"Folia Microbiologica"

Khammuang, Saranyu;Sarnthima, Rakrudee

doi: 10.1007/s12223-012-0151-4pmid: 22678697

Abstract Melanins are complex natural pigments that darken the skin and are difficult to degrade. This study evaluated synthetic melanin decolorization by the crude laccase from fungus Lentinus polychrous in the absence and presence of selected redox mediators. The greatest melanin decolorization activity was 87 % at pH 6.5 within 3 h in the presence of 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS), whereas only about 22 % melanin decolorized at pH 5.0 in case of no mediator. The optimum temperatures for melanin decolorization in the absence and presence of ABTS were 55 and 35°C, respectively. Using a natural redox mediator, 1.0 mmol/L vanillin leads to 45 % melanin decolorization. Our results suggest the possibility of applying vanillin for L. polychrous laccase-catalyzed decolorization of melanin.

Zhou, Ying;Hou, Zheng;Fang, Chao;Xue, Xiaoyan;Da, Fei;Wang, Yukun;Bai, Hui;Luo, Xiaoxing

doi: 10.1007/s12223-012-0168-8pmid: 22684972

Abstract In consideration of high production costs of new antimicrobial drugs, a more convenient and economical method for time–kill study is urgently required. In the present experiment, we attempted to demonstrate the feasibility of microplate method as an alternative measure of macrodilution method for time–kill study. Three conventional antibiotics (ciprofloxacin, ceftazidime, and levofloxacin) and two antimicrobial peptides [A-thanatin and K4-S4(1–16)a] were used to determine time–kill curves against Escherichia coli ATCC 25922 and Staphylococcus epidermidis ATCC 14990. Meanwhile, both methods were also performed with three antisense peptide nucleic acids (PNA3, PNA4, and PNA5) targeting ropD gene of Staphylococcus aureus ATCC 29213 and MRSA WHO-2. In order to study the correlation between the two methods, the growth inhibition rate of PNAs, antimicrobial peptides, and antibiotics for the tested strains were evaluated. A strong agreement between the results obtained from the two methods has been demonstrated. Although microplate method required longer incubation time for a significant result than macrodilution method, the former provides a more convenient, economical, and stable way to perform time–kill test for these agents. Thus, we concluded that microplate method was an available measure for time–kill study of new antimicrobial drugs.

Sadok, Khouadja;Mejdi, Snoussi;Nourhen, Saidi;Amina, Bakhrouf

doi: 10.1007/s12223-012-0174-xpmid: 22684973

Abstract The genus Vibrio is characterized by a large number of species and some of them are human pathogens causing gastrointestinal and wound infections through the ingestion or manipulation of contaminated fishes and shellfish including Vibrio parahaemolyticus and Vibrio alginolyticus. In this study, we reported the phenotypic and molecular characterization of 9 V. parahaemolyticus and 27 V. alginolyticus strains isolated from outbreaks affecting cultured Gilthead sea bream (Sparus aurata L.) and Sea bass (Dicentrarchus labrax) along the Tunisian coast from 2008 to 2009. All isolates were tested for the presence of DNase, caseinase, protease, lipase, amylase, gelatinase, hemolytic activity and antibacterial resistance to different drugs. Randomly amplified polymorphic DNA was used to examine the genetic relatedness among the V. parahaemolyticus and V. alginolyticus strains.

Montagna, Maria Teresa;Coretti, Caterina;Rella, Antonella;Barbuti, Giovanna;Manca, Fabio;Montagna, Osvaldo;Laforgia, Nicola;Caggiano, Giuseppina

doi: 10.1007/s12223-012-0169-7pmid: 22688898

Abstract Candidemia is a major infectious complication in neonatal patients. The isolation of yeasts from blood is still the “gold standard” for its diagnosis, but other laboratory markers (i.e., circulating antigens) have been studied with varying specificities and sensitivities. The aim of this study was to evaluate the role of procalcitonin for the diagnosis of candidemia in neonatal patients at high risk. To verify if the use of different commercial methods can highlight dissimilar results of sensitivity and/or specificity, the determination of procalcitonin serum levels was estimated by two systems. Overall, 90 patients from a Neonatal Intensive Care Units were enrolled, of whom six developed Candida bloodstream infection. Four of six infants with candidemia had slight increase of procalcitonin values (0.5–1 ng/mL). Only one baby showed very high levels but he had fungal and bacterial sepsis at the same time, while no elevation was observed in the sixth patient. No statistically significant difference was observed between two different methods at the time of monitoring (p > 0.643). Both methods showed a sensitivity of 83.3 % at diagnosis, while the specificity was 73.8 and 63.1 % by methods A and B, respectively. In the light of the low sensibility and specificity of this assay, we can assume that the determination of procalcitonin would not seem to play a significant role in the diagnosis of fungal infection in neonatal patients.

