Publications

• Irreversible inhibition of the Mycobacterium tuberculosis beta-lactamase by clavulanate.

  Hugonnet J.E., Blanchard J.S.

  Members of the beta-lactam class of antibiotics, which inhibit the bacterial d,d-transpeptidases involved in cell wall biosynthesis, have never been used systematically in the treatment of Mycobacterium tuberculosis infections because of this organism's resistance to beta-lactams. The critical res ... >> More

  Members of the beta-lactam class of antibiotics, which inhibit the bacterial d,d-transpeptidases involved in cell wall biosynthesis, have never been used systematically in the treatment of Mycobacterium tuberculosis infections because of this organism's resistance to beta-lactams. The critical resistance factor is the constitutive production of a chromosomally encoded, Ambler class A beta-lactamase, BlaC in M. tuberculosis. We show that BlaC is an extended spectrum beta-lactamase (ESBL) with high levels of penicillinase and cephalosporinase activity as well as measurable activity with carbapenems, including imipenem and meropenem. We have characterized the enzyme's inhibition by three FDA-approved beta-lactamase inhibitors: sulbactam, tazobactam, and clavulanate. Sulbactam inhibits the enzyme competitively and reversibly with respect to nitrocefin. Tazobactam inhibits the enzyme in a time-dependent manner, but the activity of the enzyme reappears due to the slow hydrolysis of the covalently acylated enzyme. In contrast, clavulanate reacts with the enzyme quickly to form hydrolytically stable, inactive forms of the enzyme that have been characterized by mass spectrometry. Clavulanate has potential to be used in combination with approved beta-lactam antibiotics to treat multi-drug resistant (MDR) and extremely drug resistant (XDR) strains of M. tuberculosis. << Less

  Biochemistry 46:11998-12004(2007) [PubMed] [EuropePMC]

• Characterization and sequence of the Chryseobacterium (Flavobacterium) meningosepticum carbapenemase: a new molecular class B beta-lactamase showing a broad substrate profile.

  Rossolini G.M., Franceschini N., Riccio M.L., Mercuri P.S., Perilli M., Galleni M., Frere J.-M., Amicosante G.

  The metallo-beta-lactamase produced by Chryseobacterium (formerly Flavobacterium) meningosepticum, which is the flavobacterial species of greatest clinical relevance, was purified and characterized. The enzyme, named BlaB, contains a polypeptide with an apparent Mr of 26000, and has a pI of 8.5. I ... >> More

  The metallo-beta-lactamase produced by Chryseobacterium (formerly Flavobacterium) meningosepticum, which is the flavobacterial species of greatest clinical relevance, was purified and characterized. The enzyme, named BlaB, contains a polypeptide with an apparent Mr of 26000, and has a pI of 8.5. It hydrolyses penicillins, cephalosporins (including cefoxitin), carbapenems and 6-beta-iodopenicillanate, a mechanism-based inactivator of active-site serine beta-lactamases. The enzyme was inhibited by EDTA, 1-10 phenanthroline and pyridine-2,6-dicarboxylic acid, with different inactivation parameters for each chelating agent. The C. meningosepticum blaB gene was cloned and sequenced. According to the G+C content and codon usage, the blaB gene appeared to be endogenous to the species. The BlaB enzyme showed significant sequence similarity to other class B beta-lactamases, being overall more similar to members of subclass B1, which includes the metallo-enzymes of Bacillus cereus (Bc-II) and Bacteroides fragilis (CcrA) and the IMP-1 enzyme found in various microbial species, and more distantly related to the metallo-beta-lactamases of Aeromonas spp. (CphA, CphA2 and ImiS) and of Stenotrophomonas maltophilia (L1). << Less

  Biochem. J. 332:145-152(1998) [PubMed] [EuropePMC]

• A metallo-beta-lactamase enzyme in action: crystal structures of the monozinc carbapenemase CphA and its complex with biapenem.

