Slime production and antibiotic susceptibility in staphylococci isolated from clinical samples

A total of 187 isolates from several clinical specimens were identified to species level as 129 Staphylococcus aureus strains and 58 coagulase-negative staphylococci (CNS) strains by the API Staph System (Biomerieux). Slime production was detected both by the conventional Christensen's method as well as by the Congo red agar method. Seventy-two strains of staphylococci isolates (38.5%) were found to be slime producers by Christensen's test tube method whereas 58 strains (31%) were slime positive with Congo red agar method. There was no statistically significant difference between the two methods for the detection of slime production (P > 0.05). Susceptibility of isolates against antimicrobial agents was tested by the disk diffusion method. Staphylococcal species had resistance to one or more antibiotics. Among the various antimicrobial agents, oxacillin (71.1%) and erythromycin (47.1%) showed higher resistance than most of the agents used against all isolates. Oxacillin resistant S. aureus (ORSA) and oxacillin resistant coagulase-negative staphylococci (ORCNS), 97 (75.2%) and 36 (62.1%) respectively were frequently observed in strains isolated from clinical materials. Among the ORSA strains, two strains were resistant to vancomycin. Moreover, 96 (74.4%) of 129 S. aureus strains were positive for blactamase enzyme. However, 78 (81.25%) of 96 b-lactamase positive S. aureus strains were b-lactamase positive ORSA isolates, but none of them had vancomycin resistance.

Antimicrobial activity of Brazilian copaiba oils obtained from different species of the Copaifera genus

The antimicrobial activity of copaiba oils was tested against Gram-positive and Gram-negative bacteria, yeast, and dermatophytes. Oils obtained from Copaifera martii, Copaifera officinalis, and Copaifera reticulata (collected in the state of Acre) were active against Gram-positive species (Staphylococcus aureus, methicillin-resistant S. aureus, Staphylococcus epidermidis, Bacillus subtilis, and Enterococcus faecalis) with minimum inhibitory concentrations ranging from 31.3-62.5 µg/ml. The oils showed bactericidal activity, decreasing the viability of these Gram-positive bacteria within 3 h. Moderate activity was observed against dermatophyte fungi (Trichophyton rubrum and Microsporum canis). The oils showed no activity against Gram-negative bacteria and yeast. Scannning electron microscopy of S. aureus treated with resin oil from C. martii revealed lysis of the bacteria, causing cellular agglomerates. Transmission electron microscopy revealed disruption and damage to the cell wall, resulting in the release of cytoplasmic compounds, alterations in morphology, and a decrease in cell volume, indicating that copaiba oil may affect the cell wall.

Prognostic factors in left-sided endocarditis: results from the andalusian multicenter cohort

Despite medical advances, mortality in infective endocarditis (IE) is still very high. Previous studies on prognosis in IE have observed conflicting results. The aim of this study was to identify predictors of in-hospital mortality in a large multicenter cohort of left-sided IE.Methods An observational multicenter study was conducted from January 1984 to December 2006 in seven hospitals in Andalusia, Spain. Seven hundred and five left-side IE patients were included. The main outcome measure was in-hospital mortality. Several prognostic factors were analysed by univariate tests and then by multilogistic regression model. Results.The overall mortality was 29.5% (25.5% from 1984 to 1995 and 31.9% from 1996 to 2006; Odds Ratio 1.25; 95% Confidence Interval: 0.97-1.60; p = 0.07). In univariate analysis, age, comorbidity, especially chronic liver disease, prosthetic valve, virulent microorganism such as Staphylococcus aureus, Streptococcus agalactiae and fungi, and complications (septic shock, severe heart failure, renal insufficiency, neurologic manifestations and perivalvular extension) were related with higher mortality. Independent factors for mortality in multivariate analysis were: Charlson comorbidity score (OR: 1.2; 95% CI: 1.1-1.3), prosthetic endocarditis (OR: 1.9; CI: 1.2-3.1), Staphylococcus aureus aetiology (OR: 2.1; CI: 1.3-3.5), severe heart failure (OR: 5.4; CI: 3.3-8.8), neurologic manifestations (OR: 1.9; CI: 1.2-2.9), septic shock (OR: 4.2; CI: 2.3-7.7), perivalvular extension (OR: 2.4; CI: 1.3-4.5) and acute renal failure (OR: 1.69; CI: 1.0-2.6). Conversely, Streptococcus viridans group etiology (OR: 0.4; CI: 0.2-0.7) and surgical treatment (OR: 0.5; CI: 0.3-0.8) were protective factors.Conclusions Several characteristics of left-sided endocarditis enable selection of a patient group at higher risk of mortality. This group may benefit from more specialised attention in referral centers and should help to identify those patients who might benefit from more aggressive diagnostic and/or therapeutic procedures.

