Microbiology and Biosafety Levels Quiz

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Questions and Answers

What is one of the benefits provided by normal microbiota to humans?

They disrupt the digestive process.

They synthesize vitamins. (correct)

They cause infectious diseases.

They inhibit the maturation of the immune system.

What term describes the imbalance of normal microbiota that can lead to health issues?

Symbiosis

Homeostasis

Dysbiosis (correct)

Allostasis

Which of the following best defines a pathogen?

A disease-causing microbe. (correct)

A genetically modified organism.

A microbe that promotes health.

A microbe that has mutualistic relationships.

What physiological process might allow a normally harmless microbiota to become pathogenic in another host?

Tropism Signup and view all the answers

Which situation could lead to the sudden flourishing of a pathogen like Clostridioides difficile?

Course of antibiotics disrupting normal microbiota. Signup and view all the answers

How can normal microbiota promote immune system maturation?

By competing with pathogens for resources. Signup and view all the answers

Which of the following statements about host-microbe interactions is correct?

Host-microbe interactions can be mutualistic. Signup and view all the answers

What can result from a disruption in the balance of normal microbiota?

Increased likelihood of disease. Signup and view all the answers

Which biosafety level is associated with agents that are well characterized and rarely cause disease in healthy individuals?

BSL-1 Signup and view all the answers

What type of agents does BSL-2 encompass?

Infectious agents that are not airborne Signup and view all the answers

What is a key characteristic of BSL-4 agents?

They require specialized personal protective equipment. Signup and view all the answers

Which biosafety level requires personnel to use an N95 or higher respirator?

BSL-3 Signup and view all the answers

BSL-2+ agents are noted for which of the following characteristics?

They are considered dangerous and incurable. Signup and view all the answers

How many BSL-3 facilities are estimated to exist across the United States?

Approximately 2,000 Signup and view all the answers

What is a common safety practice for handling BSL-2 agents?

Using personal protective equipment (PPE) Signup and view all the answers

What is the primary reason for tissue damage in tuberculosis?

The immune system attacking infected cells. Signup and view all the answers

Which mechanism allows a pathogen to evade phagocytosis?

Making a capsule to protect against phagocyte recognition. Signup and view all the answers

What is a characteristic of intracellular pathogens?

They spend most of their life cycle inside host cells. Signup and view all the answers

What is the role of latency in a pathogen's life cycle?

It helps the pathogen evade detection by the immune system. Signup and view all the answers

Which of the following best describes antigen masking?

Covering surface antigens to avoid immune detection. Signup and view all the answers

How can pathogens undermine host immune function?

By blocking immune system signals. Signup and view all the answers

What is a consequence of pathogens evolving to thrive inside the phagolysosome?

They gain access to nutrients and protection from immune responses. Signup and view all the answers

Which of the following examples illustrates a latent infection?

Herpes viruses presenting intermittent flare-ups. Signup and view all the answers

What does the lethal dose-50 specifically measure?

The amount of toxin needed to kill 50% of affected hosts Signup and view all the answers

Which option correctly describes the purpose of the infectious dose-50?

It describes how many cells are needed to infect 50% of hosts Signup and view all the answers

Which of the following anatomical sites is associated with nutrient acquisition regarding pathogens?

Respiratory Mucosa Signup and view all the answers

What common feature is shared by both the GI mucosa and respiratory mucosa in terms of pathogen interaction?

Both are involved in adhesion processes Signup and view all the answers

Which of the following is NOT a mechanism for pathogens to evade the immune system?

Nutrient acquisition Signup and view all the answers

Which of the following anatomical locations is least likely to be involved in the acquisition of pathogens?

Parenteral Signup and view all the answers

What role do toxins play in relation to the immune system?

They hinder immune system function Signup and view all the answers

In terms of disease etiology, what does parenteral exposure primarily refer to?

Introduction of pathogens via circumvention of the digestive system Signup and view all the answers

What is the main purpose of antigen masking in pathogens?