  Garau G., Bebrone C., Anne C., Galleni M., Frere J.M., Dideberg O.

  One strategy developed by bacteria to resist the action of beta-lactam antibiotics is the expression of metallo-beta-lactamases. CphA from Aeromonas hydrophila is a member of a clinically important subclass of metallo-beta-lactamases that have only one zinc ion in their active site and for which n ... >> More

  One strategy developed by bacteria to resist the action of beta-lactam antibiotics is the expression of metallo-beta-lactamases. CphA from Aeromonas hydrophila is a member of a clinically important subclass of metallo-beta-lactamases that have only one zinc ion in their active site and for which no structure is available. The crystal structures of wild-type CphA and its N220G mutant show the structural features of the active site of this enzyme, which is modeled specifically for carbapenem hydrolysis. The structure of CphA after reaction with a carbapenem substrate, biapenem, reveals that the enzyme traps a reaction intermediate in the active site. These three X-ray structures have allowed us to propose how the enzyme recognizes carbapenems and suggest a mechanistic pathway for hydrolysis of the beta-lactam. This will be relevant for the design of metallo-beta-lactamase inhibitors as well as of antibiotics that escape their hydrolytic activity. << Less

  J. Mol. Biol. 345:785-795(2005) [PubMed] [EuropePMC]

• Competitive inhibitors of the CphA metallo-beta-lactamase from Aeromonas hydrophila.

  Horsfall L.E., Garau G., Lienard B.M., Dideberg O., Schofield C.J., Frere J.M., Galleni M.

  Various inhibitors of metallo-beta-lactamases have been reported; however, none are effective for all subgroups. Those that have been found to inhibit the enzymes of subclass B2 (catalytically active with one zinc) either contain a thiol (and show less inhibition towards this subgroup than towards ... >> More

  Various inhibitors of metallo-beta-lactamases have been reported; however, none are effective for all subgroups. Those that have been found to inhibit the enzymes of subclass B2 (catalytically active with one zinc) either contain a thiol (and show less inhibition towards this subgroup than towards the dizinc members of B1 and B3) or are inactivators behaving as substrates for the dizinc family members. The present work reveals that certain pyridine carboxylates are competitive inhibitors of CphA, a subclass B2 enzyme. X-ray crystallographic analyses demonstrate that pyridine-2,4-dicarboxylic acid chelates the zinc ion in a bidentate manner within the active site. Salts of these compounds are already available and undergoing biomedical testing for various nonrelated purposes. Pyridine carboxylates appear to be useful templates for the development of more-complex, selective, nontoxic inhibitors of subclass B2 metallo-beta-lactamases. << Less

  Antimicrob. Agents Chemother. 51:2136-2142(2007) [PubMed] [EuropePMC]

• Purification and characterization of inducible beta-lactamases in Aeromonas spp.

  Iaconis J.P., Sanders C.C.

  beta-Lactamases from Aeromonas hydrophila and A. sobria were purified and characterized. Both species produced beta-lactamases that were inducible by either cefoxitin or imipenem. These species were resistant to ampicillin and cephalothin but not imipenem. Isoelectric focusing of sonic extracts re ... >> More

  beta-Lactamases from Aeromonas hydrophila and A. sobria were purified and characterized. Both species produced beta-lactamases that were inducible by either cefoxitin or imipenem. These species were resistant to ampicillin and cephalothin but not imipenem. Isoelectric focusing of sonic extracts revealed one band at pI 8.0 and a second band at pI 7.0 for A. hydrophila. Likewise, A. sobria produced two bands, one at pI 8.4 and the other at pI 7.0. Two enzymes from each species were separated by flatbed electrofocusing gel and purified to homogeneity. The molecular weight of the pI 7.0 enzyme (A1) from both species was estimated to be 42,500, whereas the pI 8.0 (A2h) and 8.4 (A2s) enzymes of A. hydrophila and A. sobria had molecular weights of 31,500 and 35,000, respectively, on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The relative Vmax values for cephalothin, penicillin, and imipenem for these enzymes indicated that A1 was primarily a cephalosporinase while A2h and A2s were penicillinases highly active against carbapenems. A1 was susceptible to inhibition by cloxacillin, while the A2 enzymes were inhibited by clavulanic acid and EDTA and required zinc for activity. Thus, there appear to be two distinct inducible beta-lactamases in A. hydrophila and A. sobria that play an important role in the beta-lactam resistance of these species. << Less

