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Questions and Answers
A researcher is studying a newly identified bacterium that causes severe pneumonia in otherwise healthy individuals. The bacterium produces a potent toxin that damages lung tissue. Which classification is MOST appropriate for this bacterium?
A researcher is studying a newly identified bacterium that causes severe pneumonia in otherwise healthy individuals. The bacterium produces a potent toxin that damages lung tissue. Which classification is MOST appropriate for this bacterium?
- Opportunistic pathogen
- Normal flora
- Commensal organism
- True pathogen (correct)
An elderly patient recovering from surgery develops a bloodstream infection (sepsis) caused by Staphylococcus epidermidis. This bacterium is commonly found on the skin of healthy individuals without causing harm. What best explains the infection in this patient?
An elderly patient recovering from surgery develops a bloodstream infection (sepsis) caused by Staphylococcus epidermidis. This bacterium is commonly found on the skin of healthy individuals without causing harm. What best explains the infection in this patient?
- The patient's compromised immune system and recent surgery created an opportunity for _S. epidermidis_ to cause infection. (correct)
- The patient was likely exposed to a new, highly virulent strain of _S. epidermidis_.
- _S. epidermidis_ produces a potent toxin that directly attacks the immune system.
- _S. epidermidis_ is a virulent pathogen that always causes disease.
Yersinia pestis, the causative agent of plague, is classified as a true pathogen. What is the most significant implication of this classification regarding its ability to cause disease?
Yersinia pestis, the causative agent of plague, is classified as a true pathogen. What is the most significant implication of this classification regarding its ability to cause disease?
- It only causes disease in individuals with pre-existing conditions.
- It can cause disease in healthy individuals, regardless of their immune status. (correct)
- It primarily infects animals and only rarely affects humans.
- It requires a compromised immune system to establish infection.
A patient undergoing chemotherapy develops a severe fungal infection in their lungs. The causative agent is identified as Pneumocystis jirovecii, a fungus commonly found in the lungs of healthy individuals without causing disease. Which factor BEST explains why this patient developed the infection?
A patient undergoing chemotherapy develops a severe fungal infection in their lungs. The causative agent is identified as Pneumocystis jirovecii, a fungus commonly found in the lungs of healthy individuals without causing disease. Which factor BEST explains why this patient developed the infection?
Enterohemorrhagic Escherichia coli (EHEC) produces Shiga toxin, leading to bloody diarrhea and potential kidney failure, even in immunocompetent individuals. This characteristic is MOST indicative of which pathogenic classification?
Enterohemorrhagic Escherichia coli (EHEC) produces Shiga toxin, leading to bloody diarrhea and potential kidney failure, even in immunocompetent individuals. This characteristic is MOST indicative of which pathogenic classification?
A researcher is investigating potential virulence factors in a novel bacterial species. They discover that the bacterium produces a surface protein that allows it to adhere strongly to implanted medical devices. This bacterium is MOST likely to be an:
A researcher is investigating potential virulence factors in a novel bacterial species. They discover that the bacterium produces a surface protein that allows it to adhere strongly to implanted medical devices. This bacterium is MOST likely to be an:
Which of the following scenarios BEST exemplifies an infection caused by an opportunistic pathogen?
Which of the following scenarios BEST exemplifies an infection caused by an opportunistic pathogen?
A new viral strain is discovered that causes severe encephalitis (brain inflammation) in virtually all infected individuals, regardless of their age or health status. The virus replicates rapidly and efficiently evades the host's immune defenses. How should it be classified?
A new viral strain is discovered that causes severe encephalitis (brain inflammation) in virtually all infected individuals, regardless of their age or health status. The virus replicates rapidly and efficiently evades the host's immune defenses. How should it be classified?
A patient with severe burns covering a large portion of their body develops a systemic bacterial infection. The bacteria are identified as Pseudomonas aeruginosa, a common environmental organism. Why did the patient with severe burns develop the infection?
A patient with severe burns covering a large portion of their body develops a systemic bacterial infection. The bacteria are identified as Pseudomonas aeruginosa, a common environmental organism. Why did the patient with severe burns develop the infection?
A research team is developing a novel antimicrobial drug that specifically targets virulence factors produced by true pathogens. Which approach would represent the MOST appropriate strategy in the drug development process?
A research team is developing a novel antimicrobial drug that specifically targets virulence factors produced by true pathogens. Which approach would represent the MOST appropriate strategy in the drug development process?
Flashcards
True Pathogens
True Pathogens
Cause disease regardless of host microbiota or immune status.
Opportunistic Pathogens
Opportunistic Pathogens
Cause disease only when host defenses are compromised.
Pathogen
Pathogen
A microorganism that can cause disease.
Bacteria
Bacteria
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Viruses
Viruses
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Fungi
Fungi
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Protists
Protists
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Study Notes
- Pathogens are classified as either true pathogens or opportunistic pathogens.
True Pathogens
- True pathogens cause disease in a host, regardless of the host microbiota or immune system status.
- Many true pathogens produce virulence factors that contribute to disease.
- Enterohemorrhagic E. coli (EHEC) produces Shiga toxin, which inhibits protein synthesis, leading to bloody diarrhea, prolonged inflammation, and potentially kidney failure.
- True pathogens cause disease even in immunocompetent patients.
- True pathogens cause disease in healthy individuals and are typically associated with a specific disease.
- An example is Yersinia pestis, the causative agent of plague.
Opportunistic Pathogens
- Opportunistic pathogens only cause disease in situations that compromise the host defenses.
- Susceptible individuals include the very young, the elderly, pregnant women, chemotherapy patients, immunocompromised or deficient patients, and patients recovering from surgery, severe wounds, or burns.
- Opportunistic pathogens cause disease in a compromised host.
- Staphylococcus epidermidis is a member of the skin's normal flora and is typically avirulent.
- In hospitals, S. epidermidis can grow in biofilms on catheters, implants, and devices during surgical procedures.
- Once inside the body, S. epidermidis can cause serious diseases such as endocarditis.
Types of Pathogens
- Pathogens can be viruses, bacteria, protists, or fungi, which are microorganisms that can cause disease.
Bacteria
- Bacteria are microscopic, with even the largest only being 10 micrometers long.
- Once bacteria enter the body, they release toxins that can cause illness.
- Examples of bacterial infections include cholera, typhoid, food poisoning, and COVID-19.
Viruses
- Viruses are much smaller than bacteria.
- Viruses enter cells and reproduce inside them, producing hundreds or thousands of copies.
- Eventually, the host cell explodes, releasing the viruses to spread through the airways, bloodstream, or other routes.
- Examples of viral infections include the flu (influenza), measles, mumps, the common cold, and AIDS.
Fungi
- Thousands of fungal species exist, but only a few cause human diseases.
- Fungi can cause minor skin conditions or life-threatening diseases.
- Common fungal skin conditions include athlete's foot and ringworm.
- These conditions are contagious and can spread through direct contact or contact with common surfaces.
- Some opportunistic fungal diseases can take advantage when the immune system is weakened, such as in cases of cancer or AIDS.
Protists
- Protists are single-celled organisms.
- Some protists can contaminate food and cause amoebic dysentery, an intestinal infection that results in severe diarrhea.
- Protist pathogens can also be parasitic, living in other organisms and causing harm.
- Malaria is an example of a protist pathogen that lives in the blood and is transmitted by mosquitoes.
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