Insights into the molecular basis of reduced vancomycin susceptibility among three prominent clonal complexes.

Unlabelled: is a leading cause of healthcare-associated infections globally. Vancomycin-resistant (VRSA), those with high-level resistance [minimum inhibitory concentration (MIC) of 16-32 µg/mL vancomycin], are uncommon, whereas vancomycin-intermediate (VISA; MIC of 4-8 µg/mL), are isolated more frequently and develop during long-term and/or repeated use of the antibiotic. VISA can be difficult to eradicate and infections may persist.

Interaction of multidrug-resistant hypervirulent with components of human innate host defense.

strains with a combination of multidrug resistance and hypervirulence genotypes (MDR hvKp) have emerged as a cause of human infections. The ability of these microbes to avoid killing by the innate immune system remains to be tested fully. To that end, we compared the ability of a global collection of hvKp and MDR hvKp clinical isolates to survive in human blood and resist phagocytic killing by human neutrophils.

Microbes and the fate of neutrophils.

Neutrophils or polymorphonuclear neutrophils (PMNs) are an important component of innate host defense. These phagocytic leukocytes are recruited to infected tissues and kill invading microbes. There are several general characteristics of neutrophils that make them highly effective as antimicrobial cells.

Subinhibitory Concentrations of Antibiotics Alter the Response of Klebsiella pneumoniae to Components of Innate Host Defense.

Carbapenem-resistant Klebsiella pneumoniae isolates classified as multilocus sequence type 258 (ST258) are a problem in health care settings in many countries globally. ST258 isolates are resistant to multiple classes of antibiotics and can cause life-threatening infections, such as pneumonia and sepsis, in susceptible individuals. Treatment strategies for such infections are limited.

Toward Optimization of a Rabbit Model of Staphylococcus aureus (USA300) Skin and Soft Tissue Infection.

Staphylococcus aureus remains a leading cause of skin and soft tissue infections (SSTIs) globally. In the United States, many of these infections are caused by isolates classified as USA300. Our understanding of the success of USA300 as a human pathogen is due in part to data obtained from animal infection models, including rabbit SSTI models.

Rapid pathogen-specific recruitment of immune effector cells in the skin by secreted toxins.

Swift recruitment of phagocytic leucocytes is critical in preventing infection when bacteria breach through the protective layers of the skin. According to canonical models, this occurs via an indirect process that is initiated by contact of bacteria with resident skin cells and which is independent of the pathogenic potential of the invader. Here we describe a more rapid mechanism of leucocyte recruitment to the site of intrusion of the important skin pathogen Staphylococcus aureus that is based on direct recognition of specific bacterial toxins, the phenol-soluble modulins (PSMs), by circulating leucocytes.

Further Insight into the Mechanism of Human PMN Lysis following Phagocytosis of Staphylococcus aureus.

Staphylococcus aureus is an important human pathogen that can cause a variety of diseases ranging from mild superficial skin infections to life-threatening conditions like necrotizing pneumonia, endocarditis, and septicemia. Polymorphonuclear leukocytes (PMNs; neutrophils in particular herein) are essential for host defense against S. aureus infections, and the microbe is phagocytosed readily.

Innate Host Defense against Klebsiella pneumoniae and the Outlook for Development of Immunotherapies.

Klebsiella pneumoniae (K. pneumoniae) is a Gram-negative commensal bacterium and opportunistic pathogen. In healthy individuals, the innate immune system is adept at protecting against K.

Phagocytosis and neutrophil extracellular traps.

Neutrophils are recruited rapidly to sites of infection in response to host- and/or microbe-derived proinflammatory molecules. At such sites, neutrophils phagocytose microbes and are activated to produce superoxide and other reactive oxygen species (ROS). In addition, neutrophils contain stores of antimicrobial peptides and enzymes that work in concert with ROS to kill ingested microbes.

Bacteriophage Treatment Rescues Mice Infected with Multidrug-Resistant Klebsiella pneumoniae ST258.

Severe infections caused by multidrug-resistant sequence type 258 (ST258) highlight the need for new therapeutics with activity against this pathogen. Bacteriophage (phage) therapy is an alternative treatment approach for multidrug-resistant bacterial infections that has shown efficacy in experimental animal models and promise in clinical case reports. In this study, we assessed microbiologic, histopathologic, and survival outcomes following systemic administration of phage in ST258-infected mice.

Streptococcus pyogenes genes that promote pharyngitis in primates.

