Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0276640 (TEM)
 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Doripenem is a broad-spectrum parenteral carbapenem under clinical development in Japan and North America. Its activities against (i) Pseudomonas aeruginosa isolates with graded levels of intrinsic efflux-type resistance, (ii) mutants with various combinations of AmpC and OprD expression, (iii) PU21 transconjugants with class A and D beta-lactamases, and (iv) P. aeruginosa isolates with metallo-beta-lactamases were tested by the agar dilution method of the National Committee for Clinical Laboratory Standards. Selection of resistant P. aeruginosa mutants was investigated in single- and multistep procedures. Doripenem MICs for isolates without acquired resistance mostly were 0.12 to 0.5 microg/ml, whereas meropenem MICs were 0.25 to 0.5 microg/ml and imipenem MICs were 1 to 2 microg/ml. The MICs of doripenem, meropenem, ertapenem, and noncarbapenems for isolates with increased efflux-type resistance were elevated, whereas the MICs of imipenem were less affected. The MICs of doripenem were increased by the loss of OprD but not by derepression of AmpC; nevertheless, and as with other carbapenems, the impermeability-determined resistance caused by the loss of OprD corequired AmpC activity and was lost in OprD- mutants also lacking AmpC. The TEM, PSE, PER, and OXA enzymes did not significantly protect P. aeruginosa PU21 against the activity of doripenem, whereas MICs of > or =16 microg/ml were seen for clinical isolates with VIM and IMP metallo-beta-lactamases. Resistant mutants seemed to be harder to select with doripenem than with other carbapenems (or noncarbapenems), and the fold increases in the MICs were smaller for the resistant mutants. Single-step doripenem mutants were mostly resistant only to carbapenems and had lost OprD; multistep mutants had broader resistance, implying the presence of additional mechanisms, putatively including up-regulated efflux. Most mutants selected with aminoglycosides and quinolones had little or no cross-resistance to carbapenems, including doripenem.
 ...
PMID:Doripenem versus Pseudomonas aeruginosa in vitro: activity against characterized isolates, mutants, and transconjugants and resistance selection potential. 1527 24

An Escherichia coli strain with decreased susceptibility to carbapenems was isolated from a hospitalised patient in Athens, Greece. The strain was resistant to all beta-lactams, including aztreonam, whereas the MIC of imipenem and meropenem was 0.5 mg/L. A positive EDTA-disk synergy test suggested the production of a metallo-beta-lactamase. PCR experiments revealed the presence of the bla(VIM-2), bla(IBC-1), and bla(TEM-1) genes. Resistance to beta-lactams was not transferable by conjugation. This is the first report of a clinical isolate of E. coli producing VIM-2, and the first report of the coexistence of bla(VIM-2) and bla(IBC-1) in a single clinical isolate.
 ...
PMID:First identification of an Escherichia coli clinical isolate producing both metallo-beta-lactamase VIM-2 and extended-spectrum beta-lactamase IBC-1. 1530 81

The many and diverse beta-lactamases produced by bacteria, particularly by Gram-negative pathogens, are increasingly posing a serious threat to the clinical utility of beta-lactams. First-generation inhibitors (clavulanic acid, sulbactam, tazobactam) focus on Ambler class A enzymes. However, recent structural upgrades of class A beta-lactamases (e.g. TEM, SHV) have extended their spectrum (extended-spectrum beta-lactamases and carbapenemases [Sme, NMC-A, IMI-1]) and have brought about the possibility of beta-lactamase-inhibitor resistance. Furthermore, the mobilisation and spread of originally chromosomal class C enzymes (CMY, MIR), the growing clinical importance of class B enzymes (IMP, VIM), the emergence of inhibitor-resistant, broad spectrum class D (OXA) enzymes and the co-existence of different classes of beta-lactamases in the same pathogen have spurred research toward universal inhibitors. A complicating issue is target accessibility in Gram-negative bacteria, particularly in Enterobacter, Acinetobacter, Pseudomonas, Stenotrophomonas and other organisms, which is necessary in order for the inhibitor to synergise with vulnerable beta-lactam antibiotics. Several new, broad-spectrum inhibitors have emerged: cephem sulfones and oxapenems are upgrades of penam sulfones and oxapenams, respectively, with cephem sulfones possibly extending their inhibition to class B metallo-enzymes; and boronates and phosphonates are designed de novo, based on common structural and mechanistic features of serine beta-lactamases.
 ...
PMID:Beta-lactamase inhibitors: evolving compounds for evolving resistance targets. 1546 59

