Clinical Microbiology and Infection, Volume 12, Supplement 4, 2006 Dendograms in microbial phylogenetics and epidemiological typing (Symposium arranged with ESGM) S8 S9 Evolutionary trees in microbiology Representations of strain similarities in B. Hall (Bellingham, US) molecular microbial typing (Ghent, BE) Phylogenetic trees are just tools for representing the relation- P. Vauterin ships among organisms. The focus of this presentation is on the This talk covers a variety of grouping techniques that are used to interpretation of phylogenetic trees, rather than on construction represent the relations between strains using molecular typing of those trees. Elements that will be considered are: what are data. For each technique, the strong and weak points are branches and nodes and what do they mean? Trees are typically discussed, and guidelines are given to come to a reliable drawn so that they appear to depict the order of descent from interpretation of the results. The emphasis is on traditional common ancestors, i.e. the direction of evolution. That appear- hierarchical cluster analysis tools, and we elaborate on the limits ance is often misleading. Direction of evolution and order of of their applicability. In particular, the loss of information descent are only shown by rooted trees, whereas most introduced by cluster analysis is discussed, as well as the phylogenetic methods produce unrooted trees. What informa- problem to degenerate solutions. The particular challenges tion is required to root a tree? Trees of microbial isolates often associated with the analysis and interpretation of modern include zero-length branches. What do zero-length branches large data sets potentially include thousands of organisms, really mean? Trees are only estimates of historical relationships which are also covered. We also discuss novel grouping they are not facts. How do we determine the reliability of those techniques, such as minimum spanning trees and self-organiz- estimated trees? Recombination can dramatically affect the ing maps, and show how these tools can be used complemen- validity of phylogenetic trees. What do we do when there is tary to traditional cluster analysis to gain further insight in the too much recombination to construct valid phylogenetic trees? structure of the data. Antimicrobial resistance in anaerobic bacteria. Experiences in Europe and North America (Symposium arranged with ESGARAB) S11 Clostridium perfringens, and Clostridium difficile. Two Europe- Antimicrobial susceptibility patterns in different wide resistance studies were carried out during the past European countries 15 years involving almost all European countries evaluating the development of resistance among B. fragilis and related E. Nagy (Szeged, HU) species. A similar study was done with clinical isolates of Antibiotic susceptibility testing of clinically relevant anaerobes Propionibacterium acnes and Peptostreptococci. Expressed differ- in different clinical microbiological laboratories in Europe is less ences were found in resistance levels between different Bacter- and less frequently carried out due to the fact, that clinicians oides species and between different areas of Europe for treat many presumed anaerobic infections empirically. Even less clindamycin, erythromycin, ampicillin and moxifloxacin. The data are available about the antibiotic resistance levels among same is true for Propionibacterium acnes. Resistance genes the anaerobic normal flora isolates developed due to the use of responsible for carbapenem and nitro-imidazole resistance can antibiotics for infections caused by aerobic or facultative be found more frequently among clinical and normal flora anaerobic pathogens. New antibiotics with anti-anaerobic activ- isolates, than the expressed resistance. Despite of the fact that ity may be tested on "old" isolates instead of using "recent" most anti-anaerobic drugs show good activity against anaerobic clinical isolates, which may create false susceptibility data and clinical isolates, the number of the resistant isolates is increasing incorrect recommendations for treatment of anaerobic infec- parallel with the time. Accumulation of resistance markers can tions. Most systemic data in Europe are available for few genera be observed among Bacteroides strains. Reported cases will be and species of anaerobic bacteria such as Bacteroides fragilis and discussed where clinical failure was due to the presence of related species, Fusobacterium spp., Propionibacterium acnes, multi-resistant anaerobic pathogens. 