scholarly journals Overexpression of Efflux Pumps, Mutations in the Pumps’ Regulators, Chromosomal Mutations, and AAC(6′)-Ib-cr Are Associated With Fluoroquinolone Resistance in Diverse Sequence Types of Neonatal Septicaemic Acinetobacter baumannii: A 7-Year Single Center Study

2021 ◽  
Vol 12 ◽  
Author(s):  
Subhasree Roy ◽  
Somdatta Chatterjee ◽  
Amrita Bhattacharjee ◽  
Pinaki Chattopadhyay ◽  
Bijan Saha ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Efflux Pump ◽  
Critical Role ◽  
Holistic Approach ◽  
Efflux Pumps ◽  
Resistance Mechanisms ◽  
Fluoroquinolone Resistance ◽  
Active Efflux ◽  
Chromosomal Mutations ◽  
Sequence Types

This study investigates susceptibility toward three fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin), multiple fluoroquinolone-resistance mechanisms, and epidemiological relationship of neonatal septicaemic Acinetobacter baumannii. Previous studies on fluoroquinolone resistance in A. baumannii focused primarily on ciprofloxacin susceptibility and assessed a particular mechanism of resistance; a more holistic approach was taken here. Epidemiological relationship was evaluated by Multi Locus Sequence Typing. Minimum Inhibitory Concentrations of fluoroquinolones was determined with and without efflux pump inhibitors. Overexpression of efflux pumps, resistance-nodulation-cell-division (RND)-type, and multidrug and toxic compound extrusion (MATE)-type efflux pumps were evaluated by reverse transcriptase-qPCR. Mutations within regulatory proteins (AdeRS, AdeN, and AdeL) of RND-pumps were examined. Chromosomal mutations, presence of qnr and aac(6′)-Ib-cr were investigated. A. baumannii were highly diverse as 24 sequence-types with seven novel STs (ST-1440/ST-1441/ST-1481/ST-1482/ST-1483/ST-1484/ST-1486) were identified among 47 A. baumannii. High resistance to ciprofloxacin (96%), levofloxacin (92%), and particularly moxifloxacin (90%) was observed, with multiple mechanisms being active. Resistance to 4th generation fluoroquinolone (moxifloxacin) in neonatal isolates is worrisome. Mutations within GyrA (S83L) and ParC (S80L) were detected in more than 90% of fluoroquinolone-resistant A. baumannii (FQRAB) spread across 10 different clonal complexes (CC1/CC2/CC10/CC25/CC32/CC126/CC149/CC216/CC218/CC513). Efflux-based FQ resistance was found in 65% of FQRAB with ≥2 different active pumps in 38% of strains. Overexpression of adeB was highest (2.2−34-folds) followed by adeJ, adeG, and abeM. Amino acid changes in the regulators (AdeRS/AdeN/AdeL) either as single or multiple substitutions substantiated the overexpression of the pumps. Diverse mutations within AdeRS were detected among different CCs whereas mutations within AdeN linked to CC10 and CC32. Chromosomal mutations and active efflux pumps were detected simultaneously among 64% of FQRAB. Presence of aac(6′)-Ib-cr was also high (74% of FQRAB) but qnrS were absent. As most FQRABs had chromosomal mutations, this was considered predominant, however, isolates where pumps were also active had higher MIC values, establishing the critical role of the efflux pumps. The high variability of FQ susceptibility among FQRAB, possessing the same set of mutations in gyrA, parC, and efflux pump regulators, was also noted. This reveals the complexity of interpreting the interplay of multiple resistance mechanisms in A. baumannii.

scholarly journals Contribution of Target Gene Mutations and Efflux to Decreased Susceptibility of Salmonella enterica Serovar Typhimurium to Fluoroquinolones and Other Antimicrobials

2006 ◽  
Vol 51 (2) ◽  
pp. 535-542 ◽  
Author(s):  
Sheng Chen ◽  
Shenghui Cui ◽  
Patrick F. McDermott ◽  
Shaohua Zhao ◽  
David G. White ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Efflux Pump ◽  
Critical Role ◽  
Gene Mutations ◽  
Efflux Pumps ◽  
Fluoroquinolone Resistance ◽  
Naturally Occurring ◽  
Serovar Typhimurium ◽  
Resistant Mutants ◽  
Increased Susceptibility