Sepová, Hana Kiňová;Bilková, Andrea

doi: 10.1007/s12223-012-0166-xpmid: 22688897

Abstract Five new strains of lactobacilli isolated from goatling’s stomach were identified by molecular–biological approaches. Profiles of fermentable saccharides, Gram staining, and cell morphology were also determined. They were identified as Lactobacillus reuteri (strains KO4b, KO4m, KO5) and as Lactobacillus plantarum (strains KG1z, KG4). In DNA samples of all newly isolated L. reuteri strains as well as in L. reuteri E (Lreu E; originated from lamb), the part of gldC gene, coding large subunit of glycerol dehydratase, that is necessary for 3-hydroxypropionaldehyde (3-HPA; reuterin) production, was amplified using two designed primer sets. However, the 3-HPA production was revealed only in the strain Lreu E. It produced five- or ten-fold lower amount of 3-HPA in comparison with probiotic L. reuteri ATCC 55730 in aerobic or anaerobic conditions, respectively. Moreover, Lreu E completely lost its production ability after ca. five passages in MRS medium. The co-incubation of Lreu E, but not other L. reuteri isolates, with Escherichia coli re-induced 3-HPA production. In the case of L. reuteri ATCC 55730, the 3-HPA production increased more than four times after co-incubation with E. coli.

Trabelsi, Lamia;Ouada, Hatem Ben;Zili, Fatma;Mazhoud, Nahla;Ammar, Jihen

doi: 10.1007/s12223-012-0170-1pmid: 22688899

Abstract The kinetic study of Arthrospira platensis extracellular polymeric substances (EPS) production under different trophic modes—photoautotrophy (100 μmol photons m−2 s−1), heterotrophy (1.5 g/L glucose), and mixotrophy (100 μmol photons m−2 s−1 and 1.5 g/L glucose)—was investigated. Under photoautotrophic and heterotrophic conditions, the maximum EPS production 219.61 ± 4.73 and 30.30 ± 1.97 mg/L, respectively, occurred during the stationary phase. Under a mixotrophic condition, the maximum EPS production (290.50 ± 2.21 mg/L) was observed during the early stationary phase. The highest specific EPS productivity (433.62 mg/g per day) was obtained under a photoautotrophic culture. The lowest specific EPS productivity (38.33 mg/g per day) was observed for the heterotrophic culture. The effects of glucose concentration, light intensity, and their interaction in mixotrophic culture on A. platensis EPS production were evaluated by means of 32 factorial design and response surface methodology. This design was carried out with a glucose concentration of 0.5, 1.5, and 2.5 g/L and at light levels of 50, 100, and 150 μmol photons m−2 s−1. Statistical analysis of the model demonstrated that EPS concentration and EPS yield were mainly influenced by glucose concentration and that conditions optimizing EPS concentration were dissimilar from those optimizing EPS yield. The highest maximum predicted EPS concentration (369.3 mg/L) was found at 150 μmol photons m−2 s−1 light intensity and 2.4 g/L glucose concentration, while the highest maximum predicted EPS yield (364.3 mg/g) was recorded at 115 μmol photons m−2 s−1 light intensity and 1.8 g/L glucose concentration.

Szczuka, Ewa;Urbańska, Katarzyna;Pietryka, Marta;Kaznowski, Adam

doi: 10.1007/s12223-012-0175-9pmid: 22711180

Abstract Many serious diseases caused by Staphylococcus aureus appear to be associated with biofilms. Therefore, we investigated the biofilm-forming ability of the methicillin-resistant S. aureus (MRSA) isolates collected from hospitalized patients. As many as 96 % strains had the ability to form biofilm in vitro. The majority of S. aureus strains formed biofilm in ica-dependent mechanism. However, 23 % of MRSA isolates formed biofilm in ica-independent mechanism. Half of these strains carried fnbB genes encoding surface proteins fibronectin-binding protein B involved in intercellular accumulation and biofilm development in S. aureus strains. The biofilm structures were examined via confocal laser scanning microscopy (CLSM) and three-dimensional structures were reconstructed. The images obtained in CLSM revealed that the biofilm created by ica-positive strains was different from biofilm formed by ica-negative strains. The MRSA population showed a large genetic diversity and we did not find a single clone that occurred preferentially in hospital environment. Our results demonstrated the variation in genes encoding adhesins for the host matrix proteins (elastin, laminin, collagen, fibronectin, and fibrinogen) and in the gene involved in biofilm formation (icaA) within the majority of S. aureus clones.

