Pathogenic Mechanisms and Host Interactions in Staphylococcus epidermidis Device-Related Infection

Wild-type Caenorhabditis elegans isolates exhibit distinct gene expression profiles in response to microbial infection

The soil-dwelling nematode Caenorhabditis elegans serves as a model system to study innate immunity against microbial pathogens. C. elegans have been collected from around the world, where they, presumably, adapted to regional microbial ecologies. Here we use survival assays and RNA-sequencing to better understand how two isolates from disparate climates respond to pathogenic bacteria. We found that, relative to N2 (originally isolated in Bristol, UK), CB4856 (isolated in Hawaii), was more susceptible to the Gram-positive microbe, Staphylococcus epidermidis, but equally susceptible to Staphylococcus aureus as well as two Gram-negative microbes, Providencia rettgeri and Pseudomonas aeruginosa. We performed transcriptome analysis of infected worms and found gene-expression profiles were considerably different in an isolate-specific and microbe-specific manner. We performed GO term analysis to categorize differential gene expression in response to S. epidermidis. In N2, genes that encoded detoxification enzymes and extracellular matrix proteins were significantly enriched, while in CB4856, genes that encoded detoxification enzymes, C-type lectins, and lipid metabolism proteins were enriched, suggesting they have different responses to S. epidermidis, despite being the same species. Overall, discerning gene expression signatures in an isolate by pathogen manner can help us to understand the different possibilities for the evolution of immune responses within organisms.

Prevention, inhibition, and degradation effects of melittin alone and in combination with vancomycin and rifampin against strong biofilm producer strains of methicillin-resistant Staphylococcus epidermidis

Methicillin-resistant Staphylococcus epidermidis (MRSE) bacteria are being recognized as true pathogens as they are able to resist methicillin and commonly form biofilms. Recent studies have shown that antimicrobial peptides (AMPs) are promising agents against biofilm-associated bacterial infections. In this study, we aimed to explore the antibiofilm activity of melittin, either alone or in combination with vancomycin and rifampin, against biofilm-producing MRSE strains. Minimum biofilm preventive concentration (MBPC), minimum biofilm inhibition concentration (MBIC), and minimum biofilm eradication concentration (MBEC), as well as fractional biofilm preventive-, inhibitory-, and eradication concentrations (FBPCi, FBICi, and FBECi), were determined for the antimicrobial agents tested. Cytotoxicity and hemolytic activity of melittin at its synergistic concentration were examined on human embryonic kidney cells (HEK-293) and Red Blood Cells (RBCs), respectively. The effect of melittin on the downregulation of biofilm-associated genes was explored using Real-Time PCR. MBPC, MBIC, and MBEC values for melittin were in the range of 0.625-20, 0.625-20, and 10-40 μg/μL, respectively. Melittin showed high synergy (FBPCi, FBICi and FBECi < 0.5). The synergism resulted in a 64-512-fold, 2-16 and 2-8-fold reduction in melittin, rifampicin and vancomycin concentrations, respectively. The synergistic melittin concentration found to be effective did not manifest either cytotoxicity on HEK-293 or hemolytic activity on RBCs. Results showed that melittin downregulated the expression of biofilm-associated icaA, aap, and psm genes in all isolates tested, ranging from 0.04-folds to 2.11-folds for icaA and from 0.05 to 3.76-folds for aap and psm. The preventive and therapeutic indexes of melittin were improved 8-fold when combined with vancomycin and rifampin. Based on these findings, the combination of melittin with conventional antibiotics could be proposed for treating or preventing biofilm-associated MRSE infections.

Interactions between human milk oligosaccharides, microbiota and immune factors in milk of women with and without mastitis

Lactational mastitis is an excellent target to study possible interactions between HMOs, immune factors and milk microbiota due to the infectious and inflammatory nature of this condition. In this work, microbiological, immunological and HMO profiles of milk samples from women with (MW) or without (HW) mastitis were compared. Secretor status in women (based on HMO profile) was not associated to mastitis. DFLNH, LNFP II and LSTb concentrations in milk were higher in samples from HW than from MW among Secretor women. Milk from HW was characterized by a low bacterial load (dominated by Staphylococcus epidermidis and streptococci), high prevalence of IL10 and IL13, and low sialylated HMO concentration. In contrast, high levels of staphylococci, streptococci, IFNγ and IL12 characterized milk from MW. A comparison between subacute (SAM) and acute (AM) mastitis cases revealed differences related to the etiological agent (S. epidermidis in SAM; Staphylococcus aureus in AM), milk immunological profile (high content of IL10 and IL13 in SAM and IL2 in AM) and milk HMOs profile (high content of 3FL in SAM and of LNT, LNnT, and LSTc in AM). These results suggest that microbiological, immunological and HMOs profiles of milk are related to mammary health of women.

Look Who's Talking: Host and Pathogen Drivers of Staphylococcus epidermidis Virulence in Neonatal Sepsis

Preterm infants are at increased risk for invasive neonatal bacterial infections. S. epidermidis, a ubiquitous skin commensal, is a major cause of late-onset neonatal sepsis, particularly in high-resource settings. The vulnerability of preterm infants to serious bacterial infections is commonly attributed to their distinct and developing immune system. While developmentally immature immune defences play a large role in facilitating bacterial invasion, this fails to explain why only a subset of infants develop infections with low-virulence organisms when exposed to similar risk factors in the neonatal ICU. Experimental research has explored potential virulence mechanisms contributing to the pathogenic shift of commensal S. epidermidis strains. Furthermore, comparative genomics studies have yielded insights into the emergence and spread of nosocomial S. epidermidis strains, and their genetic and functional characteristics implicated in invasive disease in neonates. These studies have highlighted the multifactorial nature of S. epidermidis traits relating to pathogenicity and commensalism. In this review, we discuss the known host and pathogen drivers of S. epidermidis virulence in neonatal sepsis and provide future perspectives to close the gap in our understanding of S. epidermidis as a cause of neonatal morbidity and mortality.

MicroRNA hsa-let-7a facilitates staphylococcal small colony variants survival in the THP-1 macrophages by reshaping inflammatory responses

Recent studies have provided emerging evidence of the critical involvement of microRNAs in host immune defence against bacterial infection and that likewise the expression of the miRNAs is profoundly impacted by a variety of pathogens to subvert the immune response. Here, we report the role of hsa-let-7a miRNA in response to Staphylococcus epidermidis Small Colony Variants infection. We also assessed whether the expression levels of inflammatory cytokines associated with the hsa-let-7a are manipulated by the pathogen and the effect of the IFN-γ priming on the expression of hsa-let-7a and the fate of SCVs/WTs in infected macrophages. A striking observation was the downregulation of the let-7a miRNA upon challenge of the THP-1 activated cells with the SCV isolates while no significant changes in expression were noticed after the infection of macrophages with their WT counterparts. Staphylococcus epidermidis WT and SCV strains were found to invade and survive in macrophages. A significant reduction in bacterial load for both phenotypes was observed in macrophages treated with let-7a mimic compared to untreated ones. Survival of WTs was augmented in cells treated with the inhibitor in 4 out of 5 strains as compared to the number of bacteria recovered from non-transfected cells. At the same time, let-7a inhibitor did not influence on the survival of SCVs in macrophages as their number was comparable to number recovered from non-transfected cells. When the ratio of both let-7a cytokine targets was compared, anti-inflammatory IL-10 cytokine was induced by SCVs predominantly, while the macrophage challenge with WTs was characterized by the inflammatory cytokine profile with high IL-6 and low IL-10 production. Moreover, the balance between pro-inflammatory and anti-inflammatory cytokines has been expectedly retrieved when macrophages were transfected with let-7a mimic before infection with WT or SCV strains. The results also show that IFN-γ likely regulates the macrophage environment contributing to the inflammatory response and elimination of bacteria from intracellular milieu by augmenting the synthesis of pro-inflammatory cytokines and supressing the anti-inflammatory IL-10. Our work has shown that SCVs have the potential to regulate the let-7a miRNA to balance the pro-inflammatory IL-6 with anti-inflammatory IL-10 and this mechanism is one of the ways in a complex regulatory network adopted by SCVs to promote their survival.

