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Phase 2a Medicine > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What is a pathogen?

A

Organism that is capable of causing disease

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2
Q

What is a commensal organism?

A

An organism that colonises the host but causes no disease in normal cirumstances

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3
Q

What is an opportunistic pathogen?

A

Microbe that only causes disease if host defences are compromised

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4
Q

What is virulence/pathogenicity?

A

The degree to which a given organism is pathogenic

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5
Q

What is asymptomatic carriage?

A

When a pathogen is carried harmlessly at a tissue site where it causes no disease

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6
Q

What is general rule for naming bacteria?

A

Genus first then species second

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7
Q

What is the name for round bacteria?

A

Coccus

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8
Q

What is the name for rod shaped bacteria?

A

Bacillus

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9
Q

What colour do gram positive bacteria stain?

A

Purple (purple has 2 p’s)

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10
Q

What colour do gram negative bacteria stain?

A

Pink (pink has an n in it)

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11
Q

What is a diplococcus bacteria?

A

A bacterium that occurs as pairs of cocci

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12
Q

Apart from by themselves or in pairs, how else can coccus bacteria occur?

A

Chain of cocci and cluster of cocci

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13
Q

What ways can bacillus arrange themselves?

A

Individually, chains of rods, curved rods or spiral rods

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14
Q

What is the name for curved bacillus?

A

Vibrio

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15
Q

What is the name for spiral bacillus?

A

Spirochete

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16
Q

What is the main 2 differences between gram positive and gram negative bacteria?

A

Gram positive bacteria have a thick peptidoglycan layer and no outer lipid membrane. Gram negative bacteria have a thin peptidoglycan layer and have an outer lipid membrane.

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17
Q

What is the environment needed to kill bacteria?

A

50 years for spores) and UV light

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18
Q

How longs does the average bacteria take to double?

A

Less than an hour. E. coli doubles every 20-30 minutes, but some can take up to 2 weeks.

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19
Q

What is an endotoxin?

A

Lipopolysaccharides found in the cell wall of Gram-negative bacteria, which can induce inflammation and fever as an immune response in higher organisms

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20
Q

What is an exotoxin?

A

Group of soluble proteins that are secreted by the bacterium, enter host cells, and catalyse the covalent modification of a host cell component(s) to alter the host cell physiology

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21
Q

How is transcription in bacteria similar to transcription in eukaryotic cells?

A

Still uses RNA polymerase to create mRNA

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22
Q

Is bacteria division a stable or unstable process?

A

Very unstable, prone to mutations. These can be base substitution, deletion or insertion

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23
Q

Why does bacterial division instability make them hard to treat?

A

They are always changing

24
Q

What are plasmids?

A

Small, often circular DNA molecule found in bacteria and other cells

25
Q

Why are plasmids known as promiscuous?

A

They can be exchanged between cells

26
Q

What are some examples of what plasmids may contain?

A

Transfer promotion genes, plasmid maintenance genes, antibiotic or virulence determinant genes

27
Q

What are the gene transfer methods plasmids can be exchanged?

A

Transformation e.g. via plasmid, transduction e.g. via phage, conjugation e.g. via sex pilus

28
Q

What is the classification of bacteria?

A

Really complicated. Quite hard to do on flashcards, have a look at some images

29
Q

Why do gram positive bacteria stain purple?

A

The thick peptidoglycan layer cannot be easily penetrated by the solvent

30
Q

What is coagulase?

A

An enzyme produced by bacteria that clots blood plasma. Fibrin clot formation around bacteria may protect them from phagocytosis

31
Q

What are the bacterial classifications of bacteria?

A

Can be coagulase +ve or -ve

32
Q

What type of infections are coagulase -ve species important in?

A

Opportunistic infections

33
Q

What is the normal habitat for staphylococcus?

A

Nose and skin

34
Q

How is staphylococcus aureus spread?

A

Aerosol and touch

35
Q

What virulence factors do staphylococcus aureus have?

A

Pore forming toxins, proteases, toxic shock syndrome toxin and protein A

36
Q

What is MRSA resistant to?

A

Beta-lactams and many other antibiotics now

37
Q

What are the 2 types of infection caused by MRSA

A

Pyogenic (wound infections and abscesses (boils carbuncles)) and toxin mediated (scalded skin syndrome)

38
Q

What does S. epidermis cause?

A

Wound infections, boils, sinus infections, endocarditis and other inflammations. Commonly infections in debilitated prostheses

39
Q

What does S. saprophyticus cause?

A

Common cause of UTIs but also causes acute cystitis

40
Q

What is haemolysis?

A

Breakdown or destruction of red blood cells

41
Q

What is beta type haemolysis?

A

Complete lysis of red cells in the media around and under the colonies

42
Q

What causes beta haemolysis?

A

2 hemolysins O and S

43
Q

What is alpha haemolysis?

A

Reduction of the red blood cell haemoglobin to methaemoglobin in the medium surrounding the colony

44
Q

What causes alpha haemolysis?

A

Hydrogen peroxide produced by the bacterium. H2O2 reacts with Hb.

45
Q

What is a serogroup?

A

A group of serotypes having one or more antigens in common

46
Q

How can you test for Lancefield A-h and K-v serogroups?

A

Antiserum added to each group and added to the suspension of bacteria. Clumping indicates recognition

47
Q

What are the S. pyogenes virulence factors?

A

Exported factors, toxins and surface factors

48
Q

What are the infections caused by S. pyogenes?

A

Wound infections (cellulitis and puerperal fever), tonsillitis and pharyngitis, otitis media, impetigo, scarlet fever, complications (rheumatic fever)

49
Q

Where can S. pneumoniae exist normal commensally?

A

The oropharynx (30% of the population)

50
Q

What does S. pneumonia cause?

A

Pneumonia, otitis media, sinusitis and meningitis

51
Q

What are the predisposing factors that assist S. pneumonia?

A

Impaired mucus trapping (e.g. viral infection), hypogammaglobulinemia and asplenia

52
Q

What are the virulence factors of S. pneumonia?

A

Capsule, inflammatory wall constituents and cytotoxin

53
Q

Why do gram negative bacteria stain pink?

A

The thinner peptidoglycan layer allows the stain to wash out by the solvent

54
Q

What is lipopolysaccharide?

A

Major component of the wall of gram negative bacteria. Can also be classed as an endotoxin

55
Q

What are pathogenicity determinants (virulence determinant or virulence factors)?

A

Any bacteria-associated product or strategy that contributes to pathogenicity/virulence

56
Q

What are the colonisation factors?

A

Adhesions, invasins, nutrient acquisition and defence against the host

Phase 2a Medicine (6 decks)

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