Infections after PRK could have a happy ending: a series of three cases.

BACKGROUND: Infectious keratitis after PRK remains a rare but potentially devastating complication. HISTORY AND SIGNS: Medical records of 3 male patients with infectious keratitis after uneventful PRK for myopia and astigmatism were reviewed retrospectively. PRK was performed using the Wavelight Allegretto excimer laser. Postoperative care included a bandage contact lens (BCL) for 5 days, topical antibiotics, ketorolac, and artificial tears. THERAPY AND OUTCOME: Keratitis presented 2 - 4 days postoperatively. In one case, each culture was negative (case 1), and was positive for Streptococcus pneumoniae (case 2) and Staphylococcus aureus (case 3). Final BSCVA (best spectacle corrected visual acuity) after intensive antibiotic treatment and removal of BCL were 1.0 (case 1), 0.9 (case 2) and 0.3 correctable to 0.8 with pinhole (case 3). CONCLUSIONS: Postoperative broad-spectrum antibiotics are mandatory after PRK to prevent infectious keratitis. However, resistant organisms are more and more common. The presence of a bandage soft contact lens after surgery is an unfavourable element that may increase risk of infection. Based on our case series, we suggest limiting soft contact lens wear during the two postoperative days even if the corneal ulceration is not healed.

Rescue treatment with terlipressin in children with refractory septic shock: a clinical study

INTRODUCTION Refractory septic shock has dismal prognosis despite aggressive therapy. The purpose of the present study is to report the effects of terlipressin (TP) as a rescue treatment in children with catecholamine refractory hypotensive septic shock. METHODS We prospectively registered the children with severe septic shock and hypotension resistant to standard intensive care, including a high dose of catecholamines, who received compassionate therapy with TP in nine pediatric intensive care units in Spain, over a 12-month period. The TP dose was 0.02 mg/kg every four hours. RESULTS Sixteen children (age range, 1 month-13 years) were included. The cause of sepsis was meningococcal in eight cases, Staphylococcus aureus in two cases, and unknown in six cases. At inclusion the median (range) Pediatric Logistic Organ Dysfunction score was 23.5 (12-52) and the median (range) Pediatric Risk of Mortality score was 24.5 (16-43). All children had been treated with a combination of at least two catecholamines at high dose rates. TP treatment induced a rapid and sustained improvement in the mean arterial blood pressure that allowed reduction of the catecholamine infusion rate after one hour in 14 out of 16 patients. The mean (range) arterial blood pressure 30 minutes after TP administration increased from 50.5 (37-93) to 77 (42-100) mmHg (P < 0.05). The noradrenaline infusion rate 24 hours after TP treatment decreased from 2 (1-4) to 1 (0-2.5) microg/kg/min (P < 0.05). Seven patients survived to the sepsis episode. The causes of death were refractory shock in three cases, withdrawal of therapy in two cases, refractory arrhythmia in three cases, and multiorgan failure in one case. Four of the survivors had sequelae: major amputations (lower limbs and hands) in one case, minor amputations (finger) in two cases, and minor neurological deficit in one case. CONCLUSION TP is an effective vasopressor agent that could be an alternative or complementary therapy in children with refractory vasodilatory septic shock. The addition of TP to high doses of catecholamines, however, can induce excessive vasoconstriction. Additional studies are needed to define the safety profile and the clinical effectiveness of TP in children with septic shock.

Neurological complications of infective endocarditis: risk factors, outcome, and impact of cardiac surgery: a multicenter observational study.

