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Questions and Answers
What distinguishes strictly pathogenic microorganisms from opportunistic pathogenic microorganisms?
Which of the following is an example of an opportunistic pathogenic microorganism?
Which factor does NOT significantly influence the composition of a person's resident microbial flora?
What is an incorrect statement regarding the areas of the body with microbial flora?
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Which of the following does NOT represent a way in which opportunistic pathogens can cause disease?
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Which bacterium is primarily associated with surgical wound infections in the hospital setting?
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What is the primary role of Streptococcus mutans in the oral cavity?
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Which of the following is a common opportunistic pathogen found in the mouth and throat?
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What characteristic is unique to Methicillin Resistant Staphylococcus aureus (MRSA)?
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Which bacteria is commonly known for causing gastroenteritis?
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Which microorganism is known for its ability to survive in the acidic environment of the stomach?
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Which of the following bacteria is typically present in the large intestine and aids in digestion?
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What is a notable feature of the human gastrointestinal tract's microbial community?
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What is the primary distinction between colonization and infection?
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Which microorganism is commonly associated with causing diarrheal disease and colitis after antibiotic treatment?
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Which factor does NOT influence the microbial flora in the human body?
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Which of the following is classified as opportunistic pathogenic microorganisms?
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What role does the skin play in microbial colonization?
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Which of the following microorganisms is NOT part of the normal flora of the upper respiratory tract?
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How does hospitalization impact the microbial balance in a patient?
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Which of the following sites is known for the colonization of coagulase-negative Staphylococcus?
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Study Notes
Microbial Ecology
- Vision: To become a model in community engagement through excellence and international recognition in medical education, research, and health care.
- Mission: To promote higher standards in medical education, health care, research, and community health services.
- Values: Islamic values, excellence, creativity, compassion, leadership, and responsiveness to community.
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Learning Outcomes: Students should be able to:
- Differentiate between colonization and infection.
- Identify the distribution of microorganisms in the body.
- Explain the regulation of microbial populations in the body.
- Distinguish between strictly pathogenic and opportunistic pathogenic microorganisms.
- Identify the most common microorganisms in various body sites.
Introduction
- Factors influencing Microbial Flora: Age, diet, hormonal state, health, and personal hygiene.
- Fetal Development: The human fetus develops in a protected, sterile environment.
- Birth: At birth, the fetus is exposed to microbes from the mother and the environment.
- Colonization Order: Skin is colonized first, followed by the oropharynx, gastrointestinal tract.
- Microbial Balance Disruption: Changes in health can significantly disrupt the microbial balance, such as hospitalizations leading to the replacement of normally avirulent organisms.
- Clostridium difficile: Controlled in the gut, antibiotic treatment can alter the balance and lead to the proliferation of C. difficile, causing diarrhea and colitis.
Colonization and Infection
- Colonization: Organisms colonize a human, whether for a short period (transient) or permanently. They do not interfere with normal body functions.
- Infection: A pathogenic process characterized by damage to the host. Damage can result from microbial factors, such as, organ damage from microbe proliferation, or the production of toxins, or the host's immune response to the organism.
Distribution of Microorganisms
- Nose: Staphylococcus aureus, Staphylococcus epidermidis, Corynebacterium species.
- Mouth: Streptococci, Fusobacterium, Actinomyces, Leptotrichia, Veillonella.
- Throat: Streptococcus, Branhamella catarrhalis, Corynebacterium, Haemophilus, Neisseria, Mycoplasma.
- Large Intestine: Bacteroides fragilis, Escherichia coli, Proteus mirabilis, Klebsiella species, Lactobacillus species, Streptococcus species, Candida albicans, Clostridium species, Pseudomonas species, Enterococcus species.
- Skin: Staphylococcus epidermidis, Propionibacterium acnes, Pityrosporum ovale.
- Vagina: Lactobacillus species, Streptococcus species, Candida albicans, Gardnerella vaginalis.
- Urethra: Streptococcus species, Mycobacterium species, Escherichia coli, Bacteroides species.
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Upper Respiratory Tract:
- Non-haemolytic streptococci
- Alpha- non-haemolytic streptococci
- Neisseria species
- Streptococcus pneumoniae
- Streptococcus pyogenes
- Haemophilus influenzae
- Neisseria meningitidis
Ear and Eye
- Outer Ear: Coagulase-negative Staphylococcus is the most common organism.
- Eyes: Coagulase-negative staphylococci, Haemophilus spp., Neisseria spp., and viridans streptococci.
