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Bacteriology > Other lectures (not drugs or bugs) > Flashcards

Other lectures (not drugs or bugs) Flashcards

1
Q

What are Koch’s postulates?

A
  • Organism must be found in all disease cases, not healthy animals
  • Organism must be isolated from diseased animals and grown in cultures
  • Disease must be reproduced when isolated organism is inoculated into susceptible animals
  • Organism must be isolated from experimentally infected animals
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2
Q

What is the infectious cycle of a pathogen?

A
  • Entry/exit of host
  • Establishment
  • Persistence/Proliferation
  • Host damage
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3
Q

What are the two general mechanisms of cellular invasion?

A

Zipper - ligand binds to receptor, recruits more receptors to bind to ligand, eventually organism is surrounded
Trigger - microbe engages signaling proteins that regulate actin, cytoskeleton engulfs organism

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4
Q

What element is essential for the growth of virtually all bacteria?

A

Iron (patients with increased iron have increased susceptibility to certain infections)

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5
Q

How many layers is the cell envelope of Gram positive bacteria and what are they?

A

Two - Cell wall (thick peptidoglycan layer) and cytoplasmic membrane

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6
Q

How many layers is the cell envelope of Gram negative bacteria and what are they?

A

Three - Outer membrane, cell wall (thin peptidoglycan layer), and cytoplasmic membrane

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7
Q

How many layers is the cell envelope of Acid fast bacteria and what are they?

A

~2.5 - Cytoplasmic membrane, cell wall (thin peptidoglycan layer), and acyl layer

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8
Q

What PRR recognizes the lipoteichoic acid (LTA) of Gram positive bacteria?

A

TLR2

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9
Q

What PRR recognizes the lipopolysaccharide (LPS) of Gram negative bacteria?

A

TLR4

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10
Q

How does Gram staining work?

A

Add crystal violet stain, decolorize but polysaccharide layer retains stain so Gram positive stay purple.
Counter stain with Safranin so Gram negative look pink.

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11
Q

How does acid fast stain work?

A

Stain with carbofuschsin, decolorize but waxes retain stain so acid fast bacteria look pink.
Counter stain with methylene blue so everything else besides acid fast bacteria looks blue.

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12
Q

What enzymes are required for peptidoglycan synthesis?

A

Transglycosylase (links new peptidoglycan monomers)

Transpeptidase (forms peptide cross links between rows and layers of peptidoglycan)

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13
Q

What are the different orientations of flagella on a bacteria?

A

Monotrichous - single flagella
Lophotrichous - multiple from same spot
Amphitrichous - single flagella on each end
Peritrichous - many in all directions (i.e. E. coli)

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14
Q

If a flagella rotates anticlockwise, what type of movement does it cause?

A

Forward movement, swimming

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15
Q

If a flagella rotates clockwise, what type of movement does it cause?

A

Tumbling movement, reorientation

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16
Q

What type of movement do pili/fimbriae cause?

A

Twitching (grappling hook)

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17
Q

What is the function of pili/fimbriae?

A

Adhesion to surfaces

Sometimes conjugation

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18
Q

What is the function of glycocalyx capsule or slime layer?

A

Adhesion (biofilm)

Protects bacteria from phagocytosis

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19
Q

What is the function of endospore?

A
  • Dormant and tough non-reproductive structure that can allow bacteria to survive tough environment
  • Can only be destroyed by burning or autoclaving
  • Seen in Bacillus and Clostridium
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20
Q

What is the function of a plasmid?

A

Transfer genetic elements

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21
Q

What PRR recognizes flagella?

A

TLR5

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22
Q

What is MBC?

A

Minimum bactericidal concentration - the minimum concentration of antimicrobial to kill the bacteria

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23
Q

What is MIC?

A

Minimum inhibitory concentration - the minimum concentration of antimicrobial to prevent growth of organism

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24
Q

When is it necessary to have a bactericidal as opposed to bacteriostatic agent?

A 
Endocarditis (need to get rid of biofilm entirely)
Neutropenic patient (i.e. due to cancer therapy)
Preferred in meningitis (though not proven)
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25
Q

What is the limiting factor in how fast bacteria can grow?