Streptococcus pyogenes (group A streptococcus; GAS) causes 600 million cases of pharyngitis annually worldwide. There is no licensed human GAS vaccine despite a century of research. Although the human oropharynx is the primary site of GAS infection, the pathogenic genes and molecular processes used to colonize, cause disease, and persist in the upper respiratory tract are poorly understood.

, Antibiotic Resistance, and the Interaction with Human Neutrophils.

is among the leading causes of bacterial infections worldwide. The high burden of among human and animal hosts, which includes asymptomatic carriage and infection, is coupled with a notorious ability of the microbe to become resistant to antibiotics. Notably, has the ability to produce molecules that promote evasion of host defense, including the ability to avoid killing by neutrophils.

Genetic heterogeneity of the Spy1336/R28-Spy1337 virulence axis in Streptococcus pyogenes and effect on gene transcript levels and pathogenesis.

Streptococcus pyogenes is a strict human pathogen responsible for more than 700 million infections annually worldwide. Strains of serotype M28 S. pyogenes are typically among the five more abundant types causing invasive infections and pharyngitis in adults and children.

New Pathogenesis Mechanisms and Translational Leads Identified by Multidimensional Analysis of Necrotizing Myositis in Primates.

A fundamental goal of contemporary biomedical research is to understand the molecular basis of disease pathogenesis and exploit this information to develop targeted and more-effective therapies. Necrotizing myositis caused by the bacterial pathogen is a devastating human infection with a high mortality rate and few successful therapeutic options. We used dual transcriptome sequencing (RNA-seq) to analyze the transcriptomes of and host skeletal muscle recovered contemporaneously from infected nonhuman primates.

Vaccine Protection against Multidrug-Resistant Klebsiella pneumoniae in a Nonhuman Primate Model of Severe Lower Respiratory Tract Infection.

is a human gut communal organism and notorious opportunistic pathogen. The relative high burden of asymptomatic colonization by is often compounded by multidrug resistance-a potential problem for individuals with significant comorbidities or other risk factors for infection. A carbapenem-resistant strain classified as multilocus sequence type 258 (ST258) is widespread in the United States and is usually multidrug resistant.

capsule polysaccharide as a target for therapeutics and vaccines.

Carbapenem-resistant (CR) has emerged as an urgent public health threat in many industrialized countries worldwide, including the United States. Infections caused by CR are difficult to treat because these organisms are typically resistant to multiple antibiotics, and the patients have significant comorbidities. Notably, there is high (∼50%) mortality among individuals with bacteremia caused by CR .

Genome-Scale Transcript Analyses of Human Neutrophils.

Transcriptome analyses of unicellular and multicellular organisms have changed fundamental understanding of biological and pathological processes across multiple scientific disciplines. Over the past 15 years, studies of polymorphonuclear leukocyte (PMN or neutrophil) gene expression on a global scale have provided new insight into the molecular processes that promote resolution of infections in humans. Herein we present methods to analyze gene expression in human neutrophils using Affymetrix oligonucleotide microarrays and next-generation sequencing.

Isolation of Neutrophils from Nonhuman Species.

The development of new advances in understanding the role of neutrophils in inflammation requires effective procedures for isolating and purifying neutrophils. Methods for isolating human neutrophils are fairly standard, and some are covered in other chapters of this volume and previous editions. However, procedures for isolating neutrophils from nonhuman species used to model human diseases vary from those used in isolating human neutrophils and are not as well developed.

The Role of Neutrophils in the Immune System: An Overview.

Neutrophils, also known as polymorphonuclear neutrophils (PMNs), have long been considered as the short-lived, nonspecific white cells that form pus-and also happen to kill invading microbes. Indeed, neutrophils were often neglected (and largely not considered) as immune cells. This historic view of neutrophils has changed considerably over the past several decades, and we now know that in addition to playing the predominant role in the clearance of bacteria and fungi, they have a major role in shaping the host response to infection and immune system homeostasis.

Neutrophils in innate immunity and systems biology-level approaches.

The innate immune system is the first line of host defense against invading microorganisms. Polymorphonuclear leukocytes (PMNs or neutrophils) are the most abundant leukocyte in humans and essential to the innate immune response against invading pathogens. Compared to the acquired immune response, which requires time to develop and is dependent on previous interaction with specific microbes, the ability of neutrophils to kill microorganisms is immediate, nonspecific, and not dependent on previous exposure to microorganisms.

Mouse Model of Staphylococcus aureus Skin Infection.

Bacterial skin and soft tissue infections are abundant worldwide, and many are caused by Staphylococcus aureus. Indeed, S. aureus is the leading cause of skin and soft tissue infections in the USA.