers |
| True or False: Only symptomatic carriers of infectious disease can spread the microbes to others. | False |
| What are the three examples of nonliving reservoirs | 1. water 2. food 3. soil/ waste or animal waste can contaminate |
| Presence of microorganisms often due to contamination of what? | feces and urine |
| Infectious microbes are transmitted from a reservoir to a new host’s portal of entry and may occur by what three broad ways? | 1. contact 2. vehicle 3. vector |
| three ways contact transmission can occur | 1. Direct contact transmission 2. Indirect contact 3. Droplet transmission |
| direct physical contact | Direct contact transmission, body contact btw hosts, and transmission within a single individual can occur |
| pathogens spread from host to host by fomites (doorknobs inanimate object) | Indirect contact |
| droplets of mucus by exhaling, coughing and sneezing, contact bc it is transmitted in close proximity | Droplet transmission |
| four ways vehicle transmission can occur | airborne, water borne, foodborne, and body fluid transmission |
| airborne transmission | aerosol particles in air that travel further than 1 meter, via an aerosol (sneezing, coughing, ac systems, sweeping, walking through carpet |
| Water borne transmission | arise from contaminated animal feces or animal urine contaminating water (fecal-oral infection), important for spread of many GI infections |
| Foodborne transmission | spread in and on foods, uncooked, undercooked, inadequately refrigerated foods, food many be contaminated with feces. |
| Body fluid transmission | blood urine saliva that carry pathogens, ex: STI’s. prevent contact w conjunctiva or breaks in skin or mucous membranes |
| two ways vector transmission can occur | Biological vectors and Mechanical vectors |
| Mechanical vectors | physical vectors they only carry but not internally, do not take in pathogen, passively transmits to new host Houseflies, cockroach, |
| Biological vectors | transmits pathogens and serve as host for some pathogens life cycle stage, stupid mosquitos, fleas, mites, ticks |
| The mere presence of microbes in or on the body is called | contamination |
| infection | When pathogenic microbes evade the body’s external defenses, multiply, and become established in the body they are said to cause |
| Sites through which pathogens enter the body | portal of entry |
| three major portals of entry | Skin, mucous membrane, and placenta |
| additional route of entry that is not one of the main three but still is a common route of entry | circumvent skin, and directly deposits microbes to underlying tissue, skin or mucous membranes |
| How can pathogens get through the skin barrier | Cuts or scrapes that allow opening, burrowing into or digest outer layers of skin such as keratin or collagen |
| four major mucous membranes in humans | 1. Respiratory tract 2. GI 3. EE 4. Urogenital tract, all provide warm, moist environments |
| Which mucous membranes are the most common route of entry and how do pathogens enter these membranes? | Respiratory tract and eyes |
| Pathogens that enter via the gastrointestinal route must be able to survive what | 2 to 3 pH of the stomach |
| placenta | Transfers O2 and nutrients from mother to embryo, typically a good barrier but some microbes that can cross the placenta |
| what effect can pathogens that can cross the placenta have on pregnancies | microbes that can cross the placenta (toxoplasma gondii, listeria) affect the fetus development and growth |
| Parental route | Pathogens that are deposited directly below the skin or mucous membranes via punctures can enter the body through an unofficial portal of entry |
| adhesion/attachment, which will typically lead to infection | The process by which pathogens attach themselves to host cells |
| True or false: Adhesion is typically required for colonization of pathogens in their host | False |
| Adhesion factors | Structures or molecules used by pathogens to attach themselves to host cells |
| type types of adhesion factors | 1. Specialized structures 2. Attachment molecules or ligands |
| What are examples of specialized adhesion factors | Fimbriae and capsules in bacteria, adhesion disks in protozoa that allow physical binding to host, hooks and suckers in helminths |
| Attachment molecules are also called | Ligands |
| Ligand | any molecule that can bind to a surface receptor molecule on host cells. Proteins that are lipoproteins or glycoproteins (carbo + protein). Microbe need complementary attachment point to human host cell to allow for physical attachment. |
