The mutational landscape of Staphylococcus aureus during colonisation.

Staphylococcus aureus is an important human pathogen and a commensal of the human nose and skin. Survival and persistence during colonisation are likely major drivers of S. aureus evolution.

PBP4 is required for serum-induced cell wall thickening and antibiotic tolerance in .

The bacterial pathogen responds to the host environment by synthesizing a thick peptidoglycan cell wall, which protects the bacterium from membrane-targeting antimicrobials and the immune response. However, the proteins required for this response were previously unknown. Here, we demonstrate by three independent approaches that the penicillin-binding protein PBP4 is crucial for serum-induced cell wall thickening.

Lipoteichoic acid biosynthesis by is controlled by the MspA protein.

produces a plethora of virulence factors critical to its ability to establish an infection and cause disease. We have previously characterized a small membrane protein, MspA, which has pleiotropic effects on virulence and contributes to pathogenicity . Here we report that inactivation triggers overaccumulation of the essential cell wall component, lipoteichoic acid (LTA), which, in turn, decreases autolytic activity and leads to increased cell size due to a delay in cell separation.

Extensive remodelling of the cell wall during the development of bacteraemia.

The bloodstream represents a hostile environment that bacteria must overcome to cause bacteraemia. To understand how the major human pathogen manages this we have utilised a functional genomics approach to identify a number of new loci that affect the ability of the bacteria to survive exposure to serum, the critical first step in the development of bacteraemia. The expression of one of these genes, was found to be induced upon exposure to serum, and we show that it is involved in the elaboration of a critical virulence factor, the wall teichoic acids (WTA), within the cell envelope.

A high-throughput cytotoxicity screening platform reveals -independent mutations in bacteraemia-associated that promote intracellular persistence.

infections are associated with high mortality rates. Often considered an extracellular pathogen, can persist and replicate within host cells, evading immune responses, and causing host cell death. Classical methods for assessing cytotoxicity are limited by testing culture supernatants and endpoint measurements that do not capture the phenotypic diversity of intracellular bacteria.

Extensive re-modelling of the cell wall during the development of bacteraemia.

The bloodstream represents a hostile environment that bacteria must overcome to cause bacteraemia. To understand how the major human pathogen manages this we have utilised a functional genomics approach to identify a number of new loci that affect the ability of the bacteria to survive exposure to serum, the critical first step in the development of bacteraemia. The expression of one of these genes, was found to be induced upon exposure to serum, and we show that it is involved in the elaboration of a critical virulence factor, the wall teichoic acids (WTA), within the cell envelope.

Triclosan-resistant small-colony variants of produce less capsule, less phenol-soluble modulins, and are attenuated in a model of infection.

In recent work we identified genes that confer the slow-growing and antibiotic-resistant small-colony variant (SCV) form of , as associated with the amount of capsule the bacteria produce. In this study we isolated a triclosan-resistant SCV (tr-SCV) and demonstrated that it produces significantly less capsule, an effect that appears to be mediated at the transcriptional stage. As with other SCVs, we found that the tr-SCV produces less toxins, and when compared to both a capsule and an Agr mutant we found the tr-SCV to be significantly attenuated in an insect model of infection.

Diagnostic MALDI-TOF MS can differentiate between high and low toxic bacteraemia isolates as a predictor of patient outcome.

bacteraemia (SAB) is a major cause of blood-stream infection (BSI) in both healthcare and community settings. While the underlying comorbidities of a patient significantly contributes to their susceptibility to and outcome following SAB, recent studies show the importance of the level of cytolytic toxin production by the infecting bacterium. In this study we demonstrate that this cytotoxicity can be determined directly from the diagnostic MALDI-TOF mass spectrum generated in a routine diagnostic laboratory.

Wall Teichoic Acids Facilitate the Release of Toxins from the Surface of Staphylococcus aureus.

A major feature of the pathogenicity of Staphylococcus aureus is its ability to secrete cytolytic toxins. This process involves the translocation of the toxins from the cytoplasm through the bacterial membrane and the cell wall to the external environment. The process of their movement through the membrane is relatively well defined, involving both general and toxin-specific secretory systems.

Targeted control of pneumolysin production by a mobile genetic element in .

is a major human pathogen that can cause severe invasive diseases such as pneumonia, septicaemia and meningitis. Young children are at a particularly high risk, with an estimated 3-4 million cases of severe disease and between 300 000 and 500 000 deaths attributable to pneumococcal disease each year. The haemolytic toxin pneumolysin (Ply) is a primary virulence factor for this bacterium, yet despite its key role in pathogenesis, immune evasion and transmission, the regulation of Ply production is not well defined.

Significant variability exists in the cytotoxicity of global methicillin-resistant lineages.

is a major human pathogen where the emergence of antibiotic resistant lineages, such as methicillin-resistant (MRSA), is a major health concern. While some MRSA lineages are restricted to the healthcare setting, the epidemiology of MRSA is changing globally, with the rise of specific lineages causing disease in healthy people in the community. In the past two decades, community-associated MRSA (CA-MRSA) has emerged as a clinically important and virulent pathogen associated with serious skin and soft-tissue infections (SSTI).

