Higher Antibacterial Effect Research Articles

Insights on the ultra high antibacterial activity of positionally substituted 2'-O-hydroxypropyl trimethyl ammonium chloride chitosan: A joint interaction of -NH2 and -N+(CH3)3 with bacterial cell wall.

The positionally substituted 2'-O-hydroxypropyl trimethyl ammonium chloride chitin (2'-O-HTACCT) with different substitution degree of quaternary ammonium salt were synthesized directly from β-chitin, after that these 2'-O-HTACCT were then deacetylated to obtain corresponding 2'-O-hydroxypropyl trimethyl ammonium chloride chitosan (2'-O-HTACCS) with different deacetylation degree. The antibacterial activity and mechanism against E. coli and S. aureus of these 2'-O-HTACCT and 2'-O-HTACCS were investigated with various techniques. The results demonstrated that the 2'-O-HTACCT had antibacterial effect against S. aureus, but it had negligible antibacterial effect against E. coli, maybe due to the lack of anionic compound such as teichoic acid on the E. coli's cell wall. Impressively, the high antibacterial effect against E. coli of the 2'-O-HTACCS was derived only from its -NH2, but the ultra high antibacterial effect against S. aureus of the 2'-O-HTACCS was derived both from its -NH2 and -N+(CH3)3, and enhanced as its pH value decreased. Thus, the positionally substituted 2'-O-HTACCS played an important role as a high-performance antibacterial bio-resource polymer against E. coli and S. aureus.

A novel hybrid β-chitin/calcium phosphate functionalized with copper nanoparticles for antibacterial applications

In the present work, a newly synthesized hybrid β-chitin/dicalcium phosphate anhydrous (DCPA) loaded with copper nanoparticles Cu(NPs) was investigated as an antibacterial agent using various strains. The hybrid β-chitin/DCPA was obtained via a mechano-chemical route and the Cu(NPs) supported over β-chitin/DCPA matrix was successfully synthesized from Cu(II) ions using the ultrasound-assisted method followed by in situ chemical reduction with sodium borohydride. All the prepared materials were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–vis diffuse reflectance spectroscopy (DRS), simultaneous thermogravimetry/differential thermal analysis (TG/DTA), and scanning electron microscopy (SEM-EDS). The localized surface plasmon resonance (LSPR) of Cu(NPs) after the reduction process was identified by the optical absorption spectroscopy, in the visible light region around 600 nm. The antibacterial activity of Cu-based materials was investigated against series of Gram-positive bacteria (S. aureus, L. monocytogenes) and Gram-negative (E. coli, P. aeruginosa) strains, using the microtitration assay by determining the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). Among the materials tested, Cu(NPs)/β-chitin/DCPA exhibited a high antibacterial effect exceeding CuII-β-chitin/DCPA and many others reported antibacterial agents, with a MIC value of 125 μg.mL−1 (6 μg.mL−1 of copper). The excellent antibacterial result was related to high dispersion properties of the hybrid support (β-chitin/DCPA) which avoid the aggregation of Cu(NPs) via various surface bonds with β-chitin biopolymer. Copper-based materials synthesized here exhibit promising antibacterial activities which can be explored in more details in others bacterial strains.

Enamel Anti-Demineralization Effect of Orthodontic Adhesive Containing Bioactive Glass and Graphene Oxide: An In-Vitro Study.

White spot lesions (WSLs), a side effect of orthodontic treatment, can result in reversible and unaesthetic results. Graphene oxide (GO) with a bioactive glass (BAG) mixture (BAG@GO) was added to Low-Viscosity Transbond XT (LV) in a ratio of 1, 3, and 5%. The composite’s characterization and its physical and biological properties were verified with scanning electron microscopy (SEM) and X-ray diffraction (XRD); its microhardness, shear bond strength (SBS), cell viability, and adhesive remnant index (ARI) were also assessed. Efficiency in reducing WSL was evaluated using antibacterial activity of S. mutans. Anti-demineralization was analyzed using a cycle of the acid-base solution. Adhesives with 3 wt.% or 5 wt.% of BAG@GO showed significant increase in microhardness compared with LV. The sample and LV groups showed no significant differences in SBS or ARI. The cell viability test confirmed that none of the sample groups showed higher toxicity compared to the LV group. Antibacterial activity was higher in the 48-h group than in the 24 h group; the 48 h test showed that BAG@GO had a high antibacterial effect, which was more pronounced in 5 wt.% of BAG@GO. Anti-demineralization effect was higher in the BAG@GO-group than in the LV-group; the higher the BAG@GO concentration, the higher the anti-demineralization effect.

