Activity of antimicrobial combinations against KPC-2-producing Klebsiella pneumoniae in a rat model and time-kill assay

Combined therapeutic option for NDM-producing Serratia Marcescens - an in vitro study from clinical samples

BACKGROUND

Treating NDM-producing bacteria poses a significant challenge, especially for those bacteria inherently resistant to polymyxin, such as Serratia marcescens, necessitating combined therapies.

OBJECTIVE

To assess in vitro the synergistic effect of different antimicrobial combinations against NDM-producing S. marcescens.

METHODS

Four clinical isolates were tested with various antibiotic combinations: polymyxin, amikacin, meropenem, and aztreonam. Concentrations used were those maximized by pharmacokinetic and pharmacodynamic assessments. Synergy evaluation involved a static macrodilution test followed by a time-kill curve assay.

RESULTS

All four isolates demonstrated resistance according to CLSI and EUCAST standards for the tested antibiotics (polymyxin, amikacin, meropenem, and aztreonam). In the macrodilution synergy test, the combination of aztreonam and amikacin was active in 2 out of 4 isolates within 24 h, and polymyxin with meropenem in only one isolate, despite of intrinsic resistance to polymyxin. However, time-kill curve analysis revealed no synergism or additive effect for combinations with the tested antimicrobials.

CONCLUSION

Combinations of polymyxin, meropenem, aztreonam, and amikacin at doses optimized by pharmacokinetic/pharmacodynamic were insufficient to demonstrate any synergism in NDM-producing S. marcescens isolates in time-kill curves.

Nano-ciprofloxacin/meropenem exhibit bactericidal activity against Gram-negative bacteria and rescue septic rat model

Aim: We hypothesized that simultaneous administration of two antibiotics loaded into a nanopolymer matrix would augment their synergistic bactericidal interaction. Methods: Nanoplatforms of chitosan/Pluronic® loaded with ciprofloxacin/meropenem (CS/Plu-Cip/Mer) were prepared by the ionic gelation method, using Plu at concentrations in the range 0.5-4% w/v. CS/Plu-Cip/Mer was evaluated for antibacterial synergistic activity in vitro and in vivo. Results: CS/Plu-Cip and CS/Plu-Mer with Plu concentrations of 3% w/v and 2% w/v, respectively, exhibited ∼80% encapsulation efficiency. The MICs of pathogens were fourfold to 16-fold lower for CS/Plu-Cip/Mer than for Cip/Mer. Synergy was evidenced for CS/Plu-Cip/Mer with a bactericidal effect (at 1× MIC and sub-MICs), and it significantly decreased bacterial load and rescued infected rats. Conclusion: This study illustrates the ability of CS/Plu nanopolymer to intensify synergy between antibiotics, thereby providing a promising potential to rejuvenate antibiotics considered ineffective against resistant pathogens.

In vitro Synergistic Activity of Ceftazidime-Avibactam in Combination with Aztreonam or Meropenem Against Clinical Enterobacterales Producing blaKPC or blaNDM

Background

It is often challenging to select appropriate combination therapies to treat infections caused by carbapenem-resistant Enterobacterales (CRE) with high-level resistance to carbapenem.

Methods

We investigated the in vitro synergistic activity of ceftazidime-avibactam-, polymyxin- or tigecycline-, and meropenem-based combinations using checkerboard assays against 16 CRE including Klebsiella pneumoniae carrying bla_KPC-2 (CR1-bla_KPC-2) and Enterobacter cloacae carrying bla_NDM-1 (CR2-bla_NDM-1) with meropenem MICs ≥128 mg/L. Time-kill assays were used to observe synergistic bactericidal activity.

