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FUNMED > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Define ‘virulence’

A

Quality of being extremely poisonous, infectious or damaging OR the extent to which a disease or toxin possess this quality

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2
Q

Briefly describe gram negative bacteria

A

On staining appear red/pink; have an outer layer followed by thin peptidoglycan layer in the cell wall

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3
Q

Briefly describe gram positive bacteria

A

On staining appear violet/purple and have thick peptidoglycan cell wall

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4
Q

What are cocci bacteria?

A

Spherical appearance

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5
Q

What are bacilli bacteria?

A

Cylindrical rod appearance

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6
Q

What are spirochaetes bacteria?

A

Curved/spiral appearance

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7
Q

How can you distinguish between staphylococci and streptococci?

A

Staphylococci are catalase positive and streptococci are catalase negative

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8
Q

What is a virus?

A

Single cell with no organelles, has either a DNA or RNA strand (not both) and a protein capsid which surrounds and protects the genome

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9
Q

What are fungi?

A

Organism with mainly chitin cell wall, which have similar ultrastructure to eukaryotes but with 80S ribosomes

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10
Q

What are protozoa?

A

Unicellular eukaryotes (parasites) with 80s ribosomes

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11
Q

What are helminths?

A

Multicellular eukaryotes without a backbone or exoskeleton

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12
Q

What is a parasite?

A

Any living form which is dependent on other living things for survival and causing some damage to the host

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13
Q

Describe the structure of bacteria

A

Single circular chromosome is free in the cytoplasm (and sometimes plasmids), have 70s ribosomes, no mitochondria though or any membrane-based organelles

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14
Q

What is peptidoglycan?

A

A cross-linked complex of polysaccharides and peptides

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15
Q

What are pili?

A

Hair-like proteins which allow transfer of DNA between bacteria

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16
Q

What are fimbriae?

A

Hair-like proteins which interacts with cell surface receptors to allow binding

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17
Q

Describe the mechanisms by which bacteria adhere to the body

A

1) Stick to mucosa via Van der Waals at portal of entry
2) Proteins on microbe surface recognise host carbohydrates and bind OR pili/fimbriae attach
3) Surface molecules of microbe bind to complementary surface receptors on certain cells of the host tissue

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18
Q

What is a biofilm?

A

Accumulation of bacteria on a cell surface due to van der waals forces (begins as slime and proliferation forms biofilm)

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19
Q

What is viral antigenic shift?

A

Change in antigens on the surface of viruses to evade established immune responses

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20
Q

How do viruses harm the host?

A

Induce histological cell changes in certain areas (cause giant cells), cause cells to enter apoptosis, incorporate nucleic acid into genome which can cause cancers

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21
Q

What does catalase do?

A

Breaks down hydrogen peroxide to water and oxygen

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22
Q

What are exotoxins?

A

Toxins produced by gram negative and positive bacteria to help bacterial spread, lyse cells and block protein synthesis and cell function

23
Q

What are endotoxins?

A

Toxins produced only by gram negative bacteria and cause an over-reaction of the immune response leading to host cell damage

24
Q

How do bacteria persist in the human body despite immunological defences?

A

Bind the host antibody the wrong way –> antibody neutralisation, disrupt complement binding and produce antiphagocytic enzymes, detoxifies harmful substances such as free radicals and hydrogen peroxide and produces heat shock proteins to prevent denaturation at increased temperatures

25
Q

Outline the course of viral infection

A

primary replication –> systemic spread –> secondary replication in susceptible organs following spread

26
Q

Describe the different modes of virus transmission

A

Direct (horizontal) - host to host contact
Indirect (horizontal) - through food, water etc.
Transplacental (vertical)
Perinatal (vertical)
Breast milk (vertical)

27
Q

Define incidence

A

Occurrence, rate or frequency of a disease

28
Q

Define prevalence

A

The proportion of a population with the condition

29
Q

What is meant by ‘reproduction number (RO)’?

A

The number of transmissions per source of virus

30
Q

What is an antibiotic?