Antibacterial Activity and Cytotoxicity of Betainated Oligochitosane Derivatives

Insolubility of chitosan and oligochitosan in aqueous media above pH 6.2–6.5 and the resulting decreased penetration thorough mucosa restricts significantly their application in biomedical compositions. To create non-cytotoxic chitosan derivatives with a high antibacterial activity in weakly alkaline physiological media, alkali-soluble derivatives of oligochitosan and low-molecular weight chitosan were synthesized by coupling a betaine substituent to the nitrogen atom of glucosamine units. Comparative studies of the pH range of the solubility of these derivatives depending on the chain length and modification degree of oligochitosan with Mw = 9.7 ± 1.7 kDa were carried out. It was found that 12 mol % of betaine substituents was the optimal modification degree ensuring the existence of a single-phase solution of modified oligochitosan (Mw = 2–10 kDa) within the entire pH range. Investigation of the antibacterial activity of betaine derivatives against gram-positive (S. aureus) and gram-negative (E. coli) bacteria revealed their high antibacterial effect in both weakly acidic and weakly alkaline environments. Betaine derivatives were found to be nottoxic towards cow lung epithelial cells (LEC) at concentrations below 2.5 mg/mL. The results obtained seem promising for the application of these derivatives in biomedical compositions.

Photocatalytic Antibacterial Effectiveness of Cu-Doped TiO2 Thin Film Prepared via the Peroxo Sol-Gel Method

Cu-doped titanium dioxide thin films (Cu/TiO2) were prepared on glass substrate via peroxo sol-gel method and dip-coating process with no subsequent calcination process for the degradation of organic dye and use as an antibacterial agent. The as-prepared materials were characterised using transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). For photocatalytic degradation of methylene blue in water, the samples were subjected to Ultraviolet C (UVC) and visible light irradiation. Degraded methylene blue concentration was measured using UV-Vis spectrophotometer. The antibacterial activities of the samples were tested against the gram-negative bacteria Escherichia coli (ATCC25922). Copper species were present in the form of CuO on the surface of modified TiO2 particles, which was confirmed using TEM and XPS. The optimal observed Cu/TiO2 weight ratio of 0.5 represents the highest photocatalytic activities under both UVC and visible light irradiation. Moreover, the same composition remarkably exhibited high antibacterial effectiveness against E. coli after illumination with ultraviolet A. The presence of CuO on TiO2 significantly enhanced photocatalytic activities. Therefore, active Cu-doped TiO2 can be used as a multipurpose coating material.

Microwave-Assisted Green Synthesis of Silver Nanoparticles Using Juglans regia Leaf Extract and Evaluation of Their Physico-Chemical and Antibacterial Properties.

Silver nanoparticles (Ag NPs) were synthesized using Juglans regia (J. regia) leaf extract, as both reducing and stabilizing agents through microwave irradiation method. The effects of a 1% (w/v) amount of leaf extract (0.1–0.9 mL) and an amount of 1 mM AgNO3 solution (15–25 mL) on the broad emission peak (λmax) and concentration of the synthesized Ag NPs solution were investigated using response surface methodology (RSM). Fourier transform infrared analysis indicated the main functional groups existing in the J. regia leaf extract. Dynamic light scattering, UV-Vis spectroscopy and transmission electron microscopy were used to characterize the synthesized Ag NPs. Fabricated Ag NPs with the mean particle size and polydispersity index and maximum concentration and zeta potential of 168 nm, 0.419, 135.16 ppm and −15.6 mV, respectively, were obtained using 0.1 mL of J. regia leaf extract and 15 mL of AgNO3. The antibacterial activity of the fabricated Ag NPs was assessed against both Gram negative (Escherichia coli) and positive (Staphylococcus aureus) bacteria and was found to possess high bactericidal effects.