Results

Meropenem in combination with ertapenem, amikacin, tigecycline or polymyxin B, and tigecycline plus ceftazidime-avibactam showed weak synergistic activities against CR1-bla_KPC-2 and CR2-bla_NDM-1. Polymyxin B combined with tigecycline or ceftazidime-avibactam, and ceftazidime-avibactam plus amikacin showed synergistic effects against two tigecycline-non-susceptible KPC-producers or three ceftazidime-avibactam-resistant NDM-producer, and 50% (5/10) of strains with amikacin MICs ≥4096 mg/L, respectively. Synergistic interactions of ceftazidime-avibactam plus aztreonam or meropenem in checkerboard assays were measured for 100% (16/16) and 93.8% (15/16) of strains, respectively. The time-kill assay further verified that the ceftazidime-avibactam combination had the potential to restore aztreonam susceptibility and reduced meropenem MICs to 8 mg/L.

Conclusion

Ceftazidime-avibactam plus aztreonam or meropenem could be an effective strategy for treating CRE infections, particularly those with high-level resistance to carbapenems and/or ceftazidime-avibactam.

Luteolin 4'-Neohesperidoside Inhibits Clinically Isolated Resistant Bacteria In Vitro and In Vivo

Multidrug resistance (MDR) pathogens are usually associated with higher morbidity and mortality rates. Flavonoids are good candidates for the development of new potential antimicrobials. This research investigated whether luteolin 4'-neohesperidoside (L4N) has antibacterial and synergistic activities against four antibiotic-resistant pathogens: methicillin-resistant Staphylococcus aureus (MRSA), Klebsiella pneumoniae, fosA-positive shiga toxin producing the Escherichia coli serogroup O111 (STEC O111), and Bacillus cereus. In vitro antimicrobial susceptibility testing revealed highly potent anti-MRSA (MIC of 106.66 ± 6.95 µg/mL), anti-K. pneumoniae (MIC of 53.33 ± 8.47 µg/mL) and anti-STEC O111 (MIC of 26.66 ± 5.23 µg/mL) activities. Significant synergistic combination was clearly noted in the case of gentamycin (GEN) against Gram-negative bacteria. In the case of B. cereus, the combination of vancomycin (VAN) with L4N could efficiently inhibit bacterial growth, despite the pathogen being VAN-resistant (MIC of 213.33 ± 7.9 µg/mL). In vivo evaluation of L4N showed significant decreases in K. pneumoniae and STEC shedding and colonization. Treatment could significantly diminish the levels of pro-inflammatory markers, tumor necrosis factor-alpha (TNF-α), and immunoglobulin (IgM). Additionally, the renal and pulmonary lesions were remarkably enhanced, with a significant decrease in the bacterial loads in the tissues. Finally, this study presents L4N as a potent substitute for traditional antibiotics with anti-STEC O111 and anti-K. pneumoniae potential, a finding which is reported here for the first time.

Bioassay-Guided Isolation of Antimicrobial Components and LC/QToF Profile of Plumeria obtusa: Potential for the Treatment of Antimicrobial Resistance

The methanolic fraction (M-F) of the total extract (TE) of Plumeria obtusa L. aerial parts showed promising antibacterial effects against the MDR (multidrug-resistant) gram-negative pathogens Klebsiella pneumoniae and Escherichia coli O157:H7 [Shiga toxin-producing E. coli (STEC)]. In addition, M-F had a synergistic effect (in combination with vancomycin) against the MDR gram-positive strains MRSA (methicillin-resistant Staphylococcus aureus) and Bacillus cereus. After treating the K. pneumoniae- and STEC-infected mice with M-F (25 mg/kg, i.p.), the level of IgM and TNF-α was decreased and the severity of pathological lesions were reduced better than that observed after administration of gentamycin (33 mg/kg, i.p.). Thirty-seven compounds including 10 plumeria-type iridoids and 18 phenolics, 7 quinoline derivatives, 1 amino acid, and 1 fatty acid were identified in TE using LC/ESI-QToF. Furthermore, five compounds; kaempferol 3-O-rutinoside (M1), quercetin 3-O-rutinoside (M2), glochiflavanoside B (M3), plumieride (M4), and 13-O-caffeoylplumieride (M5) were isolated from M-F. M5 was active against K. pneumoniae (MIC of 64 μg/mL) and STEC (MIC of 32 μg/mL). These findings suggested that M-F and M5 are promising antimicrobial natural products for combating MDR K. pneumoniae and STEC nosocomial infections.

