The Prolonged Treatment of Salmonella enterica Strains with Human Serum Effects in Phenotype Related to Virulence

Salmonella enterica as common pathogens of humans and animals are good model organisms to conduct research on bacterial biology. Because these bacteria can multiply in both the external environments and in the living hosts, they prove their wide adaptability. It has been previously demonstrated that prolonged exposition of Salmonella serotype O48 cells to normal human serum led to an increase in resistance to sera in connection with the synthesis of very long O-antigen. In this work, we have studied the phenotype connected to virulence of Salmonella enterica strains that were subjected to consecutive passages in 50% human serum from platelet-poor plasma (SPPP). We found that eight passages in SPPP may not be enough for the bacteria to become serum-resistant (S. Typhimurium ATCC 14028, S. Senftenberg). Moreover, C1q and C3c complement components bound to Salmonellae (S. Typhimurium ATCC 14028, S. Hammonia) membrane proteins, which composition has been changed after passaging in sera. Interestingly, passages in SPPP generated genetic changes within gene fljB, which translated to cells’ motility (S. Typhimurium ATCC 14028, S. Erlangen). One strain, S. Hammonia exposed to a serum developed a multi-drug resistance (MDR) phenotype and two S. Isaszeg and S. Erlangen tolerance to disinfectants containing quaternary ammonium salts (QAS). Furthermore, colonial morphotypes of the serum adaptants were similar to those produced by starter cultures. These observations suggest that overcoming stressful conditions is manifested on many levels. Despite great phenotypic diversity occurring after prolonged exposition to SPPP, morphotypes of colonies remained unchanged in basic media. This work is an example in which stable morphotypes distinguished by altered virulence can be confusing during laboratory work with life-threatening strains.

Benefits of Usage of Immobilized Silver Nanoparticles as Pseudomonas aeruginosa Antibiofilm Factors

The aim of this study was to assess the beneficial inhibitory effect of silver nanoparticles immobilized on SiO2 or TiO2 on biofilm formation by Pseudomonas aeruginosa-one of the most dangerous pathogens isolated from urine and bronchoalveolar lavage fluid of patients hospitalized in intensive care units. Pure and silver doped nanoparticles of SiO2 and TiO2 were prepared using a novel modified sol-gel method. Ten clinical strains of P. aeruginosa and the reference PAO1 strain were used. The minimal inhibitory concentration (MIC) was determined by the broth microdilution method. The minimal biofilm inhibitory concentration (MBIC) and biofilm formation were assessed by colorimetric assay. Bacterial enumeration was used to assess the viability of bacteria in the biofilm. Silver nanoparticles immobilized on the SiO2 and TiO2 indicated high antibacterial efficacy against P. aeruginosa planktonic and biofilm cultures. TiO2/Ag0 showed a better bactericidal effect than SiO2/Ag0. Our results indicate that the inorganic compounds (SiO2, TiO2) after nanotechnological modification may be successfully used as antibacterial agents against multidrug-resistant P. aeruginosa strains.

Consequences Of Long-Term Bacteria's Exposure To Silver Nanoformulations With Different PhysicoChemical Properties

Purpose

Resistance to antibiotics is a major problem of public health. One of the alternative therapies is silver – more and more popular because of nanotechnology development and new possibilities of usage. As a component of colloid, powder, cream, bandages, etc., nanosilver is often recommended to treat the multidrug-resistant pathogens and we can observe its overuse also outside of the clinic where different physicochemical forms of silver nanoformulations (e.g. size, shape, compounds, surface area) are introduced. In this research, we described the consequences of long-term bacteria exposure to silver nanoformulations with different physicochemical properties, including changes in genome and changes of bacterial sensitivity to silver nanoformulations and/or antibiotics. Moreover, the prevalence of exogenous resistance to silver among multidrug-resistant bacteria was determined.

Materials and Methods

Gram-negative and Gram-positive bacteria strains are described as sensitive and multidrug-resistant strains. The sensitivity of the tested bacterial strains to antibiotics was carried out with disc diffusion methods. The sensitivity of bacteria to silver nanoformulations and development of bacterial resistance to silver nanoformulations has been verified via determination of the minimal inhibitory concentrations. The presence of sil genes was verified via PCR reaction and DNA electrophoresis. The genomic and phenotypic changes have been verified via genome sequencing and bioinformatics analysis.

Results

Bacteria after long-term exposure to silver nanoformulations may change their sensitivity to silver forms and/or antibiotics, depending on the physicochemical properties of silver nanoformulations, resulting from phenotypic or genetic changes in the bacterial cell. Finally, adaptants and mutants may become more sensitive or resistant to some antibiotics than wild types.

Conclusion

Application of silver nanoformulations in the case of multiple resistance or multidrug-resistant bacterial infection can enhance or decrease their resistance to antibiotics. The usage of nanosilver in a clinic and outside of the clinic should be determined and should be under strong control. Moreover, each silver nanomaterial should be considered as a separate agent with a potential different mode of antibacterial action.

Preparation and preliminary evaluation of bio-nanocomposites based on hydroxyapatites with antibacterial properties against anaerobic bacteria

Hexagonal nanocrystalline powders of the non-doped Ca₁₀(PO₄)₆(OH)₂ as well as activated with Ag⁺ and Eu³⁺ ions were synthesized by using different wet chemistry methods. Moreover, the obtained hydroxyapatite was loaded with Ag⁰, as well as nitroimidazole antimicrobials: metronidazole and tinidazole. The structural properties of the products were analyzed by X-ray diffraction (XRD), scanning (SEM) and transmission (TEM) electron microscopy as well as infrared (IR) and Raman spectroscopy. The photoluminescence properties of the Eu³⁺ and Ag⁺ co-doped Ca₁₀(PO₄)₆(OH)₂ were characterized via the PL emission, excitation spectra and the luminescence decay curve. The antimicrobial activity of the obtained materials against Prevotella bivia and Parabacteroides distasonis was studied. The cytotoxicity assessment was carried out on the human osteosarcoma cell line (U2OS) as well as human red blood cells (RBC). The choice of the in vitro model was based on the fact that U2OS is a cancer cell line derived from bone tissue which is rich in apatites that play a pivotal role in the extracellular matrix formation. RBCs are the most abundant blood cells and they are used as a cell model in the study of biocompatibility of new prepared biocompounds with potential medical applications. The obtained multifunctional materials do not exhibit the haemolytic activity, therefore, they could be used as a promising antimicrobial agent and for anaerobic bacteria.

