Synergetic Effects of Combined Treatment of Colistin With Meropenem or Amikacin on Carbapenem-Resistant Klebsiella pneumoniae in vitro

Effectiveness of antimicrobial agent combinations against carbapenem-producing Klebsiella pneumoniae with KPC variants in China

Purpose

Carbapenem-resistant Klebsiella pneumoniae (CRKP) producing carbapenemases poses a global threat to public health. Antimicrobial agent combinations have been promoted as a potential therapeutic strategy for infections. The most effective antimicrobial combinations against CRKP strains producing different carbapenemases are currently unclear, particularly those producing the KPC variant carbapenemases. This study is aimed to evaluate the effectiveness of various antimicrobial agent combinations against CRKP strains with different carbapenemases.

Methods

A checkerboard assay involving 24 antimicrobial agent combinations was conducted on 44 strains of carbapenemase-producing CRKP isolated from patients of which 13 CRKP strains carried single KPC variants. The 24 antimicrobial combinations were based on meropenem, polymyxin, tigecycline, ceftazidime/avibactam, respectively. The fractional inhibitory concentration (FIC) indexes were calculated for each combination of antimicrobial agents.

Results

The distribution of carbapenemases in 44 CRKP strains was as follows: KPC variants (n = 13, 29.5%), KPC-2 (n = 10, 22.7%), metallo-β-lactamases (n = 9, 20.5%), OXA-48-like (n = 12, 27.3%). In the checkerboard assay, the combination of polymyxin and aztreonam exhibited the highest synergistic effect against CRKP strains, with a rate of 95.5% (42/44). This was followed by polymyxin-meropenem at 88.6% (39/44) and polymyxin-levofloxacin at 68.2% (30/44). Additionally, polymyxin-aztreonam combination and polymyxin-meropenem showed the highest sum of synergistic and additive rates of 100.0% against KPC variant-producing CRKP strains. Notably, ceftazidime/avibactam-based combinations exhibited better synergistic effects on KPC variant-producing CRKP strains compared to other CRKP strains with adjusted p value <0.05.

Conclusion

Our study suggests that the combinations of antimicrobial agent could serve as potential treatment strategies against CRKP infections. Furthermore, the effectiveness of these combinations is influenced by the types of carbapenemases present. Ceftazidime/avibactam-based combinations have showed superior synergistic effects on KPC variant-producing CRKP strains.

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.

A challenging case of carbapenem resistant Klebsiella pneumoniae-related pyogenic liver abscess with capsular polysaccharide hyperproduction: a case report

BACKGROUND

Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections are a major public health problem, necessitating the administration of polymyxin E (colistin) as a last-line antibiotic. Meanwhile, the mortality rate associated with colistin-resistant K. pneumoniae infections is seriously increasing. On the other hand, importance of administration of carbapenems in promoting colistin resistance in K. pneumoniae is unknown.

CASE PRESENTATION

We report a case of K. pneumoniae-related pyogenic liver abscess in which susceptible K. pneumoniae transformed into carbapenem- and colistin-resistant K. pneumoniae during treatment with imipenem. The case of pyogenic liver abscess was a 50-year-old man with diabetes and liver transplant who was admitted to Abu Ali Sina Hospital in Shiraz. The K. pneumoniae isolate responsible for community-acquired pyogenic liver abscess was isolated and identified. The K. pneumoniae isolate was sensitive to all tested antibiotics except ampicillin in the antimicrobial susceptibility test and was identified as a non-K1/K2 classical K. pneumoniae (cKp) strain. Multilocus sequence typing (MLST) identified the isolate as sequence type 54 (ST54). Based on the patient's request, he was discharged to continue treatment at another center. After two months, he was readmitted due to fever and progressive constitutional symptoms. During treatment with imipenem, the strain acquired blaOXA-48 and showed resistance to carbapenems and was identified as a multidrug resistant (MDR) strain. The minimum inhibitory concentration (MIC) test for colistin was performed by broth microdilution method and the strain was sensitive to colistin (MIC < 2 µg/mL). Meanwhile, on blood agar, the colonies had a sticky consistency and adhered to the culture medium (sticky mucoviscous colonies). Quantitative real-time PCR and biofilm formation assay revealed that the CRKP strain increased capsule wzi gene expression and produced slime in response to imipenem. Finally, K. pneumoniae-related pyogenic liver abscess with resistance to a wide range of antibiotics, including the last-line antibiotics colistin and tigecycline, led to sepsis and death.

CONCLUSIONS

Based on this information, can we have a theoretical hypothesis that imipenem is a promoter of resistance to carbapenems and colistin in K. pneumoniae? This needs more attention.