Imidazole-molecule-capped chitosan–gold nanocomposites with enhanced antimicrobial activity for treating biofilm-related infections

Biofilms that are widely associated with persistent bacterial infections impose a heavy burden on patients primarily due to their formidable resistance to conventional antiseptic drugs and local immune defense. Here, we successfully synthesized functional gold nanocomposites (CS-Au@MMT) by reducing chloroauric acid in the presence of biocompatible chitosan polymers with cationic amine and the small molecule 2-mercapto-1-methylimidazole (MMT). The cationic amine allowed transport of the CS-Au@MMT to the negatively charged sites at the surface of bacterial cells though electrostatic adhesion, with synergistic effects from the gold nanoparticles and MMT then exerting a strong bactericidal effect to inhibit biofilm formation. For established mature biofilms, CS-Au@MMT was able to adhere to the biofilm surface to render nearby bacterial cells inactive, resulting in biofilm rupture. This allowed CS-Au@MMT to penetrate through the biofilm, leading to sustained damage and achieving biofilm elimination. Furthermore, the nanocomposites efficiently inhibited infections induced by mature biofilm in vivo. These findings indicated that the CS-Au@MMT nanocomposites provide ease of synthesis and fabrication, high bactericidal effect, and low toxicity; thus, they show potential as biofilm-disrupting agents for biomedical and industrial applications.

Enhancement of antibacterial effect of quaternary ammonium with inorganic nanosheets against Enterobacter cloacae

To suppress nosocomial infections, numerous studies of quaternary ammonium cations (R4N+) to improve the antibiotic properties have been investigated. However, most of them reported developments of novel organic or polymeric materials with R4N+. To pioneer antibacterial inorganic materials hybridized with R4N+, a colloidal solution of metal oxide nanosheets, which have a small particle size (typically less than 10 nm), is considered to be a suitable option because oxide nanosheets with a negative surface charge strongly interact R4N+. Herein, we demonstrate for the first time that the high antibacterial/bactericidal effects of titanate nanosheets (TNS) adsorbing tetramethylammonium (TMA-TNS) or tetrabultylammonium ions (TBA-TNS). Their antibacterial effects against Enterobacter cloacae were evaluated using a colony forming unit (CFU) counting method. The results showed that the synthesized TNS composites had superior antibacterial and bactericidal effects to those of free R4N+ and TBA-TNS exhibited the strongest effect (69% CFU reduction compared with that of free TBA+ and 98% CFU reduction compared with the control) among the samples examined. Dark incubation was employed to ensure that photocatalytic reaction of semiconducting TNS did not contribute to the process. Compared with TiO2 spherical particles, such high bactericidal effect would be induced by a synergistic function of TBA+ and TNS, which physically damages bacteria due to long hydrophobic alkyl chains and an anisotropic nanocrystalline structure with sharp edges, respectively.

Antimicrobial graphene nanoplatelets coatings for silicone catheters

Silicone rubber (SR) peritoneal dialysis (PD) catheters are prone to bacterial adhesion and biofilm formation, which contributes to development of infection and associated morbidity in PD patients. We herein evaluate whether surface immobilization of graphene nanoplatelets (GNP) provides antimicrobial properties to SR. Dip and spray coating were used to deposit a dispersion containing SR and GNP-M5 or its oxidized form (GNP-M5ox) on the surface of silicone. The antimicrobial effect of GNP exposure and oxidation towards Staphylococcus epidermidis was assessed. GNP was successfully exposed on the surface, and while dipping provided better adhesion of either GNP, spraying resulted in uniform and higher surface coverage. Spraying led to enhanced bacterial adhesion comparing to dip coated and uncoated SR, which are similar. However, independently of the technique, GNP-M5ox coatings induced higher bacterial death. As such, SR/GNP-M5ox coating performed by dipping revealed to be the most promising approach, preserving bacterial adhesion levels of silicone while increasing bacterial death to around 80%.For the first time, graphene-based materials antimicrobial activity was evaluated by quantification of bacterial adhesion and viability. The high antibacterial effect, associated with a stable and cytocompatible coating which does not delaminate from SR surface, demonstrates its potential use in silicone biomedical industry.