  Antimicrob. Agents Chemother. 34:44-51(1990) [PubMed] [EuropePMC]

• Purification, characterization, and kinetic studies of a soluble Bacteroides fragilis metallo-beta-lactamase that provides multiple antibiotic resistance.

  Wang Z., Benkovic S.J.

  Resistance to multiple beta-lactam antibiotics traced to the expression of Zn(II) requiring metallo-beta-lactamases has emerged in clinical isolates of several bacterial strains including Bacteroides fragilis, a pathogen commonly found in suppurative/surgical infections. A soluble B. fragilis meta ... >> More

  Resistance to multiple beta-lactam antibiotics traced to the expression of Zn(II) requiring metallo-beta-lactamases has emerged in clinical isolates of several bacterial strains including Bacteroides fragilis, a pathogen commonly found in suppurative/surgical infections. A soluble B. fragilis metallo-beta-lactamase has been purified to homogeneity from the cell growth medium after expression as a secretory protein in Escherichia coli. The enzyme requires two tightly bound Zn(II) ions for full activity, and the Zn(II) ions can be removed by EDTA from the enzyme. The apoenzyme is reactivated by stoichiometric amounts of Zn(II) and Co(II) ions. The Co(II)-substituted enzyme exhibits a UV-visible spectrum characterized by strong Co(II) d-d transitions at 510, 548, 615, and 635 nm and an EPR spectrum with g values of 5. 52, 4.25, and 2.01: features that serve as useful spectroscopic handles for the mechanistic studies of the enzyme. Although steady-state and transient-state kinetic studies of the soluble Zn(II) enzyme with nitrocefin as substrate found no ionizable groups with pKa values between 5.25 and 10.0 involved in catalysis, a kinetically significant proton transfer step in turnover was implicated by studies in deuterium oxide. These studies also detected the accumulation of an enzyme-bound intermediate and provide the basis for a minimal kinetic scheme describing metallo-beta-lactamase-catalyzed nitrocefin hydrolysis. << Less

  J. Biol. Chem. 273:22402-22408(1998) [PubMed] [EuropePMC]

• Crystal structure and activity studies of the Mycobacterium tuberculosis beta-lactamase reveal its critical role in resistance to beta-lactam antibiotics.

  Wang F., Cassidy C., Sacchettini J.C.

  beta-Lactam antibiotics are extremely effective in disrupting the synthesis of the bacterial cell wall in both gram-positive and gram-negative bacteria. However, they are ineffective against Mycobacterium tuberculosis, due to the production of a beta-lactamase enzyme encoded on the chromosome of M ... >> More

  beta-Lactam antibiotics are extremely effective in disrupting the synthesis of the bacterial cell wall in both gram-positive and gram-negative bacteria. However, they are ineffective against Mycobacterium tuberculosis, due to the production of a beta-lactamase enzyme encoded on the chromosome of M. tuberculosis that degrades these antibiotics. Indeed, recent studies have demonstrated that deletion of the blaC gene, the only gene encoding a beta-lactamase in M. tuberculosis, or inhibition of the encoded enzyme resulted in significantly increased sensitivity to beta-lactam antibiotics. In this paper we present a biochemical and structural characterization of M. tuberculosis BlaC. Recombinant BlaC shows a broad range of specificity with almost equal penicillinase and cepholothinase activity. While clavulanate is a mechanism-based inhibitor to class A beta-lactamase with high potency (typically K(i) < 0.1 microM), it is a relatively poor inhibitor of the M. tuberculosis BlaC (K(i) = 2.4 microM). The crystal structure of the enzyme, determined at a resolution of 1.7 A, shows that the overall fold of the M. tuberculosis enzyme is similar to other class A beta-lactamases. There are, however, several distinct features of the active site, such as the amino acid substitutions N132G, R164A, R244A, and R276E, that explain the broad specificity of the enzyme, relatively low penicillinase activity, and resistance to clavulanate. << Less

