Clostridium perfringens causes gas gangrene, a serious infection of the muscle tissues that can lead to amputation. Clostridium are Gram-positive endospore-formers and obligate anaerobes that are killed when exposed to oxygen. Which of the following virulence factors would be most helpful to this organism in establishing an infection?

In order to establish a successful infection, a pathogen must arrive at a susceptible site, adhere, invade, acquire nutrients, and grow.

Clostridium perfringens causes gas gangrene, a serious infection of the muscle tissues that can lead to amputation. Clostridium are Gram-positive endospore-formers and obligate anaerobes that are killed when exposed to oxygen. Which of the following virulence factors would be most helpful to this organism in establishing an infection?

An endotoxin

B nuclease, an enzyme that breaks down nucleic acids

C collagenase, an enzyme that destroys collagen, which is a major protein of connective tissues

D a neurotoxin

Which phenotypic assay could be used to determine whether a new Streptococcus spp. is of the phones or viridans group?

hemolytic type after growth on a blood agar plate

product(s) formed during lactose fermentation

catalase assay with H₂O₂

the occurrence of cells being in clusters or as individual cells under a microscope