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Medical Sciences > Lecture 4-Exam 2 > Flashcards

Lecture 4-Exam 2 Flashcards

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USMLE® Step 1 flashcards
1
Q

Mircoorganisms:
* What type of group?
* Found where?
* Relatively simple in what?
* Benefits and badness?

A
  • Most populous and diverse group of organisms
  • Found everywhere on the planet
  • Relatively simple in their construction and lack differentiated tissues
  • Benefits: production of food, beverages, antibiotics, and vitamins
  • Badness: causes disease in people, plants, or animals
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2
Q

What did these people do?
* Francesco stelluti
* Robert Hooke
* Antony Van Leeuwenhoek
* Louis Pasteur

A
  • Francesco Stelluti observed bees and weevils between 1625-1630
  • Robert Hooke – published drawings of the fungus Mucor in his book in 1965
  • Antony Van Leeuwenhoek- first person to observe microorganisms accurately in 1632-1723
  • Louis Pasteur- swan-neck flask experiments, discovered that boiling solutions caused no growth of microorganisms
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3
Q

The role of microorganisms in disease

  • What was infectious disease believed to be due to?
  • What was the treatment back in the day?
  • Why was studying microbes important?
A
  • Infectious disease was believed to be due to supernatural
    forces or imbalances of the 4 humors
  • Blood letting to cure fevers, releasing the bad humors
  • Studying microbes was important in understanding the connection between microbes and disease
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4
Q

Early evidence for the relationship between microorganisms and disease

What do louis pasteur demonstrate and develop?

A
  • Demonstrated microorganisms could carry out fermentation- helped the French wine industry
  • Developed pasteurization to avoid wine spoilage by microbes - later this was used for dairy and other assorted beverages
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5
Q

Early evidence for the relationship between microorganisms and disease

What do Joseph Lister provide and develop?

A
  • Provided indirect evidence that microorganisms were the causal agents of disease
  • Developed an antiseptic surgery system to prevent microorganisms from entering wounds
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6
Q

Early evidence for the relationship between microorganisms and disease

What did Robert Koch establish?

A
  • Established the relationship between bacillus anthracis and the disease anthrax
  • The criteria he used are now known as “Koch’s postulates”
  • Still used today to establish the link between a particular microorganism and a particular disease
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7
Q

Explain Koch’s postulates with TB (4)

A
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8
Q

Explain Koch’s postulates again :)

A
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9
Q

What were the limitations in Koch’s postulates? (3)

A
  • Some organisms cannot be grown in pure culture
  • Using humans in completing the postulates is unethical
  • Molecular and genetic evidence may replace and overcome these limits
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10
Q

Fill in for the divisions of microbes

A
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11
Q

Prokaryotes:
* Derived from what?
* One of the most ancients groups of what?
* Small or big?

A
  • Derived from Greek words which translates to before nuclei
  • One of the most ancient groups of living organisms on earth (fossil records dating back 3.5 billion years ago)
  • Comparatively smaller and simpler than eukaryotic cells
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12
Q

Prokaryotes:
* What does it not possess?
* Reproduction happens how?
* What does it have and what does this function as?
* What are examples?

A
  • Does not possess membrane bound cell organelles such as a nucleus
  • Reproduction happens through the process of binary fission
  • Have a capsule enveloping their entire body, functions as a protective coat (Helps to prevent phagocytosis)
  • Examples: bacteria and archaea
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13
Q

Eukaryotes:
* Derived from what?
* Small or big?
* What does it include?

A
  • Derived from the Greek words that translate into “good or true nuclei”
  • More complex and larger than prokaryotes
  • Include almost all of the major kingdoms
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14
Q

Eukaryotes:
* Posses what? What does this control?
* Nucleus contains what?
* What are examples?

A

Possess a cell wall which supports and protects the plasma membrane
* Controls the entry and exit of certain substances

Nucleus contains DNA, responsible for storing all genetic information
* Within nucleus is a nucleolus which is crucial to synthesizing proteins
* Also contains mitochondria

Examples: almost every unicellular organism with a nucleus

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15
Q

Bacteria are diverse but share common features, explain the three examples she gave

A

Shape
* Cocci and rods are most common
* Various others

Arrangement
* Determined by plane of division
* Determined by separation or not

Size

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16
Q

What are the different cocci shapes?

A
  • Diplococci – pairs
  • Streptococci- chains
  • Staphylococci – grape like clusters
  • Tetrads – 4 cocci in a square
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17
Q
A
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18
Q

Shape: rods and other shapes

  • Bacilli:
  • Coccobacilli:
  • Vibrios:
  • Spirilla:
  • Spirochetes:
  • Mycelium:
  • Pleomorphic:
A
  • Bacilli- rods
  • Coccobacilli – very short rods
  • Vibrios – resemble rods, comma shaped
  • Spirilla- rigid helices
  • Spirochetes – flexible helices
  • Mycelium – network of long, multinucleate filaments
  • Pleomorphic - organisms that are variable in shape
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19
Q

What are the commmon features of bacterial cell organization?