Citral alleviates peptidoglycan-induced inflammation and disruption of barrier functions in porcine intestinal epithelial cells

Peptidoglycan (PGN) is a major polymer in bacterial cell walls and may constrain gut functionality and lower intestinal efficiencies in livestock. Citral has been reported to exhibit antibacterial and anti-inflammatory biological activities, improving the gastrointestinal function of swine. However, the protective effect of citral against PGN-elicited cellular responses and possible underlying mechanisms are unknown. In this study, the porcine jejunal epithelial cell line (IPEC-J2) was challenged with PGN from Staphylococcus aureus (S. aureus) or Bacillus subtilis (B. subtilis) to explore PGN-induced inflammatory responses. Our data showed that the inflammatory response stimulated by PGN from harmful bacteria (S. aureus) was more potent than that from commensal bacteria (B. subtilis) in IPEC-J2 cells. Based on the inflammatory model by PGN from S. aureus, it was demonstrated that PGN could significantly induce inflammatory cytokine production and influence nutrient absorption and barrier function in a dose-dependent manner. However, the PGN-mediated immune responses were remarkably suppressed by citral. In addition, citral significantly attenuated the effect of PGN on the intestine nutrient absorption and barrier function. The expression of TLR2 was strongly induced by PGN stimulation, which was suppressed by citral. All data nominated that citral downregulated PGN-induced inflammation via TLR2-mediated activation of the NF-κB signaling pathway in IPEC-J2 cells. Furthermore, the results also indicate that the PGN degradation through the inclusion of enzymes (e.g., muramidase) as well as the inclusion of citral for attenuating inflammation may improve pig gut health and functionality.

Presence of Candida tropicalis on Staphylococcus epidermidis Biofilms Facilitated Biofilm Production and Candida Dissemination: An Impact of Fungi on Bacterial Biofilms

While Staphylococcus epidermidis (SE) is a common cause of infections in implanted prostheses and other indwelling devices, partly due to the biofilm formation, Candida tropicalis (CT) is an emerging Candida spp. with a potent biofilm-producing property. Due to the possible coexistence between SE and CT infection in the same patient, characteristics of the polymicrobial biofilms from both organisms might be different from those of the biofilms of each organism. Then, the exploration on biofilms, from SE with or without CT, and an evaluation on l-cysteine (an antibiofilm against both bacteria and fungi) were performed. As such, Candida incubation in preformed SE biofilms (SE > CT) produced higher biofilms than the single- (SE or CT) or mixed-organism (SE + CT) biofilms as determined by crystal violet staining and fluorescent confocal images with z-stack thickness analysis. In parallel, SE > CT biofilms demonstrated higher expression of icaB and icaC than other groups at 20 and 24 h of incubation, suggesting an enhanced matrix polymerization and transportation, respectively. Although organism burdens (culture method) from single-microbial biofilms (SE or CT) were higher than multi-organism biofilms (SE + CT and SE > CT), macrophage cytokine responses (TNF-α and IL-6) against SE > CT biofilms were higher than those in other groups in parallel to the profound biofilms in SE > CT. Additionally, sepsis severity in mice with subcutaneously implanted SE > CT catheters was more severe than in other groups as indicated by mortality rate, fungemia, serum cytokines (TNF-α and IL-6), and kidney and liver injury. Although CT grows upon preformed SE-biofilm production, the biofilm structures interfered during CT morphogenesis leading to the frailty of biofilm structure and resulting in the prominent candidemia. However, l-cysteine incubation together with the organisms in catheters reduced biofilms, microbial burdens, macrophage responses, and sepsis severity. In conclusion, SE > CT biofilms prominently induced biofilm matrix, fungemia, macrophage responses, and sepsis severity, whereas the microbial burdens were lower than in the single-organism biofilms. All biofilms were attenuated by l-cysteine.

Unraveling the Microbiome of Necrotizing Enterocolitis: Insights in Novel Microbial and Metabolomic Biomarkers

Necrotizing enterocolitis (NEC) is among the most relevant gastrointestinal diseases affecting mostly prematurely born infants with low birth weight. While intestinal dysbiosis has been proposed as one of the possible factors involved in NEC pathogenesis, the role of the gut microbiota remains poorly understood. In this study, the gut microbiota of preterm infants was explored to highlight differences in the composition between infants affected by NEC and infants prior to NEC development. A large-scale gut microbiome analysis was performed, including 47 shotgun sequencing data sets generated in the framework of this study, along with 124 retrieved from publicly available repositories. Meta-analysis led to the identification of preterm community state types (PT-CSTs), which recur in healthy controls and NEC infants. Such analyses revealed an overgrowth of a range of opportunistic microbial species accompanying the loss of gut microbial biodiversity in NEC subjects. Moreover, longitudinal insights into preterm infants prior to NEC development indicated Clostridium neonatale and Clostridium perfringens species as potential biomarkers for predictive early diagnosis of this disease. Furthermore, functional investigation of the enzymatic reaction profiles associated with pre-NEC condition suggested DL-lactate as a putative metabolic biomarker for early detection of NEC onset.

IMPORTANCE Necrotizing enterocolitis (NEC) is a severe gastrointestinal disease occurring predominantly in premature infants whose etiology is still not fully understood. In this study, the analysis of infant fecal samples through shotgun metagenomics approaches revealed a marked reduction of the intestinal (bio)diversity and an overgrowth of (opportunistic) pathogens associated with the NEC development. In particular, dissection of the infant’s gut microbiome before NEC diagnosis highlighted the potential involvement of Clostridium genus members in the progression of NEC. Remarkably, our analyses highlighted a gastrointestinal DL-lactate accumulation among NEC patients that might represent a novel potential functional biomarker for the early diagnosis of NEC.

IL-6 Signaling Protects Zebrafish Larvae during Staphylococcus epidermidis Infection in a Bath Immersion Model

The host immune responses to Staphylococcus epidermidis, a frequent cause of nosocomial infections, are not well understood. We have established a bath immersion model of this infection in zebrafish (Danio rerio) larvae. Macrophages play a primary role in the host immune response and are involved in clearance of infection in the larvae. S. epidermidis infection results in upregulation of tlr-2 There is marked inflammation characterized by heightened NF-κB signaling and elevation of several proinflammatory cytokines. There is rapid upregulation of il-1b and tnf-a transcripts, whereas an increase in il-6 levels is relatively more delayed. The IL-6 signaling pathway is further amplified by elevation of IL-6 signal transducer (il-6st) levels, which negatively correlates with miRNA dre-miR-142a-5p. Enhanced IL-6 signaling is protective to the host in this model as inhibition of the signaling pathway resulted in increased mortality upon S. epidermidis infection. Our study describes the host immune responses to S. epidermidis infection, establishes the importance of IL-6 signaling, and identifies a potential role of miR-142-5p-il-6st interaction in this infection model.

Mechanisms of microbe-immune system dialogue within the skin

The prevalence and severity of dermatological conditions such as atopic dermatitis have increased dramatically during recent decades. Many of the factors associated with an altered risk of developing inflammatory skin disorders have also been shown to alter the composition and diversity of non-pathogenic microbial communities that inhabit the human host. While the most densely microbial populated organ is the gut, culture and non-culture-based technologies have revealed a dynamic community of bacteria, fungi, viruses and mites that exist on healthy human skin, which change during disease. In this review, we highlight some of the recent findings on the mechanisms through which microbes interact with each other on the skin and the signalling systems that mediate communication between the immune system and skin-associated microbes. In addition, we summarize the ongoing clinical studies that are targeting the microbiome in patients with skin disorders. While significant efforts are still required to decipher the mechanisms underpinning host-microbe communication relevant to skin health, it is likely that disease-related microbial communities, or Dermatypes, will help identify personalized treatments and appropriate microbial reconstitution strategies.

Whole Genome Sequencing of Methicillin-Resistant Staphylococcus epidermidis Clinical Isolates Reveals Variable Composite SCCmec ACME among Different STs in a Tertiary Care Hospital in Oman

Staphylococcus epidermidis has been recently recognized as an emerging nosocomial pathogen. There are concerns over the increasing virulence potential of this commensal due to the capabilities of transferring mobile genetic elements to Staphylococcus aureus through staphylococcal chromosomal cassette (SCCmec) and the closely related arginine catabolic mobile element (ACME) and the copper and mercury resistance island (COMER). The potential pathogenicity of S. epidermidis, particularly from blood stream infections, has been poorly investigated. In this study, 24 S. epidermidis isolated from blood stream infections from Oman were investigated using whole genome sequence analysis. Core genome phylogenetic trees revealed one third of the isolates belong to the multidrug resistance ST-2. Genomic analysis unraveled a common occurrence of SCCmec type IV and ACME element predominantly type I arranged in a composite island. The genetic composition of ACME was highly variable among isolates of same or different STs. The COMER-like island was absent in all of our isolates. Reduced copper susceptibility was observed among isolates of ST-2 and ACME type I, followed by ACME type V. In conclusion, in this work, we identify a prevalent occurrence of highly variable ACME elements in different hospital STs of S. epidermidis in Oman, thus strongly suggesting the hypothesis that ACME types evolved from closely related STs.

