Biomedical subjects

A Hostacká

Publications and source records attributed to A Hostacká.

At least 37 records · Page 2Linked to original sources

PubMed2000

Effect of meropenem on the vascular permeability factor produced by Acinetobacter baumannii.

Eleven Acinetobacter baumannii strains produced a toxic substance--the vascular permeability factor--in the culture medium. Intradermal injection of this substance enhanced vascular permeability in the rabbit skin. The extent of permeability reactions varied from 0.28 cm2 to 1.61 cm2. Changes in the permeability factor activity of four A. baumannii strains after treatment with meropenem (CAS 96036-03-2) at suprainhibitory concentrations (2x, 4x or 8x) minimum inhibitory concentration (MIC) or supra-subinhibitory ones (2-8x MIC + 0.2x MIC) were tested in vitro. Meropenem at all suprainhibitory concentrations (with the exception of 8x MIC for one strain) was almost ineffective. Alterations in this activity were in the range of 93% to 106% of the control values. Supra-subinhibitory concentrations of meropenem significantly increased the permeability factor activity (to 150%-176% of the control values). These findings indicate that meropenem mainly at supra-subinhibitory concentrations can in vitro interfere with the vascular permeability factor produced by A. baumannii.

Acinetobacter↗

PubMed2000

[Pharmacodynamic parameters of gentamicin and its effect on the surface hydrophobicity of Acinetobacter baumannii].

The postantibiotic effect (PAE) and postantibiotic effect of subinhibitory concentration (PA SME) of gentamicin as well as influence of these pharmacodynamic parameters on surface hydrophobicity of three Acinetobacter baumannii strains were studied in vitro. Suppression of bacterial growth (PAE) after a short time exposure of bacteria to gentamicin (30 min) at suprainhibitory concentration 2x MIC was in the range of 0.6 h to 3.4 h. Longer PAE was observed after treatment of bacteria with gentamicin at 4x MIC (1.5 h-5.1 h). Supra-subinhibitory concentrations of gentamicin (2x or 4x MIC + 0.2x MIC) caused still more effective delay of bacterial regrowth (PA SME) in comparison with suprainhibitory concentrations for one strain (9.1 h and 9.6 h) and in the case of further two strains they were so efficient that regrowth of bacteria was not observed for 24 h. Surface hydrophobicity of the gentamicin treated strains evaluated by adherence of bacteria to xylene ranged from 90.0% to 99.7% of the control values (without antibiotic).

Acinetobacter↗

PubMed2000

Influence of some antibiotics on lipase and hydrophobicity of Acinetobacter baumannii.

Effect of four antibiotics (cefotaxime, ceftazidime, cefepime and ofloxacin) at subinhibitory concentrations (sub-MICs) (1/4, 1/8 or 1/16 of the MICs) on lipase and cell surface hydrophobicity of a clinical isolate of Acinetobacter baumannii 16265 was studied. Lipase activity in the majority of the cases was not significantly changed. Small alterations were drug and concentration dependent. The most efficient ceftazidime at 1/4 of the MIC reduced lipolytic activity to 78.7% of the control value. On the other hand, all beta-lactam antibiotics mainly at the highest concentration (1/4 of the MICs) most effectively decreased surface hydrophobicity of the studied strain. Hydrophobicity of treated bacteria evaluated by their adherence to xylene was in the range of 11.2 to 29.9% of the control values. The most efficient was cefepime. Whether the modifications in potential virulence factors of the bacteria tested observed in in-vitro experiments would have the clinical importance, remains to be evaluated.

Acinetobacter↗

PubMed2000

[New findings on the genus Acinetobacter].

The author reviewed recent data on the genus Acinetobacter. It is an evaluation of their participation in nosocomial infections, antibiotic resistance, virulence factors as well as the possibilities of modifications of their virulence after treatment with antibiotics.

Acinetobacter↗

PubMed1999

Alterations in surface hydrophobicity of Acinetobacter baumannii induced by meropenem.

Six strains of Acinetobacter baumannii out of eleven strains tested revealed a strong hydrophobic character. This was demonstrated by adherence of bacteria to xylene in the range of 90-94%. Changes in surface hydrophobicity of these strains were studied after treatment with meropenem at subinhibitory concentrations (sub-MICs) (1/4, 1/8, 1/16 or 1/32 of the MICs). All strains showed a reduced adherence to xylene after the action of meropenem at 1/4 or 1/16 of the MICs. Hydrophobicity of the treated bacteria was decreased to 1.3-70% (1/16 of the MICs) or to 12-86% (1/4 of the MICs), depending on the strain. A decrease in surface hydrophobicity of three strains was also observed after their exposure to meropenem at 1/8 of the MICs (to 18-71% of the control values). Meropenem at 1/32 of the MICs practically did not affect bacterial hydrophobic properties, with the exception of one strain.

