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P Canepari

Publications and source records attributed to P Canepari.

At least 55 records · Page 3Linked 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

Preliminary research on possibility of bronchial asthma treatment with hyperbaric oxygenation.

The total of the persons examined was divided into 3 groups. There were 11 men and 5 women with various diseases diagnosed in Group I, 5 healthy men in Group II and 9 man and 2 women with allergy in Group III, the control group. The subjects were treated with hyperbaric oxygenation exposures from 1.8 to 2.5 ata O2 within a 60-90 minute period. The number of exposures ranged from 1-4 for Group II till 10-15 for Group I and Group III. In all the cases the following examinations were carried out: hematological tests (Hb, Ht, erythrocytes, leucocytes, and blood platelets counts, blood picture), immunological tests (IgG, IgM, IgA, IgD, IgE, C3 fraction of complement and hematolytical activity of complement--CH50) and all required additional clinical tests. These examinations were made before the series of hyperbaric exposures, after 4 exposures, after their completion and a month later. Full documentation in Group I was obtained in 6 cases and in the 10 remaining only before the exposures and after their completion. In Group II full documentation was available only in 1 person, but before the exposures and after their completion in the rest, and finally, in Group III full documentation was obtained in 7 persons, but before the exposures and after their completion in 4 others. Generally, it was in allergic states that a positive therapeutic effect of hyperbaric oxygenation was found. It had already been corroborated by the respective shifts of immunological coefficients, noted by other authors too. The above observations need to be confirmed in a wider material, in different periods of the disease and with other additional examinations employed.

Adult↗
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↗
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

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↗
PubMed1983

Streptococcus faecium ATCC 9790 penicillin-binding proteins and penicillin sensitivity are heavily influenced by growth conditions: proposal for an indirect mechanism of growth inhibition by beta-lactams.

The effects of variations in growth conditions on the penicillin response of Streptococcus faecium ATCC 9790 were studied. Changes in the growth temperature and medium composition were found to cause striking changes in the bacterial generation time, cellular penicillin sensitivity (minimum inhibitory concentration), sensitivity of peptidoglycan synthesis to inhibition by penicillin, rate of autolysis, and labeling pattern of penicillin-binding proteins. However, no constant relationship between these parameters and the minimum inhibitory concentration could be observed. Similar electrophoretic patterns for penicillin-binding proteins were observed in cells grown in different media at the optimal growth temperature. Inhibition of cell division by penicillin in cells grown at this temperature (but not at higher or lower temperatures) caused filamentation of the bacteria. In cells grown in a chemically defined medium at the optimal temperature (but not at temperatures above or below), complete inhibition of cell division was associated with only partial inhibition (34% after 150 min) of peptidoglycan synthesis. It is suggested that the status and physiological importance of individual penicillin-binding proteins in S. faecium are heavily influenced by growth conditions. Depending on the growth conditions, different penicillin-binding proteins may perform the cellular function, indispensible for bacterial growth.

Bacterial Proteins↗
PubMed1983

Identification of a streptococcal penicillin-binding protein that reacts very slowly with penicillin.

Penicillin-binding protein (PBP) 5 of Streptococcus faecium ATCC 9790 has an unusually low affinity for penicillin (50% binding occurred at a penicillin level of 8 micrograms/ml after 60 min of incubation, and the protein only became labeled after 20 min of incubation with high concentrations of radioactive penicillin). PBPs with similar properties are carried by strains of Streptococcus durans, Streptococcus faecalis, and Streptococcus lactis but not by strains of groups A, B, C, and G streptococci or Streptococcus pneumoniae. The strains carrying the slow-reacting PBP demonstrated a sensitivity to penicillin that was several hundred times lower than that of strains not carrying it. Spontaneous mutants with minimal inhibitory concentrations of penicillin of 20, 40, and 80 micrograms/ml were isolated from S. faecium ATCC 9790. They all showed a dramatic increase in the amount of slow-reacting PBP produced. Mutants with increased penicillin resistance were also isolated from wild-type strains of S. durans, S. faecalis, and S. faecium. All of them carried a greater amount of the slow-reacting PBP than that carried by the parent. Finally, it was found that resistant S. faecium ATCC 9790 mutants grew normally in the presence of penicillin concentrations that were far above that saturating all PBPs except PBP 5. Cell growth was, on the contrary, inhibited by a penicillin concentration that saturated the slow-reacting PBP by 90%. This penicillin dose was equal to the minimal inhibitory concentration.

