Antimicrobial resistance of human Salmonella enterica serovar Typhimurium U302 strains: prevalence of R-type ASSuT in Slovakia, 2006-2011.

Salmonella enterica serovar Typhimurium is a common cause of non-typhoid salmonellosis in humans. Since 2006, an increase in the human infections caused by U302 phage type in Slovakia has been documented and, from 2006 to 2011, a total of 291 U302 human strains were isolated. Antimicrobial susceptibility testing demonstrated that these strains had a high overall antimicrobial resistance and 244 (83.8%) of the tested strains were multidrug-resistant (MDR). The most prevalent resistance was to ampicillin, streptomycin, sulfisoxazole, and tetracycline (R-type ASSuT), which was verified in 87 (29.9%) strains. The annual rate of this resistance type varies, but the largest number of these strains were identified in 2009 and 2010. The classical pentaresistance phenotype (R-type ACSSuT), characteristic of the DT104 phage type, was found only in 40 (13.7%) U302 strains. These results suggested that although the prevalence of DT104 phage type has decreased, ASSuT as well as ACSSuT resistance markers continue to circulate. Therefore, continual surveillance of the occurrence of these and similar MDR phage types is necessary.

Detection of the class 1 integrons and SGI1 among Salmonella enterica Serovar Typhimurium DT104, U302, DT120, DT193, and nontypable human isolates.

Salmonella enterica serovar Typhimurium strains of particular phage types, such as DT104, U302, DT120, DT193, and nontypable strains, are often characterized by resistance to multiple antibiotics. This antibiotic resistance can be caused by the presence of the integrons, transposons, Salmonella genomic island 1 (SGI1), or conjugative plasmids. In this study we were interested in the relative contribution of integrons and SGI1 to the antibiotic resistance of the four mentioned phage types and nontypable S. Typhimurium human strains. Altogether 193 isolates were characterized for antibiotic susceptibility, presence of class 1 integrons, and the left junction of SGI1. Based on the presence of class 1 integrons and the left junction of SGI1, all strains could be clustered into three groups. The first group consisted of 69 strains positive for both the class 1 integrons and the left junction of SGI1. The strains of this group belonged mainly to DT104, U302, and DT120 phage types with resistance phenotype ACSSuT or ACSSuTNA. The second group comprised 9 strains which were positive only for the presence of class 1 integrons. In this group were some strains of multiple-antibiotic-resistant phage types: DT120, DT193, U302; and nontypable. The third group consisted of 115 strains in which neither the class 1 integrons nor the left junction of SGI1 were detected. Although the isolates were resistant to 2-8 antibiotics, the most frequent resistance type of these strains were ASSuT and SSu. By nucleotide sequencing of class 1 integrons PCR amplicons, the following embedded gene cassettes were determined: aadA1, aadA2, aadA5, aadA7, bla(PSE-1), sat1, dfrA1; and dfrA14. Our study shows a high prevalence and diversity of class 1 integrons embedded antimicrobial gene cassettes and their strong association with SGI1.

[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.

Molecular characterization of the multidrug-resistant phage types Salmonella enterica serovar Typhimurium DT104, DT20A and DT120 strains in the Slovakia.

An increase in the number of multidrug-resistant Salmonella enterica serovar Typhimurium strains (definitive phage type DT20a and DT120) as well as the occurrence of DT104 strains during 2003-2005 in Slovakia was documented. Based on the results of the molecular analysis we suggest that multidrug-resistant DT20a and DT120 phage types are more closely related to multidrug-resistant phage type, and that the occurrence is probably due to changes in the phage susceptibility of DT104. Continued surveillance and molecular analysis should be maintained to follow the spread of these new multidrug-resistant DT104 variants in animals and humans.

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.

Molecular characterization of class 1 integrons in clinical strains of Salmonella typhimurium isolated in Slovakia.

The presence of class 1 integrons was investigated in 156 epidemiologically unrelated Salmonella Typhimurium isolates. Of these 156 isolates, 70 were of definitive phage type DT104 and 86 were strains of various phage type, RDNC and untypable, designated here as non-DT104 strains. Integrons were found in 47 of DT104 isolates (67.1%), while in all strains with characteristic pentaresistance (R-type ACSSuT) two integrons 1.0 kb and 1.2 kb in size were found. Among 86 non-DT104 strains, integrons with sizes of 1.6 kb and 1.9 kb in four multidrug-resistant strains DT193 and U302 were found. The integrons from selected strains were further sequenced and the aadA1, aadA2, dhfr1, dhfr12 and bla(PSE) genes were found embedded in cassettes.

