Why should antibiotics be used with caution in suspected STEC infections?

• A. Antibiotics may trigger increased Shiga toxin production and risk of HUS; supportive care is preferred in many cases
• B. Antibiotics reduce risk of HUS but can cause resistance
• C. Antibiotics may cause antibiotic resistance but are always beneficial
• D. Antibiotics have no effect on Shiga toxin production

Answer: (C)

In Shiga toxin–producing E. coli infections, antibiotics are used with caution because they can worsen outcomes by increasing toxin production. The toxin genes are carried on a bacteriophage integrated into the bacterial genome. When certain antibiotics provoke the bacterial SOS response, the phage can be induced to enter the lytic cycle, leading to more Shiga toxin being released. This raises the risk of hemolytic-uremic syndrome, especially in children. Because of this, the usual approach is supportive care—hydration, careful monitoring for signs of HUS, and avoiding antibiotics in suspected STEC infections unless there is another compelling reason to treat a different infection. So, the idea that antibiotics are always beneficial or have no effect on toxin production isn’t correct; antibiotics can actually increase toxin production and worsen outcomes in this setting.