Comparison of the phylogenetic analysis of PFGE profiles and the characteristic of virulence genes in clinical and reptile associated Salmonella strains

BACKGROUND

Salmonella is generally considered as a human pathogen causing typhoid fever and gastrointestinal infections called salmonellosis, with S. Enteritidis and S. Typhimurium strains as the main causative agents. Salmonella enterica strains have a wide host array including humans, birds, pigs, horses, dogs, cats, reptiles, amphibians and insects. Up to 90% of reptiles are the carriers of one or more serovars of Salmonella. Extraintestinal bacterial infections associated with reptiles pose serious health threat to humans. The import of exotic species of reptiles as pet animals to Europe correlates with the emergence of Salmonella serotypes, which not found previously in European countries. The presented study is a new report about Salmonella serotypes associated with exotic reptiles in Poland. The goal of this research was to examine the zoonotic potential of Salmonella strains isolated from reptiles by comparative analysis with S. Enteritidis strains occurring in human population and causing salmonellosis.

RESULTS

The main findings of our work show that exotic reptiles are asymptomatic carriers of Salmonella serovars other than correlated with salmonellosis in humans (S. Enteritidis, S. Typhimurium). Among the isolated Salmonella strains we identified serovars that have not been reported earlier in Poland, for example belonging to subspecies diarizonae and salamae. Restriction analysis with Pulsed-field Gel Electrophoresis (PFGE), showed a great diversity among Salmonella strains isolated from reptiles. Almost all tested strains had distinct restriction patterns. While S. Enteritidis strains were quite homogeneous in term of phylogenetic relations. Most of the tested VGs were common for the two tested groups of Salmonella strains.

CONCLUSIONS

The obtained results show that Salmonella strains isolated from reptiles share most of virulence genes with the S. Enteritidis strains and exhibit a greater phylogenetic diversity than the tested S. Enteritidis population.

Complex Signaling Networks Controlling Dynamic Molecular Changes in Pseudomonas aeruginosa Biofilm

The environment exerts strong influence on microbes. Adaptation of microbes to changing conditions is a dynamic process regulated by complex networks. Pseudomonas aeruginosa is a life-threating, versatile opportunistic and multi drug resistant pathogen that provides a model to investigate adaptation mechanisms to environmental changes. The ability of P. aeruginosa to form biofilms and to modify virulence in response to environmental changes is coordinated by various mechanisms including two-component systems (TCS), and secondary messengers involved in quorum sensing (QS) and c-di-GMP networks (diguanylate cyclase systems, DGC). In this review, we focus on the role of c-di-GMP during biofilm formation. We describe TCS and QS signal cascades regulated by c-di-GMP in response to changes in the external environment. We present a complex signaling network dynamically changing during the transition of P. aeruginosa from the free-living to sessile mode of growth.

Antimicrobial Resistance and Biofilm Formation in Enterococcus spp. Isolated from Humans and Turkeys in Poland

Enterococci are a natural component of the intestinal flora of many organisms, including humans and birds. As opportunistic pathogens, they can cause fatal infections of the urinary tract and endocarditis in humans, whereas in poultry symptoms are joint disease, sepsis, and falls in the first week of life. The study covered 107 Enterococcus strains—56 isolated from humans and 51 from turkeys. Among the isolates investigated Enterococcus faecalis was detected in 80.36% of human and 80.39% of turkey samples. Enterococcus faecium was identified in 8.93% of human and 17.65% of turkey strains. The highest percentage of the strains was resistant to tetracycline as follows: 48 (85.71%) and 48 (94.12%) of human and turkey strains, respectively. Resistance to erythromycin occurred in 37.50% of the human and in 76.47% of turkey strains, otherwise 27.10% of all strains showed resistance to ciprofloxacin. Our study revealed that 25% of human and 15.69% of turkey strains were resistant to vancomycin. Multidrug resistance showed in 32.14% and 43.14% of human and turkey strains, respectively. The tetracycline resistance gene, tetM, was detected in 82.24% of all strains analyzed, whereas the tetO gene was found in 53.57% of human but only in 7.84% of turkey strains. The vancomycin resistance gene (vanA) was detected in seven Enterococcus strains (six isolated from turkeys and one from humans). The ermB gene (resistance to macrolide) was detected in 55.14% of all isolates (42.86% of human and 68.63% of turkey strains), whereas the ermA gene was detected in 17.65% of turkey but only in 3.57% of human isolates. All the strains had the ability to form biofilms. A stronger biofilm was formed after 24-hour incubation by strains isolated from turkeys, whereas after 48 hours of incubation all examined strains produced strong biofilm.

Identification of Yersinia enterocolitica isolates from humans, pigs and wild boars by MALDI TOF MS

BACKGROUND

Yersinia enterocolitica is widespread within the humans, pigs and wild boars. The low isolation rate of Y. enterocolitica from food or environmental and clinical samples may be caused by limited sensitivity of culture methods. The main goal of present study was identification of presumptive Y. enterocolitica isolates using MALDI TOF MS. The identification of isolates may be difficult due to variability of bacterial strains in terms of biochemical characteristics. This work emphasizes the necessity of use of multiple methods for zoonotic Y. enterocolitica identification.

