scholarly journals In vitro analysis of colistin-carbapenem combination activity against Acinetobacter spp infection

2018 ◽  
Vol 12 (02.1) ◽  
pp. 11S ◽  
Author(s):  
Micheline Soudeiha ◽  
Elie S Sokhn ◽  
Ziad Daoud ◽  
Dolla Sarkis
Keyword(s):  
Medical Center ◽  
Pcr Amplification ◽  
Carbapenem Resistance ◽  
Antagonistic Effect ◽  
Amplification Method ◽  
Carbapenem Resistant ◽  
Acinetobacter Spp ◽  
Vitro Analysis ◽  
Time Kill

Introduction: Increasing carbapenem resistance in Acinetobacter spp calls for the appraisal of alternative strategies in Acinetobacter spp infection therapy. This study aims at evaluating colistin-carbapenem combination against Acinetobacter spp using the checkerboard, Etest, and time-kill methods. Methodology: One hundred nonrepetitive Acinetobacter spp isolates were collected from patients admitted at the Saint-George-Hospital-University-Medical-Center over a one year period. The identification was performed using the API20NE and confirmed by the amplification of the blaOXA-51-like. Susceptibility to colistin, and carbapenems were determined using the Etest, microdilution methods and interpreted according to the CLSI, 2015. Detection of the carbapenemases was performed by PCR amplification method. Clonality was determined by the 3-Locus PCR-typing and ERIC-PCR methods. The synergistic potential of the combination was determined by calculating the Fractional-Inhibitory-Concentration-Index, which determines a synergistic, additive, indifferent or antagonistic effect. Results: In our study (84%) of the isolates were carbapenem resistant. Only one strain showed resistance to colistin. (99%) and (77%) of the Acinetobacter spp isolates harbored blaOXA-51-like and blaOXA-23-like respectively. (86.2%) of the A.baumannii isolates pertained to the International Clone II. An additive effect of the colistin-carbapenem combination was determined using the 3 methods. A decrease of 2.6 and 2.8 folds in the MIC of colistin was showed in colistin-meropenem and colistin-imipenem, respectively (p < 0.001). The Colistin-meropenem showed better effects when compared to colistin-imipenem (p < 0.05). Only a few isolates showed a synergistic effect in the time-kill assay. Conclusion: Our study showed that the decrease in the MIC of colistin following colistin-carbapenem combination might be a promising antimicrobial approach for treating carbapenem-resistant Acinetobacter spp.

scholarly journals Can Plazomicin Alone or in Combination Be a Therapeutic Option against Carbapenem-Resistant Acinetobacter baumannii?

2015 ◽  
Vol 59 (10) ◽  
pp. 5959-5966 ◽  
Author(s):  
Cristina García-Salguero ◽  
Iciar Rodríguez-Avial ◽  
Juan J. Picazo ◽  
Esther Culebras
Keyword(s):  
Acinetobacter Baumannii ◽  
Therapeutic Option ◽  
Carbapenem Resistance ◽  
Beta Lactam ◽  
Content Type ◽  
Carbapenem Resistant ◽  
Multiple Drugs ◽  
Time Kill ◽  
Hospital Acquired

ABSTRACTNosocomial pathogens can be associated with a variety of infections, particularly in intensive care units (ICUs) and in immunocompromised patients. Usually these pathogens are resistant to multiple drugs and pose therapeutic challenges. Among these organisms,Acinetobacter baumanniiis one of the most frequent being encountered in the clinical setting. Carbapenems are very useful to treat infections caused by these drug-resistant Gram-negative bacilli, but carbapenem resistance is increasing globally. Combination therapy is frequently given empirically for hospital-acquired infections in critically ill patients and is usually composed of an adequate beta-lactam and an aminoglycoside. The purpose of this study was to evaluate thein vitroactivity of plazomicin against carbapenem-resistantAcinetobacter baumannii. Amikacin was used as a comparator. The activity of plazomicin in combination with several different antibiotics was tested by disk diffusion, the checkerboard method, and time-kill studies. Synergy was consistently observed with carbapenems (meropenem and/or imipenem) along with plazomicin or amikacin. When the aminoglycosides were combined with other classes of antibiotics, synergy was observed in some cases, depending on the strain and the antibiotic combination; importantly, there was no antagonism observed in any case. These findings indicate the potential utility of plazomicin in combination with other antibiotics (mainly carbapenems) for the treatment ofA. baumanniiinfections, including those caused by carbapenem-resistant isolates.

