microbiology quiz 2

7/27/2019 microbiology quiz 2

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Quiz 2

Dr. Ashish Jawarkar

M.D. Path

Parul Sevashram Hospital


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Q-1

Which class of organisms causes the

disease in picture


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Athletes foot


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A. Bacteria

B. Fungi

C. Virus

D. Protozoa


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Fungi

Eukaryotic organisms

with rigid cell wall

Yeasts

Single-celled Reproduce by budding

Molds

Large, fuzzy,

multicelled organisms

Produce spores

Superficial infections

Athletes foot

Ringworm

Thrush

Can cause systemic

infections


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Q-2

Which of the following is semipermeable

A. cell membrane

B. cell wall

C. Nucleus

D. Ribosomes


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Cytoplasmic (Plasma)

membrane Thin layer 5-10 nm, separates cell wall from cytoplasm

Acts as a semipermeablemembrane: controls theinflow and outflow of metabolites

Composed of lipoproteins with small amounts of

carbohydrates


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Q-3

What are the contents of Mac Conkeys

medium?

A. Peptone B. Lactose

C. Neutral Red

D. All of the above


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Differential media

A media which has substances incorporated in it

enabling it to distinguish between bacteria. Eg: Mac Conkeys medium

Peptone

Lactose

Agar

Neutral red

Taurocholate

Distinguish between lactose fermenters & nonlactose fermenters.


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Lactose fermentersPinkcolonies

Non lactose fermenterscolourless colonies


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Q-4

What is this used for?


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For removing oxygen, to grow anaerobic

bacteria


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ANAEROBIC CULTURE METHODS

Anaerobic bacteria differ in their requirement

and sensitivity to oxygen.

Cl.tetani is a strict anaerobegrows at an

oxygen tension < 2 mm Hg.

Methods: Production of vacuum

Displacement of oxygen with other gases

Chemical method Biological method

Reduction of medium


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Production of vacuum:

Incubate the cultures in a vacuum desiccator.

Displacement of oxygen with other gases

Displacement of oxygen with hydrogen,

nitrogen, helium or CO2. Eg: Candle jar


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Chemical method

Alkaline pyrogallol absorbs oxygen.

McI ntoshFildes anaerobic jar

Consists of a metal jar or glass jar with a metallid which can be clamped air tight.

The lid has 2 tubesgas inlet and gas outlet

The lid has two terminalsconnected toelectrical supply.

Under the lidsmall grooved porcelain spool,wrapped with a layer of palladinised asbestos.


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Working:

Inoculated plates are placed inside the jar and

the lid clamped air tight. The outlet tube is connected to a vacuum pump

and the air inside is evacuated.

The outlet tap is then closed and the inlet tube is

connected to a hydrogen supply.

After the jar is filled with hydrogen, the electric

terminals are connected to a current supply, so

that the palladinised asbestos is heated.Act as a catalyst for the combination of hydrogen

with residual oxygen.


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Gaspak

Commercially available disposable envelope.

Contains chemicals which generate H2and CO2on addition of water.

Cold catalystin the envelope

Indicator is usedreduced methylene blue. Colourlessanaerobically

Blue colouron exposure to oxygen


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Q-5

What is resolution

A. the ability of the microscope to

enlarge the object B. the ability of the microscope to show

two nearby placed objects separately


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Important Vocabulary :

magnification \mag-ne-fe-'ka-shen\ n1.

apparent enlargement of an object 2. theratio of image size to actual sizeA magnification of "100x" means that theimage is 100 timesbigger than the actualobject.

resolution \rez-e-loo-shen\ n1. clarity,sharpness 2. the ability of a microscope toshow two very close points separately


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Q-6

Which type of microscope has been

used for taking this picture?


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A. Bright field microscope

B. Dark field microscope

C. Phase contrast microscopeD. Fluorosence microscope


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Bright-field MicroscopeContains two lens systems for magnifying

specimens

Specimens illuminated directly from above or

belowAdvantages: convenient, relatively

inexpensive, available

Disadvantages: R.P 0.2 m at best; canrecognize cells but not fine details

Needs contrast. Easiest way to view cells is

to fix and stain.


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Different magnifications


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Special Microscopy

Applications

Dark Field

Phase Con trast

Fluorescence

Electron Microscope


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Dark Field Microscopy

special condenserdiaphragm

occludes direct light,passes wide anglelight

angle too wide toenter objective

diffractedlight

diffracted light scattered

enters objectiveobjects light on dark background


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Phase Contrast Microscopy

light rays through objects of different change in

phase, not intensity

special ring-shaped condenser diaphragm

special glass disc in objective

change phase differences to intensity differences

can view transparent

objects as dark on light

background (without staining)

Right; human brain glial

cells


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Fluorescence Microscopy

Illuminate specimen with UV visible fluorescence(filter removes harmful UV)

View auto-fluorescent objects (e.g., chloroplasts)

Stain with specific fluorescent dyes, which absorb in

region 230-350 nm & emit orange, yellow or greenishlight

Images appear coloured against a dark background


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Electron Microscopy


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Q-7

Steps of staining include

1. primary stain

2. decolorisation 3. counter stain

Which dyes are used for these steps?In gram staining and acid fast staining


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Primary

staining

Decolorisation

Counter

staining


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Primary stain

Decolorisation

Counter stain


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Q-8

What is sterilisation?

A. Killing all organisms on the object

B. Removing only pathogenic organisms


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DEFINITION

STERILIZATION

The process of freeing an article frommicroorganisms including their spores.


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DISINFECTION:

Reducing the number of

pathogenic microorganisms to the

point where they no longer causediseases.


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Q-9

Which is true?

A. Bacteriostatic agent doesnot kill

bacteria B. Bactericidal agent kills bacteria

C. All of the above


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Bacteriostatic Agent:

An agent that inh ib i tsthe growth of bacteria, but

does not necessarily kill them.


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Bactericide:

An agent that kills bacteria. Most do not killEndospores.

Sporicide:

An agent that kills spores.


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Q-10

Which method is used to sterilize?


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A. Hot air oven

B. Autoclave

C. PasteurizationD. Ethylene oxide gas


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Q-11

Which organism causes plague

A. streptococcus pneumoniae

B. mycobacterium tuberculosisC. vibrio cholerae

D. yersinia pestis


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Bubonic Plague or the Black

Death

Epidemic swept thru Europe in the Middle

Ages (13th and 14th centuries)

40 million people were killed About 1/3 of the population of the continent

Etiological agent:

Yersinia pestis Gram (-) rod

2 Vectors

Rat

Flea


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Yersinia pestis - Gram (-) bacillus

Vectors - Rat and Flea


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Bubonic Plague Infection

1. Flea bite with Yersinia pestis

2. Bacteria multiply in the bloodstream

Bacteremia 3. Bacteria localize in lymph nodes,

especially axillary and groin areas


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4. Hemorrhaging occurs in lymph nodes, resulting in

black and blue swellings or Buboes (hence the name

Bubonic Plague or Black Death)

B b i Pl I f ti


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Bubonic Plague Infection 5. If untreated, about 50 % Mortality Rate

6. If bacteria spread to the lungs, it becomesPneumonic Plague and is now highly

contagious (Almost a 99 % Mortality Rate)


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microbiology quiz 2

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