Acinetobacter↗

PubMed1999

Cytotoxic activity of Acinetobacter baumannii after treatment with aminoglycosides.

The effect of three aminoglycoside antibiotics--netilmicin (CAS 56391-57-2), gentamicin (CAS 1403-66-3) and amikacin (CAS 37517-28-5)--at subinhibitory concentrations (sub-MICs; 1/4 or 1/16 of the MICs) on the cytotoxic activity of Acinetobacter baumannii was studied. The cytotoxic factor was manifested by reduction of the number of isolated rat lung type II cells evaluated by alkaline phosphatase determination. All aminoglycosides at both concentrations studied (with the exception of 1/4 of the MIC of amikacin) did not modify cytotoxic activity of A. baumannii. This activity was partially inhibited only after treatment with amikacin at 1/4 of the MIC. In this case the number of type II cells after incubation with antibiotic treated A. baumannii was higher (71%) as compared to the number of type II cells cultured with untreated A. baumannii (47%).

Acinetobacter↗

PubMed1999

Effect of amikacin on cytotoxic activity and hydrophobicity of Acinetobacter baumannii.

Effect of amikacin at suprainhibitory (2 or 4 x MIC) or supra-subinhibitory concentrations (2 or 4 x MIC + 0.2 x MIC) on bacterial growth, cytotoxicity and cell surface hydrophobicity of three Acinetobacter baumannii strains was studied. Amikacin at suprainhibitory concentrations induced postantibiotic effects (PAEs; suppression of bacterial growth after short time exposure of bacteria to the antibiotic) against all A. baumannii strains. PAEs ranged from 1.2 to 2.9 h (2 x MIC) and 3.5 to 6.3 h (4 x MIC). Supra-subinhibitory concentrations of amikacin (2 x MIC + 0.2 x MIC) manifested a more significant delay of bacterial regrowth (PA SMEs) for two strains (6.6 or 7.5 h) in comparison with PAEs. One strain under these conditions as well as all strains treated with amikacin at 4 x MIC + 0.2 x MIC did not show any regrowth. Amikacin at all concentrations tested significantly reduced cytotoxic activity of A. baumannii evaluated on alveolar epithelial type II cells. Survival of type II cells after application of antibiotic-treated A. baumannii was in the range of 88 to 101% of the control cells. Cell surface hydrophobicity of amikacin-treated bacteria was practically unchanged varying between 94 and 100.9% as compared to the controls.

Acinetobacter↗

PubMed1999

[Sensitivity to blood bactericidal activity and hydrophobicity of Acinetobacter baumannii after treatment with imipenem].

Sensitivity to the serum bactericidal activity and surface hydrophobicity of Acinetobacter baumannii strains isolated from the urinary (UT) or respiratory tract (RT) of patients after exposure to imipenem at subinhibitory concentrations (sub-MICs) (1/4, 1/8 or 1/16 of their MICs) were tested. The antibiotic at the mentioned concentrations decreased significantly the sensitivity of strain UT to the bactericidal activity of human serum. Sensitivity to the bactericidal activity of serum of strain RT was affected only very ineffectively. Imipenem at 1/4 of their MICs reduced the cell surface hydrophobicity to 76.1% (strain UT) and to 81.9% (strain RT) compared with control values (without imipenem). Lower concentrations of antibiotic influenced cell surface hydrophobicity only to a smaller extent. Possible decrease in sensitivity of bacteria to the bactericidal activity of serum after treatment with imipenem in "in vivo" experiments would manifest an increase in virulence of these strains.

Acinetobacter↗

PubMed1999

Pharmacodynamic parameters and hydrophobicity changes induced by meropenem in Acinetobacter baumannii.

The suppression of bacterial growth of four Acinetobacter baumannii strains after 60 min exposure to meropenem at supra-inhibitory concentrations (postantibiotic effect; PAE) or at supra-subinhibitory concentrations (postantibiotic-sub-MIC effect; PA SME) was studied. The duration of the PAE was dependent on antibiotic concentration and on the strain. Meropenem at 2x or 4x the minimum inhibitory concentration (MIC), with the exception of one strain treated with 4x MIC, did not provoke suppression of bacterial growth compared with untreated controls. The highest concentration of meropenem (8x MIC) induced PAE for the strains tested in the range of 0.6-6.9 h. The effect of supra-subinhibitory concentrations of meropenem (2x, 4x or 8x MIC + 0.2x MIC) on bacterial growth was more efficient compared with supra-inhibitory concentrations alone. Two out of the four strains treated did not renew their growth. Bacterial suspensions exposed to meropenem showed reduced surface hydrophobicity. Decreases in hydrophobicity were associated with longer PAE and PA SME depending on the strain.

