Antimicrobial activity of the synthetic peptide Lys-a1 against oral streptococci

The peptide LYS-[TRP6]-Hy-A1 (Lys-a1) is a synthetic derivative of the peptide Hy-A1, initially isolated from the frog species Hypsiboas albopunctatus. According to previous research, it is a molecule with broad antimicrobial activity. The objective of this study was to evaluate the antimicrobial activity of the synthetic peptide Lys-a1 (KIFGAIWPLALGALKNLIK- NH2) on the planktonic and biofilm growth of oral bacteria. The methods used to evaluate antimicrobial activity include the following: determination of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) in microtiter plates for growth in suspension and quantification of biomass by crystal violet staining and counting of colony forming units for biofilm growth. The microorganisms Streptococcus oralis, Streptococcus sanguinis, Streptococcus parasanguinis, Streptococcus salivarius, Streptococcus mutans and Streptococcus sobrinus were grown in Brain Heart Infusion broth at 37 °C under atmospheric pressure with 10% CO2. The peptide was solubilized in 0.1% acetic acid (v/v) at various concentrations (500-1.9 μg mL-1). Chlorhexidine gluconate 0.12% was used as the positive control, and BHI culture medium was used as the negative control. The tested peptide demonstrated a remarkable antimicrobial effect, inhibiting the planktonic and biofilm growth of all strains tested, even at low concentrations. Thus, the peptide Lys-a1 is an important source for potential antimicrobial agents, especially for the control and prevention of microbial biofilms, which is one of the most important factors in cariogenic processes. © 2012 Elsevier Inc.

Dynamics and Conformational Studies of TOAC Spin Labeled Analogues of Ctx(Ile21)-Ha Peptide from Hypsiboas albopunctatus

Antimicrobial peptides (AMPs) isolated from several organisms have been receiving much attention due to some specific features that allow them to interact with, bind to, and disrupt cell membranes. The aim of this paper was to study the interactions between a membrane mimetic and the cationic AMP Ctx(Ile21)-Ha as well as analogues containing the paramagnetic amino acid 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid (TOAC) incorporated at residue positions n = 0, 2, and 13. Circular dichroism studies showed that the peptides, except for [TOAC13]Ctx(Ile21)-Ha, are unstructured in aqueous solution but acquire different amounts of α-helical secondary structure in the presence of trifluorethanol and lysophosphocholine micelles. Fluorescence experiments indicated that all peptides were able to interact with LPC micelles. In addition, Ctx(Ile21)-Ha and [TOAC13]Ctx(Ile21)-Ha peptides presented similar water accessibility for the Trp residue located near the N-terminal sequence. Electron spin resonance experiments showed two spectral components for [TOAC0]Ctx(Ile21)-Ha, which are most likely due to two membrane-bound peptide conformations. In contrast, TOAC2 and TOAC13 derivatives presented a single spectral component corresponding to a strong immobilization of the probe. Thus, our findings allowed the description of the peptide topology in the membrane mimetic, where the N-terminal region is in dynamic equilibrium between an ordered, membrane-bound conformation and a disordered, mobile conformation; position 2 is most likely situated in the lipid polar head group region, and residue 13 is fully inserted into the hydrophobic core of the membrane. © 2013 Vicente et al.

Dimerization of aurein 1.2: Effects in structure, antimicrobial activity and aggregation of Cândida albicans cells

Antimicrobial peptides (AMPs) are a promising solution to face the antibiotic-resistant problem because they display little or no resistance effects. Dimeric analogues of select AMPs have shown pharmacotechnical advantages, making these molecules promising candidates for the development of novel antibiotic agents. Here, we evaluate the effects of dimerization on the structure and biological activity of the AMP aurein 1.2 (AU). AU and the C- and N-terminal dimers, (AU)2K and E(AU)2, respectively, were synthesized by solid-phase peptide synthesis. Circular dichroism spectra indicated that E(AU)2 has a coiled coil structure in water while (AU)2K has an α-helix structure. In contrast, AU displayed typical spectra for disordered structures. In LPC micelles, all peptides acquired a high amount of α-helix structure. Hemolytic and vesicle permeabilization assays showed that AU has a concentration dependence activity, while this effect was less pronounced for dimeric versions, suggesting that dimerization may change the mechanism of action of AU. Notably, the antimicrobial activity against bacteria and yeast decreased with dimerization. However, dimeric peptides promoted the aggregation of C. albicans. The ability to aggregate yeast cells makes dimeric versions of AU attractive candidates to inhibit the adhesion of C. albicans to biological targets and medical devices, preventing disease caused by this fungus. © 2013 Springer-Verlag Wien.