A

Cell envelope: 3 layers
1. Plasma membrane
2. Cellwall
3. Capsule, slime layer

Cytoplasm

External structures (depends on what bacteria)

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20
Q

What are the plasma membrane functions

A

Encompasses the cytoplasm, absolute requirement for all living organisms

Selectively permeable barrier

Interacts with external environment
* Receptors for detection of and response to chemicals in surroundings
* Transport systems
* Metabolic processes

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21
Q

How does the plasama membrane interact with external environment?

A
  • Receptors for detection of and response to chemicals in surroundings
  • Transport systems
  • Metabolic processe
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22
Q

Fill in gram + and -

A
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23
Q

Bacterial cell wall?

What are the cell wall functions?

A
  • Maintains shape of the bacterium
  • Helps protect cell from osmotic lysis and toxic materials
  • May contribute to pathogenicity (about cell wall that can invade our IS)
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24
Q

Peptidoglycan:
* What is it?
* What does a gram stain reveal about the peptidoglycan? Explain

A

Rigid structure lying just outside the cell plasma membrane

Gram stain reveals which two types of bacteria based on peptidoglycan
* Gram + stain purple due to thick peptidoglycans
* Gram - stain pink or red due to thin peptidoglycan and outer membrane

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25
Q

Explain the different structures on gram + and - cell wall (picture the cell wall in head)

A
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26
Q

Bacterial cell wall

What are the three layers in the cell wall?

A
  • Outer membrane
  • Peptidoglycan cell wall
  • Cytoplasmic or inner membrane
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27
Q

Gram + cell wall
* What does it lack? What is it surrounded by?
* What is threading through the layers of peptidoglycan?
* What do some gram + bacteria have?

A
  • Gram positive: lack an outer membrane, surrounded by layers of peptidoglycan many times thicker than is found in the gram negatives
  • Threading through the layers of peptidoglycan are long polymers called teichoic acids (unique)
  • Some gram positive bacteria have layer of proteins on surface of peptidoglycan
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28
Q

What is the periplasmic space in gram + cell wall?

A
  • Between plasma membrane and cell wall
  • Relatively few proteins (for transport)
  • Exoenzymes secreted by gram positive bacteria aids in degradation of large nutrients
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29
Q

Gram negative cell wall:
* What does it have surrounding it?
* Less or more complex?
* What does it consist of? What does that account for?
* Outer membrane composed of what? More or less permeable?
* What is not present?

A
  • Gram negative – peptidoglycan cell wall, surrounded by an outer membrane containing lipopolysaccharide
  • More complex than gram positive
  • Consist of a thin layer of peptidoglycan surrounded by an outer membrane -> Accounts for approximately 5-10% cell wall weight
  • Outer membrane composed of lipids, lipoproteins, and lipopolysaccharides -> More permeable than plasma membrane due to presence of porin proteins and transporter proteins
  • No teichoic acids
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30
Q

What makes the periplasmic space different in gram - than +

A
  • May constitute 20-40% of cell volume
  • Many enzymes present in periplasma (hydrolytic enzymes, transport proteins, and other proteins)
31
Q

What does the lipopolysaccharide consist of? (3)

A
  • Lipid A – buried in the outer membrane
  • Core polysaccharide – extend out from the cell š
  • O side chain – extend out from the cell

Gives cell polarity, permeabity and endotoxin

32
Q
A
33
Q

What was the one of the most crucial staining techniques in micro? Who first introduced it?

A
  • Gram staining was one of the most crucial staining techniques in microbiology
  • First introduced by Hans Christian Gram in 1882
34
Q

Gram staining involves the use of what?

A

š Involves the use crystal violet or methylene blue as the primary color

35
Q
  • Organisms that retain the primary color and appear purple brown under a microscope are what?
  • Organisms that do not take up primary stain appear red under a microscope are what?
A
  • Gram +
  • Gram -
36
Q
  • What can be used to perform gram staining?
  • Used when?
A
  • Can be performed using sputum, blood, cerebrospinal fluid, ascitic fluid, synovial fluid, pleural fluid, urine, etc.
  • Used for easy and early diagnosis of a bacterial infection
37
Q

What is the gram stain process (4)

Low yield

A
38
Q

What are hypotonic and hypertonic environments?

A

Hypotonic environments
* Solute concentration outside cell less than inside cell
* Water moves into cell and cell swells
* Cell wall protects from lysis

Hypertonic environments
* Solute concentration outside the cell is greater than inside
* Water leaves the cell
* Plasmolysis

39
Q
A
40
Q

A weakness in bacterial the cell wall

  • What is a lysozyme?
  • Where is it present?
  • What can it break?
A
  • Lysozyme- enzyme involved in the innate immune system:
  • In tears, saliva, and mucus
  • It can break the peptidoglycan structure
41
Q

What inhibits the peptidoglycan synthesis?

