Search

A series of discrete elements simulations is presented for the study of fault gouges' frictional response. The gouge is considered to have previously undergone ultra-cataclastic flow and long-time consolidation loading. We explore the effect of different particle characteristics such as size, polydispersity, and also shearing velocities on gouge's response under the conditions met in the seismogenic zone. Monte-Carlo analyses suggest that the local stick-slip events disappear when averaging over a large number of numerical samples. Moreover, the apparent material frictional response remains almost unaffected by the spatial randomness of particles' position and by the particle's size distribution. On the contrary, the mean particle size controls the formation and thickness of the observed shear bands, which appear after the peak friction is met. Furthermore, the apparent friction evolution fits well to an exponential decay law with slip, which involves a particle size dependent critical slip distance. For the studied conditions and depth, the shearing velocity is found to play a secondary role on the apparent frictional response of the gouge, which highlights the importance of analyses involving multiphysics for studying the rheology of fault gouges. Besides improving the understanding of the underlying physics of the problem, the above findings are also useful for deriving pertinent constitutive models in the case of modeling with continuum theories., (© 2022 The Authors.)

We propose a theory for preventing instabilities and inducing controlled, slow-slip in frictionally unstable systems, such as the Generalized-Burridge-Knopoff (GBK) model and seismic fault models. We exploit the dependence of friction on pressure and use it as a backdoor for altering the dynamics of the underlying dynamical system. We use the mathematical Theory of Control and, for the first time, we manage to (a) stabilize and restrict chaos in this kind of systems, (b) guarantee slow frictional dissipation and (c) tune the system toward desirable global asymptotic equilibria of lower energy. Our control approach is robust and does not require exact knowledge of the frictional or elastic behavior of the system. Numerical examples of control are given for a Burridge-Knopoff system and a strike-slip fault model obeying rate-and-state friction. GBK models are known to present Self-Organized Critical (SOC) behavior. Therefore, the presented methodology shows an additional example of SOC Control. Even though further developments are necessary before any practical application, we expect our methodology to inspire earthquake mitigation strategies regarding anthropogenic and/or natural seismicity., (© 2022. The Authors.)

Black widow spider is endemic in the Mediterranean area and although envenomations are rare, may occasionally lead to death. We present a case of a 64-year-old female developing a rare variant of takotsubo, stress-induced, cardiomyopathy after a spider bite. This resulted in acute heart failure within 24  hours of the bite. With medical treatment and supportive care, the patient's clinical condition improved. Reverse takotsubo cardiomyopathy was diagnosed by echocardiography, which was transient. Clinical and echocardiographic findings have been completely resolved on follow-up 46 days later. Reverse takotsubo cardiomyopathy has not been yet described following a spider bite. Doctors in the emergency department of endemic countries should be familiar with this potential complication.

Carbapenemase-producing Klebsiella pneumoniae strains (CP-Kps) are currently among the most important nosocomial pathogens. An observational study was conducted during 2009 to 2010 in two hospitals located in a high-prevalence area (Athens, Greece). The aims were (i) to evaluate the clinical outcome of patients with CP-Kp bloodstream infections (BSIs), (ii) to identify predictors of mortality, and (iii) to evaluate the various antibiotic schemes employed. A total of 205 patients with CP-Kp BSIs were identified: 163 (79.5%) were infected with KPC or KPC and VIM, and 42 were infected with VIM producers. For definitive treatment, 103 patients received combination therapy (two or more active drugs), 72 received monotherapy (one active drug), and 12 received therapy with no active drug. The remaining 18 patients died within 48 h after the onset of bacteremia. The all-cause 28-day mortality was 40%. A significantly higher mortality rate was observed in patients treated with monotherapy than in those treated with combination therapy (44.4% versus 27.2%; P=0.018). The lowest mortality rate (19.3%) was observed in patients treated with carbapenem-containing combinations. In the Cox proportion hazards model, ultimately fatal disease (hazards ratio [HR], 3.25; 95% confidence interval [CI], 1.51 to 7.03; P=0.003), the presence of rapidly fatal underlying diseases (HR, 4.20; 95% CI, 2.19 to 8.08; P<0.001), and septic shock (HR, 2.15; 95% CI, 1.16 to 3.96; P=0.015) were independent predictors of death. Combination therapy was strongly associated with survival (HR of death for monotherapy versus combination, 2.08; 95% CI, 1.23 to 3.51; P=0.006), mostly due to the effectiveness of the carbapenem-containing regimens.

