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MB1: Principles > Microbiology > Flashcards

Microbiology Flashcards

1
Q

describe layers of peptidoglycan relative to gram staining

A

Gram positive bacteria have a thicker peptidoglycan layer than gram negative bacteria and so stain a darker purple

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2
Q

what is the endotoxin and where is it found

A

lipopolysaccharide, contains toxins and antigens and is the outer cell membrane of gram negative bacteria

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3
Q

what are targets for antimicrobials

A 
Cell membrane 
Cell wall
Protein synthesis
DNA
Ribosomes
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4
Q

what appendages do bacteria have to aid movement

A

Gram positive have fimbriae, non flagella protein appendages

Gram negative have pili, which is absent of a motor

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5
Q

What are the requirements for prokaryotic growth

A 
Food
Temperature 
pH
Osmotic protection
Oxygen, or lack thereof
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6
Q

Growth phases of bacteria

A

Lag
Exponential phase
Stationary phase
Decline/Death phase

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7
Q

What is a mesophile

A

Bacteria which are optimum at body temperature

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8
Q

How is an abscess formed

A

bacteria secrete toxins to break down tissues for nutrients

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9
Q

Bacilli

A

Rod shaped

Exist in isolation or chains

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10
Q

Cocci

A

Can form chains called streptococci

Can form clusters called staphylococci

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11
Q

Spiral corkscrew

A

Rigid - spirillum
flexible - spirochaete
operate best in viscous environment

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12
Q

Fusiform

A

Stillbirth

Long and slender

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13
Q

Curved rods

A

Gram negative

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14
Q

Why are bacteria with capsules more virulent

A

Complement system cannot bind to these bacteria as effectively

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15
Q

Classes of oxygen tolerance

A 
Capnophilic 
Aerobic
Obligate aerobe
Obligate anaerobe 
Facultative anaerobes
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16
Q

What is selective media

A

identifies bacteria by presence of specific substances permitting its growth

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17
Q

What is differential media

A

incorporation of chemicals to provide visible changes in colonies for identifying

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18
Q

What are the different types of heamolysis and what does it mean

A

Alpha - colony greening, identifies Viridans group and lancefield D
Beta - discolouration of blood agar, pyrogens and lancefield A, B, C, F, G
Gamma - no heamolysis

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19
Q

qPCR does what?

A

amplifies DNA on bacteria to indicate presence of a specific microbe

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20
Q

What does MALDI-TOF do?

A

puts analyte into gas phase to separate ions by mass to charge ratio for identifying microbes

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21
Q

What is agglutination

A

Clumping together of cells due to antibodies binding to their antigens

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22
Q

What is metabolic profiling

A

uses carbon sources and exo enzyme production to identify microbes

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23
Q

what are exo enzymes

A

what is metabolised by microbe

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24
Q

What does a positive coagulase indicate

A

Staph Aureus

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25
Q

What are serological tests

A

detection of IgM antibody to microbe in vitro by agglutination

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26
Q

What is the difference between polyclonal and monoclonal antibodies

A

Polyclonal - specific to microbe

Monoclonal - specific to single component

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27
Q

Describe the structure of viruses

A

Protein coat
Envelope
Genetic information as RNA or DNA

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28
Q

Structure of a virus in terms of shape

A

Helical

Icosahedral

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29
Q

Describe the virus life cycle

A 
Attachment 
Entry
Uncoating 
Nucleic acid and protein synthesis
Assembly 
Release
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30
Q

Why are viruses harder to develop drugs against

A

they have less structures to target

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31
Q

Where is antiviral resistance most common

A

Immunocomproised patients

32
Q

Types of immunity to viruses

A

Innate
Humoural
T-cell recognises non self antigens and invokes apoptosis

33
Q

How are viruses identified

A

PCR, antigen detection
NGS, mass spectroscopy
Electron microscopy and culture - falling out of use

34
Q

What are endogenous bacteria

A

Bacteria from inside the body in gut flora, can occasionally be pathogenic in some circumstances

35
Q

What are exogenous bacteria

A

Bacteria from outside the body, they can be pathogenic

36
Q

What are oppertunistic pathogens

A

an organism that causes infection given an opportunity

37
Q

what is virulence

A

capacity of a microbe to cause disease

38
Q

What is a pathogen

A

disease causing microorganism

39
Q

Yeast infection? What can it form?

A

Candida spp.

Hyphae, spike growing down epithelial cells

40
Q

Types of protozoan disease?

