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517000.9762Synergistic effect of imp/ostA and msbA in hydrophobic drug resistance of Helicobacter pylori. BACKGROUND: Contamination of endoscopy equipment by Helicobacter pylori (H. pylori) frequently occurs after endoscopic examination of H. pylori-infected patients. In the hospital, manual pre-cleaning and soaking in glutaraldehyde is an important process to disinfect endoscopes. However, this might not be sufficient to remove H. pylori completely, and some glutaraldehyde-resistant bacteria might survive and be passed to the next patient undergoing endoscopic examination through unidentified mechanisms. We identified an Imp/OstA protein associated with glutaraldehyde resistance in a clinical strain, NTUH-C1, from our previous study. To better understand and manage the problem of glutaraldehyde resistance, we further investigated its mechanism. RESULTS: The minimal inhibitory concentrations (MICs) of glutaraldehyde andexpression of imp/ostA RNA in 11 clinical isolates from the National Taiwan University Hospital were determined. After glutaraldehyde treatment, RNA expression in the strains with the MICs of 4-10 microg/ml was higher than that in strains with the MICs of 1-3 microg/ml. We examined the full-genome expression of strain NTUH-S1 after glutaraldehyde treatment using a microarray and found that 40 genes were upregulated and 31 genes were downregulated. Among the upregulated genes, imp/ostA and msbA, two putative lipopolysaccharide biogenesis genes, were selected for further characterization. The sensitivity to glutaraldehyde or hydrophobic drugs increased in both of imp/ostA and msbA single mutants. The imp/ostA and msbA double mutant was also hypersensitive to these chemicals. The lipopolysaccharide contents decreased in individual imp/ostA and msbA mutants and dramatically reduced in the imp/ostA and msbA double mutant. Outer membrane permeability assay demonstrated that the imp/ostA and msbA double mutation resulted in the increase of outer membrane permeability. Ethidium bromide accumulation assay demonstrated that MsbA was involved in efflux of hydrophobic drugs. CONCLUSION: The expression levels of imp/ostA and msbA were correlated with glutaraldehyde resistance in clinical isolates after glutaraldehyde treatment. Imp/OstA and MsbA play a synergistic role in hydrophobic drugs resistance and lipopolysaccharide biogenesis in H. pylori.200919594901
245910.9745In vitro antimicrobial activity and resistance mechanisms of cefiderocol against clinical carbapenem-resistant gram-negative bacteria. BACKGROUND: The rise of carbapenem-resistant gram-negative bacteria (CRGNB) necessitates new therapeutic options such as cefiderocol. OBJECTIVE: To evaluate the in vitro efficacy of cefiderocol against clinical CRGNB and investigate associated resistance mechanisms. METHODS: A total of 370 CRGNB isolates were analyzed. Minimum inhibitory concentration (MIC) values were determined, and whole genome sequencing, efflux pump inhibition assays, and RT-qPCR were conducted to assess resistance-related mutations, gene loss, and expression changes. RESULTS: Cefiderocol demonstrated potent in vitro activity, with high susceptibility rates in C. freundii (100%), K. pneumoniae (93.3%), and E. hormaechei (92.2%), and notable activity against P. aeruginosa (80.0%) and Escherichia coli (76.8%). Efflux pump inhibition by Carbonyl Cyanide m-Chlorophenyl Hydrazone (CCCP) significantly reduced MICs in resistant strains. Key resistance mechanisms included β-lactamase gene variants (bla (OXA-66), bla (OXA-23), bla (SHV-12)), mutations in envZ, cirA, nuoC, ampC, and loss or altered expression of iron transporter genes (piuA, pirA, fepA). CONCLUSION: Cefiderocol is highly effective against CRGNB; however, resistance may arise through diverse mechanisms, including efflux pump activity. Continued surveillance of emerging resistance is essential to guide its optimal clinical use.202541113641
637320.9743Antibiotic resistance and multidrug-resistant efflux pumps expression in lactic acid bacteria isolated from pozol, a nonalcoholic Mayan maize fermented beverage. Pozol is a handcrafted nonalcoholic Mayan beverage produced by the spontaneous fermentation of maize dough by lactic acid bacteria. Lactic acid bacteria (LAB) are carriers of chromosomal encoded multidrug-resistant efflux pumps genes that can be transferred to pathogens and/or confer resistance to compounds released during the fermentation process causing food spoiling. The aim of this study was to evaluate the antibiotic sensibility and the transcriptional expression of ABC-type efflux pumps in LAB isolated from pozol that contributes to multidrug resistance. Analysis of LAB and Staphylococcus (S.) aureus ATCC 29213 and ATCC 6538 control strains to antibiotic susceptibility, minimal inhibitory concentration (MIC), and minimal bactericidal concentration (MBC) to ethidium bromide were based in "standard methods" whereas the ethidium bromide efflux assay was done by fluorometric assay. Transcriptional expression of efflux pumps was analyzed by RT-PCR. LAB showed antibiotic multiresistance profiles, moreover, Lactococcus (L.) lactis and Lactobacillus (L.) plantarum displayed higher ethidium bromide efflux phenotype than S. aureus control strains. Ethidium bromide resistance and ethidium bromide efflux phenotypes were unrelated with the overexpression of lmrD in L. lactics, or the underexpression of lmrA in L. plantarum and norA in S. aureus. These findings suggest that, moreover, the analyzed efflux pumps genes, other unknown redundant mechanisms may underlie the antibiotic resistance and the ethidium bromide efflux phenotype in L. lactis and L. plantarum. Phenotypic and molecular drug multiresistance assessment in LAB may improve a better selection of the fermentation starter cultures used in pozol, and to control the antibiotic resistance widespread and food spoiling for health safety.201627247772
574830.9740Nosocomial Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus: Sensitivity to Chlorhexidine-Based Biocides and Prevalence of Efflux Pump Genes. The widespread use of disinfectants and antiseptics has led to the emergence of nosocomial pathogens that are less sensitive to these agents, which in combination with multidrug resistance (MDR) can pose a significant epidemiologic risk. We investigated the susceptibility of nosocomial Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus to a 0.05% chlorhexidine (CHX) solution and a biocidal S7 composite solution based on CHX (0.07%) and benzalkonium chloride (BAC, 0.055%). The prevalence of efflux pump genes associated with biocide resistance and their relationship to antibiotic resistance was also determined. Both biocides were more effective against Gram-positive S. aureus than Gram-negative bacteria. The most resistant strains were P. aeruginosa strains, which were mainly killed by 0.0016% CHX and by 0.0000084% (CHX)/0.0000066% (BAC) S7. The S7 bactericidal effect was observed on P. aeruginosa and S. aureus after 10 min, while the bactericidal effect of CHX was only observed after 30 min. qacEΔ1 and qacE efflux pump genes were prevalent among E. coli and K. pneumoniae, while mexB was more often detected in P. aeruginosa. norA, norB, mepA, mdeA, and sepA were prevalent in S. aureus. The observed prevalence of efflux pump genes highlights the potential problem whereby the sensitivity of bacteria to biocides could decline rapidly in the future.202539796210
600640.9735Missense Mutations in the CrrB Protein Mediate Odilorhabdin Derivative Resistance in Klebsiella pneumoniae. NOSO-502 is a preclinical antibiotic candidate of the Odilorhabdin class. This compound exhibits activity against Enterobacteriaceae pathogens, including carbapenemase-producing bacteria and most of the Colistin (CST)-resistant strains. Among a collection of CST-resistant Klebsiella pneumoniae strains harboring mutations on genes pmrAB, mgrB, phoPQ, and crrB, only those bearing mutations in gene crrB were found to be resistant to NOSO-502.CrrB is a histidine kinase which acts with the response regulator CrrA to modulate the PmrAB system, which finally induces the restructuring of the lipopolysaccharide present on the outer membrane and thus leading to CST resistance. Moreover, crrB mutations also enhance the transcription of neighboring genes such as H239_3063, an ABC transporter transmembrane region; H239_3064, a putative efflux pump also known as KexD; and H239_3065, a N-acetyltransferase.To elucidate the mechanism of resistance to NOSO-502 induced by CrrB missense mutations in K. pneumoniae, mutants of NCTC 13442 and ATCC BAA-2146 strains resistant to NOSO-502 and CST with single amino acid substitutions in CrrB (S8N, F33Y, Y34N, W140R, N141I, P151A, P151L, P151S, P151T, F303Y) were selected. Full susceptibility to NOSO-502 was restored in crrA or crrB deleted K. pneumoniae NCTC 13442 CrrB(P151L) mutants, confirming the role of CrrAB in controlling this resistance pathway. Deletion of kexD (but no other neighboring genes) in the same mutant also restored NOSO-502-susceptibility. Upregulation of the kexD gene expression was observed for all CrrB mutants. Finally, plasmid expression of kexD in a K. pneumoniae strain missing the locus crrABC and kexD significantly increased resistance to NOSO-502.202333685902