Salmonella enterica serovar Kentucky: antimicrobial resistance and molecular analysis of clinical isolates from the Slovak Republic.

A collection of 68 isolates of Salmonella enterica serovar Kentucky collected during the period 2003-2004 from humans in two geographical regions in the Slovak Republic was studied. The original isolate of this serovar was associated with travel to Egypt, and the emergence of other isolates was due to the nosocomial spread of this strain in two hospitals. Antimicrobial susceptibility testing, class I integrons content, pulsed-field gel electrophoresis (PFGE) analysis and plasmid DNA profiles were performed on all isolates. A high proportion (89.7%) of the isolates was multidrug-resistant, while 67 strains expressed resistance against ciprofloxacin. By sequence analysis of randomly selected strains, the point mutations in quinolone resistance-determining region of the DNA gyrase were found. The S. Kentucky isolates investigated were determined to be clonally related by PFGE as well as plasmid DNA analysis.

[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.

Analysis of integrons in human isolates of Salmonella enterica serovar typhimurium isolated in the Slovak Republic.

About 110 sporadic, epidemiologically unrelated Salmonella enterica serovar typhimurium strains isolated in the Slovak Republic were analyzed for the presence of integrons. Of these 110 examined strains, 47 were of definitive phage type DT104 and 63 were strains of various phage type, RDNC and untypeable, designated here as non-DT104 strains. All isolates were also tested for antimicrobial resistance to 10 antibiotics as well as for the presence of virulence plasmid. Of 63 non-DT104 strains, 15 isolates were multiple-resistant, independently from phage type, other strains were resistant to one, two or three drugs. Resistance to ampicillin, streptomycin, tetracycline and sulfisoxazole was most frequently observed. Among the DT104 isolates up 65.9% exhibited characteristic pentaresistance--ACSSuT phenotype. The integron content was studied in PCR experiments using a 5'-CS/3'-CS primer pair. Fourteen non-DT104 strains, independently from phage type, were found to carry integrons with amplicons 650-1900 bp in size. Thirty-six DT104 strains contained integrons of 1000 and 1200 bp and 31 of they exhibited the ACSSuT phenotype. No integron was found in 10 DT104 strains, which included strains mostly resistant only to streptomycin, tetracycline and sulfisoxazole. The majority of non-DT104 strains did not possess any integrons. Our findings show the widespread existence of both resistant and multiple-resistant epidemiologically unrelated Salmonella typhimurium strains and suggest that integrons contribute to this antimicrobial resistance. The presence of 90-kb virulence plasmid in the 54 non-DT104 and in the all DT104 strains was found.

[Occurrence of phage types of non-typhoid Salmonella serovar in the Slovak Republic 2000-2003]. / Výskyt fágotypov netýfusových sérovarov salmonel v Slovenskej republike v rokoch 2000-2003.

Salmonellae of non-typhoidal serovars are the most important pathogens involved in foodborne diseases in humans all over the world. The incidence rates of two major Salmonella serovars, i.e. S. enterica serovar Enteritidis (S. Enteritidis) and S. enterica serovar Typhimurium (S. Typhimurium), in the Slovak Republic in 2000-2003 are given. Over the period studied, 829 S. Enteritidis strains and 258 S. Typhimurium strains isolated from patients with salmonellosis were investigated in the National Reference Centre for Salmonella Phage Typing. The S. Enteritidis strains were differentiated into 16 phage types, with phage type 8 being dominant since found in 73.6%, 53.8%, 62.8% and 45.6% of strains in 2000, 2001, 2002 and 2003, respectively. The following most frequent phage types were 4 and 13a. New phage types, i.e. 15, 5, 25 and 14b, were identified from salmonellosis outbreaks in 2003. The S. Typhimurium strains were also differentiated into 16 phage types with phage type DT104 strains being prevalent and showing an increase from 7.4% in 2000 to 44.6% in 2003; 54.2% of them were resistant and of R type ACSSut. The second most frequent phage type in 2000-2001 was 2b in 2003 DT41. The frequency of the other phage types was not epidemiologically significant.

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.