A

A natural antimicrobial substance produced by a microorganism

31
Q

What is an antimicrobial?

A

A type of antibiotic that is synthesised chemically, or modified from natural resources

32
Q

What are some bacterial targets for drugs?

A

Cell wall synthesis, bacterial protein synthesis, nucleic acid metabolism and bacterial cell membrane

33
Q

Describe and name two antimicrobials that affect the bacterial cell wall

A

Beta lactams - inhibit cell wall synthesis by binding to transpeptidases which cross-like in the cell wall,, leading to an unsupported cell –> cell ruptures –> bacterial death
Glycopeptides - inhibit cell wall synthesis in gram positive bacteria by binding to cell wall precursors

34
Q

Describe and name three antimicrobials that inhibit protein synthesis

A

Aminoglycerides - bind to 30s subunit of ribosome –> disrupts structure –> prevents translation initiation
Tetracyclines - bind 30s subunit (bacterial ribosome) –> prevents AA amino acid incorporation –> incomplete, non-functional proteins
Macrolides - bind to 50s subunit –> prevent translocation of protein along the ribosome

35
Q

Describe and name two antimicrobials that inhibit nucleic synthesis

A

Quinolones - inhibit DNA synthesis

Rifampicin - inhibits RNA polymerase

36
Q

Outline the infectious cycle of a virus

A

attachment and particle entry –> decoding and uncoating of genome –> translation of viral mRNA by host ribosomes –> genome replication –> assembly and release of particles containing genome

37
Q

What is a viral capsid?

A

Protein shell of a virus

38
Q

What are capsomeres?

A

One of the individual protein units which make up the capsil (outer coat)

39
Q

Define ‘genome’

A

Complete set of genes present in a cell or organism

40
Q

What is a nucleocapsid?

A

Capsid of a virus with the enclosed nucleic acid

41
Q

Describe the function of viron proteins

A

Assemble protective shell, bind to specific external receptors on host cells, transmit signals to induce genome uncoating, induces fusion with host cell membrane, transports genome to appropriate site within host cell

42
Q

What are RNA viruses?

A

Viruses containing RNA, if it has a positive polarity it can be transcribed immediately, if it has a negative polarity it has to be converted to positive before it can be translated

43
Q

What are antivirals?

A

Drugs which target viral proteins, predominantly viral enzymes

44
Q

Describe the influenza virus

A

Orthomyxocirus has an envelope, single stranded RNA, 8 segmented genes and surface spikes of haemagluttinin protein and neuraminidase

45
Q

What does antigenic shift and drift of the influenza A virus involve, and what can this cause?

A

Antigenic shift involves the shift in haemagluttinin and can lead to a pandemic
Antigenic drift involves changes to the virus due to host to host transmission (evolution) and this leads to epidemics and involves haemagluttinin and neuraminidase proteins

46
Q

Describe how amanitidine and rimantidine work to treat flu

A

Inhibits the viral M2 protein which decreases viral H+ influx and this inhibits viral uncoating and inhibits the coating process as a new viron aims to leave (by binding to haemagluttinin)

47
Q

Describe how neuraminidase inhibitors work to treat flu

A

Stops neuraminidase from cleaving sialic acid from glycoconjugate and therefore stops viron release, aggregation of virons and also increases virus inactivation conducted by respiratory mucus

48
Q

Describe the HIV virus

A

Single stranded RNA present, reverse transcriptase, integrasem protease

49
Q

Describe the treatment of HIV

A

HAART (highly active anti-retroviral therapy) where drugs include inhibitors of reverse transcriptase, integrase, protease and fusion and entry modalities

50
Q

Describe the hepatitis C virus

A

An enveloped virus with a single-strand of RNA

51
Q

What is an emergent virus?

A

When a virus has adapted and emerged as a new disease/strain

52
Q

What is a resurgent virus?

A

When a virus increases in prevalence one more after a period of little activity or occurrence

53
Q

Define ‘serotype’

A

The type of organism, determined by its constituent antigens

FUNMED (8 decks)

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