RESULTS

Identification of Y. enterocolitica isolates was based on MALDI TOF MS, and verified by VITEK® 2 Compact and PCR. There were no discrepancies in identification of all human' and pig' isolates using MALDI TOF MS and VITEK® 2 Compact. However three isolates from wild boars were not decisively confirmed as Y. enterocolitica. MALDI TOF MS has identified the wild boar' isolates designated as 3dz, 4dz, 8dz as Y. enterocolitica with a high score of matching with the reference spectra of MALDI Biotyper. In turn, VITEK® 2 Compact identified 3dz and 8dz as Y. kristensenii, and isolate 4dz as Y. enterocolitica. The PCR for Y. enterocolitica 16S rDNA for these three isolates was negative, but the 16S rDNA sequence analysis identified these isolates as Y. kristensenii (3dz, 4dz) and Y. pekkanenii (8dz). The wild boar' isolates 3dz, 4dz and 8dz could not be classified using biotyping. The main bioserotype present within pigs and human faeces was 4/O:3. It has been shown that Y. enterocolitica 1B/O:8 can be isolated from human faeces using ITC/CIN culturing.

CONCLUSION

The results of our study indicate wild boars as a reservoir of new and atypical strains of Yersinia, for which protein and biochemical profiles are not included in the MALDI Biotyper or VITEK® 2 Compact databases. Pigs in the south-west Poland are the reservoir for pathogenic Y. enterocolitica strains. Four biochemical features included in VITEK® 2 Compact known to be common with Wauters scheme were shown to produce incompatible results, thus VITEK® 2 Compact cannot be applied in biotyping of Y. enterocolitica.

High Prevalence of Resistance to Fluoroquinolones and Tetracycline Campylobacter Spp. Isolated from Poultry in Poland

Campylobacter spp. is a major cause of foodborne diseases in humans, particularly when transmitted by the handling or consumption of undercooked poultry meat. Most Campylobacter infections are self-limiting, but antimicrobial treatment (e.g., fluoroquinolones and macrolides) is necessary in severe or prolonged cases. The indiscriminate use of these drugs, both in clinical medicine and animal production, has a major impact on public health. The aim of the present study was to identify Campylobacter strains, isolated from turkey and broilers, using both PCR and the matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) methods to reveal the accuracy of identification, as well to evaluate the antimicrobial and genetic resistance of the investigated strains. MALDI-TOF and PCR methods were used to show differences, if any, in the specificity of that test. In this study, MALDI-TOF mass spectrometry gave the same results as multiplex PCR, in all cases. The highest rate of resistance (i.e., 100% of turkey and broiler strains) was detected against ciprofloxacin, whereas 58.1% of turkey and 78.6% of broiler strains were resistant to tetracycline. Multidrug-resistant isolates were not found in the study. All ciprofloxacin-resistant strains had a mutation in the gyrA gene, at the Thr-86 position. The presence of the tetO gene was found in 71% of turkey and in 100% of broiler strains. All resistant to tetracycline strains included tetO gene. Additionally, in five turkey and three broiler strains, susceptible to tetracycline, tetO gene was present. These results indicate the high prevalence of Campylobacter strains, which are phenotypically and genetically resistant to fluoroquinolones and tetracycline.

Anti-enterococcal activities of pentacyclic triterpenes

BACKGROUND

Asiatic (AA) and ursolic (UA) acids are widely studied phytochemicals, but their antimicrobial properties are still poorly understood. Therefore our research has focused on their activity against uropathogenic Enterococcus faecalis strains.

OBJECTIVES

The aim of this research was to determine the influence of AA and UA on the growth, cell morphology, virulence factors and biofilm formation by E. faecalis strains.

MATERIAL AND METHODS

AA and UA were purchased from Sigma-Aldrich. E. faecalis strains were isolated from the urine samples of patients with urinary tract infections. The strains were checked for the presence of virulence genes using the PCR method. Their antimicrobial susceptibility was performed using the disc diffusion method. The MICs of triterpenes were determined using the broth microdilution method. The hydrophobicity of cells was established by salt aggregation test. Lipase and lecithinase activities were determined by using an agar medium containing egg yolk emulsion. DNase agar was used for the detection of DNase synthesis. Hemolytic activity was established using a sheep-blood agar. Todd-Hewitt agar medium containing gelatin was used for determination of gelatinase activity. The anti-biofilm activity of asiatic acid and ursolic acid was tested on polystyrene microtiter plates. It was examined using time-kill and biofilm assays.

RESULTS

Reduction of growth and enzyme synthesis after exposure of E. faecalis to the acids was observed. None of the acids changed the hydrophobicity of bacteria. Stronger anti-biofilm activity was observed when the bacteria were incubated with AA. Thus, reduction of both the survival and the virulence factors will make bacteria less infectious.

CONCLUSIONS

Based on the results obtained, we can assume that the triterpenes investigated should be considered natural components of a human diet rather than as antibacterial agents used on their own.

Proteomic Analysis of Outer Membrane Proteins from Salmonella Enteritidis Strains with Different Sensitivity to Human Serum

Differential analysis of outer membrane composition of S. Enteritidis strains, resistant to 50% normal human serum (NHS) was performed in order to find factors influencing the resistance to higher concentrations of NHS. Ten S. Enteritidis clinical strains, resistant to 50% NHS, all producing very long lipopolysaccharide, were subjected to the challenge of 75% NHS. Five extreme strains: two resistant and three sensitive to 75% NHS, were chosen for the further analysis of outer membrane proteins composition. Substantial differences were found in the levels of particular outer membrane proteins between resistant and sensitive strains, i.e. outer membrane protease E (PgtE) was present mainly in resistant strains, while sensitive strains possessed a high level of flagellar hook-associated protein 2 (FliD) and significantly higher levels of outer membrane protein A (OmpA).

Study of the impact of cranberry extract on the virulence factors and biofilm formation by Enterococcus faecalis strains isolated from urinary tract infections

Drinking of cranberry fruit juice and application of commercial preparations containing the cranberry extracts are recommended in the prevention and treatment of urinary tract infections (UTIs), especially in women with recurrent UTIs. Many studies focus on the activity of cranberries against uropathogenic Escherichia coli (E. coli) strains. However, the knowledge of the cranberry effect on Gram-positive Enterococcus faecalis (E. faecalis) is limited. Therefore, the aim of our study was to establish the activity of commercial concentrated cranberry extract on the growth, virulence factors and biofilm formation of E. faecalis strains isolated from urine. Minimal inhibitory concentrations (MICs) of cranberry extract were determined by the broth microdilution method. Disc diffusion method was used to determine antimicrobial susceptibility. The impact of cranberry extract on bacterial survival, hydrophobicity, synthesis of lipase, lecithinase, DNase, hemolysin, gelatinase and biofilm mass was determined. Results show that cranberry extract inhibits the growth, enzymatic activities of bacteria and limits biofilm formation. The antibacterial activities of the studied cranberry extract confirm that it could be successfully used in prevention of UTIs caused by E. faecalis.

