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

Non-fermenting Gram-negative bacteria (NFGNB) pose a significant public
health threat due to multidrug resistance (MDR) mediated by biofilms,
efflux pumps, and carbapenemases. This cross-sectional study evaluated the
minimum inhibitory concentrations (MICs) of quinolones and carbapenems
against the Acinetobacter calcoaceticus–baumannii (ACB) complex and
Pseudomonas aeruginosa isolated from clinical specimens at the Nepal Armed
Police Force Hospital, Balambu, Kathmandu, Nepal. These NFGNB were
isolated and identified using standard microbiological methods. Quinolone-
and carbapenem-resistant isolates, screened by disc diffusion, were tested
for MICs of quinolones and carbapenems using broth microdilution.
Statistical analyses were performed in SPSS 17.0. 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.