Synergistic action of 6-gingerol as an adjuvant to colistin for susceptibility enhancement in multidrug-resistant Klebsiella pneumoniae isolates

The growing threat to human health posed by multidrug-resistant Klebsiella pneumoniae (MDR-KP) indicates an urgent need to develop alternative therapeutic options. The emergence of colistin resistance further adds to the complexity. The study aims to explore in silico-screened phytomolecule 6-gingerol, the most potent active constituent of ginger, as an adjuvant to restore sensitivity in MDR-KP isolates to colistin. The screening of phytocompounds of Zingiber officinale were obtained from the spiceRx database, and molecular docking with efflux pump protein AcrB was performed using Schrödinger's Glide program. The synergistic and bactericidal effects of 6-gingerol in combination with colistin against MDR-KP isolates were determined following broth micro-dilution (MIC), checkerboard assay, and time-kill study. 6-Gingerol showed a good binding affinity with AcrB protein (-9.32 kcal mol-1) and followed the Lipinski rule of (RO5), demonstrating favourable drug-like properties. Further, the synergistic interaction of 6-gingerol with colistin observed from checkerboard assays against efflux-mediated colistin resistance MDR-KP isolates reveals it to be a prospectus adjuvant. The time-killing assays showed the effect of 6-gingerol in combination with colistin to be bactericidal against MSK9 and bacteriostatic against MSK4 and MSK7. Overall, the study provides insights into the potential use of 6-gingerol as a safe and easily available natural product to treat multidrug-resistant K. pneumoniae infections combined with colistin but needs in vivo toxicity evaluation before further recommendations can be made.

Combating antimicrobial resistance: the silent war

Once hailed as miraculous solutions, antibiotics no longer hold that status. The excessive use of antibiotics across human healthcare, agriculture, and animal husbandry has given rise to a broad array of multidrug-resistant (MDR) pathogens, posing formidable treatment challenges. Antimicrobial resistance (AMR) has evolved into a pressing global health crisis, linked to elevated mortality rates in the modern medical era. Additionally, the absence of effective antibiotics introduces substantial risks to medical and surgical procedures. The dwindling interest of pharmaceutical industries in developing new antibiotics against MDR pathogens has aggravated the scarcity issue, resulting in an exceedingly limited pipeline of new antibiotics. Given these circumstances, the imperative to devise novel strategies to combat perilous MDR pathogens has become paramount. Contemporary research has unveiled several promising avenues for addressing this challenge. The article provides a comprehensive overview of these innovative therapeutic approaches, highlighting their mechanisms of action, benefits, and drawbacks.

Mechanism for transmission and pathogenesis of carbapenem-resistant Enterobacterales harboring the carbapenemase IMP and clinical countermeasures

Carbapenem-resistant Enterobacterales (CRE) are some of the most important pathogens causing infections, which can be challenging to treat. We identified four blaIMP-carrying CRE isolates and collected clinical data. The transferability and stability of the plasmid were verified by conjugation, successive passaging, and plasmid elimination assays. The IncC blaIMP-4-carrying pIMP4-ECL42 plasmid was successfully transferred into the recipient strain, and the high expression of traD may have facilitated the conjugation transfer of the plasmid. Interestingly, the plasmid showed strong stability in clinical isolates. Whole-genome sequencing was performed on all isolates. We assessed the sequence similarity of blaIMP -harboring plasmid from our institution and compared it to plasmids for which sequence data are publicly available. We found that four blaIMP-carrying CRE belonged to four different sequence types. The checkerboard technique and time-kill assays were used to investigate the best antimicrobial therapies for blaIMP-carrying CRE. The time-kill assay showed that the imipenem of 1× minimum inhibitory concentration (MIC) alone had the bactericidal or bacteriostatic effect against IMP-producing strains at 4-12 h in vitro. Moreover, the combination of tigecycline (0.5/1/2 × MIC) and imipenem (0.5/1 × MIC) showed a bactericidal effect against the blaIMP-26-carrying CRECL60 strain.IMPORTANCECarbapenem-resistant Enterobacterales (CRE) are an urgent public health threat, and infections caused by these microorganisms are often associated with high mortality and limited treatment options. This study aimed to determine the clinical features, molecular characteristics, and plasmid transmissible mechanisms of blaIMP carriage as well as to provide a potential treatment option. Here, we demonstrated that conjugated transfer of the IncC blaIMP-4-carrying plasmid promotes plasmid stability, so inhibition of conjugated transfer and enhanced plasmid loss may be potential ways to suppress the persistence of this plasmid. The imipenem alone or tigecycline-imipenem combination showed a good bactericidal effect against IMP-producing strains. In particular, our study revealed that imipenem alone or tigecycline-imipenem combination may be a potential therapeutic option for patients who are infected with IMP-producing strains. Our study supports further trials of appropriate antibiotics to determine optimal treatment and emphasizes the importance of continued monitoring of IMP-producing strains in the future.