Patient-specific effects of soluble factors from Staphylococcus aureus and Staphylococcus epidermidis biofilms on osteogenic differentiation of primary human osteoblasts

Due to the frequency of biofilm-forming Staphylococcus aureus and Staphylococcus epidermidis in orthopedics, it is crucial to understand the interaction between the soluble factors produced by prokaryotes and their effects on eukaryotes. Our knowledge concerning the effect of soluble biofilm factors (SBF) and their virulence potential on osteogenic differentiation is limited to few studies, particularly when there is no direct contact between prokaryotic and eukaryotic cells. SBF were produced by incubating biofilm from S. aureus and S. epidermidis in osteogenic media. Osteoblasts of seven donors were included in this study. Our results demonstrate that the detrimental effects of these pathogens do not require direct contact between prokaryotic and eukaryotic cells. SBF produced by S. aureus and S. epidermidis affect the metabolic activity of osteoblasts. However, the effect of SBF derived from S. aureus seems to be more pronounced compared to that of S. epidermidis. The influence of SBF of S. aureus and S. epidermidis on gene expression of COL1A1, ALPL, BGLAP, SPP1, RUNX2 is bacteria-, patient-, concentration-, and incubation time dependent. Mineralization was monitored by staining the calcium and phosphate deposition and revealed that the SBF of S. epidermidis markedly inhibits calcium deposition; however, S. aureus shows a less inhibitory effect. Therefore, these new findings support the hypotheses that soluble biofilm factors affect the osteogenic processes substantially, particularly when there is no direct interaction between bacteria and osteoblast.

Ecology and Genetic Lineages of Nasal Staphylococcus aureus and MRSA Carriage in Healthy Persons with or without Animal-Related Occupational Risks of Colonization: A Review of Global Reports

In this conceptual review, we thoroughly searched for appropriate English articles on nasal staphylococci carriage among healthy people with no reported risk of colonization (Group A), food handlers (Group B), veterinarians (Group C), and livestock farmers (Group D) published between 2000 and 2021. Random-effects analyses of proportions were performed to determine the pooled prevalence of S. aureus, MRSA, MRSA-CC398, and MSSA-CC398, as well as the prevalence of PVL-positive S. aureus from all eligible studies. A total of 166 eligible papers were evaluated for Groups A/B/C/D (n = 58/31/26/51). The pooled prevalence of S. aureus and MRSA in healthy humans of Groups A to D were 15.9, 7.8, 34.9, and 27.1%, and 0.8, 0.9, 8.6, and 13.5%, respectively. The pooled prevalence of MRSA-CC398 nasal carriage among healthy humans was as follows: Group A/B (<0.05%), Group C (1.4%), Group D (5.4%); and the following among Group D: pig farmers (8.4%) and dairy farmers (4.7%). The pooled prevalence of CC398 lineage among the MSSA and MRSA isolates from studies of the four groups were Group A (2.9 and 6.9%), B (1.5 and 0.0%), C (47.6% in MRSA), and D (11.5 and 58.8%). Moreover, MSSA-CC398 isolates of Groups A and B were mostly of spa-t571 (animal-independent clade), while those of Groups C and D were spa-t011 and t034. The MRSA-CC398 was predominately of t011 and t034 in all the groups (with few other spa-types, livestock-associated clades). The pooled prevalence of MSSA and MRSA isolates carrying the PVL encoding genes were 11.5 and 9.6% (ranges: 0.0-76.9 and 0.0-28.6%), respectively. Moreover, one PVL-positive MSSA-t011-CC398 isolate was detected in Group A. Contact with livestock and veterinary practice seems to increase the risk of carrying MRSA-CC398, but not in food handlers. Thus, this emphasizes the need for integrated molecular epidemiology of zoonotic staphylococci.

Proper Skin Management in Breast Augmentation with a Periareolar Incision Prevents Implant Contamination and Biofilm-Related Capsular Contracture

BACKGROUND

Capsular contracture (CC) is a significant complication and major reason for revision in breast augmentation. Many studies indicate that most bacteria found in contracted capsules originate from the skin, especially that of the nipple-areolar complex (NAC). To prevent implant contamination, protocols without a periareolar incision have been proposed and have become a limitation for breast augmentation. We sought to propose a strategy of proper skin management for periareolar incisions to prevent implant contamination and biofilm-related CC.

METHODS

The analyses in this study are based on data collected from February 2017 to July 2020. A total of 129 patients were included, and they were randomized into two groups. The control group was subjected to no skin treatment before the surgery, and the treatment group underwent preoperative cleaning and disinfection of the NAC. We collected bacteriologic swabs used to rub the skin of the NAC and chest after draping and suturing from the control and treatment groups. We assessed the potential risk of detecting bacteria or fungi in the swabs, and we analyzed the data. The relationship between the positive culture rate and complication rate indicated the effectiveness of our strategy.

RESULTS

Initially, 774 swabs were obtained. In the control group, 6 swabs tested positive for pathogens, including 2 NAC swabs positive for Staphylococcus epidermidis (S. epidermidis) after draping and 3 and 1 NAC swabs positive for S. epidermidis and Staphylococcus aureus (S. aureus) after suturing, respectively. All the other samples in the control and treatment groups were negative for bacteria or fungi. All patients had at least 16 months of follow-up. No CC (Baker grades II-IV) was recorded during the follow-up, and the treatment group experienced a better outcome associated with a lower rate of minor complications.

CONCLUSIONS

Proper preoperative skin management helps keep the field pristine and potentially prevents implant contamination and even biofilm-related CC. With this strategy, breast augmentation using a periareolar incision or any other approach, even other surgery, could be a safe procedure.

LEVEL OF EVIDENCE IV

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The road to success of coagulase-negative staphylococci: clinical significance of small colony variants and their pathogenic role in persistent infections

Bacterial small colony variants represent an important aspect of bacterial variability. They are naturally occurring microbial subpopulations with distinctive phenotypic and pathogenic traits, reported for many clinically important bacteria. In clinical terms, SCVs tend to be associated with persistence in host cells and tissues and are less susceptible to antibiotics than their wild-type (WT) counterparts. The increased tendency of SCVs to reside intracellularly where they are protected against the host immune responses and antimicrobial drugs is one of the crucial aspects linking SCVs to recurrent or chronic infections, which are difficult to treat. An important aspect of the SCV ability to persist in the host is the quiescent metabolic state, reduced immune response and expression a changed pattern of virulence factors, including a reduced expression of exotoxins and an increased expression of adhesins facilitating host cell uptake. The purpose of this review is to describe in greater detail the currently available data regarding CoNS SCV and, in particular, their clinical significance and possible mechanisms by which SCVs contribute to the pathogenesis of the chronic infections. It should be emphasized that in spite of an increasing clinical significance of this group of staphylococci, the number of studies unraveling the mechanisms of CoNS SCVs formation and their impact on the course of the infectious process is still scarce, lagging behind the studies on S. aureus SCVs.

Staphylococcal trafficking and infection - from 'nose to gut' and back

Staphylococcus aureus is an opportunistic human pathogen, which is a leading cause of infections worldwide. The challenge in treating S. aureus infection is linked to the development of multidrug-resistant strains and the mechanisms employed by this pathogen to evade the human immune defenses. In addition, S. aureus can hide asymptomatically in particular ‘protective’ niches of the human body for prolonged periods of time. In the present review, we highlight recently gained insights in the role of the human gut as an endogenous S. aureus reservoir next to the nasopharynx and oral cavity. In addition, we address the contribution of these ecological niches to staphylococcal transmission, including the roles of particular triggers as modulators of the bacterial dissemination. In this context, we present recent advances concerning the interactions between S. aureus and immune cells to understand their possible roles as vehicles of dissemination from the gut to other body sites. Lastly, we discuss the factors that contribute to the switch from colonization to infection. Altogether, we conclude that an important key to uncovering the pathogenesis of S. aureus infection lies hidden in the endogenous staphylococcal reservoirs, the trafficking of this bacterium through the human body and the subsequent immune responses.