Enhanced immune responses and effectiveness of refined outer membrane protein vaccines against Vibrio harveyi in orange-spotted grouper (Epinephelus coioides).

Vibriosis is a severe infection occurring in many commercially important marine fish species. In this study, vaccines containing Vibrio harveyi recombinant outer membrane protein K (rOmpK), outer membrane protein U (rOmpU) and rOmpK-OmpU fusion protein in addition to the metabolizable MontanideTM ISA 763 A VG adjuvant were developed and evaluated in the orange-spotted grouper. The results indicate that recombinant V.harveyi protein-based vaccines resulted in a remarkably higher expression of IL-1β and IL-8 at 24hr, and greater antibody production, as early as 2weeks postimmunization. Notably, enhanced immune responses and significant protective efficacy against V.harveyi infections were observed in the fusion protein vaccine-injected fishes with relative per cent survival value of 81.8%. Additionally, the rOmpK-OmpU antisera presented a high bactericidal effect on not only V.harveyi, but also Vibrio parahaermolyticus and Vibrio alginolyticus. Our results demonstrated that the fusion protein rOmpK-OmpU was an effective vaccine candidate that exhibited potentially great versatility for controlling vibrio infections.

Corrosion and antibacterial characterization of Ag‐DLC coatingon a new CoCrNbMoZr dental alloy

The paper aim is to compare corrosion and antibacterial characterization of a new CoCrNbMoZr alloy before and after coating with diamond‐like carbon‐Ag (Ag‐DLC) compound films. The investigation of chemical structure of the deposited coating was undertaken using FTIR analysis. Surface characterization involved scanning electronic microscopy (SEM) with X rays energy dispersive analysis (EDX) investigations as well as contact angle measurements. Electrochemical stability tested in Tani–Zuchi saliva and simulated body fluid is higher compared to bare alloy in both bioliquids. Using Staphylococcus aureus and Pseudomonas aeruginosa as model for Gram positive and Gram negative bacteria, respectively, an antibacterial effect of the coated alloy was found. The coating exibited a more hydrophilic character compared to the uncoated alloy and a higher antibacterial effect, the most significant being for S. aureus. Based on experimental data was established the dual potential of Ag‐DLC coating with the capacity to enhance corrosion resistance and bacterial inhibition towards P. aeruginosa and S. aureus in the oral cavity.

Synthesis and evaluation of layered double hydroxide/doxycycline and cobalt ferrite/chitosan nanohybrid efficacy on gram positive and gram negative bacteria

The current study tested the antibacterial activity of layered double hydroxide (LDH), LDH-Doxycycline nanohybrid, Cobalt ferrite nanoparticles (NPs) and Cobalt ferrite-Chitosan nanohybrid against Gram-negative bacteria Escherichia coli. In addition, the study investigated the Cobalt ferrite NPs and Cobalt ferrite-Chitosan nanohybrids against Gram-positive bacteria Staphylococcus aureus. The nanoparticles and nanohybrids were synthesized by a chemical method and characterized by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), and Fourier transformation Infra-red Spectroscopy (FTIR). Multi-point Brunauer–Emmet–Teller (BET) method determined the specific surface area while Barrett-Joyner-Halenda for (BJH) figured the corresponding specific pore volume and pore size and Zetasizer ranked the particle size distribution. Minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) measurements besides agar well diffusion method showed the antimicrobial activity of the nanoparticles. The results revealed no antibacterial activity of the LDH and Cobalt ferrite NPs alone. Meanwhile, the Cobalt ferrite-Chitosan nanohybrid and LDH-Doxycycline showed a high activity antibacterial effect.

