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Human Biosciences > Medical and general microbiology > Flashcards

Medical and general microbiology Flashcards

1
Q

Disease definition

A

conditions that impair normal tissue function

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2
Q

What is Cystic fibrosis?

A

is due to a specific genotype that results in impaired transport of chloride ions across cell membranes – genetic or metabolic disease

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3
Q

What’s Atherosclerosis?

A

disease of aging, because it typically becomes a problem later in life after plaques of cholesterol have built up and partially blocked arteries

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4
Q

What’s measles?

A

infectious disease because it occurs when an individual contracts an outside agent

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5
Q

What’s an infection?

A

when a pathogen invades and begins growing within a host.

Disease results only if and when, as a consequence of the invasion and growth of a pathogen, tissue function is impaired.

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6
Q

What is a true pathogen and a opportunistic pathogen?

A

A true pathogen is an infectious agent that causes disease in virtually any susceptible host.

Opportunistic pathogens are potentially infectious agents that rarely cause disease in individuals with healthy immune system, lots of people don’t believe in them

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7
Q

What’s Pathogenicity

A

the capacity of a microbe to cause damage in a (susceptible) host.

So its a discontinuous variable

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8
Q

Interactions between microbes and hosts?

A

commensalism - an association between two organisms in which one benefits and the other derives neither benefit nor harm

colonisation

latency - Of an infection, a period in which the infection is present in the host without producing overt symptoms.

disease.

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9
Q

What counts as damage from a pathogen?

A

Tissue Pathology

Loss of organ function

Growth in normally sterile sites

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10
Q

What’s virulence?

A

is one of a number of possible outcomes of host-microbe interaction.

Virulence is a continuous variable, that is, it is defined by the amount of damage or disease that is manifest

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11
Q

How is virulence is measured?

A

See what dosage produces an ID50 (when 50% of the population is infected) or LD (When 50% of population is killed)

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12
Q

What is a virulence factor (Kochs molecular postulates)?

A

Easy definition is a microbial trait which causes disease

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13
Q

What’s the Limitations of the virulence factor concept?

A

The view that pathogenicity is conferred by virulence factors is difficult to apply to many microbes whose pathogenicity is limited mostly to immunocompromised hosts,

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14
Q

How can bacteria hide themselves?

A

Form a biofilm which protects them from the immune system

Also allows them to replicate

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15
Q

What could influence virulence and pathogenicity?

A 
Microbiome
Inoculum
Sex
Temperature
Environment
Age
Chance
History
Immunity
Nutrition
Genetics

Misteaching

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16
Q

Gnotobiotic means?

A

microbe free

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17
Q

What are microbiota?

A

The microorganisms that typically inhabit a specific environment

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18
Q

What is the microbiome?

A

The totality of microbes, their genomes and environmental interactions in a defined environment. e.g. the gut of a human, soil sample

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19
Q

What is dysbiosis?

A

Microbial imbalance on or within the body

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20
Q

How many more microbial genes are there compared to ours?

A

100 times more

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21
Q

2 phyla that dominate fecal matter?

A

Firmicutes and Bacteroidetes

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22
Q

What do microbes do?

A

Involved in immune system regulation
remove toxins and carcinogens,
crowd out pathogens (colonisation resistance),
improve intestinal functions,
gut-brain links in communication,
as important to us as a liver- because of metabolites produced in gut.

Considered as a vital organ

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23
Q

Feature of silver?

A

Its an antimicrobial

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24
Q

How does Naturally microbial succession occur?

A

from birth to later years (critical inoculation in infancy/birth).

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25
Q

Features of microbes and external organs?

A

, surface tissues (skin & mucous membranes and gut) are constantly exposed to environmental microorganisms and are readily colonized by diverse microbial (primarily bacterial) species

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26
Q

Whats the human microbiome project?