233750.9734Klebsiella pneumoniae susceptibility to biocides and its association with cepA, qacΔE and qacE efflux pump genes and antibiotic resistance. BACKGROUND: Although antiseptics are some of the most widely used antibacterials in hospitals, there is very little information on reduced susceptibility to these biocides and its relationship with resistance to antibiotics. AIM: To determine the relationship between reduced susceptibility to biocides and the carriage of antiseptic resistance genes, cepA, qacΔE and qacE, as well as identifying the role of efflux pumps in conferring reduced susceptibility. METHODS: Susceptibility was assessed for five biocides: chlorhexidine, benzalkonium chloride, Trigene, MediHex-4, Mediscrub; and for 11 antibiotics against 64 isolates of Klebsiella pneumoniae. Susceptibility to all compounds was tested by the agar double dilution method (DDM) and the effect of efflux pumps on biocides determined by repeating the susceptibility studies in the presence of the efflux pump inhibitor carbonyl cyanide m-chlorophenyl hydrazone (CCCP). The presence of the cepA, qacΔE and qacE genes was identified by polymerase chain reaction. FINDINGS: The bacteria were not widely antibiotic resistant though a few showed reduced susceptibility to cefoxitin, chloramphenicol and rifampicin and later-generation cephalosporins but not to carbapenems. Biocide susceptibility, tested by DDM, showed that 50, 49 and 53 strains had reduced susceptibility to chlorhexidine, Trigene and benzalkonium chloride, respectively. The antiseptic resistance genes cepA, qacΔE and qacE were found in 56, 34 and one isolates respectively and their effects as efflux pumps were determined by CCCP (10 mg/L), which decreased the minimum inhibitory concentrations (MICs) of chlorhexidine and Medihex-4 by 2-128-fold but had no impact on the MICs of benzalkonium chloride, Trigene and Mediscrub. CONCLUSION: There was a close link between carriage of efflux pump genes, cepA, qacΔE and qacE genes and reduced biocide susceptibility, but not antibiotic resistance, in K. pneumoniae clinical isolates.201222498639
469760.9732Biocide-Induced Emergence of Antibiotic Resistance in Escherichia coli. Biocide use is essential and ubiquitous, exposing microbes to sub-inhibitory concentrations of antiseptics, disinfectants, and preservatives. This can lead to the emergence of biocide resistance, and more importantly, potential cross-resistance to antibiotics, although the degree, frequency, and mechanisms that give rise to this phenomenon are still unclear. Here, we systematically performed adaptive laboratory evolution of the gut bacteria Escherichia coli in the presence of sub-inhibitory, constant concentrations of ten widespread biocides. Our results show that 17 out of 40 evolved strains (43%) also decreased the susceptibility to medically relevant antibiotics. Through whole-genome sequencing, we identified mutations related to multidrug efflux proteins (mdfA and acrR), porins (envZ and ompR), and RNA polymerase (rpoA and rpoBC), as mechanisms behind the resulting (cross)resistance. We also report an association of several genes (yeaW, pyrE, yqhC, aes, pgpA, and yeeP-isrC) and specific mutations that induce cross-resistance, verified through mutation repairs. A greater capacity for biofilm formation with respect to the parent strain was also a common feature in 11 out of 17 (65%) cross-resistant strains. Evolution in the biocides chlorophene, benzalkonium chloride, glutaraldehyde, and chlorhexidine had the most impact in antibiotic susceptibility, while hydrogen peroxide and povidone-iodine the least. No cross-resistance to antibiotics was observed for isopropanol, ethanol, sodium hypochlorite, and peracetic acid. This work reinforces the link between exposure to biocides and the potential for cross-resistance to antibiotics, presents evidence on the underlying mechanisms of action, and provides a prioritized list of biocides that are of greater concern for public safety from the perspective of antibiotic resistance. SIGNIFICANCE STATEMENT: Bacterial resistance and decreased susceptibility to antimicrobials is of utmost concern. There is evidence that improper biocide (antiseptic and disinfectant) use and discard may select for bacteria cross-resistant to antibiotics. Understanding the cross-resistance emergence and the risks associated with each of those chemicals is relevant for proper applications and recommendations. Our work establishes that not all biocides are equal when it comes to their risk of inducing antibiotic resistance; it provides evidence on the mechanisms of cross-resistance and a risk assessment of the biocides concerning antibiotic resistance under residual sub-inhibitory concentrations.202133717036