In vitro activity of sulbactam/durlobactam against global isolates of carbapenem-resistant Acinetobacter baumannii

2020 ◽  
Vol 75 (9) ◽  
pp. 2616-2621 ◽  
Author(s):  
Harald Seifert ◽  
Carina Müller ◽  
Danuta Stefanik ◽  
Paul G Higgins ◽  
Alita Miller ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Carbapenem Resistance ◽  
Resistance Mechanisms ◽  
The Novel ◽  
In Vitro Activity ◽  
Carbapenem Resistant ◽  
Excellent Activity ◽  
Acinetobacter Spp ◽  
Lactamase Inhibitor

Abstract Objectives To evaluate the activity of the novel broad-spectrum serine β-lactamase inhibitor durlobactam (ETX2514) combined with sulbactam against global isolates of carbapenem-resistant Acinetobacter baumannii with defined carbapenem resistance mechanisms compared with reference antimicrobials with known activity against Acinetobacter spp. Methods The susceptibility of 246 carbapenem-resistant non-duplicate A. baumannii isolates to sulbactam/durlobactam, amikacin, colistin, imipenem/sulbactam/durlobactam, imipenem, meropenem, minocycline and sulbactam was tested using broth microdilution. Isolates were obtained from various body sites from patients in 37 countries and from six world regions between 2012 and 2016. Identification of carbapenem resistance mechanisms and assignment to A. baumannii clonal lineages was based on WGS. Results Sulbactam/durlobactam showed excellent activity comparable to colistin but superior to amikacin, minocycline and sulbactam. The sulbactam/durlobactam MIC50/90 values were 1/4 and 2/4 mg/L and the colistin MIC50/90 values were 0.5 and 1 mg/L, respectively. Comparatively, amikacin, minocycline and sulbactam MIC50/90 values were 256/≥512, 2/16 and 16/64 mg/L, respectively. Conclusions Sulbactam/durlobactam had excellent in vitro potency against A. baumannii isolates, including those that were resistant to imipenem/meropenem, amikacin, minocycline and colistin, compared with other compounds. Sulbactam/durlobactam has the potential to become a useful addition to the limited armamentarium of drugs that can be used to treat this problem pathogen.

scholarly journals 1348. In vitro Activity of Plazomicin, a Next-Generation Aminoglycoside, Against Carbapenemase-Producing Klebsiella pneumoniae

2018 ◽  
Vol 5 (suppl_1) ◽  
pp. S412-S413
Author(s):  
Michael R Jacobs ◽  
Caryn E Good ◽  
Ayman M Abdelhamed ◽  
Daniel D Rhoads ◽  
Kristine M Hujer ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Carbapenem Resistance ◽  
Vitro Activity ◽  
In Vitro Activity ◽  
Next Generation ◽  
Aminoglycoside Resistance ◽  
Carbapenem Resistant ◽  
Carbapenemase Gene ◽  
Research Grant

Abstract Background Plazomicin is a next-generation aminoglycoside with in vitro activity against multidrug-resistant Gram-negative species, including carbapenem-resistant isolates. The Consortium on Resistance Against Carbapenems in Klebsiella and other Enterobacteriaceae (CRACKLE) is a federally funded, prospective multicenter consortium of 20 hospitals from nine US healthcare systems to track carbapenem-resistant Enterobacteriaceae. Methods Minimum inhibitory concentrations (MICs) of plazomicin were determined by broth microdilution according to current CLSI guidelines against a collection of 697 carbapenem-resistant Klebsiella pneumoniae with defined carbapenem resistance mechanisms, including KPC and OXA carbapenemases. Isolates were submitted by participating CRACKLE centers. Results Carbapenemases present in study isolates included KPC-2 (n = 323), KPC-3 (n = 364), KPC-4 (n = 2), OXA-48 like (n = 7), and NDM (n = 1). Plazomicin MICs ranged from ≤0.12 to &gt;32 mg/L, with MIC50 and MIC90 values of 0.25 and 1 mg/L, respectively (figure). MICs of 689 (98.8%) isolates were ≤4 mg/L, while MICs of the remaining eight isolates were &gt;32 mg/L. Plazomicin MICs were related to specific carbapenemases present in isolates: of eight isolates with MICs &gt;32 mg/L, seven contained OXA-48 like and one contained KPC-3, suggesting that these isolates possess an aminoglycoside-resistance mechanism on the same plasmid as their carbapenemase gene, such as a 16S ribosomal RNA methyltransferase, against which plazomicin is not active. Conclusion Plazomicin has good in vitro potency against a collection of carbapenemase-producing K. pneumoniae, with MIC90 value of 1 mg/L and MICs of ≤4 mg/L for 98.9% of isolates. Disclosures M. R. Jacobs, Achaogen: Investigator, Research grant. Shionogi: Investigator, Research grant. L. Connolly, Achaogen, Inc.: Consultant, Consulting fee. K. M. Krause, Achaogen: Employee, Salary. S. S. Richter, bioMerieux: Grant Investigator, Research grant. BD Diagnostics: Grant Investigator, Research grant. Roche: Grant Investigator, Research grant. Hologic: Grant Investigator, Research grant. Diasorin: Grant Investigator, Research grant. Accelerate: Grant Investigator, Research grant. Biofire: Grant Investigator, Research grant. D. Van Duin, achaogen: Scientific Advisor, Consulting fee. shionogi: Scientific Advisor, Consulting fee. Allergan: Scientific Advisor, Consulting fee. Astellas: Scientific Advisor, Consulting fee. Neumedicine: Scientific Advisor, Consulting fee. Roche: Scientific Advisor, Consulting fee. T2 Biosystems: Scientific Advisor, Consulting fee.