Silver Nanoforms as a Therapeutic Agent for Killing Escherichia coli and Certain ESKAPE Pathogens

The scope of this study included the preparation of silver nanoforms with high antimicrobial efficacy, low cost, and ease of application. The term 'silver nanoforms' refers to silver located on the amorphous or crystalline titanium dioxide (TiO2). Silver nanoforms may be used as an alternative to antibiotics in killing bacteria. Pure and silver-incorporated titanium (used as a carrier) was prepared using the sol-gel-modified method. Physical and chemical properties of the samples were described, and the antibacterial activity was indicated using the following strains of bacteria: Staphylococcus aureus, Klebsiella pneumoniae (ESKAPE pathogens), and Escherichia coli. The results have shown that the antibacterial activity of silver nanoforms with amorphous TiO2 is much better than that in the samples based on anatase (crystalline TiO2). The sensitivity of the tested bacteria to silver nanoforms depends on physical and chemical properties of the nanoforms and individual characteristics of the bacteria. For the first time, significant participation of amorphous TiO2 in antibacterial compounds has been described through this study.

Selection and electrophoretic characterization of Salmonella enterica subsp. enterica biocide variants resistant to antibiotics

The proposed research outlines a serious common concern of Salmonella resistance to antimicrobials following prolonged exposure to the disinfectants (biocides). These phenotypes of bacteria could potentially result in hard to treat infections. Typical for avian sources, biocide sensitive S. enterica subsp. enterica serovars: Typhimurium, Enteritidis, Virchow and Zanzibar and their isogenic biocide-tolerant variants were studied in order to investigate bacteriostatic effect of two commercially available biocide formulations: potassium peroxymonosulfate (P) and dodecylamine based structure (triamine, D). We found that cultivating of the bacteria in the medium supplemented with a blend containing P did not influence their antibiotic susceptibility pattern. In contrast, tolerance of bacteria to D compound resulted in resistance to co-trimoxazole, cefotaxime and ciprofloxacin of which two cefotaxime and ciprofloxacin are used commonly for the treatment of invasive Salmonella infections in humans. The dependency between OMP patterns and the level of Salmonella survival in media containing the biocides was observed merely in serovar Typhimurium. In conclusion, these results suggest that Salmonella strains challenged by prolonged treatment with the disinfectants become resistant to antibiotics, however it depends on Salmonella serovar and the chemical used. This paper also highlights the loop-mediated isothermal amplification (LAMP) as a technique that offers great benefits to microbiological detecting of Salmonella species in the samples.

Application of Routine Diagnostic Procedure, VITEK 2 Compact, MALDI-TOF MS, and PCR Assays in Identification Procedure of Bacterial Strain with Ambiguous Phenotype

In diagnostic microbiology as well as in microbiological research, the identification of a microorganism is a crucial and decisive stage. A broad choice of methods is available, based on both phenotypic and molecular properties of microbes. The aim of this study was to compare the application of phenotypic and molecular tools in bacterial identification on the example of Gram-negative intestine rod with an ambiguous phenotype. Different methods of identification procedure, which based on various properties of bacteria, were applied, e.g., microscopic observation of single-bacterial cells, macroscopic observation of bacterial colonies morphology, the automated system of microorganism identification (biochemical tests), the mass spectrometry method (analysis of bacterial proteome), and genetic analysis with PCR reactions. The obtained results revealed discrepancies in the identification of the tested bacterial strain with an atypical phenotype: mucous morphology of colonies, not characteristic for either E. coli and Citrobacter spp., mass spectrometry analysis of proteome initially assigned the tested strain to Citrobacter genus (C. freundii) and biochemical profiles pointed to Escherichia coli. A decisive method in the current study was genetic analysis with PCR reactions which identified conserved genetic sequences highly specific to E. coli species in the genome of the tested strain.

Intracellular drug concentrations and transporters: measurement, modeling, and implications for the liver

Intracellular concentrations of drugs and metabolites are often important determinants of efficacy, toxicity, and drug interactions. Hepatic drug distribution can be affected by many factors, including physicochemical properties, uptake/efflux transporters, protein binding, organelle sequestration, and metabolism. This white paper highlights determinants of hepatocyte drug/metabolite concentrations and provides an update on model systems, methods, and modeling/simulation approaches used to quantitatively assess hepatocellular concentrations of molecules. The critical scientific gaps and future research directions in this field are discussed.

ITC recommendations for transporter kinetic parameter estimation and translational modeling of transport-mediated PK and DDIs in humans

This white paper provides a critical analysis of methods for estimating transporter kinetics and recommendations on proper parameter calculation in various experimental systems. Rational interpretation of transporter-knockout animal findings and application of static and dynamic physiologically based modeling approaches for prediction of human transporter-mediated pharmacokinetics and drug-drug interactions (DDIs) are presented. The objective is to provide appropriate guidance for the use of in vitro, in vivo, and modeling tools in translational transporter science.

