Showing papers in "Polish Journal of Microbiology in 2008"

Characterization of glycopeptides, aminoglycosides and macrolide resistance among Enterococcus faecalis and Enterococcus faecium isolates from hospitals in Tehran.

Abstract: The prevalence of glycopeptides, aminoglycosides and erythromycin resistance among Enterococcus faecalis and Enterococcus faecium was investigated. The susceptibility of 326 enterococcal hospital isolates to amikacin, kanamycin, netilmicin and tobramycin were determined using disk diffusion method. The minimum inhibitory concentration (MIC) of vancomycin, teicoplanin, gentamicin, streptomycin, and erythromycin were determined by microbroth dilution method. The genes encoding aminoglycoside modifying enzymes described as AMEs genes, erythromycin-resistant methylase (erm) and vancomycin-resistant were targeted by multiplex-PCR reaction. High level resistance (HLR) to gentamicin and streptomycin among enterococci isolates were 52% and 72% respectively. The most prevalent of AMEs genes were aac (6')-Ie aph (2") (63%) followed by aph (3')-IIIa (37%). The erythromycin resistance was 45% and 41% of isolates were positive for ermB gene. The ermA gene was found in 5% of isolates whereas the ermC gene was not detected in any isolates. The prevalence of vancomycin resistant enterococci (VRE) was 12% consisting of E. faecalis (6%) and E. faecium (22%) and all of them were VanA Phenotype. The results demonstrated that AMEs, erm and van genes are common in enterococci isolated in Tehran. Furthermore our results show an increase in the rate of vancomycin resistance among enterococci isolates in Iran.

Low distribution of integrons among multidrug resistant E. coli strains isolated from children with community-acquired urinary tract infections in Shiraz, Iran.

Abstract: Although integrons by themselves are not mobile, due to their presence in plasmids and transposons, they can be transferred horizontally. For these reasons integrons are a major mechanism for the spread and maintenance of multidrug resistance (MDR). This study describes the distribution of integron gene cassette classes in a collection of uropathogenic Escherichia coli (UPEC) isolated from children with community acquired urinary tract infection in Jahrom, Iran. E. coli strains isolated from urine samples were tested for susceptibility to 14 different antibiotics using the disk diffusion method and for integron classes by RFLP-PCR. Totally 96 strains of E. coli were isolated from urine samples. High prevalence of resistance to ampicillin (80.2%), co-trimoxazole ((76%) and tetracycline (70.8%) was seen among the UPEC isolates. All isolates were 100% sensitive to imipenem. Sixteen strains (16.6%) had the evidence ofintegron sequences with the prevalence of 6.25% (n = 6) and 10.41% (n = 10) for intI1 and intI2, respectively. No intI3 was detected in the isolates. The presence of integrons was significantly associated with resistance to certain antibiotics including gentamicin and ampicillin. Considering the MDR patterns and the low prevalence ofintegrons among the E. coli strains under the study, we suggest that the antibiotic resistance cassettes in these strains presumably are mostly carried on the other transposable elements rather than integrons.

Statistical optimization of alpha-amylase production by Streptomyces erumpens MTCC 7317 cells in calcium alginate beads using response surface methodology

Abstract: " -Amylase has a wide range of applications in starch industries, i.e. baking, brewing, distillery, etc. The "-amylase production from Streptomyces erumpens MTCC 7317 immobilized cells was compared with that of free cells. The immobilized cells of S. erumpens in calcium alginate beads were more effective for production of "-amylase (12.2% more yield) than free cells. Response surface methodology (RSM) was used to evaluate the effect of main variables, i.e. incubation period, pH and temperature on enzyme production with immobilized cells. A full factorial Central Composite Design (CCD) was applied to study these main factors that affected "-amylase production. The experimental results showed that the optimum incubation period, pH and temperature were 36 h, 6.0 and 50∞C, respectively for immobilized cells. Repeated batch fermentation of immobilized cells in shake flasks carried out in starch-beef extract medium showed that S. erumpens cells were physiologically active on the support even after four cycles of fermentation.

Isolation and characterization of extracellular bioflocculants produced by bacteria isolated from Qatari ecosystems.

