Antimicrob Agents Chemother
February 2019
Class D carbapenemases are enzymes of the utmost clinical importance due to their ability to confer resistance to the last-resort carbapenem antibiotics. We investigated the role of the conserved hydrophobic bridge in the carbapenemase activity of OXA-23, the major carbapenemase of the important pathogen We show that substitution of the bridge residue Phe110 affects resistance to meropenem and doripenem and has little effect on MICs of imipenem. The opposite effect was observed upon substitution of the other bridge residue Met221.
View Article and Find Full Text PDFActa Crystallogr D Struct Biol
August 2017
Carbapenem-hydrolyzing class D β-lactamases (CHDLs) produce resistance to the last-resort carbapenem antibiotics and render these drugs ineffective for the treatment of life-threatening infections. Here, it is shown that among the clinically important CHDLs, OXA-143 produces the highest levels of resistance to carbapenems and has the highest catalytic efficiency against these substrates. Structural data demonstrate that acylated carbapenems entirely fill the active site of CHDLs, leaving no space for water molecules, including the deacylating water.
View Article and Find Full Text PDFProduction of β-lactamases of one of four molecular classes (A, B, C and D) is the major mechanism of bacterial resistance to β-lactams, the largest class of antibiotics, which have saved countless lives since their inception 70 years ago. Although several hundred efficient class D enzymes have been identified in Gram-negative pathogens over the last four decades, none have been reported in Gram-positive bacteria. Here we demonstrate that efficient class D β-lactamases capable of hydrolyzing a wide array of β-lactam substrates are widely disseminated in various species of environmental Gram-positive organisms.
View Article and Find Full Text PDFClass D β-lactamases of Acinetobacter baumannii are enzymes of the utmost clinical importance, producing resistance to last resort carbapenem antibiotics. Although the OXA-51-like enzymes constitute the largest family of class D β-lactamases, they are poorly studied and their importance in conferring carbapenem resistance is controversial. We present the detailed microbiological, kinetic, and structural characterization of the eponymous OXA-51 β-lactamase.
View Article and Find Full Text PDFMycoplasma mycoides subsp. capri is a causative agent of contagious agalactia in goats. In this study, M.
View Article and Find Full Text PDFIn the face of the clinical challenge posed by resistant bacteria, the present needs for novel classes of antibiotics are genuine. In silico docking and screening, followed by chemical synthesis of a library of quinazolinones, led to the discovery of (E)-3-(3-carboxyphenyl)-2-(4-cyanostyryl)quinazolin-4(3H)-one (compound 2) as an antibiotic effective in vivo against methicillin-resistant Staphylococcus aureus (MRSA). This antibiotic impairs cell-wall biosynthesis as documented by functional assays, showing binding of 2 to penicillin-binding protein (PBP) 2a.
View Article and Find Full Text PDFThe structure-activity relationship (SAR) for the newly discovered oxadiazole class of antibiotics is described with evaluation of 120 derivatives of the lead structure. This class of antibiotics was discovered by in silico docking and scoring against the crystal structure of a penicillin-binding protein. They impair cell-wall biosynthesis and exhibit activities against the Gram-positive bacterium Staphylococcus aureus, including methicillin-resistant S.
View Article and Find Full Text PDFActa Crystallogr D Biol Crystallogr
March 2014
ADC-type class C β-lactamases comprise a large group of enzymes that are encoded by genes located on the chromosome of Acinetobacter baumannii, a causative agent of serious bacterial infections. Overexpression of these enzymes renders A. baumannii resistant to various β-lactam antibiotics and thus severely compromises the ability to treat infections caused by this deadly pathogen.
View Article and Find Full Text PDFInfections caused by hard-to-treat methicillin-resistant Staphylococcus aureus (MRSA) are a serious global public-health concern, as MRSA has become broadly resistant to many classes of antibiotics. We disclose herein the discovery of a new class of non-β-lactam antibiotics, the oxadiazoles, which inhibit penicillin-binding protein 2a (PBP2a) of MRSA. The oxadiazoles show bactericidal activity against vancomycin- and linezolid-resistant MRSA and other Gram-positive bacterial strains, in vivo efficacy in a mouse model of infection, and have 100% oral bioavailability.