  Antimicrob. Agents Chemother. 50:2762-2771(2006) [PubMed] [EuropePMC]

• Biochemical and structural characterization of Mycobacterium tuberculosis beta-lactamase with the carbapenems ertapenem and doripenem.

  Tremblay L.W., Fan F., Blanchard J.S.

  Despite the enormous success of beta-lactams as broad-spectrum antibacterials, they have never been widely used for the treatment of tuberculosis (TB) due to intrinsic resistance that is caused by the presence of a chromosomally encoded gene (blaC) in Mycobacterium tuberculosis. Our previous studi ... >> More

  Despite the enormous success of beta-lactams as broad-spectrum antibacterials, they have never been widely used for the treatment of tuberculosis (TB) due to intrinsic resistance that is caused by the presence of a chromosomally encoded gene (blaC) in Mycobacterium tuberculosis. Our previous studies of TB BlaC revealed that this enzyme is an extremely broad-spectrum beta-lactamase hydrolyzing all beta-lactam classes. Carbapenems are slow substrates that acylate the enzyme but are only slowly deacylated and can therefore act also as potent inhibitors of BlaC. We conducted the in vitro characterization of doripenem and ertapenem with BlaC. A steady-state kinetic burst was observed with both compounds with magnitudes proportional to the concentration of BlaC used. The results provide apparent K(m) and k(cat) values of 0.18 microM and 0.016 min(-1) for doripenem and 0.18 microM and 0.017 min(-1) for ertapenem, respectively. FTICR mass spectrometry demonstrated that the doripenem and ertapenem acyl-enzyme complexes remain stable over a time period of 90 min. The BlaC-doripenem covalent complex obtained after a 90 min soak was determined to 2.2 A, while the BlaC-ertapenem complex obtained after a 90 min soak was determined to 2.0 A. The 1.3 A diffraction data from a 10 min ertapenem-soaked crystal revealed an isomerization occurring in the BlaC-ertapenem adduct in which the original Delta(2)-pyrroline ring was tautomerized to generate the Delta(1)-pyrroline ring. The isomerization leads to the flipping of the carbapenem hydroxyethyl group to hydrogen bond to carboxyl O2 of Glu166. The hydroxyethyl flip results in both the decreased basicity of Glu166 and a significant increase in the distance between carboxyl O2 of Glu166 and the catalytic water molecule, slowing hydrolysis. << Less

  Biochemistry 49:3766-3773(2010) [PubMed] [EuropePMC]

• The structure of the dizinc subclass B2 metallo-beta-lactamase CphA reveals that the second inhibitory zinc ion binds in the histidine site.

  Bebrone C., Delbruck H., Kupper M.B., Schlomer P., Willmann C., Frere J.M., Fischer R., Galleni M., Hoffmann K.M.

  Bacteria can defend themselves against beta-lactam antibiotics through the expression of class B beta-lactamases, which cleave the beta-lactam amide bond and render the molecule harmless. There are three subclasses of class B beta-lactamases (B1, B2, and B3), all of which require Zn2+ for activity ... >> More