Characterization of Weissella viridescens UCO-SMC3 as a Potential Probiotic for the Skin: Its Beneficial Role in the Pathogenesis of Acne Vulgaris

Previously, we isolated lactic acid bacteria from the slime of the garden snail Helix aspersa Müller and selected Weissella viridescens UCO-SMC3 because of its ability to inhibit in vitro the growth of the skin-associated pathogen Cutibacterium acnes. The present study aimed to characterize the antimicrobial and immunomodulatory properties of W. viridescens UCO-SMC3 and to demonstrate its beneficial effect in the treatment of acne vulgaris. Our in vitro studies showed that the UCO-SMC3 strain resists adverse gastrointestinal conditions, inhibits the growth of clinical isolates of C. acnes, and reduces the adhesion of the pathogen to keratinocytes. Furthermore, in vivo studies in a mice model of C. acnes infection demonstrated that W. viridescens UCO-SMC3 beneficially modulates the immune response against the skin pathogen. Both the oral and topical administration of the UCO-SCM3 strain was capable of reducing the replication of C. acnes in skin lesions and beneficially modulating the inflammatory response. Of note, orally administered W. viridescens UCO-SMC3 induced more remarkable changes in the immune response to C. acnes than the topical treatment. However, the topical administration of W. viridescens UCO-SMC3 was more efficient than the oral treatment to reduce pathogen bacterial loads in the skin, and effects probably related to its ability to inhibit and antagonize the adhesion of C. acnes. Furthermore, a pilot study in acne volunteers demonstrated the capacity of a facial cream containing the UCO-SMC3 strain to reduce acne lesions. The results presented here encourage further mechanistic and clinical investigations to characterize W. viridescens UCO-SMC3 as a probiotic for acne vulgaris treatment.

Fracture biomechanics influence local and systemic immune responses in a murine fracture-related infection model

Biomechanical stability plays an important role in fracture healing, with unstable fixation being associated with healing disturbances. A lack of stability is also considered a risk factor for fracture-related infection (FRI), although confirmatory studies and an understanding of the underlying mechanisms are lacking. In the present study, we investigate whether biomechanical (in)stability can lead to altered immune responses in mice under sterile or experimentally inoculated conditions. In non-inoculated C57BL/6 mice, instability resulted in an early increase of inflammatory markers such as granulocyte-colony stimulating factor (G-CSF), keratinocyte chemoattractant (KC) and interleukin (IL)-6 within the bone. When inoculated with Staphylococcus epidermidis, instability resulted in a further significant increase in G-CSF, IL-6 and KC in bone tissue. Staphylococcus aureus infection led to rapid osteolysis and instability in all animals and was not further studied. Gene expression measurements also showed significant upregulation in CCL2 and G-CSF in these mice. IL-17A was found to be upregulated in all S. epidermidis infected mice, with higher systemic IL-17A cell responses in mice that cleared the infection, which was found to be produced by CD4+ and γδ+ T cells in the bone marrow. IL-17A knock-out (KO) mice displayed a trend of delayed clearance of infection (P=0.22, Fisher’s exact test) and an increase in interferon (IFN)-γ production. Biomechanical instability leads to a more pronounced local inflammatory response, which is exaggerated by bacterial infection. This study provides insights into long-held beliefs that biomechanics are crucial not only for fracture healing, but also for control of infection.

Summary: Physical movement between bone fragments after a fracture influence healing, and are shown here, for the first time, to influence immune responses and infection.

Determination of the frequency, species distribution and antimicrobial resistance of staphylococci isolated from dogs and their owners in Trinidad

The close contact between humans and their dogs can lead to the commingling of staphylococci and the exchange of mobile genetic elements encoding antimicrobial resistance. The objectives of this study were to determine the species distribution and antimicrobial resistance patterns of staphylococci colonizing canine pets and their owners in Trinidad. Staphylococci were isolated from canine pets and their owners and identified using MALDI-TOF mass spectrometry. Antimicrobial susceptibilities were determined using the Kirby-Bauer disc diffusion method against seven classes of antimicrobial agents. A total of 440 staphylococci were isolated from 112 canine pets and their owners, 53.4% were from canine pets and 46.6% were from owners. Twenty-four species were detected, of which, most isolates (32.5%) belonged to the Staphylococcus intermedius group (SIG). S. sciuri was the most common species of coagulase-negative staphylococci (CoNS) comprising 22.3% of all isolates. Antimicrobial resistance was highest against commonly used antimicrobials, such as penicillin (51.4%), tetracycline (26.1%) and trimethoprim/sulfamethoxazole (18.6%). These antimicrobials also comprised the most common multidrug resistance (MDR) combination. Overall, 19.1% of isolates displayed multidrug resistance. No methicillin-resistant Staphylococcus aureus (MRSA) isolates were detected. However, methicillin resistance was detected in 13.3% and 15.1% of coagulase-positive staphylococci (CoPS) and the CoNS+CoVS (combined CoNS and coagulase-variable staphylococci) group respectively. The presence of methicillin-resistant staphylococci is worrisome because there is the potential for the transfer of these strains between dogs and humans. These strains may act as a reservoir of resistance genes.

Bactericidal fully human single-chain fragment variable antibodies protect mice against methicillin-resistant Staphylococcus aureus bacteraemia

OBJECTIVES

The increasing prevalence of antibiotic-resistant Staphylococcus aureus, besides the inadequate numbers of effective antibiotics, emphasises the need to find new therapeutic agents against this lethal pathogen.

METHODS

In this study, to obtain antibody fragments against S. aureus, a human single-chain fragment variable (scFv) library was enriched against living methicillin-resistant S. aureus (MRSA) cells, grown in three different conditions, that is human peripheral blood mononuclear cells with plasma, whole blood and biofilm. The antibacterial activity of scFvs was evaluated by the growth inhibition assay in vitro. Furthermore, the therapeutic efficacy of anti-S. aureus scFvs was appraised in a mouse model of bacteraemia.

RESULTS

Three scFv antibodies, that is MEH63, MEH158 and MEH183, with unique sequences, were found, which exhibited significant binding to S. aureus and reduced the viability of S. aureus in in vitro inhibition assays. Based on the results, MEH63, MEH158 and MEH183, in addition to their combination, could prolong the survival rate, reduce the bacterial burden in the blood and prevent inflammation and tissue destruction in the kidneys and spleen of mice with MRSA bacteraemia compared with the vehicle group (treated with normal saline).

CONCLUSION

The combination therapy with anti-S. aureus scFvs and conventional antibiotics might shed light on the treatment of patients with S. aureus infections.

Non-Native Peptides Capable of Pan-Activating the agr Quorum Sensing System across Multiple Specificity Groups of Staphylococcus epidermidis

Staphylococcus epidermidis is a leading cause of hospital-acquired infections. Traditional antibiotics have significantly reduced efficacy against this pathogen due to its ability to form biofilms on abiotic surfaces and drug resistance. The accessory gene regulator (agr) quorum sensing system is directly involved in S. epidermidis pathogenesis. Activation of agr is achieved via binding of the autoinducing peptide (AIP) signal to the extracellular sensor domain of its cognate receptor, AgrC. Divergent evolution has given rise to four agr specificity groups in S. epidermidis defined by the unique AIP sequence used by each group (AIPs-I-IV) with observed cross-group activities. As agr agonism has been shown to reduce biofilm growth in S. epidermidis, the development of pan-group activators of the agr system is of interest as a potential antivirulence strategy. To date, no synthetic compounds have been identified that are capable of appreciably activating the agr system of more than one specificity group of S. epidermidis or, to our knowledge, of any of the other Staphylococci. Here, we report the characterization of the structure-activity relationships for agr agonism by S. epidermidis AIP-II and AIP-III and the application of these new SAR data and those previously reported for AIP-I for the design and synthesis of the first multigroup agr agonists. These non-native peptides were capable of inducing the expression of critical biofilm dispersal agents (i.e., phenol-soluble modulins) in cell culture and represent new tools to study the role of quorum sensing in S. epidermidis infections.

Novel electrospun poly-hydroxybutyrate scaffolds as carriers for the wound healing agents alkannins and shikonins

The aim of this study was to investigate the potential of novel electrospun fiber mats loaded with alkannin and shikonin (A/S) derivatives, using as carrier a highly biocompatible, bio-derived, eco-friendly polymer such as poly[(R)-3-hydroxybutyric acid] (PHB). PHB fibers containing a mixture of A/S derivatives at different ratios were successfully fabricated via electrospinning. Αs evidenced by scanning electron microscopy, the fibers formed a bead-free mesh with average diameters from 1.25 to 1.47 μm. Spectroscopic measurements suggest that electrospinning marginally increases the amorphous content of the predominantly crystalline PHB in the fibers, while a significant drug amount lies near the fiber surface for samples of high total A/S content. All scaffolds displayed satisfactory characteristics, with the lower concentrations of A/S mixture-loaded PHB fiber mats achieving higher porosity, water uptake ratios, and entrapment efficiencies. The in vitro dissolution studies revealed that all samples released more than 70% of the encapsulated drug after 72 h. All PHB scaffolds tested by cell viability assay were proven non-toxic for Hs27 fibroblasts, with the 0.15 wt.% sample favoring cell attachment, spreading onto the scaffold surface, as well as cell proliferation. Finally, the antimicrobial activity of PHB meshes loaded with A/S mixture was documented for Staphylococcus epidermidis and S. aureus.