Abstract: Compared with conventional synthetic flocculants, bioflocculants has special advantages such as safety, strong effect, biodegradable and harmlessness to humans and the environment, so they may potentially be applied in drinking and wastewater treatment, downstream processing, and fermentation processes. To utilize bioflocculants widely in industrial fields, it is desirable to find various microorganisms with high bioflocculant-producing ability and improve the flocculating efficiency of the bioflocculant. In the present study, screening of new flocculant-producing microorganisms was carried out using samples collected from different Qatari ecosystems. The flocculating activity of the novel bioflocculants produced by isolated microorganisms was investigated. A total of 5 g/l Kaolin suspension was used to measure the flocculating activity. Isolated bioflocculant-producing bacteria were identified by 16S rDNA analysis, using PCR with universal primers. Comparative analysis of the 16S rDNA sequence (approximately 550 bp) in the GenBank database revealed that these bacteria are related to the genus Bacillus. FT-IR spectrometry analysis of the extracted bioflocculants indicated the presence of carboxyl, hydroxyl and amino groups preferred for the flocculation process. Influences of pH and bioflocculant dosage on the flocculation were also examined. The maximum flocculating rates were observed at pH 7, 7 and 3 of the bioflocculants derived from strains QUST2, QUST6 and QUST9, respectively. However, 20.0 mg/l was the dose that gave the highest flocculating rate with all examined bioflocculants. The elemental analysis of examined bioflocculants revealed the mass proportion of C, H, N and S. Carbon and nitrogen contents of examined bioflocculants were in the range of 42-48% and 11-12%, respectively.

Anti-phagocytic activity of Helicobacter pylori lipopolysaccharide (LPS)--possible modulation of the innate immune response to these bacteria.

Abstract: The Helicobacter pylori infections are followed by an infiltration of the gastric mucosa by neutrophils and macrophages. Accumulation of phagocytes enables them to interact with H. pylori, but a great number of infected subjects cannot eradicate these bacteria. The H. pylori inhibits its own uptake by blocking the function of phagocytes. The anti-phagocytic mechanism depends on bacterial surface structures and the presence of the cag pathogenicity island (PAI). The role of H. pylori lipopolysaccharide (LPS), during phagocytosis of these bacteria is not clear. LPS may mediate direct bacteria/phagocyte interactions and it may also regulate antibacterial activity of the phagocytes. In this study we investigated the influence of H. pylori LPS on phagocytosis of these bacteria. The H. pylori LPS inhibited an ingestion of these microbes by human peripheral blood granulocytes. This was correlated with a diminished ability of phagocytes to reduce MTT-tetrazolium salt. The anti-phagocytic effect of H. pylori LPS was reduced by recombinant lipopolysaccharide binding protein (rLBP). It is possible that in vivo H. pylori LPS may diminish elimination of these bacteria from the gastric mucosa promoting an infection persistence. However, LBP may modulate the uptake of H. pylori due to neutralization of anti-phagocytic effect of its LPS.

Influence of microencapsulation and spray drying on the viability of Lactobacillus and Bifidobacterium strains.

Abstract: Improved production methods of starter cultures, which constitute the most important element of probiotic preparations, were investigated. The aim of the presented research was to analyse changes in the viability of Lactobacillus. acidophilus and Bifidobacterium bifidum after stabilization (spray drying, liophilization, fluidization drying) and storage in refrigerated conditions for 4 months. The highest numbers of live cells, up to the fourth month of storage in refrigerated conditions, of the order of 10(7) cfu/g preparation were recorded for the B. bifidum DSM 20239 bacteria in which the N-Tack starch for spray drying was applied. Fluidization drying of encapsulated bacteria allowed obtaining a preparation of the comparable number of live bacterial cells up to the fourth month of storage with those encapsulated bacteria, which were subjected to freeze-drying but the former process was much shorter. The highest survivability of the encapsulated L. acidophilus DSM 20079 and B. bifidum DSM 20239 cells subjected to freeze-drying was obtained using skimmed milk as the cryoprotective substance. Stabilization of bacteria by microencapsulation can give a product easy to store and apply to produce dried food composition.

A comparative evaluation of PCR ribotyping and ERIC PCR for determining the diversity of clinical Pseudomonas aeruginosa isolates.

Abstract: Two typing methods were evaluated, utilizing 62 clinical strains of Pseudomonas aeruginosa, to assess their usefulness as tools to study the bacterial diversity within this complex group. Genetic diversity was determined by PCR ribotyping and enterobacterial repetitive intergenic consensus (ERIC) PCR. By these methods, 9 and 36 genotypes were found, respectively. The result showed that ERIC PCR analysis is a more discriminatory method than PCR ribotyping analysis and traditional serotyping scheme. We suggest that maximum discrimination can be achievied by a combination of these methods.