Antibacterial and antibiofilm efficacy of colistin & meropenem conjugated silver nanoparticles against Escherichia coli and Klebsiella pneumoniae

The progressive increase in infections caused by multidrug-resistant (MDR) Gram-negative bacteria and the emergence of resistance to last-resort antimicrobial drugs in recent years necessitate the development of new therapeutic strategies. This study was conducted to obtain nanostructured antimicrobials by conjugating colistin (COL) and meropenem (MEM) antibiotics with biosynthesized silver nanoparticles (bio-AgNPs) via the green synthesis method using Rosa damascena extract, and to investigate the antibacterial and antibiofilm activity of these nanostructures against Escherichia coli and Klebsiella pneumoniae strains. Ultraviolet-visible spectrophotometry, high-resolution-transmission electron microscopy, atomic force microscopy, X-ray diffraction, and Fourier transform-infrared spectroscopy analyses were performed to determine the physical and chemical properties of synthesized bio-AgNPs, COL@bio-AgNPs, MEM@bio-AgNPs, and COL&MEM@bio-AgNPs. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration of nanoparticles were determined on standard and MDR clinical strains. The antibiofilm efficacy and cytotoxic effect of nanoparticles were evaluated by the crystal violet dye method and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide dye method, respectively. The characterization analyses demonstrated that the synthesized nanoparticles had crystal structure and spherical morphology (5.6-30.2 nm in size). Antibiotic conjugated nanoparticles exhibited better antimicrobial activity and lower MIC values (0.125-4 µg/mL) on the tested strains compared to free antibiotics, and MIC values were decreased up to 1024-fold (p < 0.05). Antibiotic conjugated nanoparticles were found to be more effective in biofilm eradication than free antibiotics and bio-AgNPs and had a less inhibitory effect on peripheral blood mononuclear cell viability. The findings revealed that antibiotic-conjugated nanoparticles have the potential to be used as an effective antimicrobial drug against MDR E. coli and K. pneumoniae strains.

In Vitro antibiotic combinations of Colistin, Meropenem, Amikacin, and Amoxicillin/clavulanate against multidrug-resistant Klebsiella pneumonia isolated from patients with ventilator-associated pneumonia

BACKGROUND

Hospital infections such as ventilator-associated pneumonia (VAP) due to multidrug-resistant Klebsiella pneumoniae (MDR-KP) strains have increased worldwide. In addition, biofilm production by these resistant isolates has confronted clinicians with higher treatment failure and infection recurrence. Given the paucity of new agents and limited data on combination therapy for MDR-KPs, the present study sought to evaluate the in vitro activity of several antibiotic combinations against planktonic and biofilm MDR-KPs isolated from patients with VAP.

RESULTS

All 10 carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates demonstrated multidrug resistance against the tested antibiotics. At planktonic mode, combinations of colistin-meropenem and amoxicillin/clavulanate in combination with meropenem, colistin, or amikacin showed synergism against 60-70% isolates. On the other hand, in the biofilm state, colistin-based combinations exhibited synergism against 50-70% isolates and the most effective combination was colistin-amikacin with 70% synergy.

CONCLUSIONS

The results revealed that combinations of amoxicillin/clavulanate with colistin, meropenem, or amikacin in the planktonic mode and colistin with amoxicillin/clavulanate, meropenem, or amikacin in the biofilm mode could effectively inhibit CRKP isolates, and thus could be further explored for the treatment of CRKPs.

Risk factors and clinical outcomes of carbapenem-resistant Klebsiella pneumoniae bacteraemia in children: a retrospective study

OBJECTIVES

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is increasingly being identified in children, but data on the clinical outcomes in this population are limited. This study aimed to characterise the risk factors for 30-day mortality with CRKP bloodstream infection (BSI) in children.

METHODS

A retrospective study was performed from January 2018 to December 2021 at the First Affiliated Hospital of Zhengzhou University. Patients aged < 18 years and with CRKP BSI were included. Multivariable Cox and logistic regression were performed to determine risk factors for death and the development of septic shock following CRKP infection, respectively.

RESULTS

This study identified 33 neonates aged 0-4 weeks and 37 older children. The 30-day mortality rate was 39.4% in neonates and 43.2% in older children. In the neonatal population, a higher Pitt bacteremia score (HR 1.694; 95% CI 1.313-2.186; P < 0.001) was an independent risk factor for 30-day mortality. In the non-neonatal population, higher platelet count (HR 0.990; 95% CI 0.982-0.998; P = 0.010), the use of carbapenems (HR 0.212; 95% CI 0.064-0.702; P = 0.011) and appropriately targeted antimicrobial treatment (HR 0.327; 95% CI 0.111-0.969; P = 0.044) were associated with decreased 30-day mortality. Monocyte count < 0.1 × 109 cells/L (OR 3.615; 95% CI 1.165-11.444; P = 0.026) and a higher Pitt bacteremia score (OR 1.330; 95% CI 1.048-1.688; P = 0.019) were identified as risk factors for the development of septic shock.

CONCLUSIONS

Carbapenem-resistant Klebsiella pneumoniae BSI was associated with high mortality in children. Appropriate antimicrobial treatment is important to improve survival, but more work is needed to assess the efficacy of specific treatment regimens in children.