Effects of the post-modification using bismuth chelate (BisBAL) on the anti-biofouling and performance properties of flat-sheet microfiltration membranes

Membrane biofouling defined as the attachment and growth of microorganisms on a membrane surface has been a major problem of membrane bioreactor (MBR) technology. The anti-biofouling properties like the inhibition of bacterial adhesion of a membrane are quite significant for a long-term MBR operation. Surface modification is thought to be one of the most common approaches to improve this property. In this study, polymeric microfiltration membranes were modified by adsorption BisBAL, which is a synthesized chelate using bismuth and have a high anti-bacterial effect on various microorganisms, on the membrane surface using dip coating (DC), spin coating (SC), and low pressure-treated coating (LPtC). The purpose was to increase the surface hydrophilicity, change the surface charge, and gain the surface an anti-bacterial characteristic. It was found that the higher adsorption time, lower feed flow rate and higher spinning velocity, and pressure application increased the efficiency of the process during DC, SC, and LPtC, respectively. Furthermore, improved strategies allow the adsorption of BisBAL on the membrane surface and modified membranes has strong resistance to biofouling. Since modification resulted in a decrease in pore fouling and irreversible fouling for all type of membranes, these membranes can be novel alternatives for energy-saving MBR operation.

IN VITRO ANTIBACTERIAL ACTIVITY OF ROYAL GELLY AGAINST PATHOGEN ESCHERICHIA COLI

In the study was used a pathogen strain of E. coli, caused septicemia for ducks,resistant for different antibacterial agents: Amoxicillin, Lincospectin, Chloramphenicol,Doxycyclin, Enrofl oxacin, Sulfonamides and Trimetoprim. Bacterial suspension of E.coli icontaminated each from test solutions in TSB of royal jelly (n=6), mixes of royaljelly and rape honey, and independent used rape honey (10–45% v/v). Have in mindexactly counts of colonies before and after incubation from each of test substanceswas calculated the percent of reduction up to 30 min, and after incubation (24 hand 48 h). In almost all concentrations of royal jelly (10–45 v/v), were found totalinhibition effect to E. coli. Mixes from royal jelly and rape honey (1:100) possesseda higher antibacterial effect, compared with independent use of rape honey. Up to45% (v/v), rape honey does not cause total antibacterial reduction. Royal jelly andmixes from royal jelly and rape honey have potential as alternative therapeuticsagents against resistant for antibiotics pathogen strains of E. coli.

Studies on the Antibacterial Activity and Mechanism of Antimicrobial Peptides Against Drug-Resistant Bacteria.

Antibiotic resistance is a growing threat to human health. More than anything else, multidrug-resistant gram-negative bacteria pose the biggest challenge to healthcare, which is predominantly due to the lack of effective therapeutic options. In the present study, we investigated the activities of peptides HX-12A, HX-12B and HX-12C against MDRAB and MDRKP isolates in vitro. Those three peptides displayed high antibacterial activities and rapid bactericidal effects against MDRAB and MDRKP isolates. Additionally, the peptides retained their activity even being present in pH 6.8 and 8.0, salt (NaCl 100 mM, CaCl2 1 mM, MgCl2 1 mM) or human serum (5%), especially peptide HX-12C. Moreover, the killing kinetics and transmission electron microscopy results suggested that the possible sterilization mechanism of peptides is to destroy the cell membrane, which makes it more difficult for bacteria to develop resistance. Thus, these three peptides may be developed into new antimicrobial agents.

