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Biomedical subjects

B Oliva

Publications and source records attributed to B Oliva.

At least 55 records · Page 3Linked to original sources
PubMed1991

Lack of evidence for a saturable tetracycline transport system in Staphylococcus aureus.

Previous studies on tetracycline transport into Staphylococcus aureus identified a high-affinity, saturable uptake system for the antibiotic (Km, 4.76 microM) (B.L. Hutchings, Biochim. Biophys. Acta 174:734-738, 1969). However, the earlier results could not be confirmed using conditions that permitted energy-dependent, concentrative uptake of tetracycline. Kinetic artifacts introduced by inappropriate washing procedures may explain the previous results.

Biological Transport, Active↗
PubMed1991

Hybrid lymphoid blast crisis of chronic myeloid leukemia with both immunoglobulin and T-cell receptor gene rearrangements.

A case of Ph1+ chronic myeloid leukemia in blast crisis (CML-BC) is reported, in which the periodic acid Schiff and myeloperoxidase negative blasts displayed high terminal deoxynucleotidyl activity and coexpressed both B- (CD19, CD10, and CD24) and T- (CD7) lymphoid markers. In line with the immunophenotype, DNA analysis revealed a rearranged configuration of both the immunoglobulin and T-cell receptor (beta, gamma, and delta) genes. In spite of this dual B/T phenotype and genotype, the negativity of CyCD3 favors the suggestion that the target of the neoplastic event is an early B cell, with a cross lineage involvement of the putative common recombinase. However, taking into account that a normal counterpart of a biphenotypic B/T ALL has been recognized, it could be hypothesized that the leukemic transformation may have involved an oligopotent B/T lymphoid precursor. This case confirms the lineage heterogeneity of CML-BC and suggests that DNA analyses coupled to extensive immunophenotyping may allow further insight for a more precise recognition of both normal and leukemic ontogenesis.

Adult↗
PubMed1990

Broad spectrum beta-lactamases of Citrobacter diversus.

Citrobacter diversus NF85 produced a chromosomal beta-lactamase that was induced by a variety of beta-lactam antibiotics. Two major forms of the enzyme, with isoelectric points (pI's) of 5.7 and 6.2, were found in crude cell extracts. Derepressed mutants of NF85, generated by nitrosoguanidine treatment, displayed different levels of beta-lactamase expression to the parent strain and had different patterns of resistance to a range of beta-lactam antibiotics. Those mutants of NF85 that were totally derepressed, expressing high, constitutive levels of enzyme, were found to have an additional beta-lactamase activity with a pI of 6.8.

Anti-Bacterial Agents↗
PubMed1989

Immunologic and molecular evaluation of residual disease in B-cell chronic lymphocytic leukemia patients in clinical remission phase.

This study evaluates residual disease in 28 B-cell chronic lymphocytic leukemia (B-CLL) patients who obtained a clinicohematologic remission after intensive chemotherapy. Sixteen of 28 patients (57%) showed a normal number of circulating B-lymphocytes, as demonstrated by the low percentage of mouse rosette-forming cells (M-RFC), surface immunoglobulins (SIg), and CD24-positive cells. Clinically, a lower number of relapses occurred in this group of patients compared to those with a persistent expansion of peripheral B-cells (P less than 0.05). In order to assess monoclonality of the residual peripheral B-cell population, the distribution of SIg light chains was investigated on the B-cell-enriched fraction of 15 of these 16 cases. Only six of them had a kappa/lambda ratio which ranged between 1.7:1 and 3:1, whereas the remaining patients still displayed a clearly imbalanced kappa/lambda Ig light chain distribution. On the other hand, the analysis of the configuration of the Ig heavy chain gene region, performed in nine cases (including five of the above six cases), showed the persistence of a rearranged pattern in all cases tested but one. Therefore, residual monoclonal B-cells were found also in the majority of cases which displayed the lowest kappa/lambda ratio, a normal bone marrow lymphocytosis and a long-lasting clinical remission. Studies at the DNA level confirm that a remission is rarely achieved in this disease in spite of intensive and prolonged chemotherapy. Nonetheless, the follow-up of B-CLL patients by conventional immunologic markers may be helpful to better define response to therapy and to predict the occurrence of clinical relapse.

B-Lymphocytes↗
PubMed1989

Penicillin-binding protein 2 is required for induction of the Citrobacter freundii class I chromosomal beta-lactamase in Escherichia coli.

