scholarly journals Resistance to Glycopeptide Antibiotics in the Teicoplanin Producer Is Mediated by van Gene Homologue Expression Directing the Synthesis of a Modified Cell Wall Peptidoglycan

2007 ◽  
Vol 51 (4) ◽  
pp. 1135-1141 ◽  
Author(s):  
Fabrizio Beltrametti ◽  
Arianna Consolandi ◽  
Lucia Carrano ◽  
Francesca Bagatin ◽  
Roberta Rossi ◽  
...  
Keyword(s):  
Cell Wall ◽  
Resistance Mechanism ◽  
Gene Clusters ◽  
Glycopeptide Antibiotics ◽  
Constitutive Analysis ◽  
High Concentrations ◽  
High Level ◽  
Gene Homologue ◽  
Level Resistance ◽  
Comprehensive Study

ABSTRACT Glycopeptide resistance has been studied in detail in enterococci and staphylococci. In these microorganisms, high-level resistance is achieved by replacing the C-terminal d-alanyl-d-alanine of the nascent peptidoglycan with d-alanyl-d-lactate or d-alanyl-d-serine, thus reducing the affinities of glycopeptides for cell wall targets. Reorganization of the cell wall is directed by the expression of the van gene clusters. The identification of van gene homologs in the genomes of several glycopeptide-producing actinomycetes suggests the involvement of a similar self-resistance mechanism to avoid suicide. This report describes a comprehensive study of self-resistance in Actinoplanes teichomyceticus ATCC 31121, the producer of the clinically relevant glycopeptide teicoplanin. A. teichomyceticus ATCC 31121 showed a MIC of teicoplanin of 25 μg/ml and a MIC of vancomycin of 90 μg/ml during vegetative growth. The vanH, vanA, and vanX genes of A. teichomyceticus were found to be organized in an operon whose transcription was constitutive. Analysis of the UDP-linked peptidoglycan precursors revealed the presence of UDP-glycomuramyl pentadepsipeptide terminating in d-alanyl-d-lactate. No trace of precursors ending in d-alanyl-d-alanine was detected. Thus, the van gene complex was transcribed and expressed in the genetic background of A. teichomyceticus and conferred resistance to vancomycin and teicoplanin through the modification of cell wall biosynthesis. During teicoplanin production (maximum productivity, 70 to 80 μg/ml), the MIC of teicoplanin remained in the range of 25 to 35 μg/ml. Teicoplanin-producing cells were found to be tolerant to high concentrations of exogenously added glycopeptides, which were not bactericidal even at 5,000 μg/ml.

scholarly journals Resistance of Saccharomyces cerevisiae to High Concentrations of Furfural Is Based on NADPH-Dependent Reduction by at Least Two Oxireductases

2009 ◽  
Vol 75 (24) ◽  
pp. 7631-7638 ◽  
Author(s):  
Dominik Heer ◽  
Daniel Heine ◽  
Uwe Sauer
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Defense Mechanism ◽  
Resistance Mechanism ◽  
Pentose Phosphate ◽  
Process Conditions ◽  
Transcript Analysis ◽  
Reading Frame ◽  
High Concentrations ◽  
High Level ◽  
Level Resistance

ABSTRACT Biofuels derived from lignocellulosic biomass hold promises for a sustainable fuel economy, but several problems hamper their economical feasibility. One important problem is the presence of toxic compounds in processed lignocellulosic hydrolysates, with furfural as a key toxin. While Saccharomyces cerevisiae has some intrinsic ability to reduce furfural to the less-toxic furfuryl alcohol, higher resistance is necessary for process conditions. By comparing an evolved, furfural-resistant strain and its parent in microaerobic, glucose-limited chemostats at increasing furfural challenge, we elucidate key mechanism and the molecular basis of both natural and high-level furfural resistance. At lower concentrations of furfural, NADH-dependent oxireductases are the main defense mechanism. At furfural concentrations above 15 mM, however, 13C-flux and global array-based transcript analysis demonstrated that the NADPH-generating flux through the pentose phosphate pathway increases and that NADPH-dependent oxireductases become the major resistance mechanism. The transcript analysis further revealed that iron transmembrane transport is upregulated in response to furfural. While these responses occur in both strains, high-level resistance in the evolved strain was based on strong induction of ADH7, the uncharacterized open reading frame (ORF) YKL071W, and four further, likely NADPH-dependent, oxireductases. By overexpressing the ADH7 gene and the ORF YKL071W, we inversely engineered significantly increased furfural resistance in the parent strain, thereby demonstrating that these two enzymes are key elements of the resistance phenotype.

