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Questions and Answers
The normal microbial flora in the human body develops chaotically after birth.
The normal microbial flora in the human body develops chaotically after birth.
False
Breast-fed infants tend to have a predominance of gram-negative bacteria in their gastrointestinal tract.
Breast-fed infants tend to have a predominance of gram-negative bacteria in their gastrointestinal tract.
False
Moisture and temperature are factors that influence the composition of the normal flora on the skin.
Moisture and temperature are factors that influence the composition of the normal flora on the skin.
True
The skin's normal microbiota helps prevent the colonization of transient microbes.
The skin's normal microbiota helps prevent the colonization of transient microbes.
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Gram-negative bacilli are more commonly found in drier areas of the skin.
Gram-negative bacilli are more commonly found in drier areas of the skin.
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An infant's type of diet does not affect the composition of its normal flora.
An infant's type of diet does not affect the composition of its normal flora.
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Acne can occur when Propionibacterium, normally present on the skin, becomes trapped in hair follicles.
Acne can occur when Propionibacterium, normally present on the skin, becomes trapped in hair follicles.
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Normal flora can aid the host by producing nutrients that the host can utilize.
Normal flora can aid the host by producing nutrients that the host can utilize.
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Staphylococcus epidermidis is a common species found in the normal flora of the conjunctiva.
Staphylococcus epidermidis is a common species found in the normal flora of the conjunctiva.
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The upper respiratory tract does not contain a significant amount of microbiota.
The upper respiratory tract does not contain a significant amount of microbiota.
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Only Gram-negative bacteria are found in the population of the gastrointestinal tract.
Only Gram-negative bacteria are found in the population of the gastrointestinal tract.
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The normal flora of the oral cavity includes species from the Viridans Group Streptococci.
The normal flora of the oral cavity includes species from the Viridans Group Streptococci.
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Pathogens like Neisseria gonorrhoeae are typically found in high numbers in the conjunctiva.
Pathogens like Neisseria gonorrhoeae are typically found in high numbers in the conjunctiva.
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The large intestine is populated primarily by aerobic bacteria.
The large intestine is populated primarily by aerobic bacteria.
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Propionibacterium acnes is one of the dominant bacteria in the normal conjunctiva.
Propionibacterium acnes is one of the dominant bacteria in the normal conjunctiva.
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Hemophilus sp. and Neisseria sp. are commonly found in the upper respiratory tract flora.
Hemophilus sp. and Neisseria sp. are commonly found in the upper respiratory tract flora.
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Anaerobic Bacteriodes are the only species found in the colon of humans.
Anaerobic Bacteriodes are the only species found in the colon of humans.
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The presence of anaerobic methanogens in the human colon is an example of archaea as normal flora.
The presence of anaerobic methanogens in the human colon is an example of archaea as normal flora.
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Lactic acid produced by Lactobacillus acidophilus helps maintain a low pH in the vaginal epithelium.
Lactic acid produced by Lactobacillus acidophilus helps maintain a low pH in the vaginal epithelium.
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Urine in a healthy individual is typically contaminated with various microorganisms.
Urine in a healthy individual is typically contaminated with various microorganisms.
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Some bacteria in the colon can produce carcinogenic metabolites that may increase the incidence of colon cancer.
Some bacteria in the colon can produce carcinogenic metabolites that may increase the incidence of colon cancer.
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Staphylococcus epidermidis is an example of normal microflora in the vagina.
Staphylococcus epidermidis is an example of normal microflora in the vagina.
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Antibiotics can lead to alterations in gut flora and gastrointestinal disease.
Antibiotics can lead to alterations in gut flora and gastrointestinal disease.
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E. coli is found only in the intestines and never contaminates urine samples.
E. coli is found only in the intestines and never contaminates urine samples.
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Study Notes
Normal Human Microbial Flora
- The human body harbors microbes from birth, affecting anatomy, physiology, susceptibility to pathogens, and morbidity.
- Normal flora helps by competing for resources, producing nutrients, and protecting against pathogens.
- Flora development follows a sequence, establishing stable populations after birth.
- Environmental factors (temperature, pH, etc.) influence microbial community composition in different body regions.
- Birth canal exposure introduces organisms; breast-feeding favors Bifidobacteria and Lactobacilli. Bottle-feeding leads to a different flora.
- Immunoglobulins and breast milk components contribute to maintaining the flora.
Skin Flora
- Skin microbial communities vary across sites, influenced by moisture, occlusion, and temperature.
- Skin microbes (e.g., Staphylococci, Micrococci, Corynebacterium) often inhibit transient pathogens.
- Gram-negative bacilli colonize partially occluded areas more than drier regions.
- Skin commensals can cause problems (e.g., inflammation, acne) when conditions change (e.g., trapped in hair follicles).
Conjunctiva Flora
- Tears and blinking wash away foreign objects, limiting microbial colonization.
- Low microbial counts are usually observed on the conjunctiva, with Staphylococcus epidermidis, Propionibacterium acnes being prominent, along with occasional presence of other bacteria like Staphylococcus aureus, some streptococci and Hemophilus sp. Neisseria sp.
- Pathogens like Neisseria gonorrhoeae and Chlamydia trachomatis can attach to the conjunctiva.
Oral Cavity and Upper Respiratory Tract
- Oral cavity and upper respiratory tract are exposed to the external environment.
- Abundant and diverse microbiota inhabit these areas.
- Common bacteria include Staphylococcus epidermis, Viridans Group Streptococci (VGS), Streptococcus, Haemophilus, and Neisseria (pharynx).
- Lower respiratory tract has fewer microbes, predominantly containing Pseudomonas, Streptococcus, Prevotella, and Veillonella.
Gastrointestinal Tract Flora
- Stomach acid keeps numbers low.
- Duodenum has sparse flora mostly Gram-positive lactobacilli and Enterococcus faecalis.
- Ileum has a moderately mixed flora.
- Large intestine is heavily populated by anaerobes (bacteriodes, lactobacilli, bifidobacteria).
- Some anaerobic methanogens may also be present.
- Bacteria in the colon can aid in bile acid processing, vitamin K production, ammonia production, and can also influence carcinogenesis or be influenced by nutrition and antibiotics.
Urogenital Tract Flora
- Staphylococcus epidermidis, Enterococcus faecalis, and some alpha-hemolytic streptococci are present in the anterior urethra.
- Skin and fecal contaminants (E.coli, Proteus, Corynebacteria) may be present.
- Urine washes away microbes, making interior urogenital areas relatively free of microbes.
- Estrogen-influenced glycogen metabolism by Lactobacillus acidophilus creates an acidic environment in the vagina, preventing Candida albicans growth.
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Description
Test your knowledge on normal human microbial flora and its impact on health. This quiz covers topics such as microbial community composition, skin flora, and the role of environmental factors. Explore how these microbes affect human physiology and immunity.