Involvement of Escherichia coli penicillin-binding proteins (PBPs) in induction of the cloned ampC Citrobacter freundii beta-lactamase by 6-aminopenicillanic acid was investigated. The enzyme was not inducible at 42 degrees C in a mutant thermosensitive for expression of PBP 2. The results imply that PBP 2 is involved in the process leading to induction of ampC.

Acyltransferases↗
PubMed1988

Plasmid "curing" by some recently synthetized 4-quinolone compounds.

Nalidixic acid and two recently synthetized 4-quinolones eliminated F'lac and R-plasmids from E. coli at concentrations of one half or one quarter of the minimum inhibitory concentration (MIC). Two of the three plasmids tested were cured by all derivatives, although with different frequencies. Pefloxacin was the most effective compound compared with the other quinolones and nalidixic acid the least active.

Escherichia coli↗
PubMed1988

Inhibition of plasmid conjugation by some recently synthetized 4-quinolone compounds.

Four fluoroquinolones (norfloxacin, ciprofloxacin, ofloxacin, and pefloxacin) were compared with nalidixic acid for their inhibitory effect on conjugal plasmid transfer. The inhibition was observed in mating experiments using various combinations of drugs at subinhibitory concentrations and 3 different plasmids in the E. coli k12 genetic background. Fluoroquinolones inhibited plasmid transfer to a greater extent than nalidixic acid. Ofloxacin and pefloxacin were consistently the most active agents, causing 90 to 100% inhibition of plasmid transfer in all mating systems studied.

Anti-Infective Agents↗
PubMed1988

On the kinetic interaction between ceftriaxone and some beta-lactamases.

The activity of beta-lactamases from Citrobacter diversus ULA-27 on ceftriaxone, a widely recognized third-generation cephalosporin, has been examined and compared to the activity of various other beta-lactamases from different sources. Ceftriaxone (Roche S.p.A. Milan) was found to be resistant to hydrolysis by beta-lactamases from Enterobacter cloacae and Bacillus cereus, but susceptible to beta-lactamases from Mycobacterium fortuitum strain Cow 18 and, mostly, to beta-lactamases from various strains of Citrobacter diversus. Derivatives with substituents in the 3-position of ceftriaxone, namely cefotaxime (Roussel Maestretti S.p.A., Milan) and ceftizoxime (Farmitalia Carlo Erba, Milan), were much less susceptible to hydrolysis by C. diversus ULA-27 enzymes (22 and 6% of ceftriaxone hydrolysis, respectively), the hydrolysis rate being paralleled by differences in MIC values. Ceftriaxone inhibited the activity of E. cloacae beta-lactamases toward cefazolin as substrate, but the inhibition was totally abolished by preincubation of ceftriaxone with the enzyme before addition of the substrate. Overall, the data point to a relevance of C. diversus ULA-27 beta-lactamases in the mechanism of resistance of this strain to the various third-generation cephalosporins.

Bacillus↗
PubMed1987

Simplified identification of bacteria belonging to the genus Salmonella.

A new, simplified procedure for identification of bacteria belonging to the genus Salmonella is reported. By this procedure which is a new combination of well know tests, Salmonella spp. are easily and reproducibly differentiated from non Salmonella spp. after 6 h of incubation at 37 degrees C.

Bacteriological Techniques↗
PubMed1987

Citrobacter diversus ULA27 produces two forms of a chromosomal beta-lactamase.

A multi-resistant clinical isolate of Citrobacter diversus, particularly resistant to penicillins and cephalosporins, has been studied. The strain produced constitutively high levels of beta-lactamase which efficiently hydrolysed cephaloridine but not ampicillin. The apparent Km value for cephaloridine (125 +/- 25 microM) was within the range usually observed for beta-lactamases in similar bacteria. The strain possessed two forms of the enzyme as indicated by isoelectric focusing patterns, HPLC analysis and two pH optima. SDS-PAGE analysis indicated a single protein responsible for both forms. The strain possessed a single plasmid, as revealed by agarose gel electrophoresis, but beta-lactamase production was not plasmid encoded. The available data indicate the beta-lactamase(s) of C. diversus ULA27 to be chromosomally encoded.

Anti-Bacterial Agents↗
PubMed1986

Expression and some properties of beta-lactamase from Mycobacterium fortuitum.