Carbapenem-Resistant Klebsiella pneumoniae in COVID-19 Era-Challenges and Solutions

The COVID-19 era brought about new medical challenges, which, together with nosocomial bacterial infections, resulted in an enormous burden for the healthcare system. One of the most alarming nosocomial threats was carbapenem-resistant Klebsiella pneumoniae (CRKP). Monitoring CRKP incidence and antimicrobial resistance globally and locally is vitally important. In a retrospective study, the incidence of CRKP in the pre-COVID-19 period (2017-2019) and the COVID-19 pandemic (2020-2022) was investigated in the Central Military Hospital in Ružomberok, Slovak Republic. The relative incidence of CRKP significantly increased during the COVID-19 period-by 4.8 times, from 0.18 to 0.76%. At the same time, 47% of CRKP-positive patients also had COVID-19. Twenty-six KPC and sixty-nine NDM-producing isolates were identified. CRKPs isolated in the year 2022 were submitted to whole genome sequencing, and their susceptibility was tested to cefiderocol, ceftazidime-avibactam, imipenem-relebactam and meropenem-vaborbactam, with excellent results. KPC-producing isolates were also highly susceptible to colistin (92%). The NDM isolates revealed lower susceptibility rates, including only 57% colistin susceptibility. ST-307 prevailed in KPC and ST-11 in NDM isolates. Despite the excellent activity of new antimicrobials, rational antibiotic policy must be thoroughly followed, supported by complementary treatments and strict anti-epidemic precautions.

Aminoglycosides for the Treatment of Severe Infection Due to Resistant Gram-Negative Pathogens

Aminoglycosides are a family of rapidly bactericidal antibiotics that often remain active against resistant Gram-negative bacterial infections. Over the past decade, their use in critically ill patients has been refined; however, due to their renal and cochleovestibular toxicity, their indications in the treatment of sepsis and septic shock have been gradually reduced. This article reviews the spectrum of activity, mode of action, and methods for optimizing the efficacy of aminoglycosides. We discuss the current indications for aminoglycosides, with an emphasis on multidrug-resistant Gram-negative bacteria, such as extended-spectrum β-lactamase-producing Enterobacterales, carbapenemase-producing Enterobacterales, multidrug-resistant Pseudomonas aeruginosa, and carbapenem-resistant Acinetobacter baumannii. Additionally, we review the evidence for the use of nebulized aminoglycosides.

Outbreak report of polymyxin-carbapenem-resistant Klebsiella pneumoniae causing untreatable infections evidenced by synergy tests and bacterial genomes

Polymyxin-carbapenem-resistant Klebsiella pneumoniae (PCR-Kp) with pan (PDR)- or extensively drug-resistant phenotypes has been increasingly described worldwide. Here, we report a PCR-Kp outbreak causing untreatable infections descriptively correlated with bacterial genomes. Hospital-wide surveillance of PCR-Kp was initiated in December-2014, after the first detection of a K. pneumoniae phenotype initially classified as PDR, recovered from close spatiotemporal cases of a sentinel hospital in Rio de Janeiro. Whole-genome sequencing of clinical PCR-Kp was performed to investigate similarities and dissimilarities in phylogeny, resistance and virulence genes, plasmid structures and genetic polymorphisms. A target phenotypic profile was detected in 10% (12/117) of the tested K. pneumoniae complex bacteria recovered from patients (8.5%, 8/94) who had epidemiological links and were involved in intractable infections and death, with combined therapeutic drugs failing to meet synergy. Two resistant bacterial clades belong to the same transmission cluster (ST437) or might have different sources (ST11). The severity of infection was likely related to patients' comorbidities, lack of antimicrobial therapy and predicted bacterial genes related to high resistance, survival, and proliferation. This report contributes to the actual knowledge about the natural history of PCR-Kp infection, while reporting from a time when there were no licensed drugs in the world to treat some of these infections. More studies comparing clinical findings with bacterial genetic markers during clonal spread are needed.

Synergetic dual antibiotics-loaded chitosan/poly (vinyl alcohol) nanofibers with sustained antibacterial delivery for treatment of XDR bacteria-infected wounds

Resistance of bacterial pathogens to conventional antibiotics has remained a significant challenge in managing post-wound infections, especially in developing countries. Here, a nanofibrous chitosan/poly (vinyl alcohol) (CS/PVA) mat was designed for controlled delivery of three different concentrations of two antibiotics (colistin/meropenem ratio of 32/64 μg/ml (AB1), 64/128 μg/ml (AB2), and 128/256 (AB3) μg/ml) with synergistic antibacterial activity against ATCC and extensively drug-resistant (XDR) Acinetobacter baumannii clinical isolates. The scaffolds showed a uniform fibrous structure with no bead formation with a sustained release of the antibiotics for one week. The elongation at break, wettability, porosity, and average fiber diameter decreased with increased antibiotics concentrations. Young's modulus and tensile strength showed a significant increase after adding antibiotics. All the constructs showed excellent in vitro cytocompatibility for fibroblasts and biocompatibility in an animal model. The antibacterial assays confirmed the dose-dependent antibacterial activity of the CS/PVA. The scaffolds loaded with AB2 and AB3 showed biocidal properties against ATCC, while only CS/PVA/AB3 had antibacterial activity against XDR clinical isolates. This study suggests the CS/PVA/AB3 nanofibrous scaffold contained 128/256 μg/ml colistin/meropenem as an excellent antibacterial wound dressing for protection of skin wounds from XDR clinical isolates and now promises to proceed with pre-clinical investigations.