A

Highly parallel DNA sequencers combined with high-throughput mass spectrometers enable characterization of whole microbial communities

including Genomes, proteins and metabolic products

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27
Q

What were the aims of the human microbiome project?

A

Determine whether individuals share a core human microbiome

Can changes in the human microbiome be correlated with changes in human health?

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28
Q

What Significant advances were required in order to fully analyze the microbiome
?

A

Improved culture methods

Perform genome sequencing in the absence of culture

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29
Q

Features of the normal healthy human microbiota?

A

There is the core part which majority of all humans have this set of genes

Then there is a variable area which smaller subsets of humans have these genes

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30
Q

What’s The most heavily colonized organ in the human body?

A

The GI tract, contains more than 70% of microbes in the body

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31
Q

Overview of gut microbiota?

A

Strict anaerobes outnumber facultative aerobes & aerobes

Gut microbiota is dominated by just two phyla
Bacteroidetes (e.g. Bacteroides)
Firmicutes (e.g. Clostridium)

Bacterial abundance increases as we progress from the stomach to the colon

Colonization begins at birth, during passage through birth canal

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32
Q

What does endogenous mean?

A

All over us

eg. Staphylococcus aureus

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33
Q

What does exogenous?

A

Get from the exterior environment

eg.Clostridium spp.

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34
Q

Main cause of infection in hospitals?

A

When the skin is broken

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35
Q

Gram negative bacteria pathogen?

A

Pink on gram stain

Thin layer of peptidoglycan doesn’t trap crystal violet so it goes pink

Have 2 phospholipid bi layers the cytoplasmic membrane (phospholipid) and the outer membrane (carbohydrate) the sandwich the peptidoglycan layer

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36
Q

Features of Neisseria meningitides?

A

It’s a beta Proteobacteria

Gram negative

Carriage in the nasopharynx in 10-15% of the population

Epidemics occur every 10-12 years

Meningitidis belt in Africa where rates of infection can be 1 in 100

Classified by serogroup – reactivity to a bacterial polysaccharide capsule

Can turn their capsule on and off

There are 12 serogroups, 6 of which can cause epidemics

Carriage is facilitated by downregulation or loss of capsule expression, as this sterically inhibits adherence and biofilm formation.
However, survival in the bloodstream and in epithelial cells is enhanced by capsule expression

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37
Q

Why was meningitis B unable to have an effective vaccine produced for it?

A

The carbohydrate capsule was too similar to our carbohydrates on our cells

They fixed it by not basing vaccine on capsule rather a surface lipoprotein on it

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38
Q

Features of Gram positive bacteria?

A

Example is Corynebacterium diphteriae

Gram positive, immotile rod
Colonises upper respiratory tract

Route of infection: Airborne droplet

Produces exotoxin
Kills surrounding host cells

Toxin spreads systemically
Principally affects: Heart and Lungs
Main cause of mortality

Classic AB toxin - the main virulence factor (B is the binding factor)

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39
Q

What are emerging infections?

A

infections that are rapidly increasing in incidence and/or geographic range

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40
Q

The process of disease emergence can be divided into two steps?

A

Introduction

Establishment and dissemination

41
Q

What are zoonotic diseases?

A

Capable infecting animal hosts other than humans

They tend to show no disease on their natural host but transferring to a different species will cause disease

Example is Streptococcus suis infects pigs then humans,

42
Q

Course assessment includes up to 15th October lecture and also includes the practicals

A

ok

43
Q

What causes IBD?

A

Intestinal microbiota and genetics

44
Q

Is there a link between obesity and intestinal microbiota?

A

Yes

45
Q

What is H. pylori?

A

first formally recognized bacterial carcinogen

ability to induce gastritis, peptic ulcers, gastric cancer and mucosa-associated lymphoid tissue lymphoma has been confirmed.

Susceptibility is multifactorial e.g. H. pylori virulence, environmental factors, genetic susceptibility of the host and status of host immune system.

Difficult to eradiciate

Gastric carcinoma development may be a result of host genetic, environmental and microbiological factors.

