Micro organism which uses steroids as growth factor is
**Question:** Micro organism which uses steroids as growth factor is
A. Escherichia coli
B. Bacillus subtilis
C. Staphylococcus aureus
D. Pasteurella multocida
**Correct Answer:** D. Pasteurella multocida
**Core Concept:** Steroids are a group of natural hormones produced by the adrenal glands, with diverse physiological effects. Some steroids, like cortisol and aldosterone, are essential for regulating blood pressure, electrolyte balance, and immune response. Steroids also serve as growth factors for some microorganisms.
**Why the Correct Answer is Right:** Pasteurella multocida is a Gram-negative, aerobic, rod-shaped bacterium, commonly found in animals, particularly cats and dogs. It can cause diseases like pneumonia, mastitis, and septicemia. Steroids, particularly corticosteroids, can enhance P. multocida growth by stimulating RNA and protein synthesis, which leads to increased bacterial proliferation.
**Why Each Wrong Option is Incorrect:**
A. Escherichia coli (E. coli) is a Gram-negative, facultatively anaerobic bacterium commonly found in the human gastrointestinal tract. It does not rely on steroids for growth, as it possesses its own enzymes for steroid synthesis.
B. Bacillus subtilis is a Gram-positive, facultatively anaerobic bacterium, commonly found in soil and the gastrointestinal tracts of animals. B. subtilis does not utilize steroids as growth factors, unlike some other bacteria like P. multocida.
C. Staphylococcus aureus is a Gram-positive, facultatively anaerobic bacterium, known for causing various infections in humans and animals. S. aureus does not require steroids for growth, as it can synthesize its own steroids.
**Clinical Pearl:** Steroid-dependent microorganisms are an important consideration in the context of antibiotic therapy. Appropriate antibiotics should be chosen based on the specific microorganism and its dependence on steroids for growth. Infections caused by steroid-dependent organisms may be challenging to treat due to the potential for antibiotic resistance development.