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Maximally precise combinations to overcome metallo-β-lactamase-producing Klebsiella pneumoniae
Jan Naseer Kaur1,2, Jack F Klem1,2, Yang Liu1,2
1Center for Infectious Diseases Next Generation Therapeutics, University at Buffalo, Buffalo, New York, USA.
Abstract:
Gram-negatives harboring metallo-β-lactamases (MBLs) and extended-spectrum β-lactamases (ESBLs) pose a substantial risk to the public health landscape. In ongoing efforts to combat these "superbugs," we explored the clinical combination of aztreonam and ceftazidime/avibactam together with varying dosages of polymyxin B and imipenem against Klebsiella pneumoniae (Kp CDC Nevada) in a 9-day hollow fiber infection model (HFIM). As previously reported by our group, although the base of aztreonam and ceftazidime/avibactam alone leads to 3.34 log10 fold reductions within 72 hours, addition of polymyxin B or imipenem to the base regimen caused maximal killing of 7.55 log10 and 7.4 log10 fold reduction, respectively, by the 72-hour time point. Although low-dose polymyxin B and imipenem enhanced the bactericidal activity as an adjuvant to aztreonam +ceftazidime/avibactam, regrowth to ~9 log10CFU/mL by 216 hours rendered these combinations ineffective. When aztreonam +ceftazidime/avibactam was supplemented with high-dose polymyxin B and or low-dose polymyxin B + imipenem, it resulted in effective long-term clearance of the bacterial population. Time lapse microscopy profiled the emergence of long filamentous cells in response to PBP3 binding due to aztreonam and ceftazidime. The emergence of spheroplasts via imipenem and damage to the outer membrane via polymyxin B was visualized as a mechanism of persister killing. Despite intrinsic mgrB and blaNDM-1 resistance, polymyxin B and β-lactam combinations represent a promising strategy. Future studies using an integrated molecularly precise pharmacodynamic approach are warranted to unravel the mechanistic details to propose optimal antibiotic combinations to combat untreatable, pan-drug-resistant Gram-negatives.
Insights
Combinations of aztreonam, ceftazidime/avibactam, and high-dose polymyxin B or imipenem effectively cleared Klebsiella pneumoniae in an infection model. Lower doses showed initial killing but led to regrowth, highlighting the importance of dose optimization for combating Gram-negative superbugs.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Metallo-β-lactamases (MBLs) and extended-spectrum β-lactamases (ESBLs) in Gram-negative bacteria are a significant public health threat.
- Combating multidrug-resistant Gram-negative infections requires novel therapeutic strategies.
Purpose of the Study:
- To evaluate the efficacy of aztreonam and ceftazidime/avibactam combined with polymyxin B or imipenem against Klebsiella pneumoniae in a hollow fiber infection model.
- To investigate the impact of varying dosages of polymyxin B and imipenem on bacterial killing and long-term clearance.
Main Methods:
- Utilized a 9-day hollow fiber infection model (HFIM) with Klebsiella pneumoniae (Kp CDC Nevada).
- Tested combinations of aztreonam, ceftazidime/avibactam, polymyxin B (varying doses), and imipenem.
- Employed time-lapse microscopy to visualize bacterial responses and mechanisms of killing.
Main Results:
- Aztreonam + ceftazidime/avibactam alone achieved a 3.34 log10 fold reduction in 72 hours.
- Addition of low-dose polymyxin B or imipenem enhanced killing to >7.4 log10 fold reduction by 72 hours but resulted in regrowth by 216 hours.
- High-dose polymyxin B or low-dose polymyxin B + imipenem with aztreonam + ceftazidime/avibactam achieved effective long-term bacterial clearance.
- Microscopy revealed filamentous cells (aztreonam/ceftazidime) and spheroplasts/outer membrane damage (imipenem/polymyxin B) as killing mechanisms.
Conclusions:
- High-dose polymyxin B and specific polymyxin B-imipenem combinations show promise for long-term clearance of MBL/ESBL-producing Gram-negatives.
- Despite intrinsic resistance, these combinations offer a potential strategy against difficult-to-treat Gram-negative infections.
- Further research using molecularly precise pharmacodynamics is needed to optimize antibiotic combinations for pan-drug-resistant Gram-negatives.
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