General Microbiology MCQs

Resolution power: It is the ability to produce separate images of closely placed objects so that they can be distinguished as two separate entities. The resolution power of: Unaided human eye is about 0.2 mm (200 μm) Light microscope is about 0.2 μm Electron microscope is about 0.5 nm The best resolution for an optical microscope is about 0.2 microns = 200 nm. Reference: Ananthanarayan and Paniker's Textbook of Microbiology 12th edition, Pg 7-8

Resolution power: It is the ability to produce separate images of closely placed objects so that they can be distinguished as two separate entities. The resolution power of: Unaided human eye is about 0.2 mm (200 μm) Light microscope is about 0.2 μm Electron microscope is about 0.5 nm Reference: Ananthanarayan and Paniker's Textbook of Microbiology 12th edition, Pg 11

Resolution power: It is the ability to produce separate images of closely placed objects so that they can be distinguished as two separate entities. The resolution power of: Unaided human eye is about 0.2 mm (200 μm) Light microscope is about 0.2 μm Electron microscope is about 0.5 nm Reference: Ananthanarayan and Paniker's Textbook of Microbiology 10th edition Chapter 2, Pg 10

Each peptidoglycan layer is mucopeptide (murein) chain composed of alternate subunits of N-acetyl muramic acid (NAM) and N-acetyl glucosamine (NAG) molecules. Teichoic acid are polymers of ribitol or glycerol joined by phosphate groups. Cell wall teichoic acid: Covalently linked to NAM of cell wall. Lipoteichoic acid: attached to lipids of cell membrane Reference: Ananthanarayan and Paniker's Textbook of Microbiology 12th edition, Pg 17

Surgical instruments are made from high-grade stainless steel and are coated for protection against the aggressive nature of the decontamination process (passivation layer) and prevents the steel from rusting. If at any time rust is found on the surface of an instrument it indicates that either the passivation layer is compromised or there is weakness in the metal from which the instrument is made. When rusty instruments are found, the items need to be taken out of service so as not to compromise patient care. Loan equipment or alternative instruments need to be provided as replacement. Reference: Ananthanarayan and Paniker's Textbook of Microbiology 10th edition Chapter 3, Pg 28-29

Most commonly used Sterilization operating conditions for autoclave: 121°C for 15 min at pressure of 15 psi. Reference: Ananthanarayan and Paniker's Textbook of Microbiology 12th edition, Pg 126

Sporicidal agents include: Aldehyde: Formaldehyde, glutaraldehyde Halogens: Sodium hypochlorite, iodine/iodophors Hydrogen peroxide Peracetic acid Ozone Peroxynitrite Gaseous or vapor-phase disinfectants like Ethylene oxide. Reference: Guideline for Disinfection and Sterilization in Healthcare Facilities (2008) Reference: Ananthanarayan and Paniker's Textbook of Microbiology 10th edition Chapter 3, Pg 28-29 Reference: Ananthanarayan and Paniker's Textbook of Microbiology 10th edition Chapter 3, Pg 31-33

Ionising radiations (X-rays, gamma rays from Cobalt 60, cosmic rays) Mechanism: It causes breakage of DNA without increasing surface temperature (cold sterilization). Spectrum: It destroys spores and vegetative cells, but not effective against viruses. Use: Disposable plastics, rubber or plastic syringes, infusion sets and catheters. Catgut sutures, bone and tissue grafts and adhesive dressings, antibiotics and hormones. Advantages: High penetrating power, Fast action and cold sterilization Sterilization control: Bacillus pumilus. Reference: Ananthanarayan and Paniker's Textbook of Microbiology 10th edition Chapter 3, Pg 31-33