A

Penicillin

42
Q

External structures

  • What are external structures?
  • What is its function?
A
  • Extend beyond the cell envelope in bacteria
  • Function in protection, attachment to surfaces, horizontal gene transfer, cell movement
43
Q

What are pili, fimbriae and flagella?

A
  • Pili and fimbriae- short thin, hairlike, protein appendage, can mediate attachment to surfaces, motility, DNA uptake
  • Flagella – threadlike locomotor appendages extending outward from plasma membrane and cell wall – remain in the periplasmic space inside outer sheath
44
Q

What are the functions of the Flagella?

A
  • Motility and swarming behavior - flagellum rotates like a propeller
  • Attachment to surfaces
  • May be virulence factors
45
Q

Bacterial Endospore:
* What is it?
* Where is it located?
* What is it resistant to?

A
46
Q

Family Staphylococcaceae
* How many genera?
* What is the morphology? What does it grow in?
* Normally associated with what?

A
  • 4 genera including staphylococcus
  • Gram positive cocci-> Grow in clusters, pairs, and occasionally short chains
  • Normally associated with warm blooded animals in skin, skin glands, and mucous membranes
47
Q

Family Staphylococcaceae:
* At least how many species?
* Observation must be made on what?
* What is the family divided into?

A

At least 30 species of staphylococci have been recognized by biochemical analysis

Observation must be made on cultures grown in broth

Divided into two groups on the basis of their ability to clot blood plasma
* Coagulase positive staph constitutes the most pathogenic species- Staph aureus
* Coagulase negative staph are now known to compromise over 30 other species, ex. Staph epi

48
Q

Fill in the species

A
49
Q

Staph. aureus
* Important?
* Associated with what?
* Major cause of what?
* Colonizes where?

A

Most important human staphylococcal pathogen
* Associated with abscess, boils, wound infections, pneumonia,
osteomyelitis, endocarditis, toxic shock syndrome
* Major cause of common food poisoning
* Colonizes the nasal passage and axilla

50
Q

What are Staph. Aureus virulence factors (5)

A
  • Protein A binds host antibodies rendering them ineffective, inhibit phagocytosis
  • Surface proteins that promote colonization of host tissues
  • Toxins that damage host tissue and cause disease symptoms
  • Staphylokinase, plasminogen activator, dissolves clots that would keep the bacterium from invading beyond the initial site
  • Toxin beta-hemolysin lyses cells
51
Q

MRSA:
* What is it?
* Occured by what?
* Lowers what?
* Associated with what?

A

Methicillin resistant staph aureus
* Occurred by mutation of a penicillin-binding protein, a
chromosome-encoded protein
* Lowers the affinity of the organism to bind to beta-lactam antibiotics

Associated with significant morbidity, mortality, length of stay and cost burden

52
Q

Staph Epidermis:
* What is negative in and what is its morphology?
* Common where?
* Where does it readily colonize?
* What does it form?

A
53
Q

Infectious Endocarditis:
* Refers to what?
* What is it mainly caused by?

A
  • Refers to the colonization of cardiac valve endocardium by virulent microorganisms
  • Majority are caused from gram positive staph, strep, and enterococci infection – together accounts for 80-90% of all cases
54
Q

Treatment of choice for Staph infections:
* What does it depend on?
* What are the most common antibiotics commonly prescribed to treat? MRSA?

A

Depends on type and severity of the infection

Antibiotics commonly prescribed to treat staph infections include
* cefazolin, nafcillin, oxacillin
* vancomycin, daptomycin and linezolid.
* For serious staph infections, vancomycin may be required. This is because so many strains of staph bacteria have become resistant to other traditional antibiotics, also covers for MRSA

55
Q

Treatment of choice for Staph infections

  • When is resistance to methicillin present?
  • If methicillin is sensitive, treatment would be what?
  • If methicillin resistant, treatment would be what?
A
  • Resistance to methicillin is present in more than 80% of the coagulase negative staph isolates
  • If methicillin sensitive, treatment would be beta lactam antibiotics such as nafcillin and oxacillin
  • If methicillin resistant, treatment would be IV vancomycin
56
Q

Streptococci:
* What is the morphology?
* Most steptococci are what?
* Classified on the basis of what?
* All streptococci lack what?

A
  • Gram positive, non–motile, non spore forming, catalase negative cocci that occur in chains
  • Most streptococci are anaerobes
  • Classified on the basis of colony morphology, hemolysis, and serologic specificity
  • All streptococci lack the enzyme catalase (different than staphylococcus)
57
Q

What are the significant human diseases caused by streptococci?

