Decomposition of Growth Curves into Growth Rate and Acceleration: a Novel Procedure To Monitor Bacterial Growth and the Time-Dependent Effect of Antimicrobials.

In this paper, a simple numerical procedure is presented to monitor the growth of Streptococcus sanguinis over time in the absence and presence of propolis, a natural antimicrobial. In particular, it is shown that the real-time decomposition of growth curves obtained through optical density measurements into growth rate and acceleration can be a powerful tool to precisely assess a large range of key parameters (i.e., lag time [t0], starting growth rate [γ0], initial acceleration of the growth [a0], maximum growth rate [γmax], maximum acceleration [amax], and deceleration [amin] of the growth and the total number of cells at the beginning of the saturation phase [Ns]) that can be readily used to fully describe growth over time. Consequently, the procedure presented provides precise data of the time course of the different growth phases and features, which is expected to be relevant, for instance, to thoroughly evaluate the effect of new antimicrobial agents. It further provides insight into predictive microbiology, likely having important implications for assumptions adopted in mathematical models to predict the progress of bacterial growth. IMPORTANCE The new and simple numerical procedure presented in this paper to analyze bacterial growth will possibly allow the identification of true differences in efficacy among antimicrobial drugs for their applications in human health, food security, and the environment, among others. It further provides insight into predictive microbiology, likely helping in the development of proper mathematical models to predict the course of bacterial growth under diverse circumstances.

Antimicrobial activity of a novel Spanish propolis against planktonic and sessile oral Streptococcus spp.

Increased bacterial resistance to traditional antimicrobial agents has prompted the use of natural products with antimicrobial properties such as propolis, extensively employed since ancient times. However, the chemical composition of propolis extracts is extremely complex and has been shown to vary depending on the region and season of collection, due to variations in the flora from which the pharmacological substances are obtained, being therefore essential for their antimicrobial activity to be checked before use. For this purpose, we evaluate the in vitro antimicrobial and anti-biofilm activity of a new and promising Spanish ethanolic extract of propolis (SEEP) on Streptococcus mutans and Streptococcus sanguinis, responsible, as dominant 'pioneer' species, for dental plaque. Results reveal that S. sanguinis is more sensitive to SEEP, slowing and retarding its growth considerably with lower concentrations than those needed to produce the same effect in S. mutans. SEEP presents concentration- and time-dependent killing activity and, furthermore, some of the subinhibitory concentrations employed increased biofilm formation even when bacterial growth decreased. Mono and dual-species biofilms were also inhibited by SEEP. Findings obtained clearly show the relevance of using biofilm and subinhibitory concentration models to determine optimal treatment concentrations.

Prognostic role of NYHA class in heart failure patients undergoing primary prevention ICD therapy.

AIMS: Concerns about the prognostic value of NYHA functional class (FC) in heart failure (HF) patients carrying a prophylactic implantable cardioverter defibrillator (ICD) are still present. We aimed to compare whether mortality and arrhythmic risk were different, in a cohort of HF patients undergoing ICD-only implant, according to their FC. METHODS AND RESULTS: HF patients with left ventricle ejection fraction (LVEF) ≤35%, undergoing first prophylactic ICD-only implant were collected from a multicentre nationwide registry (2006-2015). Six hundred and twenty-one patients were identified (101 patients in NYHA I; 411 in NYHA II; 109 in NYHA III). After a mean follow-up of 4.4 years (±2.1), 126 patients died (20.3%). All-cause mortality risk was higher in symptomatic patients: 13.9% in NYHA I patients, 18.3% in NYHA II patients (HR: 1.8, 95% CI 1.1-3.2), and 32.9% in NYHA III patients (HR: 3.9, 95% CI 2.1-7.3). Seventy-eight out of all deaths were due to cardiovascular causes (12.6%). Cardiovascular mortality risk was also higher in symptomatic patients: 6.9% in NYHA I patients, 11% in NYHA II patients (HR: 2.2, 95% CI 1.1-4.9), and 23.9% in NYHA III (HR: 5.5, 95% CI 2.4-12.7). One hundred and seventeen patients received a first appropriate ICD therapy (19.4%). Arrhythmia free survival did not differ among study groups [20.8% in NYHA I patients, 18.7% in NYHA II (HR: 1.1, 95% CI 0.6-1.7) and 20.8% in NYHA III patients (HR: 1.3, 95% CI 0.7-2.5)]. NYHA class independently predicted cardiovascular mortality (NYHA III vs. NYHA I: HR, 4.7; 95% CI, 1.7-12.8, P = 0.002; NYHA II vs. NYHA I: HR, 2.1, 95% CI, 1.0-5.6, P = 0.05) but not all-cause death (NYHA III vs. NYHA I: HR: 1.8, 95% CI 0.8-3.9, P = 0.11; NYHA II vs. NYHA I: HR, 1.1, 95% CI 0.6-2.2, P = 0.71;). Atrial fibrillation, chronic kidney disease, and diabetes emerged as predictors of both all-cause death [(HR: 1.8, 95% CI 1.2-2.8, P = 0.005), (HR: 2.2, 95% CI 1.4-3.4, P < 0.001), (HR: 2.0, 95% CI 1.3-3.1, P = 0.001), respectively] and cardiovascular mortality [(HR: 1.8, 95% CI 1.1-3.1, P = 0.02), (HR: 3.1, 95% CI 1.8-5.4, P < 0.001), (HR: 1.7, 95% CI 1.1-3, P = 0.032), respectively]. CONCLUSIONS: Mortality in HF patients undergoing prophylactic ICD implantation was higher in symptomatic patients. NYHA functional class along with other comorbidities might be helpful to identify a subgroup of ICD carriers with poorer prognosis and higher risk of cardiovascular death.