Acinetobacter↗

PubMed1999

[In vitro effect of quinolones on the hydrophobicity of Acinetobacter baumannii].

Effects of subinhibitory concentrations (sub-MICs) (1/4, 1/8, 1/16 or 1/32 of the MICs) of four quinolone antibiotics on surface hydrophobicity of two Acinetobacter baumannii strains (R1 and R2) were tested. Hydrophobicity was evaluated by adherence of bacteria to xylene and their aggregation in ammonium sulphate solutions. Norfloxacin in concentrations of 1/4 or 1/8 of the MIC decreased hydrophobicity of R1 strain and of R2 strain in concentration of 1/16 of the MIC. Ciprofloxacin was efficient for both strains mainly in concentration of 1/4 of their MICs. Enoxacin (1/8 MIC) more effectively reduced hydrophobic properties only in R2 strain. The other concentrations of the above-mentioned antibiotics as well as all tested concentrations of pefloxacin practically did not affect bacterial surface hydrophobicity.

Acinetobacter↗

PubMed1999

[Effect of ofloxacin, pefloxacin, and tobramycin on the hydrophobicity of Klebsiella pneumoniae].

The effect of ofloxacin, pefloxacin and tobramycin at subinhibitory concentrations (1/4, 1/8 and 1/16 of the MICs) on surface hydrophobicity of the Klebsiella pneumoniae strain was studied. The antibiotics tested decreased cell surface hydrophobicity in a dose-dependent manner. The most significant reduction of surface hydrophobicity was found after treatment with antibiotics at 1/4 of their MICs. Surface hydrophobicity of K. pneumoniae after exposure to these concentrations was decreased to 44% (ofloxacin), 50.7% (pefloxacin) and 56.1% (tobramycin) compared with controls.

Anti-Bacterial Agents↗

PubMed1999

In vitro effect of imipenem on Acinetobacter baumannii.

Imipenem at suprainhibitory concentrations (2x, 4x or 8x MIC) induced postantibiotic effects (PAEs) (suppression of bacterial growth after a short time exposure of bacteria to antimicrobials) against two of three Acinetobacter baumannii strains. The highest concentration tested demonstrated the longest delay of bacterial regrowth (1.7 h (strain 5570) or 3.9 h (strain 6070)). All. A. baumannii strains showed changes in surface hydrophobicity and serum sensitivity after treatment with imipenem. The antibiotic at 8x MIC reduced hydrophobicity of the strains most significantly (from 42.3%-72.0%) as compared to controls (without antibiotic). Susceptibility of the treated bacteria to serum bactericidal activity has also been lowered. Though imipenem suppressed bacterial growth and decreased surface hydrophobicity of the bacteria, it increased survival of bacteria after incubation with serum. These different alterations observed in the studied strains should be taken into account when evaluating the effects of imipenem.

Acinetobacter↗

PubMed1998

Outer membrane proteins of Klebsiella pneumoniae after exposure to ciprofloxacin.

Suppression of bacterial growth of two Klebsiella pneumoniae strains after a short time exposure to ciprofloxacin at suprainhibitory concentrations was found (postantibiotic effect-PAE). PAEs induced by ciprofloxacin at 2 x MIC were 4.1 h and 5.3 h for the strains tested, the concentration of 4 x MIC manifested a suppression of the bacterial growth which lasted 5.9 h and 6.3 h. Delay of regrowth of K. pneumoniae strains exposed to suprainhibitory concentrations of quinolones was shown also by other authors. New information concerning the outer membrane protein profile of K. pneumoniae after PAE has been found. SDS-PAGE analysis revealed that outer membrane protein patterns isolated from K. pneumoniae strains treated with a suprainhibitory concentration of ciprofloxacin did not show apparent changes as compared to controls.

Anti-Infective Agents↗

PubMed1998

Effect of subinhibitory concentrations of some quinolones on a strain of Shigella dysenteriae type 1.

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the outer membrane proteins of a strain of Shigella dysenteriae exposed to four quinolone compounds (ciprofloxacin--CAS 85721-33-1, ofloxacin--CAS 83380-47-6, pefloxacin--CAS 70458-95-6, and enoxacin--CAS 74011-58-8) at subinhibitory concentrations of 1/4 or 1/8 of the minimal inhibitory concentration (MIC) showed no alterations as compared to the control. Also the hydrophobicity of the cell surface of the test strain was not affected after exposure to subinhibitory concentrations of the quinolones.

