Unravelling the mechanisms causing murepavadin resistance in : lipopolysaccharide alterations and its consequences.

Introduction: Murepavadin is an antimicrobial peptide (AMP) in clinical development that selectively targets LptD and whose resistance profile remains unknown. We aimed to explore genomic modifications and consequences underlying murepavadin and/or colistin susceptibility.

Methods: To define genomic mechanisms underlying resistance, we performed two approaches: 1) a genome-wide association study (GWAS) in a clinical collection (n=496), considering >0.

A highly-safe live auxotrophic vaccine protecting against disease caused by non-typhoidal Salmonella Typhimurium in mice.

Background: Salmonella enterica serovar Typhimurium (S. Typhimurium) has become an important intestinal pathogen worldwide and is responsible for lethal invasive infections in populations at risk. There is at present an unmet need for preventive vaccines.

Comparison of the in vivo efficacy of ceftaroline fosamil, vancomycin and daptomycin in a murine model of methicillin-resistant Staphylococcus aureus bacteraemia.

The need for alternative drugs to treat methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia has led to a focus on ceftaroline, for which clinical data remain scarce. Herein, the efficacy of ceftaroline fosamil for the treatment of experimental MRSA bacteraemia was compared with that of approved therapies. Five MRSA strains were tested in an immunocompetent BALB/c bacteraemia model.

Cross-Protection against Acute Lung Infection in Mice by a D-Glutamate Auxotrophic Vaccine Candidate.

is regarded as a threatening bacterial pathogen causing invasive pneumonia in healthcare settings and in the community. The continuous emergence of multidrug resistant strains is narrowing the treatment options for these infections. The development of an effective vaccine is, therefore, a global priority.

Double Auxotrophy to Improve the Safety of a Live Anti- Vaccine.

is an opportunistic nosocomial pathogen that causes serious infections in the respiratory tract of immunocompromised or critically ill patients, and it is also a significant source of bacteremia. Treatment of these infections can be complicated due to the emergence of multidrug-resistant strains worldwide. Hence, the development of prophylactic vaccines is a priority for at-risk patients.

A New Live Auxotrophic Vaccine Induces Cross-Protection against Infections in Mice.

The development of a whole-cell vaccine from bacteria auxotrophic for D-amino acids present in the bacterial cell wall is considered a promising strategy for providing protection against bacterial infections. Here, we constructed a prototype vaccine, consisting of a glutamate racemase-deficient mutant, for preventing infections. The deletion mutant lacks the gene and requires exogenous addition of D-glutamate for growth.

In vitro and in vivo efficacy of combinations of colistin and different endolysins against clinical strains of multi-drug resistant pathogens.

The emergence of multidrug resistant (MDR) pathogenic bacteria is jeopardizing the value of antimicrobials, which had previously changed the course of medical science. In this study, we identified endolysins ElyA1 and ElyA2 (GH108-PG3 family), present in the genome of bacteriophages Ab1051Φ and Ab1052Φ, respectively. The muralytic activity of these endolysins against MDR clinical isolates (Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae) was tested using the turbidity reduction assay.

A live auxotrophic vaccine confers mucosal immunity and protection against lethal pneumonia caused by Pseudomonas aeruginosa.

Pseudomonas aeruginosa is one of the leading causes of nosocomial pneumonia and its associated mortality. Moreover, extensively drug-resistant high-risk clones are globally widespread, presenting a major challenge to the healthcare systems. Despite this, no vaccine is available against this high-concerning pathogen.

The and Toxin-Antitoxin Operons Participate in Oxidative Stress and Biofilm Formation.

Type II (proteic) toxin-antitoxin systems (TAs) are widely distributed among bacteria and archaea. They are generally organized as operons integrated by two genes, the first encoding the antitoxin that binds to its cognate toxin to generate a harmless protein⁻protein complex. Under stress conditions, the unstable antitoxin is degraded by host proteases, releasing the toxin to achieve its toxic effect.

A D-Alanine auxotrophic live vaccine is effective against lethal infection caused by Staphylococcus aureus.

Staphylococcus aureus infections are becoming a major global health issue due to the rapid emergence of multidrug-resistant strains. Therefore, there is an urgent need to develop an effective vaccine to prevent and control these infections. In order to develop a universal immunization strategy, we constructed a mutant derivative of S.

Design of live attenuated bacterial vaccines based on D-glutamate auxotrophy.

Vaccine development is a priority for global health due to the growing multidrug resistance in bacteria. D-glutamate synthesis is essential for bacterial cell wall formation. Here we present a strategy for generating effective bacterial whole-cell vaccines auxotrophic for D-glutamate.

In vitro biofilm development of Streptococcus pneumoniae and formation of choline-binding protein-DNA complexes.

Extracellular deoxyribonucleic acid (eDNA) is an essential component of bacterial biofilm matrices, and is required in their formation and maintenance. Extracellular DNA binds to exopolysaccharides or extracellular proteins, affording biofilms greater structural integrity. Recently, we reported evidence of intercellular eDNA-LytC complexes in pneumococcal biofilms.

Pleiotropic effects of cell wall amidase LytA on Streptococcus pneumoniae sensitivity to the host immune response.

The complement system is a key component of the host immune response for the recognition and clearance of Streptococcus pneumoniae. In this study, we demonstrate that the amidase LytA, the main pneumococcal autolysin, inhibits complement-mediated immunity independently of effects on pneumolysin by a complex process of impaired complement activation, increased binding of complement regulators, and direct degradation of complement C3. The use of human sera depleted of either C1q or factor B confirmed that LytA prevented activation of both the classical and alternative pathways, whereas pneumolysin inhibited only the classical pathway.