A

How fast they can replicate their DNA

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26
Q

What are the classifications of bacteria based on oxygen requirement?

A

Obligate aerobes - need O2
Obligate anaerobes - O2 kills them, get energy via fermentation
Facultative anaerobes - can grow +/- O2 but prefer O2
Microaerophiles - can withstand low levels of O2

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27
Q

Why is oxygen toxic to anaerobes?

A

Superoxide and hydrogen peroxide are toxic, but anaerobes lack superoxide dismutase and catalase/peroxidase

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28
Q

What are the classifications of bacteria based on temperature?

A

Mesophiles: best from 30-45 C (includes most pathogenic bacteria)
Thermophiles: 55-75 C (hot springs)
Psychrophiles: temps below 20 C

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29
Q

What are the phases of the bacterial growth curve?

A

Lag phase: slow growth, get acclimated to environment
Log phase: multiply exponentially
Stationary phase: competition for food and nutrients, growth stops
Decline phase: toxic waste builds up, bugs die

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30
Q

What is the formula for generation time (or doubling time)?

A

g = t/n

g = generation time
t = time interval
n = number of generations (number of times population doubles during time interval)
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31
Q

How can you determine how much bacteria was in an original sample?

A

Pour Plate
Serially dilute original sample and plate.
Each spot is colony forming unit (CFU) derived from 1 bacterium that increased in size by binary fission.
Count number of CFUs on plate of a certain dilution and backtrack.

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32
Q

What are characteristics of a biofilm?

A

Microbes that are:

  • Attached to hydrated surface
  • Embedded in polysaccharide slime
  • Behave as a community
  • Demonstrate antibiotic resistance and resistance to clearance by host immune system
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33
Q

What is the progression of a biofilm?

A

Single cells come in and attach –> early structure –> mature biofilm –> seeding dispersal

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34
Q

What is the main type of biofilm associated infection?

A

Indwelling medical device

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35
Q

Why are biofilms resistant to antibiotics?

A
  • Reduce antibiotic penetration
  • Cells within a biofilm are very slow growing
  • Stress response genes can allow it to resist antibiotic action
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36
Q

Can you culture a biofilm?

A

No

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37
Q

Definition of asepsis

A

State of being free of microorganisms

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38
Q

Definition of sterilization

A

Inactivation or elimination of ALL organisms and their spores

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39
Q

Definition of disinfection

A

Inactivation or elimination of MOST microorganisms

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40
Q

Definition of sanitization

A

REDUCES pathogen levels

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41
Q

Definition of germicide

A

Substance that kills vegetative bacteria and SOME spores

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42
Q

Definition of disinfectant

A

Kills vegetative bacteria, fungi, viruses but NO spores

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43
Q

Definition of antiseptic

A

Prevents multiplication of microorganism (bacteriostatic , not bactericidal)

44
Q

What are methods of physical sterilization?

A

Autoclave (moisture, heat and pressure)
Hot air sterilization (for materials that would be damaged by moist heat)
Filtration disinfection (for liquids)
Radiation (ionizing via gamma)

45
Q

What are methods of chemical sterilization?

A

Ethylene oxide (toxic)
Alcohols
Halogens (basically bleach)

46
Q

What are implications of biofilms on Infectious Disease?

A
  • Inaccurate MIC/MBC preduction of bacterial populations in situ
  • Inaccurate CFU determination from clinical samples
47
Q

What is the definition of an outbreak?

A

Incidence of an event / expected rates (endemic)

48
Q

What is the definition of a pandemic?

A

A worldwide epidemic

49
Q

What are the steps of an outbreak investigation?

A
  • Prevent further cases
  • Develop a case definition
  • Conduct surveillance
  • Build epidemic curve
  • Summarize data on case patients in a line listing
  • Develop and test a hypothesis of what caused outbreak
  • Institute and assess efficacy of intervention
50
Q

What is a case definition?

A

Defines the disease (clinical symptoms, signs and diagnostic tests) with restrictions on time, person, and place

51
Q

Definition of sensitivity of case definition

A

Ability to correctly identify those who have new infection

52
Q

Definition of specificity of case definition

A

Ability to correctly identify those who do not have new infections (want this to be high to minimize false positives)

53
Q

What information can be gained from an epidemic curve?

