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Fichas por Michelle Kimble, actualizado hace más de 1 año
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Creado por Michelle Kimble
hace más de 7 años
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| Pregunta | Respuesta |
| Discuss the development of normal flora in humans. | Normal flora in humans is a symbiotic relationship. Most resident microbes are established during the first few months of life. Rupture of the amniotic sac and passage through the birth canal and the first few breaths allowed microorganisms to enter through the mouth and nose and establish residence in the respiratory tract. The first meals allowed progenitors of microbiota to set up residence in the colon. Skin contact also allowed the transfer of microorganisms to the infant's skin. |
| The ubiquitous flora is not always protective to humans. Discuss a few ways in which the flora can become opportunistic pathogens. | Introduced to a new area of the body if the immune system is suppressed - stress, disease, malnutrition, age, chemotherapy, radiation, or immunosuppression drugs Changes in normal flora - this happens when there is a decline in lactobacillus that allows gardenrella to multiple - another example: when antibiotics affect the normal bacteria int he vagina allowing Candida albicans to grow |
| Describe three types of reservoirs using examples | 1. Animal reservoir - infectious diseases live in animals and can be transmitted to humans by direct contact with infected animals or their wastes, eating infected animals, or through blood sucking arthropods who fed off of infected animals that then bit a human. Once human is infected, the zoonose is a dead-end diseases. Ex: Malaria: transmitted from a mosquito that fed off of a monkey Ex: Lyme disease which is transmitted from a tick who has fed off of a deer 2. Human carrier - someone asymptomatic or healthy due to defensive system and unknowingly transmits pathogen to others. Ex: Mary Mallon - asymptomatic carrier of typhoid in the 1900s - chef who transmitted through food Ex: HIV virus - infected person doesn't know for first three months. Period of time allows a carrier to spread the disease unknowingly to others 3. Nonliving reservoir: soil, water and food that has been contaminated. Soil contaminated with feces can harbor Clostridium pathogens. Water contaminated with fecal mater and urine may contain parasitic worm eggs, protozoa, bacteria, and viruses |
| Compare and contrast the following terms: infection, disease, morbidity, pathogenicity and virulence. | Infection: when an organism enters the body , multiplies, and establishes itself in the body. An infection may or may not result in a disease. Disease: any internal condition in the body that is severe enough to interfere with normal function Morbidity: another term for disease which is any change from a normal state of functioning. Pathogenicity: a microbe's ability to cause disease Virulence: the degree of pathogenicity, the ability of a pathogen to infect a host and cause a disease If the pathogenicity of an organism is high, then there are virulence factors. Virulence factors means the pathogen in more virulent. The more virulent the pathogen, the higher the morbidity. |
| Infection | when an organism enters the body, multiples, and establishes itself in the body May or may not result in a disease |
| Disease | any internal condition in the body that is severe enough to interfere with normal function |
| Morbidity | another term for disease which is any change from a normal state of functioning |
| Pathogenicity | a microbe's ability to cause disease |
| Virulence | the degree of pathogenicity, the ability of a pathogen to infect a host and cause a disease |
| Virulence factors | Present when pathogenicity is high Means the pathogen is more virulent the more virulent the pathogen, the higher the morbidity |
| What is the difference between signs and symptoms? Provide three examples of each. | Signs: manifestations of a disease that can be observed or measured Ex: fever, blood pressure, pulse, liver enzymes Symptoms: manifestations of a disease that are subjective (can not be measured) Ex: fatigue, pain, or nausea |
| Compare and contrast exotoxins and endotoxins. Use examples. | Endotoxins come from a gram- bacterium. The lipid A lipopolysaccharide is anchored to the outer membrane. When the bacterium dies, the lipid A is released. In large enough numbers, the endotoxin effects are damaging. It can send a person into shock which can lower blood pressure. Ex: Haemophilus influenza, pseudomonas, and Vibrio cholerae. Exotoxins are from gram+ and gram- bacteria. They are secreted by microorganisms and either kill the host cell or interrupt the metabolism of the host cell. 3 types of exotoxins: cytotoxins, neurotoxins, and enterotoxins. Cytoxoxins kill the host or interrupt the metabolism. Neurotoxins interfere with nerve cell function. Enterotoxins affect the lining of the gastrointestinal tract. Ex: Clostridia, E. coli, Shigella |