scholarly journals WGS of Commensal Neisseria Reveals Acquisition of a New Ribosomal Protection Protein (MsrD) as a Possible Explanation for High Level Azithromycin Resistance in Belgium

Pathogens ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 384
Author(s):  
Tessa de Block ◽  
Jolein Gyonne Elise Laumen ◽  
Christophe Van Dijck ◽  
Said Abdellati ◽  
Irith De Baetselier ◽  
...  
Keyword(s):  
Integration Site ◽  
Bacterial Species ◽  
Resistance Mechanism ◽  
Health Concern ◽  
Sex With Men ◽  
High Level ◽  
Ribosomal Protection Protein ◽  
Commensal Neisseria ◽  
Level Resistance ◽  
Ribosomal Protection

In this study, we characterized all oropharyngeal and anorectal isolates of Neisseria spp. in a cohort of men who have sex with men. This resulted in a panel of pathogenic Neisseria (N. gonorrhoeae [n = 5] and N. meningitidis [n = 5]) and nonpathogenic Neisseria (N. subflava [n = 11], N. mucosa [n = 3] and N. oralis [n = 2]). A high proportion of strains in this panel were resistant to azithromycin (18/26) and ceftriaxone (3/26). Whole genome sequencing (WGS) of these strains identified numerous mutations that are known to confer reduced susceptibility to azithromycin and ceftriaxone in N. gonorrhoeae. The presence or absence of these known mutations did not explain the high level resistance to azithromycin (>256 mg/L) in the nonpathogenic isolates (8/16). After screening for antimicrobial resistance (AMR) genes, we found a ribosomal protection protein, Msr(D), in these highly azithromycin resistant nonpathogenic strains. The complete integration site originated from Streptococcus pneumoniae and is associated with high level resistance to azithromycin in many other bacterial species. This novel AMR resistance mechanism to azithromycin in nonpathogenic Neisseria could be a public health concern if it were to be transmitted to pathogenic Neisseria. This study demonstrates the utility of WGS-based surveillance of nonpathogenic Neisseria.

scholarly journals Phenotypic Characterization of Two Ancylostoma caninum Isolates with Different Susceptibilities to the Anthelmintic Pyrantel

2008 ◽  
Vol 52 (11) ◽  
pp. 3980-3986 ◽  
Author(s):  
Steven R. Kopp ◽  
Glen T. Coleman ◽  
James S. McCarthy ◽  
Andrew C. Kotze
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Resistance Mechanism ◽  
Fold Increase ◽  
Phenotypic Characterization ◽  
Gastrointestinal Helminths ◽  
Ancylostoma Caninum ◽  
High Level ◽  
Level Resistance

ABSTRACT The anthelmintic pyrantel plays an important role in the control of gastrointestinal helminths of humans and domestic animals. Despite the demonstration of pyrantel resistance in several helminth species over the last 20 years, the resistance mechanism remains unclear. It has been hypothesized that resistance may arise as a consequence of changes to the relative proportions of subpopulations of nicotinic acetylcholine receptors (nAchRs). To test this hypothesis, we examined the responses of two isolates of the canine hookworm Ancylostoma caninum with low-level resistance (isolate NT) and high-level resistance (isolate PR) to pyrantel to nicotinic agonist drugs reported to be selective for three nAchR subtypes. We used larval motility and conformation assays and force transduction experiments with adult worms. Pyrantel and levamisole were less potent against larvae of isolate PR than larvae of isolate NT (up to an 18-fold increase in the 50% inhibitory concentration); on the other hand, bephenium was more potent against larvae of isolate PR than larvae of isolate NT (twofold) and nicotine had the same potency against larvae of both isolates. In adults, pyrantel, levamisole, and nicotine were less potent against isolate PR than isolate NT (two- to threefold), but the potency of bephenium against the two isolates was equivalent. Our data indicate a complex pattern of nAchRs in this species and suggest that the two isolates differ in their relative sensitivities to agonists targeting different nAchRs.

scholarly journals High-Level β-Lactam Resistance and Cell Wall Synthesis Catalyzed by the mecA Homologue of Staphylococcus sciuri Introduced into Staphylococcus aureus

2005 ◽  
Vol 187 (19) ◽  
pp. 6651-6658 ◽  
Author(s):  
Anatoly Severin ◽  
Shang Wei Wu ◽  
Keiko Tabei ◽  
Alexander Tomasz
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
High Performance ◽  
Protein Product ◽  
Spectrometric Analysis ◽  
Cell Wall Synthesis ◽  
Absolute Dependence ◽  
A Cell ◽  
High Concentrations ◽  
High Level

