Maryam Hassan

Natural antimicrobial peptides from bacteria: characteristics and potential applications to fight against antibiotic resistance.

Because of the emergence of antibiotic‐resistant pathogens worldwide, a number of infectious diseases have become difficult to treat. This threatening situation is worsened by the fact that very limited progress has been made in developing new and potent antibiotics in recent years. However, a group of antimicrobials, the so‐called bacteriocins, have been much studied lately because they hold a great potential in controlling antibiotic‐resistant pathogens. Bacteriocins are small antimicrobial peptides (AMPs) produced by numerous bacteria. They often act toward species related to the producer with a very high potency (at pico‐ to nanomolar concentration) and specificity. The common mechanisms of killing by bacteriocins are destruction of target cells by pore formation and/or inhibition of cell wall synthesis. Several studies have revealed that bacteriocins display great potential in the medical sector as bacteriocinogenic probiotics and in the clinic as therapeutic agents. In this review, we discuss the emerging antibiotic resistance and strategies to control its dissemination, before we highlight the potential of AMPs from bacteria as a new genre of antimicrobial agents.

Nanoliposome-based antibacterial drug delivery.

Abstract Although most bacterial infectious diseases can be treated successfully with the remarkable array of antibiotics, the microbial pathogens continue to be one of the most critical health challenges worldwide. One of the common efforts in addressing this issue lies in improving the existing antibacterial delivery systems since inefficient delivery can lead to poor therapeutic outcome of the administered drug. Recently, nanoliposomal systems have been widely used as promising strategies to overcome these challenges due to their unique set of properties. This article tries to briefly summarize the current studies that have taken advantage of liposomal nanoparticles as carriers to deliver antibacterial agents. The reviewed investigations demonstrate the immense potential of liposomal nanoparticles as carriers for antibiotic delivery and highlight the latent promise in this class of vehicles for treatment of bacterial infections. The future of these promising approaches lies in the development of more efficient techniques for preparing liposomal nanoparticles with great potential in effective and selective targeting of antibiotics to bacterial cells for eradication as well as the highest safety for human host.

Study of antimicrobial effects of vancomycin loaded PLGA nanoparticles against enterococcus clinical isolates.

Researchers have demonstrated that antimicrobial agents in nanoparticle (NP) forms have better activities. Vancomycin (VCM), as a glycopeptide antibiotic with antimicrobial activity against gram positive bacteria, is poorly absorbed from the intestinal tract. Enterococcus is a genus of bacteria that became resistant to a wide range of antibiotics in last decades, and cause severe infections in hospitalized patients. This paper describes preparation of VCM--loaded poly (lactic-co-glycolic acid) (PLGA) NPs and compares the antimicrobial effects with drug solution against clinical Enterococcus isolates. VCM-loaded PLGA NPs were fabricated by W1/O/W2 solvent evaporation method. The comparison of obtained Minimum Inhibitory Concentration (MIC) values showed a significant decrease in the antimicrobial effect of VCM -loaded NPs. Results also indicated that the potency of the NPs against VCM resistant isolates of Enterococcus was less than VCM susceptible isolates. The reduced antimicrobial effect of formulated NPs in invitro condition is perhaps related to the strong electrostatic linkage between hydrophilic drug (VCM) and hydrophobic polymer (PLGA) that lead to the slow release of the antibiotic from polymeric NPs.

Prevalence of bacteriocin activities and bacteriocin-encoding genes in enterococcal clinical isolates in Iran.

The aim of the project was to isolate and characterize bacteriocin-producing enterococci, as well as determine the prevalence of enterocin structural genes in 187 enterococcal clinical isolates from the northwest of Iran. The isolates were screened for antibacterial activity against 15 different indicator strains. The proteinaceous nature of the antimicrobial substances was confirmed by sensitivity to proteinase K; their stability to heat treatment was tested at 60 °C and 100 °C for 20 and 10 min, respectively. The PCR method was applied to detect previously identified enterocin genes. Our results showed that 38 (20.3%) of the enterococcal isolates were considered to be potential bacteriocinogenic strains. Furthermore, genes encoding diverse bacteriocin are highly distributed among clinical enterococci, and the strains with multi-bacteriocin genes displayed high antimicrobial activity. Enterocin A, enterolysin A, and enterocin L50A/B were the most abundant structural genes detected in bacteriocinogenic strains. This work is the first survey on the prevalence of bacteriocin genes among clinical enterococci in Iran that has isolated a strain with high antimicrobial activity and sensitivity to clinically relevant antibiotics.

Determination of comparative minimum inhibitory concentration (MIC) of bacteriocins produced by enterococci for selected isolates of multi-antibiotic resistant Enterococcus spp.

INTRODUCTION The occurrence of multi-antibiotic resistance among enterococci is a prevalent clinical problem worldwide and continues to get serious due to the lack of efficient therapeutic options by the time. In this regards, prokaryotic antimicrobial peptides with bactericidal or bacteriostatic activity which are directed against bacterial strains closely related to producer strains looks one of the promising alternative to conventional antibiotics. METHODS The antibiotic susceptibility pattern of 20 clinical isolates of enterococci was evaluated and subsequently the isolates were screened for antibacterial activity against three different indicator strains. The efficacy of potential bacteriocinogenic isolates were assayed against multi-antibiotic resistant Enterococcus spp. by comparative minimum inhibitory concentration (MIC). RESULTS Antibiotic resistant pattern of enterococcal isolates demonstrated that multi-antibiotic resistant to conventional antibiotics were significantly high and the prevalent pattern of resistance was combination of gentamicin, streptomycin, chloramphenicol and vancomycin. In addition, the data from comparative MIC showed the noticeable activity of selected potential bacteriocinogenic strains against pathogenic enterococci. CONCLUSION The present survey may address the potential applicability of antimicrobial peptides in alleviating the problems of antibiotic resistance.

