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Biomedical subjects

G Satta

Publications and source records attributed to G Satta.

At least 91 records · Page 5Linked to original sources
PubMed1987

Streptococcus faecium mutants that are temperature sensitive for cell growth and show alterations in penicillin-binding proteins.

The penicillin-binding proteins (PBPs) of 209 cell division (or growth) temperature-sensitive mutants of Streptococcus faecium were analyzed in this study. A total of nine strains showed either constitutive or temperature-sensitive conditional damage in the PBPs. Analysis of these nine strains yielded the following results: one carried a PBP 1 constitutively showing a lower molecular weight; one constitutively lacked PBP 2; two lacked PBP 3 at 42 degrees C, but not at 30 degrees C; one was normal at 30 degrees C but at 42 degrees C lacked PBP 3 and overproduced PBP 5; two were normal at 42 degrees C and lacked PBP 5 at 30 degrees C; one constitutively lacked PBP 5; and one carried a PBP 6 constitutively split in two bands. The mutant lacking PBP 3 and overproducing PBP 5 continued to grow at 42 degrees C for 150 min and then lysed. Revertants selected for growth capability at 42 degrees C from the mutants altered in PBPs 5 and 6 maintained the same PBP alterations, while those isolated from the strains with altered PBP 1 or lacking PBP 2 or PBP 3 showed a normal PBP pattern. Penicillin-resistant derivatives were isolated at 30 degrees C from the mutants lacking PBP 2 and from that lacking PBP 3. All these derivatives continued to show the same PBP damage as the parents, but overproduced PBP 5 and grew at 42 degrees C. These findings indicate that high-molecular-weight, but not low-molecular-weight, PBPs are essential for cell growth in S. faecium. This is in complete agreement with previous findings obtained with a different experimental system. On the basis of both previous and present data it is suggested that PBPs 1, 2, and 3 appear necessary for cell growth at optimal temperature (and at maximal rate), but not for cell growth at a submaximal one (or at a reduced rate), and an overproduced PBP 5 is capable of taking over the function of PBPs 1, 2, and 3.

Bacterial Proteins↗
PubMed1987

Bacterial resistance and single-dose therapy of urinary tract infections.

In this work, we discuss the effects that the administration of both single and multiple doses of antibiotics are likely to have on antibiotic sensitivity of both the bacteria responsible for the infection and the human normal flora. It is concluded that a single-dose therapy when used under the appropriate conditions has the advantage of having less chances to select resistant strains in the normal bacterial flora.

Anti-Bacterial Agents↗
PubMed1986

In Streptococcus faecium penicillin-binding protein 5 alone is sufficient for growth at sub-maximal but not at maximal rate.

In Streptococcus faecium inhibition by both benzylpenicillin and cefotaxime of cells growing at maximal and at reduced rates was associated with saturation of different penicillin-binding proteins. Cells growing at reduced rates were not inhibited by benzylpenicillin concentrations that saturated all penicillin-binding proteins except penicillin-binding protein 5, but did stop growing when this protein was saturated.

Bacterial Proteins↗
PubMed1986

Comparison of effects of penicillin minimal inhibitory and sub-inhibitory concentration on Staphylococcus aureus and Streptococcus faecium does not support the view that antibiotic sub-inhibitory concentrations can specifically interfere with bacterial virulence.

The effect of minimal (MIC) and sub-minimal (sub-MIC) inhibitory concentrations of penicillin on Staphylococcus aureus and Streptococcus faecium were compared. It was found that similar alterations in both cell shape and ultrastructure were found in the presence of penicillin MIC and sub-MICs, the only difference being that while in the presence of penicillin MIC all individual cells were altered, in the presence of sub-MICs the damaged portion was smaller the lower the penicillin concentration and the longer the incubation time. By testing the effect of inoculum size on the penicillin MIC, it was found that penicillin concentrations, which were sub-MICs for rather dense population, turned out to be the MICs for lower density populations. These findings do not support the view that sub-MICs of antibiotics can cause specific damage to bacterial cells which, although not leading to growth inhibition, lowers their virulence. On the contrary, it is suggested that penicillin sub-MICs have no specific effect on Staphylococcus aureus and Streptococcus faecium cells, but simply differ from MIC in that they do not inhibit all cells.