537970.9732Membrane-Targeting Triphenylphosphonium Functionalized Ciprofloxacin for Methicillin-Resistant Staphylococcus aureus (MRSA). Multidrug-resistant (MDR) bacteria have become a severe problem for public health. Developing new antibiotics for MDR bacteria is difficult, from inception to the clinically approved stage. Here, we have used a new approach, modification of an antibiotic, ciprofloxacin (CFX), with triphenylphosphonium (TPP, PPh(3)) moiety via ester- (CFX-ester-PPh(3)) and amide-coupling (CFX-amide-PPh(3)) to target bacterial membranes. In this study, we have evaluated the antibacterial activities of CFX and its derivatives against 16 species of bacteria, including MDR bacteria, using minimum inhibitory concentration (MIC) assay, morphological monitoring, and expression of resistance-related genes. TPP-conjugated CFX, CFX-ester-PPh(3), and CFX-amide-PPh(3) showed significantly improved antibacterial activity against Gram-positive bacteria, Staphylococcus aureus, including MDR S. aureus (methicillin-resistant S. aureus (MRSA)) strains. The MRSA ST5 5016 strain showed high antibacterial activity, with MIC values of 11.12 µg/mL for CFX-ester-PPh(3) and 2.78 µg/mL for CFX-amide-PPh(3). The CFX derivatives inhibited biofilm formation in MRSA by more than 74.9% of CFX-amide-PPh(3). In the sub-MIC, CFX derivatives induced significant morphological changes in MRSA, including irregular deformation and membrane disruption, accompanied by a decrease in the level of resistance-related gene expression. With these promising results, this method is very likely to combat MDR bacteria through a simple TPP moiety modification of known antibiotics, which can be readily prepared at clinical sites.202033143023
229880.9731Burden of biocide resistance among multidrug-resistant bacteria isolated from various clinical specimens in a tertiary care hospital. BACKGROUND: Most studies on biocide resistance and its genetic determinants arise from environmental or food-borne microbial isolates and only a few from clinically relevant isolates. OBJECTIVES: This study determines the proportion of biocide resistance against five commonly used biocides and detects biocide resistance genes among MDR bacterial isolates using PCR. METHODS: Consecutive MDR isolates (n ​= ​180) were included (30 each of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, Staphylococcus aureus, and Enterococcus species) from clinical specimens of various inpatient units at JIPMER. The isolates were challenged at 0.5,1 and 2 Macfarland (McF) inoculum with discrete dilutions of disinfectants. The minimum bactericidal concentrations (MBCs) for 70% Ethanol, 1.5% Cresol, 2% Glutaraldehyde, 1% Cetrimide, and 1% Chlorhexidine were determined for the isolates using ATCC reference strains as controls. PCR was performed targeting qac A/B, G; smr; and nfx B genes. RESULTS: For all biocides, MDR isolates had MBCs less than the maximum MBCs of ATCC strains. For MDR K. pneumoniae, A. baumannii, and P. aeruginosa, the highest MBCs of chlorhexidine and cetrimide were ≥75 and ​≥ ​150 ​μg/ml respectively at 0.5 McF inoculum; whereas these organisms grew at higher inoculum (2McF) even at commercially recommended biocidal concentration (1%) corresponding to 750 and 1500 ​μg/ml of chlorhexidine and cetrimide respectively. Meanwhile, the highest MBCs of MDR E. coli were 75 and 150 ​μg/ml for chlorhexidine and cetrimide respectively. Interestingly, the Gram-positive cocci survived the action of up to 35% ethanol. The nfxB and qacG genes were detected in 87% and 6.67% of MDR P. aeruginosa isolates respectively with no biocide resistance genes detected among the other organisms. CONCLUSIONS: Biocide dilutions challenged with higher inoculum indicated a narrow margin of effectiveness for certain biocides. Although a significant proportion of clinical MDR isolates of P. aeruginosa harbored biocide resistance genes, this finding had no phenotypic correlation.202337769586
904690.9731Burkholderia pseudomallei resistance to antibiotics in biofilm-induced conditions is related to efflux pumps. Burkholderia pseudomallei, the causative agent of melioidosis, has been found to increase its resistance to antibiotics when growing as a biofilm. The resistance is related to several mechanisms. One of the possible mechanisms is the efflux pump. Using bioinformatics analysis, it was found that BPSL1661, BPSL1664 and BPSL1665 were orthologous genes of the efflux transporter encoding genes for biofilm-related antibiotic resistance, PA1874-PA1877 genes in Pseudomonas aeruginosa strain PAO1. Expression of selected encoding genes for the efflux transporter system during biofilm formation were investigated. Real-time reverse transcriptase PCR expression of amrB, cytoplasmic membrane protein of AmrAB-OprA efflux transporter encoding gene, was slightly increased, while BPSL1665 