A

Whether infection is point source v. ongoing transmission

Incubation period

54
Q

What should a outbreak hypothesis explain?

A

Mode of transmission

Source of outbreak

55
Q

What is a plasmid?

A

Small, self-replicating extrachromosomal circle of DNA

  • Can be transferred from one bacterium to another (conjugative plasmid)
  • Can encode antibiotic resistance
56
Q

What is a transposon?

A

Jumping genes that cannot replicate independently, but must be inserted into another replicon (plasmid, chromosome, or phage)

  • Often encode antibiotic resistance
  • Usually inactivates target genes and can cause rearrangements
57
Q

What is on either end of a transposon?

A

Inverted repeats

58
Q

Lytic v. lysogenic bacteriophage

A

Lytic - immediately lyse and kill cell
Lysogenic - phage DNA incorporated into bacterial chromosome and encode virulence factors (like toxins i.e. diphtheria toxin, Shiga toxin)

59
Q

What is a pathogenicity island?

A

Large block of DNA containing multiple virulence genes, located in a region of “house-keeping” genes
i.e. E. coli LEE pathogenicity island

60
Q

What are the 3 basic mechanisms of genetic exchange in bacteria?

A

Transformation
Conjugation
Transduction

61
Q

Definition of bacterial transformation

A

Naked DNA from one cell taken up by another cell through the cell wall

62
Q

Definition of bacterial conjugation

A

Genetic transfer via cell-to-cell contact (bacteria sex)

63
Q

Definition of bacterial transduction

A

Transfer of DNA between bacteria by viruses

64
Q

What is quorum sensing?

A

Mechanism by which bacteria secrete a low molecular weight compound that signals other bacteria to turn on specific gene expression (this only happens at high bacterial density when signalling compound is at sufficient concentration)

65
Q

What is the main way that antibiotic resistance factors are spread?

A

Conjugative plasmids (especially in Gram neg bacteria)

66
Q

Should you use antibiotics for otitis media with effusion?

A

No! Could be remnants of previous acute otitis media infection, usually asymptommatic and not bacterial

67
Q

How can you distinguish between acute otitis media v. otitis media with effusion?

A

Physical exam.
AOM - bulging tympanic membrane, no light reflex
Otitis media with effusion - air fluid level visible, concave tympanic membrane

68
Q

What are the three major organisms that cause bacterial acute otitis media?

A

Moraxella catarrhalis
Strep pneumoniae
Haemophilus influenzae

69
Q

What is the primary treatment of acute otitis media?

A

Amoxicillin

“wait and see” is also an option

70
Q

What is a major complication of acute otitis media?

A

Mastoiditis (purulent material accumulate in mastoid cavity)

71
Q

What are the three major organisms that cause bacterial sinusitis?

A

Moraxella catarrhalis
Strep pneumoniae
Haemophilus influenzae
(same as acute otitis media)

72
Q

What is the primary treatment of sinusitis?

A

Amoxicillin/clavulanate

73
Q

What is a major complication of sinusitis?

A

Orbital cellulitis - proptotic, muscle stranding and swelling

74
Q

What is the major organism that causes pharyngitis?

A

Group A beta hemolytic strep (Strep pyogenes)

75
Q

What is the primary treatment for pharyngitis from Group A Strep (Strep pyogenes)?

A

Penicillin! resistance remains low

76
Q

What are major complications of Strep pharyngitis?

A

Acute rheumatic fever

Glomerulonephritis

77
Q

What are major pathogens that cause typical bacterial pneumonia?

A

Strep pneumoniae
H. influenzae
Staph aureus
Group A strep (Strep pyogenes)

78
Q

What are major pathogens that cause atypical pneumoniae?

A

VIRUSES (#1!)
Mycoplasma pneumoniae
Chlamydophila pneumoniae
Legionella pneumoniae

79
Q

How can you differentiate from typical v. atypical pneumoniae?

A

Typical - usually lobar, pulmonary symptoms (pleuritic chest pain, purulent cough)
Atypical - usually diffuse, extrapulmonary symptoms (fatigue, sore throat, nonproductive cough)

80
Q

What is the primary treatment for atypical pneumonia?

A

Macrolides (azithro)

81
Q

What can precede the development of severe pneumonia due to S. aureus?

