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Pharm I: Exam 3 > Introduction to Medical Microbiology > Flashcards

Introduction to Medical Microbiology Flashcards

1
Q

What is Medical Microbiology?

A

“the study of microorganisms (including bacteria, viruses, fungi, and parasites) which are of medical importance and are capable of causing diseases in human beings”

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2
Q

Why is Medical Microbiology important?

A

Infection is one of the most important causes of morbidity and mortality in the population.

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3
Q

What is the normal flora?

A

The population of bacteria, fungi, and parasites that live on the human body.

  • Systems include Skin, Nose, Mouth, GI Tract
  • Humans are NOT microbiologically sterile!
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4
Q

What functions does the normal flora perform for the host? (3)

A
  • Competition with pathogenic microorganisms
  • Aids in digestion
  • produces essential vitamins (e.g. folic acid, Vitamin K)
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5
Q

What could happen if diseases are at the wrong site?

A

Disease (e.g. E.coli in the bladder → UTI)

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6
Q

What is contamination?

A

Presence of an organism in a culture that was not there when the sample was taken (e.g. blood culture with an organism from the skin ⇒ contaminated)

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7
Q

What are two definitions for colonization?

A
  1. First stage of microbial infection – successful occupation of new habitat not normally found in niche
  2. Presence of bacteria on a body surface (i.e. skin, mouth, intestines) without causing disease in person
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8
Q

What is an infection?

A

“Colonization and/or invasion and multiplication of pathogenic microorganisms in the host with or without the manifestation of disease”

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9
Q

How are ALL living organisms classified? (4)

A
  1. Kingdom
  2. Phylum (family)
  3. Genus
  4. Species
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10
Q

What is the Relevance of classifications?

A
  • Diseases (bacteria, fungi, and virus most likely cause ACUTE infections)
  • Mode of Transmission
  • Treatments (antibiotics do not cure viral infections)
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11
Q

What are the characteristics of a virus?

A
  • 50-300nm (small)
  • Unable to replicate independently (Invade host cells and use replication machinery in cell)
  • Often difficult to treat
    *
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12
Q

What are the characteristics of a bacteria?

A
  • 500-800nm
  • Capable of independent replication
  • Cause most diseases in hospitals
  • Many different species (e.g. Pneumonia, bacterial, meningitis, cellulitis)
  • Treat with antibiotics
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13
Q

What are characteristics of a fungus?

A
  • Complex, large eukaryotes (AS ARE HUMANS)
  • Separated into Yeast and Molds
  • Cause a range of diseases (many are opportunistic)
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14
Q

What are characteristics of a parasite?

A
  • Lives in/on a host
  • Retrieves food from or at the expense of the host
  • can cause disease in humans (some easily treated)
  • Usually exist in the tropics or subtropics (some developing countries)
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15
Q

Why are bacterias classified?

A

Different bacteria:

  • cause different disease
  • susceptible/resistant to different antibiotics
  • some related to common flora ()others related to pathogens)
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16
Q

How are bacteria classified?

A

Bacterium shape and cell arrangement (most basic method)

17
Q

What are three (3) morphological categories of bacteria?

A
  • Bacilli (rod)
  • Cocci (round)
  • Spirilla (spiral)
18
Q

What are some common cellular arrangements of bacteria?

A
  • Singly
  • Chains
  • Clusters

Some have flagella (enable motile capabilities)

19
Q

Flow chart for Antibiotic testing

A
20
Q

What is a Gram Stain?

A

Method of differentiating bacteria (gives initial possible identity of organism)

  • May be Positive (+) or Negative (-) dependent on bacteria
  • Further classified based on shape (e.g. rod, coccus)
  • 4 Combinations: G(+) rod, G(+) coccus, G(-) rod, G(-) coccus

First available result on blood cultures (rapid, can be completed without growing organism)

21
Q

What are bacteria wall differences of Gram Positive and Gram Negative?

A

Gram Positive: thick peptidoglycan layer (“teichoic acid”)

  • Retains crystal violet stain (appears deep violet-blue)
  • Resist discoloration

Gram Negative: thick lipopolysaccharide layer (little/no teichoic acid)

22
Q

What is the relevance to Gram reactions?