| Ligand | Any protein that can bind to cell surface preceptor of humans |
| Adhesions or ligands | any ligands found on bacteria, fimbriae, flagella, and glycocalyces |
| adhesions | Proteins found on the surface of bacteria that allow them to attach to host cells |
| Proteins found on the surface of viruses that allow them to attach to host cells | attachment proteins |
| what do ligands need in order to infect | hosts that have complimentary surface proteins on their cell surfaces |
| True or false: Some pathogens can only infect one type of host | True |
| True or False: Some pathogens can only infect specific types of cells in specific hosts | True |
| Specificity | pathogens can only infect hosts that have complimentary surface proteins on their cell surfaces. |
| Are humans susceptible to all viruses? | No, Some are only animal viruses and do no harm to human, once they begin mutating can be some cross infection. |
| How can bacterial and viral attachment through specific ligand binding be prevented | Change or block ligand on its receptor: antimicrobial agent that binds to cell surface ligand, prevent protein expression of ligands |
| True or False: Pathogens that are unable to make attachment proteins or adhesins are avirulent. | False |
| mass of densely populated bacteria on a surface created by some bacterial pathogens attached to each other | biofilm |
| biofilm | Prevent antibiotics from diffusing into bacteria ex: catheters and plaque on teeth |
| two main ways that pathogens can evade host defenses, If they want to stay in body | Inactivate immune proteins and Antiphagocytic factors |
| Antiphagocytic factors | bacterial capsule and antiphagocytic chemicals evade phagocytic process |
| Inactivate immune proteins | antibodies specific for specific antigen, some microbes secrete enzymes that break down antibodies or (protease) and complement proteins |
| Bacterial capsule | A type of antiphagocytic factor that use capsule to help with attachements and are slippery making it difficult to be engulfed. contribute to biofilm formation and are composed of chemicals that are not recognized as foreign. |
| Antiphagocytic chemicals | a type of Antiphagocytic factor |
| How can some pathogens inactivate immune proteins | Some bacteria secrete protease enzymes that destroy antibodies and compliment proteins, which allows pathogen to survive host's immune system. |
| What are the two types of antiphagocytic factors | Bacteria capsule and antiphagocytic chemicals |
| How can bacterial capsules prevent bacteria from being phagocytized | help with attachment, are slippery and make it difficult to be engulfed, and contribute to biofilm formation that are composed of chemicals that may not be recognized as foreign |
| How can antiphagocytic chemicals prevent bacteria from being phagocytized or destroyed by phagocytic cells of the immune system | 1 bacterial capsules and 2 antiphagocytic chemicals |
| Pathogenecity | The ability of a microorganism to cause disease |
| A measure of the degree of pathogenicity | virulence |
| True or False: All pathogens have the same virulence level | False, pathogens have different types of virulence levels |
| the two main virulence factors | Extracellular enzymes and toxins, virulence factors contribute to virulence |
| two types of toxins that pathogens may produce | 1. Endotoxins and 2. Exotoxins |
| Exotoxins | Toxins that are secreted by some bacteria and can destroy cells or interfere with host cell |
| Endotoxins | found in LPS of gram neg bacteria, lipid A highly antigenic released only when the bacteria cell dies, not secreted part of membrane |
| the three main type of exotoxins | 1. Cytotoxins: 2. Neurotoxins: 3. Enterotoxins |
| Cytotoxins | Destroy host cells in general or affect their function |
| Neurotoxins | specificllay disrupt nerve cell function |
| Enterotoxins | affect cells lining the GI tract |
| disease | Results from direct disease-causing pathogen secreting virulence factors toxins or indirectly due to bodies immune system response overreacting to the pathogens secretion |
| synonymous term for disease | morbidity |
| 83. True or False: Disease can be caused either directly by cell and tissue damage from virulence factors of the pathogen or indirectly from the body’ own immune system overreacting contact with the pathogen or their secretions. | True |