| Describe the mechanism by which capsules enhance the survival of pathogens. | Capsules are made of many chemicals found in the human body such as polysaccharides. For this reason, capsules do not stimulate a response from the host. Additionally, many capsules are slippery which makes it hard for phagocytes to surround them. |
| Contact transmission | It is the spread of pathogens from one person to another by three methods: direct contact, indirect contact, and droplets. Direct contact requires body contact between one host and another. Ex: ringworm, sexually transmitted diseases, rabies Indirect contact is when fomites spread the disease from one host to another. Ex: HIB and hepatitis B Droplet transmission is when a pathogen is spread from one host to another through droplets of mucus. This can happen during coughing and sneezing. Ex: cold and flu viruses |
| Vehicle transmission | It is the transmission of pathogens through air, water, or food. Hantavirus and Streptococcus can be found on dust particles that float through the air. Amebic dysentery and cholera can be spread through water. Food that is incorrectly processed, undercooked, or improperly stored can contain botulism and E. coli. |
| Vector transmission | Vector transmission happens when a pathogen is spread in animals from one host to another. Biological vectors such as mosquitos and ticks can pass pathogens from an infected animal to a human. Examples: Malaria which is spread from an infected monkey which is fed on by a mosquito that later bit a human. Lyme disease which is spread from a deer which is fed on by a tick that later bit a human. Mechanical vectors are when pathogens are passively carried to new hosts via parts of the body such as the feet. Ex: Houseflies and cockroaches which may introduce pathogens such as Shigella and Salmonella into drinking water, food, or directly onto skin. |
| Contrast droplet transmission and airborne transmission. How do we prevent transmission of pathogens by these methods? | Droplet transmission: when a pathogen is carried on a mucous droplet through the air no more than one meter Airborne transmission: the spread of a pathogen greater than one meter. This can be caused by sneezing, coughing, air conditioners, sweeping, mopping, or even changing household linens. This can mostly be prevented by commonsense such as sneezing or coughing into your elbow instead of your hand, not making big sweeping motions when sweeping or mopping, and not flapping linens around when taking them off the bed. |
| Endemic | When the incidence and prevalence of a disease is stable |
| Epidemic | When the incidence of a disease is greatly increased, therefore, making the prevalence of a disease increase |
| Pandemic | When the disease has spread across continents |
| There are several types of nosocomial infections, ie endogenous, iatrogenic, superinfections. How are they different? Examples. | Endogenic is when the normal flora of a person is introduced to a new area of the body in a hospital setting and becomes opportunistic. Ex: when normal flora from a person's gut is introduced into the urinary system Iatrogenic is when a pathogen is introduced through a medical procedure such as the insertion of a catheter. Superinfections result from the use of antimicrobial drugs that inhibit normal flora to grow. This allows other flora to grow unchecked since there is no competition. Ex: antimicrobial therapy may allow C. difficile to grow unchecked and cause pseudomembranous colitis. |
| Symbiosis means | to live together |
| Types of symbiosis | Mutualism Commensalism Parasitism |
| Mutualism | Both benefit Ex: E. coli in gut/makes vitamins/host absorbs Ex: use of probiotics |
| Commensalism | One causes no harm, other may benefit Ex: S. epidermidis on skin/protects against pathogenic microbes |
| Parasitism | Anything that acts like a pathogen Ex: pathogens |
| Normal Microbiota in Hosts | Also termed normal flora and indigenous microbiota Can be affected by diet, medication, hormones Not identical between people |
| Two types of normal microbiota in hosts | Resident Transient |
| Resident microbiota definition | permanent part of you can't sterilize yourself |
| Transient microbiota definition | Things that you pick up hospital, daycare, school, work, environment |
| axenic | no natural microbiota Ex: alveoli |
| Upper Respiratory tract Resident Microbiota | Haemophilus, Lactobacillus, Moraxella, Staphylococcus, Fusobacterium |
| Upper digestive tract Resident microbiota | Actnomyces, Bacteroides, Haemophilus, Staphylococcus, Lactobacilllus, Neisseria |
| Lower digestive tract resident microbiota | Bacteroides, Clostridum, Enterococcus, Escherichia, Fusobacterium, Lactobacillus, Proteus, Shagilla |
| Female Urinary and Reproductive Systems Resident Microbiota | Bacteroides, Clostridium, Lactobacillus, Staphylococcus, Streptococcus, Candida |
| Male Urinary and Reproductive Systems Resident Microbiota | Bacteroides, Fusobacterium, Lactobacillus, Mycobacterium, Staphylococus, Streptococcus |
