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BAMS > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What is a gram stain?

A

The gram-staining characteristics of bacteria are denoted as positive or negative, depending upon whether the bacteria take up and retain the crystal violet stain or not.

Gram negative - pink
Gram positive - violet

Due to gram positive having thick peptidoglycan layer and absorbing violet dye

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2
Q

What is mass spectroscopy?

A

An analytical technique that ionizes chemical species and sorts the ions based on their mass-to-charge ratio.

MALDI-TOF used specifically in microbiology to identify microbes

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3
Q

What is a coagulase test used for?

A

To differentiate s.aureus from coagulase negative staphylcoccus (CONS)

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4
Q

What is antimicrobial susceptibility testing?

A

Used to determine which antibiotics a specific bacterium or fungi is sensitive to

VITEK

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5
Q

What are three common features of both eukaryotes and prokaryotes?

A

Cells
Cell membrane
Ribosomes

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6
Q

What features are specific to a prokaryote?

A

Circular DNA

Nucleoid

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7
Q

What features are specific to eukaryotes?

A

Organelles
Linear DNA
Nucleus

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8
Q

What is meant by aerobic?

A

Oxygen

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9
Q

What is meant by capnophilic?

A

Carbon dioxide

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10
Q

What is meant by facultative?

A

With or without oxygen

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11
Q

What is meant by anaerobic?

A

Without oxygen

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12
Q

What is meant by microaerophilic?

A

Require small amounts of oxygen

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13
Q

What is binary fission?

A

Asexual reproduction - splits in half

Occurs in prokaryotes and in some single celled eukaryotes e.g. amoeba

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14
Q

What are the phases of bacterial growth?

A

Lag
Log
Stationary
Death

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15
Q

What are the components of a bacterial cell?

A 
Outer capsule
Flagellum
Pili
Circular DNA
Ribosomes
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16
Q

What are rod shaped bacterium?

A

Bacilli

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17
Q

What are round shaped bacterium?

A

Cocci

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18
Q

Describe how to conduct a gram stain.

A

Stain with crystal violet
After mordant, iodine
After decolorizer, alcohol or acetone
After counterstain, safrinin

Gram -ve - pink
Gram +ve - purple

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19
Q

What is a peptidoglycan layer?

A

Peptide chains joined by pentaglycine interbridges

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20
Q

What are lipopolysaccharides?

A

Large molecules consisting of a lipid and a polysaccharide composed of O-antigen, outer core and inner core joined by a covalent bond

LPS (Prevotella intermedia) is an endotoxin and causes an acute inflammatory response

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21
Q

What does S.mutans cause?

A

Caries

Gram positive

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22
Q

What are three examples of gram positive bacteria?

A

S. aureus
S. mutans
C. difficile

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23
Q

What does C.difficile cause?

A

Colitis, produces toxins that affect colon

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24
Q

What are examples of gram negative bacteria?

A

Neisseria meningitidis

Prevotella intermedia

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25
Q

What is an example of non-selective growth agar?

A

Blood agar

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26
Q

What is an example of selective growth agar?

A

Mannitol (A sugar)

Salt (selects growth of staphylococci)

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27
Q

What is colonization?

A

The presence of MOs in or on the host, with growth and multiplication, but without any overt clinical expression (infection)

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28
Q

What is infection?

A

Invasion of the body by pathogenic microbes and the reaction of the tissues to their presence and to the toxins generated by them

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29
Q

What is a pathogen?

A

An organism which can invade the body and cause disease

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30
Q

What are the risk factors for S.aureus colonisation?

A

Antibiotic use
Diabetic, renal dialysis, HIV, obesity
Hospitilisation
Colonised partner

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31
Q

How many people are generally on average persistent S.aureus carriers?

A

20% (12-30%)

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32
Q

What are the beneficial impact of fungis?

A

Decomposers
Industrial fermentations
Research - model eukaryotic organisms

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33
Q

What is the detrimental impact of fungi?