Characterisation of actinomycetes isolated from ancient stone and their potential for deterioration.

Abstract: Actinomycetes have been isolated from decayed and sound stone samples taken from a tomb site at Tell Basta, Zagazig City, Egypt. A total of 160 isolates have been characterised. The numbers and distribution of actinomycetes were studied during different seasons; during the winter months (18n20∞C), actinomycete numbers ranged from 10 3 to 10 4 cfu/g; in the summer (28n38∞C) lower counts were recorded. The actinomycete isolates were assigned to 4 different taxonomic groups: 54% belonged to the Streptomyces group, 26% to the Nocardia group, 14% showed the characteristics of the Micromonospora group, while the rest of the isolates analyzed (6%) were assigned to the sporangiate-type group of actinomycetes. The ability of the isolates to produce pigments as well as tolerance to high salinity were determined. It was shown that about 88% of the strains studied had the ability to produce extracellular pigments. Only 25% of the studied isolates showed tolerance to high salinity. The significance of actinomycetes to attack and degrade building stone was shown in laboratory experiments: actinomycetes recovered both from sound and decayed stones were capable of damaging stone under laboratory conditions as an up to 4% weight loss was recorded for some isolates.

Xylanase production by a newly isolated Aspergillus niger SS7 in submerged culture.

Abstract: Xylanase production by a newly isolated Aspergillus niger SS7 was studied in submerged culture. The optimum initial pH for xylanase production was found to be 7.0. Different agricultural and industrial wastes were evaluated for their ability to induce xylanase production by this isolate. The best xylanase production (293.82 IU/ml) was recorded at 3% (w/v) corn cob hulls after 120 h of incubation. The Aspergillus niger SS7 isolate grown in a simple medium, proved to be a promising microorganism for xylanase production.

Study on Bioactive Compounds from Streptomyces sp. ANU 6277

Abstract: An attempt was made to study the bioactive compounds from a terrestrial Streptomyces sp. ANU 6277 isolated from laterite soil. Four active fractions were recovered from the solvent extracts obtained from the culture broth of five day-old strain. Three bioactive compounds were purified and identified as 3-phenylpropionic acid, anthracene-9,10-quinone and 8-hydroxyquinoline. The components of the partially purified fourth active fraction were analyzed by gas chromatography-mass spectrometry and identified as benzyl alcohol, phenylethyl alcohol and 2H-1, 4-benzoxazin-3 (4H)-one. Four active fractions were screened for antimicrobial activity against Gram-positive and Gram-negative bacteria, and fungi including phytopathogenic, toxigenic and dermatophytic genera. Among these metabolites, 8-hydroxyquinoline exhibited strong antibacterial and antifungal activity as compared to 3-phenylpropionic acid and anthracene-9,10-quinone.

The decline of antibiotic era--new approaches for antibacterial drug discovery.

Abstract: Infectious diseases still remain the main cause of human premature deaths; especially in developing countries. The emergence and spread of pathogenic bacteria resistant to many antibiotics (multidrug-resistant strains) have created the need for the development of novel therapeutic agents. Only two new classes of antibiotics of novel mechanisms of action (linezolid and daptomycin) have been introduced into the market during the last three decades. The recent progress in molecular biology and bacterial genome analysis has had an enormous impact on antibacterial drug research. This review presents new achievements in searching a new bacterial essential genes, a potential targets for antibacterial drugs. Application of metagenomics strategy is also shown. Some recent technologies aimed at development of anti-pathogenic drugs such as inhibitors of quorum sensing process or histidine kinases are also discussed. Extensive research efforts have provided many details concerning structure of bacterial proteins playing an important role in pathogenesis such as adherence proteins or toxins, what allowed searching for antitoxin drugs or drugs interfering with bacterial adhesion. As an example, the review focuses on anthrax therapies under development. Additionally, the article presents the progress in phage therapy; using bacteriophages or their products such as lysins in antibacterial therapy.

Isolation and characterization of a Cr(VI) reducing Bacillus firmus strain from industrial effluents.

