Podcast
Questions and Answers
Which portal of entry is most commonly associated with respiratory infections?
Which portal of entry is most commonly associated with respiratory infections?
Why is unbroken skin an effective barrier against pathogens?
Why is unbroken skin an effective barrier against pathogens?
What characteristic allows Neisseria gonorrhoeae to cause infection in one area but not another?
What characteristic allows Neisseria gonorrhoeae to cause infection in one area but not another?
What role does the placenta play in the context of microbial entry into the body?
What role does the placenta play in the context of microbial entry into the body?
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Pathogens that enter through the gastrointestinal tract are typically resistant to what condition?
Pathogens that enter through the gastrointestinal tract are typically resistant to what condition?
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Which type of symbiotic relationship involves both species benefiting from the interaction?
Which type of symbiotic relationship involves both species benefiting from the interaction?
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What term describes bacteria that normally reside in the body and do not cause disease?
What term describes bacteria that normally reside in the body and do not cause disease?
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In which of the following sites would you expect an axenic environment?
In which of the following sites would you expect an axenic environment?
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What can lead to normal flora becoming opportunistic pathogens?
What can lead to normal flora becoming opportunistic pathogens?
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What is the primary reason for the overgrowth of C. difficile after antibiotics?
What is the primary reason for the overgrowth of C. difficile after antibiotics?
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Which of these describes transient microbiota?
Which of these describes transient microbiota?
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Which of the following is an example of parasitism?
Which of the following is an example of parasitism?
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Why might a patient with AIDS be more susceptible to certain infections?
Why might a patient with AIDS be more susceptible to certain infections?
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Which of the following pathogens has the highest likelihood of crossing the placenta?
Which of the following pathogens has the highest likelihood of crossing the placenta?
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What does the ID50 value indicate about a pathogen?
What does the ID50 value indicate about a pathogen?
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Which condition is NOT a potential result of a pathogen crossing the placenta?
Which condition is NOT a potential result of a pathogen crossing the placenta?
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What is the most common nosocomial infection?
What is the most common nosocomial infection?
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Which of the following agents is NOT commonly associated with opportunistic infections in seriously ill patients?
Which of the following agents is NOT commonly associated with opportunistic infections in seriously ill patients?
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What role does the epidemiology of a disease primarily play?
What role does the epidemiology of a disease primarily play?
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Which bacterial agent has the lowest ID50 value, indicating higher virulence?
Which bacterial agent has the lowest ID50 value, indicating higher virulence?
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What is a common pathway for pathogens to gain entry into the body?
What is a common pathway for pathogens to gain entry into the body?
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Study Notes
Symbiosis
- Symbiosis is a close relationship between different species
- Commensalism - Two species coexist without any effect on each other
- Mutualism - Two species benefit from their relationship
- Parasitism - One species benefits from an association to the detriment of the other
Normal Microbiota
- Also known as normal flora or indigenous microbiota
- Colonize the body from birth
- Most are non-pathogenic
- Resident microbiota remain throughout life
- Transient microbiota remain for a limited time
Axenic Sites
- Axenic means sterile, free from foreign organisms
- Examples include:
- In utero
- Kidney
- Prostate
- Middle and inner ear
Opportunistic Pathogens
- Normal microbiota can become pathogenic under certain conditions
- Immune suppression can lead to infections by organisms that wouldn't normally cause disease
- Location change of microbiota can lead to infection in unusual areas
-
Changes in relative number of normal flora can also lead to disease
- Microbial antagonism usually prevents overgrowth of one type of normal flora
- Overgrowth of one type can lead to disease
Portal of Entry
- Pathogens enter the body through various portals of entry
- Some pathogens have preferred portals of entry
- Examples of portals of entry:
- Mucous membranes
- Skin
- Placenta
- Parenteral route
Mucous Membranes
- Line body openings and provide a moist, warm environment for pathogens
- Respiratory tract is the most common site of entry
- Gastrointestinal tract is another route, some pathogens survive stomach acid
- Genitourinary tract (UTI, STI)
- Conjunctiva (viruses can enter the respiratory tract through the eyes)
Skin
- Acts as a barrier against pathogens due to its outer layer of dead cells
- Unbroken skin is a good defense
- Some fungi grow on the skin
- Pathogens can enter through openings (sweat glands, hair follicles)
- Others enter by burrowing into or digesting the skin (hookworms, Schistosomes)
Placenta
- Forms a barrier to most pathogens
- Some pathogens can cross the placenta and infect the fetus, causing:
- Spontaneous abortion
- Birth defects
- Premature birth
Parenteral Route
- Pathogens gain access via broken skin
- Injections
- Punctures
- Bites
- Cuts, wounds
- Surgery
- Cracking/splitting of skin
Measures of Pathogenicity
- LD50 (Lethal Dose 50): the number of microbes that kill 50% of test animals
- ID50 (Infectious Dose 50): the number of microbes required to produce demonstrable infection in 50% of test animals
Common Nosocomial Infections
- Nosocomial infections are acquired in healthcare settings
- Urinary tract infection (UTI) is the most common nosocomial infection
- Lower respiratory tract infection (LRTI) including bronchitis, tracheitis, pneumonia
- Surgical wound infection
- Bloodstream infection
Epidemiology
- Study of the occurrence, distribution, and spread of disease
-
Etiology of disease:
- Causative agent
- Mode of transmission
- Geographical distribution
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Description
This quiz explores the intricate relationships between different species, such as commensalism, mutualism, and parasitism. It also covers the concept of normal microbiota, their roles in health, and the conditions under which they can become opportunistic pathogens. Test your understanding of these critical microbiological concepts.