A

Major cause of plant diseases

Cause of many animal, including human, diseases

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34
Q

What is mycology?

A

The study of fungi

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35
Q

What are mycologists?

A

Scientists who study (pathogenic) fungi

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36
Q

What is mycotoxicology?

A

Study of fungal toxins and their effects

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37
Q

What are mycoses?

A

Diseases caused by fungi

38
Q

What is Malassezia globosa?

A

Dandruff-causing fungi on scalp

39
Q

What is onychomycosis?

A

Infection of the nails

40
Q

What causes athletes foot?

A

Tinea pedis

41
Q

What are different microbiological diagnostic tools?

A 
Smear
Oral Rinse
Swab
Foam pad
Biopsy
42
Q

What are examples of dimorphic fungi?

A

Blastomyces dermatiditis
Coccidiodes immitis
Histoplasma capsulatum
Paracoccidioides brasiliensis

43
Q

What are examples of opportunistic fungi?

A

Candida albicans
Cryptococcus neoformans
Aspergillus umigatus

44
Q

What is the capsule of cryptococcus composed of?

A

Glucoronic acid and mannose

45
Q

What does cryptococcus cause?

A

Meningitis in AIDS patients

46
Q

What is an example of a mould?

A

Aspergillus

47
Q

How do we treat fungal infections?

A

(1,3)-β-d-glucan synthase inhibitors

ergosterol-directed antimycotic agents

48
Q

What are the general properties of a virus?

A

Small size (nm)
Genome - RNA or DNA
Metabolically inert - Do not possess ribosome/protein synthesis
Some have enzymes

49
Q

What is a virion?

A

Complete virus particle

50
Q

What can the virion be split into?

A

The envelope - lipid membrane around some viruses

Capsid - protein shell

51
Q

What does the capsid consist of?

A

Capsomers - protein units that make up the capsid

52
Q

What is inside the capsid?

A

Nucleic acid genome - DNA or RNA

53
Q

How are viruses transmissible?

A 
Inhalation via respiratory tract
Ingestion via GI tract
Inoculation - skin abrasion, mucous membranes, tranfusions, transplants, injections, bites
Congenital - mother to foetus
Sexual transmission
54
Q

What are the three effects of viruses on cells?

A

Cell death
Transformation - cell not killed, changed to cancerous cell
Latent infection - remains in cell, no obvious effect on cell function

55
Q

What are the stages of viral infection?

A 
Attachment
Penetration
Uncoating
Synthesis of viral components
Assembly 
Release
56
Q

What are viral structural proteins?

A

Components for the capsid and envelope

57
Q

What are viral non-structural proteins?

A

Coded for by the genome of the virus and expressed in infected cells

58
Q

What are the two ways viruses can be released from a cell?

A

Rupture

Gradual extrusion

59
Q

How many types of influenza viruses are there?

A

RNA viruses

There are type A, B and C

60
Q

What are the two types of spikes that can exist on influenza viruses?

A

H spike

N spike

61
Q

What is Haemagglutinin?

A

A glycoprotein found on the surface of influenza viruses that is integral to its infectivity

Binds sialic acid on target cell
14 H types

62
Q

What is Neuroaminidase?

A

A glycoprotein on the surface of an influenza viruses that enables it to be released from a host cell

Cleaves sialic acid
9 N types

63
Q

What is antigenic drift?

A

Minor change
Point mutations
Epidemic
A, B and C drift

64
Q

What is antigenic shift?

A

Major change
Recombination
Pandemics
Only A

65
Q

What does the 2018/19 quadrivalent inactivated flu vaccine contain?

A

Flu A Michingan Strain
Flu A Singapore Strain
Flu B (victoria lineage)
Flu B (Yamagata lineage)

66
Q

What specimen can be used in clinical virology?

A

Swabs, faeces, aspirates, plama, CSF, vesicle fluids, urine

Plasma - monitoring by PCR
Serum - Serology - antibody titres

67
Q

What is a direct diagnostic method?