| five stages of disease | Incubation period, prodromal period, illness, decline, and convalescence |
| incubation period | growth, no effect yet because not enough, can infect others with pathogen, can be short amount of time to decades such as leprosy |
| prodromal period | bacteria or any pathogen has increase in number that allows vague symptoms to present (malaise, fatigue, uneasy feeling, difficult to diagnose pathogen) |
| illness | pathogen highest concentration in body causing characteristic symptoms and signs , overwhelming immune system |
| decline | taking antimicrobial therapy, if not immune system ( many illnesses killed by IS), antimicrobial is starting to decline |
| convalescence | most symptoms are gone, any damage done body is starting to recover, issue is that pathogen is still able to be spread |
| three manifestations of disease | Symptoms, signs, and syndrome |
| Symptoms | felt by the patient only and are subjective, (pain, nausea, fatigue |
| signs | 2. Signs: objective manifestations that can be seen or measured by others (swelling, rash, erythema, emesis, can be visually detected |
| Syndrome: | most disease have their own characteristic symptoms and signs |
| Fatigue would be an example of | symptom |
| Swollen lymph nodes would be an example of | sign |
| Infections that lack symptoms but may still have signs of infection are called | asymptomatic or subclinical infections. |
| True or false: Portals of exit are usually the same as the portals of entry | True |
| How do pathogens commonly leave the body | Through secretions such as tears, nasal secretions. saliva, urine, feces, blood, etc. |
| five main ways that diseases can be classified | Taxonomic categories, body system they affect, longevity and severity, how they spread to their host, the effects they have on the population |
| Taxonomic | a type of classification for disease, based upon their taxonomy ex: gram +/- bacteria |
| What body system they affect | a type of disease classification, Upper respiratory, Gastrointestinal |
| How they affect the population | a type of disease classification, ex: pandemic, endemic, hospital acquired infection |
| Longevity and severity | a type of disease classification, chronic or acute |
| How they spread to their host | a type of disease classification, ex: contact, vehicle |
| Infections acquired by patients or healthcare workers while they are in healthcare facilities | healthcare associated infections (HAI’s) |
| What are they four types if HAI's | Exogenous, endogenous, iatrogenic, superinfection |
| Exogenous: | Pathogen acquired from the health care environment |
| Endogenous | arise from normal microbiota within the patient |
| iatrogenic | induced through modern medical procedures (catheterization, surgeries, invasive procedures) |
| Superinfection | antimicrobial drugs inhibits some resident microbiota allowing other microbes to thrive ex: c. diff having no competition so allows right environment to flourish |
| What is required for presence of HAI | presence of microbes, transmission of pathogens between people in the hospital, and immunocompromised patients |
| How are HAI's controlled | - Disinfection, aseptic techniques, hand washing, bathing, sanitary handling of food, hygiene, cleansing of surgical field, sterilization, use of PPE, isolation of highly contagious patients, |
| What is the most effective way of reducing/preventing HAI's | handwashing |
| Mutualism | Both organisms benefit (type of symbiosis) ex: bacteria in human colon |
| Commensalism | one organism benefits, the other neither benefits nor is harmed (type of symbiosis) ex: mites in human hair follicle s |
| Parasitism | one organism benefits, the other is harmed (type of symbiosis) ex: tuberculosis |
| Amensalism | one organism is harmed and the other is neither harmed or benefitted ex: fungus secreting an antibiotic inhibiting nearby bacteria |
| Why do some pathogens not cause illness at times but do at other times | because they are outcompeted for resources (like attachment point) but then may have opportunity to grow |
| types of endogenous (normal) microbiota | transient and resident |
| Examples of mucous membranes | Upper respiratory tract, Digestive tract, Urogenital tract, eyes, ear cannals |
| Humans are usually what for zoonotic pathogens? | Dead-end host |
| Outer layer of what portal of entry acts as a barrier to pathogens | outer layer of dead skin cells |
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Acrob89
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