was significantly increased during growth of bacteria in biofilm formation. Minimum biofilm inhibition concentration and minimum biofilm eradication concentration (MBEC) of ceftazidime (CTZ), doxycycline (DOX) and imipenem were found to be 2- to 1024-times increased when compared to their MICs for of planktonic cells. Inhibition of the efflux transporter by adding phenylalanine arginine β-napthylamide (PAβN), a universal efflux inhibitor, decreased 2 to 16 times as much as MBEC in B. pseudomallei biofilms with CTZ and DOX. When the intracellular accumulation of antibiotics was tested to reveal the pump inhibition, only the concentrations of CTZ and DOX increased in PAβN treated biofilm. Taken together, these results indicated that BPSL1665, a putative precursor of the efflux pump gene, might be related to the adaptation of B. pseudomallei in biofilm conditions. Inhibition of efflux pumps may lead to a decrease of resistance to CTZ and DOX in biofilm cells.201627702426
2299100.9731Determining the resistance of carbapenem-resistant Klebsiella pneumoniae to common disinfectants and elucidating the underlying resistance mechanisms. INTRODUCTION: Carbapenem-resistant Klebsiella pneumoniae (CRKP) infection is a serious problem in hospitals worldwide, posing a particular risk to immunocompromised patients. Elimination strategies may prevent these drug-resistant bacteria from spreading within hospital environments. Here, the susceptibility of patient-derived CRKP strains to common chemical disinfectants and possible correlations between the presence of drug-resistance genes and increased resistance to disinfectants were investigated. METHODS: The minimum inhibitory (MIC) and the minimum bactericidal concentrations (MBC) of common chemical disinfectants against each CRKP strain were determined using agar dilution; K. pneumoniae ATCC700603 served as a standard. The presence of the drug-resistance genes qacΔE, qacA, acrA and qacE was determined using PCR. RESULTS: A total of 27 clinically isolated CRKP strains collected in our hospital from 2011 to 2013 exhibited sensitivity to the following common chemical disinfectants in decreasing order of sensitivity: 75% ethyl alcohol > 2% glutaraldehyde > "84" disinfectant > 0.2% benzalkonium bromide > 2% iodine tincture > 1% iodophor > 0.1% chlorhexidine acetate. Of the 27 strains, 59, 41, 19 and 15% contained qacΔE, qacA, acrA and qacE resistance genes; 15% carried acrA, qacΔE and qacA, and 26% carried both qacA and qacΔE. Comparative analysis indicated that drug-resistance genes were correlated with higher MIC values. CONCLUSION: These pan-resistant pathogenic CRKP strains contained various drug-resistance genes and exhibited relatively high resistance to ethyl alcohol, chlorhexidine acetate and iodophor. Monitoring the drug-resistance rates of CRKP strains displaying disinfectant resistance may facilitate appropriate and effective sterilisation and thus preventing the spread of these pan-resistant strains.201526184804
6372110.9731Sensitizing multi drug resistant Staphylococcus aureus isolated from surgical site infections to antimicrobials by efflux pump inhibitors. BACKGROUND: Staphylococcus aureus is a common hospital acquired infections pathogen. Multidrug-resistant Methicillin-resistant Staphylococcus aureus represents a major problem in Egyptian hospitals. The over-expression of efflux pumps is a main cause of multidrug resistance. The discovery of efflux pump inhibitors may help fight multidrug resistance by sensitizing bacteria to antibiotics. This study aimed to investigate the role of efflux pumps in multidrug resistance. METHODS: Twenty multidrug resistant S. aureus isolates were selected. Efflux pumps were screened by ethidium bromide agar cartwheel method and polymerase chain reaction. The efflux pump inhibition by seven agents was tested by ethidium bromide agar cartwheel method and the effect on sensitivity to selected antimicrobials was investigated by broth microdilution method. RESULTS: Seventy percent of isolates showed strong efflux activity, while 30% showed intermediate activity. The efflux genes mdeA, norB, norC, norA and sepA were found to play the major role in efflux, while genes mepA, smr and qacA/B had a minor role. Verapamil and metformin showed significant efflux inhibition and increased the sensitivity to tested antimicrobials, while vildagliptin, atorvastatin, domperidone, mebeverine and nifuroxazide showed no effect. CONCLUSION: Efflux pumps are involved in multidrug resistance in Staphylococcus aureus. Efflux pump inhibitors could increase the sensitivity to antimicrobials.202034394224