Antiplanktonic and antibiofilm effects of two synthetic antimicrobial peptides against Staphylococcus epidermidis

OBJECTIVES

Staphylococcus epidermidis is one of the most common Gram-positive cocci in nosocomial infection, which could adhere to the surface of medical apparatus and causes biofilm-related infections. In the present study, we aim to explore the antimicrobial effects of GH12 and SAAP-148 against Staphylococcus epidermidis.

METHODS

Micro-dilution methods were used to detect the minimal inhibitory/bactericidal concentration of peptides on Staphylococcus epidermidis. Biofilm formation positive type strain was used to determine the antibiofilm effects of the peptides. Biofilms were built on the cover slides and fluorescent dye SYTO9 and laser confocal microscope were used to observe the effects of peptides on the three-dimensional structure of Staphylococcus epidermidis biofilms. The cell membrane permeability of Staphylococcus epidermidis was detected by flow cytometry. Expressions of icaA and icaDgenes were analyzed by real-time reverse transcription PCR.

RESULTS

The minimal inhibitory concentrations of GH12 and SAAP-148 against Staphylococcus epidermidis were 8 and 16 μg/mL, respectively, and the minimal bactericidal concentration was 64 μg/mL. GH12 and SAAP-148 significantly inhibited the biofilm formation of Staphylococcus epidermidis at the concentration of 8 μg/mL (t=7.193, P<0.05) and 16 μg/mL (t=7.808, P<0.05), respectively. Similarly, the GH12 and SAAP-148 significantly eradicated the pre-formed biofilms at the concentration of 16 μg/mL (t=5.369, P<0.05) and 32 μg/mL (t=4.474, P<0.05) in a dose-response manner, respectively. Meanwhile, the two peptides broke the structure of biofims and reduce the total biomass. GH12 and SAAP-148 at the concentration of minimal inhibitory concentration significantly disrupted the cell membrane of Staphylococcus epidermidis. The expressions of icaA and icaDgenes were significantly inhibited by antimicrobial peptides at the 1×minimal inhibitory concentration.

CONCLUSIONS

GH12 and SAAP-148 show significantly antimicrobial and anti-biofilm effects against Staphylococcus epidermidis by disruption of cell membrane and inhibition of icaAand icaDgene expression.

eDNA-Mediated Cutaneous Protection Against UVB Damage Conferred by Staphylococcal Epidermal Colonization

The human skin is a lush microbial habitat which is occupied by a wide array of microorganisms. Among the most common inhabitants are Staphylococcus spp., namely Staphylococcus epidermidis and, in ≈20% of healthy individuals, Staphylococcus aureus. Both bacteria have been associated with cutaneous maladies, where they mostly arrange in a biofilm, thus achieving improved surface adhesion and stability. Moreover, our skin is constantly exposed to numerous oxidative environmental stressors, such as UV-irradiation. Thus, skin cells are equipped with an important antioxidant defense mechanism, the Nrf2–Keap1 pathway. In this work, we aimed to explore the morphology of S. aureus and S. epidermidis as they adhered to healthy human skin and characterize their matrix composition. Furthermore, we hypothesized that the localization of both types of bacteria on a healthy skin surface may provide protective effects against oxidative stressors, such as UV-irradiation. Our results indicate for the first time that S. aureus and S. epidermidis assume a biofilm-like morphology as they adhere to ex vivo healthy human skin and that the cultures’ extracellular matrix (ECM) is composed of extracellular polysaccharides (EPS) and extracellular DNA (eDNA). Both bacterial cultures, as well as isolated S. aureus biofilm eDNA, conferred cutaneous protection against UVB-induced apoptosis. This work emphasized the importance of skin microbiota representatives in the maintenance of a healthy cutaneous redox balance by activating the skin’s natural defense mechanism.

Membrane perturbation, altered morphology and killing of Staphylococcus epidermidis upon contact with a cytocompatible peptide-based antibacterial surface

One possibility to prevent prosthetic infections is to produce biomaterials resistant to bacterial colonization by anchoring membrane active antimicrobial peptides (AMPs) onto the implant surface. In this perspective, a deeper understanding of the mode of action of the immobilized peptides should improve the development of AMP-inspired infection-resistant biomaterials. The aim of the present study was to characterize the bactericidal mechanism against Staphylococcus epidermidis of the AMP BMAP27(1-18), immobilized on titanium disks and on a model resin support, by applying viability counts, Field Emission Scanning Electron Microscopy (FE-SEM), and a fluorescence microplate assay with a membrane potential-sensitive dye. The cytocompatibility to osteoblast-like MG-63 cells was investigated in monoculture and in co-culture with bacteria. The impact of peptide orientation was explored by using N- and C- anchored analogues. On titanium, the ∼50 % drop in bacteria viability and dramatically affected morphology indicate a contact-killing action exerted by the N- and C-immobilized peptides to the same extent. As further shown by the fluorescence assay with the resin-anchored peptides, the bactericidal effect was mediated by rapid membrane perturbation, similar to free peptides. However, at peptide MBC resin equivalents the C-oriented analogue proved more effective with more than 99 % killing and maximum fluorescence increase, compared to half-maximum fluorescence with more than 90 % killing produced by the N-orientation. Confocal microscopy analyses revealed 4-5 times better MG-63 cell adhesion on peptide-functionalized titanium both in monoculture and in co-culture with bacteria, regardless of peptide orientation, thus stimulating further studies on the effects of the immobilized BMAP27(1-18) on osteoblast cells.

Evaluation of the role of staphylococci in the pathomechanism of conjunctivitis

Purpose

Determination of the association between ica genes and phenotypic biofilm formation in staphylococcal isolates involved in conjunctivitis, their antibiotic resistance as well as detection of selected virulence characteristics: adhesion to epithelial cells and in vitro cytotoxicity.

Methods

The study included 26 Staphylococcus aureus (SA) and 26 Staphylococcus epidermidis (SE) isolates. The presence of icaAD genes and ica operon was determined by the PCR assay. Phenotypic biofilm formation was verified using the microtitre plate assay. Antibiotic resistance was performed using the disc diffusion method. Staphylococcal ability to attach to host cells was assessed by flow cytometry. Cytotoxicity on epithelial cells was evaluated by LDH assay.

Results

The ica genes were detected in 26.9% of SE and in 42.3% of SA isolates. Only 15.3% of isolates (SE) were positive for both the icaAD and the ica operon. Phenotypically, 19.2% of SE isolates were strong biofilm producers, among which three were both icaAD- and ica operon-positive. About 26.9% of SA isolates were strong biofilm producers. Methicillin resistance (MR) was detected in 34.6% of SE and 26.9% of SA isolates. About 75% of MR isolates were multidrug resistant. SA isolates adhered to host cells more extensively than SE. SA isolates released higher level of LDH than SE.

Conclusions

Adherence abilities were commonly observed in staphylococci associated with conjunctivitis. However, low prevalence of isolates positive for a complete and functional ica locus and low prevalence of strong biofilm producers was detected. SA adhered to a greater extent to eukaryotic cells than SE and were more cytotoxic.

Improved diagnostic prediction of the pathogenicity of bloodstream isolates of Staphylococcus epidermidis

With an estimated 440,000 active cases occurring each year, medical device associated infections pose a significant burden on the US healthcare system, costing about $9.8 billion in 2013. Staphylococcus epidermidis is the most common cause of these device-associated infections, which typically involve isolates that are multi-drug resistant and possess multiple virulence factors. S. epidermidis is also frequently a benign contaminant of otherwise sterile blood cultures. Therefore, tests that distinguish pathogenic from non-pathogenic isolates would improve the accuracy of diagnosis and prevent overuse/misuse of antibiotics. Attempts to use multi-locus sequence typing (MLST) with machine learning for this purpose had poor accuracy (~73%). In this study we sought to improve the diagnostic accuracy of predicting pathogenicity by focusing on phenotypic markers (i.e., antibiotic resistance, growth fitness in human plasma, and biofilm forming capacity) and the presence of specific virulence genes (i.e., mecA, ses1, and sdrF). Commensal isolates from healthy individuals (n = 23), blood culture contaminants (n = 21), and pathogenic isolates considered true bacteremia (n = 54) were used. Multiple machine learning approaches were applied to characterize strains as pathogenic vs non-pathogenic. The combination of phenotypic markers and virulence genes improved the diagnostic accuracy to 82.4% (sensitivity: 84.9% and specificity: 80.9%). Oxacillin resistance was the most important variable followed by growth rate in plasma. This work shows promise for the addition of phenotypic testing in clinical diagnostic applications.

