In-vitro efficacy of quinolones and carbapenems against non-fermenting gram-negative bacteria isolated from clinical specimens received in the Nepalese tertiary care hospital

Ninety-two NFGNB were isolated, predominantly from urine (40.2%, 37/92). The MDR proportion was high in P. aeruginosa [85.7% (18/21) versus 80.28% (57/71)]. The extensively drug-resistant (XDR) proportion was high in the ACB complex [14.1% (10/71) versus 4.8% (1/21)].

The MIC50 in P. aeruginosa against norfloxacin and ofloxacin was ≥8 and ≥0.5 µg/mL, respectively. The MIC50 against ciprofloxacin in P. aeruginosa was ≥8 µg/mL, while it was ≥32 µg/mL in the ACB complex. MIC50 against levofloxacin was ≥0.5 µg/mL in P. aeruginosa, unlike the ACB complex (≥16 µg/mL).

The MIC50 for meropenem was lower in the ACB complex (≥4 vs ≥8 µg/mL) than in P. aeruginosa, while both showed similar MIC90 (≥64 µg/mL). ACB complex showed higher MIC50 against imipenem (≥4 µg/mL) than P. aeruginosa (≥0.125 µg/mL). Over three-fourths of the NFGNB infections were caused by the ACB complex, exhibiting high XDR rates and elevated MICs to quinolones and carbapenems, underscoring the need for strengthened antimicrobial stewardship.