http://www.mdpi.com/journal/ijms/special_issues/antimicrobial-agents/ Dear Colleagues, Antibiotics can be defined as low-molecular weight substances that have a cidal (killing) effect or a static (inhibitory) effect on a range of microbes, as secondary metabolites by certain groups of microorganisms. The modern era of antimicrobial chemotherapy began in 1929 with Fleming’s discovery of the powerful bacteriocidal substrance penicillin G from Pennicilium notatum, and Domagk’s discovery in 1935 of synthetic chemicals (sulfonamides) with broad antimicrobial activity. The most important property of an antimicrobial agent, from the standpoint of host, is its selective toxicity, i.e., the agent acts in some way that inhibits or kills bacterial pathogens but has little or no toxic effect on the host. Until these days, many efforts have been invested in development of new powerful antibiotics with specific narrow spectrum. In the consequence of growing problems of pathogenic organism which are resistant to conventional antibiotics, however, development of new class of antibiotics has become strongly required. In the past 15 years, hundreds of antimicrobial agents have been isolated from a wide variety of plants, invertebrates, amphibians, and mammals, as well as bacteria and fungi. The widespread occurrence of these antimicrobial agents suggests a key role in host defense. Antimicrobial agent whose main advantage are as factors of innate immunity so that they can promptly synthesized upon induction as low molecular cost, can be easily stored in a large amount, and act against invasion by occasional and obligate pathogens. Computational advances in structure based drug design are presented which emphasize the development of protocols and methodology used in force-field parameterization, scoring function development, structure prediction and validation, and docking. Computational chemistry and molecular modeling are the science of representing molecular structures numerically and simulating their behavior with the equations of quantum and classical physics. Molecular modeling was extended to wide concept that design new antimicrobial agent through that predicted three-dimension structure of molecule and property of antimicrobial agent by theoretical calculation. Dooil Kim, Ph.D. Guest Editor Submission All papers should be submitted to ijms@mdpi.com. To be published continuously until the deadline and papers will be listed together at the special issue website. Submitted papers should not have been published previously, nor be under consideration for publication elsewhere. All papers are refereed through a peer-review process. A guide for authors is available on the Instructions for Authors page. The International Journal of Molecular Sciences is an international peer-reviewed monthly journal published by MDPI. Open Access publication fees are 800 CHF per paper. English correction fees and/or formatting fees (250 CHF) will be added in certain cases (1050 CHF per paper for those papers that require extensive additional formatting and/or English corrections). http://www.mdpi.com/1422-0067/10/9/3951/ Host defense peptides can modulate the innate immune response and boost infection-resolving immunity, while dampening potentially harmful pro-inflammatory (septic) responses. Both antimicrobial and/or immunomodulatory activities are an integral part of the process of innate immunity, which itself has many of the hallmarks of successful anti-infective therapies, namely rapid action and broad-spectrum antimicrobial activities. This gives these peptides the potential to become an entirely new therapeutic approach against bacterial infections. This review details the role and activities of these peptides, and examines their applicability as development candidates for use against bacterial infections. http://www.mdpi.com/1422-0067/10/9/3951/ Wed, 09 Sep 2009 00:00:00 CEST International Journal of Molecular Sciences 2009-09-09 10 9 Review 3951 3970 1422-0067 Host Defense Peptides as Effector Molecules of the Innate Immune Response: A Sledgehammer for Drug Resistance? 2009-09-09 doi: 10.3390/ijms10093951 Lars Steinstraesser Ursula M. Kraneburg Tobias Hirsch Marco Kesting Hans-Ulrich Steinau Frank Jacobsen Sammy Al-Benna http://www.mdpi.com/1422-0067/10/8/3531/ The increase of productivity in the poultry industry has been accompanied by various impacts, including emergence of a large variety of pathogens and bacterial resistance. These impacts are in part due to the indiscriminate use of chemotherapeutic agents as a result of management practices in rearing cycles. This review provides a summary of the use of probiotics for prevention of bacterial diseases in poultry, as well as demonstrating the potential role of probiotics in the growth performance and immune response of poultry, safety and wholesomeness of dressed poultry meat evidencing