Normal Human Microbiota

Question 1

The term “normal microbial flora” denotes the population of microorganisms that inhabit the skin and mucous membranes of healthy normal persons.

Normal microbiota provides a first line of defense against ____, assist in digestion, play a role in toxin degradation, and contribute to maturation of the immune system.

Normal flora organisms are either ___ or____

Viruses, protozoa, and helminths are not considered to be members of the normal flora (but humans can be carriers of some of these organisms).

Answer 1

microbial pathogens

bacteria or yeasts.

Question 2

Normal flora organisms inhabit the body surfaces exposed to the environment, such as the ___,___,___,&____.
Members of the normal flora differ in number and kind at various anatomic sites.

Answer 2

skin, oropharynx, intestinal tract, and vagina

Question 3

Diagram check

Question 4

The transient microbiota is derived from the environment, does not produce disease, and does not establish itself permanently on the surface. Members of the transient microbiota are generally of little significance so long as the normal resident flora remains intact.

• However, if the resident microbiota is disturbed, transient microorganisms may colonize, proliferate, and produce disease.

Question 5

The microorganisms that are constantly present on body surfaces are commensals. Their flourishing in a given area depends on physiologic factors of temperature, moisture, and the presence of certain nutrients and inhibitory substances.

Members of the resident microbiota in the intestinal tract synthesizes? & helps in ?

Answer 5

vitamin K and aid in the absorption of nutrients.

Question 6

Definition: Normal microbiota, also known as resident flora, are the microorganisms that normally inhabit various body sites, such as the skin and mucous membranes, without causing disease in healthy individuals.

Function: One of the primary roles of the normal microbiota is to prevent the colonization of pathogenic organisms, a process known as “bacterial interference.”

Question 7

How does Bacterial Interfere with the normal flora if the body

Answer 7

Competition for Receptors or Binding Sites: Normal microbiota occupy attachment sites on host cells, preventing pathogens from finding a place to adhere.

Competition for Nutrients: Resident microorganisms consume available nutrients, making them scarce for invading pathogens.

Mutual Inhibition by Metabolic or Toxic Products: Normal microbiota produce metabolic byproducts or toxins that can inhibit the growth of potential pathogens.

Production of Antibiotic Substances or Bacteriocins: Some normal microbiota produce antibiotic-like substances or bacteriocins that specifically target and inhibit the growth of competing microorganisms.

Question 8

What’s the Impact of Suppression of Normal Microbiota:

Answer 8

Partial Local Void: When the normal microbiota are suppressed, such as by antibiotics, a local void is created on the skin or mucous membranes.

Opportunistic Infections: This void can be filled by opportunistic organisms from the environment or other parts of the body. These opportunistic organisms can colonize the area and potentially become pathogenic, leading to disease.

Question 9

Easy-to-Understand Analogy: Imagine the normal microbiota as the local community that keeps a neighborhood safe by occupying homes and businesses. When these residents are removed (e.g., by antibiotics), vacant properties become susceptible to squatters (opportunistic pathogens) who can cause trouble (disease).

Question 10

Pathogenic Potential: However, under certain circumstances, these typically non-pathogenic organisms can become harmful:

Environmental Shift: When these organisms are forcibly removed from their usual habitats and introduced into new environments, such as the bloodstream or deeper tissues, they may cause disease

Question 11

Whats an example of a normal human flora that turns pathogenic due to change in habitat

Answer 11

Viridans Group Streptococci:

Normal Habitat: These are common residents of the upper respiratory tract, where they coexist without causing harm.

Pathogenic Scenario: If these bacteria are introduced into the bloodstream, for instance, during a tooth extraction or oral surgery, they can travel to other parts of the body. In the bloodstream, they may:

• Settle on Heart Valves: Particularly on deformed or prosthetic heart valves.
• Cause Disease: This can lead to infective endocarditis, a serious condition characterized by inflammation of the heart valves.

Question 12

Mechanism:

Environmental Adaptation: Normal microbiota are adapted to specific environmental conditions that limit their invasiveness.

Displacement and Invasion: When these conditions change drastically, such as through medical procedures or injuries, the bacteria can invade new areas of the body where they are not normally found.

