- 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 (atypicals)
- 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
Working Ranking
- The following is a reasonable list of commonly-used antibiotics, order from broadest to narrowest, not based on the ASI
- Cefiderocol, Colistin, Polymyxin B, Meropenem-vaborbactam, Imipenem-relebactam, Ceftazidime-avibactam, Ceftolozane-tazobactam, Tigecycline, Meropenem, Doripenem, Ertapenem, Piperacillin-tazobactam, Ticarcillin-clavulanate, Fosfomycin, Moxifloxacin, Levofloxacin, Ciprofloxacin, Doxycycline, Amikacin, Tobramycin, Gentamicin, Cefipime, Ceftazidime, Trimethoprim-sulfamethoxazole, Ampicillin-sulbactam, Amoxicillin-clavulanate, Ceftaroline, Ceftriaxone, Cefuroxime, Cefazolin, Ampicillin, Amoxicillin
Sample Spectrum Index
| Antibiotic | MSSA | E.faeca | Anaerobes | Bacteroides | M/H.flu | E/K | AmpC | ESBL | Pseudo | MRSA | PRP | VRE | Atypicals | 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 |
MSSA = methicillin-susceptible Staphylococcus aureus; E/K = Escherichia coli/Klebsiella; M/H.flu = Moraxella and Haemophilus influenzae; Pseudo = Pseudomonas aeruginosa; MRSA = methicillin-resistant Staphylococcus aureus; PRP = penicillin-resistant pneumococcus; VRE = vancomycin-resistant Enterococcus; atypicals = Mycoplasma pneumoniae and Chlamidophila; MDRO = multidrug-resistant organisms
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.
