Biomedical subjects

M Perilli

Publications and source records attributed to M Perilli.

At least 37 records · Page 2Linked to original sources

PubMed1997

Does poly(ADP-ribosyl)ation regulate the DNA methylation pattern?

The existence of a possible correlation between poly(ADP-ribosyl)ation and DNA methylation processes was investigated. In vivo and in vitro experiments were carried out on L929 mouse fibroblasts preincubated for 24 h with or without 3-aminobenzamide, a well-known inhibitor of poly(ADP-ribose) polymerase. Both experimental approaches evidenced a close relationship between these two important nuclear enzymatic mechanisms, suggesting that the poly(ADP-ribosyl)ated isoform of H1 histone and/or long and branched protein-free ADP-ribose polymers could act as protecting agents against full methylation of the CpG dinucleotides in genomic DNA.

Animals↗

PubMed1997

Characterization of a new TEM-derived beta-lactamase produced in a Serratia marcescens strain.

A natural TEM variant beta-lactamase was isolated from an epidemic strain of Serratia marcescens. Nucleotide gene sequencing revealed multiple point mutations located in the 42-to-44 tripeptide and positions 145 to 146, 178, and 238. In addition, a glutamic acid 212 deletion was also found. The purified enzyme was studied from a kinetic point of view, revealing the highest catalytic efficiency (k[cat]/Km) values for ceftazidime and aztreonam compared with the TEM-1 prototype enzyme. The in vitro resistance correlated with kinetic parameters, and the enzyme also mediated resistance to some penicillins and an ampicillin-clavulanic acid combination. The mutational and kinetic changes are discussed in relation to the three-dimensional crystallographic structure of the wild-type TEM-1 enzyme.

Amino Acid Sequence↗

PubMed1997

Sensitivity of Aeromonas hydrophila carbapenemase to delta3-cephems: comparative study with other metallo-beta-lactamases.

Ceftriaxone and ceftriaxone S-oxide behaved as inactivators against the metallo-beta-lactamase of Aeromonas hydrophila AE036 and as substrates for the zinc beta-lactamase produced by Bacillus cereus (569/H/9) and Stenotrophomonas maltophilia ULA 511. Moreover, RO 09-1428, a catechol-cephalosporin, was not recognized by the A. hydrophila enzyme. Panipenem, cephalosporin C, cephalosporin C-gamma-lactone, and loracarbef were substrates for the three studied beta-lactamases.

Aeromonas hydrophila↗

PubMed1996

Overproduction and purification of the Aeromonas hydrophila CphA metallo-beta-lactamase expressed in Escherichia coli.

The Aeromonas hydrophila CphA metallo-beta-lactamase was overexpressed in a soluble secreted form in Escherichia coli using a T7 RNA polymerase-based expression system, and a simple protocol based on a single cation-exchange chromatographic step was developed, which is suitable for rapid purification of the overexpressed enzyme from E. coli lysates. A yield of up to 30 micrograms of purified enzyme per milliliter of culture was obtained. The purified enzyme preparation showed properties identical to those previously reported in the literature.

Aeromonas hydrophila↗

PubMed1996

Characterization of the chromosomal cephalosporinases produced by Acinetobacter lwoffii and Acinetobacter baumannii clinical isolates.

The beta-lactamases produced by Acinetobacter lwoffii ULA-501, Acinetobacter baumannii ULA-187, and A. baumannii AC-14 strains were purified and characterized, and their kinetic interactions with several beta-lactam molecules, including substrates and inhibitors, were studied in detail. The three enzymes appeared to be cephalosporinases with different acylation efficiencies (kcat/Km ratio values), and their hydrolytic activities were inhibited by benzylpenicillin, piperacillin, and cefotaxime, which did not behave as substrates. Carbenicillin was a substrate for the beta-lactamase from A. lwoffii ULA-501, whereas it acted as a transient inactivator of the enzymes produced by the two A. baumannii strains. Clavulanic acid was unable to inactivate the three beta-lactamases, whereas sulbactam behaved as an inactivator only at a high concentration (1 mM) which is difficult to achieve during antibiotic therapy. Analysis of the interaction with 6-beta-iodopenicillanic acid also allowed us to better discriminate the three beta-lactamases analyzed in the present study, which can be included in the group 1 functional class (5).