Evaluation of Bacteriocin Activities among Enterococcal Poultry Isolates from East Azarbaijan Iran

The objectives of the study were to isolate and characterize the bacteriocin producing enterococci in 30 enterococcal poultry isolates from north-west of Iran and to determine the prevalence of bacteriocin structural genes among them. Methods: The obtained isolates were assessed for antibacterial action against 6 indicator strains. The PCR method was applied to detect previously identified enterocin genes. Results: Based on our results 4 (13.3%) of the examined poultry enterococcal isolates were considered as potential bacteriocinogenic strains, all of them identified to be Enterococcus faecium via phenotypic and genotypic examinations. At least one of the detected Bac+ isolates had antibacterial activities against Bacillus cereus, Listeria monocytogenes, Enterococcus faecalis and Enterococcus hirea with no activity against Escherichia coli or Staphylococcus aureus. Conclusion: Genes encoding Enterocin A and enterocin LA50A/B are fairly distributed among the studied poultry enterococci.

Efficient Inactivation of Multi-Antibiotics Resistant Nosocomial Enterococci by Purified Hiracin Bacteriocin

PURPOSE Because of the emergence of multi-antibiotic resistant bacteria, a number of infectious diseases have become a major concern to treat in health care services worldwide. This situation is worsened by the fact that very limited progress has been made in developing new and potent antibiotics in recent years. In this context antimicrobial peptides (AMPs) represent new potential therapeutic compounds with bactericidal or bacteriostatic activity against closely related bacterial strains. METHODS In this study, a collection of enterococci (n=170) from clinical sources were investigated for their potential to inhibit multiresistant nosocomial enterococci from Iranian hospitals. RESULTS Four isolates produced antimicrobial peptides that inhibited all the antibiotic resistant enterococci. This included three Enterococcus faecium isolates producing combinations of enterocin A, B and L50 AB. The most potent antagonism was produced by E. faecalis HO91. Purification and subsequent characterization by MALDI-TOF MS, Edman degradation and DNA-sequencing revealed that the antimicrobial compound was Hiracin. The purified Hiracin was evaluated for antibacterial activity against 12 multiresistant enterococcal isolates from clinical samples. The results demonstrated that Hiracin is highly effective towards enterococci which were resistant even to antibiotics from four distinct classes. CONCLUSION The present research addresses Hiracin as a promising alternative to conventional antibiotics in treatment of multiresistant enterococcal infections.

Protective Effect of Matricaria chamomilla Ethanolic Extract on Hippocampal Neuron Damage in Rats Exposed to Formaldehyde

Formaldehyde, as a frequently used compound in many applications, crosses the blood-brain barrier and leads to hippocampal cell death and memory impairment. This study investigates the effects of ethanolic extract of Matricaria chamomilla (MC) on passive avoidance learning induced by damaged hippocampal cells and evaluates the antioxidant traits of MC. The male Wistar rats were divided into six (6 in each) groups: control (10 mg/kg normal saline), 200 (200 mg/kg MC extract), 500 (500 mg/kg MC extract), F (10 mg/kg formaldehyde), F200 (10 mg/kg formaldehyde and 200 mg/kg MC extract), and F500 (10 mg/kg formaldehyde and 500 mg/kg MC extract). Shuttle box assay was used for evaluation of passive avoidance learning. The apoptosis rate of hippocampal tissue, malondialdehyde (MDA) free radicals, and total antioxidant capacity was evaluated to determine the positive effect of the ethanolic extract of MC. We found that the ethanolic extract of MC reduced the cell death, time spent in a dark room, and MDA free radicals in the hippocampus, leading to increased total antioxidant capacity in this region. In conclusion, the ethanolic extract of MC could ameliorate formaldehyde-induced memory damage through decreasing cell death and MDA activity of the hippocampal region and increasing total antioxidant capacity.

Evaluation of Volatile Oil in Indigenous Populations of Ferula gummosa Boiss

Abstract Essential oil components and yield of Ferula gummosa Boiss, in different bioclimates of Iran, has been investigated. The highest essential oil versus galbanum dry weight was recorded in the samples from Ebrahim Abad (16.9 %) and the lowest amount (11 %) was measured from Angouran. Monoterpenes Hydrocabons (α-pinene (17-56.55 %), β-pinene (10.44-37.04 %), δ 3-carene (9.16-10.75 %) and Limonene (0-13.23 %)) were the predominant oils components of F. gummosa. The high variability in the oil content and composition in different populations showed a remarkable difference in monoterpenes content variation from 79.47 to 86.48 %. The highest concentration of α-pinene (56.55 %) was in the Galbanum sampled from Angouran (AG) followed by β-pinene having the highest concentration (37.04 %) from the roots samples. There was a considerable chemo-variation in the oils, the study is useful base for breeding programs of medicinal plants in order to obtain a proper line with advantageous compound as natural source for pharmaceutical and agricultural industries.