[Molecular biological and phenotypical characterization of human isolates of Salmonella enterica serovar Paratyphi B dT+ or Salmonella java]. / Molekulárno-biologická a fenotypová charakterizácia humánnych izolátov Salmonella enterica serovar Paratyphi B dT+, alebo Salmonella java.

OBJECTIVE: Salmonella Paratyphi B dT+ (or Salmonella Java) is an emerging public health problem. The study objective was to characterize phenotypically and genotypically 13 human isolates from sporadic cases of infection. MATERIAL AND METHODS: Phenotypic characteristics of 13 human isolates were determined by phage typing, disk diffusion method for testing antimicrobial susceptibility to 11 antibiotics and screening for selected virulence markers, i.e bacterial adherence to xylene, motility and biofilm formation. Genotypic characteristics of the study isolates were determined by PCR with primers for the detection of class 1 integrons, plasmid profile analysis and PFGE for the study of genetic diversity. RESULTS: The study isolates were classified into different phage types, with 3aI or 3aI variant being the most common (61.5%). All study isolates were resistant to streptomycin and sulfisoxazole, two of them were multiresistant (to streptomycin, sulfisoxazole, ampicillin and nalidixic acid). The study isolates showed low hydrophobicity, except for one isolate (2/08), and 5 isolates exhibited motility of > or = 50 mm. High biofilm formation was detected in 5 isolates. Class 1 integrons were not detected in any isolate and plasmid profile analysis revealed the presence of a 90-kb plasmid in 8 isolates. XbaI PFGE analysis differentiated the isolates into 6 pulsotypes (X1, X2, X2a, X3, X4,X5). CONCLUSION: Although the study set of S. Paratyphi B dT+ (S. Java) was small, the increasing emergence of this serovar in the human population in Slovakia is noteworthy. The results of gene analysis in PFGE suggest clonal diversity as well as a clonal link between strains of the predominant phage type. In view of possible increase in antimicrobial resistance and the spread of certain clones, continuous surveillance of strains of S. Paratyphi B dT+ is needed.

In vitro effect of subinhibitory concentrations of antibiotics on biofilm formation by clinical strains of Salmonella enterica serovar Typhimurium isolated in Slovakia.

AIMS: In this study, we examined the biofilm formation of 75 Salmonella enterica serovar Typhimurium (Salm. Typhimurium) human clinical isolates and the effect of subinhibitory concentrations (sub-MICs) of gentamicin, ciprofloxacin and cefotaxime on biofilm formation and exopolysaccharides (EPS) production. METHODS AND RESULTS: Quantification of biofilm formation and EPS production were carried out using a modified microtitre plate assay and spectrophotometric method, respectively. The results indicate that 38 isolates (50.7%), which are predominantly of DT104 phage type, presented as the strong biofilm producers in vitro on plastic surface. When strains with the highest biofilm-forming capacity were grown in the presence of sub-MICs of gentamicin and ciprofloxacin, the inhibition of biofilm formation and EPS production was observed. In contrast, cefotaxime at 1/2 MIC (0.039 microg ml(-1)) was able to significantly induce the production of biofilm as well as EPS in three isolates with nontypable and DT104 phage type, respectively. CONCLUSIONS: These results clearly indicate that all the three antibiotics tested are able to interfere with biofilm formation and EPS production by Salm. Typhimurium isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: The current study demonstrated that cefotaxime at sub-MIC can be beneficial for the behaviour of pathogen Salm. Typhimurium in vitro.

Oligonucleotide microarray for molecular characterization and genotyping of Salmonella spp. strains.

OBJECTIVES: To characterize and subtype multidrug-resistant Salmonella isolates by determining the virulence factors, prophage sequences and antimicrobial resistance genes using a novel Salmonella-specific oligonucleotide microarray. METHODS: Preliminary screening of 24 Salmonella clinical isolates was carried out by using susceptibility testing, plasmid profiling and class 1 integron PCR. Subsequently, oligonucleotide microarray was involved in genotypic characterization and localization of monitored genetic markers. The presence of antimicrobial resistance genes was also detected and confirmed by PCR and subsequent sequencing. The potential spread of emerging bla(SHV-2) was investigated by bacterial conjugation. RESULTS: All Salmonella strains revealed resistance to two or more (up to nine) antibiotics. Nineteen of them carried class 1 integrons including dfrA1, dfrA12, aadA1, aadA2, bla(PSE-1) and bla(TEM-1) gene cassettes, respectively. Twenty-three out of 24 Salmonella isolates possessed one or more plasmids. Oligonucleotide microarray characterization and typing revealed the conserved character of Salmonella pathogenicity island virulence factors among three Salmonella enterica serovars, significant variability in prophage sequences and many different antimicrobial resistance gene patterns. Differential labelling of genomic and plasmid DNA, respectively, and hybridization to the microarray made it possible to localize important resistance determinants. Microarray results were successfully confirmed and verified by using PCR. The emerging bla(SHV-2) gene from Salmonella Kentucky SK10944 conferring resistance to ceftriaxone and cefotaxime was transferred via bacterial conjugation to Escherichia coli K-12 3110. CONCLUSIONS: Salmonella isolates were quickly and thoroughly characterized by a novel oligonucleotide microarray, which could become a useful tool for detection of virulence and resistance genes and monitoring of their dissemination among salmonellae and closely related bacteria.

[Phage types and virulence markers of clinical isolates of Salmonella enteritidis]. / Fágotypy a markery virulencie klinických izolátov Salmonella enteritidis.

A set of 487 clinical isolates of Salmonella Enteritidis were phage typed and analyzed for virulence markers, i.e. bacterial cell surface hydrophobicity, motility, biofilm formation and the presence of a 60 kb serovar-specific virulence plasmid. The most frequent phage type was PT8 (48.3%), followed by PT13a (7.2%), PT15 (6.4%), and PT4 (4.5%). Thirty-one (6.4%) strains were non-typeable. As many as 128 (26.3%) strains showed hydrophobicity in the hydrocarbon xylene adherence assay, with the highest percentages of highly hydrophobic strains being found among the following phage types: PT9a (84.6%), PT25 (81.8%), PT15 (54.8%) and PT8 (23.4%). Motility > or = 50 mm was observed in 294 (60.4%) strains and visible biofilm was formed in the test tube assay in different degrees by 448 (91.9%) strains. The capacity of in vitro biofilm formation is indicative of a high virulence potential of the study strains. The 60 kb serovar-specific virulence plasmid was present in 467 (95.9%) strains. Clear correlation between phage types and particular virulence markers was not revealed in the study set of strains. The obtained in vitro results are suggestive of flexibility of Salmonella Enteritidis in infecting the host.

[In vitro activity of commercially available disinfectants against Stenotrophomonas maltophilia]. / Aktivita komercne vyrábaných dezinfektantov voci Stenotrophomonas maltophilia in vitro.

In vitro antibacterial efficacy of 14 commercially available disinfectants against the hospital pathogen Stenotrophomonas maltophilia was tested. The test disinfectants included 5 "pure" quartenary ammonium compounds (QACs) and 9 combination formulations with QACs as the major ingredient. Antibacterial efficacy was expressed as MIC, ED50 and inhibition of the rate of incorporation of radioactive precursors [14C] adenine and [14C] leucine. Based on their activity, the disinfectants were divided into four groups. Group I characterized by high inhibitory activity (MIC 0.045-0.09 microg/ml) comprised benzalconium chloride and Triquart. Group II included formulations with good antibacterial activity (MIC 0.19-0.78 microg/ml) while group III formulations showed MICs between 1.56 and 25 microg/ml. The less active Cetrimid (MIC 50-100 microg/ml) was classified into group IV. When effects on biosynthetic processes expressed as R values (IC50 Ade : IC50 Leu) were tested, R < 1 was only recorded for the following formulations: Hexaquart plus, Diesen forte, Sokrena, Forten, ID 212 and Cetrimid. Lower values of IC50 Ade and IC50 Leu are suggestive of effects on the synthesis of nucleic acids and proteins leading to inhibition of the two precursors. Endogenous respiration was almost 50% inhibited by Cetrimid and Microbac forte at a concentration of 0.78 microg/ml, and 100% inhibited by Almyrol, Diesen forte and Microbac forte at a concentration of 6.25 microg/ml and by FD312, Triquart, Hexaquart plus, Hexaquart S, ID 212, TPH 5225 at a concentration of 12.5 microg/ml.

