Which of the following microorganisms is known to grow inside macrophages?

• A. Mycobacterium tuberculosis
• B. Vibrio cholerae
• C. Escherichia coli
• D. Streptococcus pyogenes

Answer: (A)

Verified step by step guidance

1. Understand the role of macrophages: Macrophages are immune cells that engulf and destroy pathogens through phagocytosis. Some microorganisms have evolved mechanisms to survive and even replicate inside macrophages, evading the immune response.
2. Review the characteristics of each microorganism listed: Vibrio cholerae is primarily an extracellular pathogen causing cholera; Escherichia coli is mostly extracellular but some strains can invade cells; Streptococcus pyogenes is generally extracellular and causes infections like strep throat.
3. Focus on Mycobacterium tuberculosis: This bacterium is well-known for its ability to survive and multiply inside macrophages by preventing the fusion of phagosomes with lysosomes, thus avoiding destruction.
4. Compare the intracellular survival strategies: Among the options, only Mycobacterium tuberculosis has the specialized mechanisms to grow inside macrophages, making it unique in this context.
5. Conclude that the microorganism known to grow inside macrophages is Mycobacterium tuberculosis based on its pathogenic strategy and ability to evade macrophage killing.