For bacterial typing to be useful, the development, validation and appropriate application of typing methods must follow unified criteria. Over a decade ago, ESGEM, the ESCMID (Europen Society for ...Clinical Microbiology and Infectious Diseases) Study Group on Epidemiological Markers, produced guidelines for optimal use and quality assessment of the then most frequently used typing procedures. We present here an update of these guidelines, taking into account the spectacular increase in the number and quality of typing methods made available over the past decade. Newer and older, phenotypic and genotypic methods for typing of all clinically relevant bacterial species are described according to their principles, advantages and disadvantages. Criteria for their evaluation and application and the interpretation of their results are proposed. Finally, the issues of reporting, standardisation, quality assessment and international networks are discussed. It must be emphasised that typing results can never stand alone and need to be interpreted in the context of all available epidemiological, clinical and demographical data relating to the infectious disease under investigation. A strategic effort on the part of all workers in the field is thus mandatory to combat emerging infectious diseases, as is financial support from national and international granting bodies and health authorities.
Penetrability of hydraulic grouts Miltiadou-Fezans, A.; Tassios, T. P.
Materials and structures,
10/2013, Letnik:
46, Številka:
10
Journal Article
Recenzirano
Design of hydraulic grouts for strengthening of masonry historical buildings seems to follow rather empirical procedures, with all the related uncertainties, both in terms of economy and efficiency. ...This paper is part of a broader attempt to establish a rational methodology for the design of such grouts, based on their discrete injectability characteristics, i.e. (i) Penetrability, (ii) Fluidity and (iii) Stability. This paper deals with penetrability and constitutes the first part of this holistic methodology. The second part regarding the fluidity and the third regarding the stability are separately published. Grouting is intended to fill voids, fissures and open joints of the masonry as a system, producing a “dendrite” (a three-dimensional skeleton), directly contributing to the strength of the masonry as a whole. However, to do so, the grout should be able to pass through the “narrowest” possible width of such discontinuities, in order to reach the maximum possible internal volume of masonry and open joints, avoiding most of possible blockages. In the specific case of three-leaf masonries, the most decisive result of the grouting is expected to be the strengthening of the bond along the interfaces between the external layers and the infill; the rather small voids, as well as pre-existing fissures along these interfaces have to be penetrated. In this paper the penetrability of hydraulic grouts is discussed, and relationships between two characteristic diameters of the grains of the solid phase of the grout and the nominal minimum width of fissures and voids of the structure to be injected are proposed. Furthermore the beneficial role of replacing part of the cement or hydraulic lime with ultrafine materials in order to improve penetrability is presented, and related criteria are proposed.
Besides its sufficient penetrability and fluidity, a hydraulic grout in order to be injectable should also exhibit an appropriate stability, i.e. to be able to keep its homogeneity during the ...injection process, up to its setting. The paper is part of a broader attempt to establish a rational methodology for the design of hydraulic grouts for strengthening of masonry historical buildings, based on their discrete injectability characteristics. The first and second part of this holistic methodology regarding the penetrability and fluidity were published elsewhere. This paper deals with stability, the third basic injectability characteristic. The most prevailing parameters shaping stability characteristics, are water content and percentage of ultrafine materials. After a brief literature survey, an oversimplified predictive model of bleeding is firstly proposed and then its validity is confirmed using the results of an experimental study. The role of superplasticizers is also discussed. In both cases, with and without superplasticizer, semi-empirical formulae are proposed, that may be useful for the design of a grout composition. Finally, the paper presents experimental results demonstrating the role of water and superplasticizer content in the appearance of segregation; some empirical formulae are also proposed for the estimation of the critical water content initiating segregation.
Résumé
En sus des exigences de pénétrabilité et de fluidité, un coulis hydraulique doit également avoir une stabilité satisfaisante pour pouvoir être injectable. Il doit ainsi pouvoir conserver son homogénéité durant tout le processus d’injection. Cet article fait partie d’une tentative plus générale destinée à établir une méthodologie rationnelle permettant la formulation des coulis hydrauliques par l’intermédiaire d’une analyse de leurs propriétés d’injectabilité. Les deux premières parties de cette méthode portant respectivement sur les caractéristiques de pénétrabilité et de fluidité ont été publiées par ailleurs. Le présent article est consacré à la stabilité, troisième propriété essentielle caractérisant l’injectabilité. Les paramètres essentiels influençant les caractéristiques de stabilité sont la teneur en eau et le pourcentage en éléments ultra fins. Après une brève analyse bibliographique, un modèle simplifié de prédiction de l’exsudation est proposé puis validé à l’aide des résultats d’une analyse expérimentale. Le rôle des superplastifiants est également discuté. Des formules semi empiriques considérant l’éventuelle présence de superplastifiant et constituant une aide dans la formulation des coulis hydrauliques sont ensuite proposées. Cet article présente enfin des résultats expérimentaux montrant le rôle de l’eau et de la teneur en superplastifiant dans l’apparition de ségrégation. Quelques formules empiriques fournissant une estimation de la teneur en eau critique provoquant une initialisation du phénomène de ségrégation sont également proposées.