6190120.9729Identifying Escherichia coli genes involved in intrinsic multidrug resistance. Multidrug resistance is a major cause of clinical failure in treating bacterial infections. Increasing evidence suggests that bacteria can resist multiple antibiotics through intrinsic mechanisms that rely on gene products such as efflux pumps that expel antibiotics and special membrane proteins that block the penetration of drug molecules. In this study, Escherichia coli was used as a model system to explore the genetic basis of intrinsic multidrug resistance. A random mutant library was constructed in E. coli EC100 using transposon mutagenesis. The library was screened by growth measurement to identify the mutants with enhanced or reduced resistance to chloramphenicol (Cm). Out of the 4,000 mutants screened, six mutants were found to be more sensitive to Cm and seven were more resistant compared to the wild-type EC100. Mutations in 12 out of the 13 mutants were identified by inverse polymerase chain reaction. Mutants of the genes rob, garP, bipA, insK, and yhhX were more sensitive to Cm compared to the wild-type EC100, while the mutation of rhaB, yejM, dsdX, nagA, yccE, atpF, or htrB led to higher resistance. Overexpression of rob was found to increase the resistance of E. coli biofilms to tobramycin (Tob) by 2.7-fold, while overexpression of nagA, rhaB, and yccE significantly enhanced the susceptibility of biofilms by 2.2-, 2.5-, and 2.1-fold respectively.200818807027
5053130.9728Effects of different carbapenemase and siderophore production on cefiderocol susceptibility in Klebsiella pneumoniae. The resistance mechanism of Gram-negative bacteria to the siderophore antibiotic cefiderocol is primarily attributed to carbapenemase and siderophore uptake pathways; however, specific factors and their relationships remain to be fully elucidated. Here, we constructed cefiderocol-resistant Klebsiella pneumoniae (CRKP) strains carrying different carbapenemases and knocked out siderophore genes to investigate the roles of various carbapenemases and siderophores in the development of cefiderocol resistance. Antimicrobial susceptibility testing revealed that both bla(NDM) and bla(KPC) significantly increased the minimum inhibitory concentration (MIC) of Klebsiella pneumoniae (KP) to cefiderocol, while bla(OXA-48) showed a modest increase. Notably, KP expressing NDM exhibited a higher cefiderocol MIC compared to KP expressing KPC, although expression of NDM alone did not induce cefiderocol resistance. Laboratory evolutionary experiments demonstrated that combining pNDM with mutations in the siderophore uptake receptor gene cirA and pKPC with a mutation in the two-component system gene envZ led to KP reaching a high level of cefiderocol resistance. Although combining pOXA with mutations in the two-component system gene baeS did not induce cefiderocol resistance, it significantly reduced susceptibility. Moreover, siderophores could influence the development of cefiderocol resistance. Strains deficient in enterobactin exhibited increased susceptibility to cefiderocol, while deficiencies in yersiniabactin and salmochelin showed no significant alterations. In conclusion, carbapenemase gene expression facilitates cefiderocol resistance, but its presence alone is insufficient. Cefiderocol resistance in CRKP typically involves abnormal expression of certain genes and other factors, such as mutations in siderophore uptake receptor genes and two-component system genes. The enterobactin siderophore synthesis gene entB may also contribute to resistance.202439470196
6197140.9728Structure and location of tellurium deposited in Escherichia coli cells harbouring tellurite resistance plasmids. The plasmids RP4Ter and pHH1508a, which belong to the P and HII incompatibility groups, respectively, confer resistance to potassium tellurite (K2TeO3) on Escherichia coli. The genes for tellurite resistance were cloned from each plasmid onto the vector pUC8 to create pDT1366 and pD1364, respectively. Unstained, unfixed bacteria carrying these plasmids contained black intracellular deposits when grown on media containing tellurite. Thin sections of these bacteria fixed with glutaraldehyde were prepared and examined by electron microscopy. The black deposits were located inside the cell and were frequently associated with the inner membrane of the bacterium. Bacteria containing pDT1366 or pDT1364, and therefore a higher gene dosage of the Ter determinant, contained more black deposits, but had a decreased resistance, as measured by the minimum inhibitory concentration using the agar dilution method. Using the technique of electron spectroscopic imaging, the black intracellular deposits were shown to contain predominantly reduced metallic tellurium, and significant amounts of oxygen or carbon, thereby confirming earlier results using X-ray diffraction analysis of whole cells.19883042886