Bacterial Proteins↗
PubMed1983

Division blocks in temperature-sensitive mutants of Streptococcus faecium (S. faecalis ATCC 9790).

Two hundred nine temperature-sensitive growth or division (or both) mutants of Streptococcus faecium ATCC 9790 were isolated. These strains were examined for timing of the division block in the cell division cycle. About 42% of the isolates were blocked at terminal stages of cell division. A second large group appeared to be blocked at various stages of septation. Only five of the temperature-sensitive isolates were blocked at a stage before the completion of chromosome replication. Thirty temperature-sensitive isolates lysed after one or more doublings at the nonpermissive temperature.

Cell Division↗
PubMed1981

Early initiation of deoxyribonucleic acid replication and shortening of generation time associated with inhibition of lateral wall formation by mecillinam.

The effects of mecillinam on the growth of rods of the pH-conditional morphology mutant MirM7 was studied. It has been found that mecillinam causes, coincident with transition to coccal shape, a balanced rise in the rate of viable count increase and the rate of macromolecular synthesis which lasts either until the cells enter a stationary growth phase or indefinitely, in the case of continuously diluted cultures. When the antibiotic is removed from cells which have already become coccoid, cells continue to grow at a faster rate until they resume the rod shape. No change in the per-cell rate of protein synthesis has been seen in untreated or mecillinam-treated cells before or after the change in growth rate. Studies with synchronously growing cells have shown that the antibiotic causes a shortening in the I period (initiation of deoxyribonucleic acid replication). Evaluation of the residual divisions in nalidixic acid-treated, exponential-phase cells has shown that mecillinam also shortens the D period (cell division). It is proposed that, in strain MirM7, inhibition of lateral wall elongation by the antibiotic allows the initiation of a new septum, though inhibition is still in progress. The initiation of a new septum is, in turn, responsible for both the early inibition of deoxyribonucleic acid replication and accelerated division. In the parental strain, MirA12, as well as in other sensitive gram-negative rods which divide, become cocci, and stop dividing after addition of the antibiotic, inhibition of lateral wall formation activates a feedback mechanism which prevents insertion of new septa (Satta et al., J. Bacteriol. 142:43-51, 1980). Consequently, no early initiation of deoxyribonucleic acid replication is observed, and the last division allowed by the antibiotic occurs in due time. This negative control is missing in MirM7.

Amdinocillin↗
PubMed1980

Identification of the lethal target of benzylpenicillin in Streptococcus faecalis by in vivo penicillin binding studies.

The mode of bacterial killing by penicillins is still unknown in spite of many studies on the subject. The recent finding of multiple penicillin binding proteins (PBPs) in sensitive bacteria and the possibility of analysing the binding of the antibiotic to exponentially growing cells have provided new directions for investigating this problem. Sensitivity to lethal and other effects of penicillin varies very significantly with the conditions of growth of the cells. If PBPs were the penicillin target, changes in conditions of growth causing variations in penicillin sensitivity should be accompanied by changes in these proteins. Furthermore, if one of PBPs could be identified as the killing target, it could possibly be demonstrated to show changes in cells growing in different conditions. We show here that in Streptococcus faecalis ATCC 9790 changes in conditions of growth are accompanied by changes in PBPs. Furthermore, in the presence of the minimal dose of 14C-benzylpenicillin causing complete inhibition of cell growth, 100% of the total radioactivity is bound to a single protein (PBP 3).

Bacterial Proteins↗
PubMed1980

Control of cell septation by lateral wall extension in a pH-conditional morphology mutant of Klebsiella pneumoniae.

The pH-conditional morphology mutant of Klebsiella pneumoniae strain MirM7 grows as cocci at pH 7 and as rods at pH 5.8. The mutant has a high-level mecillinam resistance (50% lethal dose greater than 200 micrograms/ml) in both forms. When broth cultures of the rod-shaped mutant were grown with 0.7 microgram of mecillinam per ml, cells assumed a round shape and continued to divided at a higher rate than the untreated control. A MirM7 rod-shaped revertant (MirA12), when treated with the same antibiotic concentration, changed to coccal shape and stopped dividing. The penicillin-binding proteins (PBPs) of strains MirA12 and MirM7 were analyzed. K. pneumoniae had six major PBPs quite similar to those of Escherichia coli. No differences were seen in the PBPs of MirM7 cocci and rods and MirA12 cells. In particular, PBP2 was found to be present and similar in MirM7 rods and cocci and MirA12 cells. We suggest that that in gram-negative rods, a control mechanism exists which prevents further septation in the absence of lateral cell wall elongation. The unique behavior of MirM7 is due to the fact that the control mechanism is not active in this strain. This model allows us to explain the preservation of shape in bacterial rods under various conditions of growth and the mechanism of bacterial killing by mecillinam.

