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Microbiology Flashcards

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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
What is an example of non-selective growth agar?
Blood agar
26
What is an example of selective growth agar?
Mannitol (A sugar) | Salt (selects growth of staphylococci)
27
What is colonization?
The presence of MOs in or on the host, with growth and multiplication, but without any overt clinical expression (infection)
28
What is infection?
Invasion of the body by pathogenic microbes and the reaction of the tissues to their presence and to the toxins generated by them
29
What is a pathogen?
An organism which can invade the body and cause disease
30
What are the risk factors for S.aureus colonisation?
Antibiotic use Diabetic, renal dialysis, HIV, obesity Hospitilisation Colonised partner
31
How many people are generally on average persistent S.aureus carriers?
20% (12-30%)
32
What are the beneficial impact of fungis?
Decomposers Industrial fermentations Research - model eukaryotic organisms
33
What is the detrimental impact of fungi?
Major cause of plant diseases | Cause of many animal, including human, diseases
34
What is mycology?
The study of fungi
35
What are mycologists?
Scientists who study (pathogenic) fungi
36
What is mycotoxicology?
Study of fungal toxins and their effects
37
What are mycoses?
Diseases caused by fungi
38
What is Malassezia globosa?
Dandruff-causing fungi on scalp
39
What is onychomycosis?
Infection of the nails
40
What causes athletes foot?
Tinea pedis
41
What are different microbiological diagnostic tools?
``` Smear Oral Rinse Swab Foam pad Biopsy ```
42
What are examples of dimorphic fungi?
Blastomyces dermatiditis Coccidiodes immitis Histoplasma capsulatum Paracoccidioides brasiliensis
43
What are examples of opportunistic fungi?
Candida albicans Cryptococcus neoformans Aspergillus umigatus
44
What is the capsule of cryptococcus composed of?
Glucoronic acid and mannose
45
What does cryptococcus cause?
Meningitis in AIDS patients
46
What is an example of a mould?
Aspergillus
47
How do we treat fungal infections?
(1,3)-β-d-glucan synthase inhibitors ergosterol-directed antimycotic agents
48
What are the general properties of a virus?
Small size (nm) Genome - RNA or DNA Metabolically inert - Do not possess ribosome/protein synthesis Some have enzymes
49
What is a virion?
Complete virus particle
50
What can the virion be split into?
The envelope - lipid membrane around some viruses Capsid - protein shell
51
What does the capsid consist of?
Capsomers - protein units that make up the capsid
52
What is inside the capsid?
Nucleic acid genome - DNA or RNA
53
How are viruses transmissible?
``` Inhalation via respiratory tract Ingestion via GI tract Inoculation - skin abrasion, mucous membranes, tranfusions, transplants, injections, bites Congenital - mother to foetus Sexual transmission ```
54
What are the three effects of viruses on cells?
Cell death Transformation - cell not killed, changed to cancerous cell Latent infection - remains in cell, no obvious effect on cell function
55
What are the stages of viral infection?
``` Attachment Penetration Uncoating Synthesis of viral components Assembly Release ```
56
What are viral structural proteins?
Components for the capsid and envelope
57
What are viral non-structural proteins?
Coded for by the genome of the virus and expressed in infected cells
58
What are the two ways viruses can be released from a cell?
Rupture | Gradual extrusion
59
How many types of influenza viruses are there?
RNA viruses | There are type A, B and C
60
What are the two types of spikes that can exist on influenza viruses?
H spike | N spike
61
What is Haemagglutinin?
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
What is Neuroaminidase?
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
What is antigenic drift?
Minor change Point mutations Epidemic A, B and C drift
64
What is antigenic shift?
Major change Recombination Pandemics Only A
65
What does the 2018/19 quadrivalent inactivated flu vaccine contain?
Flu A Michingan Strain Flu A Singapore Strain Flu B (victoria lineage) Flu B (Yamagata lineage)
66
What specimen can be used in clinical virology?
Swabs, faeces, aspirates, plama, CSF, vesicle fluids, urine Plasma - monitoring by PCR Serum - Serology - antibody titres
67
What is a direct diagnostic method?
Molecular - PCR - use primers specific to suspected viral DNA End up with 68billion copies of wanted gene - used for DNA sequencing
68
What is an indirect diagnostic method?
Serology - ELISA/Western blotting
69
What is vCJD?
Variant Creutzfeld-Jakob Disease
70
What are the 6 stages of 'the chain of infection'?
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
What are prions?
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
How does a prion cause vCJD?
Conversion of alpha helix prion (PrPc) to the infectious beta pleated sheet prion (PrPsc)
73
What is the reservoir specific to the BSE epidemic?
Most cases in UK occurred in dairy cows ages 3-6 years. Changes in rendering process in 80s allowed aetiological agent to survive
74
How widespread is vCJD?
Approx 1 in 2000 | Disease is rare but infection relatively common
75
What tissues/systems are? high in both sCJD and vCJD
CNS | Optic nerve and retina
76
What tissues/systems show specifically more presence of vCJD than sCJD?
Appendix, tonsil, spleen (lymphoid organs)
77
Where in the oral cavity can vCJD exist?
Tonsils and trigeminal ganglia
78
Wha tare the mode of transmission for CJD?
``` Grafts Surgical instruments Transplants Blood transfusions Hormone administration ```
79
What oral tissues (if any) become infective?
Gingival margin shown to have highest level of infectivity in oral cavity
80
Can infection be transmitted via the oral route?
Gingival margin capable of supporting transmission of disease with high efficiency
81
How many cases of vCJD did not have a homozygous genotype?
1
82
Why are there so few clinical cases of vCJD?
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
What precautions are necessary when providing dental treatment for CJD cases?
Standard infection control procedures
84
What was Koch's postulates?
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
What components are sometimes (instead of usually) present in eukaryotic cells?
- Capsule - Inclusion granules - Fimbrae - Flagellum - Membranous invagination
86
Where is pili found?
aka Fimbrae Found in almost all Gram negative Overcome mechanical forces
87
What is the host defence mechanism against UTIs?
Flushing action of urine | Tamm-Horsfall protein helps bind specific e.coli strains
88
How does e.coli circumvent the flushing action in the urinary tract?
They produce specialised adhesive structures | Adheres to bladder mucosal cells
89
What is the capsular function?
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
What are the ways a pathogen can avoid immune system?
IgA protease secretion Variable surface coat Variable pilus antigens Capsule inhibits phagocyte ingestion
91
What are the ways in which a pathogen can cause damage?
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
What are the different microbial attachment methods for the pathogen?
Pili Lectin Host mimicry Slime/bioflim

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