1400150.9727Comparative genomic analysis of Escherichia coli strains obtained from continuous imipenem stress evolution. The carbapenem-resistant Escherichia coli has aroused increasing attention worldwide, especially in terms of imipenem (IMP) resistance. The molecular mechanism of IMP resistance remains unclear. This study aimed to explore the resistance mechanisms of IMP in E. coli. Susceptible Sx181-0-1 strain was induced into resistance strains by adaptive laboratory evolution. The drug resistance spectrum was measured using the disk diffusion and microbroth dilution methods. Whole-genome sequencing and resequencing were used to analyze the nonsynonymous single-nucleotide polymorphisms (nsSNPs) between the primary susceptible strain and resistant strains. The expression levels of these genes with nsSNPs were identified by real-time quantitative PCR (RT-qPCR). Resistance phenotype appeared in the induced 15th generation (induction time = 183 h). Sx181-32 and Sx181-256, which had the minimum inhibitory concentrations of IMP of 8 and 64 µg ml-1, were isolated during continuous subculture exposed to increasing concentrations of IMP, respectively. A total of 19 nsSNPs were observed both in Sx181-32 and Sx181-256, distributed in rpsU, sdaC, zwf, ttuC, araJ, dacC, mrdA, secF, dacD, lpxD, mrcB, ftsI, envZ, and two unknown function genes (orf01892 and orf01933). Among these 15 genes, five genes (dacC, mrdA, lpxD, mrcB, and ftsI) were mainly involved in cell wall synthesis. The mrdA (V338A, L378P, and M574I) and mrcB (P784L, A736V, and T708A) had three amino acid substitutions, respectively. The expression levels of rpsU, ttuC, and orf01933 were elevated in both Sx181-32 and Sx181-256 compared to Sx181-0-1. The expression levels of these genes were elevated in Sx181-256, except for araJ. Bacteria developed resistance to antimicrobials by regulating various biological processes, among which the most involved is the cell wall synthesis (dacC, mrdA, lpxD, mrcB, and ftsI). The combination mutations of mrdA, envZ, and ftsI genes may increase the resistance to IMP. Our study could improve the understanding of the molecular mechanism of IMP resistance in E. coli.202235147175
6189160.9727Characterization of all RND-type multidrug efflux transporters in Vibrio parahaemolyticus. Resistance nodulation cell division (RND)-type efflux transporters play the main role in intrinsic resistance to various antimicrobial agents in many gram-negative bacteria. Here, we estimated 12 RND-type efflux transporter genes in Vibrio parahaemolyticus. Because VmeAB has already been characterized, we cloned the other 11 RND-type efflux transporter genes and characterized them in Escherichia coli KAM33 cells, a drug hypersusceptible strain. KAM33 expressing either VmeCD, VmeEF, or VmeYZ showed increased minimum inhibitory concentrations (MICs) for several antimicrobial agents. Additional four RND-type transporters were functional as efflux pumps only when co-expressed with VpoC, an outer membrane component in V. parahaemolyticus. Furthermore, VmeCD, VmeEF, and VmeYZ co-expressed with VpoC exhibited a broader substrate specificity and conferred higher resistance than that with TolC of E. coli. Deletion mutants of these transporter genes were constructed in V. parahaemolyticus. TM32 (ΔvmeAB and ΔvmeCD) had significantly decreased MICs for many antimicrobial agents and the number of viable cells after exposure to deoxycholate were markedly reduced. Strains in which 12 operons were all disrupted had very low MICs and much lower fluid accumulation in rabbit ileal loops. These results indicate that resistance nodulation cell division-type efflux transporters contribute not only to intrinsic resistance but also to exerting the virulence of V. parahaemolyticus.201323894076
6368170.9726Antibacterial effects of curcumin encapsulated in nanoparticles on clinical isolates of Pseudomonas aeruginosa through downregulation of efflux pumps. Curcumin as a flavonoid from the rhizome of Curcuma longa has antibacterial, antiviral and antifungal activity. Multidrug resistance in pathogenic bacteria is continuously increasing in hospitals. The aim of this study was to investigate the effect of curcumin encapsulated in micellar/polymersome nanoparticles as an efflux pump inhibitor (EPI) on the expression of mexX and oprM genes in curcumin-treated and -untreated isolates of Pseudomonas aeruginosa. Clinical isolates of Pseudomonas aeruginosa were treated with ciprofloxacin (sub-MICs) alone and/or in combination with curcumin-encapsulated in micellar/polymersome nanoparticles. The expression of mexX and oprM genes was quantitatively evaluated by qRT-PCR in curcumin-treated and -untreated