In vitro bactericidal and bacteriolytic activity of ceragenin CSA-13 against planktonic cultures and biofilms of Streptococcus pneumoniae and other pathogenic streptococci.

Ceragenin CSA-13, a cationic steroid, is here reported to show a concentration-dependent bactericidal/bacteriolytic activity against pathogenic streptococci, including multidrug-resistant Streptococcus pneumoniae. The autolysis promoted by CSA-13 in pneumococcal cultures appears to be due to the triggering of the major S. pneumoniae autolysin LytA, an N-acetylmuramoyl-L-alanine amidase.

Frequent carriage of resistance mechanisms to β-lactams and biofilm formation in Haemophilus influenzae causing treatment failure and recurrent otitis media in young children.

Objectives: Non-typeable Haemophilus influenzae are a major cause of acute otitis media (AOM), including chronic and recurrent otitis in young children. The objective of this study was to determine whether non-typeable H. influenzae isolates causing these infections produce biofilms and carry resistance mechanisms to β-lactams.

In vitro biofilm formation by Streptococcus pneumoniae as a predictor of post-vaccination emerging serotypes colonizing the human nasopharynx.

The increasing use of the 7-valent pneumococcal conjugate vaccine has been accompanied by the rise of non-vaccine serotypes colonizing the human nasopharynx. The vast majority of infections are caused by microorganisms that grow in biofilms. It has recently been shown that the formation of Streptococcus pneumoniae biofilms in vivo and in vitro is hindered by the presence of capsular polysaccharide.

Biofilm formation avoids complement immunity and phagocytosis of Streptococcus pneumoniae.

Streptococcus pneumoniae is a frequent member of the microbiota of the human nasopharynx. Colonization of the nasopharyngeal tract is a first and necessary step in the infectious process and often involves the formation of sessile microbial communities by this human pathogen. The ability to grow and persist as biofilms is an advantage for many microorganisms, because biofilm-grown bacteria show reduced susceptibility to antimicrobial agents and hinder recognition by the immune system.

Insight into the composition of the intercellular matrix of Streptococcus pneumoniae biofilms.

Biofilm matrices consist of a mixture of extracellular polymeric substances synthesized in large part by the biofilm-producing microorganisms themselves. These matrices are responsible for the cohesion and three-dimensional architecture of biofilms. The present study demonstrates the existence of a matrix composed of extracellular DNA, proteins and polysaccharides in the biofilm formed by the human pathogen Streptococcus pneumoniae.

Vancomycin tolerance in Gram-positive cocci.

Vancomycin, a glycopeptide antimicrobial agent, represents the last line of defence against a wide range of multi-resistant Gram-positive pathogens such as enterococci, staphylococci and streptococci. However, vancomycin-resistant enterococci and staphylococci, along with vancomycin-tolerant clinical isolates, are compromising the therapeutic efficacy of vancomycin. It is conceivable that tolerance may emerge during prolonged vancomycin use.

Biofilm formation in Streptococcus pneumoniae.

Biofilm-grown bacteria are refractory to antimicrobial agents and show an increased capacity to evade the host immune system. In recent years, studies have begun on biofilm formation by Streptococcus pneumoniae, an important human pathogen, using a variety of in vitro model systems. The bacterial cells in these biofilms are held together by an extracellular matrix composed of DNA, proteins and, possibly, polysaccharide(s).

Nasopharyngeal colonization and invasive disease are enhanced by the cell wall hydrolases LytB and LytC of Streptococcus pneumoniae.

Background: Streptococcus pneumoniae is a common colonizer of the human nasopharynx and one of the major pathogens causing invasive disease worldwide. Dissection of the molecular pathways responsible for colonization, invasion, and evasion of the immune system will provide new targets for antimicrobial or vaccine therapies for this common pathogen.

Methodology/principal Findings: We have constructed mutants lacking the pneumococcal cell wall hydrolases (CWHs) LytB and LytC to investigate the role of these proteins in different phases of the pneumococcal pathogenesis.

In vitro destruction of Streptococcus pneumoniae biofilms with bacterial and phage peptidoglycan hydrolases.

Host- and phage-coded cell wall hydrolases have been used to fight Streptococcus pneumoniae growing as planktonic cells in vitro as well as in animal models. Until now, however, the usefulness of these enzymes in biofilm-grown pneumococci has gone untested. The antipneumococcal activity of different cell wall hydrolases produced by S.

Vancomycin tolerance in clinical and laboratory Streptococcus pneumoniae isolates depends on reduced enzyme activity of the major LytA autolysin or cooperation between CiaH histidine kinase and capsular polysaccharide.

Vancomycin is frequently added to standard therapy for pneumococcal meningitis. Although vancomycin-resistant Streptococcus pneumoniae strains have not been isolated, reports on the emergence of vancomycin-tolerant pneumococci are a cause of concern. To date, the molecular basis of vancomycin tolerance in S.

Pneumococcal biofilms.

Over 60% of bacterial infections (and up to 80% of chronic infections) are currently considered to involve microbial growth in biofilms. This peculiar form of life poses an array of problems in human clinical practice, from infections associated with the implant of prosthetic devices and dental plaque formation to diseases such as cystic fibrosis, otitis media, and endocarditis. Biofilms are also at the basis of a variety of problems in industry.

Versatility of the capsular genes during biofilm formation by Streptococcus pneumoniae.

Streptococcus pneumoniae forms part of the natural microbiota of the nasopharynx. For the pneumococcus to cause infection, colonization needs to occur and this process is mediated by adherence of bacteria to the respiratory epithelium. Although the capsular polysaccharide (CPS) of S.