BACKGROUND The purpose of this study was to assess the incidence of neurological complications in patients with infective endocarditis, the risk factors for their development, their influence on the clinical outcome, and the impact of cardiac surgery. METHODS AND RESULTS This was a retrospective analysis of prospectively collected data on a multicenter cohort of 1345 consecutive episodes of left-sided infective endocarditis from 8 centers in Spain. Cox regression models were developed to analyze variables predictive of neurological complications and associated mortality. Three hundred forty patients (25%) experienced such complications: 192 patients (14%) had ischemic events, 86 (6%) had encephalopathy/meningitis, 60 (4%) had hemorrhages, and 2 (1%) had brain abscesses. Independent risk factors associated with all neurological complications were vegetation size ≥3 cm (hazard ratio [HR] 1.91), Staphylococcus aureus as a cause (HR 2.47), mitral valve involvement (HR 1.29), and anticoagulant therapy (HR 1.31). This last variable was particularly related to a greater incidence of hemorrhagic events (HR 2.71). Overall mortality was 30%, and neurological complications had a negative impact on outcome (45% of deaths versus 24% in patients without these complications; P<0.01), although only moderate to severe ischemic stroke (HR 1.63) and brain hemorrhage (HR 1.73) were significantly associated with a poorer prognosis. Antimicrobial treatment reduced (by 33% to 75%) the risk of neurological complications. In patients with hemorrhage, mortality was higher when surgery was performed within 4 weeks of the hemorrhagic event (75% versus 40% in later surgery). CONCLUSIONS Moderate to severe ischemic stroke and brain hemorrhage were found to have a significant negative impact on the outcome of infective endocarditis. Early appropriate antimicrobial treatment is critical, and transitory discontinuation of anticoagulant therapy should be considered.

Acute haematogenous prosthetic joint infection: prospective evaluation of medical and surgical management

The optimum treatment for prosthetic joint infections has not been clearly defined. We report our experience of the management of acute haematogenous prosthetic joint infection (AHPJI) in patients during a 3-year prospective study in nine Spanish hospitals. Fifty patients, of whom 30 (60%) were female, with a median age of 76 years, were diagnosed with AHPJI. The median infection-free period following joint replacement was 4.9 years. Symptoms were acute in all cases. A distant previous infection and/or bacteraemia were identified in 48%. The aetiology was as follows: Staphylococcus aureus, 19; Streptococcus spp., 14; Gram-negative bacilli, 12; anaerobes, two; and mixed infections, three. Thirty-four (68%) patients were treated with a conservative surgical approach (CSA) with implant retention, and 16 had prosthesis removal. At 2-year follow-up, 24 (48%) were cured, seven (14%) had relapsed, seven (14%) had died, five (10%) had persistent infection, five had re-infection, and two had an unknown evolution. Overall, the treatment failure rates were 57.8% in staphylococcal infections and 14.3% in streptococcal infections. There were no failures in patients with Gram-negative bacillary. By multivariate analysis, CSA was the only factor independently associated with treatment failure (OR 11.6; 95% CI 1.29-104.8). We were unable to identify any factors predicting treatment failure in CSA patients, although a Gram-negative bacillary aetiology was a protective factor. These data suggest that although conservative surgery was the only factor independently associated with treatment failure, it could be the first therapeutic choice for the management of Gram-negative bacillary and streptococcal AHPJI, and for some cases with acute S. aureus infections.

Excision of the Staphylococcal Cassette Chromosome mec (SCCmec) and its crucial role in the horizontal transfer of methicillin resistance in staphylococci.

Staphylococcus aureus est un pathogène humain majeur ayant développé des résistances contre la quasi totalité des antibiotiques disponibles, incluant la très importante famille des β- lactamines. La résistance à cette classe d'antibiotiques est conférée par la « Staphylococcal Cassette Chromosome mec » (SCCmec), qui est un élément génétique mobile capable de s'insérer dans le chromosome bactérien et capable d'être transféré horizontalement chez d'autres staphylocoques. Le mécanisme moléculaire impliqué dans ce transfert horizontal demeure largement inconnu. L'une des premières étapes du transfert est l'excision du SCC mec du chromosome bactérien. Cette excision est promue par des enzymes codées par l'élément SCCmec lui- même et appelées de ce fait « Cassette Chromosome Recombinases » (Ccr). L'un des buts de ce travail de thèse a été de comprendre la régulation de l'expression des gènes codant pour les Ccr recombinases. En utilisant des outils moléculaires originaux, nous avons été en mesure de démontrer en premier lieu que les Ccr recombinases étaient exprimées de façon « bistable », c'est à dire qu'uniquement quelques pourcents de cellules dans une population exprimaient ces gènes à un temps donné. Dans un deuxième temps, nous avons également démontré que l'expression de ces gènes était régulée par des facteurs étrangers au SCC mec. L'expression bistable des recombinases est un concept important. Effectivement, cela permet à la majorité des cellules d'une population de conserver l'élément SCC mec, alors que seulement une petite fraction le perd afin de le rendre disponible pour un transfert. Ainsi, alors que l'élément SCC mec continue de se propager avec la multiplication des bactéries Staphylococcus aureus résistant à la méticilline (SARM), il peut être simultanément transmis à des souches susceptibles (Staphylococcus aureus susceptible à la méticilline, SASM), entraînant l'apparition de nouveaux SARM. De façon très intéressante, le fait que cette bistabilité est contrôlée par les bactéries, et non le SCCmec lui-même, montre que la décision de transférer ou non la cassette SCC mec appartient à la bactérie. En conséquence, il doit exister dans la nature des souches qui sont plus ou moins aptes à effectuer ce transfert. En nous appuyant sur ces observations, nous avons montré que l'excision du SCC mec était effectivement régulée de façon très étroite au cours de la division cellulaire, et ne se passait que pendant un temps limité au début de la croissance. Ce résultat est compatible avec une régulation génétique commandée par la densité cellulaire, qui pourrait être dépendante de la production de signaux extracellulaires, du type que l'on rencontre dans le quorum sensing. Les signaux hypothétiques entraînant l'excision du SCC mec restent inconnus à l'heure actuelle. La connaissance de ces signaux pourrait se révéler très importante afin de développer des stratégies pour interférer avec la dissémination de la résistance au β-lactamines. Deux sujets additionnels ont été logiquement investigués au vu de ces premiers résultats. Premièrement, si certaines souches de SARM sont plus ou moins aptes à déclencher l'excision du SCC mec, de même certaines souches de SASM devraient être plus ou moins aptes à acquérir cet élément. Deuxièmement, afin d'étudier ces mécanismes de transfert au niveau épidémiologique, il nous a été nécessaire de développer des outils nous permettant d'explorer le phénomène à une plus large échelle. Concernant le premier point, il a été postulé que certains SASM seraient réfractaires à l'intégration génomique d'un SCC mec en raison de polymorphismes particuliers à proximité du site d'insertion chromosomique (attB). En étudiant plus de 40 isolais de S. aureus, provenant de porteurs sains, nous avons confirmé ce polymorphisme dans l'environnement à'attB. De plus, nous avons pu montrer que ces régions polymorphiques ont évolué parallèlement à des groupes phylogénétiques bien connus. Ainsi, si des telles régions réfractaires à l'intégration de SCC mec existent, celles-ci devraient ségréger dans des complexes clonaux bien définis qui devraient être facilement identifiables au niveau épidémiologique. Concernant le second point, nous avons été capables de construire un système rapporteur de l'excision du SCCmec, en utilisant un plasmide à faible copie. Ce système consistait en un promoteur fort et un gène codant pour une protéine verte fluorescente (GFP) sous le contrôle d'un promoteur fort séparés à l'aide d'un élément SCC artificiel portant trois terminateurs de transcription. Ainsi, la fluorescence ne s'exprime que si l'élément SCC est excisé du plasmide. Ce système a été testé avec succès dans plusieurs types de staphylocoques, et est actuellement évalué dans d'autres souches et conditions stimulant ou inhibant l'excision. De manière générale, cette dissertation représente parcours scientifique à travers plusieurs aspects d'un problème de santé publique majeur en rapport avec la résistance bactérienne aux antibiotiques. Ce travail s'attaque à des problèmes fondamentaux concernant le transfert horizontal de l'élément SCC mec. De plus, il s'intéresse à des aspects plus généraux de cet élément génétique mobile