The virulence markers of Salmonella enterica serovar Typhimurium. Different phage-type strains isolated in Slovakia.

Phage-typing determination of cell-surface hydrophobicity, motility, and serovar-specific virulence plasmid was performed in a collection of 154 clinical isolates of S. enterica serovar Typhimurium (SeT) isolated in Slovakia. All isolates were also examined in PCR for the presence of both stn (enterotoxin) and iroB (siderophore) genes. The DT104 was the definitive phage type most frequently identified (37.7 %), the second most frequently isolated phage type was DT41 (5.8 %); the occurrence of other phage types was not epidemiologically significant. On the basis of virulence-marker investigation, 46.1 % of isolates were hydrophobic in the assay of bacterial adherence to xylene, and 97.4 % were hydrophobic in salt-aggregation test. Motility of more than 50 mm was expressed by 20.8 % isolates. The serovar-specific 90-kb virulence plasmid was contained in 138 (89.6 %) of isolates. All SeT isolates were found (according to PCR) to carry the Salmonella-enterotoxin (stn) gene and the siderophore (iroB) gene. The increasing incidence of SeT DT104 human strains in Slovakia requires continuous attention; this can be markedly improved by surveillance efficiency and made possible by determining relationships between sporadic isolates.

Molecular epidemiology of Salmonella enterica serovar Enteritidis strains by pulsed-field gel electrophoresis isolated in the Slovak Republic.

A total 44 isolates of S. enterica serovar Enteritidis (S. Enteritidis) belonged to three different phage types (PTs) 9a, 13a, 25 were analyzed by the technique of pulsed-field gel electrophoresis (PFGE). Thirty and three strains were from two outbreaks (central and southern regions of the Slovak Republic PTs 13a, 25) and 11 isolates were sporadic isolates (PT9a). These isolates showed two different patterns in PFGE with XbaI digestion. Strains of PT13a generated PFP A and isolates of PT25 showed uniform PFP B. Nine sporadic isolates of PT9a belonged to PFP A and two isolates to PFP B. The PFPs A and B were differed by only two bands. The distribution of XbaI profiles did not corresponded with PTs. We conclude that the close genetic similarity observed between epidemiologically unrelated and outbreak-related isolates of S. Enteritidis suggest clonal relationship of these isolates.

[Effect of disinfectants on surface hydrophobicity and mobility in Salmonella enterica serovar Typhimurium DT104]. / Vplyv dezinfekcných látok na povrchovú hydrofobicitu a motilitu Salmonella enterica sérovar Typhimurium DT104.