scholarly journals Semimechanistic Pharmacokinetic/Pharmacodynamic Modeling of Fosfomycin and Sulbactam Combination against Carbapenem-Resistant Acinetobacter baumannii

2021 ◽  
Vol 65 (5) ◽  
Author(s):  
Sazlyna Mohd Sazlly Lim ◽  
Aaron J. Heffernan ◽  
Jason A. Roberts ◽  
Fekade B. Sime
Keyword(s):  
Acinetobacter Baumannii ◽  
Treatment Options ◽  
Pharmacodynamic Modeling ◽  
Synergistic Activity ◽  
Bacterial Burden ◽  
Target Attainment ◽  
Content Type ◽  
Carbapenem Resistant ◽  
Time Kill

ABSTRACT Due to limited treatment options for carbapenem-resistant Acinetobacter baumannii (CR-AB) infections, antibiotic combinations are now considered potential treatments for CR-AB. This study aimed to explore the utility of fosfomycin-sulbactam combination (FOS/SUL) therapy against CR-AB isolates. Synergism of FOS/SUL against 50 clinical CR-AB isolates was screened using the checkerboard method. Thereafter, time-kill studies against two CR-AB isolates were performed. The time-kill data were described using a semimechanistic pharmacokinetic/pharmacodynamic (PK/PD) model. Monte Carlo simulations were then performed to estimate the probability of stasis, 1-log kill, and 2-log kill after 24 h of combination therapy. The FOS/SUL combination demonstrated a synergistic effect against 74% of isolates. No antagonism was observed. The MIC50 and MIC90 of FOS/SUL were decreased 4- to 8-fold, compared to the monotherapy MIC50 and MIC90. In the time-kill studies, the combination displayed bactericidal activity against both isolates and synergistic activity against one isolate at the highest clinically achievable concentrations. Our PK/PD model was able to describe the interaction between fosfomycin and sulbactam in vitro. Bacterial kill was mainly driven by sulbactam, with fosfomycin augmentation. FOS/SUL regimens that included sulbactam at 4 g every 8 h demonstrated a probability of target attainment of 1-log10 kill at 24 h of ∼69 to 76%, compared to ∼15 to 30% with monotherapy regimens at the highest doses. The reduction in the MIC values and the achievement of a moderate PTA of a 2-log10 reduction in bacterial burden demonstrated that FOS/SUL may potentially be effective against some CR-AB infections.

scholarly journals 687. In vitro Activity of a New Generation Oxopyrazole Antibiotic Against Acinetobacter spp.

