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P Kontomichalou

Publications and source records attributed to P Kontomichalou.

17 recordsLinked to original sources
PubMed1982

Purification and properties of two gentamicin-modifying enzymes, coded by a single plasmid pPK237 originating from Pseudomonas aeruginosa.

A broad host range multiresistance plasmid pPK237, originating from Pseudomonas aeruginosa mediates high-level resistance to gentamicin and tobramycin. It was found to code for two gentamicin modifying enzymes, which from their substrate profile by radioenzymatic assay were characterized as aminoglycoside acetyltransferase AAC(3)-I and aminoglycoside adenylyltransferase AAD(2"). The two enzymes were studied after purification from an Escherichia coli K12 host. The two gentamicin-modifying enzymes coded by PPK237 were completely separated by DEAE chromatography. The purification (126 fold) of the acetyltransferase was achieved by (NH4)2SO4 precipitation, DEAE chromatography and affinity chromatography. The purification of the adenylyltransferase was performed by affinity chromatography directly after (NH4)2SO4 precipitation. Both purified enzyme preparations showed a single protein band on disc electrophoresis. The Km for gentamicin C1 of the acetyltransferase was 0.066 mM. The amino acid analysis of the acetyltransferase coded by pPK237 showed a different aminoacid composition than that of the gentamicin acetyltransferase AAC(3)-I purified by Williams and Northrop17). The acetyltransferase after DEAE chromatography is stable for many months at -20 degrees C, while the adenylyltransferase after purification is highly unstable; it shows enzymatic activity only in the presence of Mg++.

Acetyltransferases↗
PubMed1982

Amoxicillin and clavulanic acid combination: clinical and laboratory evaluation in pulmonary infections.

Twenty-four patients with pulmonary infections (7 pneumoniae, 17 exacerbations of chronic bronchitis) were treated with a combination of 250 mg of amoxicillin and 125 mg of clavulanic acid supplemented by 500 mg of amoxicillin every eight hours. All patients showed good clinical, roentgenological, and bacteriological response. Bacteria were cleared from sputum by the third day of treatment in half of the patients and by the end of treatment in all but one of the others. Pathogens eradicated from sputum, with concurrent clinical cure, included gram-negative bacteria producing cephalosporinases shown to be resistant to the combination drug by both disk and minimal inhibitory concentration determinations.

Adult↗
PubMed1981

Cefotaxime: clinical and bacteriologic evaluation.

Cefotaxime, a new parenteral beta-lactamase-resistant cephalosporin, was tested against 78 cephalothin-resistant clinical isolates of Enterobacteriaceae and Pseudomonas species. The anti-bacterial activity of the drug was compared with activities of cefazolin and cefuroxime and was found considerably more active. Most of the cephalothin-resistant strains were resistant to cephazin, too. The antipseudomonal activity of cefotaxime was found limited. The drug was found effective against 23 infections in hospitalized patients with only one clinical failure and two colonizations with cefotaxime-resistant bacteria. Cephalosporinases hydrolyzing cefotaxime were detected in two cefotaxime-resistant strains. Also, beta-lactamases hydrolyzing cefoxitin and cefuroxime were produced by the cefotaxime-resistant isolates studied.

Aged↗
PubMed1976

Multiresistant plasmids from Pseudomonas aeruginosa highly resistant to either or both gentamicin and carbenicillin.

High-level resistance to gentamicin and carbenicillin was found in 30 and 10.7%, respectively, of Pseudomonas aeruginosa strains, especially in isolates from urine. In 23 out of 25 strains tested, these resistances were R mediated and linked to multiresistant plasmids, carrying genes for resistances to five other aminoglycosides, tobramycin, kanamycin, neomycin, streptomycin, and spectinomycin, and for resistances to chloramphenicol, tetracycline, sulfonamides, and mercury chloride. Carbenicillin resistance was unstable in Pseudomonas, and in its presence the multiresistant plasmids had a host range extended to the Enterobacteriaceae (group I plasmids). Otherwise they were transferable intragenerically only (group II plasmids). The extended host range plasmids were, as a rule, in fi(-) incompatibility class A-C. Segregants incompatible with both class A-C and P plasmids were detected. The beta-lactamase specified by the carbenicillin marker was of the TEM-like type. Multiple linkages of resistance determinants to the aminoglycosides were concomitantly present in most of the plasmids. Results from the bioassay indicated the presence of at least two aminoglycoside-inactivating enzymes.

