Normal microbiota

1. What is the best definition of 'virulence' in the context of microbiology?

• The degree or measurement of pathogenicity of a microorganism.

• The ability of a microorganism to cause disease.

•  The resistance of a microorganism to antibiotics.

• The number of microorganisms required to infect a host.

1. How does the production of a capsule contribute to a bacterium's virulence?

• It helps the bacterium evade phagocytosis by host immune cells.

• It increases the bacterium's resistance to antibiotics.

• It helps the bacterium to move more quickly through host tissues.

• It enables the bacterium to adhere more strongly to host cells.

1. Which type of bacterial toxin is typically released upon the lysis of Gram-negative bacteria?

• Endotoxin

• Neurotoxin

• Enterotoxin

• Exotoxin

1. What is the most accurate definition of normal microbiota?

• All pathogenic microorganisms found in or on the human body.

• Microorganisms that are always present in the environment but rarely interact with humans.

• Microorganisms that permanently colonize the human body without causing disease under normal conditions.

• Any microorganisms that are acquired temporarily from the environment.

1. Which of the following human body sites is typically considered sterile and should NOT have normal microbiota?

• Skin surface

• Large intestine

• Bloodstream

• Upper respiratory tract (e.g., nasal passages)

1. How does normal microbiota protect the host from pathogenic organisms?

• By consuming all the host's nutrients, leaving nothing for pathogens.

• By activating the host's fever response against invaders.

• Through competitive exclusion, occupying niches and consuming nutrients.

• By directly attacking pathogens with antibiotics they produce.

1. Under what circumstances can normal microbiota become opportunistic pathogens?

• When they are exposed to harsh environmental conditions outside the body.

• Only if they acquire new virulence genes from other bacteria.

• When the host's immune system is compromised or they gain access to a normally sterile body site.

• When they are grown in a laboratory culture for an extended period.

1. Which of the following groups of microorganisms constitutes a significant part of the normal microbiota of the human skin?

• Methanogens and archaea

• Staphylococci (e.g., S. epidermidis) and Propionibacteria (e.g., P. acnes)

• Lactobacilli and Bifidobacteria

• Enterobacteriaceae (e.g., E. coli)

1. What is the primary role of chemoreceptors in bacterial chemotaxis?

• To produce flagella.

• To detect chemical signals in the environment.

• To synthesize ATP.

• To break down nutrients.

1. Which type of bacteria typically possesses a thick layer of peptidoglycan and no outer membrane?

• Gram-negative bacteria

• Gram-positive bacteria

• Archaea

• Mycoplasma