ABSTRACT A close homologue of mecA, the determinant of broad-spectrum β-lactam resistance in Staphylococcus aureus was recently identified as a native gene in the animal commensal species Staphylococcus sciuri. Introduction of the mecA homologue from a methicillin-resistant strain of S. sciuri into a susceptible strain of S. aureus caused an increase in drug resistance and allowed continued growth and cell wall synthesis of the bacteria in the presence of high concentrations of antibiotic. We determined the muropeptide composition of the S. sciuri cell wall by using a combination of high-performance liquid chromatography, mass spectrometric analysis, and Edman degradation. Several major differences between the cell walls of S. aureus and S. sciuri were noted. The pentapeptide branches in S. sciuri were composed of one alanine and four glycine residues in contrast to the pentaglycine units in S. aureus. The S. sciuri wall but not the wall of S. aureus contained tri- and tetrapeptide units, suggesting the presence of dd- and ld-carboxypeptidase activity. Most interestingly, S. aureus carrying the S. sciuri mecA and growing in methicillin-containing medium produced a cell wall typical of S. aureus and not S. sciuri, in spite of the fact that wall synthesis under these conditions had an absolute dependence on the heterologous S. sciuri gene product. The protein product of the S. sciuri mecA can efficiently participate in cell wall biosynthesis and build a cell wall using the cell wall precursors characteristic of the S. aureus host.

scholarly journals Sequence Analysis of the gyrA andparC Homologues of a Wild-Type Strain of Vibrio parahaemolyticus and Its Fluoroquinolone-Resistant Mutants

1999 ◽  
Vol 43 (5) ◽  
pp. 1156-1162 ◽  
Author(s):  
Jun Okuda ◽  
Eriko Hayakawa ◽  
Mitsuaki Nishibuchi ◽  
Takeshi Nishino
Keyword(s):  
Vibrio Parahaemolyticus ◽  
Resistance Mechanism ◽  
Point Mutations ◽  
Erwinia Carotovora ◽  
Open Reading Frames ◽  
Fluoroquinolone Resistance ◽  
Degenerate Primers ◽  
Resistant Mutants ◽  
High Level ◽  
Level Resistance

ABSTRACT Vibrio parahaemolyticus causes seafood-borne gastroenteritis in humans. It is particularly important in Japan, where raw seafood is frequently consumed. Fluoroquinolone is one of the current drugs of choice for treating patients infected by V. parahaemolyticus because resistant strains are rarely found. To study a possible fluoroquinolone resistance mechanism in this organism, nucleotide sequences that are homologous to known gyrA andparC genes have been cloned from V. parahaemolyticus AQ3815 and sequenced by amplification with degenerate primers of the quinolone resistance-determining region (QRDR), followed by cassette ligation-mediated PCR. Open reading frames encoding polypeptides of 878 and 761 amino acid residues were detected in the gyrA and parC homologues, respectively. The V. parahaemolyticus GyrA and ParC sequences were most closely related to Erwinia carotovora GyrA (76% identity) and Escherichia coli ParC (69% identity) sequences, respectively. Ciprofloxacin-resistant mutants of AQ3815 were obtained on an agar medium by multistep selection with increasing levels of the quinolone. One point mutation only in the gyrA QRDR was detected among mutants with low- to intermediate-level resistance, while point mutations in both the gyrA and parCQRDRs were detected only in strains with high-level resistance. These results strongly suggest that, as in other gram-negative bacteria, GyrA and ParC are the primary and secondary targets, respectively, of ciprofloxacin in V. parahaemolyticus.

scholarly journals DdlN from Vancomycin-Producing Amycolatopsis orientalis C329.2 Is a VanA Homologue withd-Alanyl-d-Lactate Ligase Activity

1998 ◽  
Vol 180 (21) ◽  
pp. 5792-5795 ◽  
Author(s):  
C. Gary Marshall ◽  
Gerard D. Wright
Keyword(s):  
Glycopeptide Antibiotics ◽  
Sources Of Resistance ◽  
Amycolatopsis Orientalis ◽  
Close Relationship ◽  
Key Enzyme ◽  
Vancomycin Resistant ◽  
High Level ◽  
Evaluation Of Kinetic Parameters ◽  
Level Resistance