The paper evaluated antibacterial efficacy of 12 disinfectants on the basis of quaternary ammonium compounds (KAZ) on the isolates of Salmonella enterica serovar Typhimurium of the definitive phage type 104 (DT104). One isolate--5551/99--represented the multiresistant phenotype, resistant to ampicillin (A), chloramphenicol (C), streptomycin (S), and tetracycline (T). The second isolate--577/99--was sensitive to all antibiotics tested. The present study further examined the capability of sub-MIC concentrations of disinfectants to intervene into surface hydrophobicity and motility of the strains tested. The results showed that all disinfectants under study exhibited high antibacterial activity. It is of interest that the isolate resistant to antibiotics was more sensitive to disinfectants in comparison with the isolate resistant to antibiotics. The most effective substances against strain 5551/99 (R-type) were Sokrena, Triquart, Hexaquart plus, ID213, and Microbac forte, and those most effective against strain 577/99 (S-type) were Benzalkonium chloride and Hexaquart plus (MIC 0.09-0.19 microliter/ml). Surface hydrophobicity of both tested strains after the action of sub-MIC (1/16, 1/8, 1/4 of MIC) of disinfectants was not influenced in a more marked way. In the case of strain 5551/99, the highest percentage of inhibition of adherence to xylene, to 69.5% versus the control, was produced by 1/4 of MIC of the substance Triquart and, in the whole concentration range, by the substance Microbac forte. After the action of most substances to strain 577/99, stimulation of adherence took place. Only substance ID213 induced inhibition of adherence in the whole concentration range. The salt-aggregative capabilities of both strains were not influenced in a more marked way. The only exceptions were the action of 1/4 of MIC of the substances Cetrimid, Sokrena, ID212, Forten, and 1/8 of MIC of Hexaquart S on strain 577/99, where a decrease in hydrophobicity was observed. A moderate inhibition of motility was found after the action of 1/4 of MIC of Benzalkonium chloride (to 87.5%) and A.D.L. 007 (to 85.2%) on strain 5551/99. In the case of sensitive isolate 577/99, the most markedly manifested inhibition effect was that of Sokrena within the whole concentration range and that of 1/4 of MIC ID213. The results can be used in the selection of a suitable disinfectant for decontamination of solid surfaces. The effect of substances under study on surface hydrophobicity and motility of the important, food-transferred pathogen in the sense of inhibition or stimulation points out to intervention into its pathogenic potential.

Effect of disinfectants on the metabolism of Salmonella enterica serovar enteritidis.

Antimicrobial activity of 19 commercially manufactured disinfectant substances on a Salmonella enteritidis strain was determined. The substances represented 8 quaternary ammonium salts (QAS) and 10 QAS combined with other additives. The antimicrobial efficacy was characterized by influencing the growth of bacterial cells expressed as MIC and ED50 values as well as by the inhibition of the incorporation rate of 14C-adenine and 14C-leucine. According to their efficacy the disinfectants were divided into three groups: (1) substances with strong inhibitory effect (MIC 6-45 micrograms/L) such as Diesin forte, Hexaquart plus, Neoquat S, Triquart, Almyrol, Hexaquart S, ID212, ID213 and Microbac forte; (2) substances with good antibacterial efficacy (MIC 90-780 micrograms/L); (3) substances with MIC values > 780 micrograms/L (up to 3120 micrograms/L). Cetrimide had very low activity (MIC 3.12-6.25 mg/L). The effect of disinfectants on the biosynthetic processes was expressed by R values (IC50(Ade):IC50(Leu)); all these values were < 1 except Benzalkonium chloride, FD312, Divoquat forte, 5P plus, Almyrol, Hexaquart S and Hexaquart plus. Low R values suggested interference of these substances with the synthesis of both nucleic acids and proteins. All substances except 5P plus caused an inhibition of endogenous respiration. The most effective were Almyrol, Diesin forte, Microbac forte and Neoquat which completely inhibited respiration at 190 mg/L. Kvart showed the lowest effect on the respiration over the whole concentration range. The disinfectants also suppressed growth of S. enteritidis, probably by interfering with energy-yielding and-requiring processes in the cells.

Toxinogenicity and markers of pathogenicity of Pseudomonas aeruginosa strains isolated from patients with tumor diseases.

Potential virulence factors (elastase, proteinase, lipase, phospholipase C, alginate) as well as surface properties (hydrophobicity, motility) were determined in 103 Pseudomonas aeruginosa strains isolated from patients with cancer. Nontypable strains were the dominant group (60%), followed by serotypes O11 (17%), O12 (7%) and O4 (5%). Seventy-one strains (69%) produced high level of elastase (10-60 mg/L), 87% of the strains possessed high activity of proteinase (bacterial) (10-250 mg/L) and 69% of the strains demonstrated higher level of lipase (20-150 U/mL); these elevated levels of enzymes were associated mainly with nontypable strains. On the other hand, 79% of the strains did not produce or produced only a low level of phospholipase C and 60% of isolates did not manifest any or very low production of alginate. Hydrophobicity demonstrated by adherence of the bacteria to xylene was shown by 69% of strains; 94% of strains aggregated with ammonium sulfate. Motility in the range of 31-80 mm was found in 76 strains (74%). The considerable virulence of tested P. aeruginosa strains was confirmed. The nontypable strains manifested the most frequent group with high level of elastase, proteinase, lipase, hydrophobicity and motility.

