Table 2.
Susceptibility of clinical strains of Gram-negative rods to select quinolones in the presence or absence of PAβN.
| Bacteria (No. of Isolates) | Quinolone a | MICs Range (mg/L) b | No. of Strains c | |
|---|---|---|---|---|
| MH | MH + PAβN | |||
| E. coli (n = 36) | ofloxacin | 1–64 | 0.125–8 | 36 |
| nalidixic acid | 1024 to >2048 | 64–256 | 36 | |
| K. pneumoniae (n = 36) | ofloxacin | 4–32 | 0.25–4 | 36 |
| nalidixic acid | 4 to >2048 | 1–512 | 36 | |
| P. aeruginosa (n = 36) | ofloxacin | 2–128 | 0.063–4 | 36 |
| nalidixic acid | 64–2048 | 1–32 | 36 | |
| S. maltophilia (n = 36) | ofloxacin | 1–8 | 1–8 | 1 |
| nalidixic acid | 4–32 | 1–4 | 36 | |
| A. baumannii (n = 36) | ofloxacin | 8–64 | 4–64 | 5 |
| nalidixic acid | 128–2048 | 32–256 | 36 | |
PAβN, efflux pump inhibitor Phe-Arg-β-naphthylamide; MH, Mueller–Hinton II medium with 1 mM MgSO4. a Antimicrobial agents used to study the influence of non-antibiotics on antibacterial activity against different bacteria species are indicated in boldface; b The correctness of the assay was verified by determining the MIC of antimicrobial agents necessary to inhibit growth of reference strains (E. coli ATCC 25922 and P. aeruginosa ATCC 27853) and comparing with CLSI guidelines: ofloxacin MIC was 0.03 mg/L for E. coli and 2 mg/L for P. aeruginosa, nalidixic acid MIC was 2 mg/L for E. coli and 512 mg/L for P. aeruginosa; c Number of strains with at least 4-fold decrease in MICs in the presence of PAβN.