Combination therapy strategies against multidrug resistant bacteria in vitro and in vivo.

This article focuses on evaluating the antibacterial efficacy of combination therapies against multidrug-resistant (MDR) Gram-negative bacteria isolated from patients with acute exacerbation of chronic obstructive pulmonary disease (COPD). The study tested seven common antibiotics and found that over 70% of isolates exhibited multidrug resistance but remained sensitive to polymyxin B. Using checkerboard assays, the combination of polymyxin B and tetracycline demonstrated significant synergistic effects with fractional inhibitory concentration index values below 0.5, which was further supported by time-kill curve analyses showing a 2–3 log reduction in bacterial counts within 12 hours. In vivo experiments using Galleria mellonella larvae infected with MDR strains confirmed that this combination significantly improved survival rates compared to monotherapies. These findings suggest that polymyxin B and tetracycline combination therapy holds promise as an effective treatment strategy for MDR Gram-negative bacterial infections in COPD patients, warranting further clinical investigation.