Staphylococcus epidermidis isolated from newborn infants express pilus-like structures and are inhibited by the cathelicidin-derived antimicrobial peptide LL37

Sequencing a CC239-MRSA-III with a novel composite SCC mec element from Kuwait

Staphylococcus aureus CC239-MRSA-III is an ancient pandemic strain of hospital-associated, methicillin-resistant S. aureus that spread globally for decades and that still can be found in some parts of the world. In Kuwait, microarray-based surveillance identified from 2019 to 2022 a series of isolates of a hitherto unknown variant of this strain that carried a second set of recombinase genes, ccrA/B-2. To elucidate the structure of its SCCmec element, two isolates were subjected to nanopore sequencing. This revealed, in addition to ccrA/B-2, several SCC-associated genes including speG (spermidine N acetyltransferase) and a gene encoding a large "E-domain containing protein" (dubbed as edcP-SCC). This gene contained three regions consisting of multiple repeating units. In terms of sequence and structure it was similar but not identical to the biofilm-related aap gene from S. epidermidis. A review of published sequences identified edcP-SCC in eighteen genome sequences of S. aureus, S. epidermidis and S. capitis, and frequently it appears in a similar cluster of genes as in the strains sequenced herein. Isolates also carried a prophage with the adhesion factor sasX/sesI and aminoglycoside resistance genes. This is consistent with an affiliation to the "South-East Asian" Clade of CC239. The emergence of edcP-SCC and sasX-positive CC239 strain shows that, against a global trend towards community-associated MRSA, the ancient pandemic CC239 hospital strain still continues to evolve and to cause outbreaks.

Quantifying the Dynamics of Bacterial Biofilm Formation on the Surface of Soft Contact Lens Materials Using Digital Holographic Tomography to Advance Biofilm Research

The increase in bacterial resistance to antibiotics in recent years demands innovative strategies for the detection and combating of biofilms, which are notoriously resilient. Biofilms, particularly those on contact lenses, can lead to biofilm-related infections (e.g., conjunctivitis and keratitis), posing a significant risk to patients. Non-destructive and non-contact sensing techniques are essential in addressing this threat. Digital holographic tomography emerges as a promising solution. This allows for the 3D reconstruction of the refractive index distribution in biological samples, enabling label-free visualization and the quantitative analysis of biofilms. This tool provides insight into the dynamics of biofilm formation and maturation on the surface of transparent materials. Applying digital holographic tomography for biofilm examination has the potential to advance our ability to combat the antibiotic bacterial resistance crisis. A recent study focused on characterizing biofilm formation and maturation on six soft contact lens materials (three silicone hydrogels, three hydrogels), with a particular emphasis on Staphylococcus epidermis and Pseudomonas aeruginosa, both common culprits in ocular infections. The results revealed species- and time-dependent variations in the refractive indexes and volumes of biofilms, shedding light on cell dynamics, cell death, and contact lens material-related factors. The use of digital holographic tomography enables the quantitative analysis of biofilm dynamics, providing us with a better understanding and characterization of bacterial biofilms.

Antimicrobial Peptides in Early-Life Host Defense, Perinatal Infections, and Necrotizing Enterocolitis—An Update

Host defense against early-life infections such as chorioamnionitis, neonatal sepsis, or necrotizing enterocolitis (NEC) relies primarily on innate immunity, in which antimicrobial peptides (AMPs) play a major role. AMPs that are important for the fetus and neonate include α and β defensins, cathelicidin LL-37, antiproteases (elafin, SLPI), and hepcidin. They can be produced by the fetus or neonate, the placenta, chorioamniotic membranes, recruited neutrophils, and milk-protein ingestion or proteolysis. They possess antimicrobial, immunomodulating, inflammation-regulating, and tissue-repairing properties. AMPs are expressed as early as the 13th week and increase progressively through gestation. Limited studies are available on AMP expression and levels in the fetus and neonate. Nevertheless, existing evidence supports the role of AMPs in pathogenesis of chorioamnionitis, neonatal sepsis, and NEC, and their association with disease severity. This suggests a potential role of AMPs in diagnosis, prevention, prognosis, and treatment of sepsis and NEC. Herein, we present an overview of the antimicrobial and immunomodulating properties of human AMPs, their sources in the intrauterine environment, fetus, and neonate, and their changes during pre- and post-natal infections and NEC. We also discuss emerging data regarding the potential utility of AMPs in early-life infections, as diagnostic or predictive biomarkers and as therapeutic alternatives or adjuncts to antibiotic therapy considering the increase of antibiotic resistance in neonatal intensive care units.