46
Q

What’s Nod2?

A

intracellular sensor for bacterial peptidoglycan. 3 polymorphisms in nod2 associated with Chroms Disease, each polymorphism results in reduced activation of NF-kB (protein complex that controls transcription of DNA, cytokine production and cell survival) in response to bacterial peptidoglycan

Nod2 function is required for optimal defensin expression –very important antimicrobial peptides = a critical component of the innate immune system.

47
Q

What’s Faecalibacterium?

A

Anti-inflammatory commensal bacterium identified by gut microbiota analysis of chronic disease patients

48
Q

Obesity-related shift in human microbiota?

A

A shift in the relative abundance of Bacteroidetes and Firmicutes has been observed in obese humans

Furthermore, abundance of Bacteroidetes increased when dieting, with the change in abundance correlating with weight lost

49
Q

What are the requirements for disease?

A

Portals of entry

Establishment

Avoiding host defences

Damaging the host

50
Q

How do we protect portals of entry?

A

Washing them with secretions eg. tears

Filter hairs in nasal passages prevents entry of large particles

Cillia in respiratory tract push mucous and microbes upwards

Keratinised surface of skin - tough so acts as an effective barrier against entry

51
Q

Features of mucous membranes?

A

Form a protective covering that resists penetration and traps many mircrobes

Are often bathed in antimicrobial secretions which contain a variety of antimicrobial substances

Contain mucosal associated lymphoid tissue

52
Q

Reasons why fluids such as blood are not suitable for microbial growth?

A

Iron isn’t available in blood or breast milk

Long chains of fatty acids which are lethal to bacteria found on skin

Lactenin- proteins in breast milk are anti bacterial and protect against inflammation

53
Q

What is lysozyme?

A

Found in tears and saliva

Hydrolyses bond connecting sugars in peptidoglycan

Affects gram positive bacteria

54
Q

Features of the GI tract that wipe out gram negative bacteria?

A

Gastic acid in stomach

Paneth cells, Pancreatic enzymes, bile, intestinal enzymes, GALT, and peristalsis from the intestines

Intestines also produce lysozyme and cryptins

55
Q

Features of the genitourinary tract?

A

Low pH of urine and vaginal epithelia
Urea and other toxic metabolic end products in urine
Hypertonic nature of kidney medulla
Flushing with urine and mucus

56
Q

What are defensins?

A

Peptides that are open ended, rich in arginine and cysteine and disulphide linked.

Found in neutrophils, intestinal panteth cells and intestinal and respiratory epithelial cells

They defend from pathogens

Shape microbiota

Protect stem cells

57
Q

What are bacteriocins?

A

Peptides produced by bacteria which are lethal to close related species

58
Q

How do bacteria establish themselves?

A

Have adherence factors

Normally multi factorial

59
Q

Examples of secreted enzyme defences?

A

Leukocidins - Kill white blood cells including neutrophils and macrophages
Produced by Stapylococcal and Streptococcal spp

Coagulase - Causes fibrin clots to form in the blood of a host. Advantageous to the bacteria in evasion

60
Q

Example of damaging chemicals bacteria release? (Exotoxins)

A

Neourotoxins - cause paralysis

Enterotxins - cause sickness and diarrhoea

Cytotoxins - cause cell death

61
Q

Bacterial anatomy of the bacterial cell wall?

A

Gram positive:
Thick layer of peptidoglycan on outside, has associated proteins as well as lipoteichoic and wall teichoic acid

Plasma membrane inside, has integral and peripheral proteins

Gram negative:
Outer membrane is made up of lipopolysaccharides, has porin gaps and a periplasmic gap between it and the middle peptidoglycan wall and has lipoproteins connecting them

Then inside is the plasma membrane

62
Q

Stuctures outside the bacterial cell wall?