Microbial Sensitivity Tests↗
PubMed1986

[Bacterial adhesins in the prophylaxis and therapy of infections].

Pathogenic bacteria must stably colonize mucosal surface to initiate the infectious process. A growing body of evidence indicates that bacteria attach to tissue surface by specific interactions between molecules of recognition (receptors) on host cell surface and adhesive molecules (adhesins) on the surfaces of the bacteria. One of the goals in the studies of bacterial adherence mechanisms is the eventual development of measures to prevent the adhesion of harmful bacteria to mucosal surfaces before the microorganism can produce tissue damage. In this paper we describe recent studies on the possibility to use in therapy either purified adhesins or receptors to block receptors and ligands respectively. We also describe recent studies on the development of antiadhesive vaccines, composed of purified ligands, to elicit local immune responses, resulting in the secretion of antibodies that cover the bacterial adhesins and thereby prevent attachment.

Anti-Bacterial Agents↗
PubMed1985

Incidence of Mediterranean spotted fever in Sardinia in the years 1982-1984.

In this work the incidence of Mediterranean spotted fever in the Borough of Cagliari (Sardinia) over the years 1982-1984 is evaluated. Our data show both an overall decrease of the incidence of the disease during this period of time with respect to the year 1980 and a significant reduction in the last year. In addition, the present study confirms the greater reliability of Immunofluorescence respect to the Weil-Felix reaction in revealing Mediterranean spotted fever. Finally we show a marked incidence of significant anti-Rickettsia conori antibodies in apparently healthy individuals, which stresses the not uncommon occurrence of subclinical infection.

Antibodies, Bacterial↗
PubMed1985

Effect of clonidine on stress-induced cortisol release in man during surgery.

The effect of clonidine on stress-induced cortisol secretion was studied in 10 patients undergoing general anesthesia for surgery; six other patients served as a control group and none of them was given clonidine. Central and peripheral alpha 2 stimulation by clonidine (average dose:0.45 mg over 60 minutes) was able to completely suppress cortisol release during surgery.

Adult↗
PubMed1985

Additional differentiating characters of the two subspecies of Staphylococcus hyicus.

Forty-five strains of Staphylococcus hyicus subsp. hyicus and 36 strains of S. hyicus subsp. chromogenes were examined for bacteriolytic activity with the same assay system previously used in taxonomic studies on staphylococci. The two subspecies differed from each other chiefly in that for optimal lytic activity S. hyicus subsp. hyicus strains required a higher salt concentration in the test medium than S. hyicus subsp. chromogenes strains. The lack of lytic activity on B15TP1 medium was a major difference between S. hyicus and S. aureus, and the lack of activity on TP2P medium was a major difference between S. hyicus and S. intermedius. Penicillin-binding proteins (PBPs) were studied in 40 S. hyicus strains. The S. hyicus subsp. hyicus strains had only one PBP (mol. wt 79 000) while the S. hyicus subsp. chromogenes strains had three distinct PBPs (mol. wts 84 000, 82 000 and 79 000).

Bacterial Proteins↗
PubMed1985

Transition from resistance to hypersusceptibility to beta-lactam antibiotics associated with loss of a low-affinity penicillin-binding protein in a Streptococcus faecium mutant highly resistant to penicillin.

Penicillin-binding protein (PBP) 5 of Streptococcus faecium has been shown to have a very low affinity for penicillin, and this PBP was suggested to be responsible for both the natural low susceptibility and high resistance to the antibiotic in this species (R. Fontana, R. Cerini, P. Longoni, A. Grossato, and P. Canepari, J. Bacteriol. 155:1343-1350, 1983). In this study, an S. faecium mutant (Rev 14) hypersusceptible to penicillin was derived from the highly resistant S. faecium R40 treated with novobiocin, and its properties were compared with those of the parent and S. faecium PS, a relatively susceptible strain from which R40 was isolated. The hypersusceptible strain did not synthesize PBP 5, but it did resemble the parent in cell morphology, growth rate, and autolytic activity. In addition, it was highly susceptible to other beta-lactams but remained as susceptible as R40 and PS to antibiotics of a different mechanisms of action. The affinity of individual PBPs for the beta-lactams tested was the same in all the strains. This finding suggested that Rev 14 hypersusceptibility was due to the lack of PBP 5 and strongly supported the role of this protein in the mechanism of both natural low susceptibility and high-level resistance to beta-lactams in S. faecium.

