Table 2.

Antimicrobial treatment recommendations for appendicitis and extra-biliary IAIs in adults.

Guideline	Indication	Treatment
SIS-IDSA [2]	Community-acquired IAIs of mild-moderate severity including perforated or abscessed appendicitis	Single agent ▪Cefoxitin ▪Ertapenem ▪Moxifloxacin ▪Tigecycline ▪Ticarcillin-clavulanic acid
	Community-acquired IAIs of high risk or severity a
	Hospital-acquired IAIs
WSES [3]	Community-acquired extra-biliary IAIs	Stable, non-critical patients with no risk factors for ESBL pathogens b ▪Amoxcillin-clavulanate IV ▪Ciprofloxacin plus metronidazole
		Stable, non-critical patients with risk factors for ESBL pathogens b ▪Ertapenem ▪Tigecycline
		Critically ill patients with no risk factors for ESBL pathogens b ▪Piperacillin-tazobactam
	Hospital-acquired extra-biliary IAIs	Stable, non-critical patients with risk factors for MDR pathogens c ▪Piperacillin plus tigecycline plus fluconazole
		Critically ill patients with risk factors for MDR pathogens c ▪Piperacillin plus tigecycline plus echinocandin ▪[Imipenem-cilastatin, meropenem or doripenem] plus teicoplanin plus echinocandin

SIS-IDSA: Surgical Infection Society and the Infectious Diseases Society of America; WSES: World Society of Emergency Surgery; Echinocandins: anidulafungin, caspofungin or micafungin; VRE: vancomycin-resistant enterococci; MRSA: methicillin-resistant Staphylococcus aureus. ^a High risk or severity includes delay in initial intervention for >24 h, APACHE II score ≥15, advanced age, comorbidity and organ dysfunction, low albumin level, poor nutritional status, degree of peritoneal involvement or diffuse peritonitis, inability to achieve source control, presence of malignancy. ^b Risk factors for ESBL pathogens include prior exposure to antibiotics (especially third generation cephalosporins), serious comorbid conditions requiring concurrent antibiotic therapy, residence in a long-term care facility, recent hospitalization, advanced age >65 years. ^c Risk factors for MDR pathogens include nosocomial-acquired infections and prior exposure to antibiotics.