Pathogenic Behavior: In these new environments, their presence can trigger harmful infections and inflammatory responses.

Question 13

Image

Question 14

What’s Bacteroides Species, their normal habit and Their Pathogenic Potential and resulting dxs

Answer 14

Normal Habitat:

Large Intestine: Bacteroides species are the most common resident bacteria in the large intestine. In this location, they are generally harmless and contribute to normal intestinal function.

Pathogenic Potential:

Displacement: If Bacteroides are introduced into areas outside the large intestine, such as the peritoneal cavity or pelvic tissues, they can cause severe infections.

Conditions Leading to Pathogenicity:

Trauma: Physical injury that allows these bacteria to enter sterile areas of the body.

Predisposing Factors: Such as immunosuppression or the presence of foreign bodies (e.g., prosthetic devices), which can enhance the bacteria’s ability to cause disease.

Resulting Diseases:

• Suppuration: The formation of pus due to bacterial infection.
• Peritonitis: Inflammation of the peritoneum, typically caused by bacterial infection.
• Bacteremia: Presence of bacteria in the blood, which can lead to serious systemic infections.

Question 15

Normal Microbiota of the Skin

Characteristics:

Diverse Microorganisms: The skin, as the body’s largest organ, hosts a wide variety of microorganisms. Most of these are harmless or beneficial, contributing to the skin’s health and function.

Exposure: Due to constant contact with the environment, the skin frequently harbors transient microorganisms, which may come and go.

Question 16

Resident Flora of the skin xteristic

Consistency: Despite the presence of transient microorganisms, the skin maintains a stable and well-defined population of resident flora.

Influencing Factors:

Secretions: Natural skin secretions can influence the composition of resident microbiota.

Clothing: Habitual wearing of clothing can create microenvironments on the skin that affect microbial populations.

Proximity to Mucous Membranes: Areas near mucous membranes, such as the mouth, nose, and perineal region, have distinct microbial communities influenced by these nearby tissues.

Question 17

Predominant Resident Microorganisms of the Skin includes

List the Aerobic and Anaerobic Diphtheroid Bacilli:

Answer 17

Corynebacterium
Propionibacterium

Question 18

Aerobic and Anaerobic Diphtheroid Bacilli:

Corynebacterium: These bacteria are commonly found on the skin and are generally harmless, although some species can cause infections under certain conditions.

Propionibacterium: These anaerobic bacteria are also normal inhabitants of the skin, playing a role in maintaining skin health

Question 19

Examples of Nonhemolytic Aerobic and Anaerobic Staphylococci:

& normal skin flora

Answer 19

Nonhemolytic Aerobic and Anaerobic Staphylococci:

Staphylococcus epidermidis: A common skin bacterium, part of the normal flora, and usually nonpathogenic.

Other Coagulase-negative Staphylococci: These bacteria are part of the normal skin flora and are usually harmless.

Staphylococcus aureus: Occasionally found on the skin, this bacterium can cause infections if it enters the body through cuts or other breaks in the skin.

Peptostreptococcus species: These anaerobic bacteria are part of the normal skin flora and are usually harmless.

α-hemolytic Streptococci (Viridans Streptococci):

Normal Skin Flora: These bacteria are part of the normal skin flora and are usually nonpathogenic.

Enterococci (Enterococcus Species):

Part of Normal Flora: These bacteria are generally found in the gastrointestinal tract but can also be present on the skin.

Gram-negative Coliform Bacilli and Acinetobacter:

Part of Normal Flora: These bacteria can be found on the skin and are usually harmless.

Fungi and Yeasts:

Skin Folds: These organisms are often present in skin folds and can be part of the normal skin flora.

Acid-fast, Nonpathogenic Mycobacteria:

Sebaceous-rich Areas: These bacteria occur in areas rich in sebaceous secretions, such as the genitalia and external ear.

Question 20

Gram-positive, Aerobic, Spore-forming Bacilli:

Ubiquitous in Environment: These bacteria are commonly found in air, water, and soil and can be present on the skin without causing harm

Question 21

Gram-positive, Aerobic, Spore-forming Bacilli:

Ubiquitous in Environment: These bacteria are commonly found in air, water, and soil and can be present on the skin without causing harm.

