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Chapter 14 - Exam 4
General microbiology - BIO 175
| Question | Answer |
|---|---|
| Symbiosis | To live together |
| Type of symbiosis | 1) Mutualism 2) Commensalism 3) Amensalism 4) Parasitism |
| Microbiome of humans | - Organisms that colonize the body's surfaces without normally causing disease - Normal microbiota, normal flora, and indigenous microbiota |
| Types of microbiome | 1) Resident microbiota 2) Transient microbiota |
| Resident microbiota | - Part of the normal microbiota throughout life - Mostly commensal |
| Transient microbiota | - Remain in the body for short period (temporary) - Found in the same regions as resident microbiota |
| Why transient microbiota cannot persist in the body? | - Microbial antagonism - Elimination by the body's defense cells (immune system) - Chemical or physical changes in the body |
| Microbial antagonism | Competition from other microorganisms |
| Axenic | Development in womb free of microorganism |
| Opportunistic pathogens | Normal microbiota that cause disease under certain circumstances |
| Circumstances that provide opportunities for pathogens (opportunistic pathogens) | - Introduction of normal microbiota into unusual site in the body - Immune suppression - Changes in the normal microbiota - Stressful conditions |
| Reservoirs | Sites where pathogens are maintained as a source of infection |
| Types of reservoirs | 1) Animal reservoirs 2) Humans carriers 3) Nonliving reservoirs |
| Infections | Exposure to microbes |
| Contamination | The mere presence of microbes in or on the body |
| Infections | When organism evades body's external defenses, multiplies, and becomes stablished in the body (increasing in number) |
| Portals of entry | - Sites through which pathogens enter the body - Three major pathways 1) Skin 2) Mucous membranes 3) Placenta - Entry via the parental route circumvents the usual portals |
| Skin (portals of entry) | - Outer layer of dead skin cells acts as barrier to pathogens - Some pathogens can enter through opening or cuts - Others enter by burrowing into or digesting outer layer of skin |
| Mucous membrane (portals of entry) | - Line the body cavities that are open to the environment - Provide a moist, warm environment hospitable to pathogens - Respiratory tract is the most common site of entry (nose. mouth, eyes) - Gastrointestinal tract may be route of entry (if surv pH) |
| Placenta (portals of entry) | - Typically forms effective barrier to pathogens - Pathogens may cross the placenta and infect de fetus (can cause spontaneous abortion, birth defects, premature birth) |
| Parenteral rout (portals of entry) | - Not a true portal of entry - Means by which other portals of entry can be circumvented - Pathogens deposited directly into tissues beneath the skin or mucous membranes |
| Adhesion (role in infection) | - Process by which microorganisms attach themselves to cells - Required to stablish colonies successfully within the host |
| Uses adhesion factors | 1) Specialized structures 2) Attachment proteins |
| Attachment proteins | - Found on viruses and many bacteria - Viral or bacterial ligands bind host cell receptors (Interaction can determine host cell specificity) |
| Avirulent | Inability to make attachment proteins or adhesins renders microorganisms |
| Infection | Invasion of the host by a pathogen |
| Disease | Results if the invading pathogen alters normal body functions |
| Morbidity | Disease |
| Manifestations of disease | 1) Symptoms 2) Signs 3) Syndromes |
| Symptoms | Subjective characteristics of disease felt only by the patient |
| Signs | Objective manifestations of disease observed or measured by others |
| Syndrome | Symptoms and signs that characterize a disease or abnormal condition |
| Asymptomatic or Subclinical | Infections lack symptoms but may still have signs of infections |
| Etiology | - Study of the cause if disease - Diseases have various causes |
| Etiology use Koch’s postulates | - Germ theory of disease - Infections by pathogenic microorganisms cause disease - Set of postulates to one must satisfy to prove a particular pathogen cause a particular disease |
| Pathogenicity | Ability of microorganisms to cause disease |
| Virulence | Degree of pathogenicity |
| Virulence factor | - Adhesion - Biofilms - Extracellular enzymes - Toxins -Antiphagocytic factors |
| Extracellular enzymes | |
| Toxins | Chemical that harm tissue or trigger host immune responses that cause damage |
| Toxemia | Refers to the presence of toxins in the bloodstream (carried beyond the site of infection) |
| Two types of toxins | 1) Exotoxins (outside) 2) Endotoxins |
| Antiphagocytic factors | - Factors prevent phagocytosis by the host’s phagocytic cells - Allow pathogens to remain in host for longer time |
| Bacterial capsule (Antiphagocytic factor) | - Composed of chemicals not recognized as foreign - Slippery and difficult for phagocytes to engulf |
| Antiphagocytic chemicals (Antiphagocytic factor) | - Prevent fusion of lysosome and phagocytic vesicles - Leukocidins directly destroy phagocytic white blood cells |
| Stages of infectious diseases | 1) Incubation period 2) Prodromal period 3) Illness 4) Decline 5) Convalescence |
| 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 materials the body secretes or excretes |
| Transmission | From a reservoir or a portal of exit to another host's portal of entry |
| Groups of transmission | 1) Contact transmission: Direct, indirect, or droplet 2) Vehicle transmission: Airborne, waterborne, or foodborne 3) Vector transmission: Biological or mechanical |
| Contact transmission direct | - Usually involves body contact between hosts - Transmission within a single individual can also occur |
| Contact transmission indirect | Pathogens spread from host to host by fomites |
| Contact transmission droplet | Spread of pathogens in droplets of mucus by exhaling, coughing, and sneezing |
| Fomites | |
| Airborne (vehicle transmission) | - When pathogens travel more than 1 meter via an aerosol - Sneezing, coughing, air-conditioning systems, sweeping |
| Waterborne (vehicle transmission) | - Important in the spread of many gastrointestinal diseases - Fecal-oral infection |
| Foodborne (vehicle transmission) | - Spread of pathogens in and on foods - Inadequately processed, cooked, or refrigerated foods - Foods may become contaminated with feces |
| Bodily fluid transmission (vehicle) | - Bodily fluid such as blood, urine, or saliva can carry pathogens - Prevent contact with conjunctiva or breaks in the skin or mucous membranes |
| Biological vectors | - Transmit pathogens and serve as host for some stage - Biting arthropods transmit many diseases to humans |
| Mechanical vectors | Passively transmit pathogens present on their body to new hosts |
| Classification of diseases | - Taxonomic categories - The body system they affect - Their longevity and severity - How they are spread to their host - The effects they have on populations |
| Frequency of disease | - Track occurrence of diseases using two measures - Incidence and prevalence |
| Incidence | Number of new cases of disease in a given area during a given period of time |
| Prevalence | Number of total cases of a disease in a given area during a given period of time |
| Epidemiology studies... | 1) Descriptive epidemiology 2) Analytical epidemiology 3) Experimental epidemiology |
| Descriptive epidemiology | - Careful tabulation of data concerning a disease * Record location of data concerning a disease * Collect patient information - Try to identify the index case of the disease |
| Analytical epidemiology | - Seeks to determine to probable cause, mode of transmission, and methods of prevention - Useful in situations when Koch’s postulates can’t be applied - Often retrospective (investigation occurs after an outbreak has occurred) |
| Nosocomial infections | Types of health care-associated infections 1) Exogenous 2) Endogenous 3) Iatrogenic 4) Superinfections |
| Exogenous | Pathogen acquires from the health care environment |
| Endogenous | Pathogen arises from normal microbiota within patient |
| Iatrogenic | Results from modern medical procedure |
| Superinfections | Use of antimicrobial drugs reduces inhibits some resident microbiota, allowing other microbiota to thrive |
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