Staphylococcus aureus and S. epidermidis in biological systems of hospital environment: Antibiotic resistance patterns in regions of Ukraine

Staphylococcus bacteria are ubiquitous and often circulate in the biological systems of the hospital environment. Staphylococci have developed antibiotic resistance mechanisms resulting in a significant medical and economic burden to the healthcare system. The goal of our research was to conduct a comparative analysis of resistance to antibiotics in S. aureus and S. epidermidis isolates found in surgical hospitals in Kharkiv and Poltava regions. In 2013 through 2019, 151,015 and 98,754 tests were made by disc-diffusion method to identify the sensitivity in the S. aureus strains to antibiotics in Kharkiv and Poltava regions respectively. In 2013–2015, 15,589 tests were made in Kharkiv region to identify antibiotics sensitivity in S. epidermidis strains. Comparison of antibiotic resistance of the S. aureus strains in Kharkiv and Poltava regions was performed using the Pearson Chi-square test (χ2) and Fisher’s exact test. The proportion of S. aureus strains resistant to penicillins, cephalosporins, carbapenems, aminoglycosides, and macrolides was higher in Kharkiv region in terms of statistical validity than in Poltava region. Overall, the proportion of S. aureus strains resistant to lincozamids, tetracycline antibiotics, and fluoroquinolones in Poltava region was higher in terms of statistical validity than in Kharkiv region. An analysis of resistance of S. aureus strains to linezolid demonstrated that in Poltava region the proportion of resistant microorganisms was higher in terms of statistical validity in 2013–2014 and in 2016–2018. In Kharkiv region, in 2013 and in 2014, 96.3% and 89.1% of isolated strains of S. aureus respectively, were resistant to vancomycin. In 2019, more than a quarter of the located isolates (26.6%) in Poltava region were resistant to this antibiotic. The analysis of the dynamic of resistance in S. epidermidis isolates demonstrated that in 2015 nearly half of the isolates located in Kharkiv region were insensitive to penicillin antibiotics. Between 2013 and 2015, the spread of resistance to cephalosporins, aminoglycosides, macrolides, and fluoroquinolones among the S. epidermidis isolates noticeably increased. When S. epidermidis resistance to vancomycin was analyzed, a decrease in the proportion of resistant strains from 88.0% in 2013 to 8.7% in 2015 was noted. A promising direction for further research is the creation of passports of microorganism resistance in the regions and various health-care settings, as well as the creation of a unified national database network on microorganism resistance using modern methodologies for determining the phenotypes and genotypes of microorganisms.

Longitudinal time-lapse in vivo micro-CT reveals differential patterns of peri-implant bone changes after subclinical bacterial infection in a rat model

Subclinical infection associated with orthopedic devices can be challenging to diagnose. The goal of this study was to evaluate longitudinal, microcomputed tomography (microCT) imaging in a rat model of subclinical orthopedic device-related infection caused by Staphylococcus epidermidis and four different Cutibacterium (previously Propionibacterium) acnes strains, and compare outcomes with non-inoculated and historical S. aureus-inoculated controls. Sterile screws or screws colonized with bacteria were placed in the tibia of 38 adult Wistar rats [n = 6 sterile screws; n = 6 S. epidermidis-colonized screws; n = 26 C. acnes-colonized screws (covering all three main subspecies)]. Regular microCT scans were taken over 28 days and processed for quantitative time-lapse imaging with dynamic histomorphometry. At euthanasia, tissues were processed for semiquantitative histopathology or quantitative bacteriology. All rats receiving sterile screws were culture-negative at euthanasia and displayed progressive bony encapsulation of the screw. All rats inoculated with S. epidermidis-colonized screws were culture-positive and displayed minor changes in peri-implant bone, characteristic of subclinical infection. Five of the 17 rats in the C. acnes inoculated group were culture positive at euthanasia and displayed bone changes at the interface of the screw and bone, but not deeper in the peri-implant bone. Dynamic histomorphometry revealed significant differences in osseointegration, bone remodeling and periosteal reactions between groups that were not measurable by visual observation of still microCT images. Our study illustrates the added value of merging 3D microCT data from subsequent timepoints and producing inherently richer 4D data for the detection and characterization of subclinical orthopedic infections, whilst also reducing animal use.

Biodegradable Zn-Cu alloys show antibacterial activity against MRSA bone infection by inhibiting pathogen adhesion and biofilm formation

Bone and joint-related infections remain the primary and most critical complications of orthopedic surgery. We have innovatively prepared Zn-Cu alloys to achieve outstanding material and antibacterial properties. In this study, we systematically assessed the material properties and antibacterial activity of these Zn-Cu alloys. Our results showed that the Zn-2Cu alloy had the best mechanical properties, biocompatibility, and osteogenic properties. Findings of microbial cultures, CLSM, SEM, and TEM indicated that Zn-2Cu alloy can inhibit both coagulase-positive and coagulase-negative staphylococci, as well as antibiotic-resistant strains (MRSA and MRSE), by preventing the bacteria adhesion and the biofilm formation. Zn-2Cu alloy could broadly affect the expression of MRSA genes associated with adhesion, autolysis, biofilm formation, virulence, and drug resistance. A rat femur intramedullary nail infection-prevention model was established and the Zn-2Cu alloy-treated group showed significant antibacterial activity against MRSA and reduced the inflammatory toxic side-effects and infection-related bone loss. Collectively, our results indicate the potential utility of Zn-Cu alloy implants with 2 wt% Cu in treating orthopedic infections. Statement of significance: Osteomyelitis is a serious complication of orthopedic surgeries. Wide use of antibiotics contributes to the appearance of multi-drug resistant strains like methicillin-resistant staphylococcus aureus (MRSA). Alternatively, anti-osteomyelitis implants with broad-spectrum antibacterial properties can be favorable. Here, the antibacterial performance of biodegradable Zn-Cu alloys was evaluated with four different bacteria strains including antibiotic-resistant strains (MRSA and MRSE). Zn-Cu alloys exert excellent bacterial killing capability in all strains. In a rat femur infection model, the alloy showed significant antibacterial activity against MRSA and reduced inflammatory toxic side-effects as well as infection-related bone loss. The antibacterial property of Zn-2Cu alloy was associated with inhibition of gene expression related to wall synthesis, adhesion, colonization, biofilm formation, autolysis, and secretion of virulence factors in MRSA.

Susceptibility to biofilm formation on 3D-printed titanium fixation plates used in the mandible: a preliminary study

Background: In the oral and maxillofacial surgery, fixation plates are commonly used for the stabilization of bone fragments. Additive manufacturing has enabled us to design and create personalized fixation devices that would ideally fit any given fracture. Aim: The aim of the present preliminary study was to assess the susceptibility of 3D-printed titanium fixation plates to biofilm formation. Methods: Plates were manufactured using selective laser melting (SLM) from Ti-6Al-4 V. Reference strains of Streptococcus mutans, Staphyloccocus epidermidis, Staphylococcus aureus, Lactobacillus rhamnosus, and Candida albicans, were tested to evaluate the material's susceptibility to biofilm formation over 48 hours. Biofilm formations were quantified by a colorimetric method and colony-forming units (CFU) quantification. Scanning electron microscopy (SEM) visualized the structure of the biofilm. Results: Surface analysis revealed the average roughness of 102.75 nm and irregular topography of the tested plates. They were susceptible to biofilm formation by all tested strains. The average CFUs were as follows: S. mutans (11.91 x 107) > S.epidermidis (4.45 x 107) > S. aureus (2.3 x 107) > C.albicans (1.22 x 107) > L. rhamnosus (0.78 x 107). Conclusions: The present preliminary study showed that rough surfaces of additively manufactured titanium plates are susceptible to microbial adhesion. The research should be continued in order to compare additively manufactured plates with other commercially available osteotomy plates. Therefore, we suggest caution when using this type of material.

