This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
Methicillin-resistant S. aureus (MRSA) was isolated from 7 patients in a 14-bed intensive care unit. All patients were isolated and the unit closed to any more admissions. Which one of the following reasons best explains these rigorous methods to control MRSA? 
Select and explain. 
A. MRSA is inherently more virulent than other staphylococci, B. The alternative for treatment of MRSA is vancomycin, an expensive and potentially toxic antibiotic, C. MRSA causes toxic shock syndrome, D. MRSA spreads more rapidly from patient to patient than antibiotic-susceptible staphylococci do
B: The alternative for treatment of MRSA is vancomycin, an expensive and potentially toxic antibiotic
Answer: B: The alternative for treatment of MRSA is vancomycin, an expensive and potentially toxic antibiotic 
Explanation: Oxacillin- and methicillinresistant S. aureus (MRSA) has been rapidly increasing in incidence. MRSA and methicillin-sensitive S. aureus (MSSA) coexist in heterologous populations. Treatment of a patient harboring this heterologous population may provide a selective environment for the MRSA. Prior to changing therapy, the susceptibility of the isolate should be determined. Vancomycin has often been used effectively for MRSA, but it is expensive and nephrotoxic. There is no evidence that MRSA is any more virulent or invasive than susceptible strains. Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition