RESUMO
A cefotaxime-resistant Klebsiella pneumoniae ML4313 was obtained from a patient from intensive care unit of Military hospital in Tunisia. This strain was resistant to beta-lactams, aminoglycosides, quinolones and phenicols, and tetracyclines. It was identified as producer of extended-spectrum beta-lactamases (ESBL) by double-disk synergy test between amoxicillin-clavulanate and cefotaxime, ceftriaxone, ceftazidime and aztreonam. The ESBL was identified as CTX-M-28 by sequencing of PCR products and by isoelectric focusing. The ESBL resistance was transferred by a 50kb plasmid. CTX-M-28 is closely related to CTX-M-15. This is the first description of this enzyme in Tunisia.
Assuntos
Proteínas de Bactérias/genética , Cefotaxima/farmacologia , Farmacorresistência Bacteriana Múltipla/genética , Infecções por Klebsiella/microbiologia , Klebsiella pneumoniae/isolamento & purificação , Resistência beta-Lactâmica , beta-Lactamases/genética , Sequência de Aminoácidos , Substituição de Aminoácidos , Proteínas de Bactérias/química , Infecção Hospitalar/epidemiologia , Infecção Hospitalar/microbiologia , DNA Bacteriano/genética , Hospitais Militares , Humanos , Unidades de Terapia Intensiva , Infecções por Klebsiella/epidemiologia , Klebsiella pneumoniae/classificação , Klebsiella pneumoniae/genética , Dados de Sequência Molecular , Mutação de Sentido Incorreto , Fatores R/genética , Alinhamento de Sequência , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Tunísia/epidemiologia , Resistência beta-Lactâmica/genética , beta-Lactamases/químicaRESUMO
The clinical isolate, Escherichia coli 1941, exhibits high resistance to chloramphenicol and tetracycline (minimum inhibitory concentrations of 512 micrograms/ml). Neither resistance is linked to the large conjugative plasmid present in the strain. The intracellular accumulation of radiolabeled chloramphenicol increased about 9-fold after the addition of the energy uncoupler carbonyl cyanide m-chlorophenol-hydrazone to an E. coli 1941 culture, indicating the presence of an active efflux mechanism. Sequence analysis and expression study suggested that the multiple-antibiotic resistance marRAB locus and the AcrAB drug-efflux pump were not involved in this active efflux of chloramphenicol.
Assuntos
Antibacterianos/metabolismo , Proteínas de Transporte , Resistência ao Cloranfenicol/fisiologia , Cloranfenicol/metabolismo , Infecções por Escherichia coli/microbiologia , Escherichia coli/metabolismo , Primers do DNA , DNA Bacteriano/genética , Proteínas de Ligação a DNA/genética , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Lipoproteínas/genética , Proteínas de Membrana/genética , Proteínas de Membrana Transportadoras , Testes de Sensibilidade Microbiana , Proteínas Associadas à Resistência a Múltiplos Medicamentos , Plasmídeos/genética , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
The role of chromosomal cephalosporinases and secondary beta-lactamases in resistance to extended spectrum cephalosporins in clinical isolates of Pseudomonas aeruginosa was investigated. Strains 687, 59, and 58 expressed an inducible chromosomal cephalosporinase, efficiently enhanced with cefoxitin and imipenem. The inducible activity in strain 802 was produced at a moderately elevated basal level and may be involved in resistance to extended spectrum cephalosporins and aztreonam. All strains produced secondary beta-lactamases inhibited by clavulanate: strains 687, 59, and 58 had carbenicillinases with pIs of 5.7 and 5.3. Strain 802 expressed a secondary beta-lactamase of pI 7.6 which may be a novel extended spectrum beta-lactamase different from known enzymes of P. aeruginosa.
Assuntos
Cefotaxima/farmacologia , Ceftazidima/farmacologia , Ceftriaxona/farmacologia , Resistência às Cefalosporinas , Cefalosporinase/biossíntese , Pseudomonas aeruginosa/efeitos dos fármacos , Pseudomonas aeruginosa/enzimologia , beta-Lactamases/biossíntese , Cefotaxima/metabolismo , Ceftazidima/metabolismo , Ceftriaxona/metabolismo , Indução Enzimática , Humanos , Focalização Isoelétrica , Testes de Sensibilidade MicrobianaRESUMO
Escherichia coli 2418 strain is resistant to beta-lactam antibiotics (ampicillin, carbenicillin, and cephalothin), streptomycin, tetracycline, kanamycin, and chloramphenicol. This strain contains at least two conjugative plasmids (R2418 and R2418S) encoding resistance to beta lactam antibiotics and resistance to both beta-lactam antibiotics and streptomycin, respectively. Restriction endonuclease mapping of plasmid DNAs indicates that the plasmid R2418S has evolved from R2418 DNA by the insertion of 2.5-kb DNA between BamHI and PvuII sites, and deletion of 0.5-kb DNA within the EcoRI-EcoRV region. The 2.5-kb DNA insert is responsible for streptomycin resistance. This evolution is also associated with a reduction in the efficiency of conjugal transfer for the plasmid R2418S. The conjugal transfer of streptomycin resistance occurs only through the coresidence of the conjugative plasmid R2418 or R2418S in the donor cell. In accordance with the hypothesis that the Smr determinant is due to a putative transposon, plasmid-free transconjugants resistant to streptomycin only were isolated. Southern blot analysis of HindIII chromosomal digests extracted from these transconjugants shows that the Smr determinant is inserted into different sites in chromosomal DNA.