Abstract: A chromium resistant bacterial strain KUCr1 exhibiting potential Cr(VI) reducing ability under in vitro aerobic condition is reported. The bacterial strain showed varied degree of resistance to different heavy metals. The MIC of chromium to this strain was found to be 950 mM under aerobic culture condition in complex medium. The factors affecting Cr(VI) reduction by this strain under culture condition were evaluated. Maximal Cr(VI) reduction was observed at the pH 8 to 10 and at a temperature of 35∞C. Higher concentration of Cr(VI) slowed down the reduction, eventually all the metal could be reduced with longer incubation time. Different toxic metals showed differential effect on reduction. Cadmium and zinc were found to inhibit reduction. Cr(VI) reduction and bioremediation were found to be related to the growth supportive condition in terms of carbon, phosphorous and nitrogen supply in wastewater fed with tannery effluent indicating cell mass dependency of Cr(VI) reduction. Through biochemical characterization and 16S rDNA sequence analysis, the strain KUCr1, as the name given to it, was identified as a strain of Bacillus firmus.

Evaluation of three methods for DNA fingerprinting of Corynebacterium pseudotuberculosis strains isolated from goats in Poland.

Abstract: Phenotypic approaches based on metabolic and biological characteristics of Corynebacterium pseudotuberculosis have been limited due to insufficient discrimination between closely related isolates. In this paper we present performance and convenience of three molecular typing methods: BOX-PCR, random amplification of polymorphic DNA (RAPD) and amplification of DNA fragments surrounding rare restriction site (ADSRRS-fingerprinting) in genome analysis of these bacteria. Among examined 61 strains there were distinguished four, eight and 10 different genotypes by BOX-PCR, RAPD and ADSRRS-fingerprinting, respectively. The value of discrimination index was the lowest for BOX-PCR (D = 0.265), much bigger for RAPD (D = 0.539) and the highest for ADSRRS-fingerprinting (D = 0.604). The good discriminatory ability and reproducibility of RAPD and ADSRRS-fingerprinting indicates that those techniques may be particularly applied for epidemiological studies of C. pseudotuberculosis isolates. We found that ADSRRS-fingerprinting is a rapid method offering good discrimination power, excellent reproducibility and may be applied for epidemiological studies of intraspecific genetic relatedness of C. pseudotuberculosis strains.

First isolation of Clostridium difficile PCR-ribotype 027/toxinotype III in Poland.

Abstract: Of 175 Clostridium difficile strains isolated from patient hospitalized in one academic hospital in Warsaw between 2005-2006, one isolate belonged to PCR-ribotype 027/toxinotype III. This isolate had tcdA, tcdB, binary toxin genes (cdtA and cdtB), a 18-bp deletion and a 1 bp deletion at 117 position in the tcdC gene. Antimicrobial susceptibility tests revealed high level resistance to erythromycin, moxifloxacin and gatifloxacin. This is a first report of the 027 strain of C. difficile in Poland.

Macrolide-lincosamide-streptogramin B resistant phenotypes and genotypes for methicillin-resistant Staphylococcus aureus in Turkey, from 2003 to 2006.

Abstract: Methicillin-resistant Staphylococcus aureus (MRSA) strains with inducible macrolide-lincosamide-streptogramin B (iMLS B ) resistance phenotype may lead to clinical failure during clindamycin (CLI) therapy. The aim of this study was to determine the incidence of MLS B phenotypes by using D-test method and genotypes by using multiplex real-time PCR method in MRSA strains. A total of 265 MRSA strains were obtained from clinical samples from hospitalized and outpatients. Of the MRSA isolates, 225 (84.9%) were resistant to erythromycin (ERT), and 170 (64.1%) to CLI. Among the 225 ERT-resistant MRSA strains, the constitutive MLS B (cMLS B ) rate was found in 49.3%, iMLS B in 39.1% and the M phenotype in 11.5%. Overall, ermA, ermC, ermA+ermC, msrA, ermC+msrA, and ermA+ermC+msrA genes were detected in 85 (37.7%), 60 (26.6%), 42 (18.6%), 26 (11.5%), 11 (4.8%), and 1 (0.4%) isolates, respectively. Most prevalent resistance determinant in MRSA strains was ermA, which was detected in 37.7% of the isolates. The 26 MRSA strains with M phenotype harboured only msrA gene. In conclusion, due to aware of the potential of CLI treatment failure, D-test should be performed and reported in MRSA strains in clinical laboratories. The multiplex real-time PCR method is easy to perform, fast and reliable method for the detection of MLS B resistance genotypes.