Mortality-Related Risk Factors and Novel Antimicrobial Regimens for Carbapenem-Resistant Enterobacteriaceae Infections: A Systematic Review

OBJECTIVE

Carbapenem-resistant Enterobacteriaceae (CRE) has become a significant public health problem in the last decade. We aimed to explore the risk factors of mortality in patients with CRE infections and to focus on the current evidence on antimicrobial regimens for CRE infections, particularly from the perspective of mortality.

METHODS

A systematic literature review was performed by searching the databases of EMBASE, PubMed, and the Cochrane Library to identify studies that evaluated mortality-related risk factors and antimicrobial regimens for CRE infections published from 2012 to 2022.

RESULTS

In total, 33 and 28 studies were included to analyze risk factors and antibiotic treatment, respectively. The risk factors most frequently reported as significantly associated with CRE mortality were antibiotic use (92.9%; 26/28 studies), comorbidities (88.7%; 23/26 studies), and hospital-related factors (82.8%; 24/29 studies). In 10 studies that did not contain ceftazidime/avibactam (CAZ-AVI) therapy, seven demonstrated significantly lower mortality in combination therapy than in monotherapy. However, 5 of 6 studies identified no substantial difference between CAZ-AVI monotherapy and CAZ-AVI combination therapy. Six studies reported substantially lower mortality in CAZ-AVI regimens than in other regimens.

CONCLUSION

Several risk factors, particularly antibiotic use and patients' comorbidities, are strong risk factors for CRE mortality. The optimal regimen for CRE infections remains controversial. Combination therapy should be considered when carbapenems, colistin, tigecycline, or aminoglycosides are administered. CAZ-AVI appears to be a promising antibiotic for CRE infections. Most importantly, treatment should be individualized according to the source and severity of the disease or other highly related risk factors.

Isothermal microcalorimetry versus checkerboard assay to evaluate in vitro synergism of meropenem-amikacin and meropenem-colistin combinations against multidrug-resistant Gram-negative pathogens

OBJECTIVES

To evaluate the activity of meropenem-amikacin and meropenem-colistin combinations with checkerboard broth microdilution (CKBM) compared to isothermal microcalorimetry (ITMC) assays against a multicentric collection of multidrug-resistant Gram-negative (MDR-GN) clinical isolates, to compare the Fractional inhibitory concentration index (FICI) and time to results of CKBM and ITMC assays.

METHODS

A collection of 333 MDR-GNs showing reduced susceptibility to meropenem (121 Klebsiella pneumoniae, 14 Escherichia coli, 130 Pseudomonas aeruginosa and 68 Acinetobacter baumannii) isolated from different centres (Florence, Madrid, Rotterdam, and Stockholm) was included in the study. The antimicrobial activity of selected combinations was evaluated with CKBM and ITMC. FICI results were interpreted as synergistic/additive and indifferent for values ≤0.5/0.5<x≤1 and >1, respectively. WGS data in a subset of strains was used to evaluate their clonality.

RESULTS

A total of 254 and 286 strains were tested with meropenem-colistin and meropenem-amikacin combinations with ITMC and CKBM, respectively. Synergism/additive effects were observed with 46 strains (20 K. pneumoniae, 4 E. coli, 22 P. aeruginosa) and 20 strains (3 K. pneumoniae, 11 P. aeruginosa and 6 A. baumannii) with meropenem-amikacin and meropenem-colistin combination, respectively, with CKBM. ITMC showed a good concordance with CKBM with 89.5% and 92.2% of cases interpreted within the same FICI category for meropenem-amikacin and meropenem-colistin combinations, respectively. Most of the synergism/additivity effects were detected within 6 hours by ITMC.

CONCLUSIONS

ITMC showed a very good concordance with CKBM against a large collection of MDR-GN and could be implemented for the rapid evaluation of in vitro activity of antimicrobial combinations.

