On the in vivo significance of bacterial resistance to antimicrobial peptides

Antimicrobial peptides (AMPs) are at the front-line of host defense during infection and play critical roles both in reducing the microbial load early during infection and in linking innate to adaptive immunity. However, successful pathogens have developed mechanisms to resist AMPs. Although considerable progress has been made in elucidating AMP-resistance mechanisms of pathogenic bacteria in vitro, less is known regarding the in vivo significance of such resistance. Nevertheless, progress has been made in this area, largely by using murine models and, in two instances, human models of infection. Herein, we review progress on the use of in vivo infection models in AMP research and discuss the AMP resistance mechanisms that have been established by in vivo studies to contribute to microbial infection. We posit that in vivo infection models are essential tools for investigators to understand the significance to pathogenesis of genetic changes that impact levels of bacterial susceptibility to AMPs. This article is part of a Special Issue entitled: Bacterial Resistance to Antimicrobial Peptides

Experimental Gonococcal Infection in Male Volunteers: Cumulative Experience with Neisseria gonorrhoeae Strains FA1090 and MS11mkC

Experimental infection of male volunteers with Neisseria gonorrhoeae is safe and reproduces the clinical features of naturally acquired gonococcal urethritis. Human inoculation studies have helped define the natural history of experimental infection with two well-characterized strains of N. gonorrhoeae, FA1090 and MS11mkC. The human model has proved useful for testing the importance of putative gonococcal virulence factors for urethral infection in men. Studies with isogenic mutants have improved our understanding of the requirements for gonococcal LOS structures, pili, opacity proteins, IgA1 protease, and the ability of infecting organisms to obtain iron from human transferrin and lactoferrin during uncomplicated urethritis. The model also presents opportunities to examine innate host immune responses that may be exploited or improved in development and testing of gonococcal vaccines. Here we review results to date with human experimental gonorrhea

The Human Host Defense Peptide LL-37 Interacts with Neisseria meningitidis Capsular Polysaccharides and Inhibits Inflammatory Mediators Release

Capsular polysaccharides (CPS) are a major virulence factor in meningococcal infections and form the basis for serogroup designation and protective vaccines. Our work has identified meningococcal CPS as a pro-inflammatory ligand that functions through TLR2 and TLR4-MD2-dependent activation. We hypothesized that human cationic host defense peptides interact with CPS and influence its biologic activity. Accordingly, the interaction of meningococcal CPS with the human-derived cationic peptide LL-37, which is expressed by phagocytic and epithelial cells that interface with meningococci during infection, was investigated. LL-37 neutralized the pro-inflammatory activity of endotoxin-free CPS as assessed by TLR2 and TLR4-MD-2-dependent release of TNFα, IL-6 and IL-8 from human and murine macrophages. The cationic and hydrophobic properties of LL-37 were crucial for this inhibition, which was due to binding of LL-37 to CPS. LL-37 also inhibited the ability of meningococcal CPS to induce nitric oxide release, as well as TNFα and CXCL10 (IP-10) release from TLR4-sufficient and TLR4-deficient murine macrophages. Truncated LL-37 analogs, especially those that retained the antibacterial domain, inhibited vaccine grade CPS and meningococcal CPS prepared from the major serogroups (A, B C, Y and W135). Thus, LL-37 interaction with CPS was independent of specific glucan structure. We conclude that the capacity of meningococcal CPS to activate macrophages via TLR2 and TLR4-MD-2 can be inhibited by the human cationic host defense peptide LL-37 and propose that this impacts CPS-based vaccine responses

Juvenile Probation Officers Call for a New Response to Teen Drug and Alcohol Use and Dependency

Shares lessons learned from RWJF's Reclaiming Futures initiative from a juvenile justice practitioner's perspective. Discusses the need to reform the system's treatment services, the challenges faced at the ten project sites, and recommendations

Lipooligosaccharide Structure is an Important Determinant in the Resistance of Neisseria Gonorrhoeae to Antimicrobial Agents of Innate Host Defense

The strict human pathogen Neisseria gonorrhoeae has caused the sexually transmitted infection termed gonorrhea for thousands of years. Over the millennia, the gonococcus has likely evolved mechanisms to evade host defense systems that operate on the genital mucosal surfaces in both males and females. Past research has shown that the presence or modification of certain cell envelope structures can significantly impact levels of gonococcal susceptibility to host-derived antimicrobial compounds that bathe genital mucosal surfaces and participate in innate host defense against invading pathogens. In order to facilitate the identification of gonococcal genes that are important in determining levels of bacterial susceptibility to mediators of innate host defense, we used the Himar I mariner in vitro mutagenesis system to construct a transposon insertion library in strain F62. As proof of principle that this strategy would be suitable for this purpose, we screened the library for mutants expressing decreased susceptibility to the bacteriolytic action of normal human serum (NHS). We found that a transposon insertion in the lgtD gene, which encodes an N-acetylgalactosamine transferase involved in the extension of the α-chain of lipooligosaccharide (LOS), could confer decreased susceptibility of strain F62 to complement-mediated killing by NHS. By complementation and chemical analyses, we demonstrated both linkage of the transposon insertion to the NHS-resistance phenotype and chemical changes in LOS structure that resulted from loss of LgtD production. Further truncation of the LOS α-chain or loss of phosphoethanolamine (PEA) from the lipid A region of LOS also impacted levels of NHS-resistance. PEA decoration of lipid A also increased gonococcal resistance to the model cationic antimicrobial polymyxin B. Taken together, we conclude that the Himar I mariner in vitro mutagenesis procedure can facilitate studies on structures involved in gonococcal pathogenesis

