MIC 205A EXAM 4 QUESTIONS WITH
CORRECT ANSWERS
Dancing with Microbes - ANSWER -Microbes are ubiquitous
-Microbes are breathed in, ingested, and picked up on skin
-Most do not harm us, many are beneficial
-Some colonize on skin and mucous membrane, most ingested microbes die in stomach
or excreted
-Some shed with dead epithelial cells
-Relatively few microbes evade defense and cause diseases -> distinct characteristics
allow avoidance of some body defenses
Normal microbiota - ANSWER -Not harmful
-Organisms that routinely reside on body's surfaces
-Relationship is delicate balance; some can cause disease if there is an opportunity
(weakness or defects n innate or adaptive defenses can leave individuals vulnerable to
invasion -> malnutrition, cancer, AIDS or other disease, surgery, wounds, genetic
defects, alcohol or drug abuse, and immunosuppressive therapy)
-Permanently colonize the host
Symbiosis - ANSWER -Different organisms living together
-Mutualism - ANSWER -Kind of symbiosis
-Both partners benefit
-Example: in large intestine, some bacteria synthesize vitamin K and B vitamins, which
host can absorb; bacteria are supplied with warmth, energy sources
Commensalism - ANSWER -Kind of symbiosis
-One partner benefits without harming the other partner
-Many microbes living on skin neither harmful nor helpful, but obtain food and
necessities from host
Parasitism - ANSWER -Type of symbiosis
-One organism benefits at expense of other
,-All pathogens are parasites, but medical microbiologists often reserve for eukaryotic
pathogens (for example, protozoa, helminths)
Opportunistic pathogens - ANSWER -Take advantage of weakened immune system
Microbiota/Microbiome - ANSWER -A collection of microbes in a given ecological niche
-Important to human health
-Relatively little is known
-Human Microbiome Project studying microbiota using metagenomics, analysis of DNA
without culturing
Transient microbiota - ANSWER -May be present for days, weeks, or months
-Inhabit temporarily
Composition of the Normal Microbiota - ANSWER -37 trillion human cells
-100 trillion bacteria, 70-80% non-culturable
-Estimated bacterial species: 5,000-35,000 in intestine, 300-500 in mouth, 120 species
on skin
-160-fold more gene in gut microbiome than in human genome
-We get our microbiomes at birth, during breast feeding, and from food and the
environment
-Obese people have more Firmicutes while lean people have more Bacteroides
-Weight loss changes microbiota to resemble that of lean people
-Composition different among individuals and over time
-Changes with physiological state and life style of host
Normal Microbiota and Your Health - ANSWER -Microbial antagonism or competitive
exclusion: occupying sites of attachment; nutrient competition; antibiotic compounds
(bacteriocins); alter environment (lower pH)
-Training adaptive immune system (hygiene hypothesis): activate B and T cells; develop
tolerance to routine microbes in guts, food, and on other mucosal membranes ->
insufficient exposure to microbes leads to allergies; antibodies against normal
microbiota also bind to pathogens; mice in microbe-free environment have
underdeveloped MALT
-Aiding digestions (break down of fibers)
-Producing required compounds (Vitamins K and B, fatty acids)
,-Upsetting microbiota balance can lead to infection (Vulvovaginal candidiasis when
Lactobacillus inhibited by antibiotics; Clostridium difficile and diarrhea when oral
antibiotics inhibit intestinal microbiota and allow overgrowth of C. difficile)
Colonization - ANSWER -Establishment and multiplication of microbes at a given niche
Infection - ANSWER -Colonization of an organism by pathogens, not always lead to
diseases
-Can be used to refer to pathogen
-Can be subclinical: no or mild symptoms
Disease - ANSWER -An abnormal state in the physiology of an organism
Signs - ANSWER -Objective, measureable evidence
-Rash, pus formation, swelling, temperature
Symptoms - ANSWER -Subjective effects experienced by patient
-Pain, nausea
Infectious disease - ANSWER -Infectious disease yields noticeable impairment
-Caused by microbial infection
-Primary infection: initial infection