A functional menadione biosynthesis pathway is required for capsule production by .

is a major human pathogen that utilises a wide array of pathogenic and immune evasion strategies to cause disease. One immune evasion strategy, common to many bacterial pathogens, is the ability of to produce a capsule that protects the bacteria from several aspects of the human immune system. To identify novel regulators of capsule production by we applied a genome wide association study (GWAS) to a collection of 300 bacteraemia isolates that represent the two major MRSA clones in UK and Irish hospitals: CC22 and CC30.

The MpsB protein contributes to both the toxicity and immune evasion capacity of .

Understanding the role specific bacterial factors play in the development of severe disease in humans is critical if new approaches to tackle such infections are to be developed. In this study we focus on genes we have found to be associated with patient outcome following bacteraemia caused by the major human pathogen . By examining the contribution these genes make to the ability of the bacteria to survive exposure to the antibacterial factors found in serum, we identify three novel serum resistance-associated genes, , and .

Post-acute COVID-19 associated with evidence of bystander T-cell activation and a recurring antibiotic-resistant bacterial pneumonia.

Here, we describe the case of a COVID-19 patient who developed recurring ventilator-associated pneumonia caused by that acquired increasing levels of antimicrobial resistance (AMR) in response to treatment. Metagenomic analysis revealed the AMR genotype, while immunological analysis revealed massive and escalating levels of T-cell activation. These were both SARS-CoV-2 and specific, and bystander activated, which may have contributed to this patient's persistent symptoms and radiological changes.

A Small Membrane Stabilizing Protein Critical to the Pathogenicity of Staphylococcus aureus.

is a major human pathogen, and the emergence of antibiotic-resistant strains is making all types of infections more challenging to treat. With a pressing need to develop alternative control strategies to use alongside or in place of conventional antibiotics, one approach is the targeting of established virulence factors. However, attempts at this have had little success to date, suggesting that we need to better understand how this pathogen causes disease if effective targets are to be identified.

Evaluation of the effectiveness and acceptability of intramuscular clozapine injection: illustrative case series.

Aims And Method: A series of eleven patients prescribed intramuscular clozapine at five UK sites is presented. Using routinely collected clinical data, we describe the use, efficacy and safety of this treatment modality.

Results: We administered 188 doses of intramuscular clozapine to eight patients.

Timing Is Everything: Impact of Naturally Occurring AgrC Cytoplasmic Domain Adaptive Mutations on Autoinduction.

Mutations in the polymorphic locus responsible for quorum sensing (QS)-dependent virulence gene regulation occur frequently during host adaptation. In two genomically closely related clinical isolates exhibiting marked differences in Panton-Valentine leukocidin production, a mutation conferring an N267I substitution was identified in the cytoplasmic domain of the QS sensor kinase, AgrC. This natural mutation delayed the onset and accumulation of autoinducing peptide (AIP) and showed reduced responsiveness to exogenous AIPs.

Disease-associated genotypes of the commensal skin bacterium Staphylococcus epidermidis.

Some of the most common infectious diseases are caused by bacteria that naturally colonise humans asymptomatically. Combating these opportunistic pathogens requires an understanding of the traits that differentiate infecting strains from harmless relatives. Staphylococcus epidermidis is carried asymptomatically on the skin and mucous membranes of virtually all humans but is a major cause of nosocomial infection associated with invasive procedures.

Genomic exploration of sequential clinical isolates reveals a distinctive molecular signature of persistent Staphylococcus aureus bacteraemia.

Background: Large-scale genomic studies of within-host diversity in Staphylococcus aureus bacteraemia (SAB) are needed to understanding bacterial adaptation underlying persistence and thus refining the role of genomics in management of SAB. However, available comparative genomic studies of sequential SAB isolates have tended to focus on selected cases of unusually prolonged bacteraemia, where secondary antimicrobial resistance has developed.

Methods: To understand bacterial genetic diversity during SAB more broadly, we applied whole genome sequencing to a large collection of sequential isolates obtained from patients with persistent or relapsing bacteraemia.

Epistasis analysis uncovers hidden antibiotic resistance-associated fitness costs hampering the evolution of MRSA.

Background: Fitness costs imposed on bacteria by antibiotic resistance mechanisms are believed to hamper their dissemination. The scale of these costs is highly variable. Some, including resistance of Staphylococcus aureus to the clinically important antibiotic mupirocin, have been reported as being cost-free, which suggests that there are few barriers preventing their global spread.

Severe infections emerge from commensal bacteria by adaptive evolution.

Bacteria responsible for the greatest global mortality colonize the human microbiota far more frequently than they cause severe infections. Whether mutation and selection among commensal bacteria are associated with infection is unknown. We investigated de novo mutation in 1163 genomes from 105 infected patients with nose colonization.