Copper(II)-Bis(Thiosemicarbazonato) Complexes as Antibacterial Agents: Insights into Their Mode of Action and Potential as Therapeutics

There is increasing interest in the use of lipophilic copper (Cu)-containing complexes to combat bacterial infections. In this work, we showed that Cu complexes with bis(thiosemicarbazone) ligands [Cu(btsc)] exert antibacterial activity against a range of medically significant pathogens. Previous work using Neisseria gonorrhoeae showed that Cu(btsc) complexes may act as inhibitors of respiratory dehydrogenases in the electron transport chain. We now show that these complexes are also toxic against pathogens that lack a respiratory chain. Respiration in Escherichia coli was slightly affected by Cu(btsc) complexes, but our results indicate that, in this model bacterium, the complexes act primarily as agents that deliver toxic Cu ions efficiently into the cytoplasm. Although the chemistry of Cu(btsc) complexes may dictate their mechanism of action, their efficacy depends heavily on bacterial physiology. This is linked to the ability of the target bacterium to tolerate Cu and, additionally, the susceptibility of the respiratory chain to direct inhibition by Cu(btsc) complexes. The physiology of N. gonorrhoeae, including multidrug-resistant strains, makes it highly susceptible to damage by Cu ions and Cu(btsc) complexes, highlighting the potential of Cu(btsc) complexes (and Cu-based therapeutics) as a promising treatment against this important bacterial pathogen

Structure-Function Relationships of the Neisserial EptA Enzyme Responsible for Phosphoethanolamine Decoration of Lipid A: Rationale for Drug Targeting

Bacteria cause disease by two general mechanisms: the action of their toxins on host cells and induction of a pro-inflammatory response that can lead to a deleterious cytokine/chemokine response (e.g., the so-called cytokine storm) often seen in bacteremia/septicemia. These major mechanisms may overlap due to the action of surface structures that can have direct and indirect actions on phagocytic or non-phagocytic cells. In this respect, the lipid A (endotoxin) component of lipopolysaccharide (LPS) possessed by Gram-negative bacteria has been the subject of literally thousands of studies over the past century that clearly identified it as a key virulence factor in endotoxic shock. In addition to its capacity to modulate inflammatory responses, endotoxin can also modulate bacterial susceptibility to host antimicrobials, such as the host defense peptides termed cationic antimicrobial peptides. This review concentrates on the phosphoethanolamine (PEA) decoration of lipid A in the pathogenic species of the genus Neisseria [N. gonorrhoeae and N. meningitidis]. PEA decoration of lipid A is mediated by the enzyme EptA (formerly termed LptA) and promotes resistance to innate defense systems, induces the pro-inflammatory response and can influence the in vivo fitness of bacteria during infection. These important biological properties have driven efforts dealing with the biochemistry and structural biology of EptA that will facilitate the development of potential inhibitors that block PEA addition to lipid A

Nurses\u27 Alumnae Association Bulletin - Volume 7 Number 11

Anna M. Shafer Barton Memorial Division Births Changes in the Ophthalmology Division Change of Address Clara Melville Fund Continental Tour Deceased Digest of Meetings Inter-County Hospitalization Plan Katherine Childs\u27 Letter Lost Members Marriages Miscellaneous Nursing Home Committee\u27s Report Physical Advantages President James L. Kauffman\u27s Letter President\u27s Greeting Private Duty Section Prizes Relief Fund School Nursing Silhouette of a Public Health Nurse Rooming-in of Infant with Mother Staff Activities The Student White Haven Divisio

Nonoxidative antimicrobial effects of human polymorphonuclear leukocyte granule proteins on Chlamydia spp. in vitro.

Proteins from isolated granules of human polymorphonuclear leukocytes were assessed for their nonoxidative microbicidal effect on chlamydiae by two different methods: a radioisotope assay for elementary body integrity and a biological assay for inclusion development. Crude granule extract, which consisted of a mixture of all granule proteins, caused a 20 to 30% decrease in infectivity and a 52% decrease in infectivity when incubated with Chlamydia psittaci CAL-10 and Chlamydia trachomatis serovar E, respectively. To define more specifically the components that were damaging to chlamydiae, crude granule extract was subjected to Sephadex G-75 column chromatography and isolated granule fractions were obtained. Only fractions containing lysozyme as the major component consistently caused reductions in infectivity of C. trachomatis elementary bodies. In contrast, fractions collected after the lysozyme fraction, containing proteins with molecular masses of 13,000 daltons or less, had detrimental effects on C. psittaci infectivity. Additional experiments using highly purified human polymorphonuclear leukocyte lysozyme confirmed its infectivity-reducing action upon C. trachomatis but not upon C. psittaci