Efficacy of Amikacin and Meropenem on Colistin-Induced Klebsiella pneumoniae Persisters

Colistin-based antibiotic therapies have been recommended for the treatment of multidrug-resistant Klebsiella pneumoniae infections. During colistin treatment, persister cells that tolerate antibiotics may arise. Here we designed an in vitro study to assess the killing activity of colistin, meropenem, and amikacin on colistin-induced K. pneumoniae persisters in comparison with starvation-induced persisters. Colistin-induced persisters were generated under exposure to 10 × minimum inhibitory concentration dose of colistin, whereas starvation-induced persisters were produced by limitation of nutrients. In colistin-induced persisters, amikacin totally inhibited cell growth in 6 hours, whereas 98% of the cell population was inhibited by meropenem, and total eradication with meropenem was observed after 24 hours. Both antibiotics also inhibited metabolic activity >88%. The lack of killing effect under colistin exposure suggested to us that these cells could protect themselves from further colistin stress. There was no significant permeabilization change in the cellular membrane with all antibiotics. There was no killing effect on starvation-induced persister cells with the exposure to all antibiotics. In 6 hours, the metabolic activity of the persisters with meropenem and colistin increased 99% and 40%, respectively, whereas there was no increase with amikacin. The sustained inhibition with amikacin was an important finding for antipersister effect of amikacin. Amikacin had rapid and sustained antipersister activity on colistin-induced persister cells. During the colistin treatment of K. pneumoniae infection, the addition of amikacin to the regimen seems to be an effective approach to prevent a recurrence.

Progress in Alternative Strategies to Combat Antimicrobial Resistance: Focus on Antibiotics

Antibiotic resistance, and, in a broader perspective, antimicrobial resistance (AMR), continues to evolve and spread beyond all boundaries. As a result, infectious diseases have become more challenging or even impossible to treat, leading to an increase in morbidity and mortality. Despite the failure of conventional, traditional antimicrobial therapy, in the past two decades, no novel class of antibiotics has been introduced. Consequently, several novel alternative strategies to combat these (multi-) drug-resistant infectious microorganisms have been identified. The purpose of this review is to gather and consider the strategies that are being applied or proposed as potential alternatives to traditional antibiotics. These strategies include combination therapy, techniques that target the enzymes or proteins responsible for antimicrobial resistance, resistant bacteria, drug delivery systems, physicochemical methods, and unconventional techniques, including the CRISPR-Cas system. These alternative strategies may have the potential to change the treatment of multi-drug-resistant pathogens in human clinical settings.

Comparison of Bleeding Risk Between Colistin-Tigecycline and Colistin-Carbapenem Treatment Regimens: A Retrospective Cohort Study

Background

Antibiotic combination is commonly used to treat multidrug-resistant pathogens. Reports have indicated that tigecycline use is associated with hypofibrinogenemia. However, whether the bleeding risk of tigecycline is higher than that of other antibiotics remains unknown. The aim of this study was to compare the bleeding risk between colistin–tigecycline and colistin–carbapenem treatment.

Methods

This retrospective cohort study enrolled adult patients treated with colistin along with tigecycline or carbapenems (doripenem, imipenem–cilastatin, or meropenem) for ˃72 hours during hospitalization. The primary outcome was major bleeding events, which were determined by a hemoglobin drop of ≥2 g/d and receipt of blood transfusions with whole blood or packed red blood cells. Multivariate logistic regression was applied to determine risk factors for bleeding events.

Results

In total, 106 and 268 patients in the colistin–tigecycline and colistin–carbapenem groups met the criteria for analysis, respectively. The two groups did not differ significantly in demographic data, except for alanine aminotransferase (ALT), serum creatinine (S_Cr) and ulcer disease. The colistin–tigecycline group had a higher ALT, S_Cr and a lower proportion of ulcer disease. Major bleeding events did not differ significantly between the colistin–tigecycline and colistin–carbapenem groups (12.26% vs 9.33%, P = 0.40). Antibiotic duration [OR = 1.06 (1.02–1.11), P=0.007)] and anticoagulant use [OR = 2.16 (1.05–4.42), P=0.04] were associated with major bleeding events.

Conclusion

Colistin–tigecycline treatment was not associated with a higher bleeding risk. Antibiotic duration and concurrent use of anticoagulant were the risk factors of bleeding events.

Emergence of the Coexistence of mcr-1, bla NDM-5, and bla CTX-M-55 in Klebsiella pneumoniae ST485 Clinical Isolates in China

Introduction

Polymyxin resistance caused by the plasmid-mediated mcr-1 gene in gram-negative bacilli poses a huge threat to our health. In recent years, many regions have reported that mcr-1 and β-lactamase genes can coexist in a single strain.

Methods

In this study, 107 nonduplicate Klebsiella pneumoniae (K. pneumoniae) isolates were collected from a tertiary hospital in Jiangxi, China. Antimicrobial susceptibility testing of isolates was performed using gram-negative susceptibility cards on the VITEK system. The minimum inhibitory concentrations (MICs) of polymyxin B was detected using the microdilution broth method. The presence of resistance genes was assessed using polymerase chain reaction (PCR). We subjected isolates to genotyping using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) and analyzed the transferability of plasmids with filter mating and electroporation. Subsequently, whole-genome sequencing was performed for plasmids.