  Bacteria can defend themselves against beta-lactam antibiotics through the expression of class B beta-lactamases, which cleave the beta-lactam amide bond and render the molecule harmless. There are three subclasses of class B beta-lactamases (B1, B2, and B3), all of which require Zn2+ for activity and can bind either one or two zinc ions. Whereas the B1 and B3 metallo-beta-lactamases are most active as dizinc enzymes, subclass B2 enzymes, such as Aeromonas hydrophila CphA, are inhibited by the binding of a second zinc ion. We crystallized A. hydrophila CphA in order to determine the binding site of the inhibitory zinc ion. X-ray data from zinc-saturated crystals allowed us to solve the crystal structures of the dizinc forms of the wild-type enzyme and N220G mutant. The first zinc ion binds in the cysteine site, as previously determined for the monozinc form of the enzyme. The second zinc ion occupies a slightly modified histidine site, where the conserved His118 and His196 residues act as metal ligands. This atypical coordination sphere probably explains the rather high dissociation constant for the second zinc ion compared to those observed with enzymes of subclasses B1 and B3. Inhibition by the second zinc ion results from immobilization of the catalytically important His118 and His196 residues, as well as the folding of the Gly232-Asn233 loop into a position that covers the active site. << Less

  Antimicrob. Agents Chemother. 53:4464-4471(2009) [PubMed] [EuropePMC]

• Molecular characterization of an enterobacterial metallo beta-lactamase found in a clinical isolate of Serratia marcescens that shows imipenem resistance.

  Osano E., Arakawa Y., Wacharotayankun R., Ohta M., Horii T., Ito H., Yoshimura F., Kato N.

  A clinical isolate of Serratia marcescens (TN9106) produced a metallo beta-lactamase (IMP-1) which conferred resistance to imipenem and broad-spectrum beta-lactams. The blaIMP gene providing imipenem resistance was cloned and expressed in Escherichia coli HB101. The IMP-1 was purified from E. coli ... >> More

  A clinical isolate of Serratia marcescens (TN9106) produced a metallo beta-lactamase (IMP-1) which conferred resistance to imipenem and broad-spectrum beta-lactams. The blaIMP gene providing imipenem resistance was cloned and expressed in Escherichia coli HB101. The IMP-1 was purified from E. coli HB101 that harbors pSMBNU24 carrying blaIMP, and its apparent molecular mass was calculated to be about 30 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Kinetic studies of IMP-1 against various beta-lactams revealed that this enzyme hydrolyzes not only various broad-spectrum beta-lactams but also carbapenems. However, aztreonam was relatively stable against IMP-1. Although clavulanate or cloxacillin failed to inhibit IMP-1, Hg2+, Fe2+, or Cu2+ blocked the enzyme's activity. Moreover, the presence of EDTA in the reaction buffer resulted in a decrease in the enzyme's activity. Carbapenem resistance was not transferred from S. marcescens TN9106 to E. coli CSH2 by conjugation. A hybridization study confirmed that blaIMP was encoded on the chromosome of S. marcescens TN9106. By nucleotide sequencing analysis, blaIMP was found to encode a protein of 246 amino acid residues and was shown to have considerable homology to the metallo beta-lactamase genes of Bacillus cereus, Bacteroides fragilis, and Aeromonas hydrophila. The G+C content of blaIMP was 39.4%. Four consensus amino acid residues, His-95, His-97, Cys-176, and His-215, which form putative zinc ligands, were conserved in the deduced amino acid sequence of IMP-1. By determination of the amino acid sequence at the N terminus of purified mature IMP-1, 18 amino acid residues were found to be processed from the N terminus of the premature enzyme as a signal peptide. These results clearly show that IMP-1 is an enterobacterial metallo beta-lactamase, of which the primary structure has been completely determined, that confers resistance to carbapenems and other broad-spectrum beta-lactams. << Less

  Antimicrob. Agents Chemother. 38:71-78(1994) [PubMed] [EuropePMC]

• Recombinant expression and characterization of the major beta-lactamase of Mycobacterium tuberculosis.

  Voladri R.K., Lakey D.L., Hennigan S.H., Menzies B.E., Edwards K.M., Kernodle D.S.