Anti-Bacterial Agents↗
PubMed1985

Different staphylococcal species contain various numbers of penicillin-binding proteins ranging from four (Staphylococcus aureus) to only one (Staphylococcus hyicus).

The penicillin-binding proteins of a total of 25 staphylococcal strains belonging to five different species were analyzed. All strains of the same species showed an identical penicillin-binding protein pattern which clearly differed from that of strains of the other species. Staphylococcus aureus, Staphylococcus intermedius, Staphylococcus simulans, and the dolphin strains were found to contain two to four penicillin-binding proteins. Strains of Staphylococcus hyicus exhibited only one penicillin-binding protein.

Bacterial Proteins↗
PubMed1985

Shifting of the penicillin binding proteins that are the target for inhibition by beta-lactams as a likely mechanism of resistance to antibiotics during therapy.

The penicillin binding proteins (PBPs) that in Streptococcus faecium are the targets for inhibitory activity of beta-lactam antibiotics were analyzed both in cells growing at their fastest and at reduced rates. It was found that while under the former conditions the PBPs showed the highest affinity for penicillin, under the latter the target is shifted to PBP (PBP5) that has a very low affinity for penicillin and other beta-lactams. The possibility that conditions met by Enterococci in human infections cause a shifting of the penicillin target and the possible role of such shifting in resistance to beta-lactams during therapy are discussed.

Anti-Bacterial Agents↗
PubMed1984

Inhibition of lateral wall elongation by mecillinam stimulates cell division in certain cell division conditional mutants of Escherichia coli.

The effect of mecillinam, a beta-lactam antibiotic that specifically binds penicillin-binding protein 2 of Escherichia coli, causes transition from rod to coccal shape, and inhibits cell division in sensitive cells, has been tested on three different E. coli temperature-sensitive cell division mutants. At the nonpermissive temperature, the antibiotic allows an increase in cell number for strains BUG6 and AX655 but not for AX621. In strain AX655, the cell division stimulation was observed only if the antibiotic was added immediately after shifting to the nonpermissive temperature, whereas in BUG6, the rise in cell number was observed also when mecillinam was added after 90 min of incubation at the nonpermissive temperature. In all cases, cell division began occurring 30 min after addition of the antibiotic. Mecillinam had no effect on division of dnaA, dnaB temperature-sensitive mutants or on division of BUG6 derivatives made resistant to this antibiotic. Other beta-lactam antibiotics such as penicillin, ampicillin, cephalexin, and piperacillin and non beta-lactam antibiotics such as fosfomycin, teichomycin, and vancomycin that inhibit cell wall synthesis did not show any effect on cell division for any of the mutants. The response of the three cell division mutants to mecillinam is interpreted in terms of a recently proposed model for shape regulation in bacteria.

Amdinocillin↗
PubMed1984

Division of temperature-sensitive Streptococcus faecium mutants after return to the permissive temperature.

The regrowth of 27 temperature-sensitive division mutants of Streptococcus faecium ATCC 9790 was examined after various periods of incubation at the nonpermissive temperature. Several of the mutants blocked at various stages of septum formation or of daughter-cell separation divided in a partially or completely synchronous way after a short incubation at the nonpermissive temperature. All four lytic mutants blocked early in the cell division cycle divided at a normal rate after a brief lag.

Cell Division↗
PubMed1984

The selective staining mechanism of phosphatase producing colonies in the diphosphatephenolphthalein-methyl green method for the detection of bacterial phosphatase activity.

The aim of this study was to explain, in a novel method for the testing of bacterial phosphatase activity (MGP), the mechanism by which, in the presence of a phosphatase substrate and a stain, the phosphatase positive colonies become intensely pigmented while the others remain unstained (Satta et al., 1979). The experiments here described indicate that the products of the phosphatase reaction form, with the stains, high pigmented insoluble complexes that precipitate at the site where the reaction has occurred. Since, in most bacteria, phosphatase are membrane bound, in the presence of phosphatase substrates and stains, intensely stained precipitates are formed on his bacterial component. Such precipitates make the cells become stained and cause the intense pigmentation of the phosphatase positive colonies.

Animals↗