Question 22

What are the Factors Eliminating Nonresident Microorganisms

Answer 22

Low pH:

The skin’s low pH creates an environment that is inhospitable to many nonresident microorganisms.

Fatty Acids in Sebaceous Secretions:

These fatty acids can inhibit the growth of nonresident microorganisms, helping to maintain the skin’s normal flora.

Presence of Lysozyme:

Lysozyme is an enzyme that can break down bacterial cell walls, helping to eliminate nonresident microorganisms from the skin.

Question 23

Impact of Hygiene Practices

Sweating, Washing, and Bathing:

Profuse sweating or routine washing and bathing do not significantly modify the normal resident flora of the skin.

Vigorous Scrubbing with Disinfectants:

Using soap containing hexachlorophene or other disinfectants can temporarily diminish the number of superficial microorganisms. However, the normal flora is rapidly replenished from sebaceous and sweat glands, even when contact with other skin areas or the environment is minimized.

Question 24

Normal Microbiota of the Mouth and Upper Respiratory Tract

What are the Flora of the Nose:

Answer 24

Prominent Corynebacteria: These bacteria are commonly found in the nose and are generally harmless.

Staphylococci: Including S. epidermidis (normal flora, usually nonpathogenic) and S. aureus (potentially pathogenic, can cause infections).

Question 25

Wide Spectrum of Organisms in Nose, Throat, and Mouth:

The nose, throat, and mouth harbor a diverse range of microorganisms, including various streptococcal and staphylococcal species.

Question 26

Lower Bronchi and Alveoli:

Typically contain few, if any, microorganisms under normal circumstances.

Question 27

Significant Microorganisms in the Nose:

Answer 27

Significant Microorganisms in the Nose:

Streptococcal Species: Various species of streptococci colonize the nose, contributing to the normal flora.

Staphylococcal Species: Besides S. epidermidis and occasional S. aureus, other staphylococcal species may also be present.

Question 28

What’s the Pathogenic Potential of S. aureus:

Answer 28

Pathogenic Potential of S. aureus:

• S. aureus: Known for its pathogenic potential, S. aureus can cause infections, particularly in healthcare settings where it may be carried on the skin, nasal passages, or perianal areas of healthcare personnel.

Occasional Outbreaks and Transmission

• Healthcare Settings: Outbreaks of disease, especially in newborn nurseries, can sometimes be traced back to carriage of S. aureus by healthcare personnel. This underscores the importance of hygiene practices and infection control measures in healthcare environments.

Question 29

In summary, the nose, throat, and mouth harbor a diverse microbiota that includes various streptococcal and staphylococcal species. While most of these organisms are harmless and part of the normal flora, S. aureus, in particular, can pose a risk if it causes infections, especially in healthcare settings.

Question 30

What are the Normal Microbiota of the Conjunctiva

Answer 30

Predominant Organisms:

Diphtheroids: These are commonly found on the conjunctiva.

Staphylococcus epidermidis: A common non-pathogenic resident of the skin and mucous membranes.

Non-hemolytic streptococci: Present in small numbers and typically non-pathogenic.

Neisseriae and Gram-negative bacilli resembling haemophili (Moraxella species): Frequently present on the conjunctiva.

Question 31

Flow of Tears:

The flow of tears plays a crucial role in controlling the conjunctival flora. Tears contain lysozyme, an antibacterial enzyme that helps keep the microbial population in check.

Question 32

Flow of Tears:

The flow of tears plays a crucial role in controlling the conjunctival flora. Tears contain lysozyme, an antibacterial enzyme that helps keep the microbial population in check.

Question 33

What’s the Normal Microbiota of the Gingival Crevices

Answer 33

Normal Microbiota of the Gingival Crevices

Anaerobic Bacteria:

Bacteroides, Prevotella, Fusobacterium, Clostridium, and Peptostreptococcus: These anaerobic bacteria thrive in the low oxygen environment of the gingival crevices.