2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S312-S312
Author(s):  
Joel Goldberg ◽  
Christopher Bethel ◽  
Andrea M Hujer ◽  
Kristine Hujer ◽  
Steven Marshall ◽  
...  
Keyword(s):  
In Vitro Activity ◽  
Penicillin Binding Proteins ◽  
Hospital Acquired Infections ◽  
New Class ◽  
Carbapenem Resistant ◽  
Acinetobacter Spp ◽  
Gram Negative Organisms ◽  
New Generation ◽  
Hospital Acquired

Abstract Background Acinetobacter spp. resistant to common antibiotics have become a worrying cause of hospital-acquired infections and represent a critical need for innovative antibacterial development. New oxopyrazole agents targeting penicillin-binding proteins (PBPs) based on a non-β-lactam core and incorporating a siderophore moiety (figure) which facilitates transport to the periplasm are being developed which show promise against Gram-negative organisms including Acinetobacter spp. Methods YU253911, an example of this new class of antibacterials, was characterized in vitro. Minimum inhibitory concentrations (MICs) were determined by broth microdilution against a collection of 200 previously described (whole-genome sequencing) Acinetobacter isolates including 98 carbapenem-resistant A. baumannii strains. YU253911’s antimicrobial activity was also evaluated in combination with complementary PBP agents and β-lactamase inhibitors by MIC and disc diffusion testing. All studies were performed according to current Clinical and Laboratory Standards Institute (CLSI) guidelines using iron-depleted media. Breakpoints for ceftazidime were arbitrarily chosen as reference. Results Using ceftazidime (breakpoint ≤8 μg/mL) as a comparator, 175 of the 200 Acinetobacter isolates were susceptible to YU253911, which possessed an MIC50 of 0.5 μg/mL and an MIC90 of 16 μg/mL. This compared favorably to all previously tested β-lactams including penicillins, cephalosporins, monobactams and carbapenems (MIC50s 2 to >16 μg/mL). Against the subset of carbapenem-resistant A. baumannii isolates, YU253911’s potency was similar with an MIC50 of 1 μg/mL. Genetic analysis showed β-lactamase genes, including OXA-23 and other carbapenemases, were common in both YU253911-resistant and susceptible strains. Conclusion YU253911 demonstrates promising in vitro potency against a collection of Acinetobacter isolates and compares favorably to β-lactam antibiotics. Understanding interactions with PBP agents and β lactamase inhibitors is being explored as well as further studies on the mechanism of resistance. Disclosures All authors: No reported disclosures.

scholarly journals In Vitro Activity of Imipenem and Colistin against a Carbapenem-ResistantKlebsiella pneumoniaeIsolate Coproducing SHV-31, CMY-2, and DHA-1

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Hung-Jen Tang ◽  
Yee-Huang Ku ◽  
Mei-Feng Lee ◽  
Yin-Ching Chuang ◽  
Wen-Liang Yu
Keyword(s):  
Outer Membrane ◽  
Multidrug Resistant ◽  
In Vitro Activity ◽  
Carbapenem Resistant ◽  
Hip Infection ◽  
Outer Membrane Porin ◽  
The Common ◽  
Inoculum Effect ◽  
Time Kill

We investigated the synergism of colistin and imipenem against a multidrug-resistantK. pneumoniaeisolate which was recovered from a severe hip infection. PCR and DNA sequencing were used to characterize the outer membrane porin genes and the resistance genes mediating the commonβ-lactamases and carbapenemases. Synergism was evaluated by time-kill studies. TheblaSHV-31,blaCMY-2, andblaDHA-1were detected. Outer membrane porin genes analysis revealed loss ofompK36and frame-shift mutation ofompK35. The common carbapenemase genes were not found. Time-kill studies demonstrated that a combination of 1x MIC of colistin (2 mg/L) and 1x MIC of imipenem (8 mg/L) was synergistic and bactericidal but with inoculum effect. Bactericidal activity without inoculum effect was observed by concentration of 2x MIC of colistin alone or plus 2x MIC of imipenem. In conclusion, colistin plus imipenem could be an alternative option to treat carbapenem-resistantK. pneumoniaeinfections.

scholarly journals Elimination of Extracellular Adenosine Triphosphate for the Rapid Prediction of Quantitative Plate Counts in 24 h Time-Kill Studies against Carbapenem-Resistant Gram-Negative Bacteria

2020 ◽  
Vol 8 (10) ◽  
pp. 1489
Author(s):  
Yiying Cai ◽  
Jonathan J. Ng ◽  
Hui Leck ◽  
Jocelyn Q. Teo ◽  
Jia-Xuan Goh ◽  
...  
Keyword(s):  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Carbapenem Resistant ◽  
Infection Models ◽  
Rapid Prediction ◽  
Atp Bioluminescence ◽  
Plate Counts ◽  
Time Kill

