Bioactive peptides from Tenebrio molitor: physicochemical and antioxidant properties and antimicrobial capacity.

Recent research has demonstrated the increasing interest in using insects for the extraction of bioactive compounds, particularly peptides. These compounds offer a spectrum of beneficial physiological effects. The aim of this study was to standardize a methodology for obtaining bioactive peptides from Tenebrio molitor and evaluate its physicochemical characterization, antioxidant, and antimicrobial potential. Six assays were carried out to hydrolyse larvae protein, with variations in Alcalase concentration (0.04 to 0.08%) and reaction time (3 to 8 h). The results indicated that the process applied to defatted mealworm flour was effective in reducing lipids by 82.5%. Consequently, it was an observed increase of 38.4% in protein content. Additionally, an increase in glycogen content was found in defatted mealworm flour (177 µmol glucose g-1 sample) and peptides (152.81 µmol glucose g-1 sample). The degree of hydrolysis was higher in assays with longer hydrolysis durations (8.14 - 8.38%). The antioxidant capacity was 12 to 14% lower in assays with an incubation time of 8h. In this sense, the methodology proposed in the present study proved to be efficient in obtaining bioactive peptides from T. molitor.

In vitro activity of polymyxin B plus imipenem, meropenem, or tigecycline against KPC-2-producing Enterobacteriaceae with high MICs for these antimicrobials.

We evaluated the in vitro activity of polymyxin B plus imipenem, meropenem, or tigecycline against six KPC-2-producing Enterobacteriaceae strains with high MICs for these antimicrobial agents. Polymyxin B with carbapenems, especially meropenem, were the most active combinations for Klebsiella pneumoniae and Enterobacter cloacae regardless of the polymyxin B concentration used in the time-kill assay. This combination was also synergistic against two Serratia marcescens strains that are intrinsically resistant to polymyxins. Polymyxin B and tigecycline also presented synergistic activity in most experiments.

Emergence of NDM-1-producing Enterobacteriaceae in Porto Alegre, Brazil.

OBJECTIVES: To evaluate the emergence of New Delhi metallo-ß-lactamase 1 (NDM-1)-producing Enterobacteriaceae isolates in Brazil. METHODS: From April to October 2013, following the detection of the first NDM-1-producing isolate, a surveillance study was performed for the detection of blaNDM-1 among Enterobacteriaceae isolates with reduced susceptibility to carbapenems in 17 hospitals of Porto Alegre, Brazil. Real-time PCR was used to determine the presence of carbapenemase genes, which were further sequenced. Clonal relatedness was assessed by pulsed-field gel electrophoresis (PFGE). RESULTS: A total of 1134 isolates were evaluated. blaNDM-1 was detected in 11 (0.97%) isolates: nine Enterobacter cloacae complex (eight belonging to a single clone recovered from two distinct hospitals and the other strain from a third hospital) and two Morganella morganii (belonging to a single clone recovered from one hospital). Most isolates presented high-level resistance to carbapenems. CONCLUSIONS: NDM-1-producing Enterobacteriaceae have emerged rapidly in the hospitals of the Brazilian city where they were first detected. The emergence of NDM-1 in Brazil is of great concern, since it is a severe threat to antimicrobial therapy against Enterobacteriaceae in this country.

Effect of cefepime dose on mortality of patients with Gram-negative bacterial bloodstream infections: a prospective cohort study.

OBJECTIVES: There are controversies regarding the association of cefepime therapy with increased mortality among patients with infections caused by Gram-negative bacteria (GNB). We evaluated the effect of cefepime on the mortality of patients with GNB bloodstream infections (BSIs). METHODS: A prospective cohort study was conducted in adult patients with creatinine ≤1.5 mg/dL who received empirical therapy with cefepime for at least 48 h for BSIs caused by GNB. The outcome was hospital mortality. Potential clinical predictors, including a high-dose regimen (2 g every 8 h), were assessed. RESULTS: One hundred and thirteen patients were included. Most (78.8%) isolates had low cefepime MICs (≤0.25 mg/L). The overall hospital mortality was 35.4% [25.6% (10/39) and 40.5% (30/74) in patients receiving high-dose and usual-dose cefepime, respectively (P = 0.17)]. In a Cox regression model adjusted for cefepime MIC and propensity score, a high-dose regimen was independently associated with lower mortality rates [adjusted hazard ratio (aHR) 0.41; 95% CI 0.18-0.91; P = 0.029] while presentation with severe sepsis or septic shock was independently associated with higher mortality rates (aHR 4.10; 95% CI 1.78-9.40; P = 0.001). A trend to lower mortality rates was also found in the subgroup analysis of patients who had not switched antibiotic during therapy after adjustment for the latter variables. CONCLUSIONS: High-dose cefepime therapy was associated with lower mortality rates in patients with GNB BSIs, even for GNB with low cefepime MICs.

Evaluation of heteroresistance to polymyxin B among carbapenem-susceptible and -resistant Pseudomonas aeruginosa.