Evidence for cutaneous dysbiosis in dystrophic epidermolysis bullosa

BACKGROUND

The human microbiome project addresses the relationship between bacterial flora and the human host, in both healthy and diseased conditions. The skin is an ecosystem with multiple niches, each featuring unique physiological conditions and thus hosting different bacterial populations. The skin microbiome has been implicated in the pathogenesis of many dermatoses. Given the role of dysbiosis in the pathogenesis of inflammation, which is prominent in dystrophic epidermolysis bullosa (DEB), we undertook a study on the skin microbiome.

AIM

To characterize the skin microbiome in a series of patients with DEB.

METHODS

This was a case-control study of eight patients with DEB and nine control cases enrolled between June 2017 and November 2018. The skin of patients with DEB was sampled at three different sites: untreated wound, perilesional skin and normal-appearing (uninvolved) skin. Normal skin on the forearm was sampled from age-matched healthy controls (HCs). We used a dedicated DNA extraction protocol to isolate microbial DNA, which was then analysed using next-generation microbial 16S rRNA sequencing. Data were analysed using a series of advanced bioinformatics tools.

RESULTS

The wounds, perilesional and uninvolved skin of patients with DEB demonstrated reduced bacterial diversity compared with HCs, with the flora in DEB wounds being the least diverse. We found an increased prevalence of staphylococci species in the lesional and perilesional skin of patients with DEB, compared with their uninvolved, intact skin. Similarly, the uninvolved skin of patients with DEB displayed increased staphylococcal content and significantly different microbiome diversities (other than staphylococci) compared with HC skin.

CONCLUSIONS

These findings suggest the existence of a unique DEB-associated skin microbiome signature, which could be targeted by specific pathogen-directed therapies. Moreover, altering the skin microbiome with increasing colonization of bacteria associated with nonchronic wounds may potentially facilitate wound healing in patients with DEB.

Development of anti-bacterial surfaces using a hydrophobin chimeric protein

The search for new approaches for developing antimicrobial surfaces is a challenge of great urgency to prevent and control microbial growth on surfaces. The strategy herein proposed relies on the design of a new, simple and general tool for creating antimicrobial surfaces, based on a hydrophobin chimeric protein which fuses the adhesive self-assembling class I hydrophobin Vmh2 from Pleurotus ostreatus to the human antimicrobial peptide LL-37. The recombinant LL37-Vmh2 protein displayed both the adhesive and the antimicrobic properties of its members, and when deposited on polystyrene surface, a positive effect due to the fusion was observed in terms of both efficacy and versatility of the coating. Indeed, the chimeric protein significantly enlarges the range of pathogens affected by Vmh2 layer rendering it able to inhibit three Gram-positive and two Gram-negative pathogens, selected among the renowned biofilm producer bacteria. Confocal Laser Scanning Microscopy analysis performed on Staphylococcus epidermidis biofilms formed on coated surfaces proved that, besides inhibiting biofilm formation, the LL37-Vmh2 coating also displayed biocidal activity, since dead cells were present in the biofilm layer. The reported results open new perspectives in various fields of application of LL37, and of antimicrobial peptides in general. LL37-Vmh2 increases the inventory of chimeric hydrophobins, further proving their effectiveness and versatility in surface functionalization.

Probiotic Supplementation During the Perinatal and Infant Period: Effects on Gut Dysbiosis and Disease

The perinatal period is crucial to the establishment of lifelong gut microbiota. The abundance and composition of microbiota can be altered by several factors such as preterm delivery, formula feeding, infections, antibiotic treatment, and lifestyle during pregnancy. Gut dysbiosis affects the development of innate and adaptive immune responses and resistance to pathogens, promoting atopic diseases, food sensitization, and infections such as necrotizing enterocolitis (NEC). Recent studies have indicated that the gut microbiota imbalance can be restored after a single or multi-strain probiotic supplementation, especially mixtures of Lactobacillus and Bifidobacterium strains. Following the systematic search methodology, the current review addresses the importance of probiotics as a preventive or therapeutic tool for dysbiosis produced during the perinatal and infant period. We also discuss the safety of the use of probiotics in pregnant women, preterm neonates, or infants for the treatment of atopic diseases and infections.