4-Quinolones↗

PubMed1998

Effects of imipenem and meropenem on serum sensitivity and surface hydrophobicity of Klebsiella pneumoniae.

Serum sensitivity and surface hydrophobicity of two Klebsiella pneumoniae strains (internal strain No. 378 and 3259) exposed to imipenem (CAS 64221-86-9) and meropenem (CAS 96036-03-2) at subinhibitory concentrations (sub-MICs; 1/4, 1/8 and 1/16 of the MICs) were evaluated. Carbapenems at all sub-MICs tested (with the exception of 1/16 of the MICs in strain 378) decreased susceptibility of bacteria to serum bactericidal activity. All sub-MICs of the antibiotics tested also reduced the bacterial surface hydrophobicity. The surface hydrophobicity of strain 3259 was most effectively decreased after the exposure to imipenem and meropenem at 1/4 of the MICs (to 3% or 5.2% of the control values). The highest decrease of hydrophobicity in strain 378 was found after exposure to imipenem and meropenem at 1/16 of the MICs (19.2% or 32.3%).

Blood Bactericidal Activity↗

PubMed1998

Serum sensitivity and cell surface hydrophobicity of Klebsiella pneumoniae treated with gentamicin, tobramycin and amikacin.

A suppression of bacterial growth of Klebsiella pneumoniae after 30 min treatment with gentamicin, tobramycin and amikacin at suprainhibitory concentrations was found (postantibiotic effect, PAE). The antibiotics at a concentration of 2 x MIC induced PAEs in the range of 0.5-1.7 h, PAEs manifested by aminoglycosides at a concentration of 4 x MIC varied between 0.8-3.3 h. Susceptibility of exposed bacteria to serum bactericidal activity was efficiently enhanced compared with controls (without antibiotics). A survival of treated bacteria was between 12.7-36.6% (2 x MIC) or 5.0-8.3% (4 x MIC). The percentage of viable nontreated bacteria moved between 70.2-83.0% at these conditions. Surface hydrophobicity of bacteria exposed to aminoglycosides was only slightly increased. The results indicate that exposure of K. pneumoniae to a suprainhibitory concentrations of aminoglycosides in vitro enhanced the susceptibility of this strain to human serum bactericidal activity. Whether this phenomenon occurs in vivo, remains to be determined.

Amikacin↗

PubMed1998

Klebsiella pneumoniae clinical isolates: susceptibility to some antibiotics and surface hydrophobicity.

The susceptibility of Klebsiella pneumoniae strains isolated from the respiratory tract (55), urinary tract (19) and other human body sites (8) to the antibiotics, amoxycillin/clavulanate, cefuroxime, ceftazidime, gentamicin, norfloxacin, colistine, cotrimoxazole and oxolinic acid, as well as their surface hydrophobicity, were studied. The strains expressed a very high sensitivity to the antibiotics (94.7-100%). The surface hydrophobicity of the strains was evaluated by means of three assays and was minimal. The hydrophobicity manifested by adherence to xylene ranged between 0 and 10% for 96.4% of the respiratory strains, and for 100% of the urinary and other sites. Weak binding of Congo red (10-29 micrograms/10(10) cells) showed 96.4% of respiratory isolates as well as 100% of the urinary and other strains. Results of the salt aggregation test showed that 96.4% of respiratory strains and 100% of urinary and other strains aggregated only at 1.5 M, 2 M or higher concentrations.

Anti-Bacterial Agents↗

PubMed1998

Changes in serum sensitivity and hydrophobicity in a clinical isolate of Klebsiella pneumoniae treated with subinhibitory concentrations of aminoglycosides.

The effects of subinhibitory concentrations (sub-MICs) of gentamicin, netilmicin and amikacin on the serum sensitivity and the cell surface hydrophobicity of Klebsiella pneumoniae were investigated. At concentrations 1/16 or 1/8 of the MICs, in all antibiotics significantly enhanced the sensitivity of K. pneumoniae to human serum as compared to nontreated bacteria. The higher concentration of the antibiotics tested was more efficient. Survival of bacteria under these conditions ranged from 24.1% to 36.7% after incubation with 10% serum for 180 min when compared with the viability of the control bacteria. Bacteria grown with the test antibiotics at sub-MICs (1/8 or 1/4 of the MICs) manifested an effective decrease of the surface hydrophobicity. The aminoglycosides which were more effective at a concentration of 1/4 of the MICs reduced bacterial hydrophobicity to 28.5% (gentamicin), 14.8% (netilmicin) and 12.7% (amikacin) of the nontreated bacteria.

Amikacin↗