Effect of 2-chloro-N-(4-fluoro-3-nitrophenyl)acetamide in combination with antibacterial drugs against Klebsiella pneumoniae

Klebsiella pneumoniae is a species of Gram-negative bacteria related to a wide range of infections and high rates of drug resistance. The combined use of antibacterial agents is one of the strategies that has been analyzed in recent years as part of the alternatives in the treatment of drug-resistant infections. Recently, the antibacterial activity of of 2-chloro-N-(4-fluoro-3-nitrophenyl)acetamide has been demonstrated against K. pneumoniae, also indicating that this acetamide did not show significant cytotoxic potential in preliminary tests. Thus, it becomes an interesting substance for future studies that explore its antimicrobial capacity, including investigating its association with antibacterial drugs. Based on this, this research aimed to analyze the effects of the association of 2-chloro-N-(4-fluoro-3-nitrophenyl)acetamide (CFA) with ciprofloxacin, cefepime, ceftazidime, meropenem and imipenem against K. pneumoniae strains. The results showed additivity when the substance was combined with ciprofloxacin and cefepime, indifference when associated with ceftazidime and synergistic effect when combined with meropenem and imipenem. Thus, the acetamide was able to optimize the effects of antibacterial drugs, reducing the concentrations necessary to cause bacterial death. These data indicate a potential future clinical use of these combinations, and further studies are needed to analyze this viability.

In vitro research of combination therapy for multidrug-resistant Klebsiella pneumoniae bloodstream infections

Objective

Multidrug-resistant Klebsiella pneumoniae (MDR KP) bloodstream infections are a serious problem. The objective of this study was to investigate the effects of appropriate combination therapies on MDR KP bloodstream infections.

Methods

MDR KP strains isolated from clinical samples were assessed for antibiotic susceptibility using the broth microdilution method. Twenty consecutive MDR KP clinical isolates from patients with bloodstream infections were examined in this study. The experiments were conducted at the Bacterial Laboratory of Tongde Hospital from March to August 2021. Antibiotic combination tests were performed using the minimum inhibitory concentration (MIC) test, and the sum of the fractional inhibitory concentration was used to assess synergy.

Results

Following treatment with a combination of two antibiotic agents, the MIC50 and MIC90 values decreased compared with that before treatment. MIC50 decreased by at least 50%, with one value reduced to 6.25% of the pretreatment value. None of the antibiotic combinations were antagonistic. Combination of polymyxin B with rifampicin or tigecycline had a synergistic effect on 70% and 65% of the strains, respectively.

Conclusions

In vitro combination therapies with two active drug agents (polymyxin B plus rifampicin or tigecycline) had a better effect on MDR KP infections compared with that in other regimens.

Effects of Zinc Oxide Nanoparticles Synthesized Using Aspergillus niger on Carbapenem-Resistant Klebsiella pneumonia In Vitro and In Vivo

Currently, the mortality rate in Saudi Arabia's ICUs is increasing due to the spread of Klebsiella pneumoniae carbapenemase (KPC)-producing bacteria. This study was carried out to evaluate the ability of biologically synthesized zinc oxide nanoparticles (ZnO-NPs) using Aspergillus niger to overcome carbapenem-resistant K. pneumoniae (KPC) in vitro and in vivo. ZnO-NPs were synthesized via a biological method and characterized using UV-Vis spectroscopy, Zetasizer and zeta potential analyses, x-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDX). In vitro sensitivity of KPC to ZnO-NPs was identified using the well diffusion method. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by a macro-dilution method. The morphological alteration of KPC cells after ZnO-NPs treatment was observed by SEM. The in vivo susceptibility of KPC cells to ZnO-NPs ointment was evaluated using wound healing in experimental rats. The chemical characterization findings showed the formation, stability, shape, and size of the synthesized nanoparticles. The MIC and MBC were 0.7 and 1.8 mg/ml, respectively. The in vivo results displayed reduced inflammation and wound re-epithelialization of KPC-infected rats. These findings demonstrated that ZnO-NPs have great potential to be developed as antibacterial agents.