Antibiotic 26-deoxylaidlomycin isolated from Streptomyces sp. Ar386 from Brazilian soil

An actinomycete strain (Ar386) was isolated from the soil of the Araraquara regio, SP, Brazil. The strain, named Streptomyces jacareensis, formed irregular rayed, rugose, grayish-white mycelium with sinuous, branched hyphae carrying rare isolated spores; assimilated glucose, galactose, inositol, ribose, maltose, sucrose, melibiose and starch but not mannitol, rhamnose, arabinose, xylose, lactose and raffinose; and contained LL- diaminopimelic acid in its cell wall. An antibiotic active against Gram- positive bacteria, which was characterized as being 26-deoxylaidlomycin and which may have application against poultry coccidiosis, was isolated from cultures of the strain. This was the first isolation of this antibiotic from a microorganism of the genus Streptomyces and also the first isolation of this antibiotic in Brazil.

Re-evaluation of antibiotic and mercury resistance in Escherichia coli populations isolated in 1978 from Amazonian rubber tree tappers and Indians

A study was carried out to assess the stability of antimicrobial susceptibility of wild isolates upon long-term storage using fifty-three Escherichia coli strains isolated in 1978 from feces of healthy children from the Amazon region in Brazil, exposed to low levels of antimicrobial agents, and examined for resistance to mercury and four antibiotics. All of the strains were kept in Lignieres medium at room temperature and were transferred to fresh media four times during this period. Thirty-five out of the 53 strains analyzed in 1978 were viable. Upon recovery, antibiotic and mercury resistance was estimated. All of the 35 strains maintained their original phenotype in a stable fashion, except for one multiresistant strain which became susceptible to kanamycin. Fifty-four percent of the strains exhibited a resistance phenotype, among which 47% had conjugative plasmids.

Resistance to colistin : what is the fate for this antibiotic in pig production?

Colistin, a cationic polypeptide antibiotic, has reappeared in human medicine as a last-line treatment option for multidrug-resistant Gram-negative bacteria (MDR-GNB). Colistin is widely used in veterinary medicine for the treatment of gastrointestinal infections caused by Enterobacteriaceae. GNB resistant to colistin owing to chromosomal mutations have already been reported both in human and veterinary medicine, however several recent studies have just identified a plasmid-mediated mcr-1 gene encoding for colistin resistance in Escherichia coli colistin resistance. The discovery of a non-chromosomal mechanism of colistin resistance in E. coli has led to strong reactions in the scientific community and to concern among physicians and veterinarians. Colistin use in food animals and particularly in pig production has been singled out as responsible for the emergence of colistin resistance. The present review will focus mainly on the possible link between colistin use in pigs and the spread of colistin resistance in Enterobacteriaceae. First we demonstrate a possible link between Enterobacteriaceae resistance emergence and oral colistin pharmacokinetics/pharmacodynamics and its administration modalities in pigs. We then discuss the potential impact of colistin use in pigs on public health with respect to resistance. We believe that colistin use in pig production should be re-evaluated and its dosing and usage optimised. Moreover, the search for competitive alternatives to using colistin with swine is of paramount importance to preserve the effectiveness of this antibiotic for the treatment of MDR-GNB infections in human medicine.

Resistance to colistin : what is the fate for this antibiotic in pig production?

Colistin, a cationic polypeptide antibiotic, has reappeared in human medicine as a last-line treatment option for multidrug-resistant Gram-negative bacteria (MDR-GNB). Colistin is widely used in veterinary medicine for the treatment of gastrointestinal infections caused by Enterobacteriaceae. GNB resistant to colistin owing to chromosomal mutations have already been reported both in human and veterinary medicine, however several recent studies have just identified a plasmid-mediated mcr-1 gene encoding for colistin resistance in Escherichia coli colistin resistance. The discovery of a non-chromosomal mechanism of colistin resistance in E. coli has led to strong reactions in the scientific community and to concern among physicians and veterinarians. Colistin use in food animals and particularly in pig production has been singled out as responsible for the emergence of colistin resistance. The present review will focus mainly on the possible link between colistin use in pigs and the spread of colistin resistance in Enterobacteriaceae. First we demonstrate a possible link between Enterobacteriaceae resistance emergence and oral colistin pharmacokinetics/pharmacodynamics and its administration modalities in pigs. We then discuss the potential impact of colistin use in pigs on public health with respect to resistance. We believe that colistin use in pig production should be re-evaluated and its dosing and usage optimised. Moreover, the search for competitive alternatives to using colistin with swine is of paramount importance to preserve the effectiveness of this antibiotic for the treatment of MDR-GNB infections in human medicine.