Antibacterial efficacy of disinfectants against some gramnegative bacteria.

The antibacterial effect of 11 new commercially manufactured disinfectants on clinical isolates of Salmonella typhimurium DT104, Serratia marcescens and Pseudomonas aeruginosa was studied. The substances tested represented six pure quaternary ammonium substances (QAS) and five QAS combined with other ingredients. The antibacterial efficacy was characterized by influencing the growth of bacterial cells expressed by MIC and ED50 values. The disinfectants are divided into three groups according to their efficacy. The antibacterial efficacy of disinfectants on S. typhimurium DT104 in the study is the highest in comparison with S. marcescens and P. aeruginosa strains. The highest inhibition of growth was caused by Diesen forte on S. typhimurium DT 104 and by Benzalkonium chloride on both S. marcescens and P. aeruginosa strains.

[Characteristics of strains of Salmonella enterica serovar Typhimurium DT104 isolated in the Slovak Republic]. / Charakterizácia kmenov Salmonella enterica sérovar Typhimurium DT104 izolovaných v SR.

From 1997 to 2000 in the Slovak Republic 8 strains of Salmonella enterica serovar Typhimurium DT104 were isolated from sporadic cases of human salmonellosis. Four strains were multiresistant and three strains were sensitive to antibiotics. We investigated the influence of the cultivation medium (complete Müeller-Hinton, synthetic-Staples) on growth, surface hydrophobicity and motility of the mentioned isolates. The hydrophobicity was evaluated by methods of adherence to the hydrocarbon xylene (BATH) in a salt-aggregation test with ammonium sulphate (SAT) and adherence to a plast. The growth of tested strains in 24 hours was greater after cultivation in the complete medium, but the salmonellae grew considerably also in the synthetic medium where the only source of C and N was asparagine. Of the investigated characteristics the cultivation medium influenced most the adherence of isolates to xylene as after cultivation in a synthetic medium all isolates with the exception of two were hydrophobic. The motility of strains was also greater after growth in this medium. Conversely cultivation in complete medium suppressed these properties of isolates. The cultivation medium did not influence the adherence of isolates to plasts and only a slight influence was observed on the salt aggregating properties of the investigated strains.

[Effect of subinhibitory levels of aminoglycosides and fluoroquinolines on hydrophobicity and motility of Serratia marcescens]. / Ucinok subinhibicných koncentrácií aminoglykozidov a fluorochinolónov na hydrofobicitu a motilitu Serratia marcescens.

The authors investigated the effect of subinhibitory quinolone concentrations (ciprofloxacin, enoxacin, norfloxacin, ofloxacin, pefloxacin) and aminoglycosides (amicacin, gentamicin, netilmicin, tobramycin) on the surface hydrophobicity and motility of the clinical isolate of Serratia marcescens. The hydrophobicity was evaluated by methods of adherence to the hydrocarbon xylene (BATH) in a salt-aggregation ammonium sulphate (SAT) test. The tested quinolones in subinhibitory concentrations inhibited the adherence of S. marcescens to xylene with the exception of 1/16 MIC ofloxacin where slight stimulation took place. The most marked inhibition of adherence was observed after the action of 1/4 MIC ciprofloxacin (to 13.2%) and pefloxacin (to 31.0%) as compared with the control. Among aminoglycosides netilmicin markedly inhibited the adherence over the whole range of concentrations, whereby 1/8 MIC suppressed it to 0.7%. With these data correlated also the results of the salt-aggregation test. The investigated antibiotics did not have a major effect on the motility of S. marcescens.

Influence on Enterobacter cloacae metabolism, cell-surface hydrophobicity and motility of suprainhibitory concentrations of carbapenems.