We present 2 cases of HIV-related cryptococcal meningitis, persisting after 3 and 9 months, respectively, of standard treatment. Both patients were treated successfully with a salvage regimen consisting of the combination of liposomal amphotericin B (3 mg/kg), intravenous voriconazole, and subcutaneous recombinant interferon γ-1b (200 μg thrice weekly). Voriconazole was administered at an increased dose (5 mg/kg, twice daily) to overcome interactions with co-administered ritonavir. In both patients, resolution of clinical signs and symptoms, as well as sterilization of cerebrospinal fluid cultures occurred after 10 weeks of salvage therapy. No major side effects were encountered. At the end of treatment, both patients were placed on maintenance therapy with oral fluconazole; no recurrence has been observed after 4 years of follow-up., (Copyright © 2012 Elsevier Inc. All rights reserved.)

This study evaluated the incidence of colonization and infection related to Central Vascular Catheters (CVC) in a tertiary care Greek hospital, as well as risk factors associated with catheter-related bloodstream infection (CRBSI). A total of 340 CVCs, were studied in relation to patient clinical and epidemiological data, CVC characteristics, and microbiological culture results. Risk factors were assessed. Pulsed field gel electrophoresis was used for the investigation of the clonal relationship of the isolates. The incidence for CRBSI and catheter colonization (CC) was 11.47 and 19.49 per 1,000 catheter days, respectively. Risk factors independently associated with CRBSI were use of corticosteroids, diabetes mellitus, solid organ neoplasm, long duration of catheterization, and changing the CVC dressing at intervals of 48 hours or more. Risk factors for CC were diabetes mellitus, hospitalization in ICU, and prolonged hospitalization. The predominant microorganisms isolated from CRBSI episodes were coagulase-negative staphylococci. All patients with CVC require constant infection surveillance and appropriate care by trained medical staff. Use of CVC for the shortest time possible, good hand hygiene and change of CVC dressing at intervals of less than 48 hours are infection prevention practices that need to be followed.

The in vitro activity of plazomicin was evaluated against 300 multidrug resistant (MDR) (carbapenemase and/or ESBL-producing) isolates from four hospitals in Athens, an area where carbapenemase-producing organisms are endemic. Most of the isolates were also resistant to the legacy aminoglycosides with the MIC₅₀/MIC₉₀ to tobramycin, amikacin and gentamicin being 32/>32, 32/>32 and 4/>8 μg/ml, respectively. ACHN-490 retained activity (MICs ≤ 4 μg/ml) against all isolates of Klebsiella pneumoniae, Escherichia coli, and Enterobacter spp. tested with MIC₅₀ and MIC₉₀ of 1 and 2 μg/ml, respectively, irrespective of their MDR phenotype and it represents a promising alternative for the treatment of the most problematic Gram-negative pathogens.

In order to investigate differences among infections due to Gram-negative anaerobic bacteria (Bacteroides, Prevotella and Fusobacterium spp.), clinical, epidemiological, and microbiological data were collected and evaluated from 206 anaerobic infections. The most frequently isolated species was Bacteroides fragilis. The majority of the cases were intra-abdominal infections (49%) followed by skin and soft tissue infections (24.7%). Logistic regression analysis showed that Bacteroides spp. strains were more often isolated from intra-abdominal infections (p = 0.002), whereas Prevotella spp. were isolated more frequently from cases with shorter duration of hospitalization (p = 0.026), and less frequently from bloodstream infections (p = 0.049). In addition, Bacteroides spp. were associated with coinfection due to Enterobacteriaceae species (p = 0.007), whereas Prevotella spp. were associated with coinfection due to Staphylococcus spp. (p = 0.002). Patients with an infection due to B. fragilis, were more frequently admitted in a general surgical ward (p = 0.017), or have been treated with a 2nd generation cephalosporin before anaerobic infection onset (p = 0.05). Total mortality was 10.9% and was associated with bacteremia (p = 0.026), and hematological (p = 0.028), or solid organ malignancy (p = 0.007). Metronidazole resistance was detected only among Prevotella spp. (16.2%) and B. fragilis group (0.8%) isolates. In conclusion, this study indicated differences between infections due to the most frequently isolated Gram-negative anaerobic species, differences that may affect the design and implementation of empirical antimicrobial chemotherapy guidelines., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

hyplex®-MBL ID Multiplex PCR-ELISA, a novel method for identifying metallo-β-lactamase genes directly in clinical specimens, was evaluated using a consecutive collection of 326 samples from three hospitals in Greece characterized by high prevalence of VIM producers. The method exhibited high sensitivity (98.0%) and specificity (98.6%) and was proven reliable in detecting bla(VIM) genes in blood, urine, pus, and sputum samples that, as confirmed by conventional methods, contained various VIM-producing species. Future multicenter studies should be considered for the thorough evaluation of this method and its potential diagnostic utility., (Copyright © 2010 Elsevier B.V. All rights reserved.)

