No diagnostic testing or treatment required
Consider discontinuing offending antibiotics
Vancomycin 125 mg PO four times daily for 10 days
Fidaxomicin 200 mg PO two times daily for 10 days
Metronidazole 500mg PO or IV four times daily for 10 days (third line therapy)
Vancomycin 125 mg PO four times daily for 10 days
Fidaxomicin 200 mg PO two times daily for 10 days
See criteria above (Evaluation section)
Vancomycin 500 mg PO or NG four times daily for 10 days
Considered rectal instillation of Vancomycin
Metronidazole 500 mg IV every 8 hours, particularly if ileus is present.
Consider emergency colectomy if:
WBC >20K
Lactate >5
Age >75
Immunosuppression
Toxic megacolon
Colonic perforation
Multi-organ system failure
WBC >20K
Lactate >5
Age >75
Immunosuppression
Toxic megacolon
Colonic perforation
Multi-organ system failure
Relapse occurs in 10-25% of patients
Occurs <=4 weeks after the completion of therapy
Otherwise consider other (more common) causes
1st recurrence: same agent  as used to treat initial episode (antimicrobial resistance is not clinically problematic)
2nd recurrence: tapered vancomycin with pulse doses
3rd recurrence: PO vancomycin 10-14 days followed immediately by rifaximin "chaser" 400mg TID x20 days 
Other options:
IVIG
Fecal transplant
Fidaxomicin 200mg BID x10 days noninferior to PO vancomycin, and reduces recurrences at 4 weeks after treatment (~15% vs 25%) 
Otherwise consider other (more common) causes
IVIG
Fecal transplant
Fidaxomicin 200mg BID x10 days noninferior to PO vancomycin, and reduces recurrences at 4 weeks after treatment (~15% vs 25%)
Clostridium difficile
Viral 
Salmonella
Bacterial
Campylobacter jejuni
Campylobacter
Yersinia enterocolitica
Shigella