-Damage can predispose individual to developing a secondary infection (respiratory
illness impairing mucociliary escalator)
Pathogenicity - ANSWER -The ability to cause disease
Virulence - ANSWER -The degree of pathogenicity
Virulence factors - ANSWER -Microbial traits contributing to disease development
Pathogenic Microbes = Diseases? - ANSWER -Percentage of humans colonized by
common pathogens: 33% Mycobacterium tuberculosis, 50% H. pylori, 50% S. aureus
-Symptomless Carriers: apparently healthy individuals capable of spreading infectious
agents for long periods of time
Disease Development: Disease Triangle - ANSWER -Hosts
-Environment
-Pathogens
-Disease in middle
, Characteristics of Infectious Diseases - ANSWER -Communicable/Contagious diseases:
easily spread
-Infectious doses: Number of initial microbes often determines the outcome of an
infection; number of microbes necessary to establish infection
-ID50 is number of cells that infects 50% of population
-Shigellosis results from 10-100 ingested Shigella
-Salmonellosis results from as many as 10^6 ingested Salmonella enterica serotype
Enteritidis
-Difference partially reflects ability to survive stomach acid
-LD50
-Skin needs less endospores of B. anthracis -> inhalation -> ingestion
Incubation period - ANSWER -Time between infection and onset
-Varies considerably: few days for common cold to even years for leprosy
-Depends on growth rate, host's condition, infectious dose
Illness - ANSWER -Signs and symptoms of disease
-May be preceded by prodromal phase (vague symptoms; a phase of early, mile, and
vague symptoms after incubation period)
Convalescense - ANSWER -Recuperation, recovery from disease
Acute infections - ANSWER -Symptoms develop quickly, last a short time (strep throat)
-Incubation period -> illness -> convalescence
-Illness is short term because the pathogen is eliminated by the host defenses; person is
usually immune to reinfection
Chronic infections - ANSWER -Develop slowly, last for months or years (tuberculosis)
-Incubation period -> illness (long lasting)
CORRECT ANSWERS
Dancing with Microbes - ANSWER -Microbes are ubiquitous
-Microbes are breathed in, ingested, and picked up on skin
-Most do not harm us, many are beneficial
-Some colonize on skin and mucous membrane, most ingested microbes die in stomach
or excreted
-Some shed with dead epithelial cells
-Relatively few microbes evade defense and cause diseases -> distinct characteristics
allow avoidance of some body defenses
Normal microbiota - ANSWER -Not harmful
-Organisms that routinely reside on body's surfaces
-Relationship is delicate balance; some can cause disease if there is an opportunity
(weakness or defects n innate or adaptive defenses can leave individuals vulnerable to
invasion -> malnutrition, cancer, AIDS or other disease, surgery, wounds, genetic
defects, alcohol or drug abuse, and immunosuppressive therapy)
-Permanently colonize the host
Symbiosis - ANSWER -Different organisms living together
-Mutualism - ANSWER -Kind of symbiosis
-Both partners benefit
-Example: in large intestine, some bacteria synthesize vitamin K and B vitamins, which
host can absorb; bacteria are supplied with warmth, energy sources
Commensalism - ANSWER -Kind of symbiosis
-One partner benefits without harming the other partner
-Many microbes living on skin neither harmful nor helpful, but obtain food and
necessities from host
Parasitism - ANSWER -Type of symbiosis
-One organism benefits at expense of other
,-All pathogens are parasites, but medical microbiologists often reserve for eukaryotic
pathogens (for example, protozoa, helminths)
Opportunistic pathogens - ANSWER -Take advantage of weakened immune system
Microbiota/Microbiome - ANSWER -A collection of microbes in a given ecological niche
-Important to human health
-Relatively little is known
-Human Microbiome Project studying microbiota using metagenomics, analysis of DNA
without culturing
Transient microbiota - ANSWER -May be present for days, weeks, or months
-Inhabit temporarily
Composition of the Normal Microbiota - ANSWER -37 trillion human cells