In this article, we describe the case of a 49-year-old male gypsy on hemodialysis that was referred to our center due to high fever, breathlessness, and productive cough with bloody sputum. Forty-five days before hospitalization, he was treated for vasculitis with prednisolone and intravenous cyclophosphamide. Soon after admission he was resuscitated and intubated after a cardiac arrest. A large worm load of Strongyloides stercoralis larvae was identified in the sputum. The patient was treated with thiopental 25 mg/kgBW/12 h through a Levine tube and died 24 h later.

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-beta-lactamase (MBL) production was examined by clavulanate- and EDTA-based techniques, respectively. Isolates were typed by PFGE of XbaI-digested genomic DNA. Detection of bla(VIM-1) and mapping of the VIM-1-encoding integrons were performed by PCR and sequencing. Beta-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 bla(VIM-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 bla(VIM-1) and expression of VIM-1 were studied in 12 isolates representing the eight PFGE clusters. In all isolates, bla(VIM-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 bla(VIM-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 bla(VIM-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.

A prospective observational study was conducted to identify factors associated with bloodstream infections (BSIs) caused by integron-carrying Enterobacteriaceae and to evaluate the clinical significance of integron carriage. Consecutive patients with Enterobacteriaceae BSIs were identified and followed up until discharge or death. Identification of blood isolates and susceptibility testing were performed by the Wider I automated system. int-1-specific PCR, conserved-segment PCR, and DNA sequencing were used to determine the presence, length, and content of integrons. The relatedness among the isolates was examined by pulsed-field gel electrophoresis. Two hundred fifty episodes of Enterobacteriaceae BSI occurred in 233 patients; 109 (43.6%) were nosocomial, 82 (32.8%) were community acquired, and 59 (23.6%) were health care associated. Integrons were detected in 11 (13.4%) community-acquired, 24 (40.7%) health care-associated, and 46 (42.2%) nosocomial isolates. Integron-carrying organisms were more likely to exhibit resistance to three or more classes of antimicrobials (odds ratio [OR], 9.84; 95% confidence interval [95% CI], 5.31 to 18.23; P < 0.001) or to produce extended-spectrum beta-lactamases (OR, 5.75; 95% CI, 2.38 to 13.89; P < 0.001) or a VIM-type metallo-beta-lactamase (P, 0.003). Inter- or intraspecies integron transfer and cross-transmission of integron-carrying clones were observed. Use of cotrimoxazole (OR, 4.77; 95% CI, 1.81 to 12.54; P < 0.001) and a nosocomial or other health care setting (OR, 3.07; 95% CI, 1.30 to 7.22; P, 0.01) were independently associated with BSIs caused by integron-carrying Enterobacteriaceae. Patients with a nonurinary source of bacteremia (OR, 9.46; 95% CI, 2.77 to 32.32; P < 0.001) and a Pitt bacteremia score of > or =4 (OR, 23.36; 95% CI, 7.97 to 68.44; P < 0.001) had a significantly higher 14-day mortality rate, whereas integron carriage did not affect clinical outcomes. These findings may have implications affecting antibiotic policies and infection control measures.

The evolution of imipenem disk-diffusion susceptibility results of 2652 strains of Klebsiella pneumoniae and 7596 Escherichia coli isolated during the period 2000-2005 were analysed. Screening for production of metallo-beta-lactamases was performed using the EDTA-synergy method. The percentage rate of K. pneumoniae isolates having a zone diameter < or =25 mm increased from 20% in 2000 to 41% in 2005, whereas the respective rate of isolates having a zone diameter > or =30 mm decreased from 48 to 23%. These changes were more evident during 2000-2002, followed in 2003 by the isolation of the first imipenem-resistant strains. Regarding E. coli, a similar decrease was observed (the rates of isolates having a zone diameter < or =25 mm and > or =30 mm changed from 7% and 68% in 2000, to 32% and 36% in 2005, respectively) following the respective changes of K. pneumoniae. A total of 20 K. pneumoniae strains, but no E. coli, were confirmed as metallo-beta-lactamase producers. In conclusion, a decrease of the imipenem susceptibility prior to the isolation of the first resistant strains in a tertiary care hospital was detected, as well as differences in this decrease between the two species. These findings indicate that monitoring of the evolution of imipenem susceptibility in real-time may help in unveiling forthcoming resistance and in implementing the appropriate diagnostic techniques.

We report a case of septic arthritis due to Roseomonas mucosa in a rheumatoid arthritis patient receiving infliximab therapy. This is the first report of septic arthritis due to R. mucosa, and infliximab therapy might be a predisposing factor because this infection was never reported in the pre-anti-tumor necrosis factor alpha therapy period.

Campylobacter species are well-recognized common causes of gastrointestinal infections. While Campylobacter jejuni is probably the most common Campylobacter isolated in humans, Campylobacter fetus is rather infrequent and mostly related with bacteraemia. Even on such occasions, it seems that immunocompetent individuals are spared. We report a case of C. fetus bacteraemia in a healthy-except for impaired fasting glucose (IFG) levels-farmer, presenting as an acute febrile syndrome and treated successfully as brucellosis.