Single-brand dual-chamber discriminators to prevent inappropriate shocks in patients implanted with prophylactic implantable cardioverter defibrillators: a propensity-weighted comparison of single- and dual-chamber devices.

PURPOSE: Comparisons of the efficacy of dual- vs. single-chamber implantable cardioverter defibrillators (ICDs) in preventing inappropriate shocks have had contradictory results. We investigated whether dual-chamber devices have a lower risk of inappropriate shocks and the specific role of supraventricular tachycardia (SVT) discriminators. METHODS: All heart failure (HF) patients without an indication for pacing and implanted with a prophylactic ICD were recruited from the nationwide multicenter UMBRELLA registry. Arrhythmic events were collected by remote monitoring and reviewed by a committee of experts. RESULTS: Among 782 patients, single-chamber ICDs were implanted in 537 (68.7%) and dual-chamber devices in 245 (31.3%). During a mean follow-up of 52.2 ± 24.5 months, 109 inappropriate shocks were delivered in 49 patients (6.2%). In the propensity-score-matched analysis, dual-chamber ICDs were related to lower rates of inappropriate shocks as compared to single-chamber devices (0.9% vs. 11.8%, p = < 0.001, log-rank test). In multivariable Cox proportional analysis, independent predictors of inappropriate shock were history of atrial fibrillation (hazard ratio (HR) = 2.78, CI 1.37-5.64, p = 0.004), chronic kidney disease (HR = 6.15, CI 2.82-13.53, p < 0.001), and non-ischemic cardiomyopathy (HR = 2.84, CI 1.54-5.23, p = 0.001). Among ICD settings, PR logic was the only discriminator independently related to a reduced risk of inappropriate shocks (HR = 0.18, CI 0.06-0.48, p = 0.001), along with an SVT limit enabled over 200 bpm (HR = 0.24, CI 0.11-0.51, p < 0.001). CONCLUSIONS: In this nationwide cohort of primary prevention ICD-only patients, dual-chamber devices were related to lower risk of inappropriate shocks compared to single-chamber ICDs. Besides, PR logic and SVT limit > 200 bpm emerged as protective factors.

Multidimensional psychosocial profiles in the elderly and happiness: a cluster-based identification.

OBJECTIVES: Evidence supports that subjective well-being (SWB) diminishes in the old age and that this decline is strongly determined by elders' psychosocial resources. This study explored person-centred, multidimensional, empirically-derived profiles of psychosocial functioning in the elderly and related each trajectory to differing configurations of SWB. METHOD: A community-based, convenience sample of Spanish institutionalised and non-institutionalised elders voluntarily participated in this cross-sectional study. RESULTS: A cluster analysis produced three within-person psychosocial profiles characterised by distinct patterns of functioning: highly successful elders demonstrated to be healthy, highly confident in their own resources and very active in daily life; moderately successful elders demonstrated average functioning across domains, although they expected decreases in the future; and highly impaired elders were ill and stressed, at a high risk for future health problems and depression, and tried to compensate for their status mainly through social support. Each of these profiles was related differently to SWB configurations: highly successful elders demonstrated significantly higher happiness, positive affect, affect balance and life satisfaction; moderately successful elders showed average levels of SWB but decreased positive affect; and highly impaired elders demonstrated dramatically lower SWB. Furthermore, such trajectories were associated with the elders' living condition. The happiest elders were more likely to be home-dwelling elders; however, there were fewer unhappy elders among those who were institutionalised. CONCLUSION: A person-centred approach to assessing psychosocial and SWB configurations provides a rich picture of individual differences in the ageing processes and can help in designing interventions aimed at enhancing happiness in old age.

Insights into bacterial contact angles: difficulties in defining hydrophobicity and surface Gibbs energy.

One of the principal techniques for evaluating the surface hydrophobicity of biological samples is contact angle. This method, applied readily to flat-smooth-inert surfaces, gives rise to an important debate when implemented with microbial lawns. After its initial description, in 1984, several authors have carried out modifications of the technique but the results obtained have not been previously judged. This work focuses on the particularities of contact angle measurements on bacterial lawns and enhances the idea of the impossibility of using water contact angle as a universal measurement of bacterial hydrophobicity. Contact angles can only be used as relative indicators of hydrophobicity, in a similar way to tests based on microbial adhesion to solvents. The strong dependence of contact angles on dried bacterial lawns with measuring time and environmental conditions (e.g. pH of the media) preclude the estimation of their absolute values, and so, of the cells surface Gibbs energy. Yet, for a given measuring time, it is found that the hydrophobicity and the apparent bacterial surface Gibbs energy components are qualitatively related to the bacterial surface electrical potential. In particular, a hydrophobic increase is always accompanied by an increase of the cells Lifshitz-Van der Waals component and a decrease of their acid-base component and absolute zeta potential. Therefore, the present study shows that the physico-chemical surface properties that characterize bacteria are not independent, and one of them can be qualitatively described in terms of the others when measuring contact angles at a fixed time after the drying of the microbial beds.