ABSTRACT Vancomycin-resistant enterococci acquire high-level resistance to glycopeptide antibiotics through the synthesis of peptidoglycan terminating in d-alanyl-d-lactate. A key enzyme in this process is a d-alanyl-d-alanine ligase homologue, VanA or VanB, which preferentially catalyzes the synthesis of the depsipeptide d-alanyl-d-lactate. We report the overexpression, purification, and enzymatic characterization of DdlN, a VanA and VanB homologue encoded by a gene of the vancomycin-producing organism Amycolatopsis orientalisC329.2. Evaluation of kinetic parameters for the synthesis of peptides and depsipeptides revealed a close relationship between VanA and DdlN in that depsipeptide formation was kinetically preferred at physiologic pH; however, the DdlN enzyme demonstrated a narrower substrate specificity and commensurately increased affinity ford-lactate in the C-terminal position over VanA. The results of these functional experiments also reinforce the results of previous studies that demonstrated that glycopeptide resistance enzymes from glycopeptide-producing bacteria are potential sources of resistance enzymes in clinically relevant bacteria.

scholarly journals Characterization of an Enterococcus gallinarum Isolate Carrying a DualvanAandvanBCassette

2015 ◽  
Vol 53 (7) ◽  
pp. 2225-2229 ◽  
Author(s):  
Alireza Eshaghi ◽  
Dea Shahinas ◽  
Aimin Li ◽  
Ruwandi Kariyawasam ◽  
Philip Banh ◽  
...  
Keyword(s):  
Clinical Isolate ◽  
Resistance Mechanism ◽  
Vancomycin Resistance ◽  
Content Type ◽  
Enterococcal Species ◽  
Enterococcus Gallinarum ◽  
High Level ◽  
Identification And Characterization ◽  
Level Resistance

The ability of vancomycin resistance determinants to be horizontally transferred within enterococci species is a concern. Identification and characterization of vancomycin-resistant enterococci (VRE) in a clinical isolate have a significant impact on infection control practices. In this study, we describe a clinical isolate ofEnterococcus gallinarumexhibiting high-level resistance to vancomycin and teicoplanin. The genetic characterization of this isolate showed the presence ofvanAandvanBgenes in addition to the naturally carriedvanCgene.vanAwas identified on pA6981, a 35,608-bp circular plasmid with significant homology to plasmid pS177. ThevanBoperon was integrated into the bacterial chromosome and showed a high level of homology to previously reported Tn1549and Tn5382. To the best of our knowledge, this is the first report ofE. gallinarumcarrying bothvanAandvanBoperons, indicating the importance of identifying the vancomycin resistance mechanism in non-E. faeciumand non-E. faecalisenterococcal species.

scholarly journals A Comparison of High-Level Aminoglycoside Resistance in Vancomycin-Sensitive and Vancomycin-Resistant Enterococcus Species

2002 ◽  
Vol 30 (5) ◽  
pp. 529-534 ◽  
Author(s):  
H Yazgi ◽  
M Ertek ◽  
S Erol ◽  
A Ayyildiz
Keyword(s):  
Brain Heart Infusion ◽  
Bactericidal Effect ◽  
Vancomycin Resistance ◽  
Glycopeptide Antibiotics ◽  
Aminoglycoside Resistance ◽  
Significant Difference ◽  
Vancomycin Resistant ◽  
High Level ◽  
Infusion Agar ◽  
Level Resistance

The aim of this study was to investigate whether there was a significant difference in high-level aminoglycoside resistance (HLAR) between vancomycin-sensitive enterococci (VSE) and vancomycin-resistant enterococci (VRE). Vancomycin resistance was determined in 116 Enterococcus isolates using brain-heart infusion agar containing 6 μg/ml vancomycin. HLAR was determined by both standard agar screening and disk diffusion methods. Streptomycin and gentamicin were used as predictors of HLAR. Vancomycin resistance and HLAR were found in 17 (14.7%) and 41 (35.3%) of the Enterococcus strains, respectively. HLAR was found in 11 of 17 VRE and 30 of 98 VSE strains. HLAR in VRE strains was significantly higher than in VSE. More enterococcal strains were found to be resistant to both gentamicin and streptomycin (29) than to gentamicin (one) or streptomycin (11) alone. The HLAR rate in VRE was two-fold higher than in VSE. The synergistic bactericidal effect of aminoglycosides and β-lactam or glycopeptide antibiotics is lost if there is high-level resistance to aminoglycosides.

scholarly journals Novel Mechanism of Resistance to Glycopeptide Antibiotics in Enterococcus faecium