To evade detection by the immune system Signup and view all the answers

What characteristic distinguishes BSL-4 laboratories?

They handle agents that pose the highest risk Signup and view all the answers

Which of the following practices is essential when there is a risk of exposure to bodily fluids?

Wearing gloves Signup and view all the answers

What is a common method by which pathogens avoid phagocytosis?

Antigen variation Signup and view all the answers

Which biosafety level is typically assigned to agents that pose a moderate risk to personnel and the environment?

BSL-2 Signup and view all the answers

What is a critical response of the immune system that pathogens might suppress?

Phagocytosis Signup and view all the answers

Which of the following is an example of antigen variation?

Surface protein alteration Signup and view all the answers

Why is hand hygiene emphasized in infection control?

To prevent pathogen spread Signup and view all the answers

What is antigenic masking in pathogens?

The pathogen concealing its antigenic features. Signup and view all the answers

How does antigenic mimicry help pathogens evade the immune system?

By resembling the host's own molecules. Signup and view all the answers

What is the main consequence of antigenic variation in pathogens?

It prevents the pathogen from being recognized quickly by the immune system. Signup and view all the answers

Which method cannot be used by pathogens to avoid phagocytosis?

Inhibiting the production of immune cells. Signup and view all the answers

What does the interference of phagocytosis primarily involve?

Damaging phagocytic cells using insults. Signup and view all the answers

What might a pathogen do to thrive within a phagolysosome?

Evolve to withstand harsh conditions. Signup and view all the answers

Which strategy is NOT a method used by pathogens to suppress the immune response?

Producing new immune cells. Signup and view all the answers

What is a result of antigenic variation by pathogens?

The avoidance of a stronger immune response. Signup and view all the answers

Study Notes

Microbiology: Basic and Clinical Principles

Chapter 10 covers Host-Microbe Interactions and Pathogenesis
The chapter is presented by Janet Dowding, Ph.D., St. Petersburg College
A clinical case, "The Case of the Deadly Mistake," is presented to explore how host-microbe interactions explain medical mysteries. Students should visit a specified study area in Mastering Microbiology to view the case.
Students should be able to describe host-microbe interactions, discuss how shifts in normal microbiota levels or location may promote disease, explain why a commensal organism in one host could be a pathogen in another host, and explain tropism and its impact on pathogen emergence.
Host-microbe interactions are dynamic give-and-takes. Normal microbiota colonize diverse body systems including skin, digestive, genital, urinary, and respiratory systems.
Microbiota returns the favor by producing vitamins, competing with potential pathogens, and promoting immune system maturation. These microbes have mutualistic relationships with their hosts. Disrupting normal microbiota balance can compromise patient health.
Pathogens are disease-causing microbes, exhibit adaptations to interact with host tissues, causing harm to the host.

Dysbiosis

Dysbiosis is a disruption of microbiota.
Examples include antibiotics killing normal microbiota in the gut, allowing Clostridioides difficile to flourish and cause disease.

Tropism

Tropism is a pathogen's preference for specific host or tissue.
Most microbes exhibit tropism, which may change over time.
Emerging pathogens may broaden their host/tissue range to infect humans.
Successful invasion doesn't guarantee disease. Host factors like age, gender, and overall health influence disease development.

Introduction to Virulence

Pathogenicity is a microbe's ability to cause disease, whereas virulence describes the extent of disease a pathogen causes.
Students should define virulence, various virulence factors (e.g., structures for adherence, invasion), host-microbe interactions that impact pathogen virulence and transmission, Ro and R values and their use in epidemic management, and attenuated pathogens.
Virulence is an evolving property; making virulence factors requires energy investment, so only beneficial factors are maintained. Pathogens develop new factors in response to host and selective pressures.

