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Synergistic killing of NDM-producing MDR Klebsiella pneumoniae by two 'old' antibiotics-polymyxin B and chloramphenicol.

ABSTRACT: Combination therapy is an important option in the fight against Gram-negative 'superbugs'. This study systematically investigated bacterial killing and the emergence of polymyxin resistance with polymyxin B and chloramphenicol combinations used against New Delhi metallo-?-lactamase (NDM)-producing MDR Klebsiella pneumoniae.Four NDM-producing K. pneumoniae strains were employed. The presence of genes conferring resistance to chloramphenicol was examined by PCR. Time-kill studies (inocula ?10(6) cfu/mL) were conducted using various clinically achievable concentrations of each antibiotic (range: polymyxin B, 0.5-2 mg/L; chloramphenicol, 4-32 mg/L), with real-time population analysis profiles documented at baseline and 24 h. The microbiological response was examined using the log change method and pharmacodynamic modelling in conjunction with scanning electron microscopy (SEM).Multiple genes coding for efflux pumps involved in chloramphenicol resistance were present in all strains. Polymyxin B monotherapy at all concentrations produced rapid bacterial killing followed by rapid regrowth with the emergence of polymyxin resistance; chloramphenicol monotherapy was largely ineffective. Combination therapy significantly delayed regrowth, with synergy observed in 25 out of 28 cases at both 6 and 24 h; at 24 h, no viable bacterial cells were detected in 15 out of 28 cases with various combinations across all strains. No polymyxin-resistant bacteria were detected with combination therapy. These results were supported by pharmacodynamic modelling. SEM revealed significant morphological changes following treatment with polymyxin B both alone and in combination.The combination of polymyxin B and chloramphenicol used against NDM-producing MDR K. pneumoniae substantially enhanced bacterial killing and suppressed the emergence of polymyxin resistance.

SUBMITTER: Abdul Rahim N

PROVIDER: S-EPMC4635649 | biostudies-literature | 2015 Sep

REPOSITORIES: biostudies-literature

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Synergistic killing of NDM-producing MDR Klebsiella pneumoniae by two 'old' antibiotics-polymyxin B and chloramphenicol.

Abdul Rahim Nusaibah N Cheah Soon-Ee SE Johnson Matthew D MD Yu Heidi H Sidjabat Hanna E HE Boyce John J Butler Mark S MS Cooper Matthew A MA Fu Jing J Paterson David L DL Nation Roger L RL Bergen Phillip J PJ Velkov Tony T Li Jian J

The Journal of antimicrobial chemotherapy 20150528 9

<h4>Objectives</h4>Combination therapy is an important option in the fight against Gram-negative 'superbugs'. This study systematically investigated bacterial killing and the emergence of polymyxin resistance with polymyxin B and chloramphenicol combinations used against New Delhi metallo-β-lactamase (NDM)-producing MDR Klebsiella pneumoniae.<h4>Methods</h4>Four NDM-producing K. pneumoniae strains were employed. The presence of genes conferring resistance to chloramphenicol was examined by PCR. ...[more]

PMID: 26023209

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Project description:The emergence and spread of polymyxin resistance, especially among Klebsiella pneumoniae isolates, threaten the effective management of infections. This study profiled for polymyxin resistance mechanisms and investigated the activity of polymyxins plus vancomycin against carbapenem- and polymyxin-resistant K. pneumoniae. The entire genome sequences of seven isolates were profiled for resistance and virulence determinants. The effects of combination therapy were evaluated using the checkerboard technique, time-kill assay, and population profile analysis. Protein profiles of the isolates treated with monotherapy were compared to that of combination therapy. The whole-genome sequencing data revealed that the isolates harbored β-lactams, carbapenems, aminoglycoside, fluoroquinolones, macrolides, and tetracycline resistance genes, with several virulence-associated genes. The plasmids including the bla OXA-232-bearing ColKP3 plasmid were also identified in our isolates. Profiling for polymyxin resistance mechanism revealed a missense mutation in the crrB gene that resulted in a Q180L variant that conferred a deleterious effect on protein function. The combination assay indicated fractional inhibitory concentration index ranging from 0.31 to 1.13, whereas the time-kill assay demonstrated synergistic log reduction in colony-forming units per milliliter. Furthermore, population analysis profiling using dual antibiotics indicated enhancement in bacterial log reduction at lower antibiotics concentrations, compared to higher concentrations of single polymyxins. For protein profiling, 796 proteins were identified, and 56 and 94 of them were increased and decreased in the combined drug treatment groups, respectively, while other differentially produced proteins were detected in all treatment groups, except for the control group. The results demonstrated that the vancomycin combination might benefit the antimicrobial activities of polymyxins. IMPORTANCE This study provides insights into the mechanisms of polymyxin resistance in K. pneumoniae clinical isolates and demonstrates potential strategies of polymyxin and vancomycin combinations for combating this resistance. We also identified possible mechanisms that might be associated with the treatment of these combinations against carbapenem- and polymyxin-resistant K. pneumoniae clinical isolates. The findings have significant implications for the development of alternative therapies and the effective management of infections caused by these pathogens.

Project description:Resistance to polymyxin antibiotics is increasing. Without new antibiotic classes, combination therapy is often required. We systematically investigated bacterial killing with polymyxin-based combinations against multidrug-resistant (including polymyxin-resistant), carbapenemase-producing Klebsiella pneumoniae Monotherapies and double- and triple-combination therapies were compared to identify the most efficacious treatment using static time-kill studies (24 h, six isolates), an in vitro pharmacokinetic/pharmacodynamic model (IVM; 48 h, two isolates), and the mouse thigh infection model (24 h, six isolates). In static time-kill studies, all monotherapies (polymyxin B, rifampin, amikacin, meropenem, or minocycline) were ineffective. Initial bacterial killing was enhanced with various polymyxin B-containing double combinations; however, substantial regrowth occurred in most cases by 24 h. Most polymyxin B-containing triple combinations provided greater and more sustained killing than double combinations. Standard dosage regimens of polymyxin B (2.5?mg/kg of body weight/day), rifampin (600?mg every 12 h), and amikacin (7.5?mg/kg every 12 h) were simulated in the IVM. Against isolate ATH 16, no viable bacteria were detected across 5 to 25 h with triple therapy, with regrowth to ?2-log10 CFU/ml occurring at 48 h. Against isolate BD 32, rapid initial killing of ?3.5-log10 CFU/ml at 5 h was followed by a slow decline to ?2-log10 CFU/ml at 48 h. In infected mice, polymyxin B monotherapy (60?mg/kg/day) generally was ineffective. With triple therapy (polymyxin B at 60?mg/kg/day, rifampin at 120?mg/kg/day, and amikacin at 300?mg/kg/day), at 24 h there was an ?1.7-log10 CFU/thigh reduction compared to the starting inoculum for all six isolates. Our results demonstrate that the polymyxin B-rifampin-amikacin combination significantly enhanced in vitro and in vivo bacterial killing, providing important information for the optimization of polymyxin-based combinations in patients.

Dataset Information

Synergistic killing of NDM-producing MDR Klebsiella pneumoniae by two 'old' antibiotics-polymyxin B and chloramphenicol.

Publications

Synergistic killing of NDM-producing MDR Klebsiella pneumoniae by two 'old' antibiotics-polymyxin B and chloramphenicol.

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