Temporal Changes in Patient-Matched Staphylococcus epidermidis Isolates from Infections: towards Defining a 'True' Persistent Infection

Staphylococcus epidermidis is found naturally on the skin but is a common cause of persistent orthopaedic device-related infections (ODRIs). This study used a pan-genome and gene-by-gene approach to analyse the clonality of whole genome sequences (WGS) of 115 S. epidermidis isolates from 55 patients with persistent ODRIs. Analysis of the 522 gene core genome revealed that the isolates clustered into three clades, and MLST analysis showed that 83% of the isolates belonged to clonal complex 2 (CC2). Analysis also found 13 isolate pairs had different MLST types and less than 70% similarity within the genes; hence, these were defined as re-infection by a different S. epidermidis strain. Comparison of allelic diversity in the remaining 102 isolates (49 patients) revealed that 6 patients had microevolved infections (>7 allele differences), and only 37 patients (77 isolates) had a ‘true’ persistent infection. Analysis of the core genomes of isolate pairs from 37 patients found 110/841 genes had variations; mainly in metabolism associated genes. The accessory genome consisted of 2936 genes; with an average size of 1515 genes. To conclude, this study demonstrates the advantage of using WGS for identifying the accuracy of a persistent infection diagnosis. Hence, persistent infections can be defined as ‘true’ persistent infections if the core genome of paired isolates has ≤7 allele differences; microevolved persistent infection if the paired isolates have >7 allele differences but same MLST type; and polyclonal if they are the same species but a different MLST type.

Antimicrobial Properties of MgO Nanostructures on Magnesium Substrates

Magnesium (Mg) and its alloys have attracted increasing attention in recent years as medical implants for repairing musculoskeletal injuries because of their promising mechanical and biological properties. However, rapid degradation of Mg and its alloys in physiological fluids limited their clinical translation because the accumulation of hydrogen (H2) gas and fast release of OH- ions could adversely affect the healing process. Moreover, infection is a major concern for internally implanted devices because it could lead to biofilm formation, prevent host cell attachment on the implants, and interfere osseointegration, resulting in implant failure or other complications. Fabricating nanostructured magnesium oxide (MgO) on magnesium (Mg) substrates is promising in addressing both problems because it could slow down the degradation process and improve the antimicrobial activity. In this study, nanostructured MgO layers were created on Mg substrates using two different surface treatment techniques, i.e., anodization and electrophoretic deposition (EPD), and cultured with Staphylococcus aureus in vitro to determine their antimicrobial properties. At the end of the 24-h bacterial culture, the nanostructured MgO layers on Mg prepared by anodization or EPD both showed significant bactericidal effect against S. aureus. Thus, nanostructured MgO layers on Mg are promising for reducing implant-related infections and complications and should be further explored for clinical translation toward antimicrobial biodegradable implants.

Cutibacterium acnes: a threat to shoulder surgery or an orthopedic red herring?

Cutibacterium acnes is a lipophilic, anaerobic, gram-positive bacillus that mainly colonizes the pilosebaceous glands of human skin. It has been implicated as the leading cause of prosthetic joint infection (PJI) after shoulder arthroplasty. However, PJI caused by C acnes rarely manifests as overt clinical, laboratory, or imaging features. In fact, more than 40% of shoulders undergoing revision arthroplasty are likely to be culture positive. However, rates of infection following a positive culture can be as low as 5%. The purpose of this review was to put forth alternative explanations for this discordance between positive cultures and infection. We describe C acnes roles as a commensal, bystander, and/or contaminant organism; the role of cultures in diagnosis and other methods that may be more accurate; its existence in a shoulder microbiome; and the variable virulence of C acnes. C acnes is an important cause of shoulder PJI in some patients. However, there is a large body of literature that suggests other functions that need to be considered. Further research is needed to define the role of C acnes that is logically explained by all of the literature and not only some.

The Genome of Staphylococcus epidermidis O47

The skin colonizing coagulase-negative Staphylococcus epidermidis causes nosocomial infections and is an important opportunistic and highly adaptable pathogen. To gain more insight into this species, we sequenced the genome of the biofilm positive, methicillin susceptible S. epidermidis O47 strain (hereafter O47). This strain belongs to the most frequently isolated sequence type 2. In comparison to the RP62A strain, O47 can be transformed, which makes it a preferred strain for molecular studies. S. epidermidis O47’s genome has a single chromosome of about 2.5 million base pairs and no plasmid. Its oriC sequence has the same directionality as S. epidermidis RP62A, S. carnosus, S. haemolyticus, S. saprophyticus and is inverted in comparison to Staphylococcus aureus and S. epidermidis ATCC 12228. A phylogenetic analysis based on all S. epidermidis genomes currently available at GenBank revealed that O47 is closest related to DAR1907. The genome of O47 contains genes for the typical global regulatory systems known in staphylococci. In addition, it contains most of the genes encoding for the typical virulence factors for S. epidermidis but not for S. aureus with the exception of a putative hemolysin III. O47 has the typical S. epidermidis genetic islands and several mobile genetic elements, which include staphylococcal cassette chromosome (SCC) of about 54 kb length and two prophages φO47A and φO47B. However, its genome has no transposons and the smallest number of insertion sequence (IS) elements compared to the other known S. epidermidis genomes. By sequencing and analyzing the genome of O47, we provide the basis for its utilization in genetic and molecular studies of biofilm formation.

Food-derived coagulase-negative Staphylococcus as starter cultures for fermented foods

Food safety is of significant concern to consumers and is a major issue for the food industry. As such, the industry is aware of the importance of safety assessments of starters used in the production of fermented foods. Coagulase-negative staphylococci (CNS) are the predominant bacteria found in fermented foods worldwide. Because of this, food-derived CNS are used as starters for cheese and meat fermentation, and have been investigated for use as starters in soybean fermentation. Although food-derived CNS are generally considered non-pathogenic, their safety remains uncertain following the isolation of CNS from skin infections in humans and animals, and because they belong to the same genus as the highly pathogenic species Staphylococcus aureus. This review explores what is known about the safety of food-derived CNS, focusing on antibiotic resistance, enterotoxin genes, and biogenic amine production, to aid in the selection of starter candidates.

Promising Therapeutic Strategies Against Microbial Biofilm Challenges

Biofilms are communities of microorganisms that are attached to a biological or abiotic surface and are surrounded by a self-produced extracellular matrix. Cells within a biofilm have intrinsic characteristics that are different from those of planktonic cells. Biofilm resistance to antimicrobial agents has drawn increasing attention. It is well-known that medical device- and tissue-associated biofilms may be the leading cause for the failure of antibiotic treatments and can cause many chronic infections. The eradication of biofilms is very challenging. Many researchers are working to address biofilm-related infections, and some novel strategies have been developed and identified as being effective and promising. Nevertheless, more preclinical studies and well-designed multicenter clinical trials are critically needed to evaluate the prospects of these strategies. Here, we review information about the mechanisms underlying the drug resistance of biofilms and discuss recent progress in alternative therapies and promising strategies against microbial biofilms. We also summarize the strengths and weaknesses of these strategies in detail.

Bacteriological Study of Electronic Devices Used by Healthcare Workers at Ruhengeri Referral Hospital

Electronic devices have become one of the most essential accessories being used in hospitals. Those devices increase the communication and contact making healthcare delivery more efficient and quality service oriented. The study was designed to collect reliable information about the spreading of pathogens through electronic devices especially in sensitive departments. The objectives of this study were to evaluate the bacterial colonization of electronic devices and determine the effectiveness of disinfection with alcohol 70% (w/v) to reduce the bacterial colonization of electronic devices. It was a cross-sectional study where samples were collected by means of moistened swabs in sterile saline solution from 30 electronic devices used by healthcare workers at Ruhengeri Referral Hospital within four different units: maternity, neonathology, intensive care, and theater room. To evaluate the effects of disinfection using 70% isopropyl alcohol, the second sample collection was carried out after decontamination with 70% isopropyl alcohol. Samples were analyzed in the microbiology lab of INES-Ruhengeri. The result showed that Staphylococcus aureus was the most predominant with 22.5%. Lactobacillus and Citrobacter spp. were 12.5%; Pseudomonas aeruginosa, coagulase-negative Staphylococci, and Serratia marcescens were 10%; Escherichia coli was 7.5%; Klebsiella spp. and Providencia spp. were at 5%. The lowest prevalence was 2.5% of Enterobacter spp. and Salmonella spp. The threat of dissemination of isolated microorganisms is valid, since all devices evaluated in this study showed bacterial contamination of species associated to hospital-acquired infections. Special care should be taken when using electronic devices in healthcare settings in addition to disinfection to reduce the risk of transmission of bacterial agents. Further studies should evaluate the antibiotic susceptibility for better conclusive results since all isolated bacteria in this study were subjected to high resistance and were associated with nosocomial infections.

