Pathogenesis of Bacterial Infection

Pathogenesis refers to:

 The mechanisms involved in the production of disease

A pathogen is best defined as:

A microorganism capable of causing disease in a host

Pathogenicity is:

The ability of a microorganism to produce disease in a host

Virulence refers to:

The severity or degree of pathogenicity of a microorganism

Which statement best distinguishes pathogenicity from virulence?

Pathogenicity describes the ability to cause disease; virulence describes the degree or severity of disease

The normal flora (microbiome) refers to microorganisms that:

Exist on or in the body without causing disease

Commensal organisms can become pathogenic when:

The host is immunosuppressed or tissue barriers are breached

Virulent bacteria are characterised by:

An increased ability to invade or damage the host

A primary pathogen is:

A bacterium that can cause disease solely due to its presence within the host

Colonisation refers to:

Presence of microorganisms on host surfaces without causing disease

Virulence factors are:

Genetic, biochemical, or structural traits that enhance a pathogen’s ability to cause disease

Methicillin-resistant Staphylococcus aureus (MRSA) is best described as:

A highly virulent bacterium that can colonise or infect the host

Opportunistic bacteria are characterised by:

Causing disease only under specific conditions (e.g., immunosuppression)

Opportunistic infections are most likely to occur when:

A foreign body or prosthetic device is present

Which of the following is not a key factor influencing whether infection occurs?

Bacterial genome sequencing method

For a pathogen to cause disease and spread, it must:

 Enter, attach, evade host defences, cause damage, and exit

Which of the following diseases is most commonly transmitted via ingestion?

Salmonella food poisoning

Pathogens such as Mycobacterium tuberculosis typically enter the body via:

Inhalation of droplets or aerosols

Which of the following best represents infection via penetration or inoculation?

Staphylococcus aureus entering through skin breaks

Which of the following infections is typically transmitted through sexual contact?

Chlamydia

Which of the following pathogens is classically transmitted vertically from mother to child?

Group B Streptococcus

Which of the following best describes the role of bacterial adhesion in infection?

It establishes a stable bacterial population within the host and prevents clearance

Bacterial adhesion to host cells occurs primarily through:

Receptor–ligand interactions involving adhesins

What are adhesins? And, what do they recognise?

They are bacterial protein ligands that recognize specific receptors on host cells

Why is bacterial adhesion critical to infection?

It allows bacteria to resist mechanical clearance mechanisms of the host

A biofilm is best described as:

 A community of bacteria adhering to surfaces such as prosthetic joints or valves

Why are biofilm-associated infections particularly difficult to treat?

Biofilm formation protects bacteria and often requires removal of the prosthesis for eradication

Pathogenic invasion into host tissues is facilitated by:

Invasins

Describe the role of invasins

Proteins that damage host tissues and promote bacterial spread

Which of the following enzymes are classified as invasins?

Kinase, Collagenase, Hyaluronidase

Bacteria employ immune evasion mechanisms to:

 Ensure long-term survival within the host by avoiding immune clearance

Which bacterial structure helps inhibit phagocytosis?

Capsule composed of polysaccharides

Which of the following pathogens possess a capsule aiding in inhibition of phagocytosis?

Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae

Which of the following bacteria can escape the phagosome after being engulfed by phagocytes?

Listeria monocytogenes

The ability to prevent phagosome–lysosome fusion is a virulence mechanism of:

Mycobacterium tuberculosis

Which pathogen is capable of surviving within the phagolysosome?

 Staphylococcus aureus

The function of leucocidins is to:

Kill phagocytic immune cells by forming pores in their membranes

Panton–Valentine leucocidin is produced by:

Staphylococcus aureus

Streptolysin, a pore-forming enzyme that targets immune cells, is produced by:

Streptococcus species

Which statement about coagulase is correct?

It converts fibrinogen to fibrin, coating bacteria and protecting them from immune cells

Detection of coagulase activity in the laboratory is useful for identifying:

 Staphylococcus aureus

Which of the following bacterial products directly contribute to host cell damage?

Invasins, toxins, and superantigens

Which of the following statements best describes bacterial toxins?

They are chemical compounds that harm host tissues or immune cells

The two major categories of bacterial toxins are:

Endotoxins and exotoxins

Endotoxins are primarily associated with:

Gram-negative bacteria

Which of the following best describes the chemical composition of an endotoxin?

 Lipopolysaccharide (LPS)

Endotoxins are released:

During bacterial cell lysis or turnover

The release of lipopolysaccharide (LPS) can trigger:

Septic shock due to a pro-inflammatory cascade

Which condition is commonly associated with endotoxin release?

Meningococcal sepsis

Exotoxins are mainly produced by:

Gram-positive bacteria

Exotoxins are:

 Polypeptide or protein molecules

Exotoxins are released:

During bacterial growth, replication, or lysis

Exotoxins often act:

Specifically on certain target cells to cause localized or distant effects

Which of the following are types of exotoxins?