In vitro and in vivo antibacterial activity assays of carvacrol: A candidate for development of innovative treatments against KPC-producing Klebsiella pneumoniae

Dissemination of carbapenem-resistant Klebsiella pneumoniae poses a threat to the successful treatment of bacterial diseases and increases the need for new antibacterial agents development. The objective of this study was to determine the antimicrobial activity of carvacrol against multidrug-resistant K. pneumoniae. Carbapenemase production was detected by MALDI-TOF. The PCR and sequencing showed that the bla_KPC-2,bla_OXA-48, bla_NDM-1, bla_CTX-M-8 genes were present in carbapenem-resistant K. pneumoniae strains. The polymyxin-resistant K. pneumoniae strain exhibited alterations in mgrB gene. The antimicrobial activity of carvacrol was evaluated in vitro using broth microdilution and time-kill methods. For this, carbapenem-resistant K. pneumoniae and polymyxin-resistant strains, were evaluated. The in vitro results showed that carvacrol had antimicrobial activity against all isolates evaluated. The survival curves showed that carvacrol eradicated all of the bacterial cells within 4 h. The antimicrobial effect of carvacrol in vivo was determined using a mouse model of infection with Klebsiella pneumoniae carbapenemase (KPC). The treatment with carvacrol was associated with increased survival, and significantly reduced bacterial load in peritoneal lavage. In addition, groups treated with carvacrol, had a significant reduction in the total numbers of white cell and significantly increased of platelets when compared to the untreated group. In vivo and in vitro studies showed that carvacrol regimens exhibited significant antimicrobial activity against KPC-producing K. pneumoniae, making it an interesting candidate for development of alternative treatments.

Combination versus monotherapy for the treatment of infections due to carbapenem-resistant Enterobacteriaceae

PURPOSE OF REVIEW

Combination therapy is a common strategy for treatment of multidrug resistant infections. Despite the strong twin rationales of improving efficacy and reducing resistance development, the evidence supporting this strategy remains controversial. The aims of this review are to assess the most recent studies supporting the use of combination therapy for treating infections because of carbapenem-resistant Enterobacteriaceae (CRE) and to highlight relevant areas for further research.

RECENT FINDINGS

Evidence supporting the use of combination therapy for the treatment of CRE remains limited to in-vitro experiments and observational studies with considerable risk of bias. Very few antibiotic combinations have been tested in well designed randomized controlled trials, making it difficult to draw general conclusions for clinical practice.

SUMMARY

Further studies are urgently needed to test the most promising synergistic combinations. New drugs potentially active against CRE should also to be tested in studies with adequate sample size and truly representative of the general patient population.

When One Drug Is Not Enough: Context, Methodology, and Future Prospects in Antibacterial Synergy Testing

Antibacterial combinations have long been used to accomplish a variety of therapeutic goals, including prevention of resistance and enhanced antimicrobial activity. In vitro synergy testing methods, including the checkerboard array, the time-kill study, diffusion assays, and pharmacokinetic/pharmacodynamic models, are used commonly in the research setting, but are not routinely performed in the clinical microbiology laboratory because of test complexity and uncertainty about their predictive value for patient outcomes. Optimized synergy testing techniques and better data on the relationship between in vitro results and clinical outcomes are needed to guide the rational use of antimicrobial combinations in the multidrug resistance era.