Host Factors and Virulence

Virulence factors damage host cells directly or provoke dangerous immune responses.
Host properties such as immune fitness, and normal microbiota balance contribute to virulence. Examples demonstrating this include: influenza pandemics being more virulent in younger adults, and SARS-CoV-2 infections being more asymptomatic in children

Transmission and Virulence

Virulence factors influence transmission. Understanding transmission helps deduce virulence factors.
Pathogens easily transmitted to new hosts become more prevalent in populations.
Basic reproduction number (R0) measures a pathogen's transmissibility, with R0 = 2.0 meaning one infected person infects an average of two others.
R values change as host-pathogen interactions change in epidemics and pandemics, the effective reproduction number (Re) is more relevant

A Pathogen's Environment Influences Virulence

Virulence is an evolving property; pathogens respond to differing selective pressures (host factors and environmental factors) causing changes to virulence factors. Attenuated pathogens are infectious but weakened, often developed from growth in cell cultures; they lack virulence factors but are still infectious, and usually do not cause disease in immunocompetent hosts.

The Dosage of Pathogen and Toxin Exposure Affects Host Health Outcomes

Pathogens must first infect a host to establish disease.
Infectious dose-50 (ID50) is the number of cells or virions needed to establish infection in 50% of exposed hosts. Less infectious pathogens have a higher ID50, while highly infectious pathogens have a lower ID50.
Lethal dose-50 (LD50) is the amount of toxin needed to kill 50% of affected hosts that are not treated. ID50 and LD50 values can change based on species, immune fitness, and route of exposure.

Toxins

Toxins are molecules that harm hosts, such as causing tissue damage or suppressing the immune response.
Toxigenic microbes produce toxins, while toxemia involves toxins in the bloodstream, and there are two main classes of toxins: endotoxins and exotoxins.

Endotoxins

Endotoxins are found in the outer membranes of Gram-negative bacteria. Released when Gram-negative bacteria die.
Lipid A of LPS (lipopolysaccharide) is called endotoxin. It's toxic to humans and other animals. Excessive levels can trigger symptoms (fever, chills, body aches, hypotension, tachycardia, increased respiratory rate, and a feeling of disorientation, nausea, and vomiting) and potentially septic shock in humans. Septic shock, if left unchecked, is lethal as organs fail.
Endotoxemia is endotoxin in the bloodstream, triggered by localized or systemic infections, introduction of Gram-negative microbiota to locations where not naturally found, and surgical complications.

Exotoxins

Exotoxins are toxic proteins from actively growing bacteria, from both Gram-negative and Gram-positive bacteria.
They differ in how they are named; they are named based on the organism producing them or the type of cells targeted (e.g., neurotoxins, enterotoxins, hepatotoxins, and nephrotoxins).
Three main families exist based on their mode of action: Type I, Type II, and Type III exotoxins differ in their actions inside the host cell.

Five Steps to Infection

Five general tasks for pathogens to establish an infection:
Enter the host at a specific portal of entry
Adhere to host tissues
Invade host tissues to obtain nutrients.
Replicate while warding off host defenses.
Transmit to new host at specific portal of exit.
Portals of entry and exit may be the same.

Skin, Ocular, Otic, and Parenteral Entry

Integumentary system, based on its surface area, is our largest body system, and helps block most microbes from entering.
Pathogens use various means (abrsisions, cuts, injections, surgical incisions, physically boring through skin to invade conjunctiva).

Respiratory tract entry

Coughing and sneezing can spread pathogens in the air, from dust/soil. Infecting the respiratory tract doesn't guarantee an infection.

Gastrointestinal (GI) Tract Entry

Frequently have fecal-oral transmission.
Invade GI tract mucosa; infections originating in the GI tract can lead to GI tract symptoms.

Urogenital Tract and Transplacental Entry

Sexually transmitted pathogens enter via vaginal or urethral mucosa. Additional pathogens can enter via skin of genitalia. Some pathogens exhibit vertical transmission via transplacental entry.