Frequent accesses to totally implanted vascular ports in pediatric oncology patients are associated with higher infection rates.

PURPOSE: Totally implanted vascular (TIVA) ports are used in children for repeated blood samples or intravenous treatments. We have recently published a prospective evaluation of surgical incidents and early complications associated with these devices. This work is the final part of the same study, assessing late complications over a follow-up of 2 yrs. METHODS: From January 2006 to January 2008, children older than 1 yr of age with a diagnosis of solid or blood cell malignancy were included. Insertion technique and care of the device were standardized. Every manipulation was prospectively recorded by specialized nurses. Obstruction was documented clinically. When bacteremia was suspected, routine central and peripheral blood cultures were drawn. RESULTS: Forty-five consecutive patients were enrolled in the study. Mean age at the time of the procedure was 8.5 yrs. There was no catheter-related infection within the first 4 weeks post-surgery. No device had to be removed because of infection or obstruction during follow-up. Frequent accesses to the port (=3 per day over a 10-day period) were associated with an 8-fold risk of infection. CONCLUSION: Insertion and use of TIVA devices were frequently associated with complications. No device had to be removed because of infection or obstruction over the follow-up period, although no prophylactic antibiotic agent was used. Restrictive use of antibiotics may prevent opportunistic infection. Frequent access to the device was significantly associated with line infection (odds ratio=8.43). No risk factor was identified for obstruction which occurred at a rate of 5.3 per 10,000 accesses.

The influence of crystallization conditions on the filtration characteristics of sulphathiazole suspensions

Cooling crystallization is one of the most important purification and separation techniques in the chemical and pharmaceutical industry. The product of the cooling crystallization process is always a suspension that contains both the mother liquor and the product crystals, and therefore the first process step following crystallization is usually solid-liquid separation. The properties of the produced crystals, such as their size and shape, can be affected by modifying the conditions during the crystallization process. The filtration characteristics of solid/liquid suspensions, on the other hand, are strongly influenced by the particle properties, as well as the properties of the liquid phase. It is thus obvious that the effect of the changes made to the crystallization parameters can also be seen in the course of the filtration process. Although the relationship between crystallization and filtration is widely recognized, the number of publications where these unit operations have been considered in the same context seems to be surprisingly small. This thesis explores the influence of different crystallization parameters in an unseeded batch cooling crystallization process on the external appearance of the product crystals and on the pressure filtration characteristics of the obtained product suspensions. Crystallization experiments are performed by crystallizing sulphathiazole (C9H9N3O2S2), which is a wellknown antibiotic agent, from different mixtures of water and n-propanol in an unseeded batch crystallizer. The different crystallization parameters that are studied are the composition of the solvent, the cooling rate during the crystallization experiments carried out by using a constant cooling rate throughout the whole batch, the cooling profile, as well as the mixing intensity during the batch. The obtained crystals are characterized by using an automated image analyzer and the crystals are separated from the solvent through constant pressure batch filtration experiments. Separation characteristics of the suspensions are described by means of average specific cake resistance and average filter cake porosity, and the compressibilities of the cakes are also determined. The results show that fairly large differences can be observed between the size and shape of the crystals, and it is also shown experimentally that the changes in the crystal size and shape have a direct impact on the pressure filtration characteristics of the crystal suspensions. The experimental results are utilized to create a procedure that can be used for estimating the filtration characteristics of solid-liquid suspensions according to the particle size and shape data obtained by image analysis. Multilinear partial least squares regression (N-PLS) models are created between the filtration parameters and the particle size and shape data, and the results presented in this thesis show that relatively obvious correlations can be detected with the obtained models.