The "Old" and the "New" Antibiotics for MDR Gram-Negative Pathogens: For Whom, When, and How

The recent expansion of multidrug resistant and pan-drug-resistant pathogens poses significant challenges in the treatment of healthcare associated infections. An important advancement, is a handful of recently launched new antibiotics targeting some of the current most problematic Gram-negative pathogens, namely carbapenem-producing Enterobacteriaceae (CRE) and carbapenem-resistant P. aeruginosa (CRPA). Less options are available against carbapenem-resistant Acinetobacter baumannii (CRAB) and strains producing metallo-beta lactamases (MBL). Ceftazidime-avibactam signaled a turning point in the treatment of KPC and partly OXA- type carbapenemases, whereas meropenem-vaborbactam was added as a potent combination against KPC-producers. Ceftolozane-tazobactam could be seen as an ideal beta-lactam backbone for the treatment of CRPA. Plazomicin, an aminoglycoside with better pharmacokinetics and less toxicity compared to other class members, will cover important proportions of multi-drug resistant pathogens. Eravacycline holds promise in the treatment of infections by CRAB, with a broad spectrum of activity similar to tigecycline, and improved pharmacokinetics. Novel drugs and combinations are not to be considered "panacea" for the ongoing crisis in the therapy of XDR Gram-negative bacteria and colistin will continue to be considered as a fundamental companion drug for the treatment of carbapenem-resistant Enterobacteriaceae (particularly in areas where MBL predominate), for the treatment of CRPA (in many cases being the only in vitro active drug) as well as CRAB. Aminoglycosides are still important companion antibiotics. Finally, fosfomycin as part of combination treatment for CRE infections and P. aeruginosa, deserves a greater attention. Optimal conditions for monotherapy and the "when and how" of combination treatments integrating the novel agents will be discussed.

Antagonistic effect between tigecycline and meropenem: successful management of KPC-producing Klebsiella pneumoniae infection

INTRODUCTION

A woman infected by carbapenem-resistant Klebsiella pneumoniae is reported in this study.

CASE REPORT

Tigecycline and meropenem combination was used, and indeed, in vitro checkerboard synergy test confirmed the antagonism between the two antibiotics. Thus, meropenem was ceased and single high-dose tigecycline was successful against the infection. Subsequent experiments showed that the isolates of the KPC-2-producing K. pneumoniae ST11 clone caused the infection.

CONCLUSION

Therefore, tigecycline and meropenem combination should be used with caution.

Enhancing Whole Phage Therapy and Their Derived Antimicrobial Enzymes through Complex Formulation

The resurgence of research into phage biology and therapy is, in part, due to the increasing need for novel agents to treat multidrug-resistant infections. Despite a long clinical history in Eastern Europe and initial success within the food industry, commercialized phage products have yet to enter other sectors. This relative lack of success is, in part, due to the inherent biological limitations of whole phages. These include (but are not limited to) reaching target sites at sufficiently high concentrations to establish an infection which produces enough progeny phages to reduce the bacterial population in a clinically meaningful manner and the limited host range of some phages. Conversely, parallels can be drawn between antimicrobial enzymes derived from phages and conventional antibiotics. In the current article the biological limitations of whole phage-based therapeutics and their derived antimicrobial enzymes will be discussed. In addition, the ability of more complex formulations to address these issues, in the context of medical and non-medical applications, will also be included.

Synergistic activity of synthetic N-terminal peptide of human lactoferrin in combination with various antibiotics against carbapenem-resistant Klebsiella pneumoniae strains