Resistance to beta-lactam antibiotics continues to increase, mostly due to the presence of various beta-lakta mases. As a result of the ability of the plasmids to acquire additional resistance determinants, many of the beta-lactamase producing pathogens became multidrug resistant. The most important beta-lactamases which compomise the use of beta-lactams nowdays are extended-spectrum beta-lactamases, inhibitor-resistant TEM and SHV beta-lactamases and carbapenemases. Carbapenemases are beta-lactamases which hydrolyse carbapenems. They belong to molecular classes A, B, and D. Class A comprises carbapenemases sensitive to inhibition by clavulanic acid. Most of them are chromosomaly encoded, but some of them are plasmid-mediated such as KPC-1 in Klebsiella pneumoniae and GES-2 in Pseudomonas aeruginosa. The class B carbapenemases are metallo-beta-lactamases of the IMP or VIM group. The class D carbapenemases are the most frequent in Acinetobacter baumannii but confer resistance to carbapenems only if other resistance mechanisms such as porin alterations, are present. Inhibitor resistant beta-lactamases are one of the most important causes of resistance to beta-lactam-inhibitor combinations. The resistance to these formulations can be also due to hyperproduction of TEM-1 beta-lactamase, modifications of the outer membrane proteins or production of OXA-type enzymes. IRT enzymes are derived from parenthal TEM-1 or TEM-2 beta-lactamases by point mutations in the beta-lactamase gene. The frequent use of beta-lactamase inhibitors in hospitals and general practice pose a selection pressure which favours spread of such strains in hospitals and community.
 ...
PMID:[Beta-lactamases and their role in resistance. PART 2: beta-lactamases in 21st century]. 1614 68

The acquired resistance against the wide-spectrum and highly stable beta-lactams including third-generation cephalosporins (3GC) and carbapenems is constinuously increasing and widespead with the discovery of various plasmid-encoded, or genes cassette or integrons coding for a novel beta-lactamase, always a major mechanism of resistance. To explain resistance against 3GC, with the continuing story with TEM and SHV mutated enzymes, several types of ESBL (class A) emerge the CTX-M type, at least CTX-M-40, but also other non predominant types intitled BES, GES, PLA, PER, VEB. The wider resistance including 3GC, cephamycins and beta-lactamase inhibitor is correlated to synthesis of transferable cephalosporinases (class C) usually located in the chromosome but mobilized from Enterobacter spp., Citrobacter freundii, Hafnia alvei, Morganella morganii, Aeromonas caviae. Such genes encoded the following types: ACC-1, ACT-1, CFE-1, CMY group, DHA-1, FOX group, MIR-1, MOX-1. Finally the resistance against carbapemens e.g. imipenem originally restricted to Pseudomonas aeruginosa, then to Acinetobacter baumannii and finally to enterobacteria is related to production of novel enzymes (classes B, D and A) denominated IMP, VIM SME, GIM, OXA, KPC. A striking exemple of evolution towards more and more resistance is given by Salmonella, even from animal origins, a great threat fo public health. So far it appears necessary to perform molecular approaches to identify such enzymatic production. Finally because the absence of real new drugs, the discovery of some progenitors of the gene beta-lactamase, a strict control of beta-lactam antibiotics must be provide not only in medecine or veterinary field but also in agriculture, including aquaculture for example.
 ...
PMID:[Beta-lactamases of Gram negative bacteria: never-ending clockwork!]. 1642 Sep 89

A plasmid-encoded class II transposon element was identified in a carbapenem-resistant Pseudomonas putida isolate. Tn1332, closely related to Tn1331, harbored the metallo-beta-lactamase gene bla(VIM-2) in addition to four other antibiotic resistance genes, aacA4, aadA1, bla(OXA-9), and bla(TEM-1), and two novel insertion sequences, ISPpu17 and ISPpu18.
 ...
PMID:Class II transposon-borne structure harboring metallo-beta-lactamase gene blaVIM-2 in Pseudomonas putida. 1687 Jul 96

Enterobacteria produce elementary chromosomal enzymes, Beta-lactamases of class A: TEM and SHV (Escherichia coli, Klebsiella pneumoniae). These can give rise to plasmid-coded broad-spectrum Beta-lactamases (ESBL) discovered in 1980 (E. coli, K. pneumoniae, Enterobacter cloacae). The first cefotaximase (CTX-M, MEN-1) was reported in Europe in 1990. This enzyme is far more active against cefotaxime than against ceftazidime and aztreonam. Chromosomal hyperpoduction of K1 Beta-lactamase differs from all other ESBLs due its sensitivity to ceftazidime (Klebsiella oxytoca). However, not all enterobacteria are resistant only because of ESBLs, but also as a result of the action of chromosomally or plasmid coded AmpC Beta-lactamase of class C (MIR-1, CMY-1, BIL-1, FOX-1, MOX-1, DHA-1, ACC-1), resistant to Beta-lactamase inhibitors and to cefoxitin (Enterobacter spp., Proteus vulgaris, Citrobacter freundii, Morganelle spp., Serratia spp.). With the loss of outside-membrane porins (OMP) they can become resistant to carbapenem an tibiotics. The 100% resistance of enterobacteria to carbapenems that so far exists in this country is elsewhere in the world compromised by the incidence of carbapenem-hydrolysing plasmid-determined Beta-lactamase of class B (IMP-1, VIM-1) and of class A (KPC-1) in K. pneumoniae, (SME-1) in Serratia marcescens and (IMI-1, NMC-A) in E. clocae. Carbapenemases in enterobacteria are only effective in the presence of impermeability and other resistance mechanisms.
 ...
PMID:[Development of Beta-lactamase resistance in enterobacteria]. 1705 71