bacteria after 24 h. Curcumin-encapsulated in nanoparticles (400 µg/mL) induced cell death up to 50% in ciprofloxacin-treated (1/2MIC) resistant isolates during 24 h, while the bacteria treated with ciprofloxacin (without curcumin) were not inhibited. Also, curcumin in different concentrations increased effect of ciprofloxacin (sub-MICs). Downregulation of mexX and oprM genes was observed in cells treated with curcumin and ciprofloxacin compared to cells treated with ciprofloxacin alone. It seems that curcumin can be used as complementary drug in ciprofloxacin-resistant isolates through downregulating genes involved in efflux pumps and trapping ciprofloxacin on bacterial cells and increasing the effects of drug.201930778922
6298180.9726Sublethal Sodium Hypochlorite Exposure: Impact on Resistance-Nodulation-Cell Division Efflux Pump Overexpression and Cross-Resistance to Imipenem. Sodium hypochlorite (NaOCl) is widely used in public healthcare facilities; this exposure can result in the development of bacterial tolerance to disinfectants, which has known links to antibiotic cross-resistance. However, the mechanism through which cross-resistance to antibiotics and disinfectants develops remains ambiguous. Therefore, this study aimed to examine the phenotypic and transcriptomic changes caused by disinfectant exposure in Gram-negative bacteria and determine the cause of cross-resistance to antibiotics. The results demonstrated that the misuse of disinfectants plays an important role in the emergence of disinfectant resistance and in the increase in antibiotic resistance. Antibiotic resistance may occur from the exposure of Gram-negative bacteria to subminimal inhibitory concentrations (MICs) of NaOCl. Ten passages of Gram-negative bacteria in increasingly higher subMICs of the NaOCl disinfectant were sufficient to increase the MIC to >2500 µg/mL NaOCl, particularly in K. pneumoniae and P. aeruginosa. To determine the development of cross-resistance to antibiotics due to NaOCl exposure, the MICs for each antibiotic before and after the exposure of each strain to sublethal concentrations of NaOCl were compared. After overnight incubation with a sublethal concentration of NaOCl, a statistically significant increase in MIC was only observed for imipenem (p < 0.01). An investigation of the mechanism of cross-resistance by means of transcriptome analysis revealed that 1250 µg/mL of NaOCl-adapted K. pneumoniae and P. aeruginosa strains increased resistance to imipenem due to the increased expression of resistance-nodulation-cell division (RND) efflux pumps, such as AcrAB-TolC and MexAB/XY-OprM. Therefore, we suggest that exposure to NaOCl can influence the expression of RND efflux pump genes, contributing to imipenem cross-resistance.202439335002
9038190.9725Molecular mechanisms of chlorhexidine tolerance in Burkholderia cenocepacia biofilms. The high tolerance of biofilm-grown Burkholderia cepacia complex bacteria against antimicrobial agents presents considerable problems for the treatment of infected cystic fibrosis patients and the implementation of infection control guidelines. In the present study, we analyzed the tolerance of planktonic and sessile Burkholderia cenocepacia J2315 cultures and examined the transcriptional response of sessile cells to treatment with chlorhexidine. At low (0.0005%) and high (0.05%) concentrations, chlorhexidine had a similar effect on both populations, but at intermediate concentrations (0.015%) the antimicrobial activity was more pronounced in planktonic cultures. The exposure of sessile cells to chlorhexidine resulted in an upregulation of the transcription of 469 (6.56%) and the downregulation of 257 (3.59%) protein-coding genes. A major group of upregulated genes in the treated biofilms encoded membrane-related and regulatory proteins. In addition, several genes coding for drug resistance determinants also were upregulated. The phenotypic analysis of RND (resistance-nodulation-division) efflux pump mutants suggests the presence of lifestyle-specific chlorhexidine tolerance mechanisms; efflux system RND-4 (BCAL2820-BCAL2822) was more responsible for chlorhexidine tolerance in planktonic cells, while other systems (RND-3 [BCAL1672-BCAL1676] and RND-9 [BCAM1945-BCAM1947]) were linked to resistance in sessile cells. After sessile cell exposure, multiple genes encoding chemotaxis and motility-related proteins were upregulated in concert with the downregulation of an adhesin-encoding gene (BCAM2143), suggesting that sessile cells tried to escape the biofilm. We also observed the differential expression of 19 genes carrying putative small RNA molecules, indicating a novel role for these regulatory elements in chlorhexidine tolerance.201121357299