LL-37 fragments have antimicrobial activity against Staphylococcus epidermidis biofilms and wound healing potential in HaCaT cell line

Staphylococcus epidermidis is a common nosocomial pathogen able to form biofilms in indwelling devices, resulting in chronic infections, which are refractory to antibiotics treatment. Staphylococcal biofilms are also associated with the delayed reepithelization and healing of chronic wounds. The human cathelicidin peptide LL-37 has been proven active against S. epidermidis biofilms in vitro and to promote wound healing. As previous studies have demonstrated that fragments of LL-37 could possess an equal antibacterial activity as the parent peptide, we tested whether shorter (12-mer) synthetic fragments of LL-37 maintained the antibiofilm and/or immune modulating activity, aiming at the identification of essential regions within the LL-37 parent sequence. Three fragments of LL-37 displayed improved activity against S. epidermidis in terms of biofilm inhibition and eradication, a reduced cytotoxicity to human keratinocytes and erythrocytes. In addition, KR-12 and VQ-12^V26 enhanced wound healing potential, relative to LL37. FK-12 and KR-12 are truncated version of the cathelicidin, previously reported as valid antimicrobials, whereas VQ-12^V26 is a single substituted LL-37 fragment. Remarkably, the single substitution aspartic acid to valine in position 26 caused gain of antimicrobial function in the inactive VQ-12 fragment. The combination of antibiofilm, wound healing potential, and low cytotoxicity makes KR-12 and VQ-12^V26 promising therapeutic agents and lead compounds for further improvement and understanding of antibiofilm and wound healing properties.

The role of the microbiome in psoriasis: moving from disease description to treatment selection?

BACKGROUND

With several million microbes per square centimetre of skin, the task of mapping the physiological cutaneous microbiome is enormous. Indeed, the reliance on bacterial culture to identify cutaneous bacterial communities has led to a systematic underappreciation of cutaneous microbial diversity, potentially limiting our understanding of common inflammatory skin diseases, including psoriasis. However, based heavily on developments in molecular biology and bioinformatics, including next-generation sequencing, the last decade has witnessed a marked increase in our understanding of the extent and composition of the cutaneous microbiome. It is already clear that skin-specific (skin site and skin microenvironment), individual-specific (hygiene, sex, age and hormonal status), disease-specific (atopic eczema, acne) and genetic factors can all influence the cutaneous microbiome, albeit to varying and, as yet, ill-defined extents.

OBJECTIVES

To investigate the role of the microbiome in psoriasis and to outline how microbiome studies can be harnessed to provide new insights into disease pathogenesis and treatment selection.

METHODS

This review briefly describes the process of 16S ribosomal RNA sequencing and then charts our current understanding of the cutaneous microbiome in health and the alterations (dysbiosis) associated with chronic inflammatory diseases, with particular reference to psoriasis.

RESULTS

The possibility and clinical relevance of intraindividual cross-talk between the various microbiomes is discussed and potential mechanisms underpinning the interactions between resident skin flora and the immune system are highlighted.

CONCLUSIONS

Ultimately, in the age of personalized medicine, the integration of cutaneous microbiome signatures and comprehensive disease and drug response endotypes will herald a novel approach in the clinical management of chronic multisystem inflammatory diseases.

Antimicrobial Proteins and Peptides in Early Life: Ontogeny and Translational Opportunities

While developing adaptive immune responses, young infants are especially vulnerable to serious infections, including sepsis, meningitis, and pneumonia. Antimicrobial proteins and peptides (APPs) are key effectors that function as broad-spectrum anti-infectives. This review seeks to summarize the clinically relevant functional qualities of APPs and the increasing clinical trial evidence for their use to combat serious infections in infancy. Levels of APPs are relatively low in early life, especially in infants born preterm or with low birth weight (LBW). There are several rationales for the potential clinical utility of APPs in the prevention and treatment of infections in infants: (a) APPs may be most helpful in those with reduced levels; (b) during sepsis microbial products signal via pattern recognition receptors causing potentially harmful inflammation that APPs may counteract; and (c) in the era of antibiotic resistance, development of new anti-infective strategies is essential. Evidence supports the potential clinical utility of exogenous APPs to reduce infection-related morbidity in infancy. Further studies should characterize the ontogeny of antimicrobial activity in mucosal and systemic compartments, and examine the efficacy of exogenous-APP formulations to inform translational development of APPs for infant groups.