Adhesion Factors

Adhesins are pathogen virulence factors for sticking to host cells. These may be particular to a cell (specific) or may not be (nonspecific). Examples include specific molecules like fimbriae or pili, and more general properties like hydrophobic interactions

Biofilms and Quorum Sensing

Bacteria form biofilms on almost any natural or manmade surface; biofilms are a source for 60-80% of human infections. Many healthcare-associated infections originate from biofilms, as seen with implanted devices (like catheters, prosthetic joints), kidney deposits (stones), and gallbladder deposits (gallstones).
Images illustrating biofilms on urinary catheters, and other examples.

Third: A Pathogen Must Invade Tissues and Obtain Nutrients

After entering and adhering, pathogens have options of staying on the surface or invading deeper tissues, or even entering cells to be an intracellular pathogen.
Invasion often damages host tissues and causes cytopathic effects

Invasins and Motility

Invasion into host tissues is facilitated by both Invasins, which are used to breach host tissues, and motility, the ability of pathogens to move around in and between host cells and tissues. Examples include collagenases, neuraminidase, coagulases, lipases, and proteases, as well as flagella or motility.

Tools to Obtain Nutrients: Siderophores and Extracellular Enzymes

Cellular pathogens need iron, so they use siderophores to snatch it from transferrin. Many pathogens secrete extracellular enzymes to break down local nutrients, helping them obtain nutrients as they damage host tissues. Examples include proteases and lipases.

Cytopathic Effects in the Host

Pathogens often damage host cells in cytopathic effects. These are further classified into cytocidal (cell killing) and non-cytocidal (damaging but not killing) effects.

Fourth: A Pathogen Must Evade Host Immune Defenses So It Can Replicate

Pathogens use various methods to evade the host immune systems. Such as hiding from immune defenses (intracellular pathogen lifestyle, latency, antigenic masking, mimicry and variation), and undermind them (interfering with phagocytosis, suppressing the immune response). Examples include interfering with phagocytosis by making a capsule, or neutralising digestive enzymes in phagocytes

Hiding From Host Immune Defenses

Include intracellular pathways, latency, antigenic masking, antigenic mimicry, and antigenic variation

Undermining the Host Immune Response

Pathogens can avoid immune detection while limiting/interfering with phagocytosis; they can use mechanisms to undermine/suppress immune response.

Fifth: A Pathogen Must Be Transmitted to a New Host

The final step is transmission to a new host, which is facilitated by symptoms such as itching, sneezing, coughing, and diarrhea leading to portal of exit for the pathogens

Exiting the Host

Portal of exit is the route a pathogen uses to exit the host.
Examples include feces, urine, saliva, mucus, semen, blood or fluids drained from wounds.

Safety and Health Care:

Criteria for assigning pathogens to biosafety levels (BSLs): Level of infectivity, Extent of disease caused and mortality rates, Mode of transmission, Availability of preventions and treatments

Biosafety Levels

There are 4 major Biosafety levels to consider (from 1 to 4).
BSL-1 agents are well-characterized, rarely cause disease, and pose minimal risk (e.g., Bacillus subtilis, E. coli K-12 strains).
BSL-2 agents are infectious, not airborne, and include bodily fluids as potential transmission vectors (e.g., Staphylococcus aureus, Herpes simplex viruses, most influenza strains, Clostridium tetani, Salmonella species; HIV). BSL-2+ agents are more serious/incurable and not preventable.
BSL-3 agents are serious or lethal, have airborne transmission, and may be treatable (e.g., Coxiella burnetii, Mycobacterium tuberculosis).
BSL-4 agents are dangerous or exotic, lethal in humans, and lack cures or treatments (e.g., Ebola and Marburg).

Infection Control Practices

Healthcare facilities have infection control teams to limit infection risks for workers and patients. Standard precautions treat all patients as potential sources of infection, using hand hygiene, glove changing, barrier clothing, face shields, mask-wearing, sharps waste management, and surface disinfection. Transmission precautions target specific infections using contact, droplet, and airborne precautions.

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Description

Test your knowledge on the benefits of normal microbiota, the implications of microbial imbalance, and the various biosafety levels. This quiz covers essential concepts such as pathogens, host interactions, and the role of microbiota in health. Perfect for microbiology students and professionals alike.