Antibiotic spectrum index

• Measures the spectrum of an antibiotic, with a range from 0 to 14
• One point for activity against each of the following:
  • Methicillin-sensitive Staphylococcus aureus (MSSA)
  • Methicillin-resistant Staphylococcus aureus (MRSA)
  • Enterococcus faecalis
  • Vancomycin-resistant Enterococcus faecalis (VRE)
  • Escherichia coli or Klebsiella
  • AmpC producers (Enterobacter, Serratia, and Citrobacter)
  • Extended-spectrum β-lactamase (ESBL) E. coli/Klebsiella
  • Pseudomonas aeruginosa
  • Penicillin-resistant pneumococcus (PRP)
  • Moraxella and Haemophilus influenzae
  • Mycoplasma and Chlamydophila
  • Anaerobes (in general)
  • Bacteriodes fragilis (specifically)
  • Multidrug-resistant organisms
• For each patient, the number of points for every antibiotic is added to give a total daily ASI

Sample Spectrum Indices

Antibiotic	MSSA	Enterococcus	Anaerobes	Bacteroides	Moraxella/Haemophilus	Escherichia/Klebsiella	AmpC	ESBL	Pseudomonas	MRSA	Pen-R pneumococcus	VRE	Atypical	MDRO	ASI
Dicloxacillin	1	0	0	0	0	0	0	0	0	0	0	0	0	0	1
Oxacillin	1	0	0	0	0	0	0	0	0	0	0	0	0	0	1
Amoxicillin	0	1	0	0	0	1	0	0	0	0	0	0	0	0	2
Ampicillin	0	1	0	0	0	1	0	0	0	0	0	0	0	0	2
Cephalexin	1	0	0	0	0	1	0	0	0	0	0	0	0	0	2
Erythromycin	0	0	0	0	1	0	0	0	0	0	0	0	1	0	2
Erythromycin	0	0	0	0	1	0	0	0	0	0	0	0	1	0	2
Metronidazole	0	0	1	1	0	0	0	0	0	0	0	0	0	0	2
Penicillin	0	1	1	0	0	0	0	0	0	0	0	0	0	0	2
Aztreonam	0	0	0	0	1	1	0	0	1	0	0	0	0	0	3
Cefazolin	1	0	0	0	1	1	0	0	0	0	0	0	0	0	3
Cefdinir	1	0	0	0	1	1	0	0	0	0	0	0	0	0	3
Cefixime	0	0	1	0	1	1	0	0	0	0	0	0	0	0	3
Cefpodoxime	1	0	0	0	1	1	0	0	0	0	0	0	0	0	3
Rifampin	1	0	0	0	1	0	0	0	0	1	0	0	0	0	3
Azithromycin	1	0	1	0	1	0	0	0	0	0	0	0	1	0	4
Cefprozil	1	0	1	0	1	1	0	0	0	0	0	0	0	0	4
Ceftazidime	0	0	1	0	1	1	0	0	1	0	0	0	0	0	4
Cefuroxime	1	0	1	0	1	1	0	0	0	0	0	0	0	0	4
Chloramphenicol	0	0	1	1	1	1	0	0	0	0	0	0	0	0	4
Clarithromycin	1	0	1	0	1	0	0	0	0	0	0	0	1	0	4
Clindamycin	1	0	1	1	0	0	0	0	0	1	0	0	0	0	4
Piperacillin	0	1	1	0	0	1	0	0	1	0	0	0	0	0	4
TMP-SMX	1	0	0	0	1	1	0	0	0	1	0	0	0	0	4
Cefotaxime	1	0	1	0	1	1	0	0	0	0	1	0	0	0	5
Cefoxitin	1	0	1	1	1	1	0	0	0	0	0	0	0	0	5
Ceftriaxone	1	0	1	0	1	1	0	0	0	0	1	0	0	0	5
Colistin	0	0	0	0	0	1	1	1	1	0	0	0	0	1	5
Daptomycin	1	1	0	0	0	0	0	0	0	1	0	1	0	1	5
Doxycycline	1	0	0	0	1	1	0	0	0	1	0	0	1	0	5
Gentamicin	1	0	0	0	1	1	0	0	1	1	0	0	0	0	5
Minocycline	1	0	0	0	1	1	0	0	0	1	0	0	1	0	5
Telavancin	1	1	0	0	0	0	0	0	0	1	1	0	0	1	5
Tobramycin	1	0	0	0	1	1	0	0	1	1	0	0	0	0	5
Vancomycin	1	1	0	0	0	0	0	0	0	1	1	0	0	1	5
Amikacin	1	0	0	0	1	1	0	0	1	1	0	0	0	1	6
Amoxicillin-clavulanic acid	1	1	1	1	1	1	0	0	0	0	0	0	0	0	6
Ampicillin-sulbactam	1	1	1	1	1	1	0	0	0	0	0	0	0	0	6
Cefepime	1	0	0	0	1	1	1	0	1	0	1	0	0	0	6
Linezolid	1	1	0	0	0	0	0	0	0	1	1	1	0	1	6
Ticarcillin-clavulanate	1	0	1	1	1	1	0	0	1	0	0	0	0	0	6
Ceftaroline	1	1	0	0	1	1	1	0	0	1	1	0	0	1	8
Ciprofloxacin	1	1	0	0	1	1	1	1	1	0	0	0	1	0	8
Piperacillin-tazobactam	1	1	1	1	1	1	1	0	1	0	0	0	0	0	8
Ertapenem	1	0	1	1	1	1	1	1	0	0	1	0	0	1	9
Levofloxacin	1	1	1	0	1	1	1	1	0	0	1	0	1	0	9
Meropenem	1	0	1	1	1	1	1	1	1	0	1	0	0	1	10
Moxifloxacin	1	1	1	1	1	1	1	0	0	1	1	0	1	0	10
Imipenem-cilastatin	1	1	1	1	1	1	1	1	1	0	1	0	0	1	11
Tigecycline	1	1	1	1	1	1	1	1	0	1	1	1	1	1	13

Further Reading

• Development and Application of an Antibiotic Spectrum Index for Benchmarking Antibiotic Selection Patterns Across Hospitals. Infect Control Hosp Epidemiol. 2017;38(8):993-997. doi: 10.1017/ice.2017.94.