One hundred and twenty-four Pseudomonas aeruginosa isolates were selected for antimicrobial susceptibility testing with anti-pseudomonal agents, MIC determination for polymyxin B and metallo-beta-lactamase detection (genes blaSPM, blaVIM-1, blaNDM-1 and blaIMP). According to the imipenem and/or meropenem susceptibility profile, a set of randomly selected isolates (12 isolates carbapenem-susceptible and 12 isolates carbapenem-resistant) were evaluated for heteroresistance to polymyxin B. Heteroresistance testing was performed by plating the isolates onto increasing concentrations of polymyxin B (from 0 to 8.0 mg l(-1)). The population analysis profile (PAP) was defined as the ratio of the number of colony-forming units on the plate with the highest concentration of polymyxin B at which bacterial growth occurred against the number of colony-forming units on the plate without antibiotic. Isolates presenting subpopulations that exhibited growth at polymyxin B concentrations ≥2 mg l(-1) were considered heteroresistant. Isolates containing subpopulations that grew at polymyxin B concentrations at least twice as high as the original MIC but <2 mg l(-1) were considered heterogeneous. Antimicrobial susceptibility testing results indicated a variable degree of susceptibility: high levels of resistance to gentamicin (30.6 %) and imipenem (29.0 %); low levels of resistance to aztreonam (1.6 %) and ciprofloxacin (4.8 %). All isolates were susceptible to polymyxin B: MIC50 and MIC90 were 1 mg l(-1) and 2 mg l(-1), respectively. Thirty-seven isolates (30 %) were carbapenem-resistant. Four isolates resistant to carbapenems were positive for blaIMP. There were no heteroresistant subpopulations in the carbapenem-susceptible group, but three isolates presented heterogeneous subpopulations. The PAP frequency ranged from 2.1×10(-4) to 6.9×10(-8). In the carbapenem-resistant group, one isolate was heteroresistant. Six isolates in this group presented heterogeneous subpopulations. In the resistant population, the PAP frequency ranged from 2.1×10(-7) to 2.6×10(-4). In this study, polymyxin B heteroresistance in P. aeruginosa was uncommon and occurred in only one carbapenem-resistant isolate, despite the fact that several isolates presented heterogeneous subpopulations with increased polymyxin B MICs.

Nucleotide metabolizing ecto-enzymes in Walker 256 tumor cells: molecular identification, kinetic characterization and biochemical properties.

In this study we describe the molecular identification, kinetic characterization and biochemical properties of an E-NTPDase and an 5'-nucleotidase in Walker 256 cells. For the ATP, ADP and AMP hydrolysis there were optimum pH in the range 6.5-8.0, and absolute requirement for divalent cations (Mg(2+)>Ca(2+)). A significant inhibition of ATP and ADP hydrolysis was observed in the presence of high concentrations of sodium azide and 0.5 mM of Gadolinium chloride. These activities were insensitive to ATPase, adenylate kinase and alkaline phosphatase classical inhibitors. The K(m) values were 464.2+/-86.6 microM (mean+/-SEM, n=4), 137.0+/-31 microM (mean+/-SEM, n=5) and 44.8+/-10.2 microM (mean+/-SEM, n=4), and V(max) values were 655.0+/-94.6 (mean+/-SEM, n=4), 236.3+/-27.2 (mean+/-SEM, n=5) and 177.6+/-13.8 (mean+/-SEM, n=5) nmol of inorganic phosphate min(-1) mg of protein(-1) for ATP, ADP and AMP, respectively. Using RT-PCR analysis we identified the mRNA of two members of the ecto-nucleoside triphosphate diphosphohydrolase family (NTPDase 2 and 5) and a 5'-nucleotidase. The presence of NTPDases and 5'-nucleotidase enzymes in Walker 256 tumor cells may be important to regulate the ratio adenine nucleotides/adenine nucleoside extracellularly, therefore motivating tumor growth.

Diminution in adenine nucleotide hydrolysis by platelets and serum from rats submitted to Walker 256 tumour.

Extracellular adenine nucleotide hydrolysis in the circulation is mediated by the action of an NTPDase (CD39, apyrase) and of a 5'-nucleotidase (CD73), presenting as a final product, adenosine. Among other properties described for adenine nucleotides, an anti-cancer activity is suggested, since ATP is considered a cytotoxic molecule in several tumour cell systems. Conversely, some studies demonstrate that adenosine presents a tumour-promoting activity. In this study, we evaluated the pattern of adenine nucleotide hydrolysis by serum and platelets from rats submitted to the Walker 256 tumour model. Extracellular adenine nucleotide hydrolysis by blood serum and platelets obtained from rats at, 6, 10 and 15 days after the subcutaneous Walker 256 tumour inoculation, was evaluated. Our results demonstrate a significant reduction in ATP, ADP and AMP hydrolysis in blood serum at 6, 10 and 15 days after tumour induction. In platelets, a significant reduction in ATP and AMP hydrolysis was observed at 10 and 15 days after tumour induction, while an inhibition of ADP hydrolysis was observed at all times studied. Based on these results, it is possible to suggest a physiologic protection mechanism against the tumoral process in circulation. The inhibition in nucleotide hydrolysis observed probably maintains ATP levels elevated (cytotoxic compound) and, at the same time, reduces the adenosine production (tumour-promoting molecule) in the circulation.

Acetylsalicylic acid inhibits ATP diphosphohydrolase activity by platelets from adult rats.

BACKGROUND AND METHODS: The in vitro effect of the nonsteroidal anti-inflammatory drug, acetylsalicylic acid (ASA), on the extracellular adenine nucleotide hydrolysis by intact rat blood platelets was studied. RESULTS: Our results demonstrate that aspirin, at final concentrations of 2.0 and 3.0 mM, inhibits ATP extracellular hydrolysis in vitro by approximately 17% and 21%, respectively. Aspirin, at a final concentration of 3.0 mM, also inhibited in vitro extracellular ADP hydrolysis by approximately 41%. The same concentrations of this drug, however, did not alter AMP hydrolysis by intact rat blood platelets under similar assay conditions. The kinetic analysis demonstrated that the inhibition of ADP and ATP hydrolysis by aspirin in rat platelets is of the uncompetitive type. CONCLUSION: In this study, we demonstrated an inhibitory effect of ASA upon E-NTPDase 3 activity of platelets from adult rats and discussed the significance of our findings.