Potential Pathogenicity: If aspirated, these organisms can cause lung abscesses, particularly in debilitated patients with poor dental hygiene.

Question 34

What’s the Normal Microbiota of the Gingival Crevices

Answer 34

Normal Microbiota of the Gingival Crevices

Anaerobic Bacteria:

Bacteroides, Prevotella, Fusobacterium, Clostridium, and Peptostreptococcus: These anaerobic bacteria thrive in the low oxygen environment of the gingival crevices.

Potential Pathogenicity: If aspirated, these organisms can cause lung abscesses, particularly in debilitated patients with poor dental hygiene.

Question 35

What’s the Normal Microbiota of the Gingival Crevices

Answer 35

Normal Microbiota of the Gingival Crevices

Anaerobic Bacteria:

Bacteroides, Prevotella, Fusobacterium, Clostridium, and Peptostreptococcus: These anaerobic bacteria thrive in the low oxygen environment of the gingival crevices.

Potential Pathogenicity: If aspirated, these organisms can cause lung abscesses, particularly in debilitated patients with poor dental hygiene.

Question 36

Actinomyces species, protozoa, and Candida species are also part of the normal oral flora but can cause infections under certain conditions.

Answer 36

Actinomyces Species:

Normally present in tonsillar tissue and on the gingivae in adults. These bacteria are part of the normal oral flora but can cause infections under certain conditions.

Protozoa and Yeasts:

Various protozoa may be present in the mouth.

Candida Species: Yeasts that occur in the mouth and can cause opportunistic infections, particularly in immunocompromised individuals.

Question 37

Summary

The conjunctiva hosts a range of organisms including diphtheroids, S. epidermidis, non-hemolytic streptococci, Neisseriae, and Moraxella species, which are controlled by the antibacterial action of tears.

The gingival crevices harbor anaerobic bacteria such as Bacteroides, Prevotella, Fusobacterium, Clostridium, and Peptostreptococcus, which can cause lung abscesses if aspirated. Actinomyces species, protozoa, and Candida species are also part of the normal oral flora but can cause infections under certain conditions.

Question 38

Normal Flora of the Intestinal Tract
Stomach:

The stomach generally contains few organisms due to its low pH, which creates a hostile environment for bacterial growth.

Question 39

Small Intestine:

The small intestine usually harbors small numbers of _____&____

Larger numbers of these organisms are found in the ____, the last part of the small intestine before it transitions to the colon.

Answer 39

streptococci, lactobacilli, and yeasts (particularly Candida albicans).

terminal ileum

Question 40

Colon:

The colon is the major site for bacteria in the body. Approximately 20% of fecal mass consists of bacteria, with about 10^11 organisms per gram.

More than 90% of the fecal flora are ____, with ______ being the most significant.

Facultative Bacteria: ______ coli, are the most abundant facultative bacteria in the colon.

Answer 40

anaerobic bacteria with Bacteroides fragilis being the most significant.

Coliforms, particularly Escherichia coli are the most abundant facultative bacteria in the colon.

Question 41

Role of Intestinal Flora in Disease

The normal intestinal flora plays a significant role in extraintestinal diseases:

Escherichia coli (E. coli):

• E. coli is the leading cause of urinary tract infections (UTIs). These bacteria typically originate from the intestinal tract and ascend the urinary tract to cause infection.

Bacteroides fragilis:

• B. fragilis is a significant cause of peritonitis, an inflammation of the peritoneum often associated with perforation of the intestinal wall due to trauma, appendicitis, or diverticulitis.

Other Anaerobic Pathogens:

• Fusobacterium: These bacteria can be involved in various infections, including those affecting the mouth, throat, and lungs.
• Peptostreptococcus: This genus includes several species that can cause infections in various body sites, particularly in anaerobic conditions.

Question 42

Summary

The stomach has few bacteria due to its low pH, while the small intestine contains moderate numbers of streptococci, lactobacilli, and yeasts, especially in the terminal ileum.

The colon is densely populated with bacteria, primarily anaerobes like Bacteroides fragilis, and facultative bacteria such as E. coli.