| Eyes and Skin Resident Microbiota | Corynebacterium, Micrococcus, Propionibacterium, Staphylococcus, Candida, Malassezia |
| Transient microbiota | Remains in the body for a short period Found in the same regions as resident microbiota Cannot persist in the body (competition from other microorganisms, elimination by the body's defense cells, chemical or physical changes in the body) |
| Acquisition of normal microbiota | develops first few months of life as they go through stages - how they mold and shape their flora all it takes is to be exposed to air development in womb free of microorganisms - axenic Microbiota begin to develop during the birthing process Much of one's resident microbiota established during first months of life |
| opportunistic pathogens | normal microbiota that cause disease under certain circumstances UTI, pneumonea |
| Conditions that provide opportunities for pathogens | Introduction of normal flora into a different site Immune suppression Changes in normal flora |
| Reservoirs (source) of infectious disease of humans | most pathogens cannot survive for long outside their host reservoirs (vectors) of infection: sites where pathogens are maintained as a source of infection |
| 3 types of reservoirs (vectors) | Animal reservoir Human reservoir Nonliving reservoir |
| Animal reservoirs | Zoonoses (dead-end diseases): diseases naturally spread from animal host to humans Aquired zoonoses through various routes: direct contact with animal or its waste, eating animals, bloodsucking arthropods Humans are usually dead-end host to zoonotic pathogens |
| Reservoirs of Zoonoses in Humans caused by Protozoa | Ex: Malaria (Plasmodium) - monkey/bite of anopheles mosquito Toxoplasmosis (Toxoplasma gondii) - cats/ingestion.inhalation of pathogen and contact |
| Reservoirs of Zoonoses in Humans causes by Fungi | Ex: Ringworm (Trichophyton) - Domestic animals/direct contact |
| Reservoirs of Zoonoses in Humans caused by Bacteria | Ex: Anthrax (Bacillus anthracis) - livestock Lyme Disease (Borrelia burgdorferi) - Deer/tick bite Salmonellosis (Salmonella) - Birds, rodents, reptiles, eating fecally contaminated foods |
| Reservoirs of Zoonoses in Humans caused by Viruses | Ex: Rabies (Lyssa virus) - Bats, foxes, skunks, dogs/bite Hantavirus pulmonary syndrome (Hanta virus) - Mice/inhalation of dried urine and feces Yellow Fever (Flavivirus) - Monkeys/bite of Aedus mosquito |
| Human Carriers Reservoirs of Infectious Disease of Humans | Asymptomatic Ex: HIV, STDs, Herpes, hepatitis B Infected individuals who are asymptomatic but infective to others Some individuals eventually develop illness while others never get sick Healthy carriers may have defensive systems that protect them They can transmit to someone else who might get sick |
| Nonliving Reservoirs Reservoirs of Infectious Disease of Humans | Soil, water, and food can be reservoirs of infection Soil (fungal, helminthic and bacterial pathogens) may contain fecal matter Water can be contaminated with fecal matter and urine (may harbor parasitic worm eggs, pathogenic protozoan, bacteria, and viruses) Food |
| What does helminthic mean? | worms |
| Exposure to Microbes: Contamination and Infection | Contamination: the mere presence of microbes in or on the body Infection: when organism evades body's external defenses, multiplies, and becomes established in the body Can be contaminated but not sick |
| Portals of Entry | Sites through which pathogens enter the body Four major pathways: Skin, Mucous membranes, Placenta Parenteral route (injected in - malaria, Lyme disease) |
| Portals of entry equal | portals of exit May leave same route or take new route |
| Mucous membranes Portals of Entry | Line the body cavities that are open to the environment Provide a moist, warm environment hospitable to pathogens Entry is through the nose, mouth, or eyes Gastrointestinal tract may be route of entry - must survive the acidic pH of the stomach |
| Placenta Portals of Entry | TORCH (Toxoplasmosis, Other - chicken pox, measles, Rubella, Cytomegalovirus, Herpes) Typically forms effective barrier to pathogens Pathogens may cross the placenta and infect the fetus Can cause spontaneous abortion, birth defects, premature birth |
| Parenteral Route Portal of Entry | Not a true portal of entry Pathogens deposited directly into tissues beneath the skin or mucous membranes |
| So how do organisms attach once they get in? | Adhesion |
| Adhesion | Process by which microorganisms attach themselves to cells Required to successfully establish colonies within the host Adhesion factors The specific interaction of adhesions/receptors determines the specificity of pathogens for particular hosts |
| Adhesion factors | Fimbriae, glycocalyx Able/more successful in causing infection (Specialized structures, attachment proteins) |
| Nature of infectious disease | Infection is the invasion of the host by a pathogen Disease results if the invading pathogen alters Disease is also referred to as morbidity |
| Mortality vs Morbidity | Mortality - death Morbidity - illness |