  New antibiotic regimens are needed for the treatment of multidrug-resistant tuberculosis. Mycobacterium tuberculosis has a thick peptidoglycan layer, and the penicillin-binding proteins involved in its biosynthesis are inhibited by clinically relevant concentrations of beta-lactam antibiotics. bet ... >> More

  New antibiotic regimens are needed for the treatment of multidrug-resistant tuberculosis. Mycobacterium tuberculosis has a thick peptidoglycan layer, and the penicillin-binding proteins involved in its biosynthesis are inhibited by clinically relevant concentrations of beta-lactam antibiotics. beta-Lactamase production appears to be the major mechanism by which M. tuberculosis expresses beta-lactam resistance. beta-Lactamases from the broth supernatant of 3-to 4-week-old cultures of M. tuberculosis H37Ra were partially purified by sequential gel filtration chromatography and chromatofocusing. Three peaks of beta-lactamase activity with pI values of 5.1, 4.9, and 4.5, respectively, and which accounted for 10, 78, and 12% of the total postchromatofocusing beta-lactamase activity, respectively, were identified. The beta-lactamases with pI values of 5.1 and 4.9 were kinetically indistinguishable and exhibited predominant penicillinase activity. In contrast, the beta-lactamase with a pI value of 4.5 showed relatively greater cephalosporinase activity. An open reading frame in cosmid Y49 of the DNA library of M. tuberculosis H37Rv with homology to known class A beta-lactamases was amplified from chromosomal DNA of M. tuberculosis H37Ra by PCR and was overexpressed in Escherichia coli. The recombinant enzyme was kinetically similar to the pI 5.1 and 4.9 enzymes purified directly from M. tuberculosis. It exhibited predominant penicillinase activity and was especially active against azlocillin. It was inhibited by clavulanic acid and m-aminophenylboronic acid but not by EDTA. We conclude that the major beta-lactamase of M. tuberculosis is a class A beta-lactamase with predominant penicillinase activity. A second, minor beta-lactamase with relatively greater cephalosporinase activity is also present. << Less

  Antimicrob. Agents Chemother. 42:1375-1381(1998) [PubMed] [EuropePMC]

• Meropenem-clavulanate is effective against extensively drug-resistant Mycobacterium tuberculosis.

  Hugonnet J.E., Tremblay L.W., Boshoff H.I., Barry C.E., Blanchard J.S.

  beta-lactam antibiotics are ineffective against Mycobacterium tuberculosis, being rapidly hydrolyzed by the chromosomally encoded blaC gene product. The carbapenem class of beta-lactams are very poor substrates for BlaC, allowing us to determine the three-dimensional structure of the covalent BlaC ... >> More

  beta-lactam antibiotics are ineffective against Mycobacterium tuberculosis, being rapidly hydrolyzed by the chromosomally encoded blaC gene product. The carbapenem class of beta-lactams are very poor substrates for BlaC, allowing us to determine the three-dimensional structure of the covalent BlaC-meropenem covalent complex at 1.8 angstrom resolution. When meropenem was combined with the beta-lactamase inhibitor clavulanate, potent activity against laboratory strains of M. tuberculosis was observed [minimum inhibitory concentration (MIC(meropenem)) less than 1 microgram per milliliter], and sterilization of aerobically grown cultures was observed within 14 days. In addition, this combination exhibited inhibitory activity against anaerobically grown cultures that mimic the "persistent" state and inhibited the growth of 13 extensively drug-resistant strains of M. tuberculosis at the same levels seen for drug-susceptible strains. Meropenem and clavulanate are Food and Drug Administration-approved drugs and could potentially be used to treat patients with currently untreatable disease. << Less

  Science 323:1215-1218(2009) [PubMed] [EuropePMC]

• Characterization of a new metallo-beta-lactamase gene, bla(NDM-1), and a novel erythromycin esterase gene carried on a unique genetic structure in Klebsiella pneumoniae sequence type 14 from India.