Acinetobacter↗

PubMed1995

Interactions of biapenem with active-site serine and metallo-beta-lactamases.

Biapenem, formerly LJC 10,627 or L-627, a carbapenem antibiotic, was studied in its interactions with 12 beta-lactamases belonging to the four molecular classes proposed by R. P. Ambler (Philos. Trans. R. Soc. Lond. Biol. Sci. 289:321-331, 1980). Kinetic parameters were determined. Biapenem was readily inactivated by metallo-beta-lactamases but behaved as a transient inhibitor of the active-site serine enzymes tested, although with different acylation efficiency values. Class A and class D beta-lactamases were unable to confer in vitro resistance toward this carbapenem antibiotic. Surprisingly, the same situation was found in the case of class B enzymes from Aeromonas hydrophila AE036 and Bacillus cereus 5/B/6 when expressed in Escherichia coli strains.

Binding Sites↗

PubMed1993

In vitro activity of cefodizime (HR-221) in combination with beta-lactamase inhibitors.

Cefodizime (formerly HR221) was tested either for in vitro microbiological activity or for its stability to beta-lactamases in the presence of two beta-lactamase inhibitors (clavulanic acid, tazobactam). Cefodizime was a poor substrate of class C enzymes but hyperproducer strains were generally resistant with or without a beta-lactamase inhibitor used in combination. On the contrary, class A enzymes were able to hydrolyze cefodizime. However, strains expressing class A beta-lactamase were susceptible to cefodizime in combination with clavulanic acid.

Anti-Bacterial Agents↗

PubMed1991

Cloning and nucleotide sequencing of the gene encoding the beta-lactamase from Citrobacter diversus.

The gene coding for the class A beta-lactamase of Citrobacter diversus has been cloned and sequenced. It contains the information for a 294-amino-acid precursor protein, including a 27-residue N-terminal signal peptide. The deduced sequence of the N-terminal portion of the mature protein is in excellent agreement with that determined by microsequencing of the protein and readily explains the pI differences observed between the naturally occurring forms I and II of the enzyme. The sequence of the mature protein exhibits a very high degree of similarity with that of the Klebsiella oxytoca class A beta-lactamase.

Amino Acid Sequence↗

PubMed1991

Proteolytic interconversion and N-terminal sequences of the Citrobacter diversus major beta-lactamases.

The N-terminal sequences of the two major beta-lactamases produced by Citrobacter diversus differed only by the absence of the first residue in form II and the loss of five amino acid residues at the C-terminal end. Limited proteolysis of the homogeneous form I protein yielded a variety of enzymatically active products. In the major product obtained after the action of papain, the first three N-terminal residues of form I had been cleaved, whereas at the C-terminal end the treated enzyme lacked five residues. However, this cannot explain the different behaviours of form I, form II and papain digestion product upon chromatofocusing. Form I, which was sequenced up to position 56, exhibited a very high degree of similarity with a Klebsiella oxytoca beta-lactamase. The determined sequence, which contained the active serine residue, demonstrated that the chromosome-encoded beta-lactamase of Citrobacter diversus belong to class A.

Amino Acid Sequence↗

PubMed1990

CTX and its desacetyl derivative (des-CTX): interaction with some representative beta-lactamases and their related pattern of resistance to newer selected clinical isolates.

In this study the kinetic features of cefotaxime (CTX) and desacetyl-cefotaxime towards several representative beta-lactamases were investigated. Desacetyl-CTX was more stable to hydrolysis in comparison with cefotaxime for all the investigated enzymes. However, a cephalosporinase produced in Acinetobacter was progressively inactivated by both CTX and des-CTX. After prolonged incubation, dialysis partially restored the enzyme activity. Finally, both compounds were tested against selected resistant strains. It is concluded that des-CTX, because of either poor hydrolysis or prolonged half-life in body fluids, could contribute in vivo to the good antimicrobial properties of cefotaxime.

