A periodontal infection caused by Porphyromonas gingivalis persists despite the presence of complement proteins in gingival crevicular fluid. The bacterium secretes a cysteine protease that degrades complement components. Which outcome is most directly associated with this immune evasion strategy?

A child is diagnosed with whooping cough caused by Bordetella pertussis. The bacterium adheres tightly to ciliated respiratory epithelial cells using a surface protein called filamentous hemagglutinin (FHA), which binds to β1-integrins on the host cell surface.

FHA is best described as which type of bacterial structure?

A hospitalised patient develops pneumonia caused by Klebsiella pneumoniae. Microscopic examination of the patient’s K. pneumoniae isolate reveals a prominent capsule surrounding each bacterial cell.

Which of the following best explains how the capsule contributes to bacterial pathogenesis?

A Klebsiella pneumoniae isolate contains a plasmid carrying a gene encoding a fimbrial adhesin that enhances bacterial attachment to urinary tract epithelial cells. This gene is flanked by insertion sequences and genetic analysis shows it was originally located on the K. pneumoniae chromosome.

Which process most likely contributed to the movement of this gene onto the plasmid?

A strain of E. coli becomes resistant to ampicillin after acquiring a circular piece of DNA that replicates independently of the bacterial chromosome and carries a β-lactamase gene.

What type of mobile genetic element is most likely responsible for this resistance?

A Shigella flexneri isolate is found to carry a new gene encoding a type III secretion system effector protein. The gene was acquired via transduction.

Which statement best describes the process by which this gene was acquired?

A bacterial pathogen is inhaled and establishes an infection in the lungs. There, the bacterium produces hyaluronidase, a virulence factor that breaks down components of the extracellular matrix allowing the bacterium to breach tissue barriers and enter the bloodstream. Which stage of bacterial pathogenesis does this virulence factor primarily contribute to?

Lactobacillus species, which are part of the normal vaginal microbiota, are identified in a vaginal swab from a healthy individual with no signs or symptoms of disease.

Select the correct statement:

Which of the following factors contribute to the emergence and re-emergence of infectious diseases? (select all that apply)

Which of the following infectious diseases were among the top ten global causes of death in 2021, according to the World Health Organization? (select all that apply)