  Yong D., Toleman M.A., Giske C.G., Cho H.S., Sundman K., Lee K., Walsh T.R.

  A Swedish patient of Indian origin traveled to New Delhi, India, and acquired a urinary tract infection caused by a carbapenem-resistant Klebsiella pneumoniae strain that typed to the sequence type 14 complex. The isolate, Klebsiella pneumoniae 05-506, was shown to possess a metallo-beta-lactamase ... >> More

  A Swedish patient of Indian origin traveled to New Delhi, India, and acquired a urinary tract infection caused by a carbapenem-resistant Klebsiella pneumoniae strain that typed to the sequence type 14 complex. The isolate, Klebsiella pneumoniae 05-506, was shown to possess a metallo-beta-lactamase (MBL) but was negative for previously known MBL genes. Gene libraries and amplification of class 1 integrons revealed three resistance-conferring regions; the first contained bla(CMY-4) flanked by ISEcP1 and blc. The second region of 4.8 kb contained a complex class 1 integron with the gene cassettes arr-2, a new erythromycin esterase gene; ereC; aadA1; and cmlA7. An intact ISCR1 element was shown to be downstream from the qac/sul genes. The third region consisted of a new MBL gene, designated bla(NDM-1), flanked on one side by K. pneumoniae DNA and a truncated IS26 element on its other side. The last two regions lie adjacent to one another, and all three regions are found on a 180-kb region that is easily transferable to recipient strains and that confers resistance to all antibiotics except fluoroquinolones and colistin. NDM-1 shares very little identity with other MBLs, with the most similar MBLs being VIM-1/VIM-2, with which it has only 32.4% identity. As well as possessing unique residues near the active site, NDM-1 also has an additional insert between positions 162 and 166 not present in other MBLs. NDM-1 has a molecular mass of 28 kDa, is monomeric, and can hydrolyze all beta-lactams except aztreonam. Compared to VIM-2, NDM-1 displays tighter binding to most cephalosporins, in particular, cefuroxime, cefotaxime, and cephalothin (cefalotin), and also to the penicillins. NDM-1 does not bind to the carbapenems as tightly as IMP-1 or VIM-2 and turns over the carbapenems at a rate similar to that of VIM-2. In addition to K. pneumoniae 05-506, bla(NDM-1) was found on a 140-kb plasmid in an Escherichia coli strain isolated from the patient's feces, inferring the possibility of in vivo conjugation. The broad resistance carried on these plasmids is a further worrying development for India, which already has high levels of antibiotic resistance. << Less

  Antimicrob. Agents Chemother. 53:5046-5054(2009) [PubMed] [EuropePMC]

• The production and molecular properties of the zinc beta-lactamase of Pseudomonas maltophilia IID 1275.

  Bicknell R., Emanuel E.L., Gagnon J., Waley S.G.

  The production and purification of a tetrameric zinc beta-lactamase from Pseudomonas maltophilia IID 1275 were greatly improved. Three charge variants were isolated by chromatofocusing. The subunits each contain two atomic proportions of zinc and (in two of the variants) one residue of cysteine. T ... >> More

  The production and purification of a tetrameric zinc beta-lactamase from Pseudomonas maltophilia IID 1275 were greatly improved. Three charge variants were isolated by chromatofocusing. The subunits each contain two atomic proportions of zinc and (in two of the variants) one residue of cysteine. The thiol group is not required for activity, nor does it appear to bind to the metal. Replacement of zinc by cobalt, cadmium or nickel takes place at a measurable rate, and gives enzymes that are less active than the zinc enzyme. The properties of this enzyme differ from those of the other known zinc beta-lactamase, beta-lactamase II from Bacillus cereus. The amino acid sequence of the N-terminal 32 residues was determined; there is no similarity to the N-terminal sequences of other beta-lactamases. << Less

  Biochem. J. 229:791-797(1985) [PubMed] [EuropePMC]