Anti-Bacterial Agents↗
PubMed1976

Plasmid-determined beta-lactamase indistinguishable from the chromosomal beta-lactamase of Escherichia coli.

A plasmid, derived from a naturally occurring strain of Proteus mirabilis, conferred resistance to cephalosporins, apparently mediated by a beta-lactamase indistinguishable from that determined by the chromosomal gene of Escherichia coli K-12. There was evidence for a recombination event between the wild-type plasmid and a defective F factor (Fsp) in the Escherichia coli K-12 culture in which it was stored.

Cephalosporins↗
PubMed1974

Molecular specificities of R factor-determined beta-lactamases: correlation with plasmid compatibility.

Beta (beta)-lactamases determined by 29 ampicillin resistance plasmids could be divided into two types. One, TEM-type, was very uniform with respect to substrate specificity but heterogeneous in absolute levels of beta-lactamase activity. The TEM-type beta-lactamase was determined by R factors of compatibility groups FII, Ialpha, Iepsilon, N, C, A, T, W, P, L, and X, and by prophage phi Amp. The other type, characterized by the ability to hydrolyze oxacillin, was less common, showed lower absolute levels of activity, and was heterogeneous as regards substrate specificities. Oxacillin-hydrolyzing beta-lactamases were determined by R factors of compatibility groups FI, Ialpha, N, C, and O.

Ampicillin↗
PubMed1970

Circular R-factor molecules controlling penicillinase synthesis, replicating in Escherichia coli under either relaxed or stringent control.

Two infectious drug-resistance (R) factors, R28K and R6K, each conferring resistance to a number of penicillins by the synthesis of a penicillinase, were transferred to Proteus mirabilis PM1 and Escherichia coli RC85 host strains. Deoxyribonucleic acid (DNA) extracted from these strains was separated by density-gradient centrifugation and subjected to electron microscopy by use of a modification of the protein-monolayer diffusion technique. Analytical density-gradient centrifugation of the purified DNA from PM1 strains showed, in addition to the major peak at a density of 1.698 g/cm(3) characteristic of Proteus chromosomal DNA, a single satellite band at a density of 1.710 g/cm(3) [guanine plus cytosine (GC) base ratio 50%] for R28K and at 1.704 g/cm(3) (GC base ratio 45%) for R6K. Direct CsCl density-gradient centrifugation of crude lysates of the E. coli (R28K)(+) strain in the presence of ethidium bromide gave rise to a sedimentation profile with a single satellite peak containing covalently closed circular (CCC) DNA molecules with a mean contour length of 21.4 mum [44 x 10(6) atomic mass units (AMU)], although a minority was 13.6 mum in length. From the size of the major class, it was estimated that there were two to three copies of the R28K factor present as CCC molecules per chromosome at various phases of cellular growth. Similar studies of the E. coli (R6K)(+) lysates showed two satellite peaks; peak I contained mostly CCC molecules of contour length 12.8 mum (26 x 10(6) AMU), and peak II, intermediate to peak I and the chromosomal peak, contained CCC molecules of a similar size, together with about equal numbers of catenated molecules, mostly dimers consisting of two interlocked monomers of 12.8 mum. A smaller number (ca. 0.1%) of higher catenanes was also seen. The number of CCC copies of the R6K factor per chromosome present in peak I was calculated as 13 at logarithmic phase and 38 at stationary phase. In peak II, a constant ratio of about one catenated dimer per chromosome was found at all phases of growth. Penicillinase assays of cultures at different phases of growth showed a correlation between the estimated number of R-factor copies present as CCC molecules and the enzyme activity per cell for both R28K and R6K.

Ampicillin↗