California Cosmetology Written ExamSafety and Infection ControlEasy
A cosmetology instructor explains that unlike bacteria, this type of pathogen cannot reproduce on its own and must invade a living host cell to multiply. What is this pathogen called?
- AA saprophyte
- BA spore-forming bacillus
- CA nonpathogenic bacterium
- DA virus
Show answer & explanationAnswer & explanation
Correct answer: D. A virus
Viruses are obligate intracellular parasites — they lack the machinery to reproduce independently and must hijack a host cell's reproductive process. Bacteria, by contrast, can reproduce on their own.
Why the other options are wrong
- A. Saprophytes live on dead matter and can reproduce independently.
- B. Bacilli reproduce by cell division without needing a host cell.
- C. Nonpathogenic bacteria still reproduce independently.
Virus
A microscopic pathogen that cannot reproduce outside a living host cell and depends on the host's cellular machinery to multiply.
- Obligate intracellular parasite
- Examples: HIV, Hepatitis B, common cold viruses
- Not killed by antibiotics; requires disinfection/vaccination for control
Memory trick: 'Vampire Virus' needs a host body to live — it can't survive alone.