Slime production by Staphylococcus aureus strains isolated from cases of bovine mastitis

Abstract: The objective of the present research was to determine the frequency of slime production by Staphylococcus aureus strains recovered from bovine mastitis and comparison of slime formation frequency, depending on the determination procedure employed. The investigations embraced 59 Staphylococcus aureus strains obtained from the inflammatory secretion of mammary glands of 45 cows. Slime production was determined using Christensen method and Congo red agar (CRA) method. Out of the 59 S. aureus isolates, 47.45% produced slime as shown by Christensen method and 42.37% by the CRA method. However, 7 strains (11.86%) demonstrated slime production ability only when tested by the Christensen method, whereas 4 strains (6.77%) only using the CRA method.

Alpha-amylase production by Streptomyces erumpens MTCC 7317 in solid state fermentation using response surface methodology (RSM).

Abstract: Production of AE-amylase under solid state fermentation by Streptomyces erumpens MTCC 7317 has been investigated using different agroindustrial residues, i.e. cassava bagasse, sugarcane bagasse and wheat bran; wheat bran was found to be the best substrate. Among different nitrogen source supplemented to wheat bran, beef extract or peptone (1%) showed maximum enzyme production. Response surface methodology was used to evaluate the effect of main process parameters as incubation period (48 h), moisture holding capacity (70%), pH (7.0) and temperature (50∞C) on enzyme production by applying a full factorial central composite design. The maximum hydrolysis of soluble starch (90%) and cassava starch (75%) was obtained with the application of 4 ml (~12096 U) of S. erumpens crude enzyme after 5 h of incubation.

Cell surface hydrophobicity of Bacillus spp. as a function of nutrient supply and lipopeptides biosynthesis and its role in adhesion.

Abstract: Cell surface hydrophobicity (CSH) is recognised as a important factor in microbial adhesion to solid surfaces. Growth conditions have been found to determine the synthesis of extracellular molecules by microorganisms. It has major consequences in modification of bacterial surface properties and consequently, in bacterial adhesion to solid surfaces. In this paper, CSH properties of Bacillus spp. depending on the nutrient supply and lipopeptide biosynthesis and its role in bacterial adhesion to solid surfaces were investigated. The obtained results indicate that the examined factors (nitrogen and carbon availability) influence the CSH of Bacillus spp. cells. In most variants of the experiments the role of nutrient supply in adhesion process was characteristic for species. The strongest effect was observed for peptone concentration (P< 0.001). A decrease of CSH was noticed in optimal nitrogen availability (10 g/l) and it was connected with maximum yield of surfactin biosynthesis. The highest values of CSH of examined Bacillus spp. strains were observed under nitrogen starvation and in excess of carbon source. In these conditions the adhesion to stainless steel surface was more extensive.

Clinical presentation of extraintestinal infections caused by non-typhoid Salmonella serotypes among patients at the University Hospital in Cracow during an 7-year period.

Abstract: The most characteristic finding in non-typhoid salmonella (NTS) infection is acute food related outbreaks of gastroenteritis, which is usually benign and self-limiting. However, more serious extraintestinal findings, such as bacteraemia and focal infections localized to any organ may appear. The objective of this paper is to describe the most important characteristic of the extraintestinal infections due to NTS serotypes observed in University Hospital, in Cracow between January 2000 and December 2006. To do so, we reviewed the clinical presentations, risk groups, complications and outcomes of in-patients, in which extraintestinal non-typhoid Salmonella serotypes were isolated, applying a clinomicrobiological protocol. Out of 30 patients with either bacteraemias (n = 22) or focal salmonella infections (n = 8), 12 had malignancies, 17 had immune dysfunction state, 9 had gastrointestinal disorders and 8 had chronic heart, pulmonary or kidney disease. Four of these patients (13%) who had hematological malignancies (2), renal transplantation (1) and pulmonary disease (1) died. Regarding the clinical picture, primary bacteraemia and focal infections occurred with similar frequency (33.3% and 26.7%, respectively); the remaining were bacteraemias secondary to gastroenteritis. The incidence rate (mean 0.30/1000 hospital admission/year) increased steadily from 0.19/1000 to 0.32/1000 hospital admission during the study period. From 30 Salmonella isolates from extraintestinal samples collected, only four isolates were resistant to ampicillin, ciprofloxacin or trimethoprim-sulfamethoxazole. This finding indicate that multidrug resistance does not represent a serious problem among NTS serotypes collected from the our medical center as monitored over a period of 7 years. Given this presentation, clinicians need to have a high index of suspicion and to consider preemptive therapy, especially in elderly patients who are likely to develop severe immunosuppression following interventions.

Statistical optimization of alpha-amylase production by probiotic Lactobacillus plantarum MTCC 1407 in submerged fermentation.

Abstract: Production and purification of "-amylase by probiotic Lactobacillus plantarum MTCC 1407 has been investigated under submerged fermentation using Mann Rogassa Sharpe medium containing (1%) soluble starch in lieu of glucose (2%) as carbon source. Response Surface Methodology was used to evaluate the effect of main variables, i.e. incubation period, pH and temperature on enzyme production. A full factorial Central Composite Design was applied to study these main factors that affected "-amylase production. The experimental results showed that the optimum incubation period, pH and temperature were 36 h, 7.0 and 35∞C, respectively. The purified enzyme (by ammonium sulphate precipitation) had a molecular mass of 75 450 Da in SDS-PAGE.

Biodegradation of carbendazim by epiphytic and neustonic bacteria of eutrophic Chełmzyńskie Lake.

Abstract: The paper presents a study on biodegradation of carbendazim (1 mg/l) by homogeneous cultures of epiphytic (n = 25) and neustonic (n = 25) bacteria and heterogeneous (n = 1) cultures containing a mixture of 25 bacterial strains isolated from epidermis of the Common Reed (Phragmites australis, (Cav.) Trin. ex Steud.) and surface microlayer (SM ≈ 250 µm) of eutrophic lake Che‡m?yaeskie. Results indicate that epiphytic bacteria are characterized by higher average capacity to decompose carbendazim than neustonic bacteria (p< 0.05). The half-life of carbendazim in epiphytic bacterial cultures equaled an average of 60 days. In the same period, neustonic bacteria reduced the concentration of the fungicide by 31%. The level of carbendazim biodegradation in mixed cultures of epiphytic and neustonic bacteria after 20-day incubation was lower than the biodegradation level in homogeneous cultures. Sixty-day homogeneous cultures of epiphytic and neustonic bacteria were characterized by a higher mean level of carbendazim biodegradation than mixed cultures. After 40-day incubation, mean values of biodegradation of the fungicide in homogeneous and mixed cultures were similar. It was demonstrated that among epiphytic bacteria, Pseudomonas luteola was the most efficient organism in reducing the concentration of carbendazim. Among neustonic bacteria, Burkholderia cepacia and Aeromonas hydrophila were the most effective in degradation of the fungicide.

Effects of Propionibacterium on the growth and mycotoxin production by some species of Fusarium and Alternaria.

Abstract: The aim of this research was to study the antifungal properties of propionibacteria. Three fractions from cultures of Propionibacterium freudenreichii ssp. shermanii 41 and ssp. freudenreichii 111 (i.e. culture containing viable bacteria, cell-free supernatant and bacteriocin preparation) were tested for their ability to inhibit the growth and mycotoxin production of Alternaria alternata, Fusarium culmorum, Fusarium graminearum and Fusarium verticillioides. The growth of the fungi was monitored during cultivation using a plating method. The concentration of toxins produced was measured by HPLC on the 14 th day of culture. Altenuene and tenuazonic acid were determined in cultures of A. alternata whilst concentration of nivalenol, deoxynivalenol, fumonisin B 1 and zearalenone was measured in Fusarium cultures. The strongest inhibition of growth and toxin production was observed in the presence of cultures containing viable cells and supernatants obtained from propionibacteria cultures. The bacteriocin extracts generally had a weak fungistatic effect on the growth of A. alternata, F. culmorum and F. graminearum. Despite the fact that growth was slower in the presence of bacteriocin extracts than in control trials, none of the preparations prepared from the propionibacteria significantly reduced the level of mycotoxin production. The ability of P. freudenreichii ssp. freudenreichii 111 to remove zearalenone from liquid medium was also evaluated. It was shown that both viable and non-viable cells caused a decrease in zearalenone concentration in the medium.

Susceptibility pattern of some clinical bacterial isolates to selected antibiotics and disinfectants.