2006 ◽  
Vol 281 (43) ◽  
pp. 32254-32262 ◽  
Author(s):  
Julie Cremniter ◽  
Jean-Luc Mainardi ◽  
Nathalie Josseaume ◽  
Jean-Charles Quincampoix ◽  
Lionel Dubost ◽  
...  
Keyword(s):  
Enterococcus Faecium ◽  
Peptide Bond ◽  
Cross Resistance ◽  
Glycopeptide Antibiotics ◽  
Penicillin Binding Proteins ◽  
Gram Positive Bacteria ◽  
High Level ◽  
Hydrolysis Of ◽  
Link Formation ◽  
Level Resistance

Glycopeptides and β-lactams are the major antibiotics available for the treatment of infections due to Gram-positive bacteria. Emergence of cross-resistance to these drugs by a single mechanism has been considered as unlikely because they inhibit peptidoglycan polymerization by different mechanisms. The glycopeptides bind to the peptidyl-d-Ala4-d-Ala5 extremity of peptidoglycan precursors and block by steric hindrance the essential glycosyltransferase and d,d-transpeptidase activities of the penicillin-binding proteins (PBPs). The β-lactams are structural analogues of d-Ala4-d-Ala5 and act as suicide substrates of the d,d-transpeptidase module of the PBPs. Here we have shown that bypass of the PBPs by the recently described β-lactam-insensitive l,d-transpeptidase from Enterococcus faecium (Ldtfm) can lead to high level resistance to glycopeptides and β-lactams. Cross-resistance was selected by glycopeptides alone or serially by β-lactams and glycopeptides. In the corresponding mutants, UDP-MurNAc-pentapeptide was extensively converted to UDP-MurNAc-tetrapeptide following hydrolysis of d-Ala5, thereby providing the substrate of Ldtfm. Complete elimination of d-Ala5, a residue essential for glycopeptide binding, was possible because Ldtfm uses the energy of the l-Lys3-d-Ala4 peptide bond for cross-link formation in contrast to PBPs, which use the energy of the d-Ala4-d-Ala5 bond. This novel mechanism of glycopeptide resistance was unrelated to the previously identified replacement of d-Ala5 by d-Ser or d-lactate.

scholarly journals Glycopeptide Antibiotic Resistance Genes in Glycopeptide-Producing Organisms

1998 ◽  
Vol 42 (9) ◽  
pp. 2215-2220 ◽  
Author(s):  
C. G. Marshall ◽  
I. A. D. Lessard ◽  
I.-S. Park ◽  
G. D. Wright
Keyword(s):  
Resistance Genes ◽  
Resistance Mechanism ◽  
Antibiotic Resistance Genes ◽  
Amino Acid Sequences ◽  
Glycopeptide Antibiotics ◽  
Degenerate Primers ◽  
Vancomycin Resistant Enterococci ◽  
Genes Encoding ◽  
Vancomycin Resistant ◽  
High Level

ABSTRACT The mechanism of high-level resistance to vancomycin in enterococci consists of the synthesis of peptidoglycan terminating ind-alanyl-d-lactate instead of the usuald-alanyl-d-alanine. This alternate cell wall biosynthesis pathway is ensured by the collective actions of three enzymes: VanH, VanA, and VanX. The origin of this resistance mechanism is unknown. We have cloned three genes encoding homologs of VanH, VanA, and VanX from two organisms which produce glycopeptide antibiotics: the A47934 producer Streptomyces toyocaensis NRRL 15009 and the vancomycin producer Amycolatopsis orientalis C329.2. The predicted amino acid sequences are highly similar to those found in VRE: 54 to 61% identity for VanH, 59 to 63% identity for VanA, and 61 to 64% identity for VanX. Furthermore, the orientations of the genes,vanH, vanA, and vanX, are identical to the orientations found in vancomycin-resistant enterococci. Southern analysis of total DNA from other glycopeptide-producing organisms,A. orientalis 18098 (chloro-eremomycin producer), A. orientalis subsp. lurida (ristocetin producer), andAmycolatopsis coloradensis subsp. labeda(teicoplanin and avoparcin producer), with a probe derived from thevanH, vanA, and vanX cluster fromA. orientalis C329.2 revealed cross-hybridizing DNA in all strains. In addition, the vanH, vanA,vanX cluster was amplified from all glycopeptide-producing organisms by PCR with degenerate primers complementary to conserved regions in VanH and VanX. Thus, this gene sequence is common to all glycopeptide producers tested. These results suggest that glycopeptide-producing organisms may have been the source of resistance genes in vancomycin-resistant enterococci.

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