ABSTRACT The mechanisms involved in fluoroquinolone resistance in Salmonella enterica include target alterations and overexpression of efflux pumps. The present study evaluated the role of known and putative multidrug resistance efflux pumps and mutations in topoisomerase genes among laboratory-selected and naturally occurring fluoroquinolone-resistant Salmonella enterica serovar Typhimurium strains. Strains with ciprofloxacin MICs of 0.25, 4, 32, and 256 μg/ml were derived in vitro using serovar Typhimurium S21. These mutants also showed decreased susceptibility or resistance to many nonfluoroquinolone antimicrobials, including tetracycline, chloramphenicol, and several β-lactams. The expression of efflux pump genes acrA, acrB, acrE, acrF, emrB, emrD, and mdlB were substantially increased (≥2-fold) among the fluoroquinolone-resistant mutants. Increased expression was also observed, but to a lesser extent, with three other putative efflux pumps: mdtB (yegN), mdtC (yegO), and emrA among mutants with ciprofloxacin MICs of ≥32 μg/ml. Deletion of acrAB or tolC in S21 and its fluoroquinolone-resistant mutants resulted in increased susceptibility to fluoroquinolones and other tested antimicrobials. In naturally occurring fluoroquinolone-resistant serovar Typhimurium strains, deletion of acrAB or tolC increased fluoroquinolone susceptibility 4-fold, whereas replacement of gyrA double mutations (S83F D87N) with wild-type gyrA increased susceptibility >500-fold. These results indicate that a combination of topoisomerase gene mutations, as well as enhanced antimicrobial efflux, plays a critical role in the development of fluoroquinolone resistance in both laboratory-derived and naturally occurring quinolone-resistant serovar Typhimurium strains.

scholarly journals Molecular Epidemiology and Mechanisms of Tigecycline Resistance in Clinical Isolates of Acinetobacter baumannii from a Chinese University Hospital

2013 ◽  
Vol 58 (1) ◽  
pp. 297-303 ◽  
Author(s):  
Mei Deng ◽  
Man-Hua Zhu ◽  
Jun-Jie Li ◽  
Sheng Bi ◽  
Zi-Ke Sheng ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Efflux Pump ◽  
Infectious Agent ◽  
Clinical Isolates ◽  
University Hospital ◽  
Resistance Pattern ◽  
Content Type ◽  
Active Efflux ◽  
Carbonyl Cyanide ◽  
Sequence Types

ABSTRACTBecause of its remarkable ability to acquire antibiotic resistance and to survive in nosocomial environments,Acinetobacter baumanniihas become a significant nosocomial infectious agent worldwide. Tigecycline is one of the few therapeutic options for treating infections caused byA. baumanniiisolates. However, tigecycline resistance has increasingly been reported. Our aim was to assess the prevalence and characteristics of efflux-based tigecycline resistance in clinical isolates ofA. baumanniicollected from a hospital in China. A total of 74A. baumanniiisolates, including 64 tigecycline-nonsusceptibleA. baumannii(TNAB) and 10 tigecycline-susceptibleA. baumannii(TSAB) isolates, were analyzed. The majority of them were determined to be positive foradeABC,adeRS,adeIJK, andabeM, while theadeEgene was found in only one TSAB isolate. Compared with the levels in TSAB isolates, the mean expression levels ofadeB,adeJ,adeG, andabeMin TNAB isolates were observed to increase 29-, 3-, 0.7-, and 1-fold, respectively. The efflux pump inhibitors (EPIs) phenyl-arginine-β-naphthylamide (PAβN) and carbonyl cyanide 3-chlorophenylhydrazone (CCCP) could partially reverse the resistance pattern of tigecycline. Moreover, thetetX1gene was detected in 12 (18.8%) TNAB isolates. To our knowledge, this is the first report of thetetX1gene being detected inA. baumanniiisolates. ST208 and ST191, which both clustered into clonal complex 92 (CC92), were the predominant sequence types (STs). This study showed that the active efflux pump AdeABC appeared to play important roles in the tigecycline resistance ofA. baumannii. The dissemination of TNAB isolates in our hospital is attributable mainly to the spread of CC92.