qui pourraient se révéler très importants en terme de mouvement de gènes au sein des staphylocoques, voir d'autres bactéries gram-positives. Finalement ce travail de thèse met en place le fondamentaux requis pour des recherches futures visant à interférer avec le transfert horizontal de la résistance aux β-lactamines. - Staphylococcus aureus is a major human pathogen. Moreover, S. aureus have developed resistance to almost all available antibiotics, including the important family of β-lactam molecules. Intrinsic resistance to β-lactams is conferred by the Staphylococcal Cassette Chromosome mec (SCCmec), which is a mobile genomic island that inserts into the staphylococcal chromosome and can be horizontally transferred into other staphylococci. However, little is known about the molecular mechanisms involved in this horizontal transfer into naïve strains. One of the first steps in SCC mec horizontal transfer is its excision from the chromosome. Excision is mediated by recombinase enzymes that are encoded by SCC mec itself, and named accordingly Ccr recombinases - for Cassette Chromosome recombinases. One goal of this thesis was to understand the regulation these recombinase genes. By using original molecular tools we could demonstrate first that the Ccr recombinases were expressed in a "bistable" manner, i.e. in only few percentages of the bacterial cells at a given time, and second that they were regulated by determinants that were not encoded on the SCC mec element, but elsewhere on the staphylococcal genome. "Bistable" expression Ccr recombinases is an important concept. It allows SCC mec to be excised and thus available for horizontal transfer, while ensuring that only some cells, but not the whole population, loose their valuable SCC mec genes. Thus, while the SCC mec element expands with the multiplication of the MRSA colony, it can simultaneously be transmitted into methicillin-susceptible S. aureus (MSSA), which convert into new MRSA. Most interestingly, the fact that bistability was regulated by the cells, rather than by SCC mec, indicates that it was the choice of the bacteria to trigger or not SCC mec transfer. As a consequence, there must be, in nature, staphylococcal strains that are more or less prone to sustain SCC mec transfer. Following these seminal observations we found that excision was indeed tightly regulated during bacterial division, and occurred only during a limited period of time at the beginning of bacterial growth. This is compatible with cell-density mediated gene regulation, and may depend on the production of extracellular signal molecules that transmit appropriate orders to neighboring cells, such as in quorum sensing. The potential signal triggering SCCmec excision is as yet unknown. However, it could be critical in promoting the horizontal transfer of methicillin resistance, or for the possible development of means to interfere with it. Two additional hypothesis were logically investigated in the view of these first results. First, if some strains of MRSA might be more prone than others to promote SCC mec excision, then some strains of MS SA might be more or less prone to acquire the element as well. Second, to investigate these multiple mechanisms at an epidemiological level, one would need to develop tools amenable to explore S. aureus strains at a larger scale. Regarding the first issue, it was postulated by others that some MSSA might be refractory to SCC mec integration because they had peculiar DNA polymorphisms in the vicinity of the site-specific chromosomal entry point {attB) of SCC mec. By studying >40 S. aureus isolates from healthy carriers, we confirmed the polymorphism of the attB environment. Moreover, we could show that these polymorphic regions co-evolved with well-known phylogenic clonal clusters. Therefore, if SCCwec-refractory attB environments exist, then they would segregate in well- defined S. aureus clonal clusters that would be easy to identify at the epidemiological level. Regarding the second issue, we were able to construct a new excision reporter system in a low copy number S. aureus plasmid. The reporter system consists in a strong promoter driving a green fluorescent protein {gfp) gene, separated by an artificial SCC-like element carrying three transcriptional terminators. Thus, fluorescence is not expressed unless the SCC-like element is excised. The system has been successfully tested in several aureus and non- aureus staphylococci, and is now being applied to more strains and various excision- triggering or inhibiting conditions. Altogether the dissertation is a scientific journey through various aspects of a salient medical problem with regard to antibiotic resistance and public health threat. The research work tackles fundamental issues about the mechanisms of horizontal transfer of the SCC mec element. Moreover, it also addresses more general features of this mobile element, which could be of larger importance with regard to gene trafficking in staphylococci, and maybe other gram-positive bacteria. Finally, the dissertation sets the fundamentals for future work and possible new ways to interfere with the horizontal transfer of methicillin resistance.