A

Glycocalyx - polysaccharides and proteins. If loosely attached referred to as slime layer. If they from a highly organised structure more commonly known as capsule. Common in preventing phagocytosis and allowing infection to continue

Fimbriae an pili are involved in adherence and mostly found in gram negative bacteria, aid motility in gliding or twitching motility. Potential vaccine candidates. Used in immune evasion through a process of antigenic variation

Flagella and Axial filaments-
Aids in movement to distal tissues
Use flagella to penetrate through gastric mucous

63
Q

Bacterial anatomy inside the cell wall?

A

Plasma membrane - Target for therapeutic strategies

DNA - Spread of antibiotic resistance on plasmids Target of antibiotic therapy.

Ribosomes - Target for antibiotics

64
Q

Historical workflow for determining an infection?

A

Stain based metrologies

Microbial culture the bug

Biochemical or antigenic techniques

Antimicrobial susceptibility testing (which one will be effective)

65
Q

need to know steps of a gram stain

A

ok

66
Q

Stains for microscopy?

A

Gram

Ziegl-neelson stain - specific, no need for culture, used mainly for tb, performed directly on sputum

PAS (periodic acid-Schiff) - stain for glycoproteins often used for fungi. disadvantage is stains for hosts cells as well

67
Q

medias in a microbial culture?

A

Selective media- eg mannitol salt agar prevents gram negatives growing, it’s specific for staphylococci

Differential media - MacConkey used to select for gram negative

68
Q

What are API strips?

A

20 biochemical tests done simultaneously

69
Q

What are agglutination assays?

A

Don’t require cultures
Used frequently for detection of viral infections

create beads with antigen for a virus

take some blood if antibody is present from virus the beads will bind and form clumps which we can see

70
Q

Describe agglutination assay using red blood cells?

A

Have red blood cells and add virus bug

Haemoglutination occurs so they bind to each other form a clump

Then add serum from someone who has infection you think it is, the antibodies will bind to the virus and haemoglutination won’t occur anymore with the red blood cells

71
Q

Describe ELISA - (Enzyme Linked ImmunoSorbent Assay)

A

good because very sensitive

Direct - have a primary antibody conjugate attached to an enzyme which will bind to the substrate

Indirect - the same as direct but also have a secondary antibody conjugate, increases specificity, also wash so on indicator doesn’t give positive to anything else

Capture assay - the same as indirect but also have an initial capture assay

72
Q

How to determine antibiotic resistance?

A

Use Etest strips, Antibiotic present at a gradient of concentrations on a Petri dish

73
Q

Types of modern clinical microbiology techniques?

A

Next generation sequencing
PCR
Mass spectrometry

74
Q

Types of total cell count?

A

Shows both living and dead cells

Direct microscopic count - difficult due to size of cells

Turbidity - measured using a calorimeter where the culture absorbance is proportional to the cell numbers and cell weight

Dry weight - involves analysis involves drying the cell mass after centrifuging a bacterial culture, the cell mass dried at 100 degrees is about 20-30% less than the wet weight

Chemical estimates - involves measuring the amount of ATP or protein to estimate the total amount of cells

75
Q

The dry weight of prokaryotic cells ranges from?

A

10 ^-15 g to 10 ^-11 g

76
Q

What are viable cell counts?

A

Measured through plate or colony count, based on the assumption that one bacteria cell produces one CFU

The culture is diluted several times and either spread onto agar plates or incorporated into molten agar and poured into plates

CFU’s that grow on agar can now be used to calculate bacteria per ml

The miles and Misra method uses smaller drops (10ul) of each dilution so more can be plated on one plate

77
Q

Questions to ask in next lab?

A

Is measuring biomass and turbidity a good quantitive measurement enumerating bacteria in the probiotic sample?

For what other purposes would you make sequential measurements of optical density of a cell suspension at 600nm

How come there was a difference between bio mass and turbidity with the amount of CFU

78
Q

CFU that are viable to count?

