Chemical and biological studies of Ribes nigrum L. buds essential oil.

Ribes nigrum buds are used in medicine for the diuretic and antiseptic properties of their volatile compounds. We present in this paper comparative data concerning the chemical composition of Ribes nigrum buds essential oils obtained from three blackcurrant varieties. Essential oils were isolated by steam distillation and were analyzed by gas chromatography coupled with mass spectrometry.

Comparative study of different methods for detection of toxic and other enzymatic factors in Vibrio cholerae strains.

The purpose of this work was to characterize the toxin profile and the presence of other virulence factors involved in the pathogenesis and biology of 13 V. cholerae O1 (11 clinical cases and 2 waters) and 6 V. cholerae non O1 strains (4 clinical cases and 2 waters) using genetic (PCR), immunological (RPLA), biochemical (NAD degradation, haemolysis, Kanagawa phenomenon, caseinase, lecithinase, mucinase, amylase, esculine hydrolysis) and cell culture (Vero E6, HEp-2) assays.

Aspects of constitutive and acquired antibioresistance in Aeromonas hydrophila strains isolated from water sources.

Over the last three decades, the literature pointed out the implications of Aeromonas species in human pathology. These species were described as being involved in intestinal (several outbreaks of acute gastroenteritis of choleric/dysenteric form or chronic diarrhoea, ulcerative colitis, etc.) in normal adults or children, as well as in extraintestinal infections in immunocompromised hosts.

Factors associated with virulence and survival in environmental and clinical isolates of Vibrio cholerae O1 and non O1 in Romania.

Four hundred ninety seven strains of Vibrio cholerae selected from isolates in Romania in the last decade 1990-1999 were investigated for antibiotic resistance and for classical and putative virulence factors. V. cholerae O1 strains predominated in clinical cases and non O1 strains in the environment, excepting in 1992 when non O1 strains were frequent in clinical and environmental sources.

[Effect of transferrin on the expression of virulence factors in Listeria monocytogenes strains].

Iron is an essential element for the great majority of microorganisms, which developed transport systems for iron acquisition, because during the colonization and invasion processes the microorganisms encounter iron-limiting conditions. The bacterial genes implicated in the iron transport and those codifying for other virulence factors are simultaneously depressed. The purpose of this study was to investigate the role of transferrin on the virulence factors expression in food isolated Listeria monocytogenes strains.

[Comparative study of classical and commercial microtest API galleries in the diagnosis of cholera infection].

Cholera still remains in the top of causes generating global mortality and morbidity, as revealed by the latest WHO reports. In 2000, on CDC/Atlanta website, the cholera agent was mentioned as potential biological weapon for bioterrorism actions in 9460 publications. Considering these aspects, a correct and rapid diagnosis is necessary in order to take appropriate epidemiological measures and to prevent the secondary transmission.

[Beta-lactam resistance in aquatic Enterobacter cloacae strains using phenotypic and genotypic criteria].

Bacterial resistance by producing of beta-lactamases represents an increasing problem of infections chemotherapy. beta-lactam hydrolyzing activities are detected in virtually all bacteria, from witch Enterobacter cloacae produce chromosomal beta-lactamases included in inducible class AmpC beta-lactamases. The purpose of this preliminary study was to investigate the antibiotic susceptibility of 7 inducible beta-lactamase-producing Enterobacter cloacae strains isolated from aquatic sources (river and polluted waters).

[Clonal analysis of some multiple antibiotic resistant E. coli strains isolated from river and polluted waters].

Several multiple antibiotic resistant E. coli strains isolated from river and polluted waters were compared for their genetic relatedness. Antibiotic susceptibility testing was performed for gentamycin, kanamycin, ampicillin, tetracycline, chloramphenicol, ceftazidime and cefotaxime, as described by Kirby-Bauer disk diffusion method following NCCLS recommendations.

[Correlation between multiple antibiotic resistance and heavy-metal tolerance among some E.coli strains isolated from polluted waters].

Self-transmissible plasmids conferring multiple antibiotic resistance are wide-spread in coliforms populations. In soil and water, multiple antibiotic resistance is clearly associated with resistance/tolerance to heavy-metals (Hg2+, Cu2+, Pb2+, Zn2+, Ca2+). For different genera the genes for heavy-metals resistance are often plasmid encoded.

[Distribution and diversity of conjugative plasmids among some multiple antibiotic resistant E.coli strains isolated from river waters].

In natural bacterial communities the microbial structure and functions are subjected to dynamic environmental and genetic adaptation. Plasmid-mediated horizontal genes transfer has a major impact on the adaptability of bacteria, exemplified by the interspecific and intergeneric transfer of antibioresistance genes in a variety of aquatic media. The high incidence of resistant bacteria has been documented for fresh waters, marine waters and chronically polluted waters.

[Study of antibiotic influence on adherence capacity of gram positive and gram negative bacteria to the cellular substrate].

Bacterial adherence to the cellular substrate (skin and mucosa) represents a precondition of infectious pathology. It was demonstrated that bacteria which adhere and form biofilms on catheters and other inert materials used in medicine are resistant to the therapeutic antibiotic concentrations being protected by the biofilm mathrix and generating severe and hard to treat infections. There are only few studies on the influence of antibiotics on the bacterial adhesins synthesis and bacterial adherence to the cellular substrate.

[ Study of exo-enzymatic profile and cytotoxic effect of bacterial culture supernatants in different growth phase].

Bacterial quorum-sensing represents an ubiquitary regulating system in which the pheromones (small molecules with different chemical structures, i.e. homoserin-lactones, octapeptides, aminoacids) act as extracellular mediators of signaling and intercellular communication.

[Factors influencing the capacity of cellular substrate adherence of vibrio cholerae O1 and non O1 strains].

Bacterial adherence to eukariotic cells represents an important step of tissue colonization and is mediated by specific molecules called adhesins. Bacterial adherence to cellular substrate is a very complex process consisting in specific interactions between the surface of host cell and bacterial cell surface respectively. Adherence to cellular substrate confers selective advantages to bacterial cells, as: rapid growth rate by shorter lag period and protection against antibodies and lysozime.

Photodynamic therapy and some clinical applications in oncology.

Photodynamic therapy (PDT), a new treatment modality for localized cancers involving the selective interaction of visible light with photosensitizers, such as hematoporphyrin derivatives (HpD) or dihematoporphyrin ether/ester (DHE) (Photofrin II). Photodynamic therapy of malignant tumors includes biological, photochemical and photophysical processes. These processes involve: (i) absorption of photosensitizing agent; (ii) selective retention of photosensitizer in tumors and (iii) irradiation of sensitized tumor by laser irradiation.