Characterization of borderline oxacillin-resistant Staphylococcus aureus isolated from food of animal origin

In this study, the molecular characteristics of food-derived oxacillin-resistant Staphylococcus aureus were determined. Eight borderline oxacillin-resistant strains with MICs of 2 to 4 microg/ml were identified from 132 S. aureus isolates of food origin. One of the two isolates with a MIC of 4 microg/ml was methicillin-resistant determinant (mecA) gene positive, and the other six with MICs of 2 microg/ml were mecA negative. The mecA-positive isolate was classified as sequence type (ST)228, staphylococcal protein A (spa) type t041, and carried the staphylococcal cassette chromosome mec type I element. Two borderline oxacillin-resistant strains were classified as spa t008 and ST8, and the remaining five as spa t164 and ST20. The mecA-positive strain and four borderline oxacillin-resistant strains were found enterotoxigenic. The enterotoxin genes detected in these strains included selp, egc1, and sed-sej-selr. The borderline-resistant S. aureus isolates from a manually handled product, i.e., minced pork, were shown genetically related to strains associated with human infections. This suggests that humans can be considered as a source of contamination of this food with oxacillin-resistant S. aureus strains. The genotypes of the investigated milk borderline-resistant isolates were shown to occur not only in cows, but also in humans. Since manual handling is reduced in raw milk production, a human origin of S. aureus seems unlikely. Because knowledge of the genotypes of animal staphylococci is limited, more research is needed to address the question of the origin of antibiotic-resistant S. aureus strains in food.

[Infectivityand resistance to antibiotics of non-fermentative rods isolated from patients hospitalised in pediatric center of Lower Silesia in Wrocław in the years 2000-2006]

The aim of this study was to evaluate the frequency of isolation and antimicrobial resistance testing of non-fermentative rods isolated from clinical specimens from patients hospitalized in Korczak Pediatric Center of Lower Silesia in Wrocław. The susceptibility of bacteria to selected antibiotics was determined. The commonest pathogens were Pseudomonas rods (81.8%) isolated from respiratory system and urine of patients hospitalized in unit intensive care. Variety of resistance patterns were detected in bacteria. ESBL were detected the most of S. maltophilia. Strains of Pseudomonas and Acinetobacter resistant to carbapenems were detected with a frequency of 5.5% and 35.9%.

[Bactericidal action of human serum against Pseudomonas aeruginosa strains with hydrophilic or hydrophobic cell surface]

Pseudomonas aeruginosa strains are the prominent nosocomial pathogens, especially dangerous for patients hospitalized in intensive care units. The cell surface hydrophobicity of P. aeruginosa rods and resistance to the bactericidal action of serum are considered as important factors of their virulence. The aim of the study was to evaluate the susceptibility of hydrophilic and hydrophobic P aeruginosa strains to the bactericidal effect of human serum. These strains were isolated from bronchioloalveolar lavage of children with hospital-acquired pneumonia. The BATH test was used to evaluate the hydrophobic properties. Among tested P aeruginosa strains seven had strong hydrophobic properties and eight strains were hydrophilic. The data showed that hydrophobic strains were more frequently serum-resistant than rods with hydrophilic cell surface.

Superantigen types in Staphylococcus aureus isolated from patients with cystic fibrosis

The screening of 17 SAg genes of S. aureus isolated from the sputum of cystic fibrosis (CF) patients revealed that among 47 genetically different strains, 39 (83 %) carried SAg genes. Superantigens forming enterotoxin gene cluster were detected in 20 strains. The 2nd most common superantigen type was selk detected in 13 strains. In 9 strains, selk occurred together with the sea gene. Out of 74 strains recovered from nasal carriers, 56 (75 %) were found to carry SAg genes, 38 carried egc genes, while selk was detected in 5 strains. The predominant SAg types in both investigated S. aureus populations were egc and selk/sea, but selk gene frequency was significantly higher in the CF-derived strains.

[Infectivity and resistance to antibiotics of bacterial strains isolated from patients hospitalised in intensive care units]

The aim of this study was to evaluate the frequency of isolation and antimicrobial resistance testing of bacterial strains isolated from clinical specimens from patients hospitalized in three Intensive Care Units in Wrocław. The susceptibility of bacteria (107 strains) to selected antibiotics was determined. The results clearly show that non-fermentative rods were identified as the main agents causing pneumonia (58% of isolates). The second commonest pathogens were Gram-positive cocci (29%). The P. aeruginosa and E. cloacae strains were resistant to ampicillin, amoxicillin/clavulanate, cefuroxime and cefotaxime. All isolates of A. baumanii were susceptible only to imipenem. The rods of K. pneumoniae and E. coli were resistant to ampicillin, about 55% strains of both bacteria were sensitive to other antibiotics, except piperacillin/tazobactam, imipenem and ciprofloxacin. About 90% of methicillin resistant S. epidermidis strains were resistant to all antibiotics, except vancomycin (100% isolates were sensitive). ESBL were detected among E. cloace, K. pneumoniae and E. coli. We found P. aeruginosa rods producing MBL.

The profiles of enterotoxin genes in Staphylococcus aureus from nasal carriers

AIMS

To evaluate the occurrence of enterotoxin genes in Staphylococcus aureus recovered from nasal carriers.

METHODS AND RESULTS

Eighty S. aureus strains were tested for the presence of 17 new enterotoxin genes using multiplex-PCR. Sixty-one isolates were found to carry enterotoxin genes. The majority of the enterotoxigenic isolates carried enterotoxin gene cluster (egc) genes, namely seg, sei, sem, sen and seo. The egc type containing the seu gene was found in 19 of the 47 isolates with egc-like genes. Interestingly, no seu-containing egc coexisted with sec and sel, as was the case for a considerable portion of the isolates carrying a seu-negative egc. The tst gene was detected in two isolates carrying sec and sel only and in eight isolates carrying seu, but not in the isolates containing the seu-negative egc type.

CONCLUSIONS

The genes forming an egc were found to be predominant in S. aureus from nasal carriers. The coexistence of a seu-positive egc with tst in contrast to an egc lacking the seu gene apparently is not associated with the presence of tst and can reflect a difference between these gene groupings.

SIGNIFICANCE AND IMPACT OF THE STUDY

The egc types carried by the analysed isolates seem to have an influence on the distribution of other genes located on staphylococcal pathogenicity islands, which may modulate the repertoire of virulence factors carried by a single S. aureus strain.