scholarly journals Constitutive SoxS Expression in a Fluoroquinolone-Resistant Strain with a Truncated SoxR Protein and Identification of a New Member of the marA-soxS-rob Regulon, mdtG

2009 ◽  
Vol 54 (3) ◽  
pp. 1218-1225 ◽  
Author(s):  
Anna Fàbrega ◽  
Robert G. Martin ◽  
Judah L. Rosner ◽  
M. Mar Tavio ◽  
Jordi Vila
Keyword(s):  
Antibiotic Resistance ◽  
Amino Acid ◽  
Resistant Strain ◽  
Efflux Pump ◽  
Transcriptional Activator ◽  
Resistance Mechanisms ◽  
Fluoroquinolone Resistance ◽  
Reverse Transcription Pcr ◽  
Chromosomal Mutations

ABSTRACT Elevated levels of fluoroquinolone resistance are frequently found among Escherichia coli clinical isolates. This study investigated the antibiotic resistance mechanisms of strain NorE5, derived in vitro by exposing an E. coli clinical isolate, PS5, to two selection steps with increasing concentrations of norfloxacin. In addition to the amino acid substitution in GyrA (S83L) present in PS5, NorE5 has an amino acid change in ParC (S80R). Furthermore, we now find by Western blotting that NorE5 has a multidrug resistance phenotype resulting from the overexpression of the antibiotic resistance efflux pump AcrAB-TolC. Microarray and gene fusion analyses revealed significantly increased expression in NorE5 of soxS, a transcriptional activator of acrAB and tolC. The high soxS activity is attributable to a frameshift mutation that truncates SoxR, rendering it a constitutive transcriptional activator of soxS. Furthermore, microarray and reverse transcription-PCR analyses showed that mdtG (yceE), encoding a putative efflux pump, is overexpressed in the resistant strain. SoxS, MarA, and Rob activated an mdtG::lacZ fusion, and SoxS was shown to bind to the mdtG promoter, showing that mdtG is a member of the marA-soxS-rob regulon. The mdtG marbox sequence is in the backward or class I orientation within the promoter, and its disruption resulted in a loss of inducibility by MarA, SoxS, and Rob. Thus, chromosomal mutations in parC and soxR are responsible for the increased antibiotic resistance of NorE5.

scholarly journals Triclosan resistance in clinical isolates of Acinetobacter baumannii

2009 ◽  
Vol 58 (8) ◽  
pp. 1086-1091 ◽  
Author(s):  
Yagang Chen ◽  
Borui Pi ◽  
Hua Zhou ◽  
Yunsong Yu ◽  
Lanjuan Li
Keyword(s):  
Acinetobacter Baumannii ◽  
Efflux Pump ◽  
Resistance Mechanism ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Active Efflux ◽  
Low Level ◽  
High Level ◽  
Resistance Rates ◽  
Triclosan Resistance

The susceptibility to triclosan of 732 clinical Acinetobacter baumannii isolates obtained from 25 hospitals in 16 cities in China from December 2004 to December 2005 was screened by using an agar dilution method. Triclosan MICs ranged between 0.015 and 16 mg l−1, and the MIC90 was 0.5 mg l−1, lower than the actual in-use concentration of triclosan. Twenty triclosan-resistant isolates (MICs ≥1 mg l−1) were characterized by antibiotic susceptibility, clonal relatedness, fabI mutation, fabI expression, and efflux pump phenotype and expression to elucidate the resistance mechanism of A. baumannii to triclosan. The resistance rates of triclosan-resistant isolates to imipenem, levofloxacin, amikacin and tetracycline were higher than those of triclosan-sensitive isolates. Triclosan resistance was artificially classified as low level (MICs 1–2 mg l−1) or high level (MICs ≥4 mg l−1). High-level triclosan resistance could be explained by a Gly95Ser mutation of FabI, whilst wild-type fabI was observed to be overexpressed in low-level resistant isolates. Active efflux did not appear to be a major reason for acquired triclosan resistance, but acquisition of resistance appeared to be dependent on a background of intrinsic triclosan efflux.

scholarly journals Insights into Acinetobacter baumannii: A Review of Microbiological, Virulence, and Resistance Traits in a Threatening Nosocomial Pathogen