Implementing statistical learning methods through Bayesian networks (Part 2): bayesian evaluations for results of black toner analyses in forensic document examination

This paper presents and discusses the use of Bayesian procedures - introduced through the use of Bayesian networks in Part I of this series of papers - for 'learning' probabilities from data. The discussion will relate to a set of real data on characteristics of black toners commonly used in printing and copying devices. Particular attention is drawn to the incorporation of the proposed procedures as an integral part in probabilistic inference schemes (notably in the form of Bayesian networks) that are intended to address uncertainties related to particular propositions of interest (e.g., whether or not a sample originates from a particular source). The conceptual tenets of the proposed methodologies are presented along with aspects of their practical implementation using currently available Bayesian network software.

Health care-associated native valve endocarditis: importance of non-nosocomial acquisition.

BACKGROUND: The clinical profile and outcome of nosocomial and non-nosocomial health care-associated native valve endocarditis are not well defined. OBJECTIVE: To compare the characteristics and outcomes of community-associated and nosocomial and non-nosocomial health care-associated native valve endocarditis. DESIGN: Prospective cohort study. SETTING: 61 hospitals in 28 countries. PATIENTS: Patients with definite native valve endocarditis and no history of injection drug use who were enrolled in the ICE-PCS (International Collaboration on Endocarditis Prospective Cohort Study) from June 2000 to August 2005. MEASUREMENTS: Clinical and echocardiographic findings, microbiology, complications, and mortality. RESULTS: Health care-associated native valve endocarditis was present in 557 (34%) of 1622 patients (303 with nosocomial infection [54%] and 254 with non-nosocomial infection [46%]). Staphylococcus aureus was the most common cause of health care-associated infection (nosocomial, 47%; non-nosocomial, 42%; P = 0.30); a high proportion of patients had methicillin-resistant S. aureus (nosocomial, 57%; non-nosocomial, 41%; P = 0.014). Fewer patients with health care-associated native valve endocarditis had cardiac surgery (41% vs. 51% of community-associated cases; P < 0.001), but more of the former patients died (25% vs. 13%; P < 0.001). Multivariable analysis confirmed greater mortality associated with health care-associated native valve endocarditis (incidence risk ratio, 1.28 [95% CI, 1.02 to 1.59]). LIMITATIONS: Patients were treated at hospitals with cardiac surgery programs. The results may not be generalizable to patients receiving care in other types of facilities or to those with prosthetic valves or past injection drug use. CONCLUSION: More than one third of cases of native valve endocarditis in non-injection drug users involve contact with health care, and non-nosocomial infection is common, especially in the United States. Clinicians should recognize that outpatients with extensive out-of-hospital health care contacts who develop endocarditis have clinical characteristics and outcomes similar to those of patients with nosocomial infection. PRIMARY FUNDING SOURCE: None.

Alfa-toksisen Staphylococcus aureuksen aiheuttama nekrotisoiva mastiitti : tapausselostus

Summary: Gangrenous mastitis caused by alpha-toxic Staphylococcus aureus - a case report

In vitro emergence of rifampicin resistance in Propionibacterium acnes and molecular characterization of mutations in the rpoB gene.

OBJECTIVES: Activity of rifampicin against Propionibacterium acnes biofilms was recently demonstrated, but rifampicin resistance has not yet been described in this organism. We investigated the in vitro emergence of rifampicin resistance in P. acnes and characterized its molecular background. METHODS: P. acnes ATCC 11827 was used (MIC 0.007 mg/L). The mutation rate was determined by inoculation of 10(9) cfu of P. acnes on rifampicin-containing agar plates incubated anaerobically for 7 days. Progressive emergence of resistance was studied by serial exposure to increasing concentrations of rifampicin in 72 h cycles using a low (10(6) cfu/mL) and high (10(8) cfu/mL) inoculum. The stability of resistance was determined after three subcultures of rifampicin-resistant isolates on rifampicin-free agar. For resistant mutants, the whole rpoB gene was amplified, sequenced and compared with a P. acnes reference sequence (NC006085). RESULTS: P. acnes growth was observed on rifampicin-containing plates with mutation rates of 2 ± 1 cfu  ×  10(-9) (4096× MIC) and 12 ± 5 cfu  ×  10(-9) (4 × MIC). High-level rifampicin resistance emerged progressively after 4 (high inoculum) and 13 (low inoculum) cycles. In rifampicin-resistant isolates, the MIC remained >32 mg/L after three subcultures. Mutations were detected in clusters I (amino acids 418-444) and II (amino acids 471-486) of the rpoB gene after sequence alignment with a Staphylococcus aureus reference sequence (CAA45512). The five following substitutions were found: His-437 → Tyr, Ser-442 → Leu, Leu-444 → Ser, Ile-483 → Val and Ser-485 → Leu. CONCLUSION: The rifampicin MIC increased from highly susceptible to highly resistant values. The resistance remained stable and was associated with mutations in the rpoB gene. To our knowledge, this is the first report of the emergence of rifampicin resistance in P. acnes.