A

Malaria and toxoplasma

41
Q

2 main types of gram negative cocci

A

Neisseria meningitidis (most common meningitis) and gonnorhoeae

42
Q

Endogenous coliforms

A

E coli
Proteus spp
Klebsiella spp
Enterobacter spp

43
Q

Exogenous pathogenic coliforms

A

Salmonella spp
Shigella spp
Ecoli 0157, 0104 - producing verotoxin

44
Q

Treatment for coliform infections?

A

Gentamycin

45
Q

True/false - any coliform can cause an infection

A

True- even endogenous coliforms can cause infection in sterile sites such as the urinary tract

46
Q

What causes acute antibiotic associated diarrhoea?

A

Clostridium difficile

Most common in vulnerable patients in absence of normal gut flora due to removal by broad spectrum antibiotics

47
Q

What class is C. diff and what can it produce

A

Can produce spores

Gram positive anerobic bacilli

48
Q

2 types of staphylococci and how they appear

A

Clusters
Staph Aureus - wound and skin infection. coagulase positive and can become MRSA
Staph epidermis

49
Q

How does streptococci appear, what types are there and how are they identifed

A 
Chains of streptococci
identified by heamolysis
Alpha - strep pneumoniae 
Beta - pygrogenes, group A
Gamma - Enterococcus spp - can either be very sensitive to amoxicillin or very resistant
50
Q

Why do patients with coliform sepsis get so ill so fast

A

Release of endotoxin from bacteria when they die

51
Q

What dies the endotoxin cause the immune system to release

A

Acute phase cytokines

52
Q

What do acute phase cytokines do

A

Can cause release of prostaglandin E at hypothalamus to cause fever or can lead to sepsis

53
Q

What do beta lactams target

A

Bacterial cell wall, penicillin binding protein by mimicking D-alanine D-alanine dipeptide to compromise cell wall

54
Q

Types of beta lactams

A

Penicillins

Cephalosporins

55
Q

What penicillin is the first line broad spectrum

A

Amoxicillin

56
Q

What is given when bacteria are beta lactamase and resistant to amoxicillin

A

Co-amoxiclav, containing clavulanic acid to inhibit beta lactamase

57
Q

What is given for staph or strep

A

Flucloxacillin, MRSA is resistant to it

58
Q

what penicillin is active against ESBL

A

Temocillin, but only really coliforms as gram negative

59
Q

Where are penicillins excreted?

A

Kidneys and urine

60
Q

True/false - cephalosporins are bacteriostatic

A

False- they are bacteriocidal

61
Q

why are cephalosporins not used as much anymore?

A

they can cause C. diff due to them being so broad spectrum

62
Q

What antibiotic would be given for MRSA

A

vancomycin - part of bacteriocidal glycopeptides but are not beta lactams

63
Q

First line antibiotic gentamycin and issues

A

only gram negative and IV, bacteirocidal

toxic to kidneys as well as VIII cranial nerve

64
Q

What antibiotics can be used to treat intracellular pathogens

A

Macrolides

65
Q

How do tetracyclines work

A

reversibly bind to 30S ribosomes, but can damage intestinal flora. teteacycline and doxycycline

66
Q

What is trimethoprim often used to treat

A

UTI - excreted via urine. can be given on its own or in combination with a sulphonamide

67
Q

What type of antibiotics increase risk of c. diff in vulnerable patients

A

broad spectrum

68
Q

Never combine …

A

bacteriostatic and bacteriocidal

69
Q

What antibiotics are avoided?

A 
4 Cs 
Cephalosporins 
Co-amoxiclav
Clindamycin
Ciprofloxacin
70
Q

What is natural resistance?

A

Absence of target required for antibiotic or presence of persistor cells or biofilms - antibiotics cannot reach inside of these

71
Q

how is antibiotic resistance passed onto other bacteria?

A

Horizontal gene transfer

72
Q

What is the difference between cross resistance and multiple resistance

A

cross resistance is the resistance to related antibiotics where multiple resistance is resistance to unrelated antibiotics

73
Q

3 types of resistance to beta lactams

A

Penicillinase - penicillin resistant
ESBL (extended spectrum beta lactamase) - penicillin and cephalosporin resistant as well as monobactams
Carbapenemase - resistance to penicillins, cephalosporins and carbapenems (last resort antibiotics such as colistin)

74
Q

How is resistance increased

A

unnecessary antibiotics or ones in sub therapeutic doses

75
Q

5Is

A 
inhalation 
ingestion 
intercourse 
mother to infant 
inoculation
76
Q

5 hand hygiene moments

A 
before patient contact
before aseptic task 
after body fluid exposure 
after patient contact 
after patient environment contact

MB1: Principles (10 decks)

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