Why is a low infectious dose a notable feature for Shigella and Campylobacter infections?

Why is a low infectious dose a notable feature for Shigella and Campylobacter infections?

• A. Small inoculum suffices to cause disease, enabling rapid person-to-person spread and outbreaks
• B. Large inoculum is required for disease
• C. Only affects immunocompromised individuals
• D. They are resistant to environmental stress

Answer: (A)

Infectious dose is the number of organisms required to establish an infection. For Shigella and Campylobacter, only a tiny number of bacteria can start disease, so contamination that would be minor or easily overlooked can still cause illness. This means transmission can occur quickly through everyday routes like contaminated food, water, or close person-to-person contact, leading to rapid outbreaks. Shigella, in particular, spreads efficiently via the fecal-oral route, so a small inoculum can seed infection in new hosts and drive rapid spread in settings such as households or daycare centers. Campylobacter can cause illness from relatively small exposures, often linked to undercooked poultry or unpasteurized products, contributing to both sporadic cases and outbreaks. The notion that a large amount of bacteria is needed isn’t accurate here, and these pathogens can affect healthy individuals, not just the immunocompromised. Environmental resistance helps survival outside the host but doesn’t define why a low dose drives transmission.

Infectious dose is the number of organisms required to establish an infection. For Shigella and Campylobacter, only a tiny number of bacteria can start disease, so contamination that would be minor or easily overlooked can still cause illness. This means transmission can occur quickly through everyday routes like contaminated food, water, or close person-to-person contact, leading to rapid outbreaks. Shigella, in particular, spreads efficiently via the fecal-oral route, so a small inoculum can seed infection in new hosts and drive rapid spread in settings such as households or daycare centers. Campylobacter can cause illness from relatively small exposures, often linked to undercooked poultry or unpasteurized products, contributing to both sporadic cases and outbreaks. The notion that a large amount of bacteria is needed isn’t accurate here, and these pathogens can affect healthy individuals, not just the immunocompromised. Environmental resistance helps survival outside the host but doesn’t define why a low dose drives transmission.