A

Influenza infection

82
Q

What are major pathogens that can cause severe pneumonia?

A

Strep pneumoniae
H. influenza
Mycoplasma

If very severe, worry about Legionella, S. aureus (MRSA)

83
Q

What is the treatment for a low risk outpatient pneumonia patient?

A

Azithromycin (macrolide)

84
Q

What is the treatment for a high risk outpatient or low risk inpatient pneumonia (assume they had antibiotic in past 3 months)?

A

Fluoroquinolone

85
Q

What is the treatment for a very high risk ICU pneumonia patient?

A

Broad beta lactam + azithro/fluoroquinolone

86
Q

In what group of patients should you treat asymptomatic bacteriuria?

A

Pregnant women since its associated with premature and low birthweight babies

87
Q

What factors will make a UTI complicated as opposed to uncomplicated?

A 
History of childhood UTIs
Immunocompromised
Preadolescent or postmenopausal
Pregnant
Underlying metabolic disorder (diabetes)
Urologic abnormalities (catheters, stones, etc.)
88
Q

What is most common organism that causes UTIs?

A

E. coli

89
Q

How does cystitis commonly present?

A

LUTS (lower urinary tract symptoms like burning)

Frequency of urination and urgency of urination

90
Q

What is the first line of treatment for UTIs?

A

Nitrofurantoin
Fosfomycin
TMP-SMX

91
Q

How does acute pyelonephritis commonly present?

A

Flank pain
Shaking chills (rigor)
Fall in blood pressure
Nausea and vomiting

92
Q

What is treatment for Acute pyelonephritis?

A

Usually fluoroquinolone like ciprofloxacin

If more serious/local fluoroquinolone resistance >10%, can give initial IV dose of ceftriaxone

93
Q

Why are pediatric UTIs particularly dangerous?

A

Sometimes associated with veiscoureteral reflux, can pool in the bladder
Can cause renal scarring

94
Q

What are common causes of acute gastroenteritis?

A

Preformed toxins such as:

  • Staph aureus enterotoxins
  • Clostridium perfingens enterotoxin
95
Q

What is clinical presentation of acute gastroenteritis?

A

Abrupt onset of severe nausea, vomiting, diarrhea

Lasts less than 24 hours

96
Q

What is the clinical presentation of acute non-inflammatory diarrhea?

A

Watery diarrhea without blood or mucus

97
Q

What is the most important treatment in diarrheal disease management?

A

Rehydration therapy!

98
Q

What are common causes of acute non-inflammatory diarrhea?

A

ETEC, EAEC, EPEC
Vibrio cholera
Campylobacter, Salmonella, Shigella

99
Q

What are key components of oral rehydration solution?

A

Sodium and glucose

Increases absorption via sodium/glucose transporter and repletes volume

100
Q

What is clinical presentation of acute inflammatory diarrhea?

A

Fever, chills, malaise, abdominal pain and diarrhea
Stools may contain mucus or blood
Dysentery is severe form of this

101
Q

What is clinical presentation of dysentery?

A

Severe form of acute inflammatory diarrhea

Frequent small bowel movements with blood/mucus, urge to defecate, painful defecation (tenesmus)

102
Q

What are common causes of acute inflammatory diarrhea?

A

C. diff (especially in hospitalized patients or those recently on antimicrobials)
Campylobacter, Salmonella, Yersinia, EAEC
Shigella can cause dysentery

103
Q

What lab finding indicates acute inflammatory diarrhea?

A

Fecal leukocytes

104
Q

What is treatment for C. diff?

A

Metronidazole
Vancomycin if severe
Fidaxomycin for relapses

105
Q

What is treatment for V. cholerae?

A

Oral rehydration primarily

Can give tetracycline to shorten diarrhea time

106
Q

What is treatment Shigella?

A

Check resistances, usually okay with cipro

107
Q

What is treatment for acute inflammatory diarrhea PRIOR to getting culture?

A

DO NOT give antibiotics if you see bloody diarrhea or suspect salmonella

  • Could be EHEC, would increase risk of HUS
  • Could be salmonella, wouldn’t have effect on duration

Otherwise usually okay with cipro

Bacteriology (19 decks)

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