Abstract: The antibacterial activities of five antibiotics, three brands of Ofloxacins (Obenasin, Floxavid and Drovid) and two brands of Ciprofloxacins (Uroxin and Siprosan), and five commonly used disinfectants (Lysol, Dettol, Purit, Roberts and Wex-cide) against Staphylococcus aureus, Escherichia coli, Proteus spp., Pseudomonas aeruginosa, Streptococcus spp. and Bacillus spp. were investigated. The growth inhibitory effect of both the antibiotics and disinfectants were determined using paper disk diffusion method and well-in-agar technique respectively. The highest mean zone of growth inhibition (19.3 mm) was given by Drovid on Streptococcus spp., while the smallest (7.0 mm) was by Floxavid on P. aeruginosa. Lysol had the highest mean zone of growth inhibition (18.0 mm) on Streptococcus spp. while P. aeruginosa and Bacillus spp. had no zone of growth inhibition with Roberts at 100-fold dilution. All the isolates were also resistant to Wex-cide. The test organisms were found to be significantly susceptible to the routinely used antimicrobials tested. However, there is the need for continuous surveillance for the detection of emerging resistance pattern.

Antimicrobial Activity of 2,4-dihydro-[1,2,4]triazol-3-one Derivatives

Abstract: Antibacterial and antifungal activity of 2,4-dihydro-[1,2,4]triazol-3-one derivatives were examined by the disc-diffusion method (growth inhibition zone diameter in agar medium). The MICis for the most active agents were determined. Of all the tested compounds, aminomethyl derivatives of 2,4-dihydro-[1,2,4]triazol-3-one exhibit activity against the majority of microorganisms studied.

Stable sulfur isotope fractionation by the green bacterium Chlorobaculum parvum during photolithoautotrophic growth on sulfide

Abstract: Growing cultures of the green obligate photolithotroph, Chlorobaculum parvum DSM263(T) (formerly Chlorobium vibrioforme forma specialis thiosulfatophilum NCIB 8327), oxidized sulfide quantitatively to elemental sulfur, with no sulfate formation. In the early stages of growth and sulfide oxidation, the sulfur product became significantly enriched with S-34, with a maximum delta S-34 above +5 parts per thousand, while the residual Sulfide was progressively depleted in S-34 to delta S-34 values greater than -4 parts per thousand. As oxidation proceeded, the delta S-34 of the sulfur declined to approach that of the initial sulfide when most of the substrate sulfide had been converted to sulfur in this closed culture system. No significant formation of sulfate occurred, and the substrate sulfide and elemental sulfur product accounted for ill the sulfur provided throughout oxidation. The mean isotope fractionation factors (epsilon) for sulfide and sulfur were equivalent at c values of -2.4 parts per thousand and +2.4 parts per thousand respectively. The significance of the experimentally-observed fractionation to the S-34/S-32 ratios seen in natural sulfur-containing minerals is considered.

Proteolytic activity of clinical Candida albicans isolates in relation to genotype and strain source

Abstract: Proteolytic activity is regarded as one of the most important virulence factors of Candida albicans. Several authors recently demonstrated that some karyotypes and genotypes harbouring a group I self-splicing intron (CaLSU) located in the gene encoding the large rRNA subunit showed a high level of proteinase production. The aim of this study was to investigate the correlation between the level of proteinase production and the presence of the CaLSU intron in C albicans isolates originating from the blood and respiratory tracts (sputum/pharyngeal swabs) of patients with and without oropharyngeal candidosis. The results revealed statistically significant differences in genotype distribution and the level of proteinase production between the C albicans isolates obtained from blood and from the respiratory tract. Genotype A, without the intron, was prevalent in all groups of strains and its prevalence was higher among isolates from blood (75%) and from patients with candidosis (80%) compared with strains from colonisation (as opposed to infection) (57.8%). Isolates from blood produced significantly less proteinase than isolates from the respiratory tract (p < 0.02), and this difference should be attributed to lower proteinase production of genotypes B and C from blood compared with genotypes B and C from the respiratory tract (p < 0.01). The higher proteinase production of genotype B than of genotype A was found among respiratory tract isolates only. The presented data indicate that the association between proteinase production and the CaLSU intron depends on the strains' population. Further study is needed on well-defined groups of clinical isolates to elucidate whether the observed diversity in proteinase production plays a role in the selection of strains inducing bloodstream infections.

Studies on the survival of enterohemorrhagic and environmental Escherichia coli strains in wastewater and in activated sludges from dairy sewage treatment plants.