consumer’s protection, with a critical evaluation of results obtained to date. http://www.mdpi.com/1422-0067/10/8/3531/ Wed, 12 Aug 2009 00:00:00 CEST International Journal of Molecular Sciences 2009-08-12 10 8 Review 3531 3546 1422-0067 The Role of Probiotics in the Poultry Industry 2009-08-12 doi: 10.3390/ijms10083531 S. M. Lutful Kabir http://www.mdpi.com/1422-0067/10/8/3400/ To protect themselves, plants accumulate an armoury of antimicrobial secondary metabolites. Some metabolites represent constitutive chemical barriers to microbial attack (phytoanticipins) and others inducible antimicrobials (phytoalexins). They are extensively studied as promising plant and human disease-controlling agents. This review discusses the bioactivity of several phytoalexins and phytoanticipins defending plants against fungal and bacterial aggressors and those with antibacterial activities against pathogens affecting humans such as Pseudomonas aeruginosa and Staphylococcus aureus involved in respiratory infections of cystic fibrosis patients. The utility of plant products as “antibiotic potentiators” and “virulence attenuators” is also described as well as some biotechnological applications in phytoprotection. http://www.mdpi.com/1422-0067/10/8/3400/ Fri, 31 Jul 2009 00:00:00 CEST International Journal of Molecular Sciences 2009-07-31 10 8 Review 3400 3419 1422-0067 Plant Antimicrobial Agents and Their Effects on Plant and Human Pathogens 2009-07-31 doi: 10.3390/ijms10083400 Rocío González-Lamothe Gabriel Mitchell Mariza Gattuso Moussa S. Diarra François Malouin Kamal Bouarab http://www.mdpi.com/1422-0067/10/6/2860/ Antimicrobial proteins (peptides) are known to play important roles in the innate host defense mechanisms of most living organisms, including plants, insects, amphibians and mammals. They are also known to possess potent antibiotic activity against bacteria, fungi, and even certain viruses. Recently, the rapid emergence of microbial pathogens that are resistant to currently available antibiotics has triggered considerable interest in the isolation and investigation of the mode of action of antimicrobial proteins (peptides). Plants produce a variety of proteins (peptides) that are involved in the defense against pathogens and invading organisms, including ribosome-inactivating proteins, lectins, protease inhibitors and antifungal peptides (proteins). Specially, the protease inhibitors can inhibit aspartic, serine and cysteine proteinases. Increased levels of trypsin and chymotrypsin inhibitors correlated with the plants resistance to the pathogen. Usually, the purification of antimicrobial proteins (peptides) with protease inhibitor activity was accomplished by salt-extraction, ultrafiltration and C18 reverse phase chromatography, successfully. We discuss the relation between antimicrobial and anti-protease activity in this review. Protease inhibitors from plants potently inhibited the growth of a variety of pathogenic bacterial and fungal strains and are therefore excellent candidates for use as the lead compounds for the development of novel antimicrobial agents. http://www.mdpi.com/1422-0067/10/6/2860/ Tue, 23 Jun 2009 00:00:00 CEST International Journal of Molecular Sciences 2009-06-23 10 6 Review 2860 2872 1422-0067 Protease Inhibitors from Plants with Antimicrobial Activity 2009-06-23 doi: 10.3390/ijms10062860 Jin-Young Kim Seong-Cheol Park Indeok Hwang Hyeonsook Cheong Jae-Woon Nah Kyung-Soo Hahm Yoonkyung Park http://www.mdpi.com/1422-0067/10/2/629/ AcrAB-TolC is the major multidrug efflux system in Enterobacteriaceae recognizing structurally unrelated molecules including antibiotics, dyes, and detergents. Additionally, in Escherichia coli it mediates resistance to bile salts. In the plant pathogen Erwinia amylovora AcrAB-TolC is required for virulence and phytoalexin resistance. Exchange analysis of AcrAB-TolC was conducted by complementing mutants of both species defective in acrB or tolC with alleles from either species. The acrB and tolC mutants exhibited increased susceptibility profiles for 24 different antibiotics. All mutants were complemented with acrAB or tolC, respectively, regardless of the taxonomic origin of the alleles. Importantly, complementation of E. amylovora mutants with respective E. coli genes restored virulence on apple plants. It was concluded that AcrAB and TolC of both species could interact and that these interactions did not yield in altered functions despite the divergent ecological niches, to which E. coli and E. amylovora have adopted. http://www.mdpi.com/1422-0067/10/2/629/ Thu, 19 Feb 2009 00:00:00 CET International Journal of Molecular Sciences 2009-02-19 10 2 Article 629 645 1422-0067 Genetic Exchange of Multidrug Efflux Pumps among Two Enterobacterial Species with Distinctive Ecological Niches 2009-02-19 doi: 10.3390/ijms10020629 Nehaya Al-Karablieh Helge Weingart Matthias S. Ullrich