| Symptoms | Manifestations that are subjective Ex: pain, fatigue, chills, stomach ache, lethargy, headache, malaise, itching, abdominal cramps |
| Signs | Manifestations that are measured or observed Ex: fever, BP, O2 stat, pulse, blood sugar, liver enzymes, rash, pus formation, anemia |
| Syndrome | Symptoms and signs that characterize a disease or abnormal condition Ex: AIDS, Metabolic syndrome, Down syndrome |
| Asymptomatic | subclinical infections lack symptoms but may still have signs of infection |
| What is virulence? | How pathogenic an organism is degree of pathogenicity slightly pathogenic, highly pathogenic, etc. |
| Pathogenicity | ability of a microorganism to cause disease |
| Virulence factors contribute to | pathogenicity *Adhesion factors, biofilms, extracellular enzymes, toxins, antiphagocytic factors (glycocalyxes, capsule, etc.) The more virulence factors - the more virulent The more virulent - the more morbidity |
| More virulent to less virulent | Francisella tularensis (rabit fever) Yersinia pestis (plague) Bordetella pertussis (whooping cough) Pseudomonas aeruginosa (infection of burns - not an outright pathogen, opportunistic) Clostridium difficile (antibiotic-induced colitis) Candida albicans (vaginitis, thrush) Lactobacilli, diptheroids |
| Extracellular Enzymes | Invasive bacteria reach epithelial surface - bacteria produce hyaluronidase and collagenase - bacteria invade deeper tissues Bacteria produce coagulase (formation of clots from fibrinogen - takes fibrinogen and turns it into fibrin) - bacteria later produce kinsase (dissolving of a clot that allows microorganism to break free) |
| Coagulase positive microorganism | Staphylococcus aureus |
| Toxins | Chemicals that harm tissues or trigger host immune responses that cause damage Toxemia refers to toxins in the blood stream that are carried beyond the site of infection Exotoxins - released from inside of cell to outside of cell |
| Majority of gut flora is | gram negative |
| If there was a vaccine for gram- bacteria, we would.... | we would most likely be desensitized to it due to the majority of the flora in our gut is gram negative |
| Exotoxins | Source: both gram- and gram+ Chemical nature: protein or short peptide Relation to bacteria: metabolic product secreted from living cell Toxicity: High Heat Stability: Typically unstable at temperatures above 60 degrees Effect on host: Variable depending on source; may be cytotoxin, neurotoxin, enterotoxin Fever producing: no Antigenicity: Strong: stimulates antitoxin (antibody) production Toxoid formation for immunization?: By treatment with heat or formaldehyde Representative diseases: Botulism, tetanus, gas gangrene, diphtheria, cholera, plague, staphylococcal food poisoning Highly toxic (nano quantities) |
| Endotoxins | Source: gram- Chemical nature: lipid portion of lipopolysaccharide (lipid A) of outer (cell wall) membrane Heat stability: can autoclave for 1 hour till dead (121 degree Celsius) Relation to bacteria: Portion of outer (cell wall) membrane released upon cell death Toxicity: Low, but may be fatal in high doses Effect on host: Fever, lethargy, malaise, shock, blood coagulation Fever producing: yes Antigenicity: Weak Toxoid formation for immunization?: Not feasible Representative diseases: Typhoid fever, tularemia, endotoxic shock, urinary tract infections, meningococcal meningitis Low toxicity - takes a whole lot to kill |
| Antigenicity | ability of the host to see something as foreign |
| Antiphagocytic factors | Factors prevent phagocytosis Bacterial capsule: 1. composed of chemicals not recognized as foreign; 2. slippery Antiphagocytic chemicals: 1. Ability to prevent fusion of lysosome and phagosome - phagocyte engulfs organism - lysosome fuses with an organism and digests it (ex: Neisseria gonorrhea, Legionella pneumophilia); 2. Production of factors that directly destroy phagocytes (Leukocidins/ Staphylococcus aureus) 3. Production of factors that resist phagocytosis (M protein/fimbriae of Streptococcus pyogenes) Phagocytic cell can not wrap arms around M protein |
| The stages of infectious disease | The disease process occurs following infection Many infectious diseases have five stages following infection |
| 5 stages of infectious disease following infection | 1. Incubation period - (hours, days to 3 months) organism gets into body - no symptoms Ex: staphylococcus - potato salad - 4 hrs HIV - 3 months 2. Prodromal period - When you first notice you are getting sick 3. Illness - when you say yea, I knew I was getting sick - here it is. 4. Decline 5. Convalescence |
| Incubation Periods of Selected Infectious Diseases | Staphylococcus foodborne infection: 4-6 hours Influenza: About 1 day Cholera: 2 to 3 days Genital herpes: About 5 days Tetanus: 5 to 15 days Syphilis: 10 to 21 days Hepatitis B: 70 to 100 days AIDS: 1 to >8 years Leprosy: 10 to >20 years |
| Portals of Exit | Pathogens leave host through portals of exit Many portals of exit are the same as portals of entry Pathogens often leave hosts in material the body secretes or excretes |
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