Abstract: Survival of Escherichia coli O157:H7 strain isolated from milk in Poland and an environmental E. coli strain in wastewater from Garwolin and £owicz dairies and in activated sludges from dairy sewage treatment plants as well as in dairy wastewater with activated sludges was examined. Environmental materials were contaminated with about 10 8 of target bacteria/ml of sample. The experiments were performed under temperature conditions typical of autumn-winter (6 o ) and spring-summer (24∞C) seasons. It was found that the non-pathogenic E. coli strain survived longer in all media than the enterohemorrhagic serotype. E. coli O157:H7 bacteria were not detected (in direct plating method) in activated sludges after 21n28 days; in dairy wastewater as well as in wastewater with activated sludges after 21n25 days. These periods for environmental E. coli strain were 35n42 days (activated sludges), 25n28 days (wastewater with activated sludges). At higher temperature environmental E. coli were not detected in wastewater from £owicz dairy sewage treatment plant after 25 days, but the bacteria were still present in wastewater from Garwolin dairy sewage tratment plant after 34 days. The obtained results show that the lack of environmental E. coli bacteria (as a indicator bacteria of fecal contamination) in dairy wastewater and in dairy wastewater with activated sludges could indicate the absence of pathogenic E. coli bacteria. Prolonged existence of the enterohemorrhagic serotype in activated sludges shows the need to treat activated sludges prior to the utilization of these materials as fertilizer.

The influence of soluble microbial products on microbial community composition: hypothesis of microbial community succession.

Abstract: Soluble microbial products (SMP) are organic compounds produced by activated sludge microorganisms as they degrade substrates. They include by-products of microbial activity, death and lysis. The available literature does not reveal how SMP influence microbial community composition. In this regard, we microscopically studied changes in composition of microbial communities, especially protozoa and metazoa, under the influence of increased as well as reduced levels of SMP. The presence of SMP at high level significantly caused changes in microbial community composition. Microbial species shifted from attached ciliates (12n175 µm) to free-swimming and crawling ciliates (35n330 µm) and then invertebrates, which included rotifers (0.2n1 mm) and nematodes (1n50 mm). The shift of smallsize microorganisms to large ones was observed as one of the most significant influences of SMP. Attached ciliates reappeared when we removed the SMP that had accumulated in the bioreactors n we have called this as the resurrection phenomenon of microorganisms. Such rapid changes in microbial community composition were not observed in the experiment with low concentration of SMP. Overall, the results suggest that accumulation of SMP is one of the intrinsic regulatory mechanisms that control viability and dormancy of microbial communities in activated sludge.

Isoglucose production from raw starchy materials based on a two-stage enzymatic system.

Abstract: A new low-cost glucoamylase preparation for liquefaction and saccharification of starchy raw materials in a one-stage system was developed and characterized. A non-purified biocatalyst with a glucoamylase activity of 3.11 U/mg, an "-amylase activity of 0.12 WU/mg and a protein content of 0.04 mg protein/mg was obtained from a shaken-flask culture of the strain Aspergillus niger C-IV-4. Factors influencing the enzymatic hydrolysis of starchy materials such as reaction time, temperature and enzyme and substrate concentration were standardized to maximize the yield of glucose syrup. Thus, a 90% conversion of 5% starch, a 67.5% conversion of 5% potato flour and a 55% conversion of 5% wheat flour to sweet syrups containing up to 87% glucose was reached in 3 h using 1.24 glucoamylase U/mg hydrolyzed substrate. The application of such glucoamylase preparation and a commercially immobilized glucose isomerase for the production of glucose-fructose syrup in a two-stage system resulted in high production of stable glucose/fructose blends with a fructose content of 50%. A high concentration of fructose in obtained sweet syrups was achieved when isomerization was performed both in a batch and repeated batch process.

Selective isolation of Bacillus thuringiensis from soil by use of L-serine as minimal medium supplement.

Abstract: The influence of L-serine on the growth of different strains of the genus Bacillus was investigated. It has been observed that the addition of L-serine to minimal synthetic media results in an inhibition in the growth of certain strains of Bacillus spp. but not B. thuringiensis. Then L-serine-resistance phenomenon was used in isolation of B. thuringiensis strains from soil. An isolation method with media supplied with L-serine was compared to the previously applied procedure (isolation on nutrient agar). L-serine-selective medium appeared to be more effective in isolation of Bt strains.