Quiz 2

Dr. Ashish Jawarkar

M.D. Path

Parul Sevashram Hospital

Q-1

Which class of organisms causes the disease in picture

Athlete’s foot

A. Bacteria B. Fungi C. Virus D. Protozoa

Fungi

Eukaryotic organisms with rigid cell wall

Yeasts Single-celled Reproduce by budding

Molds Large, fuzzy,

multicelled organisms Produce spores

Superficial infections Athlete’s foot Ringworm Thrush

Can cause systemic infections

Q-2

Which of the following is semipermeable A. cell membrane B. cell wall C. Nucleus D. Ribosomes

Cytoplasmic (Plasma) membrane Thin layer 5-10 nm, separates cell wall from cytoplasm

Acts as a semipermeable membrane: controls the inflow and outflow of metabolites

Composed of lipoproteins with small amounts of

carbohydrates

Q-3

What are the contents of Mac Conkey’s medium?

A. Peptone B. Lactose C. Neutral Red D. All of the above

Differential mediaDifferential media A media which has substances incorporated in it A media which has substances incorporated in it

enabling it to distinguish between bacteria.enabling it to distinguish between bacteria. Eg: Mac Conkey’s mediumEg: Mac Conkey’s medium

PPeptoneeptone LLactoseactose AAgargar NNeutral redeutral red TTaurocholate aurocholate

Distinguish between lactose fermenters & non Distinguish between lactose fermenters & non lactose fermenters.lactose fermenters.

Lactose fermenters – Lactose fermenters – PinkPink colonies colonies Non lactose fermenters – colourless coloniesNon lactose fermenters – colourless colonies

Q-4

What is this used for?

For removing oxygen, to grow anaerobic bacteria

ANAEROBIC CULTURE METHODSANAEROBIC CULTURE METHODS Anaerobic bacteria differ in their requirement Anaerobic bacteria differ in their requirement

and sensitivity to oxygen.and sensitivity to oxygen. Cl.tetani is a strict anaerobe – grows at an Cl.tetani is a strict anaerobe – grows at an

oxygen tension < 2 mm Hg.oxygen tension < 2 mm Hg.

Methods:Methods: Production of vacuumProduction of vacuum Displacement of oxygen with other gasesDisplacement of oxygen with other gases Chemical methodChemical method Biological methodBiological method Reduction of mediumReduction of medium

Production of vacuum:Production of vacuum: Incubate the cultures in a vacuum desiccator.Incubate the cultures in a vacuum desiccator.

Displacement of oxygen with other gasesDisplacement of oxygen with other gases Displacement of oxygen with hydrogen, nitrogen, Displacement of oxygen with hydrogen, nitrogen,

helium or COhelium or CO22..

Eg: Candle jarEg: Candle jar

Chemical methodChemical method Alkaline pyrogallol absorbs oxygen.Alkaline pyrogallol absorbs oxygen.

McIntosh – Fildes’ anaerobic jarMcIntosh – Fildes’ anaerobic jar Consists of a metal jar or glass jar with a metal Consists of a metal jar or glass jar with a metal

lid which can be clamped air tight.lid which can be clamped air tight. The lid has 2 tubes – gas inlet and gas outletThe lid has 2 tubes – gas inlet and gas outlet The lid has two terminals – connected to The lid has two terminals – connected to

electrical supply.electrical supply. Under the lid – small grooved porcelain spool, Under the lid – small grooved porcelain spool,

wrapped with a layer of palladinised asbestos.wrapped with a layer of palladinised asbestos.

Working:Working: Inoculated plates are placed inside the jar and Inoculated plates are placed inside the jar and

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

and the air inside is evacuated. and the air inside is evacuated. The outlet tap is then closed and the inlet tube is The outlet tap is then closed and the inlet tube is

connected to a hydrogen supply.connected to a hydrogen supply. After the jar is filled with hydrogen, the electric After the jar is filled with hydrogen, the electric

terminals are connected to a current supply, so terminals are connected to a current supply, so that the palladinised asbestos is heated.that the palladinised asbestos is heated.

Act as a catalyst for the combination of Act as a catalyst for the combination of hydrogen with residual oxygen.hydrogen with residual oxygen.

Gaspak Commercially available disposable envelope. Contains chemicals which generate H2 and CO2 on

addition of water. Cold catalyst – in the envelope Indicator is used – reduced methylene blue.

Colourless – anaerobically Blue colour – on exposure to oxygen

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

Important Vocabulary :

magnification  \mag-ne-fe-'ka-shen\ n 1. apparent enlargement of an object 2. the ratio of image size to actual size A magnification of "100x" means that the image is 100 times bigger than the actual object.

resolution  \rez-e-loo-shen\ n 1. clarity, sharpness 2. the ability of a microscope to show two very close points separately

Q-6

Which type of microscope has been used for taking this picture?

A. Bright field microscope B. Dark field microscope C. Phase contrast microscope D. Fluorosence microscope

Bright-field Microscope Contains two lens systems for magnifying

specimens Specimens illuminated directly from above or

below Advantages: convenient, relatively

inexpensive, available Disadvantages: R.P 0.2 m at best; can

recognize cells but not fine details Needs contrast. Easiest way to view cells is

to fix and stain.

Different magnifications

Special Microscopy Applications

Dark Field Phase Contrast Fluorescence Electron Microscope

Dark Field Microscopy

special condenser diaphragm occludes direct light,

passes wide angle light

angle too wide to enter objective

diffracted light

diffracted light scatteredenters objectiveobjects light on dark background

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

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 greenish light

Images appear coloured against a dark background

Electron Microscopy

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

Primary

staining

Decolorisation

Counter

staining

Primary stain

Decolorisation

Counter stain

Q-8

What is sterilisation? A. Killing all organisms on the object B. Removing only pathogenic organisms

DEFINITIONDEFINITION

STERILIZATIONSTERILIZATION

The process of freeing an article from The process of freeing an article from microorganisms including their spores.microorganisms including their spores.

DISINFECTION:DISINFECTION: Reducing the number of pathogenic microorganisms to the point where they no longer cause diseases.

Q-9

Which is true? A. Bacteriostatic agent doesnot kill

bacteria B. Bactericidal agent kills bacteria C. All of the above

Bacteriostatic Agent: Bacteriostatic Agent:

An agent that An agent that inhibitsinhibits the growth of bacteria, but the growth of bacteria, but does not necessarily kill them. does not necessarily kill them.

BactericideBactericide: : An agent that kills bacteria. Most do not kill An agent that kills bacteria. Most do not kill

Endospores.Endospores.

SporicideSporicide:: An agent that kills spores.An agent that kills spores.

Q-10

Which method is used to sterilize?

A. Hot air oven B. Autoclave C. Pasteurization D. Ethylene oxide gas

Q-11

Which organism causes plague A. streptococcus pneumoniae B. mycobacterium tuberculosis C. vibrio cholerae D. yersinia pestis

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

Yersinia pestis - Gram (-) bacillus

Vectors - Rat and Flea

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

4. Hemorrhaging occurs in lymph nodes, resulting in “black and blue” swellings or Buboes (hence the name Bubonic Plague or Black Death)

Bubonic Plague Infection 5. If untreated, about 50 % Mortality Rate 6. If bacteria spread to the lungs, it becomes

Pneumonic Plague and is now highly contagious (Almost a 99 % Mortality Rate)