MDS PREP
Which of the following is a distinguishing feature of exotoxins?
1) Lipopolysaccharides
2) Heat stable
3) Actively secreted by cells
4) Obtained only by cell lysis
General Microbiology Answer: 3
Exotoxins are produced and secreted by bacteria into the surrounding environment. They are typically proteins that can cause damage to the host by disrupting cellular processes. This active secretion distinguishes them from endotoxins, which are part of the bacterial cell wall and are released upon cell lysis.
The chemical nature of bacterial exotoxins is, a
1. low molecular weight polypeptide
2. lipopolysaccharide complex
3. protein
4. complex carbohydrate
Microbiology
Answer: 2
The chemical nature of bacterial exotoxins is, a
lipopolysaccharide complex
Flurescent microscopy is used to diagnose:
1) Mycobacterium tubeculosis
2) Staphylococcus aureus
3) Streptococcus capsulatum
4) Klebsilla aerogenes
Microbiology Answer: 1
Mycobacterium tuberculosis: Fluorescent microscopy can be used to detect Mycobacterium tuberculosis in clinical specimens, especially when using specific fluorescent dyes (like auramine-rhodamine) that bind to the mycobacterial cell wall. This method allows for the visualization of the bacteria under a fluorescence microscope, making it a valuable tool in the diagnosis of tuberculosis.
Which of the following is NOT a method used to produce a recombinant hepatitis B vaccine?
1) Cloning the HBsAg gene in E. coli
2) Cloning the HBsAg gene in yeasts Saccharomyces cerevisae
3) Extracting and purifying HBsAg particles from infected human plasma
4) Using baculovirus vectors to produce HBsAg in insect cells
General Microbiology Answer: 1
While recombinant hepatitis B vaccines are produced using various methods, cloning the HBsAg gene in E. coli is not one of them. Instead, the gene is typically cloned in yeast or insect cells to produce the surface antigen for the vaccine.
Which of the following is NOT a causative agent of dentoalveolar abscess?
1) Prevotella intermedia
2) P. melaninogenicus
3) Porphyromonas gingivalis
4) Fusobacterium nucleatum
General Microbiology Answer: 2Prevotella intermedia and P. melaninogenicus (now known as Aggregatibacter actinomycetemcomitans) are both anaerobic bacteria that can be found in the oral cavity and are involved in the pathogenesis of periodontal diseases, including dentoalveolar abscesses. Fusobacterium nucleatum is another anaerobic bacterium commonly found in dental plaque and is associated with various oral infections, including dentoalveolar abscesses.
Which of the following is a characteristic of endotoxins that makes them distinct from exotoxins?
1) They are heat labile
2) They are actively secreted by bacterial cells
3) They are proteins
4) They are part of the bacterial cell wall
General Microbiology Answer: 4
Endotoxins are components of the outer membrane of Gram-negative bacteria and are released when the bacteria die or divide. This structural characteristic differentiates them from exotoxins, which are secreted by living bacteria.
Which of the following is considered as a disadvantage in the application of dry heat as a sterilizing agent?
1. Requires excessive time
2. Does not destroy hepatitis viruses
3. Dulls instrument cutting edges
4. All of the above
Microbiology
Answer: 1
What is the typical incubation period for typhoid fever?
1) 1-3 days
2) 4-7 days
3) 10-14 days
4) 21-28 days
General Microbiology Answer: 3The typical incubation period for typhoid fever is 10-14 days: After the ingestion of Salmonella typhi, it typically takes 10-14 days for symptoms to appear. This period can sometimes be shorter or longer, but this is the most common range.