Rifaximin is active against Clostridium difficile. Severe allergic reactions and "Clostridium difficile" diarrhea may occasionally occur. Botulinum toxin produced by "Clostridium botulinum" is the cause of botulism. Tetanus is caused by the tetanus bacterium "Clostridium tetani". Infants can develop botulism after consuming honey contaminated with "Clostridium botulinum" endospores. H7 bacteria genetically modified to produce some of the toxins made by "Clostridium perfringens" bacteria. Oritavancin was more active than either metronidazole or vancomycin against strains of "Clostridium difficile" tested. Vancomycin is also recommended by mouth as a treatment for severe "Clostridium difficile" colitis. It is also linked to an increased risk of "Clostridium difficile" colitis. Some studies have shown a correlation between use of PPIs and "Clostridium difficile" infections. The antimicrobial efficacy of various copper alloys against "Clostridium difficile" was recently evaluated. Tolevamer was designed to bind the enterotoxins of "Clostridium difficile". This is typical of "Clostridium tetani". Blackleg is caused by infection with Clostridium bacteria. Endospore formation is limited to several genera of gram-positive bacteria such as "Bacillus" and "Clostridium".