Modified Peptidoglycan Transpeptidase Activity in a Carbenicillin-Resistant Mutant of
            <i>Pseudomonas aeruginosa</i>
            18s

Curtis, Nigel A. C.; Brown, C.G.; Boxall, Mike; Boulton, Mike G.

doi:10.1128/aac.14.2.246

Cited by 14 publications

(9 citation statements)

References 20 publications

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“…Stably derepressed mutants were selected from inducible strains on Diagnostic Sensitivity Test agar (Oxoid Ltd., Basingstoke, Hants, United Kingdom) containing cefotaxime (1 or 4 ,ug/ml) by the procedure described previously (24). 1-Lactamase basal mutants (those with low-level uninducible 13-lactamase expression) were derived from the stably derepressed organisms by mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine (2 P-Lactamase induction assays. Induction assays were performed by exposure of logarithmic-phase cells to antibiotics in Iso-Sensitest broth (Oxoid) for 4 h, as described previously (24).…”

Section: Methodsmentioning

confidence: 99%

Chromosomal beta-lactamase expression and resistance to beta-lactam antibiotics in Proteus vulgaris and Morganella morganii

Yang

Livermore

1988

Antimicrob Agents Chemother

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Indole-positive members of the Proteeae usually have inducible expression of chromosomal ,-lactamases.Mutants with stably derepressed P-lactamase expression occur in inducible populations at frequencies in the range of 10-6 to 10-8. The contribution of these P-lactamases to drug resistance was examined in Morganella morganii and Proteus vulgaris. The M. morganii enzyme was a high-molecular-weight (49,000) class I cephalosporinase with low Vm.x rates for ampicillin, carbenicillin, and broad-spectrum cephalosporins. The P.vulgaris enzyme had a lower molecular weight (32,000) and high Vmax rates for ampicillin, cephaloridine, cefotaxime, and ceftriaxone. Imipenem and cefoxitin inactivated the P. vulgaris enzyme but were low-Vmax, low-Km substrates for that of M. morganii. Despite these differences, the two I-lactamases caused similar resistance profiles. Ampicillin and cephaloridine were strong inducers for both species, and ,I-lactamaseinducible strains and their stably derepressed mutants were resistant, whereas basal mutants (those with low-level uninducible P-lactamase) were susceptible to these two compounds. Mezlocillin, cefotaxime, ceftriaxone, and (usually) carbenicillin were almost equally active against P-lactamase-inducible organisms and their basal mutants, but were less active against stably derepressed mutants. This behavior reflected the P-lactamase lability of these drugs, coupled with their weak inducer activity below the MIC. Carbenicillin was a labile strong inducer for a single P. vulgaris strain, and inducible enzyme was protective against the drug in this atypical organism. Cefoxitin and imipenem, both strong inducers below the MIC, were almost equally active against P-lactamase-inducible organisms and their basal and stably derepressed mutants.

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Section: Methodsmentioning

confidence: 99%

Chromosomal beta-lactamase expression and resistance to beta-lactam antibiotics in Proteus vulgaris and Morganella morganii

Yang

Livermore

1988

Antimicrob Agents Chemother

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“…The colonies that grew on this medium after overnight incubation at 37°C were subculturedon antibiotic-free DST agar, and then characterised. /I-Lactamase-basal mutants were derived from stablyderepressed organisms by mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine (Curtis et al, 1978).…”

Section: E Cloacae Strainsmentioning

confidence: 99%

Chromosomal -lactamase expression and antibiotic resistance in Enterobacter cloacae

Yang

Livermore

Williams

1988

Journal of Medical Microbiology

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Summary. The activities of P-lactam antibiotics were compared against Enterobacter cloacae clinical isolates and mutants which had inducible, stably-derepressed, and basal expression of a PI 8.4 subtype of the Ia chromosomal P-lactamase. These activities were correlated with the results of studies of the P-lactamase-lability and /?-lactamase-inducer-power of the antibiotics. Cefoxitin and ampicillin were labile, and induced p-lactamase production strongly at concentrations below their MIC values. Consequently, /?-lactamase-inducible and p-lactamase-stably-derepressed organisms were highly resistant (MIC > 256 mg/L) to these antibiotics, whereas enzyme-basal strains and mutants were much more susceptible (MIC 1-16 mg/L). Imipenem also induced p-lactamase production strongly at concentrations below its MIC, but was more stable than ampicillin and cefoxitin. It was active against enzyme-inducible and stably-derepressed organisms at 0-25-0.5 mg/L and against P-lactamase-basal organisms at 0.06-0-25 mg/L. Thus the P-lactamase afforded only very low-level protection against imipenem ; this appeared to be by a non-hydrolytic mechanism, with the enzyme binding to the antibiotic in a relatively stable complex. This complex, which probably was an intermediate in a hydrolytic pathway, was isolated by gelfiltration chromatography and shown to have a breakdown half-life of 47 f 2 min. Cefotaxime, ceftriaxone and mezlocillin were labile to the PI 8.4 P-lactamase but induced p-lactamase production weakly at concentrations below their MIC values. Consequently, P-lactamase-inducible and P-lactamase-basal organisms remained equally susceptible (MIC 0.06-4 mg/L), but stably-derepressed organisms were considerably more resistant (MIC > 64 mg/L) to these antibiotics.

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“…aerogenes K1-and P. rettgeri 17/1 were mutants of K. aerogenes 1082E (5) and P. rettgeri 1793E (16) selected for lack of f,-lactamase production, after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine, using the chromogenic cephalosporin 87/312 (8) as described previously (1).…”

mentioning

confidence: 99%

“…MATERIALS AND METHODS E. coli DCO (2), P. aeruginosa 18sSAI- (1), and E. cloacae P99-(3) have been described previously. K.…”

mentioning

confidence: 99%

Competition of beta-lactam antibiotics for the penicillin-binding proteins of Pseudomonas aeruginosa, Enterobacter cloacae, Klebsiella aerogenes, Proteus rettgeri, and Escherichia coli: comparison with antibacterial activity and effects upon bacterial morphology

Curtis¹,

Orr²,

Ross³

et al. 1979

Antimicrob Agents Chemother

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The competition of a number of beta-lactam morphogenic probes for the penicillin-binding proteins (PBPs) of Pseudomonas aeruginosa, Enterobacter cloacae, Klebsiella aerogenes, Proteus rettgeri, and Escherichia coli has been studied. The results indicate that the various gram-negative bacteria have similar, but not identical, PBP patterns and that the individual proteins probably perform similar morphogenic functions as in E. coli K-12. Comparison of the 50% binding concentrations of the compounds for the various PBPs of the five strains with their antibacterial activity indicates that the different antibiotics are excluded to a greater or lesser degree by the outer membrane permeability barrier and that the exclusion is most pronounced in P. aeruginosa.

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Modified Peptidoglycan Transpeptidase Activity in a Carbenicillin-Resistant Mutant of Pseudomonas aeruginosa 18s

Cited by 14 publications

References 20 publications

Chromosomal beta-lactamase expression and resistance to beta-lactam antibiotics in Proteus vulgaris and Morganella morganii

Chromosomal beta-lactamase expression and resistance to beta-lactam antibiotics in Proteus vulgaris and Morganella morganii

Chromosomal -lactamase expression and antibiotic resistance in Enterobacter cloacae

Competition of beta-lactam antibiotics for the penicillin-binding proteins of Pseudomonas aeruginosa, Enterobacter cloacae, Klebsiella aerogenes, Proteus rettgeri, and Escherichia coli: comparison with antibacterial activity and effects upon bacterial morphology

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