A comparison of the mechanisms of decreased susceptibility of aztreonam-resistant and ceftazidime-resistant Enterobacteriaceae

Piddock, Laura J. V.; Traynor, E. A.; Wise, R.

doi:10.1093/jac/26.6.749

Cited by 21 publications

(23 citation statements)

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“…Preparation of outer membrane protein (Omp) from clinical isolates and separation of the proteins by sodium dodecyl sulfate-10% polyacrylamide gel electrophoresis (acrylamide-bis, 30:3) and 8 M urea were performed according to the method of Piddock et al (20).…”

Section: Methodsmentioning

confidence: 99%

Outbreak of Infection with Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae in a Mexican Hospital

et al. 2001

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Thirty-one strains of Klebsiella pneumoniae (including 10 duplicates) from 21 septicemic pediatric patients (age, <2 months) were studied during a 4-month period (June to October 1996) in which the fatality rate was 62% (13 of 21). These isolates identified by the API 20E system yielded the same biotype. Pulsed-field gel electrophoresis experiments revealed the same clone in 31 strains. The isolates were multidrug-resistant but were still susceptible to ciprofloxacin, imipenem, and cefoxitin. A 135-kb plasmid was harbored in all of the isolates. No transconjugants were obtained that were resistant to ampicillin, cefotaxime, tetracycline, or gentamicin. Isoelectric focusing for ␤-lactamases was performed on all strains, and three bands with pIs of 5.4, 7.6, and 8.2 were obtained. Of these, the pI 8.2 ␤-lactamase had an extended-spectrum ␤-lactamase phenotype. PCR amplification of both TEM-and SHV-type genes was obtained. The sequence analysis of the SHV PCR product indicated a mutation corresponding to the SHV-5 ␤-lactamase.Klebsiella pneumoniae is an important hospital-acquired pathogen with the potential of causing severe morbidity and mortality in pediatric patients. Several outbreaks of infection caused by K. pneumoniae isolates that are simultaneously resistant to broad-spectrum cephalosporins and aminoglycosides have been widely reported (8,9,18,21). Some of these multidrug-resistant isolates produce extended-spectrum ␤-lactamases (ESBLs) that are able to hydrolyze expanded-spectrum cephalosporins (e.g., ceftriaxone, cefotaxime, and ceftazidime), aztreonam, and related oxyimino-␤-lactams. Most of these enzymes are TEM-or SHV-type ␤-lactamases in which the substitution of one or more amino acids has altered the configuration of the active site (7,14,19). Most of the plasmids determining ESBLs are large (Ն80 kb) and encode multiple resistances (10). Little is known about the ESBL-producing Enterobacteriaceae in Mexico (23). The present work is a characterization of 31 ESBL-producing K. pneumoniae isolates from a nosocomial outbreak occurring in a hospital in Cuernavaca, Mexico. MATERIALS AND METHODSPatients and bacterial strains. The General Hospital in the state of Morelos is a secondary-care facility with 100 beds. The neonatal intensive care unit has 8 beds. An outbreak was suspected in the neonatal intensive care unit due to an increased number of isolates of K. pneumoniae from blood cultures during a 4-month period. A retrospective epidemiological investigation included 74 children less than 2 months old hospitalized from June to October 1996.Twenty-one clinical isolates were from blood; another 10 duplicate strains were from sites other than blood (urine and catheter tip) corresponding to 10 patients. In total there were 31 clinical isolates identified as K. pneumoniae by the API 20E system (BioMerieux, Merck).Susceptibility testing. The antimicrobial susceptibility was initially determined with the MicroScan (Dade) system, using the Combo 14 panel. Subsequently, MICs of several ␤-lactams were determine...

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Section: Methodsmentioning

confidence: 99%

Outbreak of Infection with Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae in a Mexican Hospital

et al. 2001

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“…The kinetics of f-lactamase hydrolysis were analyzed from noninduced cells using nitrocefin as a substrate, and the Km and Vmaz were calculated. All assays were performed at 37°C using an LKB Ultrospec with a heated cell, and the data were analyzed as described by Piddock et al (29). Inducibility was examined by the zone blunting method (35).…”