Functions of Cationic Host Defense Peptides in Immunity

Cationic host defense peptides are a widely distributed family of immunomodulatory molecules with antimicrobial properties. The biological functions of these peptides include the ability to influence innate and adaptive immunity for efficient resolution of infections and simultaneous modulation of inflammatory responses. This unique dual bioactivity of controlling infections and inflammation has gained substantial attention in the last three decades and consequent interest in the development of these peptide mimics as immunomodulatory therapeutic candidates. In this review, we summarize the current literature on the wide range of functions of cationic host defense peptides in the context of the mammalian immune system.

Contribution of microbiota to the intestinal physicochemical barrier

The large number of intestinal microorganisms, which exceeds the total number of human cells by ten folds, alludes to a significant contribution to human health. This is vivid in enteric and some systemic diseases emanating from disruption of the microbiota. As life style keeps shifting towards disruption of the microbiota in most societies worldwide, interest in the contribution of the microbiota to gut health has grown enormously. Many studies have been conducted to elucidate the exact contribution of the microbiota to human health. The knowledge gained from these studies indicates that the microbiota interacts with the intestinal milieu to maintain gut health. In this review, the crosstalk of microbiota with the intestinal physicochemical barrier pivotal to the gut innate immunity is highlighted. In particular, the review focuses on the role of the microbiota on competitive exclusion of pathogens, intestinal pH, epithelial mechanical barrier integrity, apical actin cytoskeleton, antimicrobial peptides, and the mucus layer. Understanding this microbe-host relationship will provide useful insight into overcoming some diseases related to the disruption of the host microbiota.

Cathelicidin-like helminth defence molecules (HDMs): absence of cytotoxic, anti-microbial and anti-protozoan activities imply a specific adaptation to immune modulation

Host defence peptides (HDPs) are expressed throughout the animal and plant kingdoms. They have multifunctional roles in the defence against infectious agents of mammals, possessing both bactericidal and immune-modulatory activities. We have identified a novel family of molecules secreted by helminth parasites (helminth defence molecules; HDMs) that exhibit similar structural and biochemical characteristics to the HDPs. Here, we have analyzed the functional activities of four HDMs derived from Schistosoma mansoni and Fasciola hepatica and compared them to human, mouse, bovine and sheep HDPs. Unlike the mammalian HDPs the helminth-derived HDMs show no antimicrobial activity and are non-cytotoxic to mammalian cells (macrophages and red blood cells). However, both the mammalian- and helminth-derived peptides suppress the activation of macrophages by microbial stimuli and alter the response of B cells to cytokine stimulation. Therefore, we hypothesise that HDMs represent a novel family of HDPs that evolved to regulate the immune responses of their mammalian hosts by retaining potent immune modulatory properties without causing deleterious cytotoxic effects.

In mammals, secreted host defence peptides (HDPs) protect against a wide range of infectious pathogens. They also perform a range of immune modulatory functions which regulate the immune response to pathogens, ensuring that the protective inflammatory response is not exacerbated and that post-infection repair mechanisms are initiated. We identified a novel family of molecules secreted by medically-important helminth pathogens (termed helminth defence molecules; HDMs) that exhibit striking structural and biochemical similarities to the HDPs. To further investigate the extent of this similarity, we have performed a comparative functional study between several well characterized, anti-microbial, mammalian HDPs and a series of parasite-derived peptides. The parasite HDMs displayed immune modulatory properties that were similar to their HDP homologs in mammals, but possessed no antimicrobial or cytotoxic activity. We propose that HDMs of these helminth pathogens underwent specific adaptation, losing their anti-microbial activity but retaining their ability to regulate the immune responses of their mammalian hosts. This absence of cytotoxicity and retention of immune-modulatory activity offers an opportunity to design novel immunotherapeutics derived from the HDMs which could be used to combat destructive inflammatory responses associated with microbial infection and immune-related disorders.