A
  • Different gram reactions are susceptible to different groups of antibiotics
  • Cause different diseases
  • Differing characteristics (survival, cleaning, infection control, outbreak management)
23
Q

What is facultative anaerobic respiration?

A

Microorganism that can perform in either under aerobic or anaerobic respiration depending on environment (prefers aerobic due to higher efficiency, however, no oxygen is a simple switch to anaerobic)

24
Q

What is the classification (i.e. gram stain) of Streptococcus species?

A

Gram Positive bacteria

25
Q

What is the classification (i.e. gram stain) of a Clostridium species?

A

Anaerobic Gram Positive Rods

26
Q

What is the classification (i.e. gram stain) of Enterobacteriaceae species?

A

Gram Negative Rods (e.g. E.coli)

27
Q

What is the classification (i.e. gram stain) of Neisseria species?

A

Gram Negative Diplococci

28
Q

What are some general characteristics of Nonfermenting Gram Negative Rods?

A
  • Predominantly opportunistic
  • Pathogenicity related (usually) to altered/already debilitated host
  • Nomenclature of these organism changes rapidly (new genera defined with use of molecular techniques)
  • do NOT ferment glucose
  • may rapidly develop resistance to antimicrobials use in treatment
29
Q

What is the Catalase test?

A
  • Used to identify organisms that produce the enzyme (catalase)
  • Catalase can breakdown compounds such as hydrogen peroxide (release bubbles ⇒ Catalase positive)
30
Q

What are examples of Catalase Positive bacteria? (Differentiate between Gram stains)

A

Aerobic Gram Positive Cocci

  • Micrococcus
  • Staphylococcus (MRSA)

Aerobic Gram Negative Cocci

  • Moraxella catarrhalis
  • Neisseria gonorrhoeae
  • Neisseria meningiditis
31
Q

What are examples of Catalase Negative bacteria?

A
  • Enterococcus faecalis
  • Enterococcus faecium
  • Streptococcus agalactiae (Group B)
  • Streptococcus pneumoniae
  • Streptococcus pyogenes (Group A)
  • Viridans strept
32
Q

What is the Coagulase test?

A
  • Coagulase clots blood plasma
  • Performed on Gram-positive, catalase-positive Staphylococcus aureus
  • Considered a virulence factor
  • Formation of a clot around an infection most likely protects bacteria from phagocytosis
33
Q

What is a Blood Agar Plate? What are different results observed? (give names)

A

Considered a differential medium, the BAP test observes the ability of an organism to produce hemolysins (enzymes that damage/lyse RBCs – Helpful in differentiating between Streptococcus and Enterococcus species

  • ß-hemolysis = complete hemolysis (transparent zone surround the colonies
  • alpha-hemolysis = partial hemolysis (colonies surrounded by green/opaque zone)
  • gamma hemolysis = no hemolysis (no notable zones)
34
Q

What is a Taxos P?

A

Also termed the Optochin Sensitivity Test, used to distinguish between organisms’ sensitivity to the antibiotic optochin – used to distinguish between Streptococcus pneumonia (sensitive, right side) and other alpha-hemolytic streptococci (resistant, pictured left side)

35
Q

What is a Taxos A?

A

Test used to distinguish organisms that are sensitive to bacitracin (peptide antibiotic, produced by Bacillus subtilis, that inhibits cell wall synthesis and disrupts cell membranes) – commonly used to distinguish between ß-hemolytic streptococci

36
Q

What is a Macconkey Agar?

A

Selective and differential medium used to differentiate between the Enterobacteriaceae species

  • Selective: Bile salts inhibit growth of Gram-positive bacteria
  • Differential: Lactose fermentation is observed as a bright pink-red color from acidic pH
37
Q

What is the Simmon’s Citrate Agar?

A

Distinguishes organisms that are able to use citrate as sole carbon source – differentiate between different Enterobacteriaceae species (bromthymol blue, alkaline pH, is a citrate positive indicator)

Pharm I: Exam 3 (10 decks)

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