Over the past 40 years, quorum sensing (QS)-a type of chemical communication used by common bacteria-has been shown to be play an increasingly important role in bacterial communities. QS mediates a wide array of bacterial group behaviors such as initiating infection, mediating symbiosis, and adapting to environmental stimuli. A common QS pathway used by many Gram-positive bacteria is the accessory gene regulator (agr) system, which has been recognized as a key regulator of virulence in several clinically relevant pathogens. Activation of agr QS and its downstream regulation is dependent upon the production and reception of a peptide signal known as the autoinducing peptide (AIP). Interfering with this signaling process using non-native chemical modulators that target the various components of agr represents an approach to attenuate agr QS activity and alter associated bacterial phenotypes. There currently is a dearth of potent and efficacious chemical modulators for the majority of agr systems. Moreover, many of these synthetic ligands have been only examined in vitro, and many questions remain about the modes by which bacteria use agr QS in vivo and the methods by which to best leverage these chemical modulators to reduce bacterial virulence. In this thesis, I describe my work to create, develop, and apply chemical tools to investigate agr QS in three important pathogens. I performed structure-activity relationship (SAR) analyses on the native AIP signal of Listeria monocytogenes and uncovered the most potent agr agonists and antagonists of its agr system to date. These modulators can strongly promote or inhibit biofilm formation, a critical virulence phenotype in L. monocytogenes, demonstrating the utility of chemical control of agr activity. Structural and SAR studies of the AIPs from Staphylococcus epidermidis revealed new structural insights into modulator potency and efficacy, as well as enabling the development of the first agonists capable of activating multiple AgrC receptors. Lastly, I characterized degradable polymeric materials loaded with potent Staphylococcus aureus agr antagonists and demonstrated their ability to attenuate infection in a murine model. The studies presented herein represent significant advances towards developing chemical tools to probe and control agr QS in important Gram-positive bacteria.

Over the past 40 years, quorum sensing (QS)-a type of chemical communication used by common bacteria-has been shown to be play an increasingly important role in bacterial communities. QS mediates a wide array of bacterial group behaviors such as initiating infection, mediating symbiosis, and adapting to environmental stimuli. A common QS pathway used by many Gram-positive bacteria is the accessory gene regulator (agr) system, which has been recognized as a key regulator of virulence in several clinically relevant pathogens. Activation of agr QS and its downstream regulation is dependent upon the production and reception of a peptide signal known as the autoinducing peptide (AIP). Interfering with this signaling process using non-native chemical modulators that target the various components of agr represents an approach to attenuate agr QS activity and alter associated bacterial phenotypes. There currently is a dearth of potent and efficacious chemical modulators for the majority of agr systems. Moreover, many of these synthetic ligands have been only examined in vitro, and many questions remain about the modes by which bacteria use agr QS in vivo and the methods by which to best leverage these chemical modulators to reduce bacterial virulence. In this thesis, I describe my work to create, develop, and apply chemical tools to investigate agr QS in three important pathogens. I performed structure-activity relationship (SAR) analyses on the native AIP signal of Listeria monocytogenes and uncovered the most potent agr agonists and antagonists of its agr system to date. These modulators can strongly promote or inhibit biofilm formation, a critical virulence phenotype in L. monocytogenes, demonstrating the utility of chemical control of agr activity. Structural and SAR studies of the AIPs from Staphylococcus epidermidis revealed new structural insights into modulator potency and efficacy, as well as enabling the development of the first agonists capable of activating multiple AgrC receptors. Lastly, I characterized degradable polymeric materials loaded with potent Staphylococcus aureus agr antagonists and demonstrated their ability to attenuate infection in a murine model. The studies presented herein represent significant advances towards developing chemical tools to probe and control agr QS in important Gram-positive bacteria.

Established almost 30 years ago, Methods in Microbiology is the most prestigious series devoted to techniques and methodology in the field. Now totally revamped, revitalized, with a new format and expanded scope, Methods in Microbiology will continue to provide you with tried and tested, cutting-edge protocols to directly benefit your research. - Focuses on the methods most useful for the microbiologist interested in the way in which bacteria cause disease - Includes section devoted to 'Approaches to characterising pathogenic mechanisms' by Stanley Falkow - Covers safety aspects, detection, identification and speciation - Includes techniques for the study of host interactions and reactions in animals and plants - Describes biochemical and molecular genetic approaches - Essential methods for gene expression and analysis - Covers strategies and problems for disease control

Providing a comprehensive insight into cellular signaling processes in bacteria with a special focus on biotechnological implications, this is the first book to cover intercellular as well as intracellular signaling and its relevance for biofilm formation, host pathogen interactions, symbiotic relationships, and photo- and chemotaxis. In addition, it deals in detail with principal bacterial signaling mechanisms -- making this a valuable resource for all advanced students in microbiology. Dr. Krämer is a world-renowned expert in intracellular signaling and its implications for biotechnology processes, while Dr. Jung is an expert on intercellular signaling and its relevance for biomedicine and agriculture.