Traditional in vitro time-kill studies (TKSs) require viable plating, which is tedious and time-consuming. We used ATP bioluminescence, with the removal of extracellular ATP (EC-ATP), as a surrogate for viable plating in TKSs against carbapenem-resistant Gram-negative bacteria (CR-GNB). Twenty-four-hour TKSs were conducted using eight clinical CR-GNB (two Escherichia coli, two Klebsiella spp., two Acinetobacter baumannii, two Pseudomonas aeruginosa) with multiple single and two-antibiotic combinations. ATP bioluminescence and viable counts were determined at each timepoint (0, 2, 4, 8, 24 h), with and without apyrase treatment. Correlation between ATP bioluminescence and viable counts was determined for apyrase-treated and non-apyrase-treated samples. Receiver operator characteristic curves were plotted to determine the optimal luminescence threshold to discriminate between inhibitory/non-inhibitory and bactericidal/non-bactericidal combinations, compared to viable counts. After treatment of bacteria with 2 U/mL apyrase for 15 min at 37 °C, correlation to viable counts was significantly higher compared to untreated samples (p < 0.01). Predictive accuracies of ATP bioluminescence were also significantly higher for apyrase-treated samples in distinguishing inhibitory (p < 0.01) and bactericidal (p = 0.03) combinations against CR-GNB compared to untreated samples, when all species were collectively analyzed. We found that ATP bioluminescence can potentially replace viable plating in TKS. Our assay also has applications in in vitro and in vivo infection models.

In vitro synergy of ceftolozane/tazobactam in combination with fosfomycin or aztreonam against MDR Pseudomonas aeruginosa

2020 ◽  
Vol 75 (7) ◽  
pp. 1874-1878 ◽  
Author(s):  
Gabriel T Cuba ◽  
Gerlan Rocha-Santos ◽  
Rodrigo Cayô ◽  
Ana Paula Streling ◽  
Carolina S Nodari ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Resistance Mechanisms ◽  
Density Reduction ◽  
Carbapenem Resistant ◽  
Gradient Diffusion ◽  
Fold Reduction ◽  
The Face ◽  
Antimicrobial Synergy ◽  
Time Kill

Abstract Objectives Carbapenem-resistant Pseudomonas aeruginosa (CR-PSA) imposes great limitations on empirical therapeutic choices, which are further complicated by metallo-β-lactamase production. This study evaluated in vitro antimicrobial synergy of ceftolozane/tazobactam in combination with aztreonam and fosfomycin against MDR PSA. Methods MICs were determined by broth microdilution and gradient strips. The effect of ceftolozane/tazobactam+aztreonam and ceftolozane/tazobactam+fosfomycin combinations were tested against 27 MDR PSA isolates carrying blaSPM-1 (n = 13), blaIMP (n = 4), blaVIM (n = 3), blaGES-1 (n = 2) and blaCTX-M-like (n = 2), and 3 isolates with no acquired β-lactamase production detected by gradient diffusion strip crossing (GDSC). Six genetically unrelated SPM-1-producing isolates were also evaluated by time–kill analysis (TKA). Results All CR-PSA isolates harbouring blaSPM-1, blaGES-1 and blaIMP-1 were categorized as resistant to ceftolozane/tazobactam, meropenem and fosfomycin, with 70% being susceptible to aztreonam. Synergism for ceftolozane/tazobactam+fosfomycin and ceftolozane/tazobactam+aztreonam combinations was observed for 88.9% (24/27) and 18.5% (5/27) of the isolates by GDSC, respectively. A 3- to 9-fold reduction in ceftolozane/tazobactam MICs was observed, depending on the combination. Ceftolozane/tazobactam+fosfomycin was synergistic by TKA against one of six SPM-1-producing isolates, with additional non-synergistic bacterial density reduction for another isolate. Aztreonam peak concentrations alone demonstrated a ≥3 log10 cfu/mL reduction against all six isolates, but all strains were within the susceptible range for the drug. No antagonism was observed. Conclusions In the context of increasing CR-PSA and the genetic diversity of resistance mechanisms, new combinations and stewardship strategies may need to be explored in the face of increasingly difficult to treat pathogens.

scholarly journals The Clinical and Molecular Epidemiology of Noncarbapenemase-Producing Carbapenem-Resistant Enterobacteriaceae: A Case-Case-Control Matched Analysis

2020 ◽  
Vol 7 (8) ◽  
Author(s):  
Ruth Bouganim ◽  
Liana Dykman ◽  
Omar Fakeh ◽  
Yair Motro ◽  
Rivka Oren ◽  
...  
Keyword(s):  
Medical Center ◽  
Carbapenem Resistance ◽  
Case Control ◽  
Beta Lactamases ◽  
Carbapenem Resistant ◽  
Asymptomatic Carriage ◽  
Skin Ulcers ◽  
Chronic Skin ◽  
Multivariable Regression Models ◽  
Carbapenem Resistant Enterobacteriaceae