Section: Materlals and Methodsmentioning

confidence: 99%

A pleiotropic, posttherapy, enoxacin-resistant mutant of Pseudomonas aeruginosa

Piddock

Hall

Bellido

et al. 1992

Antimicrob Agents Chemother

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An enoxacin-resistant Pseudomonas aeruginosa mutant (G49) isolated during patient therapy was characterized in detail. The G49 mutant was cross resistant to several classes of antibiotics including quinolones, I-lactams, chloramphenicol, and tetracycline, but not imipenem or aminoglycosides. Compared with its paired pretherapy isolate G48, this mutant had several alterations in outer membrane proteins including a complete loss of the major porin protein OprF and a substantially altered lipopolysaccharide profile. Revertants were selected at a frequency of approximately 1% after enrichment for OprF+ cells on low-salt proteose peptone no. 2 medium. Ninety-seven of these OprF+ revertants were as susceptible to carbenicillin and norfloxacin as the pretherapy isolate. One of these revertants was characterized in more detail and shown to be indistinguishable in all properties from the pretherapy isolate. It is proposed that the multiple-antibiotic-resistance (Mar) phenotype of this mutant resulted from a single pleiotropic mutation.Enoxacin is a difluorinated quinolone with strong activity for gram-negative bacteria (7,41). Enoxacin is now marketed in 11 countries, including South America, the United Kingdom, and other parts of Europe, for use in the therapy of urinary tract infections and in some countries for respiratory tract infections. As in other bacteria, the primary target for quinolones in Pseudomonas aeruginosa is DNA gyrase. nalA, nfxA, norA, and cipA are alleles ofgyrA and encode A subunits that are less susceptible to inhibition by quinolones (14,16,33,34). Other mutations affecting quinolone activity, but not DNA gyrase, in P. aeruginosa have also been described. Many laboratory mutants contain alleles of nalB and require nalidixic acid MICs of >500 ,ug/ml and are cross resistant to carbenicillin, ureidopenicillins, chloramphenicol, and novobiocin (33, 34). Resistant strains have arisen during experimental P. aeruginosa infections, with several classes of mutants isolated with mutations resembling naL4 and nfxC (10,22,23). Quinolone-resistant P. aeruginosa isolated from patients may also have the nal4 or nalB phenotype (43) or a nalB-like phenotype lacking OprF. Such strains have been isolated from patients with chronic obstructive airway disease (30), burn wound sepsis (17), cystic fibrosis (6), and empyema (20). While several strains with decreased susceptibilities to several agents have been isolated, which suggests a mutation in nalB, there are biochemical differences that are commensurate with different mutations encoding multiple resistance. Some quinolone-resistant P. aeruginosa strains contain a new 54-kDa outer membrane protein (14, 18) or lack a 31.5-kDa outer membrane protein (9, 17), possibly OprF, or have decreased levels of proteins D2 and Hi or Gl (5,20,23). Several workers have also reported changes in lipopolysaccharide (LPS) (6,18,34).An open study to evaluate the efficacy of enoxacin in respiratory tract infections with particular attention to those caused by P. aeruginosa was perform...

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“…Spots of interest were excised and analysed by tryptic fragment digestion and MS, using an Applied Biosystems Voyager DE-STR MALDI-TOF mass spectrometer. Outer-membrane samples of MJF543 and MJF544 were prepared during exponential growth in defined medium as described by Piddock et al (1990).…”

Section: Strainsmentioning

confidence: 99%

“…Reproducible (nl3) changes in the levels of three separate spots whose intensities exhibited major differences were observed in protein pattern of MJF544 compared to that of MJF543. In the mutant strains one c) Outer-membrane fractions were also prepared from exponentially growing cultures as described in Piddock et al (1990). Outer-membrane fractions from MJF543 (lane 1) and MJF544 (lane 2) were analysed by 1D SDS-PAGE.…”

Section: Deletion Of the Trub Gene Affects The Levels Of Key Outer-mementioning

confidence: 99%

Physiological analysis of the role of truB in Escherichia coli: a role for tRNA modification in extreme temperature resistance

et al. 2002

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The truB gene of Escherichia coli encodes the pseudouridine-55 (ψ55) synthase and is responsible for modifying all tRNA molecules in the cell at the U55 position. A truB null mutant grew normally on all growth media tested, but exhibited a competitive disadvantage in extended co-culture with its wild-type progenitor. The mutant phenotype could be complemented by both the cloned truB gene and by a D48C, catalytically inactive allele of truB. The truB mutant also exhibited a defect in survival of rapid transfer from 37 to 50 SC. This mutant phenotype could be complemented by the cloned truB gene but not by a D48C, catalytically inactive allele of truB. The temperature sensitivity of truB mutants could be enhanced by combination with a mutation in the trmA gene, encoding an m 5 U-methyltransferase, modifying the universal U54 tRNA nucleoside, but not by mutations in trmH, encoding the enzyme catalysing the formation of Gm18. The truB mutant proteome contained altered levels of intermediates involved in biogenesis of the outer-membrane proteins OmpA and OmpX. The truB mutation also reduced the basal expression from two σ E promoters, degP and rpoHP3. Three novel aspects to the phenotype of truB mutants were identified. Importantly the data support the hypothesis that TruB-effected ψ55 modification of tRNA is not essential, but contributes to thermal stress tolerance in E. coli, possibly by optimizing the stability of the tRNA population at high temperatures.

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A comparison of the mechanisms of decreased susceptibility of aztreonam-resistant and ceftazidime-resistant Enterobacteriaceae

Cited by 21 publications

References 0 publications

Outbreak of Infection with Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae in a Mexican Hospital

Outbreak of Infection with Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae in a Mexican Hospital

A pleiotropic, posttherapy, enoxacin-resistant mutant of Pseudomonas aeruginosa

Physiological analysis of the role of truB in Escherichia coli: a role for tRNA modification in extreme temperature resistance

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