Effect of pure and REM: (Nd, Ce)-doped Dy2O3 NPs via hydrothermal method and their magnetic, optical, electrochemical, antibacterial and photocatalytic activities

Pure Dysprosium oxide (Dy2O3) with the spherical-morphology based material, and the rare earth metal (REM) - doped Dy2O3 nanoparticles (NPs) were synthesized using the reaction of dysprosium (III) nitrate pentahydrate, neodymium (III) nitrate hexahydrate and cerium (III) nitrate hexahydrate by the simple cost-effective hydrothermal method, which exhibits high antibacterial effects and photocatalytic activity. The antibacterial effect of pure and (5 mol% of Nd, Ce) - doped Dy2O3 NPs, on Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella typhi were studied by using various concentrations. The photocatalytic activity of pure and 5 mol% of cerium doped Dy2O3 NPs were assessed by degrading the methyl orange (MO) dye under UV irradiation. The characterization results indicated that the XRD and TEM studies confirms the size of the prepared Dy2O3 NPs decreased with Nd and Ce insertion into dysprosium oxide. The particle size calculated from the Williamson-Hall (W-H) plot was consistent with TEM results. From VSM analysis, cerium doped NPs shows high saturation (Ms) magnetization than that of pure Dy2O3 NPs. The emission spectra and electrochemical properties are found to be dopant dependent. 5 mol% of Ce-doped Dy2O3 NPs shows good antibacterial effect compared to that of pure and Nd doped sample. From the above, it is observed that cerium doped NPs exhibit high photocatalytic activity than pure NPs. The mineralization of MO dye solution for pure and 5 mol% of Ce-doped samples has been confirmed by chemical oxygen demand (COD) measurements. In addition, the rate of decolorization is also confirmed by the total organic carbon (TOC) study. From the results, cerium doped sample enhances the photocatalytic performance compared to pure Dy2O3 NPs due to the lower recombination rate of electron-hole pairs and the presence of large surface area of the samples act as reactive facets for adsorption of MO dye molecules.

Changeability in Retama raetam essential oils chemical composition, antioxidant and antimicrobial properties as affected by the physiological stage

Retama raetam essential oils (EOs) composition and biological activities were assessed during three developmental periods. The essential oil yield varied significantly among the developmental stages and the optimal was detected at the fresh fruiting stage (0.34%). In addition, EOs composition varied significantly (p < 0.05) according to the different developmental stages. In fact, 2-Methoxy-4-vinylphenol, linalool, and 1-octen-3-ol were the main compounds in the vegetative, flowering, and the fresh fruiting stages, respectively. Developmental stage had also a strong effect on EOs antioxidant and antimicrobial activities. In fact, during the fresh fruiting stage, IC50 and EC50 values of the antioxidant assays were 2 to 3 times inferior to all others stages. Concerning the determination of the diameter of inhibition, a slight to high antimicrobial activity was revealed against 12 bacteria and 4 yeasts. Once again, EOs from the fresh fruiting stage had higher bactericidal effect than those from the flowering and vegetative ones (IZ varied from 10 to 13 mm). The results of this investigation showed for the first time the high accumulation of EOs at the early stages of fruit development making the fresh fruiting optimal stage for the extraction of powerful antioxidant and antimicrobial EOs.

Antibacterial Effect of Surface Pretreatment Techniques against Streptococcus Mutans.

The aim of this study was to evaluate the antibacterial surface pretreatment methods against Streptococcus mutans within the infected dentin surface using a tooth cavity model. Seventy-two cavities were prepared on caries-free third molars (n = 8). After sterilization, teeth were inoculated with S. mutans for 48 h. One cavity of each tooth was used to evaluate the infection. Following inoculation, infected cavity surfaces were treated either with (1) Er:YAG Laser (1W; 5x5s, Smart 2940D Plus, Deka Laser), (2) Ozone (80s; HealOzone, Kavo), (3) ErYAG-Ozone combination, (4) Er:YAG-Ozone-CHX combination, (5) Chlorhexidine (CHX), (6) Clearfil Protect Bond (PB), (7) potassium-titanyl-phosphate (KTP) Laser (1W; 60 s, SMARTLITE D, Deka Laser), (8) KTP-Ozone combination, and (9) KTP-Ozone-CHX. Standardized amounts of dentin chips were obtained from the cavity walls, and the number of bacteria recovered was counted. Kruskal-Wallis test was used for statistical analyzes. Both sole antibacterial materials, CHX or Protect Bond application, exhibited the most effective antibacterial activity with 125 and 156 CFU is an acronym of "colony forming unit" usullay mentioned by acronym. (CFU/ml), respectively, among the groups evaluated (P < 0.05). Er:YAG laser irradiation and its combinations with other antibacterial surface pretreatment applications also inhibited the bacterial growth with, respectively, 1444, 406, and 294 CFU/ml bacterial recovery being more efficient than KTP laser irradiation and ozone combinations. As an alternative device with photodynamic effects, Er:YAG and KTP laser irradiations and their further combinations during the cavity pretreatment procedure with chlorhexidine and ozone treatments exerted antibacterial effect against S. mutans, whereas chlorhexidine and antibacterial dentin bonding application solely have the highest antibacterial effects.