Abstract Background Risk factors and outcomes associated with carbapenem-resistant Enterobacteriaceae (CRE) acquisitions are derived primarily from cohorts consisting of carbapenemase-producing (CP) strains. Worldwide epidemiology of non-CP-CRE is evolving, but controlled epidemiological analyses are lacking. Methods A matched case-case-control investigation was conducted at Shamir (Assaf Harofeh) Medical Center, Israel, on November 2014–December 2016. Noncarbapenemase-producing CRE (as defined by the US Clinical and Laboratory Standards Institute Standards) carriers were matched to patients with non-CRE Enterobacterales and to uninfected controls (1:1:1 ratio). Matched and nonmatched multivariable regression models were constructed to analyze predictors for acquisition and the independent impact of carriage on multiple outcomes, respectively. Representative isolates were whole genome sequenced and analyzed for resistome and phylogeny. Results Noncarbapenemase-producing CRE carriers (n = 109) were matched to the 2 comparative groups (overall n = 327). Recent exposure to antibiotics (but not specifically to carbapenems), prior intensive care unit admission, and chronic skin ulcers were all independent predictors for non-CP-CRE acquisition. Acquisitions were almost exclusively associated with asymptomatic carriage (n = 104), and despite strong associations per univariable analyses, none were independently associated with worse outcomes. Genomic analyses of 13 representative isolates revealed polyclonality, confirmed the absence of carbapenemases, but confirmed the coexistence of multiple other genes contributing to carbapenem-resistance phenotype (multiple beta-lactamases and efflux pumps). Conclusions Noncarbapenemase-producing CRE acquisitions are primarily associated with asymptomatic carriage, specifically among prone populations with extensive recent exposures to antibiotics. The prevalent mode of acquisition is “emergence of resistance” (not “patient-to-patient transmission”), and therefore the role of stewardship interventions in reducing the spread of these therapeutically challenging pathogens should be further explored.

scholarly journals OmpK26, a Novel Porin Associated with Carbapenem Resistance in Klebsiella pneumoniae

2011 ◽  
Vol 55 (10) ◽  
pp. 4742-4747 ◽  
Author(s):  
Laura García-Sureda ◽  
Antonio Doménech-Sánchez ◽  
Mariette Barbier ◽  
Carlos Juan ◽  
Joan Gascó ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Outer Membrane Proteins ◽  
Systemic Infection ◽  
Carbapenem Resistance ◽  
Resistant Isolate ◽  
Identical Result ◽  
Sequencing Analysis ◽  
Content Type ◽  
Carbapenem Resistant

ABSTRACTClinical isolates ofKlebsiella pneumoniaeresistant to carbapenems are being isolated with increasing frequency. Loss of the expression of the major nonspecific porins OmpK35/36 is a frequent feature in these isolates. In this study, we looked for porins that could compensate for the loss of the major porins in carbapenem-resistant organisms. Comparison of the outer membrane proteins from twoK. pneumoniaeclinical isogenic isolates that are susceptible (KpCS-1) and resistant (KpCR-1) to carbapenems revealed the absence of OmpK35/36 and the presence of a new 26-kDa protein in the resistant isolate. An identical result was obtained when another pair of isogenic isolates that are homoresistant (Kpn-3) and heteroresistant (Kpn-17) to carbapenems were compared. Mass spectrometry and DNA sequencing analysis demonstrated that this new protein, designated OmpK26, is a small monomeric oligogalacturonate-specific porin that belongs to the KdgM family of porins. Insertion-duplication mutagenesis of the OmpK26 coding gene,yjhA, in the carbapenem-resistant, porin-deficient isolate KpCR-1 caused the expression of OmpK36 and the reversion to the carbapenem-susceptible phenotype, suggesting that OmpK26 is indispensable for KpCR-1 to lose OmpK36 and become resistant to these antibiotics. Moreover, loss of the major porin and expression of OmpK26 reducedin vitrofitness and attenuated virulence in a murine model of acute systemic infection. Altogether, these results indicate that expression of the oligogalacturonate-specific porin OmpK26 compensates for the absence of OmpK35/36 and allows carbapenem resistance inK. pneumoniaebut cannot restore the fitness of the microorganism.

Sign in / Sign up

Export Citation Format

Share Document