The spread of multi-drug resistant (MDR) Klebsiella pneumoniae strains producing carbapenemases points to a pressing need for new antibacterial agents. To this end, the in-vitro antibacterial activity of a synthetic N-terminal peptide of human lactoferrin, further referred to as hLF1-11, was evaluated against K. pneumoniae strains harboring different carbapenemase genes (i.e. OXA-48, KPC-2, KPC-3, VIM-1), with different susceptibility to colistin and other antibiotics, alone or in combination with conventional antibiotics (gentamicin, tigecycline, rifampicin, clindamycin, and clarithromycin). An antimicrobial peptide susceptibility assay was used to assess the bactericidal activity of hLF1-11 against the different K. pneumoniae strains tested. The synergistic activity was evaluated by a checkerboard titration method, and the fractional inhibitory concentration (FIC) index was calculated for the various combinations. hLF1-11 was more efficient in killing a K. pneumoniae strain susceptible to most antimicrobials (including colistin) than a colistin-susceptible strain and a colistin-resistant MDR K. pneumoniae strain. In addition, hLF1-11 exhibited a synergistic effect with the tested antibiotics against MDR K. pneumoniae strains. The results of this study indicate that resistance to hLF1-11 and colistin are not strictly associated, and suggest an hLF1-11-induced sensitizing effect of K. pneumoniae to antibiotics, especially to hydrophobic antibiotics, which are normally not effective on Gram-negative bacteria. Altogether, these data indicate that hLF1-11 in combination with antibiotics is a promising candidate to treat infections caused by MDR-K. pneumoniae strains.

Strategies for the treatment of polymyxin B-resistant Acinetobacter baumannii infections

In this study, the activity of meropenem (MEM), fosfomycin (FOF) and polymyxin B (PMB), alone and in combination, was analysed. In addition, optimisation of the pharmacodynamic index of MEM and FOF against six isolates of OXA-23-producing Acinetobacter baumannii (including three resistant to PMB) that were not clonally related was assessed. Antimicrobial combinations were evaluated by chequerboard analysis and were considered synergistic when the fractional inhibitory concentration index (FICI) was ≤0.5. Pharmacodynamic analyses of the MEM and FOF dosing schemes were performed by Monte Carlo simulation. The target pharmacodynamic index (%ƒT>MIC) for MEM and FOF was ≥40% and ≥70%, respectively, and a probability of target attainment (PTA) ≥0.9 was considered adequate. Among the PMB-resistant isolates, combinations of PMB+MEM and PMB+FOF+MEM showed the highest synergistic activity (FICI ≤0.125); isolates that were previously PMB-resistant were included in the susceptible category using CLSI interpretive criteria. Pharmacodynamic evaluation found that for a FOF minimum inhibitory concentration (MIC) of ≤16μg/mL, treatment both by bolus dosing and prolonged infusion achieved adequate PTA, whilst for MIC=32μg/mL only infusion achieved adequate PTA. For a MEM MIC of 4μg/mL, only the bolus treatment scheme with 1.5g q6h and the infusion schemes with 1.0g q8h, 1.5g q6h and 2.0g q8h achieved PTA ≥0.9. Results of antimicrobial and pharmacodynamic analyses can assist in treating infections caused by multidrug-resistant A. baumannii. However, in vivo clinical studies are essential to evaluate the true role of these compounds, including intravenous antimicrobial FOF therapy.

Polymyxin B in Combination with Rifampin and Meropenem against Polymyxin B-Resistant KPC-Producing Klebsiella pneumoniae