Cytotoxins, neurotoxins, enterotoxins

A superantigen is best described as:

A type of exotoxin that causes massive immune activation

Superantigens were first discovered in strains of:

Staphylococcus aureus

Superantigens cause shock syndromes primarily through:

Nonspecific activation of large numbers of T-cells via MHC class II interaction

Toxic shock syndrome toxin-1 (TSST-1) is produced by:

Staphylococcus aureus

Which of the following correctly matches the toxin type with its source?

Exotoxin
Gram-positive (and some Gram-negative) bacteria

Cholera, tetanus, and botulism are caused by:

Exotoxins

what is the difference between exo- and endotoxin release?

Exotoxins are secreted actively; endotoxins are released upon cell lysis

Which of the following is not a mechanism by which pathogens spread within the body?

Diffusion through epithelial DNA

Salmonella typhi spreads within macrophages, representing which dissemination route?

Carriage within macrophages

Ascending and descending spread of infection within a tract typically refers to:

Urinary or reproductive tracts

Skin-to-skin contact allows for transmission of pathogens primarily via:

Direct contact

Pathogens transmitted via coughing or sneezing use which route?

Respiratory (aerosol/droplet)

Pathogens transmitted through contaminated food or water typically use which route?

Ingestion

A pathogen causing genital ulcers or discharge would most likely be transmitted via:

Sexual contact

Vertical or perinatal transmission refers to infection:

From mother to child during pregnancy or delivery

Transmission of infection via a contaminated inanimate object (fomite) is an example of:

Environmental transmission

Host factors are best described as:

C. Conditions that increase a person’s susceptibility to infection or its severity

Host factors primarily:

C. Increase susceptibility and severity of infection

Which statement about extremes of age is true in relation to infection risk?

A. Both the very young and elderly are at increased risk due to reduced immune function

People with diabetes are more susceptible to infection because:

C. They have impaired immune function and poor circulation

Which of the following conditions or treatments can cause immunosuppression?

A. Chemotherapy and corticosteroids

Which of the following is not a disease that can lead to immunosuppression?

D. Influenza

Patients with asplenism are particularly vulnerable to infection because:

B. The spleen filters encapsulated bacteria from the bloodstream

Asplenic patients are especially susceptible to infections caused by:

B. Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae

Which of the following treatments increases infection risk due to immunosuppression?

B. Chemotherapy and long-term corticosteroids

Which of the following would represent a major breach in skin or mucosal barriers that increases infection risk?

C. Recent major surgery

Why do prosthetic materials (e.g., joint replacements or heart valves) increase infection risk?

B. They serve as surfaces for bacterial adhesion and biofilm formation

Bacteria in biofilms are difficult to eradicate because:

C. The biofilm protects them from antibiotics and immune responses

Which of the following medical devices is not commonly associated with an increased risk of infection?

D. Blood pressure cuffs

An anatomical abnormality or surgical complication can increase infection risk primarily because:

A. It reduces normal fluid drainage or tissue function

Antibiotic use can paradoxically increase infection risk by:

B. Disrupting the normal microbiome

Clostridioides difficile infection is commonly associated with:

B. Overuse of broad-spectrum antibiotics

Normal flora can cause opportunistic infection when:

A. Host immunity is compromised or barriers are breached

A primary pathogen differs from an opportunistic one because it:

B. Causes disease solely because of its presence in a healthy host

The function of adhesins and invasins in bacterial pathogenesis is to:

B. Facilitate bacterial attachment and entry into host cells

Bacteria evade immune responses through all of the following except:

D. Increased antibody production by the host

Exotoxins and endotoxins are bacterial products that cause:

B. Host cell toxicity via direct damage or immune dysregulation

The likelihood of infection increases with:

B. Extremes of age, chronic disease, and medical devices

Which environmental or lifestyle factor significantly compromises host defense against respiratory pathogens?

A. Regular exercise
B. Adequate sleep
C. Smoking
D. Balanced diet

C. Smoking

Malnutrition can increase susceptibility to infection primarily due to its effect on:

A. Blood pressure regulation
B. Immune system development and function
C. Bone density
D. Vision acuity

B. Immune system development and function

In a patient with a compromised immune system, the risk of developing candidiasis (a fungal infection) highlights the importance of:

A. Bacterial adhesion
B. Viral evasion strategies
C. The host's normal microbiome in preventing opportunistic infections
D. Pathogen dissemination routes

C. The host's normal microbiome in preventing opportunistic infections

Which of the following is an example of an opportunistic pathogen causing disease due to a breach in physical barriers?

A. Salmonella typhi causing typhoid fever after ingestion
B. Mycobacterium tuberculosis causing lung disease after inhalation
C. Staphylococcus aureus causing a surgical site infection
D. Neisseria gonorrhoeae causing a sexually transmitted infection

C. Staphylococcus aureus causing a surgical site infection

For a pathogen to cause disease, it generally needs to successfully achieve all the following steps EXCEPT:

A. Colonize host tissues
B. Evade host immune responses
C. Produce specific antibodies against host cells
D. Cause damage or dysfunction to host cells

C. Produce specific antibodies against host cells