Bacteriologist Interview Questions And Answers

When answering this question keep focused on what the company can offer you in the long term so the interviewer knows that you are going to stick around for awhile. Tell the interviewer that you can see this as a long term career and that you are happy to learn the job and that you are also keen to pursue further education and even an additional degree to achieve your goals.

An often fatal and infectious disease, caused by ingestion or inhalation of spores of Bacillus anthracis, which are normally found in soil. It is acquired by humans through contaminated wool or animal products or by inhalation of airborne spores

Quaternary ammonium compounds are positively charged polyatomic ions, which concentrate at the cell surface and alter the physical and chemical properties of the membrane, thus killing the cefl. Examples inlcude Benzalkonium chloride and Cetrimonium bromide.

The two methods namely Kinyoun’s and Gabbetts dont involve heating of slides, hence called cold methods. Heating is substituted by increased concentration of phenol and prolonging the duration of staining. Kinyoun’s method is favoured for detection of Cryptosporidium oocysts in fecal samples. Gabbetts method has decolourizer and counterstain in one solution.

LoetTler’s methylene blue solution treated with Potassium hydroxide turns into Polychrome methylene blue after prolonged storage with shaking. Used in McFadyean’s reaction for Bacillus anthracis in blood films and demonstration of metachromatic granules of Corynebacterium diphtheriae.

Preparing for this question requires a little bit of self-awareness and strategy. You don't want to share that you have trouble working with difficult people or that you struggle with the details, as those are key aspects of your role. What you do want to focus on is a weakness that you could possibly turn into a strength or share something that would not be detrimental to your role that you are working on improving.

Refers to organisms that survive in the absence of oxygen (anearobic organisms), the absence of molecular oxygen, processes occurring in the absence of oxygen like anearobic respiration.

Agarose is obtained from seaweed and is used as a resolving medium in electrophoresis. It consists of non-sulfated linear polymer, which contains D-galactose and 3:6-anhydro-L-galactose alternately.

Cell wall theory: Cell wall of Gram positive bacteria are 40 times thicker than those of Gram negative cells, hence they are thought to help retain the dye-iodine complex.
Lipid Content Theory: Cell envelope of Gram negative bacteria contains an additional membrane (outer membrane). hence containing more lipids than Gram positive bacteria. Acetone or alcohol dissolves the lipid thus forming large pores in Gram negative bacteria through which the dye-iodine complex leaks out. Alcohol/acetone dehydrates Gram positive bacteria shrinking the cell wall and the closing the pores.
Magnesium Ribonucleate Theory: A compound of magnesium ribonucleate and basic protein concentrated at the cell membrane helps Gram positive bacteria retain the primary dye. Gram negative bacteria do not possess this substance.
Cytoplasmic pH Theory: The cytoplasm of Gram positive bacteria are said to be more acidic (2) than those of Gram negative ones (3). Hence the dye is said to bind with more affinity to Gram positive cells.

These are Gram positive, nonmotile, nonsporing, noncapsulated filaments that break into bacillary and coccoid elements. They resemble fungi, and most are free living, particularly in soil.

A minute protozoan, occurring as a single cell with a nucleus, that changes shape by extruding its cytoplasm, leading to the formation of pseudopodia, by means of which it absorbs food and moves

☛ Simple stain: where only one stain is used and all bacteria are stained similarly. Eg: F1ethylene blue, dilute carbol fuchsin
☛ Differential staining: where different bacteria stain differently to a common staining technique depending on their physiological properties. Eg: Gram’s stain and Acid fast staining
☛ Special stain: where structures of bacteria like spores. granules. capsule etc are demonstrated. Eg: silver impregnation technique for demonstration of spirochetes. Feulgen stain for demonstration of nucleus. Sudan black stain for demonstration of lipid vacuoles. Ryu’s stain for demonstration of flagella. Albert’s stain for demonstration of metachromatic granules.
☛ Negative staining: where the background is stained with an acidic dye such as India ink or Nigrosin. Used for demonstration of capsules.

☛ Extremely slender bacteria such as Treponema
☛ Cells containing waxy substances impermeable to stain such as Mycobacteria
☛ Minute intracellular bacteria such as Chlamydia and Rickettsia
☛ Cell organelles such as capsule. spore. flagella etc

Candida sps

For uniform distribution of heat, or else the slide may break.

121°C for 15 minutes at 15 pounds per square inch of pressure

Gamma rays. Electron beams and Ethylene oxide

Non-living factors that can affect life, like soil, nutrients, climate, wind etc.

☛ When over-decolourized by either prolonged exposure to decolourizer or using acetone alone.
☛ When cell wall gets damaged by exposure to lysozyme or cell wall acting antibiotics such as Penicillin.
☛ Old cultures, where cell wall is weakened or action of autolytic enzymes
☛ Those bacteria that are phagocytosed. where cell wall is acted upon by lysosomal contents

☛ A new slide must be used for every specimen. because scratch marks may give false positive.
☛ A uniform smear from thick portion of the sputum must be made.
☛ Staining jars should not be used to staining smear as there is risk to cross contamination
☛ Fresh blotting paper must be used for each smear for drying the slide to prevent transfer from one slide to another.

160°C for 60 mInutes

By filtration.

Sodium hypochlorite or Calcium hypochlorite

Glutaraldehyde or a combination of peracetic acid and hydrogen peroxide can be used.

It disinfects and solidifies egg and serum containing media such as U medium and LoelTiers serum slope.