The impact of postantibiotic effect (PAE) of carbapenems (imipenem, meropenem) on the metabolism (biosynthesis of macromolecules, respiration), cell-surface hydrophobicity and motility of a clinical isolate of Enterobacter cloacae was examined. The metabolism was evaluated after 16 h and after 1 d of cultivation using 2x and 4x minimum inhibitory concentrations (MIC) of both antibiotics for the induction of PAE. Imipenem at 4 x MIC did not induce PAE. After a 16-h cultivation (in the postantibiotic phase of both carbapenems), inhibition of nucleosynthesis and protein synthesis was found; after a 1-d cultivation, during regrowth stimulation of mainly 14C-leucine incorporation was found. The presence of the exogenous intermediates of citrate cycle, viz. 2-oxoglutarate, increased the respiratory activity of the cells. The cell-surface hydrophobicity (evaluated by three methods--bacterial adhesion to hydrocarbon, nitrocellulose-filter test and salt-aggregation test) decreased after PAE of both carbapenems; meropenem was more effective. Motility (an important virulence factor) was inhibited in the postantibiotic phase of both carbapenems; the 4 x MIC caused a higher inhibition.

Effect of suprainhibitory concentrations of quinolones on hydrophobicity and motility of Serratia marcescens.

The effect of suprainhibitory concentrations of quinolones (ciprofloxacin, enoxacin and norfloxacin) on the growth, hydrophobicity and motility of a nosocomial pathogen Serratia marcescens was studied. A postantibiotic effect (PAE) was induced by 2x of 4x MIC concentrations for 0.5 h. By using the 2x MIC concentrations all three quinolones induced equally long PAE approximately 1 h. The longest PAE of 5.4 h at 4x MIC concentration was induced by enoxacin. The results obtained showed that suprainhibitory concentrations of quinolones significantly stimulated the adhesion of S. marcescens to xylene, with the exception of enoxacin, which inhibited the adhesion to 61.2% at 4x MIC concentration. These results correlated with those in the salt aggregation test. The adhesion of strains to nitrocellulose filters did not influence the aftereffect of suprainhibitory concentrations of quinolones. Exposure of bacterial cells to suprainhibitory concentrations of ciprofloxacin and norfloxacin caused a reduction in motility, while this effect was more distinct at 4x MIC concentration. The results suggest that any consideration of postantibiotic effects should include the residual antibiotic effects on virulence factors, in addition to the defined suppression of bacterial regrowth.

Effect of new quaternary bisammonium compounds on the growth and cell surface hydrophobicity of Enterobacter cloacae.

The effect of new quaternary bisammonium salts (QBAS) of series A: 1, 10-[bis(alkyldimethyl-diammonium)]-4,7-dioxo-3,8-dioxoundecandi bromides and series B: alpha-omega[bis(dodecyldimethyl-diammonium)]-3,x-dioxo-4,y- dioxoalcandibromides on the growth and surface hydrophobicity of E. cloacae strain was studied. The compounds of series A possess changing side substituent and the inhibition of growth displayed evident dependence of effect on length of alkyl with optimum at C9-C11 (cut off effect). In series B are compounds with changing joining chain between two ammonium cations where the mentioned effect was not observed. The cell surface hydrophobicity of tested strain was determined by the method of adhesion to hydrocarbon--xylene (BATH) and in salt aggregation test of ammonium sulphate (SAT). The effect of 1/4 of the MIC compounds series A with nonyl, decyl and undecyl reduced the adhesion of E. cloacae cells below 50% against the control. These compounds at sub-MICs decreased salt-aggregative ability of E. cloacae cells. The influencing of cell surface hydrophobicity was not found after affecting of compounds at sub-MIC from series B with the exception of moderate decrease at compound with joining chain of C7. The length of chain connecting two symmetrical parts of molecule has slight impact on the effect of bisammonium salts. The influence of QBAS at sub-MICs on cell surface hydrophobicity can interfere with pathogenic potential of E. cloacae.