Antibiotics ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 119 ◽  
Author(s):  
Carole Ayoub Moubareck ◽  
Dalal Hammoudi Halat
Keyword(s):  
Acinetobacter Baumannii ◽  
Virulence Factors ◽  
Efflux Pump ◽  
Iron Acquisition ◽  
Multidrug Resistant ◽  
Resistance Mechanisms ◽  
Biofilm Production ◽  
Resistant Phenotype ◽  
Severe Infections ◽  
Hydrolyzing Enzymes

Being a multidrug-resistant and an invasive pathogen, Acinetobacter baumannii is one of the major causes of nosocomial infections in the current healthcare system. It has been recognized as an agent of pneumonia, septicemia, meningitis, urinary tract and wound infections, and is associated with high mortality. Pathogenesis in A. baumannii infections is an outcome of multiple virulence factors, including porins, capsules, and cell wall lipopolysaccharide, enzymes, biofilm production, motility, and iron-acquisition systems, among others. Such virulence factors help the organism to resist stressful environmental conditions and enable development of severe infections. Parallel to increased prevalence of infections caused by A. baumannii, challenging and diverse resistance mechanisms in this pathogen are well recognized, with major classes of antibiotics becoming minimally effective. Through a wide array of antibiotic-hydrolyzing enzymes, efflux pump changes, impermeability, and antibiotic target mutations, A. baumannii models a unique ability to maintain a multidrug-resistant phenotype, further complicating treatment. Understanding mechanisms behind diseases, virulence, and resistance acquisition are central to infectious disease knowledge about A. baumannii. The aims of this review are to highlight infections and disease-producing factors in A. baumannii and to touch base on mechanisms of resistance to various antibiotic classes.

scholarly journals Two resistance nodulation division-family efflux pumps inChromobacteriumspecies and their role in antibiotic resistance and tolerance

2019 ◽  
Author(s):  
Saida Benomar ◽  
Kara C Evans ◽  
Robert L Unckless ◽  
Josephine R Chandler
Keyword(s):  
Antibiotic Resistance ◽  
Efflux Pump ◽  
Bacterial Species ◽  
Efflux Pumps ◽  
Resistance Mechanisms ◽  
Antibiotic Resistant ◽  
Burkholderia Thailandensis ◽  
New Information ◽  
Resistance Nodulation Division ◽  
Culture Growth

ABSTRACTVery little is known of the antibiotic resistance mechanisms of members of theChromobacteriumgenus. In previous studies ofChromobacterium subtsugae(formerlyC. violaceum) strain CV017, we identified a resistance nodulation division (RND)-family efflux pump (CdeAB-OprM). Here, we show thecdeAB-oprMgenes are widely distributed in members of theChromobacteriumgenus. We use antimicrobial susceptibility testing with a CV017cdeAB-oprMmutant to show the products of these genes confers resistance to a variety of antibiotics including ciprofloxacin, a clinically important antibiotic. We also identified a related RND-family pump,cseAB-oprN, in the genome of CV017 and otherC. subtsugaespecies, that is not present in other members of theChromobacteriumgenus. We demonstrate that CdeAB-OprM and CseAB-OprN are both transcriptionally induced in CV017 cells treated with sub-lethal antibiotic concentrations and they are important for induction of tolerance to different antibiotics. While CdeAB-OprM has a broad antibiotic specificity, the CseAB-OprN system is highly specific for a ribosome-targeting antibiotic produced by the saprophytic bacteriumBurkholderia thailandensis,bactobolin. Finally, we use a previously developedB. thailandensis-C. subtsugaeCV017 co-culture model to demonstrate that adding sub-lethal bactobolin at the beginning of co-culture growth increases the ability of CV017 to compete withB. thailandensisin a manner that is dependent on the CseAB-OprN system. Our results provide new information on the antibiotic resistance mechanisms ofChromobacteriumspecies and highlight the importance of efflux pumps during competition with other bacterial species.IMPORTANCEThis study describes two closely related efflux pumps in members of theChromobacteriumgenus, which includes opportunistic but often-fatal pathogens and species with highly versatile metabolic capabilities. Efflux pumps remove antibiotics from the cell and are important for antibiotic resistance. One of these pumps is broadly distributed in theChromobacteriumgenus and increases resistance to clinically relevant antibiotics. The other efflux pump is present only inChromobacterium subtsugaeand is highly specific for bactobolin, an antibiotic produced by the soil saprophyteBurkholderia thailandensis. We demonstrate these pumps can be activated to increase resistance by their antibiotic substrates, and that this activation is important forC. subtsugaeto survive in a laboratory competition experiment withB. thailandensis.These results have implications for managing antibiotic-resistantChromobacteriuminfections, bioengineering ofChromobacteriumspecies, and for understanding the evolution of efflux pumps.

