ESOT microbiology

Many gram positive and gram negative bacteria produce exotoxins of medical importance. Which of the following is the characteristic of exotoxins?

• They can withstand temperatures above 60C for hours without loss of toxicity

• They are lipopolysaccharide complexes

• They are secreted by living cells

• They are weakly immunogenic

High efficiency particulate air (HEPA) filters are used to

• induce DNA damage that eventually kills microbial cells

• prevent binding of microbial enzymes with their substrates

• prevent microbial airborne contamination in operation theatres

• recover small numbers of organisms from large volumes of fluids

The association of endotoxin in Gram negative bacteria is a result of presence of

• peptidoglycan

• lipopolysaccharide

• polypeptide

• steroids

Which of the following statements is a good description of neisseria meningitidis?

• Gram positive cocci. They are arranged in grape-like clusters, non-sporing and non-motile. Capsules are produced by some strains.

• Gram positive cocci. They are arranged in chains, non-sporing and non-motile. Capsules are produced by some strains.

• Gram negative cocci. They are arranged in pairs, non-sporing and non-motile. Most fresh isolates are encapsulated.

• Gram negative cocci. They are arranged single, non-sporing and non-motile. Capsules are not produced.

Which of the following virulent antigens that are expressed by Enterobacteriase is termed H antigen?

• Somatic antigen

• Capsular antigen

• Cell wall antigen

• Flagella antigen

Which of the following bacteria is a gram negative obligate anaerobe?

• Chlamydia

• Bacteroides

• Pseudomonas

• Campylobacter

Which of the following bacteria is the causal organism of epidemic typhus?

• Anaplasma phagocytophilum

• Ehrlichia chaffeensis

• Rickettsia rickettsii

• Rickettsia prowazekii

Which of the following bacteria is the causal organism of gas gangrene?

• Clostridium perfringens

• Clostridium tetani

• Clostridium botulinum

• Clostridium difficile

Which of these statements is true regarding plasmids?

• Prokaryotic plasmids are unable to self-replicate

• Prokaryotic plasmids are not passed from one cell to another during replication

• Prokaryotic plasmids may carry genes that provide antibiotic resistance to the cell

• Plasmids are usually circular pieces of RNA

Which of the following microorganisms causes Scalded skin syndrome by producing exotoxin (exfoliatins):

• Streptococcus pyogens

• Pseudomonas aeruginosa

• Staphylococcus aureus

• Clastridium perfringens