A

30-300

79
Q

Why do we measure cell number at 600nm? and what wavelength is used to measure protein or DNA

A

Any more UV light would start killing bacteria

260nm DNA

280nm protein

80
Q

Bacteria involved in the fermentation of milk?

A

Lactobacillus bulgaricus

Lactococcus lactis

Streptococcus thermophilus

81
Q

Most commonly added culture after sterilisation in yoghurt is?

A

L.caseli, member of the genus Lactobacillus

82
Q

How to work out CFU from a serial dilution?

A

Multiply the amount you counted so you have the correct amount fluid in your formula

Then multiply by the correct power of 10

83
Q

In an isolated colony are all the bacteria genetically identical?

A

yes

84
Q

Forms of bacteria going from circle shaped to very chain like?

A

Circular
Irregular
Filamentous
Rhizoid

Can
I
f
R

85
Q

Different types of elevation of bacteria?

A 
Raised - small dome
Convex - higher dome
Flat
Umbonate - nipple
Crateriform 0 crater
Rick
Clapped
Feebly
Under
Caren
86
Q

Different types of margin?

A 
Entire
Undulate - few bobbles
Filiform - thin hairs
Curled - dart board
Lobate -few thick hairs

Eat udders for cuban leprocorns

87
Q

What causes filamentous appearance?

A

When bacteria have flagella and swarm across the plate

88
Q

What appearance do bacteria that produce capsules or expolysaccharides show?

A

Mucoid or glossy appearance

Mostly are circular or raised

89
Q

Bacteria that have a dry rough appearance are sometimes referred to as?

A

Ground glass appearance

90
Q

Steps of gram stain?

A

Fix bacteria passing through flame

Crystal violet

Iodine

Alcohol

Counter stain with safranin

Observe under immersion oil 100 x

positive = purple

negative = pink

91
Q

How to test for biochemical activities of a microbial isolate?

A

Testing the fermentation of different sugars

Members of the lactic acid bacteria when they ferment sugars they produce lactic acid so the pH goes down, hence lowering the pH

Can test this with the indicator bromocresol purple

Yellow media occurs when the pH is bellow 5.2
Purple when it’s more than 6.8

92
Q

What type of antibiotic is Ampicillin?

A

B-Lactam

93
Q

What type of antibiotic is kanamycin?

A

Aminoglycoside

94
Q

neomycin phosphotransferase ii gene encodes to resistance for what antibiotic?

A

confers resistance to various aminoglycoside antibiotics, including kanamycin

95
Q

What does B-lactamase gene (bla) do?

A

Encodes for an enzyme that confers resistance to B-lactam antibiotics

Does this by catalysing the hydrolysis of a broad range of β-lactam

96
Q

What is MIC?

A

The minimum inhibitory concentration

97
Q

The abundance of Faecalibacterium within the gastrointestinal tract is believed to influence Crohn’s disease because?

A

Faecalibacterium promotes the production of anti-inflammatory cytokines

98
Q

Describe restriction endonucleases?

A

Cut DNA at specific target sequences

Their mode of action is DNA sequence dependent

Widely used in genotyping to identify genetic differences between bacterial strains without the need for sequencing

Techniques that use them include Pulsed-field gel electrophoresis (PFGE) and Single nucleotide polymorphism (SNP)

To look at plasmid DNA sequences use restriction fragment length polymorphism (RFLP)

99
Q

Describe RFLP?

A

Used on 2 different strains

Method based on the principle that the plasmid circular DNA will be linearised if cut at a single location and will be cut into fragments if cut twice

The difference in length (length polymorphism) of the restriction fragments will be seen after gel electrophoresis and will indicate which plasmid has been isolated

Identification is done via a plasmid map which shows where the restriction enzymes recognition sites are located on the circular molecule and allows you to identify the plasmid

eg. which has the black (ampicillin) resistant plasmid and which has (Neo) kanamycin resistant

Human Biosciences (69 decks)

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