A

scarlet fever, rheumatic heart disease, glomerulonephritis, and pneumonia

58
Q

Streptococci:
* Classified on the basis of what?
* Divided into three groups by what?

A

Classified on the basis of colony morphology, hemolysis, and serologic specificity

Divided into three groups by the type of hemolysis on blood agar
* Beta hemolytic, alpha hemolytic, and gamma hemolytic

59
Q

Streptococci:
* Serologic grouping is based on what?
* Serologic groups as what?
* VFs are different for what?
* Group B strep is common where?
* Human disease is most commonly associated with what?

VF: virulence factors

A
60
Q
  • Group B strep is found where?
  • Human disease is commonly associated with what? Most often what?
A

Group B strep common in normal vaginal flora- maternal IgG protects the neonate group against it

Human disease is most commonly associated with group A streptococci
* Most often a respiratory infection (pharyngitis, tonsillitis)

61
Q

What is pyogenic (pus producing) streptococci?

A

Strep pyogenes (group A)- leading cause of uncomplicated bacterial pharyngitis and tonsillitis = can also cause acute glomerulonephritis, and rheumatic fever

62
Q

What is oral streptococci?

A

S. mutans - dental caries

63
Q
  • What is S. Pneumoniae? Where?
  • Numbers are normally limited by what?
  • Usually happens with what?
A

S. pneumoniae – normal member of the nasopharyngeal/respiratory microbial ecosystem
* Numbers are normally limited by competition from the ecosystem, but failure of these mechanisms can result in disease
* Usually happens with acquisition of a new strain following alteration of the normal flora. Invasion results in pneumonia. Can also cause: meningitis, bacteremia, and otitis media

64
Q

What is strep viridans?

A

šNon groupable streptococci of the oral, gastrointestinal tract, and urogenital tract

65
Q

Strep viridans:
* Important what?
* S. mutans and S. sanguis are what?
* What is predisposed?

A
  • Important etiologic agents of bacterial endocarditis
  • S. mutans and S. sanguis are odontopathogens responsible for dental caries
  • Valves from rheumatic heart fever or congenital abnormalities predispose
66
Q

Enteroccocus:
* What is the morphology?
* Found where?
* How many species? What are the most important ones?

A
  • Gram positive,** anaerobic cocci in short and medium chains**
  • Found in the soil, water, food, sewage, human skin, oral cavity, and large intestine
  • 58 recognized species of enterococcus-> Most important and common is E. faecalis and E. faecium
67
Q

Enteroccocus:
* Main predisposing factor is what?
* Common cause of what?
* 60% of all infections by enterococci are what?
* Intrinsic resistance to some antibiotics, which ones?

A
  • Main predisposing factor for severe infections- enterococcal colonization of the GI tract
  • Common cause of UTI, bacteremia, infective endocarditis, peritonitis
  • 60% of all infections by enterococci are healthcare acquired, including ICU setting
  • Intrinsic resistance to some antibiotics – cephalosporins, clindamycin, aminoglycosides
68
Q

Enterococci virulence:
* What do they not produce? Where does their virulence comes from?
* What can they form?
* They can secrete what?

A
  • Enterococci do not produce toxins like staph or strep, but virulence comes from other properties like durability, structure, and antibiotic resistance
  • Ability to form a biofilm – promotes adherence to catheters, prostheses, heart valves and limits antibiotic penetration
  • They secrete virulence factors that lead to cell injury
69
Q

Enterococcus faecalis:
* Inhabits what?
* What are some traits ?
* Can survive in what?
* Can cause what?

A
  • Inhabits the gastrointestinal tract of humans, found in healthy humans
  • Anaerobic, non motile
  • Can survive very harsh environments including extremely
    alkaline pH 9.6
    Can cause endocarditis, sepsis, urinary tract infections, meningitis
70
Q

Enterococcus faecium:
* Commensal organism in waht?
* Leading cause of what?

A
  • Commensal organism in the gastrointestinal tract of humans
  • Leading cause of multi drug resistant enterococcal infections (VRE)
71
Q

Neisseria:
* Morphology?
* Approx how many species?
* Most of these organism do what?
* What are the two species have evolved to cause disease in humans?

A
72
Q

What organism is this?

A

N. Gonorrhoeae

73
Q

N. Gonorrhoeae:
* Obligate pathogen that primarily colonizies what?
* Symptoms? (men v women)

A

Obligate pathogen that primarily colonizes the mucosal epithelium of the male urethra and female cervix, causing the sexually transmitted disease gonorrhea.
* Symptoms: neutrophil influx at sites of mucosal colonization
* Men get urethritis, painful discharge
* Women get mucopurulent cervicitis (this is usually asymptomatic)

Medical Sciences (11 decks)

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