A total of 1019 non-replicate, consecutively isolated methicillin-resistant Staphylococcus aureus (MRSA) strains were collected from in-patients of a tertiary care general hospital in Athens, Greece, during the period 1994-2001. The susceptibility, resistance phenotypes and the dissemination of these isolates among hospital wards were studied. Total MRSA and gentamicin-resistant MRSA, as a proportion of the S. aureus isolates, increased from 33 and 9% in 1994 to 50.1 and 33.3% in 2001, respectively. Three main multi-resistant phenotypes predominated, representing 50.9% of the total MRSA isolates in 2001. MRSA strains susceptible to all antibiotics tested decreased to 1.9% in 1997 and again increased to 13.5% in 2001. A gradual decrease in the susceptibility of vancomycin during the 8-year-period was detected, but no vancomycin resistant S. aureus strains were isolated.

Intracoronary stenting has been shown to reduce acute closure and restenosis rate in patients treated with coronary angioplasty. The use of high inflation pressures and intravascular ultrasound guidance allowed the substitution of anticoagulants with antiplatelet agents but increased the cost. The aim of this study was to investigate the effectiveness, safety, and long-term outcome of the elective implantation of a relatively new type of stent (Micro-Stent II), without the use of quantitative coronary angiography or intravascular ultrasound guidance and without subsequent anticoagulation. The study included 361 patients who underwent elective microstent implantation. Stent expansion was performed at 8 atm followed by higher inflation pressure at 14-20 atm. Heparin was given intraarterially only once immediately after the arterial sheath insertion. Ticlopidine was started at least 48 hours before the procedure and continued for 1 month while aspirin was continued indefinitely. All patients were followed up for 12.9 +/- 3.6 months. Short term outcome (first month): Stent implantation was successfully achieved in 361 of 366 patients (98.6%). Seven patients (1.9%) were excluded from the study and received anticoagulants because of a suboptimal result. In total, 423 stents were implanted. There was no subacute thrombosis, but acute vessel closure occurred in one patient (0.3%). Non-Q wave myocardial infarction occurred in six patients (1.7%), Q wave myocardial infarction occurred in one patient (0.3%), and only one death (0.3%) of nonischemic origin was reported. No major peripheral vascular complications were observed. Late results: Q or non-Q wave infarction occurred in 13 patients (3.6%), 26 patients (7.2%) underwent a repeat angioplasty, eight patients (2.2%) underwent coronary artery bypass grafting, and four patients (1.1%) died. Overall, 284 patients (78.7%) were free of symptoms, while 77 (21.3%) had recurrent coronary ischemia. In conclusion, Micro-Stent II implantation without quantitative coronary angiography or intravascular ultrasound guidance and without anticoagulation was found to be effective, safe, and with good long-term outcome.

We report the first case of Cryptococcus laurentii meningitis and a rare case of Cryptococcus albidus cryptococcaemia in AIDS patients. Both infections were treated with amphotericin B and flucytosine. The C. laurentii meningitis was controlled after 2 weeks of treatment with no evidence of infection 20 months later. The patient with C. albidus cryptococcaemia, despite the amphotericin B/flucytosine combination therapy, died on the 14th day of treatment. The minimum inhibitory concentrations (MICs) for C. laurentii, as determined by Etest on RPMI 1640 agar, were 0.25 microg ml(-1) of amphotericin B, 1.25 microg ml(-1) flucytosine, 4 microg ml(-1) fluconazole, 0.50 microg ml(-1) itraconazole and 1.0 microg ml(-1) of ketoconazole. The MIC of amphotericin B for C. albidus was 0.5 microg ml(-1), flucytosine 1.25 microg ml(-1), fluzonazole 4 microg ml(-1), itraconazole 0.5 microg ml(-1) and ketonazole 0.25 microg ml(-1). The agreement of the amphotericin B MIC values obtained in antibiotic medium 3 by the broth microdilution method, with those obtained on casitone medium by Etest, was within a two-dilution range for both isolates. C. laurentii may cause meningitis and may also involve the lungs in AIDS patients.

A postanginal Sepsis Syndrome with metastatic lung abscess caused by Fusobacterium necrophorumin a 25-year-old previously healthy man is described. The incomplete and ineffective antibiotic treatment at onset of angina ended progressively in septicaemia and metastatic infections in a 3-week time period. The early parenteral use of Metronidazole based only on the clinical picture, the Gram stain findings and the strict anaerobic feature of the blood isolate in parallel with the long-term antibiotic treatment were possibly the main reasons for the good outcome of this serious infection.