Results

Of the 107 K. pneumoniae isolates, 15 (14.0%) were resistant to polymyxin B. All polymyxin B-resistant isolates harbored at least one of the extended-spectrum β-lactamase genes tested. Only one isolate simultaneously harbored mcr-1, bla_NDM-5, bla_CTX-M-55 , and bla_SHV-27 genes. MLST results showed that 15 carbapenem-resistant K. pneumoniae isolates belonged to five sequence types (STs). PFGE results displayed nine different PFGE clusters. Conjugation and transformation experiments and sequencing analysis showed that the strain had three plasmids, and mcr-1, bla_NDM-5 , and bla_CTX-M-55 were located on different plasmids.

Conclusion

The present study demonstrated for the first time the coexistence of mcr-1, bla_NDM-5 , and bla_CTX-M-55 in a K. pneumoniae ST485 isolate. The three plasmids carrying the mcr-1, bla_NDM-5 , and bla_CTX-M-55 genes can be transmitted in Enterobacteriaceae strains, which may lead to more severe bacterial resistance.

Role of Coptis chinensis in antibiotic susceptibility of carbapenem-resistant Klebsiella pneumoniae

BACKGROUND

The incidence of carbapenem-resistant Klebsiella pneumoniae (CRKP) has rapidly increased. This study aimed to assess the effect of Coptis chinensis and its compounds on the minimal inhibitory concentrations (MICs) of eight antibiotics against CRKP.

METHODS

Cell cultures were used to investigate the effects of C. chinensis and its compounds on the MICs of eight antibiotics against CRKP. The MICs for antibiotics alone and antibiotics with C. chinensis or compounds were measured and compared. Furthermore, the effects of C. chinensis on cell membrane injury and intracellular adenosine triphosphate (ATP) CRKP concentration were also measured. The Mann-Whitney rank-sum test was used to analyze the differences between means.

RESULTS

C. chinensis exhibits a notable MIC bacteriostatic effect at 5 mg/mL on CRKP. A significant MIC reduction against CRKP exists when C. chinensis was added to colistin and colistin-containing two-antibiotic combinations. Moreover, C. chinensis could damage cell membrane integrity and decrease intracellular ATP concentration in CRKP. Thus, C. chinensis exhibits antimicrobial activity superiority with colistin against CRKP. Furthermore, the effects of identified compounds in C. chinensis on the MICs of colistin, four-to eight-, two-to four-, and one-to two-fold reductions were found in ferulic acid, magnoflorine, and jatrorrhizine hydrochloride, respectively. Among these compounds, ferulic acid destroys membrane integrity and decreases intracellular ATP concentration.

CONCLUSION

C. chinensis and ferulic acid can potentiate the antimicrobial activity of colistin and may represent a promising component of combination therapy against CRKP infections in a clinical setting.

Synergistic antibacterial effects of colistin in combination with aminoglycoside, carbapenems, cephalosporins, fluoroquinolones, tetracyclines, fosfomycin, and piperacillin on multidrug resistant Klebsiella pneumoniae isolates

Multidrug resistant Enterobacterales have become a serious global health problem, with extended hospital stay and increased mortality. Antibiotic monotherapy has been reported ineffective against most drug resistant bacteria including Klebsiella pneumoniae, thus encouraging the use of multidrug therapies as an alternative antibacterial strategy. The present works assessed the antibacterial activity of colistin against K. pneumoniae isolates. Resistant isolates were tested against 16 conventional antibiotics alone and in combination with colistin. The results revealed that all colistin resistant isolates demonstrated multidrug resistance against the tested antibiotics except amikacin. At sub-inhibitory concentrations, combinations of colistin with amikacin, or fosfomycin showed synergism against 72.72% (8 of 11 isolates). Colistin with either of gentamicin, meropenem, cefoperazone, cefotaxime, ceftazidime, moxifloxacin, minocycline, or piperacillin exhibited synergism against 81.82% (9 of 11 isolates). Combinations of colistin with either of tobramycin or ciprofloxacin showed synergism against 45.45% (5 in 11 isolates), while combinations of colistin with imipenem or ceftolozane and tazobactam displayed 36.36% (4 of 11 isolates) and 63.64% (7 of 11 isolates) synergism. In addition, combinations of colistin with levofloxacin was synergistic against 90.91% (10 of 11 isolates). The results revealed that combinations of colistin with other antibiotics could effectively inhibit colistin resistant isolates of K. pneumoniae, and thus could be further explore for the treatment of multidrug resistant pathogens.