Normal intestinal flora can lead to significant extraintestinal diseases, with E. coli causing UTIs and B. fragilis causing peritonitis after intestinal perforation. Other anaerobes like Fusobacterium and Peptostreptococcus also play roles in various infections.

Question 43

Additional Important Facultative Bacteria
Enterococcus faecalis:

This bacterium is a common cause of urinary tract infections (UTIs) and endocarditis (infection of the heart valves).
Pseudomonas aeruginosa:

Known for causing various infections, particularly in hospitalized patients with compromised immune systems.
Found in approximately 10% of normal stools and commonly present in soil and water.

Question 44

Effects of Antibiotic Therapy
Clindamycin and Normal Flora:

Antibiotic therapy can suppress the predominant normal flora, allowing opportunistic pathogens to overgrow.
Clostridium difficile: A rare bacterium that can overgrow after the suppression of normal flora by antibiotics, leading to severe colitis, specifically pseudomembranous colitis. This condition involves severe inflammation and damage to the colon.

Question 45

The major Vaginal Flora is? & what’s it’s function

Answer 45

Vaginal Flora

Lactobacillus species:

Predominantly colonize the vagina of adult women.

Responsible for producing acid, maintaining a low pH, which helps prevent the growth of potential pathogens.

During periods of low estrogen levels (before puberty and after menopause), lactobacilli are rare, leading to a higher vaginal pH.

Question 46

What’s the consequences of Lactobacilli Suppression:

Answer 46

Effects of Lactobacilli Suppression:

Antibiotics can suppress lactobacilli, allowing for the overgrowth of Candida albicans, a yeast that can cause Candida vaginitis.

Question 47

Summary

Enterococcus faecalis and Pseudomonas aeruginosa are important facultative bacteria causing UTIs, endocarditis, and various infections, especially in immunocompromised individuals.
Antibiotic therapy, particularly with clindamycin, can disrupt normal flora, leading to overgrowth of Clostridium difficile, causing severe pseudomembranous colitis.

Vaginal flora in adult women is primarily composed of lactobacilli, which maintain low pH and inhibit pathogen growth. Suppression of lactobacilli by antibiotics can result in Candida albicans overgrowth and Candida vaginitis.

Question 48

Normal Flora of the Genitourinary Tract

Vaginal Flora and Proximity to the Anus:

The vagina’s proximity to the anus allows for colonization by fecal flora members.

Recurrent Urinary Tract Infections (UTIs): Women prone to UTIs often harbor fecal organisms like E. coli and Enterobacter in the introitus (vaginal opening).

Question 49

Normal Flora of the Genitourinary Tract

Group B Streptococci:

Approximately 15% to 20% of women of childbearing age carry group B streptococci in the vagina.

Neonatal Sepsis and Meningitis: These bacteria can cause serious infections in newborns, such as sepsis and meningitis, acquired during childbirth.

Question 50

Staphylococcus aureus:

About 5% of women carry S. aureus in their vagina.
Toxic Shock Syndrome (TSS): Carriage of S. aureus increases the risk of TSS, a potentially life-threatening condition.

Question 51

Urine and the Urethra:

Sterile Urine: In a healthy person, urine is sterile within the bladder.
Contamination During Passage: As urine passes through the urethra, it often becomes contaminated with normal flora, including:

• Staphylococcus epidermidis
• Coliforms (e.g., E. coli)
• Diphtheroids
• Non-hemolytic streptococci
• Genitourinary Tract Skin Flora:

The skin around the genitourinary tract commonly hosts Staphylococcus saprophyticus, a notable cause of UTIs in women.

Question 52

Summary

Vaginal Flora: Proximity to the anus leads to colonization by fecal flora. Recurrent UTIs in women are often due to fecal organisms like E. coli and Enterobacter.

Group B Streptococci: Carried by 15%-20% of women of childbearing age, posing a risk of neonatal infections such as sepsis and meningitis.

Staphylococcus aureus: Found in 5% of women, increasing the risk of toxic shock syndrome.

Urine Contamination: While sterile in the bladder, urine can be contaminated by normal flora during its passage through the urethra.

Staphylococcus saprophyticus: Commonly found on the skin around the genitourinary tract, causing UTIs in women.