Bacterial etiology and antibiotic resistance pattern of pediatric bloodstream infections: A multicenter based study in Tehran, Iran.

Due to the diverse nature of bloodstream infections etiology and to the antibiotic resistance patterns in periodic intervals, rational and accurate use of antibiotics requires an understanding of common causative agents of septicemia and their susceptibility patterns. The present study aimed to determine the bacterial etiology of the neonate and pediatric septicemia, and their antibiotic resistance pattern in Tehran, North of Iran. This retrospective cross-sectional study was conducted along two years, from October 2014 to November 2016 among children with suspected bloodstream infection. Blood specimens were collected aseptically in BACTECTM blood bottles, and standard microbiological methods were applied for the isolation and identification of the bacteria. Antimicrobial susceptibility tests were performed using the disk diffusion method according to Clinical and Laboratory Standards Institute recommendations. Overall, 433 (21.1%) blood cultures showed a significant bacterial growth. Gram-negative bacteria with a proportion of 55.4% were the predominant isolates. The most frequently isolated Gram-negative bacteria were Pseudomonas spp. (26.8%), followed by Klebsiella spp. (8.8%), and Acinetobacter spp. (7.9%). Ciprofloxacin, amikacin, and piperacillin/tazobactam had the highest antibacterial effect on non-fermenting Gram-negative bacilli. Regarding the recovered Enterobacteriaceae, aminoglycosides and carbapenems showed a promising effect for tested isolates. The prevalence of methicillin-resistant S. aureus and coagulase-negative staphylococci were 52.6%, and 78.6%, respectively. The rate of vancomycin-resistant enterococci was estimated 68.8%. Meanwhile, the overall prevalence of multiple-drug resistant isolates was 83.4. Regarding results, Multiple Drug Resistant isolates had a significant role in the occurrence of bloodstream infections. Hopefully, several locally available antibiotics still have promising effects on these isolates.

Isolation and Molecular Identification of Bacteriocin-producing Enterococci with Broad Antibacterial Activity from Traditional Dairy Products in Kerman Province of Iran.

One of the critical limitations to use of bacteriocins produced by lactic acid bacteria as a substitute for chemical antibiotics is the narrow spectrum of their antibacterial activity. The aim of present study was isolation and molecular identification of bacteriocin-producing enterococci with broad antibacterial spectrum. Bacteriocin-producing bacteria were isolated from native dairies in Kerman. Bacteriocins were purified by ammonium sulfate method and the effects of them were investigated on different strains of bacteria. Also, the effects of pH and heat on produced bacteriocins were investigated. High level bacteriocin-producing isolates were identified based on molecular tests. A total of 15 strains of bacteriocin-producing Enterococcus were isolated initially. Enterococcus faecium C-2 and Y-1 strains produced bacteriocins with the highest antibacterial effect. The bacteriocins were stable in pH ranges from 2 to 12 and their antibacterial activity was maintained after autoclave treatment. The maximum bactericidal effect was observed against Listeria monocytogenes and Pseudomonas aeruginosa. In conclusion, use of these bacteriocins as a substitute for chemical antibiotics is recommended.