Antibacterial burst-release from minimal Ag-containing plasma polymer coatings.

Biomaterials releasing silver (Ag) are of interest because of their ability to inhibit pathogenic bacteria including antibiotic-resistant strains. In order to investigate the potential of nanometre-thick Ag polymer (Ag/amino-hydrocarbon) nanocomposite plasma coatings, we studied a comprehensive range of factors such as the plasma deposition process and Ag cation release as well as the antibacterial and cytocompatible properties. The nanocomposite coatings released most bound Ag within the first day of immersion in water yielding an antibacterial burst. The release kinetics correlated with the inhibitory effects on the pathogens Pseudomonas aeruginosa or Staphylococcus aureus and on animal cells that were in contact with these coatings. We identified a unique range of Ag content that provided an effective antibacterial peak release, followed by cytocompatible conditions soon thereafter. The control of the in situ growth conditions for Ag nanoparticles in the polymer matrix offers the possibility to produce customized coatings that initially release sufficient quantities of Ag ions to produce a strong adjacent antibacterial effect, and at the same time exhibit a rapidly decaying Ag content to provide surface cytocompatibility within hours/days. This approach seems to be favourable with respect to implant surfaces and possible Ag-resistance/tolerance built-up.

Learning about Bayesian networks for forensic interpretation : An example based on the "the problem of multiple propositions"

Both, Bayesian networks and probabilistic evaluation are gaining more and more widespread use within many professional branches, including forensic science. Notwithstanding, they constitute subtle topics with definitional details that require careful study. While many sophisticated developments of probabilistic approaches to evaluation of forensic findings may readily be found in published literature, there remains a gap with respect to writings that focus on foundational aspects and on how these may be acquired by interested scientists new to these topics. This paper takes this as a starting point to report on the learning about Bayesian networks for likelihood ratio based, probabilistic inference procedures in a class of master students in forensic science. The presentation uses an example that relies on a casework scenario drawn from published literature, involving a questioned signature. A complicating aspect of that case study - proposed to students in a teaching scenario - is due to the need of considering multiple competing propositions, which is an outset that may not readily be approached within a likelihood ratio based framework without drawing attention to some additional technical details. Using generic Bayesian networks fragments from existing literature on the topic, course participants were able to track the probabilistic underpinnings of the proposed scenario correctly both in terms of likelihood ratios and of posterior probabilities. In addition, further study of the example by students allowed them to derive an alternative Bayesian network structure with a computational output that is equivalent to existing probabilistic solutions. This practical experience underlines the potential of Bayesian networks to support and clarify foundational principles of probabilistic procedures for forensic evaluation.

Atividade antioxidante e antimicrobiana de extratos de atemoia (Annona cherimola Mill. x A. squamosa L.)

O objetivo deste trabalho foi quantificar os teores de fenóis e flavonoides totais, bem como avaliar as atividades antioxidante e antimicrobiana de extratos obtidos dos talos e folhas de atemoia (A. cherimola Mill. x A. squamosa L.), que pertence à família Annonaceae. A atividade antioxidante foi avaliada pelos métodos de sequestro dos radicais 2,2-difenil-1-picrilhidrazil (DPPH) e 2,2'-azinobis-3-etilbenzotiazolina-6-ácido sulfônico (ABTS), bem como pelo método da cooxidação do β-caroteno/ácido linoleico. A avaliação da atividade antimicrobiana dos extratos foi analisada contra 10 cepas de bactérias. Os resultados da atividade antioxidante dos extratos mostraram que o extrato etanólico dos talos (EEt) foi o antioxidante mais efetivo (IC50 = 10,44 ± 1,25 µg/mL) no método do sequestro do DPPH, bem como no sequestro do radical ABTS (24,81 ± 0,49%). O extrato hexânico das folhas apresentou o melhor percentual de atividade antioxidante no ensaio do β-caroteno/ácido linoleico (41,12 ± 4,35%). Os extratos etanólico dos talos e metanólico das folhas mostraram-se ativos contra cepas de Bacillus cereus, Klebsiella pneumoniae, Staphylococcus aureus resistente à meticilina (MRSA), Staphylococcus aureus e Staphylococcus epidermidis.