scholarly journals Impact of an Intervention to Control Imipenem-Resistant Acinetobacter baumannii and Its Resistance Mechanisms: An 8-Year Survey

2021 ◽  
Vol 11 ◽  
Author(s):  
Lida Chen ◽  
Pinghai Tan ◽  
Jianming Zeng ◽  
Xuegao Yu ◽  
Yimei Cai ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Acinetobacter Baumannii ◽  
Bacterial Resistance ◽  
Efflux Pump ◽  
Resistance Mechanism ◽  
Resistance Mechanisms ◽  
Multi Drug Resistance ◽  
Minimal Inhibitory Concentrations ◽  
Resistance Rates ◽  
The Impact

BackgroundThis study aimed to examine the impact of an intervention carried out in 2011 to combat multi-drug resistance and outbreaks of imipenem-resistant Acinetobacter baumannii (IRAB), and to explore its resistance mechanism.MethodsA total of 2572 isolates of A. baumannii, including 1673 IRAB isolates, were collected between 2007 and 2014. An intervention was implemented to control A. baumannii resistance and outbreaks. Antimicrobial susceptibility was tested by calculating minimal inhibitory concentrations (MICs), and outbreaks were typed using pulsed-field gel electrophoresis (PFGE). Resistance mechanisms were explored by polymerase chain reaction (PCR) and whole genome sequencing (WGS).ResultsFollowing the intervention in 2011, the resistance rates of A. baumannii to almost all tested antibiotics decreased, from 85.3 to 72.6% for imipenem, 100 to 80.8% for ceftriaxone, and 45.0 to 6.9% for tigecycline. The intervention resulted in a decrease in the number (seven to five), duration (8–3 months), and departments (five to three) affected by outbreaks; no outbreaks occurred in 2011. After the intervention, only blaAMPC (76.47 to 100%) and blaTEM–1 (75.74 to 96.92%) increased (P < 0.0001); whereas blaGES–1 (32.35 to 3.07%), blaPER–1 (21.32 to 1.54%), blaOXA–58 (60.29 to 1.54%), carO (37.50 to 7.69%), and adeB (9.56 to 3.08%) decreased (P < 0.0001). Interestingly, the frequency of class B β-lactamase genes decreased from 91.18% (blaSPM–1) and 61.03% (blaIMP–1) to 0%, while that of class D blaOXA–23 increased to 96.92% (P < 0.0001). WGS showed that the major PFGE types causing outbreaks each year (type 01, 11, 18, 23, 26, and 31) carried the same resistance genes (blaKPC–1, blaADC–25, blaOXA–66, and adeABC), AdeR-S mutations (G186V and A136V), and a partially blocked porin channel CarO. Meanwhile, plasmids harboring blaOXA–23 were found after the intervention.ConclusionThe intervention was highly effective in reducing multi-drug resistance of A. baumannii and IRAB outbreaks in the long term. The resistance mechanisms of IRAB may involve genes encoding β-lactamases, efflux pump overexpression, outer membrane porin blockade, and plasmids; in particular, clonal spread of blaOXA–23 was the major cause of outbreaks. Similar interventions may also help reduce bacterial resistance rates and outbreaks in other hospitals.

scholarly journals Characteristics and diversity of mutations in regulatory genes of resistance-nodulation-cell division efflux pumps in association with drug-resistant clinical isolates of Acinetobacter baumannii