Several species of mycobacteria have been reported to produce beta-lactamases, but only those of M. smegmatis have been purified and partially characterized. This study is a preliminary report of the presence of beta-lactamase activity in M. fortuitum, strain Cow 18. A partial purification of the beta-lactamase has also been achieved. M. fortuitum was grown in either Sauton or glucose-yeast extract medium (GYM) and sonicated cells or culture filtrates were assessed for the presence of beta-lactamase activity using a chromogenic compound (PADAC) as substrate. Cells growing in GYM medium released a detectable amount of enzyme, whereas microorganisms showed only intracellular beta-lactamase activity. The enzyme present in the culture filtrate of M. fortuitum Cow 18 was concentrated by Amicon ultrafiltration and partially purified through Sephadex G-75 and QAE-Sephadex A-50 ion exchanger columns. The spectrum of activity of this enzyme included some cephalosporins (cephaloridine, cephalothin) and some penicillins, the hydrolysis of the former being generally more pronounced. Furthermore, cefoxitin, ceftazidime and cefotaxime were not hydrolysed.

Culture Media↗
PubMed1985

Inhibition of conjugal transfer by new quinolinic compounds.

We found that nalidixic acid is a good inhibitor of conjugal transfer of R-plasmids and that related compounds show the same properties. We investigated recently synthetized quinolinic molecules. The inhibition was not due to bacterial activity of the compounds against donors, recipients or R transconjugants; in fact, the drug concentrations were twice or four times lower than the M.I.C. values. The new molecules showed a marked inhibitory effect in various R-mating experiments.

4-Quinolones↗
PubMed1980

New translocation sequence mediating tetracycline resistance found in Escherichia coli pathogenic for piglets.

A discrete piece of deoxyribonucleic acid coding for tetracycline (Tc) resistance was found to move from one R plasmid to another in an Escherichia coli strain which is pathogenic for piglets. Since this phenomenon took place also in rec strains, the Tc segment was classified as a transposon and called Tn804. Restriction enzyme analysis with EcoRI, BglII, and HindIII indicated that Tn804 is related to Tn10, a well-known transposon that codes for resistance to tetracycline. Hybridization between plasmids carrying the two transposons provided proof of homology between Tn10 and prt of Tn804. Electron microscopic studies showed a transposon-like structure composed of one loop-stem structure with inverted repetitions of approximately 0.9 megadaltons inserted into the loop of a second loop-stem structure. It is suggested that Tn804 is composed of Tn10 plus another transposable sequence.

Animals↗
PubMed1979

Plasmids and transposable elements in Salmonella wien.

The plasmids from six clinical strains of Salmonella wien have been characterized. All the S. wien strains were found to carry three types of plasmids: an IncFI R-Tc Cm Km Ap (resistance to tetracycline, chloramphenicol, kanamycin, and ampicillin) plasmid, either conjugative or nonconjugative, of large size (90 to 100 megadaltons); an R-Ap Su Sm (resistance to ampicillin, sulfonamide, and streptomycin) plasmid of 9 megadaltons; and a very small (1.4 megadaltons) cryptic plasmid. The characteristics of conjugative R plasmids, recombinant between F'lac pro and the FI nonconjugative plasmid, indicated that regions coding for the donor phenotype were present on this plasmid. The molecular and genetic features of the R plasmids were very close to those described for the R plasmids isolated from S. wien strains of different origin. This fact supported the hypothesis of a clonal distribution of this serotype in Algeria and Europe. The analysis used to identify transposable elements showed the presence of only TnA elements, which were located on both the R-Tc Cm Km Ap and R-Ap Su Sm plasmids. They contained the structural gene for a TEM-type beta-lactamase and had translocation properties analogous to those reported for other TnA's.

Ampicillin↗
PubMed1975

In vitro and in vivo microbiological evaluation of Cephapirin, a new antibiotic.

The microbiological properties of cephapirin, a new semisynthetis cephalosporin, have been studied. This antibiotic, if compared with ampicillin, shows a greater activity against gram positive bacteria, a lack of sensitivity to staphlococcal beta-lactamase, and a lower sensitivity to those produced by gram-negative bacteria. Useful therapeutic of cephapirin levels can be detected in human serum 6 h after administration of 500 and 1,000 mg parenterally.

Ampicillin↗