Profiles and mechanisms of resistance to beta-lactam antibiotics of isolates of Gram-negative microorganisms, which are causative agents of infections in Intensive Care Unit of hospital surgery department, were studied. Two hundred and ten clinical isolates were studied: Pseudomonas aeruginosa--86 strains (40.9%), Acinetobacter baummanii--45 strains (21.4%), Klebsiella pneumoniae--52 strains (24.8%), Escherichia coli--23 strains (11%), Enterobacter spp.--4 strains (1.9%). Profiles of antibiotic resistance were studied by the method of serial microdilutions; detection of most widespread and clinically significant genes of beta-lactamases of Gram-negative bacteria was performed by polymerase chain reaction. Carbapenems and cefoperazone/sulbactam were the most active antibiotics. Local features of distribution of beta-lactamase coding genes (TEM, SHV, CTX) in K. pneumoniae and E. coli isolates were revealed. Eleven strains of P. aeruginosa resistant to carbapenems and possessing genetic determinants of VIM-group, which codes metallo-beta-lactamases, were isolated. Obtained data allows to assess the parameters of resistance to beta-lactam antibiotics and to reveal the main mechanisms of such resistance in etiologic agents of nosocomial infections, that, in its turn, allows to choose preparations for etiotropic therapy.
 ...
PMID:[Antimicrobial susceptibility and molecular mechanisms of resistance to beta-lactams of gram-negative microorganisms--causative agents of nosocomial infections]. 1803 41

Sixty-two clinical isolates of Enterobacter aerogenes resistant to expanded-spectrum cephalosporins were collected between July 2003 and May 2005. Among these isolates, 23 (37.1%) were imipenem (IPM) susceptible, and 39 (62.9%) were IPM insusceptible, of which 89.7% (35/39) were resistant and 10.3% (4/39) were intermediate. Isolate genotypes were compared by pulsed-field gel electrophoresis. Of 62 isolates, 48 belonged to epidemic pulsotype A (77.4%). This pulsotype included 37.5% and 58.4% of beta-lactam phenotypes b and a, respectively. Nine isolates (14.5%) belonged to pulsotype E, which included 22.3% and 77.7% of phenotypes b and a, respectively. The beta-lactamases with pIs of 5.4, 6.5, 8.2, and 8.2 corresponded to extended-spectrum beta-lactamases (ESBLs) TEM-20, TEM-24, SHV-5, and SHV-12, respectively. Of 39 IPM-insusceptible E. aerogenes isolates, 26 (66.6%) were determined to be metallo-beta-lactamase producers, by using a phenotypic method. Of these isolates, 24 harbored a bla(IMP-1) gene encoding a protein with a pI of >9.5, and two carried the bla(VIM-2) gene encoding a protein with a pI of 5.3, corresponding to beta-lactamases IMP-1 and VIM-2, respectively. The remaining 13 (33.4%) isolates were negative for the bla(IMP-1) and bla(VIM-2) genes but showed an alteration of their outer membrane proteins (OMPs). Ten of these isolates produced the two possible OMPs (32 and 42 kDa), with IPM MICs between 8 and 32 microg/ml, and three others produced only a 32-kDa OMP with IPM MICs >32 microg/ml. This work demonstrates that, in addition to resistance to expanded-spectrum cephalosporins, IPM resistance can occur in ESBL-producing E. aerogenes isolates by carbapenemase production or by the loss of porin in the outer membrane.
 ...
PMID:Successive emergence of extended-spectrum beta-lactamase-producing and carbapenemase-producing Enterobacter aerogenes isolates in a university hospital. 1823 76

The beta-lactamase (BLA) genes, the genes for aminoglycosides-modifying enzymes (AMEs), disinfectant-sulfanilamide resistance (qacEDelta1-sul1) genes, class 1 integrase (intl1) gene, and the qnr gene associated with plasmid-mediated quinolone resistance were analyzed using PCR and verified by DNA sequencing for 31 clinical isolates of multidrug-resistant Acinetobacter baumannii (MDRAB). The organism typing was performed by pulsed-field gel electrophoresis (PFGE). The positive rate of ADC, TEM, PER, and DHA of BLA genes were 100%, 61.3%, 19.4%, and 3.2%, respectively; however, the genes of SHV, OXA-23 group, OXA-24 group, GES, VIM, IMP, and qnr gene were negative. The positive rate of the genes of AMEs for aac (3)-I, aac (6')-I, ant (3")-I, ant (2")-I, aac (3)-II, and aac (6')-II were 67.7%, 45.2%, 29.0%, 22.6%, 12.9%, and 3.2%, respectively. The positive rate of qacEDelta1-sul1 and intl1 were 80.6% and 58.1%, respectively. Six different PFGE clones were found, of which two dominated. The findings show that clinical isolates of MDRAB harbor various kinds of resistance genes.
 ...
PMID:Detection of drug resistance-associated genes of multidrug-resistant Acinetobacter baumannii. 1848 41


1 2 3 4 5 6 7 8 9 Next >>