View Article and Find Full Text PDFCarbapenem-hydrolyzing class D β-lactamases (CHDLs) are enzymes of the utmost clinical importance due to their ability to produce resistance to carbapenems, the antibiotics of last resort for the treatment of various life-threatening infections. The vast majority of these enzymes have been identified in Acinetobacter spp., notably in Acinetobacter baumannii.
View Article and Find Full Text PDFAntimicrob Agents Chemother
November 2014
Class D β-lactamases capable of hydrolyzing last-resort carbapenem antibiotics represent a major challenge for treatment of bacterial infections. Wide dissemination of these enzymes in Acinetobacter baumannii elevated this pathogen to the category of most deadly and difficult to treat. We present here the structure of the OXA-58 β-lactamase, a major class D carbapenemase of A.
View Article and Find Full Text PDFThe Class D β-lactamases have emerged as a prominent resistance mechanism against β-lactam antibiotics that previously had efficacy against infections caused by pathogenic bacteria, especially by Acinetobacter baumannii and the Enterobacteriaceae. The phenotypic and structural characteristics of these enzymes correlate to activities that are classified either as a narrow spectrum, an extended spectrum, or a carbapenemase spectrum. We focus on Class D β-lactamases that are carried on plasmids and, thus, present particular clinical concern.
View Article and Find Full Text PDFDissemination of Acinetobacter baumannii strains harboring class D β-lactamases producing resistance to carbapenem antibiotics severely limits our ability to treat deadly Acinetobacter infections. Susceptibility determination in the A. baumannii background and kinetic studies with a homogeneous preparation of OXA-23 β-lactamase, the major carbapenemase present in A.
View Article and Find Full Text PDFAntimicrob Agents Chemother
January 2013
Aminoglycoside 2″-phosphotransferases are the major aminoglycoside-modifying enzymes in clinical isolates of enterococci and staphylococci. We describe a novel aminoglycoside 2″-phosphotransferase from the Gram-negative pathogen Campylobacter jejuni, which shares 78% amino acid sequence identity with the APH(2″)-Ia domain of the bifunctional aminoglycoside-modifying enzyme aminoglycoside (6') acetyltransferase-Ie/aminoglycoside 2″-phosphotransferase-Ia or AAC(6')-Ie/APH(2″)-Ia from Gram-positive cocci, which we called APH(2″)-If. This enzyme confers resistance to the 4,6-disubstituted aminoglycosides kanamycin, tobramycin, dibekacin, gentamicin, and sisomicin, but not to arbekacin, amikacin, isepamicin, or netilmicin, but not to any of the 4,5-disubstituted antibiotics tested.
View Article and Find Full Text PDFAntimicrob Agents Chemother
November 2012
The class A carbapenemase KPC-6 produces resistance to a broad range of β-lactam antibiotics. This enzyme hydrolyzes penicillins, the monobactam aztreonam, and carbapenems with similar catalytic efficiencies, ranging from 10(5) to 10(6) M(-1) s(-1). The catalytic efficiencies of KPC-6 against cephems vary to a greater extent, ranging from 10(3) M(-1) s(-1) for the cephamycin cefoxitin and the extended-spectrum cephalosporin ceftazidime to 10(5) to 10(6) M(-1) s(-1) for the narrow-spectrum and some of the extended-spectrum cephalosporins.
View Article and Find Full Text PDFFPH-1 is a new class A carbapenemase from Francisella philomiragia. It produces high-level resistance to penicillins and the narrow-spectrum cephalosporin cephalothin and hydrolyzes these β-lactam antibiotics with catalytic efficiencies of 10(6) to 10(7) M(-1) s(-1). When expressed in Escherichia coli, the enzyme confers resistance to clavulanic acid, tazobactam, and sulbactam and has K(i) values of 7.