Postantibiotic effects of gentamicin and netilmicin on Serratia marcescens: effects on hydrophobicity and motility.

The impact of postantibiotic effect (PAE) of aminoglycosides (gentamicin, netilmicin) on cell-surface hydrophobicity and motility of a clinical isolate Serratia marcescens was evaluated. For the induction of PAE 2x and 4xMIC concentrations of both antibiotics were used. Gentamicin and netilmicin induced a PAE of similar duration after 2xMIC concentration (2.7 and 2.8 h, respectively). Both aminoglycosides demonstrated concentration-dependent PAE. At a concentration of 4xMIC they produced PAEs of 5.9 and 8.2 h, respectively. The evaluation of hydrophobic properties of S. marcescens after affecting PAE showed that both aminoglycosides inhibited adherence to xylene. This inhibition was also concentration-dependent. More expressive was netilmicin which inhibited the adhesion by 70.5% at 2xMIC and by 85.2% at 4xMIC. Netilmicin inhibited also the adhesion to nitrocellulose filter by 34.7% at 4xMIC. Exposure of the bacterial cells to suprainhibitory concentrations of both aminoglycosides resulted only in moderate inhibition of motility of strain tested compared to the unexposed cells.

The effect of new disinfectant substances on the metabolism of Enterobacter cloacae.

The antimicrobial mechanism of 16 new commercially manufactured disinfectant substances on an Enterobacter cloacae strain was studied. The substances tested represent 11 quaternary ammonium salts (QAS) and five combinated QAS with other ingredients. The antimicrobial efficacy was characterized by influencing the growth of bacterial cells expressed by MIC and ED50 values as well as by the inhibition of the incorporation rate of [14C] adenine and [14C] leucine. The disinfectants are divided into three groups according to their efficacy. The first group comprised substances with strong inhibitory effect (MIC 0.006-0.048 mg l(-1)) such as triquart, topax 91, benzalkonium chloride, neoquat S, ID 213, and antibacteric P. The second group represented substances with good antibacterial efficacy (MIC 0.048-0.15 mg l(-1)), and the third group were substances with MIC values up to 0.195-0.39 mg l(-1). Cetrimide had low activity (MIC 3.12-6.25 mg l(-1)). The effect of substances studied on the biosynthetic processes expressed by R values (IC50 Ade:IC50 Leu) showed that these values were < 1 except ADL 007. Much lower IC50 Ade and IC50 Leu values of the disinfectant substances studied suggested interference of these substances with nucleic acid synthesis and proteins synthesis which was expressed by inhibition of both precursors. All substances except cetrimide caused an inhibition of the endogenous respiration. The highest inhibition was caused by benzalkonium chloride. This affected the respiration significantly in the presence of intermediators of the Krebs' cycle (glycerol, aspartate). The tested substance suppressed the growth of E. cloacae probably through interference with energy-yielding and energy-requiring processes of the cells.

Postantibiotic effect of some antibiotics on the metabolism of Pseudomonas aeruginosa.

The influence of the postantibiotic effects (PAEs) of ciprofloxacin, pefloxacin, imipenem, meropenem and amikacin in the suprainhibitory concentrations (2 x and 4 x MIC) on the metabolic processes of P. aeruginosa was studied. The synthesis of macromolecules was expressed by influencing of the incorporation rate of [14C] adenine and [14C] leucine. Remarkable affecting of both biosynthetic processes evoked the suprainhibitory concentration 4 x MIC of meropenem by inhibition of the nucleic acids synthesis to 76.1% and proteins synthesis to 61.1% against the control. The suprainhibitory concentration 4 x MIC of both pefloxacin and ciprofloxacin affected the highest suppression of the endogenous respiration to 16.5% and to 20.3%, respectively. The respiration was influenced the least after the effect of meropenem in the both suprainhibitory concentrations tested. According to our knowledge, this is first report about the evaluation of the endogenous respiration after PAE. In this study we demonstrated the inhibitory effects of 4 x MIC concentration of antibiotics studied on the metabolic processes of P. aeruginosa. The results suggest a multiple mechanism for the PAE.