Final answer:
Group A Streptococcus (S. pyogenes) is the most common cause of necrotizing fasciitis, with other bacteria also capable of causing the condition. Treatment is complicated by antibiotic resistance and the nature of the infection which limits the effectiveness of antibiotics.
Step-by-step explanation:
The microbe responsible for causing necrotizing fasciitis is most commonly the bacterium Group A Streptococcus (S. pyogenes), although other bacteria such as Klebsiella, Clostridium, Escherichia coli, Staphylococcus aureus, and Aeromonas hydrophila can also cause this rare but potentially fatal condition. The infection involves the fascia, a connective tissue between the skin and muscle, and can spread rapidly, often requiring aggressive treatment, including debridement or amputation of infected tissue, as well as intravenous antibiotics.
Antibiotic resistance is a complicating factor in treating necrotizing fasciitis, especially with methicillin-resistant S. aureus (MRSA). Factors such as the genetically encoded bacterial toxins that limit blood flow and the effectiveness of intravenous antibiotics exacerbate this issue. Moreover, horizontal gene transfer can spread resistance among bacteria, making treatment more challenging.