Distribution of newly described enterotoxin-like genes in Staphylococcus aureus from food

Extensive analysis of the Staphylococcus aureus genome has allowed the identification of new genes encoding enterotoxin-like superantigens (SEls). Some of these are thought to be involved in staphylococcal food poisoning, while others do not elicit any emetic effect. The potential impact of these members of the enterotoxin-like family on the human organism seems to rely mainly on their superantigenic activity. In this paper the distribution of the genes coding for enterotoxin-like superantigens in S. aureus isolated from food was studied. Fifty isolates of S. aureus were examined and 27 were shown to be enterotoxigenic. Only 9 of the 27 strains carried genes encoding enterotoxins SEA-SEE. In 18 SEA-SEE-negative strains the presence of newly described enterotoxin genes was detected. All SEA-SEE-positive strains simultaneously carried genes of new SEls. We show that the gene encoding SElH (staphylococcal enterotoxin-like enterotoxin H) was the most frequently detected (n=14), while genes encoding SElI together with SElG accompanied by the other genes of the egc locus were detected in three strains. We also detected the presence of three less investigated genes: sep, sel, and sek. These genes were present in eight, two, and one isolate, respectively. In one strain, sep was accompanied by genes of other SEls, while in the remaining seven it was the only enterotoxin-like gene detected. The high prevalence of newly discovered enterotoxin genes, including the genes encoding emetic toxins, was demonstrated in food-derived strains. This supports the need for additional work on its role in food poisoning and, alternatively, to monitor its presence in S. aureus isolated from food. Our results suggest that yet unknown genetic elements encoding enterotoxin genes may exist.

[Evaluation of sensitivity to antibiotics of microorganisms isolated from children with urinary tract infections]

The incidence of etiological factors of urinary tract infections in children and in vitro susceptibility of these strains to antibiotics were evaluated. 1082 strains isolated from 905 samples of urine of children hospitalized in the period of 01.01-31.12.2001 were tested. Among the isolated microorganisms, the most common group was the Enterobacteriaceae family (57.4%) and also very often Gram-positive cocci were isolated (34.2%). The most frequent causative agents of UTI (Escherichia coli and Enterococcus faecalis) were generally sensitive to all used antibiotics, but E. coli rods were resistant to ampicillin. In addition, 23.4% of E. coli were the ESBL-producing strains.

Inhibition of the contraction of the ductus arteriosus to oxygen by 1-aminobenzotriazole, a mechanism-based inactivator of cytochrome P450

1. We have proposed that contractile tension of the ductus arteriosus is sustained by a cytochrome P450-linked mechanism acting as a limiting step in the synthesis of endothelin-1 (ET-1). In the present study, we have used the isolated ductus from near-term foetal lambs and guinea-pigs to investigate the effect on both muscle tone and ET-1 formation of 1-aminobenzotriazole (ABT), a suicide substrate for mono-oxygenase reactions. 2. ABT relaxed the lamb ductus at rest (2.5% O2) and during the oxygen contraction (15 to 95% O2). The effect was seen at 40 microM, and at 0.8 mM active tone was almost completely abolished. ABT (1 mM) also reversed the oxygen contraction in the guinea-pig ductus. 3. In the lamb ductus, the ABT response was not affected by removal of the endothelium or by treatment with 2.8 microM indomethacin (at 2.5% O2) and the ensuing contraction. 4. At both low and high concentration, ABT relaxed marginally, or not at all, the potassium-contracted (55 mM) ductus from either species. 5. ET-1 release from either the intact or endothelium-denuded lamb ductus tended to decrease in the presence of ABT (1 mM), whilst during the same treatment cyclic GMP content of the tissue remained unchanged. 6. We conclude that ABT relaxation is due to suppression of a contractile mechanism and not to activation of prostaglandin- and NO-mediated relaxing mechanisms. This contractile mechanism has a cytochrome P450-based mono-oxygenase reaction as a key component.

Cross-reactivity of thirteen monoclonal antibodies with ten vaccinia cDNA expressed rat, mouse and human cytochrome P450s

Twelve monoclonal antibodies (MAbs) to rat cytochrome P450s and one MAb to a scup (fish) P450 have been isolated, characterized, and are currently in common use. Expression of cDNAs for different P450s from a vaccinia vector offers a rapid and simple way toward the production of individual P450s. The thirteen MAbs were examined for their cross-reactivity with ten cDNA expressed human, rat, and mouse P450s. Three MAbs to rat 1A1 and fish 1A1 cross-reacted with cDNA expressed mouse 1A1. One of the latter MAbs, 1-7-1 but none of the others cross-reacted with mouse 1A2. Surprisingly, the fish MAb to 1A1 also cross-reacted with human 2E1. Two MAbs to rat 2B1/2B2 cross-reacted with rat 2A1. An MAb to rat 2C11 cross-reacted with human 2C9. Two MAbs to rat 2E1 cross-reacted with human 2E1. Finally, two MAbs to rat 3A1 cross-reacted strongly with human 3A4. These studies open the door to constructing a library of MAbs with defined binding activity to the P450s of human and other species.

Steroid hormone hydroxylase specificities of eleven cDNA-expressed human cytochrome P450s

Steroid hydroxylation specificities were determined for 11 forms of human cytochrome P450, representing four gene families and eight subfamilies, that were synthesized in human hepatoma Hep G2 cells by means of cDNA-directed expression using vaccinia virus. Microsomes isolated from the P450-expressing Hep G2 cells were isolated and then assayed for their regioselectivity of hydroxylation toward testosterone, androstenedione, and progesterone. Four of the eleven P450s exhibited high steroid hydroxylase activity (150-900 pmol hydroxysteroid/min/mg Hep G2 microsomal protein), one was moderately active (30-50 pmol/min/mg) and six were inactive. In contrast, 10 of the P450s effectively catalyzed O-deethylation of 7-ethoxycoumarin, a model drug substrate, while only one (P450 2A6) catalyzed significant coumarin 7-hydroxylation. Human P450 4B1, which is expressed in lung but not liver, catalyzed the 6 beta-hydroxylation of all three steroids at similar rates and with only minor formation of other hydroxylated products. Three members of human P450 family 3A, which are expressed in liver and other tissues, also catalyzed steroid 6 beta-hydroxylation as their major activity but, additionally, formed several minor products that include 2 beta-hydroxy and 15 beta-hydroxy derivatives in the case of testosterone. These patterns are similar to those exhibited by rat family 3A P450s. Although several rodent P450s belonging to subfamilies 2A, 2B, 2C, 2D are active steroid hydroxylases, four of five human P450s belonging to these subfamilies exhibited very low activity or were inactive, as were the human 1A and 2E P450s examined in the present study. These studies demonstrate that individual human cytochrome P450 enzymes can hydroxylate endogenous steroid hormones with a high degree of stereospecificity and regioselectivity, and that some, but not all of the human cytochromes exhibit metabolite profiles similar to their rodent counterparts.