Safe and effective therapies are urgently needed to treat polymyxin-resistant KPC-producing Klebsiella pneumoniae infections and suppress the emergence of resistance. We investigated the pharmacodynamics of polymyxin B, rifampin, and meropenem alone and as polymyxin B-based double and triple combinations against KPC-producing K. pneumoniae isolates. The rates and extents of killing with polymyxin B (1 to 128 mg/liter), rifampin (2 to 16 mg/liter), and meropenem (10 to 120 mg/liter) were evaluated against polymyxin B-susceptible (PB^s) and polymyxin B-resistant (PB^r) clinical isolates using 48-h static time-kill studies. Additionally, humanized triple-drug regimens of polymyxin B (concentration at steady state [C_ss] values of 0.5, 1, and 2 mg/liter), 600 mg rifampin every 12 or 8 h, and 1 or 2 g meropenem every 8 h dosed as an extended 3-h infusion were simulated over 48 h by using a one-compartment in vitro dynamic infection model. Serial bacterial counts were performed to quantify the pharmacodynamic effect. Population analysis profiles (PAPs) were used to assess the emergence of polymyxin B resistance. Monotherapy was ineffective against both isolates. Polymyxin B with rifampin demonstrated early bactericidal activity against the PB^s isolate, followed by regrowth by 48 h. Bactericidal activity was sustained at all polymyxin B concentrations of ≥2 mg/liter in combination with meropenem. No two-drug combinations were effective against the PB^r isolate, but all simulated triple-drug regimens showed early bactericidal activity against both strains by 8 h that was sustained over 48 h. PAPs did not reveal the emergence of resistant subpopulations. The triple-drug combination of polymyxin B, rifampin, and meropenem may be a viable consideration for the treatment of PB^r KPC-producing K. pneumoniae infections. Further investigation is warranted to optimize triple-combination therapy.

The rapid spread of carbapenem-resistant Enterobacteriaceae

Carbapenems, our one-time silver bullet for multidrug resistant bacterial infections, are now threatened by widespread dissemination of carbapenem-resistant Enterobacteriaceae (CRE). Successful expansion of Enterobacteriaceae clonal groups and frequent horizontal gene transfer of carbapenemase expressing plasmids are causing increasing carbapenem resistance. Recent advances in genetic and phenotypic detection facilitate global surveillance of CRE diversity and prevalence. In particular, whole genome sequencing enabled efficient tracking, annotation, and study of genetic elements colocalized with carbapenemase genes on chromosomes and on plasmids. Improved characterization helps detail the co-occurrence of other antibiotic resistance genes in CRE isolates and helps identify pan-drug resistance mechanisms. The novel β-lactamase inhibitor, avibactam, combined with ceftazidime or aztreonam, is a promising CRE treatment compared to current colistin or tigecycline regimens. To halt increasing CRE-associated morbidity and mortality, we must continue quality, cooperative monitoring and urgently investigate novel treatments.

Global Dissemination of Carbapenemase-Producing Klebsiella pneumoniae: Epidemiology, Genetic Context, Treatment Options, and Detection Methods

The emergence of carbapenem-resistant Gram-negative pathogens poses a serious threat to public health worldwide. In particular, the increasing prevalence of carbapenem-resistant Klebsiella pneumoniae is a major source of concern. K. pneumoniae carbapenemases (KPCs) and carbapenemases of the oxacillinase-48 (OXA-48) type have been reported worldwide. New Delhi metallo-β-lactamase (NDM) carbapenemases were originally identified in Sweden in 2008 and have spread worldwide rapidly. In this review, we summarize the epidemiology of K. pneumoniae producing three carbapenemases (KPCs, NDMs, and OXA-48-like). Although the prevalence of each resistant strain varies geographically, K. pneumoniae producing KPCs, NDMs, and OXA-48-like carbapenemases have become rapidly disseminated. In addition, we used recently published molecular and genetic studies to analyze the mechanisms by which these three carbapenemases, and major K. pneumoniae clones, such as ST258 and ST11, have become globally prevalent. Because carbapenemase-producing K. pneumoniae are often resistant to most β-lactam antibiotics and many other non-β-lactam molecules, the therapeutic options available to treat infection with these strains are limited to colistin, polymyxin B, fosfomycin, tigecycline, and selected aminoglycosides. Although, combination therapy has been recommended for the treatment of severe carbapenemase-producing K. pneumoniae infections, the clinical evidence for this strategy is currently limited, and more accurate randomized controlled trials will be required to establish the most effective treatment regimen. Moreover, because rapid and accurate identification of the carbapenemase type found in K. pneumoniae may be difficult to achieve through phenotypic antibiotic susceptibility tests, novel molecular detection techniques are currently being developed.