-100 trillion bacteria, 70-80% non-culturable
-Estimated bacterial species: 5,000-35,000 in intestine, 300-500 in mouth, 120 species
on skin
-160-fold more gene in gut microbiome than in human genome
-We get our microbiomes at birth, during breast feeding, and from food and the
environment
-Obese people have more Firmicutes while lean people have more Bacteroides
-Weight loss changes microbiota to resemble that of lean people
-Composition different among individuals and over time
-Changes with physiological state and life style of host
Normal Microbiota and Your Health - ANSWER -Microbial antagonism or competitive
exclusion: occupying sites of attachment; nutrient competition; antibiotic compounds
(bacteriocins); alter environment (lower pH)
-Training adaptive immune system (hygiene hypothesis): activate B and T cells; develop
tolerance to routine microbes in guts, food, and on other mucosal membranes ->
insufficient exposure to microbes leads to allergies; antibodies against normal
microbiota also bind to pathogens; mice in microbe-free environment have
underdeveloped MALT
-Aiding digestions (break down of fibers)
-Producing required compounds (Vitamins K and B, fatty acids)
,-Upsetting microbiota balance can lead to infection (Vulvovaginal candidiasis when
Lactobacillus inhibited by antibiotics; Clostridium difficile and diarrhea when oral
antibiotics inhibit intestinal microbiota and allow overgrowth of C. difficile)
Colonization - ANSWER -Establishment and multiplication of microbes at a given niche
Infection - ANSWER -Colonization of an organism by pathogens, not always lead to
diseases
-Can be used to refer to pathogen
-Can be subclinical: no or mild symptoms
Disease - ANSWER -An abnormal state in the physiology of an organism
Signs - ANSWER -Objective, measureable evidence
-Rash, pus formation, swelling, temperature
Symptoms - ANSWER -Subjective effects experienced by patient
-Pain, nausea
Infectious disease - ANSWER -Infectious disease yields noticeable impairment
-Caused by microbial infection
-Primary infection: initial infection
-Damage can predispose individual to developing a secondary infection (respiratory
illness impairing mucociliary escalator)
Pathogenicity - ANSWER -The ability to cause disease
Virulence - ANSWER -The degree of pathogenicity
Virulence factors - ANSWER -Microbial traits contributing to disease development
Pathogenic Microbes = Diseases? - ANSWER -Percentage of humans colonized by
common pathogens: 33% Mycobacterium tuberculosis, 50% H. pylori, 50% S. aureus
-Symptomless Carriers: apparently healthy individuals capable of spreading infectious
agents for long periods of time
Disease Development: Disease Triangle - ANSWER -Hosts
-Environment
-Pathogens
-Disease in middle
, Characteristics of Infectious Diseases - ANSWER -Communicable/Contagious diseases:
easily spread
-Infectious doses: Number of initial microbes often determines the outcome of an
infection; number of microbes necessary to establish infection
-ID50 is number of cells that infects 50% of population
-Shigellosis results from 10-100 ingested Shigella
-Salmonellosis results from as many as 10^6 ingested Salmonella enterica serotype
Enteritidis
-Difference partially reflects ability to survive stomach acid
-LD50
-Skin needs less endospores of B. anthracis -> inhalation -> ingestion
Incubation period - ANSWER -Time between infection and onset
-Varies considerably: few days for common cold to even years for leprosy
-Depends on growth rate, host's condition, infectious dose
Illness - ANSWER -Signs and symptoms of disease
-May be preceded by prodromal phase (vague symptoms; a phase of early, mile, and
vague symptoms after incubation period)
Convalescense - ANSWER -Recuperation, recovery from disease
Acute infections - ANSWER -Symptoms develop quickly, last a short time (strep throat)
-Incubation period -> illness -> convalescence
-Illness is short term because the pathogen is eliminated by the host defenses; person is
usually immune to reinfection
Chronic infections - ANSWER -Develop slowly, last for months or years (tuberculosis)
-Incubation period -> illness (long lasting)
