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EK Phase 2A > Microbiology Practicals > Flashcards

Microbiology Practicals Flashcards

1
Q

How is a gram stain prepared?

A

Come In And Stain
Crystal violet - primary stain
Iodine
Acetate/Alcohol - decolourise
Safranin - Counterstain

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2
Q

What colour do gram positive and gram negative bacteria stain?

A

Gram positive - Purple

Gram Negative - Pink

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3
Q

What is blood agar?

A

agar with horse/sheeps blood
used for growing lots of bacteria
least selective

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4
Q

What is chocolate agar?

A

heated to 80C for breakdown of haem & release of factors that grow organisms w/ fastidious growth requirements [H.influenzae]

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5
Q

What is CLED?

A

differentiates between organisms in urine & allows classification of lactose fermenting & non lactose fermenting gram-negative bacilli

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6
Q

What is MacConkey Agar?

A

grows gram negative bacilli (it has bile salts that inhibit the growth of gram positive). Has lactose & red dye

lactose fermenting = pink colonies
non lactose fermenting = white colonies

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7
Q

What is Gonococcus Agar?

A

Contains growth factors to promote the growth of Neisseria species as well as antibiotics & antifungal agents to inhibit the growth of other organisms.

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8
Q

What is Sabouraud’s Agar?

A

used to culture fungi. Has antibiotics to inhibit bacterial growth.

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9
Q

What is XLD Agar?

A

used to isolate Salmonella and Shigella [non lactose fermenting, gram negative]
Salmonella - Red with black centre (produces H2S)
Shigella - Red only

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10
Q

What colour will Staphylococcus aureus appear on blood agar and what colour would other staphylococcus species appear?

A

S.aureus - gold
S.other - white

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11
Q

What are the sterile sites of the body?

A

Blood
CSF
pleural fluid
Peritoneum
Joints
Urinary Tracts
Lower Respiratory Tract

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12
Q

How can you tell the difference between various Gram Positive bacteria?

A

+tve Catalase Test = Staphylococcus:
(if positive then do Coagulase Test:)
+tve = S.aureus
-tve = S.epidermidis/S.saprophyticus

-tve Catalase Test = Streptococcus
(if negative then do Haemolysis on blood agar)

alpha haemolysis (partial/green) = requirement for Optochin Test
Optochin Sensitive = S.pneumoniae
Optochin Resistant = S. viridans group

Beta haemolysis (full) = requirement for Lancefield grouping via serology)
A = S.pyogenes
B = S.agalactiae
A,C, G = Tonsilitis, pharyngitis, skin infection
B = Neonatal sepsis + meningitis

Gamma Haeomolgysis (none) = Enterococcus

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13
Q

How can you tell the difference between various Gram Negative bacteria?

A

MacConkey Agar for lactose fermentation Test:
+tve lactose fermentation = E.coli/Klebsiella
-tve Lactose fermentation = Requirement to do Oxidase Test

Oxidase Test:
+tve Oxidase = Pseudomonas, Aueruginosa
-tve Oxidase = Requirement to do XLD test:

Colonies on XLD which are Red with black centers = Salmonella
Colonies on XLD which are Red only = Shigella

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14
Q

What are the 2 main approaches to diagnosing viral infection?

A

Electron Microscopy / PCR
Serology Testing - ELISA, IF, Complement Fixation Test.

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15
Q

What is an advantage and disadvantage to EM testing?

A

Very specific and sensitive but too expensive and too long

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16
Q

What is an advantage and disadvantage to PCR?

A

Very fast but high risk of false positives as it is very sensitive and so can easily be contaminated.

17
Q

What virus causes shingles and how does it present?

A

Varicella Zoster Virus (VZV)

Red painful rash conferred to a single dermatome

18
Q

What virus causes Glandular fever (infectious mononucleosis)?

A

Epstein Barr Virus (EBV)

Ix: FBC - Atupical lymphocytes
Serology for EBV Igs - ELISA Test

19
Q

What is a differential Diagnosis to Glandular fever and how is this ruled out?

A

S.pyogenes throat infection - Both EBV and S.pyogenes present with purulent (pus) infection over the tonsils

Take black charcoal swab to rule out S.pyogenes

20
Q

What other Sx can be caused by EBV?

A

Tonsilitis,
Cough
Fever
Splenomegaly

21
Q

What is BALF?

A

Bronchoalveolar lavage fluid

Fluid collected from the lungs
Bronchi are washed and this fluid is sent for analysis using PCR

22
Q

What condition can cytomegalovirus cause?

A

CMV colitis
Characteristic finding is OWL EYE INCLUSION BODIES

23
Q

What is the treatment for CMV infection?

A

IV ganciclovir

24
Q

What HIV markers can be found in the blood

A

HIV Igs
HIV RNA
p24 antigen

25
Q

How may a patient present with meningitis?

A

Headache
Fever
Photophobia
Neck stiffness

26
Q

What Ix are required for suspected meningitis?

A

Take CSF sample.
CSF –> Increased WCC + protein

Determine type of meningitis based on CSF glucose, type of WCC and CSF appearance.
If viral then use PCR to determine specific type

EK Phase 2A (15 decks)

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