View Article and Find Full Text PDFAntimicrob Agents Chemother
February 2012
The class A β-lactamase FTU-1 produces resistance to penicillins and ceftazidime but not to any other β-lactam antibiotics tested. FTU-1 hydrolyzes penicillin antibiotics with catalytic efficiencies of 10(5) to 10(6) M(-1) s(-1) and cephalosporins and carbapenems with catalytic efficiencies of 10(2) to 10(3) M(-1) s(-1), but the monobactam aztreonam and the cephamycin cefoxitin are not substrates for the enzyme. FTU-1 shares 21 to 34% amino acid sequence identity with other class A β-lactamases and harbors two cysteine residues conserved in all class A carbapenemases.
View Article and Find Full Text PDFThe Glu166Arg/Met182Thr mutant of Escherichia coli TEM(pTZ19-3) β-lactamase produces a 128-fold increase in the level of resistance to the antibiotic ceftazidime in comparison to that of the parental wild-type enzyme. The single Glu166Arg mutation resulted in a dramatic decrease in both the level of enzyme expression in bacteria and the resistance to penicillins, with a concomitant 4-fold increase in the resistance to ceftazidime, a third-generation cephalosporin. Introduction of the second amino acid substitution, Met182Thr, restored enzyme expression to a level comparable to that of the wild-type enzyme and resulted in an additional 32-fold increase in the minimal inhibitory concentration of ceftazidime to 64 μg/mL.
View Article and Find Full Text PDFAntimicrob Agents Chemother
April 2011
Bacterial resistance to β-lactam antibiotics (penicillins, cephalosporins, carbapenems, etc.) is commonly the result of the production of β-lactamases. The emergence of β-lactamases capable of turning over carbapenem antibiotics is of great concern, since these are often considered the last resort antibiotics in the treatment of life-threatening infections.
View Article and Find Full Text PDFAcquired resistance to aminoglycoside antibiotics primarily results from deactivation by three families of aminoglycoside-modifying enzymes. Here, we report the kinetic mechanism and structure of the aminoglycoside phosphotransferase 2''-IVa (APH(2'')-IVa), an enzyme responsible for resistance to aminoglycoside antibiotics in clinical enterococcal and staphylococcal isolates. The enzyme operates via a Bi-Bi sequential mechanism in which the two substrates (ATP or GTP and an aminoglycoside) bind in a random manner.
View Article and Find Full Text PDFObjectives: The role of sdiA in the acquisition of low-level multidrug resistance (MDR) was analysed and compared with that of marA and soxS in two Escherichia coli clinical isolates and two in vitro-selected mutants.
Methods: The mutants were developed by growth in lomefloxacin and ceftazidime. The sdiA, marA, soxS, ftsI, tolC and acrB gene transcript levels were determined by RT-PCR.
The detection of mycoplasma in milk can be performed by either culture techniques or polymerase chain reaction (PCR) based methods. Although PCR can reduce the average diagnostic time to 5 h in comparison with the several days for the isolation of the agent, there is still a need to develop methods, which could give earlier results. For this purpose, we tested the ability of flow cytometry (FC) to detect mycoplasmas in milk samples.
View Article and Find Full Text PDFFlow cytometry has become a valuable tool in different fields of microbiology, such as clinical microbiology, aquatic and environmental microbiology, food microbiology, and biotechnology. It combines direct and rapid assays to determine numbers, biochemical and physiological characteristics of individual cells, revealing the heterogeneity present in a population. This review focuses on the applications of flow cytometry to the field of mycoplasmology.
View Article and Find Full Text PDFIn this study, flow cytometry was evaluated for the determination of the minimal inhibitory concentrations (MIC) of seven antibacterial agents (enrofloxacin, ciprofloxacin, gentamicin, streptomycin, chloramphenicol, oxytetracycline, and tylosin) on Mycoplasma (M.) agalactiae. Flow cytometry was able to detect M.
View Article and Find Full Text PDFFlow cytometry together with SYBR green I and propidium iodide was used to study the effects of enrofloxacin, ciprofloxacin, gentamicin, chloramphenicol, oxytetracycline, and tylosin on four mycoplasma species. Inhibition of mycoplasma growth could be detected by as early as 3 h after the start of treatment. The strongest effect was observed with enrofloxacin- and ciprofloxacin-treated cells.
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