Final answer:
Rifaximin acts by binding to bacterial RNA polymerase to inhibit RNA transcription, making it selectively toxic to bacteria. It is used for travelers' diarrhea caused by E. coli and for preventing hepatic encephalopathy. However, it's not recommended for certain E. coli infections, where other antibiotics might be used.
Step-by-step explanation:
Its primary mechanism of action (MOA) involves the inhibition of bacterial RNA synthesis. Specifically, Rifaximin works by binding to the bacterial RNA polymerase, blocking its activity, and therefore preventing the transcription of RNA. This mechanism is effective because the RNA polymerase enzymes in bacteria have a structure different from those found in eukaryotic cells, which results in selective toxicity against bacterial cells without affecting the human host. Indications for Rifaximin include the treatment of travelers' diarrhea caused by noninvasive strains of Escherichia coli and preventing hepatic encephalopathy, a brain disorder that can occur due to severe liver disease. However, it is not recommended for other types of E. coli such as Enteroinvasive E. coli (EIEC) and Enterohemorrhagic E. coli (EHEC). Instead, other agents like fluoroquinolones or trimethoprim/sulfamethoxazole (TMP/SMZ) may be considered for other E. coli infections like Enterotoxigenic E. coli (ETEC) and Enteropathogenic E. coli (EPEC).