Throughout the biological world, bacteria thrive predominantly in surface-attached, matrix-enclosed, multicellular communities or biofilms, as opposed to isolated planktonic cells. This choice of lifestyle is not trivial, as it involves major shifts in the use of genetic information and cellular energy, and has profound consequences for bacterial physiology and survival. Growth within a biofilm can thwart immune function and antibiotic therapy and thereby complicate the treatment of infectious diseases, especially chronic and foreign device-associated infections. Modern studies of many important biofilms have advanced well beyond the descriptive stage, and have begun to provide molecular details of the structural, biochemical, and genetic processes that drive biofilm formation and its dispersion. There is much diversity in the details of biofilm development among various species, but there are also commonalities. In most species, environmental and nutritional conditions greatly influence biofilm development. Similar kinds of adhesive molecules often promote biofilm formation in diverse species. Signaling and regulatory processes that drive biofilm development are often conserved, especially among related bacteria. Knowledge of such processes holds great promise for efforts to control biofilm growth and combat biofilm-associated infections. This volume focuses on the biology of biofilms that affect human disease, although it is by no means comprehensive. It opens with chapters that provide the reader with current perspectives on biofilm development, physiology, environmental, and regulatory effects, the role of quorum sensing, and resistance/phenotypic persistence to antimicrobial agents during biofilm growth.

Methicillin-resistant Staphylococcus aureus (MRSA) emerged as a clinically relevant human pathogen more than five decades ago. The virulent bacterium was first detected in hospitals and other health care facilities where vulnerable hosts, frequent exposure to the selective pressure of intensive antimicrobial therapy, and the necessity for invasive procedures created a favorable environment for dissemination. MRSA emerged as an important cause of healthcare-associated infections, particularly central line-associated bloodstream infection, ventilator-associated pneumonia, and surgical site infection (SSI). Despite the adoption of infection-control measures, the incidence of MRSA infection at most U.S. hospitals steadily increased for many years, but it is now decreasing. While the decrease in the incidence of MRSA infection may be due to efforts to screen for MRSA carriage, it may also be due to secular trends (such as efforts to improve patient safety) and to confounders (such as efforts to improve the appropriate use of antibiotics and to decrease healthcare-associated infections in general, including catheter-associated bloodstream infection, ventilator-associated pneumonia, and SSI). A number of analyses suggest that MRSA infections are associated with increased mortality and cost of care when compared with those due to strains that are susceptible to methicillin. Even the availability of newer pharmaceutical agents with specific activity against MRSA has not ameliorated the challenge of caring for patients with MRSA. The widespread use of these agents has been limited, in part due to toxicity, cost, and uncertainty as to optimal indications. The management and control of MRSA have been further complicated by dramatic changes in the epidemiology of transmission and infection observed over the past two decades. Specifically, S. aureus strains resistant to methicillin, once exclusively linked to hospital care, have increasingly been detected among patients in the community who lack conventional risk factors for MRSA infection. Community-acquired MRSA has been linked to outbreaks of infection in hospitals and health care facilities. Conventional strategies for the control of MRSA have focused on the prevention of spread from patient to patient. The effectiveness of hand hygiene in preventing the spread of MRSA has been demonstrated in observational studies in which hand hygiene promotion campaigns were associated with subsequent reductions in the incidence of MRSA among hospitalized patients. While hand hygiene remains important in the effort to control MRSA transmission, the continued spread of the pathogen after its initial introduction in most facilities has prompted efforts to identify additional strategies. The use of contact isolation-including the donning of gowns and gloves when interacting with patients colonized or infected with MRSA and the assignment of such patients to single rooms or to a room with a group of affected patients-has been widely promoted and adopted. Such isolation precautions now are the centerpiece of most authoritative guidelines for MRSA control. Despite the broad consensus associated with the use of contact isolation for MRSA prevention, the specific evidence in support of this practice remains limited and indirect. The objective of this review was to synthesize comparative studies that examined the benefits or harms of screening for MRSA carriage in the inpatient or outpatient settings. The review examined MRSA-screening strategies applied to all hospitalized or ambulatory patients, as well as screening strategies applied to selected inpatient or outpatient populations, and compared them with no screening or with screening of selected patient populations. The review evaluated MRSA-screening strategies that included screening with or without isolation and with or without attempted eradication/decolonization.