Colistin and amoxicillin combinatorial exposure alters the human intestinal microbiota and antibiotic resistome in the simulated human intestinal microbiota

Antibiotics treatment could cause the dysbiosis of human intestinal microbiota and antibiotic resistome. Fecal microbiota transplantation (FMT) has been an efficacious treatment to restore the dysbiosis of intestinal microbiota in a variety of intestinal diseases. However, to data, the effect of the combinatorial antibiotic treatment on microbiota, antibiotic resistome and the FMT for restoration affected by combinatorial antibiotic exposure in the human intestinal microbiota remain unclear. In this study, we systematically investigated the effect of the colistin and amoxicillin combinatorial exposure in the simulator of the human intestinal microbial ecosystem (SHIME) and found that this combinatorial exposure significantly altered (p < 0.05) the human intestinal microbiota and antibiotic resistome. The shift of bacterial community and antibiotic resistome could incompletely recovery to baseline by FMT treatment after combinatorial antibiotic exposure. Additionally, the variance of antibiotic resistome was dominantly driven by the bacterial community (41.18%-68.03%) after the combinatorial antibiotic exposure. Overall, this study first to investigate the influence of the colistin and amoxicillin combinatorial exposure on the intestinal microbiota and antibiotic resistome, and assess the FMT recovery in the simulated human intestinal microbiota, which may potentially provide a correct administration of antibiotics and application of FMT in the clinic.

In-vitro synergistic activity of colistin and meropenem against clinical isolates of carbapenem resistant E.coli and Klebsiella pneumoniae by checkerboard method

CONTEXT

The emergence of drug resistant pathogens pose major threat to hospitalized patients as well as to the community associated with increased mortality and morbidity. The treatment of carbapenem resistant enterobacteriaceae, one of the top WHO priority pathogen remains a global issue. Combination therapy with different classes of antibiotics have been tried with the aim to reduce toxicity, to increase the efficacy of the drugs and to reduce resistance. The in-vitro synergy methods have to be carried out to determine whether the combination of those antibiotics are synergistic, antagonistic or additive.

AIMS

We have performed in-vitro synergy testing by checkerboard method for colistin -meropenem combination to determine whether the combination of the two antibiotics were synergistic or antagonistic.

METHODS AND MATERIAL

All the consecutive twenty five blood isolates of Escherichia coli and twenty five blood isolates of Klebsiella pneumoniae which were showing resistance to carbapenems by either disc diffusion or vitek 2 were collected over a period of 6 months and checkerboard method was performed.

STATISTICAL ANALYSIS USED

The reduction of MIC of colisin on combination with meropenem compared to MIC of colistin alone is analyzed by McNemar's chisquare test with the help of software Stata version 14 and p value < 0.05 is considered as significant.

RESULTS

56% of K. pneumoniae showed synergy and 44% showed additive/indifference results. For E. coli 40% showed synergy and 60% showed additive/indifference. None of the isolates of E. coli and K. pneumoniae showed antagonism. There was more than two fold reduction in MIC of colistin (significant) on combining withmeropenem.

CONCLUSIONS

The study results support the combination therapy to treat infections by multi-drug-resistant Klebsiela pneumoniae and Escherichia coli by in-vitro checkerboard testing method which inturn will be helpful for clinicians for judicious use of antimicrobials.

In vitro evaluation of double carbapenem and colistin combinations against OXA-48, NDM carbapenemase-producing colistin-resistant Klebsiella pneumoniae strains

BACKGROUND

Treatment of pandrug-resistant isolates often necessitates combination therapy. Checkerboard synergy and time-killing assay tests were performed to evaluate the benefits of a triple combination with meropenem, ertapenem, and colistin against 10 colistin-resistant K. pneumoniae clinical isolates harboring different β-lactamases. (bla_OXA-48, bla_NDM).

MATERIALS AND METHODS

In this study, ertapenem and meropenem (ERT/MEM), meropenem and colistin (MEM/COL), ertapenem, meropenem and colistin (ERT/MEM/COL) combinations were tested using checkerboard techniques and time-kill assays of each antibiotic alone and in combination against 10 colistin-resistant clinical K. pneumoniae isolates. An analysis of K. pneumoniae isolate B6 using a scanning electron microscope revealed morphologic changes in the cell surface after treatment with each antibiotic both alone and in combination. The whole genome of K. pneumoniae KPNB1 was sequenced using an Ion Torrent PGM sequencer.

RESULTS

According to the checkboard results, synergistic combinations were observed with ertapenem/meropenem (5/10 isolates), meropenem/colistin (7/10) and ertapenem/meropenem/colistin (9/10); no antagonism was observed for all combinations. For the time-kill assay results; synergism and bactericidal effects were observed with meropenem/colistin (10/10) and with ertapenem/meropenem/colistin (10/10) combinations, and an indifference effect was observed with the ertapenem and meropenem (10/10) combination. Strain number 1 was found 100% identical to Klebsiella pneumoniae subsp. pneumoniae HS11286 according to the outcomes of complete genome sequence analysis, and the strain carried the genes bla_OXA-181, bla_CTXM-15, blaNDM, arr-3, aac (6')-Ib-cr, rmtF, and catB1.

CONCLUSION

Using double carbapenem antibiotics with colistin could be a potential alternative to treat colistin and carbapenem-resistant K. pneumoniae. The present study is the first Turkish report of OXA-181-type carbapenemase causing colistin resistance.