Amdinocillin↗
PubMed1979

Peptidoglycan synthesis in cocci and rods of a pH-dependent, morphologically conditional mutant of Klebsiella pneumoniae.

Mir M7 is a spontaneous morphologically conditional mutant of Klebsiella pneumoniae which grows as round cells (cocci) at pH 7 and as normal rods at pH 5.8. We studied the rates of peptidoglycan synthesis of cocci and rods growing at pH values of 7 and 5.8, respectively. It was found that exponentially growing cocci produced a reduced amount of peptidoglycan per cell, compared with rods. Moreover, a shift of cocci to the permissive pH (5.8) caused an increase in the rate of peptidoglycan synthesis, whereas the reverse shift of rods to pH 7 determined a twofold reduction in the rate of [(3)H]diaminopimelic acid incorporation. During synchronous growth at pH 7, the rate of peptidoglycan synthesis after cell division decreased with time and rose before and during the first division. The susceptibilities of rods and cocci to beta-lactam antibiotics were also studied. It was found that cocci were more sensitive both to penicillin G and to cephalexin than were rods, but they showed a high level of resistance to mecillinam. The peculiar behavior of this mutant was interpreted as supporting the existence in bacterial rods of two different sites for peptidoglycan synthesis: one responsible for lateral wall elongation and one responsible for septum formation. In Mir M7, shape damage is described as dependent on the specific inhibition, at the nonpermissive pH, of the site for lateral wall extension.

Amdinocillin↗
PubMed1979

Alterations in peptidoglycan chemical composition associated with rod-to-sphere transition in a conditional mutant of Klebsiella pneumoniae.

Klebsiella pneumoniae Mir M7 is a spontaneous parentless morphology mutant which grows as cocci at pH 7 and as rods at pH 5.8. This strain has been characterized as defective in lateral wall formation (at pH7). Data suggest that the cell wall is mainly made up of poles of the rods (G. Satta, R. Fontana, P. Canepari, and G. Botta, J. Bacteriol. 137:727--734, 1979). In this work the isolation and the biochemical properties of the peptidoglycan of both Mir M7 rods and cocci and a nonconditional rod-shaped Mir M7 revertant (strain Mir A12) are described. The peptidoglycan of Mir M7 (both rods and cocci) and Mir A12 strains carried covalently bound proteins which could be easily removed by pronase treatment in Mir M7 rods and Mir A12 cells, but not in Mir M7 round cells. However, when the sodium dodecyl sulfate-insoluble residues of Mir M7 cocci were pretreated with ethylenediaminetetraacetic acid (EDTA), pronase digestion removed the covalently bound proteins, and pure peptidoglycan was obtained. EDTA treatment of the rigid layer of Mir M7 cocci removed amounts of Mg2+ and Ca2+, which were 10- and 50-fold higher, respectively, than the amount liberated from the rigid layer of Mir M7 rods and Mir A12 cells. Amino acid composition was qualitatively similar in both strains, but Mir M7 cocci contained a higher amount of alanine and glucosamine. Mir M7 cocci contained approximately 50% less peptidoglycan than rods. Under electron microscopy, the rigid layer of the Mir M7 rods and Mir A12 cells appeared to be rod-shaped and their shape remained unchanged after EDTA and pronase treatment. On the contrary, the Mir M7 cocci rigid layer appeared to be round, and after EDTA treatment it collapsed and lost any definite morphology. In spite of these alterations, the peptidoglycan of Mir M7 cocci still appeared able to determine the shape of the cell and protect it from osmotic shock and mechanical damages. The accumluation of divalent cations appeared necessary for the peptidoglycan to acquire sufficient rigidity for shape determination and cell protection. We concluded that the coccal shape in Mir M7 cells is not due to loss of cell wall rigidity but is a consequence of the formation of a round peptidoglycan molecule. The possibility that the alterations found in the Mir M7 cocci rigid layer may reflect natural differences in the biochemical composition of the septa and lateral wall of normally shaped bacteria is discussed.

Amino Acids↗