A

Molecular - PCR - use primers specific to suspected viral DNA
End up with 68billion copies of wanted gene - used for DNA sequencing

68
Q

What is an indirect diagnostic method?

A

Serology - ELISA/Western blotting

69
Q

What is vCJD?

A

Variant Creutzfeld-Jakob Disease

70
Q

What are the 6 stages of ‘the chain of infection’?

A
  1. The infectious agent
  2. The reservoir
  3. The portal of exit
  4. The mode of transmission
  5. The portal of entry
  6. The susceptible host
71
Q

What are prions?

A

Infectious agent devoid of nucleic acid

Disease due to the accumulation of an abnormal form of a natural protein

Conformational changes associated with a specific disease

Most common disease caused by prions in vCJD

72
Q

How does a prion cause vCJD?

A

Conversion of alpha helix prion (PrPc) to the infectious beta pleated sheet prion (PrPsc)

73
Q

What is the reservoir specific to the BSE epidemic?

A

Most cases in UK occurred in dairy cows ages 3-6 years.

Changes in rendering process in 80s allowed aetiological agent to survive

74
Q

How widespread is vCJD?

A

Approx 1 in 2000

Disease is rare but infection relatively common

75
Q

What tissues/systems are? high in both sCJD and vCJD

A

CNS

Optic nerve and retina

76
Q

What tissues/systems show specifically more presence of vCJD than sCJD?

A

Appendix, tonsil, spleen (lymphoid organs)

77
Q

Where in the oral cavity can vCJD exist?

A

Tonsils and trigeminal ganglia

78
Q

Wha tare the mode of transmission for CJD?

A 
Grafts
Surgical instruments
Transplants
Blood transfusions
Hormone administration
79
Q

What oral tissues (if any) become infective?

A

Gingival margin shown to have highest level of infectivity in oral cavity

80
Q

Can infection be transmitted via the oral route?

A

Gingival margin capable of supporting transmission of disease with high efficiency

81
Q

How many cases of vCJD did not have a homozygous genotype?

A

1

82
Q

Why are there so few clinical cases of vCJD?

A

Significant species barrier with rare exposure of sufficient dose to result in infection
Genetic heterogeneity with longer incubation periods and/or lower susceptibility to infection

83
Q

What precautions are necessary when providing dental treatment for CJD cases?

A

Standard infection control procedures

84
Q

What was Koch’s postulates?

A

The germ theory of disease

  • The microbe must be present in every case of the disease
  • Microbe must be isolated from the diseased host and grown in pure culture
  • Disease must be reproduced when a pure culture is introduced into a susceptible host
  • The microbe must be recovered from an experimentally infected host
85
Q

What components are sometimes (instead of usually) present in eukaryotic cells?

A
  • Capsule
  • Inclusion granules
  • Fimbrae
  • Flagellum
  • Membranous invagination
86
Q

Where is pili found?

A

aka Fimbrae
Found in almost all Gram negative
Overcome mechanical forces

87
Q

What is the host defence mechanism against UTIs?

A

Flushing action of urine

Tamm-Horsfall protein helps bind specific e.coli strains

88
Q

How does e.coli circumvent the flushing action in the urinary tract?

A

They produce specialised adhesive structures

Adheres to bladder mucosal cells

89
Q

What is the capsular function?

A

Mediate adhesion
Immun evasion
Protection from dessication
Reserves of CHOs
Encapsulated bacteria give rise to smooth colonies
Capsule material gives rise to ‘capsular antignes’

90
Q

What are the ways a pathogen can avoid immune system?

A

IgA protease secretion
Variable surface coat
Variable pilus antigens
Capsule inhibits phagocyte ingestion

91
Q

What are the ways in which a pathogen can cause damage?

A

Release of endotoxin (LPS) or teichoic acid - promotes IL-1 and TNF production which results in fever and sock

Exotoxin production - many toxin-mediated damage pathways

92
Q

What are the different microbial attachment methods for the pathogen?

A

Pili
Lectin
Host mimicry
Slime/bioflim

BAMS (14 decks)

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