Anti-Bacterial Agents↗

PubMed1989

The beta-lactamases of Citrobacter diversus and their hydrolysis kinetics for some structurally-related cephalosporins.

We measured the kinetics of hydrolysis of various cephalosporins by the chromosomally-encoded beta-lactamases of Citrobacter diversus ULA-27. Cefonicid, cefamandole, cefatrizine and cefoperazone were all hydrolyzed but these antibiotics showed a different feature in their kinetic parameters. Moreover, cefoperazone was a non-competitive inhibitor of this type of enzyme. Cefotetan was stable to hydrolysis and behaved like a progressive inactivator. The ability of these enzymes to inactivate the reported antibiotics contributes largely to the resistance of the studied strain. We conclude that hydrolysis is the main mechanism of resistance of this strain to the new cephalosporins.

Cell Cycle↗

PubMedDate not supplied

In vitro activity of piperacillin/tazobactam against 615 Pseudomonas aeruginosa strains isolated in intensive care units.

From May 1996 to September 1997, 615 Pseudomonas aeruginosa strains isolated from patients in intensive care units collected from different Italian laboratories were studied. The susceptibility of piperacillin/tazobactam, in comparison with other antipseudomonal antibiotics, to their NCCLS breakpoints was evaluated: amikacin 79. 6%, carbenicillin 67.0%, ceftazidime 73.4%, ciprofloxacin 55.8%, imipenem 64.1%, piperacillin 88.1%, piperacillin/tazobactam 92.4% and ticarcillin/clavulanic acid 69.0%. Seventy-three strains were selected because of their resistance to piperacillin and the mechanisms underlying such a resistance were investigated. Isoelectric focusing and hydrolysis assays revealed the presence of 15 plasmid-mediated beta-lactamases. Chromosomal beta-lactamase derepression was demonstrated in 34 isolates. The remaining 24 piperacillin-resistant strains did not produce beta-lactamases and an 'intrinsic mechanism' of resistance was inferred. The piperacillin/tazobactam combination restored resistance in 25 piperacillin strains. Nine of these were derepressed for chromosomal beta-lactamase, 8 showed impermeability and 8 showed plasmid enzymes.

Drug Therapy, Combination↗

PubMedDate not supplied

Comparative activity of piperacillin/tazobactam against clinical isolates of extended-spectrum beta-lactamase-producing Enterobacteriaceae.

beta-Lactam resistance on the part of the Enterobacteriaceae causes serious therapeutic problems in our institutions due to their production of extended-spectrum beta-lactamases (ESbetaLs). We studied the in vitro activity of beta-lactam/beta-lactamase inhibitor combinations and third-generation cephalosporins and monobactams against 71 clinically relevant Enterobacteriaceae which produced TEM- and SHV-derivative ESbetaLs. Of the single drugs and combinations tested, piperacillin/tazobactam proved to be the most effective. Piperacillin/tazobactam was highly active against Proteus mirabilis, with minimum inhibitory concentrations (MICs) ranging from 0.125 to 16 microg/ml; Escherichia coli (MICs from 2 to 16 microg/ml) and Serratia marcescens (MICs from 4 to 8 microg/ml), while its activity against Klebsiella pneumoniae ESbetaL producers turned out to be closely related to the type and the amount of enzyme produced, the MIC ranging from 1 to 128 microg/ml. The antibacterial activity of piperacillin/tazobactam was stronger than that of ticarcillin/clavulanate, ceftriaxone, cefotaxime, ceftazidime and aztreonam, and the combination shared favorable in vitro activity properties against the ESbetaL producers with imipenem which, however, should be kept as reserve product.

Clavulanic Acids↗

PubMedDate not supplied