2020 ◽  
Author(s):  
Bahare Salehi ◽  
Zohreh Ghalavand ◽  
Abbas Yadegar ◽  
Gita Eslami
Keyword(s):  
Cell Division ◽  
Acinetobacter Baumannii ◽  
Efflux Pump ◽  
Efflux Pumps ◽  
Regulatory Genes ◽  
Clinical Isolates ◽  
Drug Resistant ◽  
Broth Microdilution Method ◽  
Rnd Efflux Pumps ◽  
Multiple Antibiotics

Abstract Background: This study aimed to characterize the regulation and expression of three putative resistance-nodulation-cell division (RND)-type efflux systems and their contribution to multidrug efflux in clinical isolates of Acinetobacter baumannii. Methods: Antimicrobial susceptibility testing (AST) of 95 A. baumannii isolates was determined by Kirby-Bauer disk diffusion for 18 antibiotics and minimum inhibitory concentration (MIC) of colistin was determined by broth microdilution method. Moreover, MIC of five classes of antibiotics was assessed using E-test strips in the presence and absence of phenylalanine-arginine beta-naphthylamide (PAβN). Regulatory genes of RND efflux pumps (AdeRS, AdeL, AdeN and BaeSR) were subjected to sequencing. The relative expression of adeB. adeG and adeJ genes was determined by quantitative real-time PCR (RT-PCR).Results: Overall, majority of isolates (93%) were extensively drug-resistant (XDR). In the phenotypic assay, efflux pump activity was observed in 40% of isolates against multiple antibiotics mainly tigecycline, but not to imipenem. Several amino acid substitutions were detected in the regulatory genes; except in AdeN. Of note, G186V in AdeS were found to be associated with overexpression of their relative efflux pumps. No insertion sequences (ISs) were detected. Conclusions: Our findings outline the role of RND efflux pumps in resistance of A. baumannii against multiple antibiotics particularly tigecycline, and point out importance of a variety of single mutations in the corresponding regulatory systems. Even though it has been concluded that multidrug resistance occurs as a result of a complex sets of different resistant mechanisms.

scholarly journals EFFLUX PUMP OVEREXPRESSION PROFILING IN ACINETOBACTER BAUMANNII AND STUDY OF NEW 1-(1-NAPHTHYLMETHYL)-PIPERAZINE ANALOGS AS POTENTIAL EFFLUX INHIBITORS

2021 ◽  
Author(s):  
Morgane Choquet ◽  
Elodie Lohou ◽  
Etienne Pair ◽  
Pascal Sonnet ◽  
Catherine Mullie
Keyword(s):  
Antibiotic Resistance ◽  
Acinetobacter Baumannii ◽  
Inhibitory Activity ◽  
Efflux Pump ◽  
Parent Compound ◽  
Efflux Pumps ◽  
Quinoline Derivative ◽  
Genes Encoding ◽  
Efflux Pump Inhibitors ◽  
Therapeutic Alternatives

Overexpression of efflux pumps extruding antibiotics currently used for the treatment of Acinetobacter baumannii infections has been described as an important mechanism causing antibiotic resistance. The first aim of this work was to phenotypically evaluate the overexpression of efflux pumps on a collection of 124 ciprofloxacin resistant A. baumannii strains. An overexpression of genes encoding one or more efflux pumps was obtained for 19 out of the 34 strains with a positive phenotypic efflux (56%). The most frequent genes overexpressed were those belonging to the RND family, with adeJ being the most prevalent (50%). Interestingly, efflux pump genes coding for MATE and MFS families were also overexpressed quite frequently: abeM (32%) and abaQ (26%). The second aim was to synthesize 1-(1-NaphthylMethyl)-Piperazine analogs as potential new efflux pump inhibitors and biologically evaluate them against strains with a positive phenotypic efflux. Quinoline and pyridine analogs were found to be more effective than their parent compound 1-(1-NaphthylMethyl)-Piperazine. Stereochemistry also played an important part in the inhibitory activity as quinoline derivative ( R )-3a was identified as being the most effective and less cytotoxic. Its inhibitory activity was also correlated to the number of efflux pumps expressed by a strain. The results obtained in this work suggest that quinoline analogs of 1-(1-NaphthylMethyl)-Piperazine are promising leads in the development of new anti- Acinetobacter baumannii therapeutic alternatives, in combination with antibiotics for which an efflux-mediated resistance is suspected.

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