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Phase 2a > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Process of gram staining

A

Come in and stain

1) Stain the slide with CRYSTAL violet then rinse with water

2) Stain it with IODINE

3) Wash the slide with ACETATE (Gram + is purple, Gram - is colourless)

4) Use SAFRANIN COUNTERSTAIN - (Gram + is purple, Gram - is pink)

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2
Q

Differences in structure between gram positive and negative bacteria

A

Positive - Thick peptidoglycan layer (traps crystal violet-iodine complex)
Negative - Thin peptidoglycan layer

Positive - Lack an outer membrane (Reason why they are more susceptible to beta lactam antibiotics)
Negative - Has an outer membrane composed of lipopolysaccharides - An Endotoxin (not permeable to crystal violet-iodine complex)

Positive - Has lipoteichoic acid which provides structural support
Negative - doesn’t have

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3
Q

How to investigate specifically for
- Fungi
- Cryptococcus
- Syphilis

A

Fungi - Potassium hydroxide test

Cryptococcus - India ink stain

Syphilis - Dark ground microscopy

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4
Q

3 methods of genetic variation in bacteria/gene transfer

A

1) Transformation via uptake of free DNA from the environment

2) Transduction via phage - (virus transfers DNA from one bacteria to another)

3) Conjugation via sex pilus (genetic material transferred via direct contact)

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5
Q

What stain do you use for mycobacteria and why?

A

Ziehl Neelsen stain

Because their cell wall has a high lipid content with mycolic acids, making them resistant to gram stains

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6
Q

2 challenges in dealing with mycobacteria

A

1) Thick lipid rich cell wall with mycolic acids - difficult for immune cells to effectively kill it

2) They have a slow growth rate - symptoms develop over time leading to delayed diagnosis

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7
Q

Blood agar

A

Contains Sheep or horse blood

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8
Q

Chocolate agar

A

Contains blood agar that is heated (to release some nutrients) - easier for fastidious organisms to grow

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9
Q

Cled Agar - Cysteine lactose electrolyte deficient

A

Differentiates micro-organisms in urine

Lactose fermenting bacteria (E.coli) – Yellow

Non lactose fermenting bacteria (Salmonella, Shigella) - Blue

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10
Q

MacConkey

A

Primary grows gram negative bacilli
- Differentiates between lactose fermenting and non lactose fermenting

Lactose fermenting (E.coli) - Pink

Non lactose fermenting (Salmonella, shigella) - Yellow/colourless

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11
Q

XLD agar - Xylose lysine deoxycholate

A

Used to differentiate salmonella and shigella species.

Shigella - Red colonies
Salmonella - Red with black centres (salmonella reduces thiosulphate to hydrogen sulphide)

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12
Q

Sabouraud agar

A

Cultures fungi

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13
Q

CCDA agar - Charcoal cefoperazone deoxycholate agar

A

Selective and supports growth of Campylobacter

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14
Q

Lowenstein Jensen medium

A

For mycobacterium species e.g. M.tuberculosis

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15
Q

5 sterile sites of the body

A

Blood, CSF, pleural fluid, joints, urinary tract, lower respiratory tract

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16
Q

Definition of virus and virion

A

Virus - infectious, obligate intracellular parasite which comprises genetic material surrounded by a protein coat

Virion - The infectious particle of a virus which exists outside host cells.

17
Q

Malaria life cycle. Most common parasite

A

In the african continent - most common is plasmodium falciparum

(outside africa - mostly Plasmodium Vivax)

Gaemtocytes –> Sporozoites –> Schizont –> merozoites –> Schizont –> trophozoites

18
Q

What is the minimum inhibitory concentration of an antibiotic defined as?

A

The lowest concentration of an antibiotic required to inhibit visible growth of a microorganism after overnight incubation.

19
Q

5 functional groups of antibiotics

A

1) Beta-lactams (inhibits cell wall synthesis)

2) Polymyxins - inhibits mmbrane function

3) Quinolones - Inhibits nucleic acid synthesis

4) Anti metabolites - inhibits folic acid synthesis

5) Macrolides and tetracyclines - inhibits protein synthesis - inhibits 50s and 30s ribosomal subunits.

20
Q

Streptococcus viridans treatment

Strep pyogenes treatment

A

Benzylpenicillin

Strep pyogenes - phenoxymethylpenicillin

21
Q

Bacteria with no cell wall

A
  • Mycoplasma pneumoniae
  • Mollicutes
22
Q

Gram negative Cocci examples

A

Aerobic
Neisseria meningitidis
Neisseria gonorrhoea

Anaerobic
Veillonella

23
Q

Gram positive Rods/bacillus examples

A

Anaerobic
Clostridium.difficile

Aerobic
- Listeria monocytogenes
- Bacillus anthracis
- Corynebacterium diphtheriae

24
Q

Gram negative rods

A

Escherichia Coli
Salmonella
Shigella
Pseudomonas. aeruginosa
Campylobacter.jejuni
Haemophilus. influenzae

Anaerobic - Bacteroides.fragilis

25
Q

Anaerobic gram positive cocci

A

Peptostreptococcus

26
Q

Facultative anaerobe

A

Any organism that is able to grow either with or without free oxygen

  • E.coli
  • Listeria
  • Shigella
  • Salmonella
  • Staphylococcus species
27
Q

Pros and cons of PCR

A

Pros of PCR - Fast and sensitive
Cons of PCR - Need to suspect a virus before being able to test for it as you need complimentary primers to be designed + it is vulnerable to contamination and can yield a false positive result

28
Q

What receptor does Covid enter the body by?

Where are they expressed

A

Angiotensin converting enzyme 2 receptors

ACE2 - highly expressed in the lungs, hearts

29
Q

2 proteins in H.influenza

A

Haemagglutinin - lets the virus IN

Neuraminidase - Facilitates virus release from infected cells

30
Q

Glandular fever triad of symptoms and what its caused by

A

Cough, fever, splenomegaly, cervical lymphadenopathy (hallmark)

caused by EBV (young adults 15-24)

31
Q

Treatment of malaria and investigations

A

Investigations - Blood film showing parasites

Treatment - artemether-lumefantrine
(Quinine + doxycycline)

Prophylaxis - mosquito nets, mosquito spray

32
Q

What are the 2 possible ways that all antibiotics try to get rid of the bacteria?

A

1) Bactericidal antibiotics
- The agent kills the bacteria by inhibiting cell wall synthesis (by reducing peptidoglycan synthesis or by reducing cross linking of peptidoglycan) - Beta lactams, glycopeptide (vancomycin)

2) Bacteriostatic antibiotics
- Which inhibits the growth of bacteria. This is via the inhibition of protein synthesis, DNA replication or metabolism. - Clindamycin
(Defined as a ratio of minimum bactericidal)

Phase 2a (29 decks)

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