86,583 research outputs found
Effect of the inoculum size on susceptibility tests perfomed on sessily growing bacteria.
No full textIt has been clearly established that the inoculum size greatly affects the results of antibiotic susceptibility tests performed in both liquid and solid media in standard laboratory growth conditions (i.e. planktonic). Recently methods were developed to perform antibiotic susceptibility tests on bacteria growing in sessile conditions. The present study investigates the effect of the inoculum size on results obtained by these methods. Results show that the inoculum size does not affect tests performed in sessile conditions. A simple and reliable method is proposed to be applied to routine microbiological laboratory procedures
Modified Mc Conkey medium which allows simple and reliable identification of Providencia stuartii.
No full text
GROWTH AND ADSORPTION OF STREPTOCOCCUS-MUTANS 6715-13 TO HYDROXYAPATITE IN THE PRESENCE OF LACTOFERRIN
No full textThe growth of Streptococcus mutans 6715-13 in a rich medium (Todd Hewitt broth) was drastically reduced by addition of apo-lactoferrin (apo-Lf); this effect was bacteriostatic and reversible by saturation of Lf with iron. The influence of Lf, salivary proteins (SP) and bovine serum albumin (BSA) on the attachment of Streptococcus mutans to hydroxyapatite (HA) was successively investigated. Sorption of Lf, SP, and BSA to HA was dependent on the protein concentration and reached the end-point at about 80 mg of proteins per gram of HA. Similarly, the number of streptococci adsorbed to HA was correlated to the amount of cells available up to at least 10(7) cells per mg of HA. The adsorption of Lf, SP and BSA on HA reduced the number of attaching S. mutans cells. In particular, SP reduced the adsorption of S. mutans by 30%, whereas pre-coating of HA with apo- or iron-saturated Lf resulted in a three orders of magnitude reduction of S. mutans adsorption to HA, as demonstrated by means of different experimental procedures. The powerful adherence-inhibiting effect of apo-Lf together with its noticeable antibacterial activity towards S. mutans points to a biological significance of these phenomena also in vivo
Ruolo del ferro nell’attivazione del sistema di secrezione di tipo III dei batteri enteroinvasivi.
No full textLF immunomodulatory strategies: mastering bacterial endotoxin
No full textLactoferrin (LF), an iron-binding glycoprotein expressed in most biological fluids, represents a major component of mammalian innate immune system. The multiple activities of LF rely not only on its capacity to bind iron but also to interact with molecular and cellular components of both the host and pathogens. LF can bind and sequester lipopolysaccharide thus preventing proinflammatory pathway activation, sepsis, and tissue damage. However, the interplay between LF and lipopolysaccharide is complex and may lead to different outcomes including both the suppression of inflammatory response and immune activation. Understanding the molecular basis and the functional consequences of this complex interaction is critically relevant in the development of LF-based therapeutic interventions in humans
A species-specific DNA probe for Providencia stuartii identification
No full textA DNA probe is described that can be used for identification of Providencia stuartii by means of filter hybridization assays. The probe, which is a fragment of the P. stuartii phoN gene coding for an acid phosphatase, appeared to be able to recognize only P. stuartii strains in slot-blot hybridization experiments performed with total DNA extracted from 545 strains of 64 different Gram-negative bacterial species, including all the major representatives of the family Enterobacteriaceae. Owing to the problems that may be often encountered for correct identification of P. stuartii at the species level when using commercial identification systems, this probe may result useful for fast and reliable identification of P. stuartii strains for taxonomical, epidemiological and diagnostic studies
COMMERCIAL IDENTIFICATION SYSTEMS OFTEN FAIL TO IDENTIFY PROVIDENCIA-STUARTII
No full textWe tested 145 clinical isolates in an attempt to evaluate some of the most widely used commercial
identification systems in Europe in terms of their ability to identify Providencia strains. Two manual
miniaturized systems (API 20E and Enterotube II) and three mechanized-automated systems (Cobas-Bact,
Sceptor System, and Titertek-Enterobac-Rapid Automated System) were evaluated. Providencia alcalifaciens
and Providencia rettgeri strains were correctly identified by all systems in ail cases, and in most cases
identification was achieved without the aid of supplementary tube tests. By contrast, Providencia stuartii was
identified without the aid of supplementary tube tests for only 42.5% (API 20E), 37.5% (Enterotube), 68.7%
(Sceptor), and 71.2% (Cobas-Bact) of the isolates. The overall misidentification rates were 16.3, 11.3, 11.3, and
10%, respectively. The Titertek-Enterobac-Rapid Automated System failed to identify only 1 of 80 strains
(1.3%) and required supplementary tests in 2 other cases (2.5%). Since four of the multitest systems examined
often failed to correctly identify P. stuartil, we conclude that supplementary conventional tube tests should
always be used to distinguish this species from the other taxa of the Proteeae tribe
Structure and activity of lactoferrin — A multi-functional protective agent for human health
No full textThe Chryseobacterium meningosepticum PafA enzyme: prototype of a new enzyme family of prokaryotic phosphate-irrepressible alkaline phosphatases?
No full textChryseobacterium meningosepticum is an aerobic Gram-negative rod widely distributed in natural environments. Unlike many bacteria, it produces a phosphate-irrepressible periplasmic alkaline phosphatase (AP). This work describes cloning of the gene encoding that enzyme from C. meningosepticum CCUG 4310 (NCTC 10585), and preliminary characterization of its product. The gene, named pafA, encodes a protein (PafA) of 546 amino acids with a calculated molecular mass of the mature peptide of 58682 Da. PafA exhibits high sequence identity with the PhoV AP of Synechococcus PCC 7942 (49.9% identity) and with the Cda Ca2+-dependent ATPase of Myroides odoratus (51.9% identity), while being more distantly related to the PhoD AP of Zymomonas mobilis (22.1% identity) and to the PhoA AP of Escherichia coli (14.0% identity). PafA was partially purified; it exhibits optimal activity at pH 8.5 and is active towards a broad spectrum of substrates including both phosphomonoesters and ATP, with preferential activity for the latter compound. The present findings allow definition of a new family of APs including 60 kDa, periplasmic enzymes whose expression is not influenced by freely available Pi in the medium. Moreover, PafA can be considered an evolutionary intermediate between Ca2+-ATPase of M. odoratus and the APs PhoV of Synechococcus PCC 7942 and PhoD of Z. mobilis
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