Questions and Answers
What is the definition of normal flora in the human body?
Microorganisms that are always present and do not cause disease
What is the term used to describe the population of microorganisms that inhabit the skin and mucous membranes of healthy persons?
Microbiota
What is the characteristic of transient flora?
Temporarily present on the skin
Which of the following is NOT a site of the body with normal flora?
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What is the importance of knowing the sites of the body with no normal flora?
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What is the approximate number of microbial cells present in the human body?
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What is the primary function of bacteriocins produced by intestinal bacteria?
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What is a characteristic of a fetus at birth?
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Why does the normal flora differ from one human to another?
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What is the approximate number of microbial cells in the human gut?
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What is the consequence of a germ-free animal's caecum?
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What is the function of the normal flora in the development of certain tissues?
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What is the approximate number of bacteria present in the human physical structure?
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What percentage of fecal weight consists of bacteria?
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Which type of relationship is described when both the host and bacteria derive benefits from each other?
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What is the term used to describe the relationship between the normal flora and the host?
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Which type of flora is always present on or within the body?
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What is the role of E. coli in the human body?
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Which term refers to an organism that can cause an infection in individuals with normal host defenses?
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What is the term used to describe a state of being a carrier of pathogenic organisms but being free from disease?
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Which term is defined as the ability of a parasite to cause damage to the host?
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Who is an animal or plant on or in which a parasite or commensal organism lives?
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Which term refers to an organism that can cause infections in individuals with abnormal host defenses?
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What is the term used to describe an organism that is found normally on parts of the body that are exposed to the external environment?
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What type of relationship is commensalism?
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When E.coli leave the large intestine and cause infections, it is an example of?
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What role does a microbiologist play in the context of the text?
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What infections can E.coli cause when it gains access to body parts outside the large intestine?
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Which type of relationship involves one organism benefiting at the expense of the other organism?
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What should physicians avoid in the context of antimicrobial treatment?
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Study Notes
Normal Microbial Flora
- Normal microbial flora refers to the population of microorganisms that inhabit the skin and mucous membranes of healthy persons from birth to death.
- The human body is home to approximately 10^14 microbial cells.
Definition of Terms
- Normal flora: microorganisms that normally live on or in the body without causing disease.
- Resident flora: microorganisms that are always present on or in a person and usually do not cause disease.
- Transient flora: microorganisms that temporarily colonize the skin.
- Carrier state: state of being a carrier of pathogenic organisms, i.e., one who is infected but free from disease.
- Pathogen: an organism that can cause infection in individuals with normal host defenses.
- Commensal: an organism that is found normally on parts of the body exposed to the external environment.
- Opportunistic pathogen: an organism that can cause infection in individuals with abnormal host defenses.
- Pathogenicity: the ability of a parasite to inflict damage on the host.
- Virulence: a measure of pathogenicity in a microorganism.
- Host: an animal or plant on or in which a parasite or commensal organism lives.
Importance of Normal Flora
- Normal flora may antagonize other bacteria through the production of substances that inhibit or kill non-indigenous species.
- Intestinal bacteria produce substances like non-specific fatty acids, peroxides, and bacteriocins, which inhibit or kill other bacteria.
- Normal flora stimulates the development of certain tissues, such as the caecum and lymphatic tissues in the GI tract.
Sites of Normal Flora
- Gastrointestinal tract (GIT): home to approximately 10^14 microbial cells, with 40,000 bacterial species, 9 million unique bacterial genes, and 100 trillion microbial cells.
- Urogenital tract: harbors normal flora, with the vagina having a distinct microbiota.
- Skin: harbors normal flora, with approximately 10^12 bacteria on the skin.
Sites with No Normal Flora
- Sterile body sites: spleen, liver, pancreas, bladder, cerebrospinal fluid, and blood (unless infected).
Symbiosis
- Symbiosis: the relationship between normal flora and the host.
- Mutualism: both the host and bacteria benefit from each other.
- Commensalism: one organism benefits, and the other is unaffected.
- Parasitism: one organism benefits at the expense of the other organism.
Role of Microbiologist and Physician
- Microbiologist: accurate diagnosis through rapid and meaningful reporting.
- Physician: proper treatment with antimicrobial regimens, avoiding overuse/misuse of antimicrobials, and targeting pathogens, not normal flora.
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