Metabolic activation of 4-ipomeanol by complementary DNA-expressed human cytochromes P-450: evidence for species-specific metabolism

4-Ipomeanol is a pulmonary toxin in cattle and rodents that is metabolically activated by cytochromes P-450 (P-450s). P-450-mediated activation of 4-ipomeanol to DNA binding metabolites was evaluated using a vaccinia virus complementary DNA expression system and an in situ DNA-binding assay. Twelve human P-450s and two rodent P-450s were expressed in human hepatoma Hep G2 cells and examined for their abilities to metabolically activate this toxin. Three forms, designated CYP1A2, CYP3A3, and CYP3A4, were able to catalyze significant production of DNA-bound metabolites of 20-, 8-, and 5-fold, respectively, above binding catalyzed by Hep G2 cells infected with wild-type vaccinia virus. These enzymes, with highest activities, are not known to be expressed in human or rodent lung. CYP2F1 and CYP4B1, two enzymes that are expressed in lung, display only modest 3- and 2-fold respective increased abilities to metabolically activate 4-ipomeanol. Two human forms were inactive and seven other human forms showed activities ranging from 0.5- to 2-fold above control level. Surprisingly, rabbit complementary DNA-expressed CYP4B1 was the most active enzyme (180-fold above control) among all P-450s tested in producing DNA-binding metabolites from this mycotoxin. These studies demonstrate a species difference in 4-ipomeanol metabolism and suggest caution when attempting to extrapolate rodent data to humans.

Oxidative modification by low levels of HOOH can transform myoglobin to an oxidase

It is generally thought that the oxidative modification of hemoproteins leads to their inactivation. In the current study, however, a transiently activated form of myoglobin was shown to be formed when the prosthetic heme group became covalently bound to the polypeptide during the reaction of myoglobin with low levels of HOOH. In the presence of an enzymatic metmyoglobin reducing system containing diaphorase and methylene blue with excess NADH, this HOOH-altered myoglobin catalyzed NADH oxidation and oxygen consumption; the overall stoichiometry indicated a two-electron reduction of oxygen to HOOH. This reaction was not catalyzed by iron released from heme, as desferrioxamine had no effect on the activity. Stoichiometric amounts of HOOH were sufficient to produce the activated oxidase state of myoglobin, whereas larger amounts of HOOH lead to heme destruction, iron release, and inactivation of the oxidase activity. The alteration of myoglobin to an enzyme that can form toxic oxygen metabolites may have pathological importance, especially in myocardial injury caused by ischemia and reperfusion, where myoglobin is present in large amounts and HOOH is formed. Furthermore, the oxidase form may be involved in the mechanism of destruction of the heme seen with oxidative treatment of myoglobin.

Sequence requirements for cytochromes P450IIA1 and P450IIA2 catalytic activity: evidence for both specific and non-specific substrate binding interactions through use of chimeric cDNAs and cDNA expression

Cytochrome P450s IIA1 and IIA2, encoded by the CYP2A1 and CYP2A2 genes, display 88% amino acid sequence similarities. The dissimilarities of sequence between these two enzymes are primarily localized within four discrete regions of the polypeptides that are separated by regions of absolute sequence identity. IIA1 specifically hydroxylates the prototype substrate testosterone at the 7 alpha and 6 alpha position with a predominance of 7 alpha metabolite. IIA2, on the other hand, hydroxylates this steroid at eight positions on the molecule, with one of the most abundant metabolites being 15 alpha-hydroxytestosterone. To determine those amino acids responsible for the difference in testosterone hydroxylation specificities, chimeras were constructed between IIA1 and IIA2 cDNAs and expressed in cell culture using vaccinia-virus-mediated cDNA expression. Chimeras, in which the first 355 amino acids correspond to a single enzyme, maintain the specificity associated with that enzyme. Of six chimeras which have substitutions between amino acids 161 and 276, two are inactive and the remaining four give similar metabolite profiles, in which both 7 alpha and 15 alpha hydroxylation specificities have been lost. Two of these four chimeras are diametric apposites, suggesting that modification of either the N-terminal or central regions of the enzymes results in conformational changes that prevent the specific binding interactions responsible for the narrow regioselectivity associated with IIA1 and 15 alpha-hydroxytestosterone formation associated with IIA2.

Estradiol metabolism by complementary deoxyribonucleic acid-expressed human cytochrome P450s

Twelve forms of human cytochrome P450 were synthesized in human hepatoma Hep G2 cells by means of cDNA-directed expression using vaccinia virus. The cDNA-expressed enzymes were tested for their ability to oxidize estradiol. Incubation of [14C]estradiol with cell lysates containing P450 IA2 resulted in the production of 2-hydroxy and 4-hydroxy metabolites with substrate turnovers of 2.74 and 0.27 min-1, respectively. P450s IIIA3 and IIIA4 yielded the same metabolites at about one third the rate of P450 IA2. Low levels of estradiol hydroxylation were also catalyzed by P450s IIC9, IIIA5, and IVB1. Six other P450 forms yielded no detectable metabolism. The roles of P450s IA2, IIA3, and IIIA4 were further established by immunoinhibition using antirat P450 antibodies. Antibody that specifically binds to P450 IIIA3 and IIIA4 inhibited 60-70% of estradiol hydroxylation, and antibody against P450 IA2 inhibited 20-40% of the estradiol hydroxylase activity in microsomes from two human liver specimens, suggesting that these enzymes constitute the major forms catalyzing estradiol oxidation in human liver. Immunoinhibition results also suggest that 2-hydroxy- and/or 4-hydroxycatechol estrogens are further metabolized to other yet uncharacterized metabolites by P450s IIIA3 and IIIA4.