Koreň, Ján;Čurová, Katarína;Kmeťová, Marta;Siegfried, Leonard;Jankó, Viktor;Kovács, László;Hupková, Helena;Luha, Ján

doi: 10.1007/s12223-012-0176-8pmid: 22718252

Abstract A total of 145 Escherichia coli strains causing pyelonephritis in children were investigated for the prevalence of genes encoding the following virulence factors (VFs): P fimbria (67.6 %), S fimbria (53.8 %), AFA adhesins (2.8 %), cytotoxic necrotizing factor 1 (37.9 %), α-hemolysin (41.4 %), and aerobactin (71.7 %). One hundred and thirty-six (93.8 %) isolates harbored at least one of the virulence genes detected in the present study. Statistically significant co-occurrent presence of two VF genes was found for α-hly–cnf1, α-hly–sfa, cnf1–sfa (p < 0.001), and α-hly–pap (p = 0.001). Twenty-six profiles of VF genes were detected in this study. The combinations of aer–pap and aer–pap–sfa–α-hly–cnf1 were presented with the highest frequency—both of them in 28 isolates (19.3 %). All E. coli strains included in the study were susceptible to meropenem, amikacin, and tobramycin; the highest frequency resistance was found toward ampicillin (43.4 %), piperacillin (31.7 %), tetracycline (15.9 %), and trimethoprim/sulfamethoxazole (11.7 %). The resistance to the other tested antimicrobial drugs did not exceed 3 % incidence. Overall, 55.9 % strains were susceptible to all tested anti-infective agents. Antimicrobial resistance of E. coli strains toward trimethoprim/sulfamethoxazole statistically significantly correlated with the presence of α-hly (p < 0.001), sfa (p < 0.01), and cnf1 (p < 0.05).

Stefanis, Christos;Alexopoulos, Athanasios;Voidarou, Chrissa;Vavias, Stavros;Bezirtzoglou, Eugenia

doi: 10.1007/s12223-012-0179-5pmid: 22791233

Abstract Soil microbial populations play crucial role in soil properties and influence below-ground ecosystem processes. Microbial composition and functioning changes the soil quality through decomposition of organic matter, recycling of nutrients, and biological control of parasites of plants. Moreover, the discovery that soil microbes may translate into benefits for biotechnology, management of agricultural, forest, and natural ecosystems, biodegradation of pollutants, and waste treatment systems maximized the need of scientists for the isolation and their characterization. Operations such as the production of antibiotics and enzymic activities from microorganisms of soil constitute objectives of industry in her effort to cope with the increase of population of earth and disturbance of environment and may ameliorate the effects of global climate change. In the past decades, new biochemical and molecular techniques have been developed in our effort to identify and classify soil bacteria. The goal of measuring the soil microbial diversity is difficult because of the limited knowledge about bacteria species and classification through families and orders. Molecular techniques extend our knowledge about microbial diversity and help the taxonomy of species. Measuring and monitoring soil microbial communities can lead us to better understanding of their composition and function in many ecosystem processes.

Ondriska, František;Vrabcová, Ivana;Brinďáková, Silvia;Kváč, Martin;Ditrich, Oleg;Boldiš, Vojtech;Bastlová, Marcela

doi: 10.1007/s12223-012-0182-xpmid: 22826020

Abstract Cryptosporidiosis belongs to the important parasitic infections with zoonotic potential and the occurrence in European countries is rare. The first cases of cryptosporidiosis caused by Cryptosporidium hominis detected in the Slovak republic were described here. Collection of examined humans consisted of five family members. Faecal specimens were examined by formalin sedimentation, by the Sheather’s sugar flotation and by immunochromatography and visualised by the Ziehl–Neelsen acid fast stain. A fragment of the Cryptosporidium small subunit ribosomal RNA gene was amplified by nested polymerase chain reaction and species was determined by restriction fragment length polymorphism analysis with the endonucleases SspI and VspI. C. hominis was found in faeces of two immunocompetent siblings (a 7-year-old boy and a 2-year-old girl). The symptoms occurred only in the boy as gastrointestinal disorders lasting 5 days, and manifested by abdominal pain, an elevated body temperature (37.2 °C), mild diarrhoea, accompanied by lassitude, depression and anorexia. Ultrasonic scan revealed enlarged spleen and mezenteric lymph nodes. Microscopic examination of the stool sample revealed numerous Cryptosporidium oocysts. The DNA typing identified C. hominis subtype IbA10G2. Cryptosporidium was also detected in the boy’s sister without any complications and symptoms. Their father, mother and grandmother were parasitologically negative. The source of infection remained unknown. Human cases in present study reflect necessity of systematic attention on intestinal parasites diagnostic inclusive of cryptosporidia.