Human cathelicidin LL-37 prevents bacterial biofilm formation

Human pathogens often colonize their host by the formation of biofilms. These surface-attached aggregates of bacteria are characterized by a self-produced extracellular matrix, which makes them highly resistant towards antibiotic treatment. Their abilities to adhere to abiotic surfaces (e.g., catheters and other medical devices) also makes bacterial biofilm formation a challenge in modern medicine. Antimicrobial peptides have lately been introduced as a potential class of drug molecules for combating severe hospital-acquired infections. One of these peptides, human cathelicidin LL-37, has recently been demonstrated to bridge innate and adaptive host defence, in addition to facilitating a robust antibiofilm effect at sub-inhibitory concentrations. In this review we will discuss the evidence, potential and challenges for LL-37 as a candidate molecule for therapeutic use.

Microbiology of the skin and the role of biofilms in infection

The integrity of human skin is central to the prevention of infection. Acute and chronic wounds can develop when the integrity of skin as a barrier to infection is disrupted. As a multi-functional organ, skin possesses important biochemical and physical properties that influence its microbiology. These properties include a slightly acidic pH, a low moisture content, a high lipid content (which results in increased hydrophobicity) and the presence of antimicrobial peptides. Such factors have a role to play in preventing exogenous microbial colonisation and subsequent infection. In addition, the properties of skin both select for and enhance colonisation and biofilm formation by certain 'beneficial' micro-organisms. These beneficial micro-organisms can provide further protection against colonisation by potential pathogens, a process known as colonisation resistance. The aim of this paper is to summarise the microflora of skin and wounds, highlighting the role of certain micro-organisms and biofilms in associated infections.

Purification and structural characterization of a novel antibacterial peptide from Bellamya bengalensis: activity against ampicillin and chloramphenicol resistant Staphylococcus epidermidis

Increasing tendency of clinical bacterial strains resistant to conventional antibiotics has being a great challenge to the public's health. Antimicrobial peptides, a new class of antibiotics is known to have the activity against a wide range of bacteria resistant to conventional antibiotics. An antimicrobial peptide of 1676 Da was purified from Bellamya bengalensis, a fresh water snail, using ultrafiltration and reversed phase liquid chromatography. The effect of this peptide on Staphylococcus epidermidis resistant to ampicillin and chloramphenicol was investigated; the MIC and MBC values were 8 μg/ml and 16 μg/ml, respectively. Complete sequence of the peptide was determined by tandem mass spectrometry (MS/MS). Further, peptide net charge, hydrophobicity and molecular modeling were evaluated in silico for better understanding the probable mechanisms of action. The peptide showed the specificity to bacterial membranes. Hence, this reported peptide revealed a promising candidate to contribute in the development of therapeutic agent for Staphylococcal infections.

Maternal plasma level of antimicrobial peptide LL37 is a major determinant factor of neonatal plasma LL37 level

AIM

To determine cathelicidin antimicrobial peptide LL37subcellular distribution in cord neutrophils and normal plasma LL37 levels in mothers and neonates, relate them to delivery mode and relevant biochemical markers, including 25-OHvitamin D [25(OH)D] as this molecules increases cathelicidin gene expression.

METHODS

A total of 115 infants were included, n = 68 with normal delivery and n = 47 with elective Caesarean section (C-section), a subset of these being 50 mother-infant pairs. Biomarkers were determined in maternal and cord blood. Subcellular peptide LL37 distribution was analysed with immunoelectron microscopy.

RESULTS

Cord plasma LL37 levels were three-times higher after normal delivery compared with C-section. A highly significant correlation was observed between maternal and cord plasma LL37 levels, regardless of delivery mode. No relationship was found between LL37 and 25(OH)D levels. Neutrophils from cord blood after normal delivery contained 10-times more cytoplasmatic cathelicidin peptide compared with corresponding cells after C-section where a strict granular localization was found.

CONCLUSION

These data are consistent with a placental transfer of LL37 and identifies maternal stores as the critical factor determining neonatal plasma LL37 level. An additional enhancement of neonatal cathelicidin mobilization and release is connected to normal delivery stress.