cDNA-directed expression of rat P450s IIA1 and IIA2. Catalytic activities toward steroids and xenobiotics and comparison with the enzymes purified from liver

Cytochromes P-450IIA1 and IIA2 are steroid hydroxylases that are expressed in rat liver. The cDNAs for these enzymes were recently sequenced and compared. To study and compare the catalytic activities of IIA1 and IIA2, their cDNAs were inserted into a vaccinia virus expression vector and expressed in human hepatoma Hep G2 cells. IIA2 was able to efficiently catalyze ethoxycoumarin O-deethylation and propoxycoumarin O-depropylation, while IIA1 was inactive toward these substrates. Neither enzyme could catalyze ethoxy- and pentoxyresorufin dealkylation reactions. Both cDNA-expressed IIA1 and IIA2 metabolize testosterone and these activities were quantitatively and qualitatively similar to those obtained with the purified enzymes. IIA1 produced 7 alpha-hydroxy, 6 alpha-hydroxy, and delta 6-testosterone at ratios of 9:0.5:0.5 while IIA2 formed 15 alpha-hydroxytestosterone, an unknown metabolite and four minor metabolites. Progesterone metabolism was also studied. IIA1 yielded a 9.5:0.5 ratio of 7 alpha-hydroxy and 6 alpha-hydroxyprogesterone, while IIA2 produced at least six metabolites. These studies establish the conditions and verify the reliability and accuracy of the vaccinia virus expression system for studies on the enzymology of IIA1 and IIA2.

The use of Brauman's least squares approach for the quantification of deuterated chlorophenols

The least squares method for the solution of ion overlap problems in quantitative mass spectrometry first introduced by Brauman was used to quantify isotopic mixtures of chlorophenol derivatives. The samples analyzed consisted of the chlorophenols resulting from the cytochrome P-450 mediated oxidation of isotopic mixtures of chlorobenzenes, and were analyzed on a VG-7070 double-focusing mass spectrometer. The application of this method is described and its advantages are highlighted. In some instances the use of the least squares methods resulted in smaller standard deviations of the means of replicate analyses. Significant features of the technique include its simplicity of use, the universality of its application to all cases of ion overlap and its inherent ability to detect erroneous data, e.g. that due to the presence of impurities or mass spectral parameter variation.

Sequence requirements for cytochrome P-450IIB1 catalytic activity. Alteration of the stereospecificity and regioselectivity of steroid hydroxylation by a simultaneous change of two hydrophobic amino acid residues to phenylalanine

The phenobarbital-inducible P-450 forms IIB1 and IIB2 are identical in sequence except for 14 amino acid differences within the carboxyl-terminal half of the molecule. IIB1 has about a 5-10-fold higher turnover number for most monooxygenase substrates examined although the substrate specificities of both enzymes are virtually identical. Both P-450s oxygenate testosterone to yield the 16 alpha-hydroxy, 16 beta-hydroxy, 17-keto, and 16 beta-hydroxy, 17-keto metabolites as major products. A variant IIB2 cDNA, isolated from an uninduced rat liver lambda gt11 library, and when expressed in Hep G2 cells using a vaccinia virus vector, was found to code for a protein that produced the 16 alpha-hydroxy and 17-keto metabolites of testosterone but no 16 beta-hydroxylated products. Although the published sequences of IIB1 and IIB2 are identical within the N-terminal halves of the proteins, sequence analysis of the variant cDNA revealed two amino acid substitutions in this region; Leu58----Phe and I1e114----Phe. When these two amino acid changes were incorporated into IIB1, via construction of a chimeric cDNA, the resultant expressed enzyme did not catalyze the 16 beta-hydroxylation of testosterone or androstenedione. Formation of the 16 alpha-hydroxy and 17-keto metabolites, however, was only slightly reduced compared with the parent IIB1. A IIB1 protein that possessed only the I1e114----Phe replacement catalyzed the production of all four testosterone metabolites with only slightly different product ratios compared with the parent enzyme. The substrate specificity of a IIB1 variant containing only the Leu58----Phe replacement could not be determined, since that protein did not accumulate in cells infected with the corresponding recombinant vaccinia virus. These data suggest that two distinct amino acid residues located within the amino-terminal fourth of IIB1 and IIB2 can affect substrate orientation at the active site.

cDNA-directed expression of rat testosterone 7 alpha-hydroxylase using the modified vaccinia virus, T7-RNA-polymerase system and evidence for 6 alpha-hydroxylation and delta 6-testosterone formation

The modified vaccinia virus, T7-RNA-polymerase cDNA-expression system was used to express rat cytochrome P-450a. Various parameters such as host-cell type and density, and duration of infection were tested to optimize the level of expression of cytochrome P-450a enzyme activity. Cytochrome P-450a expressed from the cDNA sequence was exclusively incorporated into the membrane-containing portions of the cell lysates, as expected from its normal association in the liver endoplasmic reticulum. The enzyme displayed a carbon-monoxide-reduced-cytochrome-P-450a difference spectrum with a Soret maximum of 450 nm. Activity measurements revealed that cytochrome P-450a produced three metabolites of testosterone; 7 alpha-hydroxytestosterone and 6 alpha-hydroxytestosterone and delta 6-testosterone at a ratio of about 38:1:1. Under the appropriate conditions, the vaccinia-virus, T7-RNA-polymerase system produces high levels of a single form of cytochrome P-450 in cells that are virtually devoid of endogenous cytochrome P-450. Analysis of the cytochrome P-450 in its natural membrane-bound state, as opposed to artificial-lipid reconstitution studies of purified enzymes, allows accurate and confident measurements of substrate specificities.