- Potential Pathogens: S. pneumoniae, S. aureus, H. influenzae, N. gonorrhoeae, P. aeruginosa.
Nose
- Staphylococcus aureus: Gram-positive bacterium, a major cause of surgical wound and systemic infections. Often referred to as MRSA (Methicillin-Resistant Staphylococcus aureus).
Mouth
- Streptococcus mutans: Gram-positive bacterium that resides in biofilms on teeth. Consumes sugar and converts it to lactic acid.
- Streptococcus pneumoniae: A more threatening bacteria that can colonize the mouth awaiting an opportunity to infect the lungs when defense mechanisms are low.
Gastrointestinal Tract
- Stomach: Helicobacter pylori thrives in the gastric acid environment, causing ulcers.
- Small Intestine: Colonized with various bacteria, fungi, and parasites (most anaerobes). Peptostreptococcus is one example
- Common Causes of Gastroenteritis: Salmonella, Campylobacter spp. (present in small numbers as asymptomatic residents). Various yeasts and non-pathogenic parasites can reside in the large intestine.
- Common Bacteria: Bifidobacterium, Eubacterium, Bacteroides, Enterococcus, and the Enterobacteriaceae family.
- E. coli: Present in virtually all humans from birth until death.
Colonic Habitant
- Colonic Flora: Digests polysaccharides that would otherwise be indigestible following flow through the colon (24-28 hours).
Genitourinary Tract
- List of Common Microbes: Actinomyces, Bacteroides, Bifidobacterium, Clostridium, Corynebacterium, Enterobacteriaceae, Enterococcus, Eubacterium, Fusobacterium, Gardnerella, Haemophilus, Lactobacillus, Mobiluncus, Mycoplasma, Peptostreptococcus, Porphyromonas.
Anterior Urethra
- Commensal Population: Lactobacilli, streptococci, coagulase-negative staphylococci. Most numerous.
- Transient Colonization: Faecal organisms (e.g., Enterococcus, Enterobacteriaceae, and Candida) can transiently colonize, invade the urinary tract, multiply in urine, and cause significant disease.
Normal Vaginal Flora
- Newborn to 6 Weeks: Lactobacilli.
- Pre-puberty: pH Neutral.
- Puberty: pH Acidic. Lactobacilli.
- Menopause: pH Neutral. S. epidermis, streptococcus, Enterococcus, Enterobacteriaceae, Gardnerella, Mycoplasma, Ureaplasma, and Candida.
At Birth, Puberty, and Menopause
- At Birth: Lactobacilli (6 months), Maternal estrogen declines, resulting in flora changes. Some examples of changes are to include Staphylococcus, Enterobacteriaceae, and Streptococcus.
- Puberty: Estrogen production initiated, Lactobacilli re-emerges. An increase in Streptococci (including group B), Enterococci, Gardnerella, Mycoplasma, Ureaplasma, Enterobacteriaceae, and anaerobic bacteria.
- Menopause: Estrogen declines, resulting in increased S. epidermidis, streptococcus, Enterococcus, Enterobacteriaceae, Gardnerella, Mycoplasma, Ureaplasma, and Candida.
Cervix
- Non-Colonization: The cervix is typically not colonized by bacteria.
- Important Pathogens: Neisseria gonorrhoeae and Chlamydia trachomatis; causes cervicitis (inflammation of the cervix). Actinomyces can also cause disease at this site.
Skin
- Not Rich Environment: Human skin is relatively dry, slightly acidic, and microbes obtain nutrition from dead cells.
- Primary Organisms: Propionibacterium acnes (Gram-positive anaerobe), Staphylococcus epidermidis.
Regulation
- Factors: Age, diet, hormonal state, and personal hygiene.
Microorganism Classification
- Strictly Pathogenic: Organisms always associated with disease (e.g., Mycobacterium tuberculosis, Neisseria gonorrhoeae, Plasmodium spp., rabies).
- Opportunistic Pathogenic: Typically members of the patient's normal microbial flora (e.g., Staphylococcus aureus, Escherichia coli, Candida albicans). They do not cause disease in their normal setting. Disease occurs when introduced into unprotected sites.
Questions
- Question 1: Which body area does not have a resident microbial flora? Answer: ear (and likely the eyes, although not explicitly stated).
- Question 2: Which factor greatly influences resident flora numbers? Answer: Hygiene.
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Description
Test your understanding of microbial ecology by exploring the role of microorganisms in the human body. This quiz will cover topics such as colonization vs. infection, distribution of microbes, and pathogenicity. Prepare to deepen your knowledge of the factors influencing microbial flora and their significance in health.