CAMPYLOBACTER EM CAES COM E SEM DIARREIA: INCIDENCIA E SUSCETIBILIDADE A 21 ANTIMICROBIANOS

Two hundred and four stools of 102 diarrheic (0-12 months of age) and 102 non-diarrheic dogs coming from kennel and ambulatory, respectively, were assayed for the presence of Campylobacter. From the diarrhetic group, 46% of the samples yelded positive Campylobacter isolation mainly found in young animals until 5 months of age (72%), whereas those with age ranging from 6-12 months showed either a lower frequence of the organisms (28%) and a trend of the younger animals to be more charged than the older. 47 Campylobacter strains isolated from the diarrheic group were: C. jejuni biotype 1 (49%); C. jejuni biotyp 2 (11%); C. jejuni/coli (19%); C. coli (8,5%); Campylobacter NARTC group (8,5%) and C. sputoruns (4%). In the non-diarrhetic group, 27 (28%) Campylobacter strains were classified as: C. jejuni biotype 1 (34%) and biotype 2 (28%); C. jejuni/coli (24%) and C. coli (14%). According the biochemical tests, the 1% glycine tolerance test was not taking in account for the differentiation of C. jejuni because 45% of the strains failed in showing characteristic and 3 strains did not reduce the sodium selenite. The biochemical studies also showed phenotipical cross reactions between two Campylobacter NARTC-group strains with the C. jejuni strains, as well as two thermophilic species grew also at 25°C. All the 76 isolates were sensitive to gentamicin, nitrofurantoin and neomycin and resistant to oxacillin and penicillin. Furthermore, for the remaining 16 drugs the populational resistance ranged from 8% to 73% of strains. The presence of Campylobacter in dogs as well their close contact which man makes possible the occurrence of infections as also confirm the campylobacteriosis as an important zoonosis.

AVALIACAO DO EFEITO DO VENENO DE APIS MELLIFERA EM CULTURAS DE E. COLI, S. TYPHIMURIUM E Y. ENTEROCOLITICA TRATADAS COM BLEOMICINA

Apis mellifera bee venom (Africanized honey bee) was tested for the ability to protect against the lethal effect of bleomycin, an antibiotic and antineoplastic agent. Since the radioprotective effect of the venom has been observed on the other biological systems, in the present study the venom was applied to cultures of enterobacteria treated with bleomycin, a radiomimetic agent. The venom did not act as a protective agent against bleomycin in E. coli, S. typhimurium or Y. enterocolitica.

Estudo sobre a resistencia aos antimicrobianos em bacterias isoladas de pacientes hospitalizados (Botucatu, 1988-1992)

Since 1988 to 1992, a study about susceptibility to antimicrobial drugs of bacterias isolated from hospitalized patients was performed. The compared susceptibility to important drugs (ampicillin, cephalotin, cefoxitin, ceftaxizime, ceftriaxone, aztreonam, gentamicin, amikacin, pefloxacin, ciprofloxacin, imipenem, oxacillin and vancomycin) was investigated in 1200 strains (300 of each specie) of the prevalent bacterias: E. coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and S. aureus. Minimal inhibitory concentration (MIC) was determined by agar dilution method, using from 0.05 to 256 mcg of each drug per ml of culture medium (Mueller-Hinton). Ranges of MIC, MIC(50%), MIC(90%) and the proportion of resistant strains were determined and permitted to know the 4 drugs that were found to be more active against bacterias; the CIM(90%) values are: E. coli - aztreonam (0.1 mcg/ml), pefloxacin (0.1), ceftazidime (0.25) and ceftriaxone (0.05); K. pneumoniae-aztreonam (0.25) ceftriaxone (0.25), ceftazidime (0.5) and pefloxacin (2.0); P. aeruginosa-imipenem (4.0), aztreonam (16), ceftazidime (16) and ciprofloxacin (16); S. aureus-vancomycin (1.01, ciprofloxacin (8, 0), amikacin (128) and cephalothin (128 mg/ml). The better 'in vitro' antibacterial activity observed was related to: aztreonam (77-100% of the sensitive strains), ceftazidime (50-99,7%), pefloxacin (73-99,7%), ciprofloxacin (80%), imipenem (93%) and vancomycin (100%).

FATORES RELACIONADOS COM A OCORRENCIA E EVOLUCAO DAS ENDOFTALMITES

We retrospectively analysed 33 endophthalmitis patients treated at the Faculdade de Medicina de Botucatu. We observed that 81,8% of these patients were males and older than 60 years. Trauma was the main cause of endophthalmitis (42,4%). Endophthalmitis severity can be assessed by the fact there was no improvement on the final visual acuity.