In this paper we present the results of an experimental program on eight reinforced concrete columns subjected to constant axial load and reversed statically imposed displacements. The loading ...conditions simulated those of a doubly fixed column. The parameters tested were: (a) the shear ratio
α
s
=
M
/
V
h
(
α
s
=
1
, 2 and 3), (b) the amount of the longitudinal reinforcement (
ρ
s
=
0.02
, 0.04), (c) the amount of the transverse reinforcement (
ρ
w
=
0.012
, 0.019), (d) the axial load ratio (
ν
=
0.3
, 0.6), and (e) two different main reinforcement layouts (conventional and a combination of conventional and bi-diagonal reinforcement). One of the major objectives of the tests was to measure the strains of the reinforcement (longitudinal and transverse) and of the concrete along inclined force-paths. Conclusions are drawn regarding the seismic design of columns with low shear ratios.
Objectives To determine the current frequency and study the characteristics of VIM-1-producing Klebsiella pneumoniae isolates from bloodstream infections in Greek hospitals. Methods All blood ...isolates of K. pneumoniae were prospectively collected during 2004–06 in three teaching hospitals located in Athens. MICs of antibiotics were determined by the Etest. Extended-spectrum- (ESBL) and metallo-β-lactamase (MBL) production was examined by clavulanate- and EDTA-based techniques, respectively. Isolates were typed by PFGE of XbaI-digested genomic DNA. Detection of blaVIM-1 and mapping of the VIM-1-encoding integrons were performed by PCR and sequencing.β-Lactamase activities were analysed by IEF and imipenem hydrolysis was assessed by spectrophotometry. VIM-1-encoding plasmids were transferred to Escherichia coli by conjugation and transformation and characterized by Inc/rep typing and RFLP. Results Sixty-seven (37.6%) of 178 K. pneumoniae blood isolates were blaVIM-1-positive (VPKP); 77.8% of these were from ICUs. All VPKP isolates were multidrug-resistant. The MICs of carbapenems for VPKP varied from the susceptible range to high-level resistance overlapping with those of MBL-negative isolates. The EDTA-imipenem synergy methods had reduced sensitivity in detecting VPKP isolates when the MICs were in the susceptible range. ESBL production was common among VPKP isolates (n = 45, 67.2%) as indicated by resistance to aztreonam and confirmed by a clavulanate-based double-disc synergy test. The responsible ESBL was always an SHV-5-type enzyme as indicated by IEF. PFGE identified eight clusters (A–H) of VPKP isolates with related (>80%) patterns, as well as four unique types. Both inter-hospital spread of several clones and genotypic similarities among susceptible, ESBL-positive and VPKP isolates were also observed. Location of blaVIM-1 and expression of VIM-1 were studied in 12 isolates representing the eight PFGE clusters. In all isolates, blaVIM-1 was part of a class 1 integron that also carried aacA4, dhfrI, aadA and sulI. In eight isolates (clusters C, D, G and H), the blaVIM-1 integron was located in transferable IncN plasmids. A cluster F isolate carried a VIM-1-encoding, self-transferable plasmid that was not typeable by Inc/rep typing. VIM-1-encodingreplicons were not identified in three isolates (PFGE clusters A, B and E). VPKP isolates exhibited differences in imipenem-hydrolysing activities which, however, were not correlated with the respective carbapenem MICs. Conclusions A multiclonal epidemic of blaVIM-1-carrying K. pneumoniae is under way in the majorhospitals in Greece. Microorganisms producing both VIM-1 and SHV-5 constitute the prevalent multidrug-resistant population of K. pneumoniae in this setting.
In order to investigate for possible differences between paediatric and adult invasive Streptococcus pyogenes (iGAS) infections, a total of 142 cases were identified in 17 Greek hospitals during ...2003–2007, of which 96 were children and 46 adults. Bacteraemia, soft tissue infections, streptococcal toxic shock syndrome (STSS), and necrotizing fasciitis were the main clinical presentations (67·6%, 45·1%, 13·4%, and 12·0% of cases, respectively). Bacteraemia and lymphadenitis were significantly more frequent in children (P = 0·019 and 0·021, respectively), whereas STSS was more frequent in adults (P = 0·017). The main predisposing factors in children were varicella and streptococcal pharyngotonsillitis (25% and 19·8%, respectively), as opposed to malignancy, intravenous drug abuse and diabetes mellitus in adults (19·6%, 15·2% and 10·9%, respectively). Of the two dominant emm-types, 1 and 12 (28·2% and 8·5%, respectively), the proportion of emm-type 12 remained stable during the study period, whereas emm-type 1 rates fluctuated considerably. Strains of emm-type 1 from children were associated with erythromycin susceptibility, STSS and intensive-care-unit admission, whereas emm-type 12 isolates from adults were associated with erythromycin and clindamycin resistance. Finally, specific emm-types were detected exclusively in adults or in children. In conclusion, several clinical and epidemiological differences were detected, that could prove useful in designing age-focused strategies for prevention and treatment of iGAS infections.
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