2006 Clinical Microbiology and Infection, Volume 12, Supplement 4 ISSN: 1470-9465 Abstracts Pathogenesis and prevention of nosocomial infections-new aspects (Symposium arranged with ESGNI) S12 be able to swallow their oral secretions. Oral hygiene and Infections associated with intravascular devices suctioning are important parts of nursing care, which also B. Rijnders (Rotterdam, NL) contribute to the reduction of aspiration. However, the subglot- tic space can usually not be emptied of secretions by oral Notwithstanding the progress in our understanding of the suctioning. One approach is suctioning of subglottic secretions pathogenesis of foreign body infection, catheter-related infection using a special endotracheal tube with an additional dorsal (CRI) continues to be part of the daily life in the ICU, oncology lumen right above the cuff. Whereas several researchers could or haematology unit. The consequential morbidity and longer not find a benefit, at least two studies showed subglottic hospital stay brings about considerable costs. However, several suctioning to be effective for reducing the incidence of VAP (9, interventions can reduce the incidence of CRI. 10 years ago, 10). However, it is definitely not indicated to replace a regular catheters coated or impregnated with antiseptics or antibiotics endotracheal tube by a subglottic suction tube in a patient, who became part of our armament against CRI. However, indiscrim- is already intubated. It has clearly been shown that reintubation inate prophylactic use of antibiotics increases the risk of is a risk factor for the development of pneumonias. This is most antimicrobial resistance. Furthermore the minocyclin-rifampin likely due to aspiration occurring during the deflation of the impregnated catheter (the only antibiotic impregnated catheter endotracheal tube and during the process of intubation. This with well documented efficacy) is not available in Europe. also means that thorough precautions have to be taken, when an A catheter impregnated with chlorhexidine/silver sulfadiazine endotracheal tube has to be changed for medical reasons: enteral (CS) on the outer surface is available in Europe and has been feeding should be stopped several hours in advance, the patient shown to have the incidence of CRI. Two recent clinical studies should be placed in a semi-recumbent position, the stomach and show that an improved version of this catheter (with CS on the oral cavity are suctioned as well as the subglottic space, which inner and outer surface) reduces catheter colonization with 45– can be visualized and suctioned during laryngoscopy before the 72%. In vitro evidence about the use of antiseptic agents as a cuff of the endotracheal tube is to be deflated. Reduction of substitute for antibiotic locks for the prevention of endoluminal microbial colonization of the oral cavity is a causal approach for CRI is available. However, evidence from prospective random- the prevention of VAP. It has been shown in patients undergo- ized controlled clinical trials on the use of antiseptic locks is still ing cardiac surgery, that a 0.12% oral chlorhexidine solution can scarce. Several clinical studies and a meta-analysis support the reduce the incidence of postoperative pneumonias, but it is still use of chlorhexidine as the preferred disinfectant prior to unclear, whether this should generally be recommended for catheter insertion. Recent evidence supports the use of a surgical patients (4). Recent investigations point to the import- chlorhexidine impregnated sponge that is placed around the ance of bacterial colonization of teeth in the pathogenesis of insertion site of the catheter to prevent recolonization of the VAP (5). However, antiseptic gels applied to the gingiva and insertion site and therefore also exoluminal CRI of short-term teeth were so far not effective for prevention of VAP (6). central venous as well as arterial catheters. In general it is correct Likewise iseganan, an antimicrobial peptide applied to the oral to state that microorganisms on the outer surface of the catheter cavity was also not effective, as shown in a recent multi centre (exoluminal) are the source of infection in most of the CRI in placebo-controlled double-blind trial (7). Topical application of short-term catheters and microorganisms on the inner surface antibiotics into the oropharynx is part of several trials using (endoluminal) become more important with longer duration of selective digestive decontamination (SDD) and the exclusive catheter use. This difference is however gradual. Therefore in administration to the oral cavity (SOD: selective oral decontam- most settings interventions directed against exoluminal as well ination) was effective in reducing VAP in ICU patients (1). as endoluminal CRI should be combined. Despite the above- Meanwhile, 3 independent clinical trials have shown a survival mentioned new developments, the implementation of a struc- benefit for critically ill patients treated with