Genotypic and phenotypic changes of Staphylococcus epidermidis during relapse episodes in prosthetic joint infections

Staphylococcus epidermidis is a coagulase-negative bacterium capable of causing recurrent relapses in prosthetic joint infection (PJI). The aim of this study was to determine if Staphylococcus epidermidis isolates from patients with recurrent relapses of prosthetic joint infection (PJI) changed genotypically (pulsed-field gel electrophoresis (PFGE) pattern analysis and genes involved in biofilm formation) and phenotypically (antimicrobial resistance, biofilm formation) during the different episodes. Four patients with PJI recurrent relapses were evaluated clinically and microbiologically. Genotypic and phenotypic characteristics of 31 S. epidermidis isolates were determined. In all cases, PJI was treated with antimicrobial therapy and resection of the prosthesis without reimplantation. Months later, all patients had a relapse episode and treated with rifampin plus vancomycin and surgical debridement. Changes in the antibiotics resistance profile in isolates from patients 1 and 2 were observed in the two episodes. Patient 1 had four clones A, B, C, and D that were distributed differentially in the two episodes. Similarly, patients 2 and 3 had two clones and subclones (E-E1 and F-F1, respectively), and patient 4 had only the clone G in both episodes. The clone F formed small-colony variants (SCVs). High level of biofilm formation was found in all clones, except for clones D and G. Clones/subclones showed a genotypic variation in icaA, sdrF, bap, sesI, and embp genes. The principal coordinate analysis showed that all clones/subclones were different. These results showed that the initial infective clone of S. epidermidis from PJI, changed genotypically and phenotypically after a second relapse as a response to the treatment.

The Influence of Different Forms of Silver on Selected Pathogenic Bacteria

The application of silver nanoparticles as an antibacterial agent is becoming more common. Unfortunately, their effect on microorganisms is still not fully understood. Therefore, this paper attempts to investigate the influence of silver ions, biologically synthesized silver nanoparticles and nanoparticles functionalized with antibiotics on molecular bacteria profiles. The initial stage of research was aimed at the mechanism determination involved in antibiotics sorption onto nanoparticles' surface. For this purpose, the kinetics study was performed. Next, the functionalized formulations were characterized by Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS) and a zeta potential study. The results reveal that functionalization is a complex process, but does not significantly affect the stability of biocolloids. Furthermore, the antimicrobial assays, in most cases, have shown no increases in antibacterial activity after nanoparticle functionalization, which suggests that the functionalization process does not always generate the improved antimicrobial effect. Finally, the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) technique was employed to characterize the changes in the molecular profile of bacteria treated with various antibacterial agents. The recorded spectra proved many differences in bacterial lipids and proteins profiles compared to untreated cells. In addition, the statistical analysis of recorded spectra revealed the strain-dependent nature of stress factors on the molecular profile of microorganisms.

Antimicrobial Resistance Profiling of Coagulase-Negative Staphylococci in a Referral Center in South Italy: A Surveillance Study

Background:

CoNS are part of the normal flora of the skin, upper respiratory tract and human intestine. CoNS are able to colonize host tissues or inert materials such as prosthetics, heart valves, pacemakers, and urinary and venous catheters. They can also internalize in host cells, thus eluding immune defenses and attack by antibiotics.

Objective:

In this study, we collected the epidemiological data and determined the antibiotic susceptibility of 828 CoNS, collected in Garibaldi Hospital (Catania, Italy) between January 2016 and October 2018.

Methods:

Strains were evaluated by determining the Minimum Inhibitory Concentration (MIC) using the broth microdilution method, according to the guidelines of the Clinical and Laboratory Standards Institute. The antibiotic sensitivity pattern of CoNS against eighteen antibiotics was determined.

Results:

For all the 828 clinical isolates, varying resistance rates were observed: ampicillin (87%), penicillin (86%), amoxicillin-clavulanate (71%), oxacillin (70%), erythromycin (69%), azithromycin (68%), levofloxacin (55%), ciprofloxacin (54%), gentamycin (47%), moxifloxacin (42%), trimethoprim-sulfamethoxazole (30%), clindamycin (28%), tetracycline (24%), rifampicin (20%), quinupristin-dalfopristin (synercid) (4%). No strains investigated demonstrated resistance to teicoplanin, vancomycin and linezolid.

Conclusion:

Our results highlight the importance of monitoring the evolution of CoNS resistance in order to implement control measures and reduce the risk of spread in the population.

Draft Genome Sequence of Staphylococcus epidermidis UMB7765, Isolated from the Urobiome of a Woman with Recurrent Urinary Tract Infection

Staphylococcus epidermidis is a Gram-positive bacterium that is resistant to many antibiotics. Here, we present the 2.5-Mb draft genome of S. epidermidis UMB7765, isolated from a voided urine sample from a female with recurrent urinary tract infections.

Establishment and Characterization of Bacterial Infection of Breast Implants in a Murine Model

BACKGROUND

Staphylococcus epidermidis and Pseudomonas aeruginosa are the most common causes of Gram-positive and Gram-negative breast implant-associated infection. Little is known about how these bacteria infect breast implants as a function of implant surface characteristics and timing of infection.

OBJECTIVES

The aim of this work was to establish a mouse model for studying the impact of various conditions on breast implant infection.

METHODS

Ninety-one mice were implanted with 273 breast implant shells and infected with S. epidermidis or P. aeruginosa. Smooth, microtextured, and macrotextured breast implant shells were implanted in each mouse. Bacterial inoculation occurred during implantation or 1 day later. Implants were retrieved 1 or 7 days later. Explanted breast implant shells were sonicated, cultured, and colony-forming units determined or analyzed with scanning electron microscopy.

RESULTS

P. aeruginosa could be detected on all device surfaces at 1- and 7- days post infection (dpi), when mice were implanted and infected concurrently or when they were infected 1- day after implantation. However, P. aeruginosa infection was more robust on implant shells retrieved at 7 dpi and particularly on the macrotextured devices that were infected 1 day post implantation. S. epidermidis was mostly cleared from implants when mice were infected and implanted concurrently. Other the other hand, S. epidermidis could be detected on all device surfaces at 1 dpi and 2 days post implantation. However, S. epidermdis infection was suppressed by 7 dpi and 8 days post implantation.

CONCLUSIONS

S. epidermidis required higher inoculating doses to cause infection and was cleared within 7 days. P. aeruginosa infected at lower inoculating doses, with robust biofilms noted 7 days later.

Study on the Effects of Estradiol in Staphylococcus epidermidis Device-Related Capsule Formation

BACKGROUND

Capsular contracture, mainly caused by Staphylococcus epidermidis (S. epidermidis) biofilm formation, is a complex problem for breast cancer patients who undergo surgical prosthetic breast reconstruction. Estradiol has been reported to be involved in the formation of bacterial biofilms. Thus, the underlying mechanism of estradiol in capsular contracture needs to be investigated.

METHODS

Biofilm-related gene expressions were measured by qRT-PCR after sterilizing the silicone with bacterial suspension and E2 treatment in vitro. Rat models were established with bilateral ovariectomy operations and estradiol subcutaneous injections. The effects of estradiol on capsular contracture were detected by monitoring serum estradiol levels, bacterial infection rate in organs, biofilm formation and capsular contracture in vivo; inflammatory factors in vivo were examined as well. Biofilm on the silicone implants was observed under a scanning electron microscope.

RESULTS

Both positive regulatory genes and negative regulatory genes were increased by the high concentration of estradiol, suggesting that estradiol can promote the formation of biofilm by not only positive but also negative regulations. High estradiol levels increased bacterial infection rate in organs, biofilm formation and capsular contracture. Further, high estradiol caused a large number of inflammatory cells to infiltrate and caused serious inflammatory reactions that aggravate the immune imbalances of the host.

CONCLUSION

High estradiol levels contribute to increasing capsular contracture caused by S. epidermidis biofilm formation.

NO LEVEL ASSIGNED

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Mechanistic study on the inhibition of Staphylococcus epidermidis biofilm by agrC-specific binding polypeptide

Background

Considering the wide-spread misuse of antibiotics, the development of new antibacterial drugs may effectively prevent the emergence of antibiotic resistance in bacteria. The understanding of the mechanism underlying the Staphylococcus epidermidis agrC-specific binding polypeptide-mediated inhibition of S. epidermidis biofilm formation may supply ideas for the development of new antibacterial drugs.

Methods

S. epidermidis cells were cultured with different concentrations (0, 100, 200, 400, 800, and 1,600 µg/mL) of agrC-specific binding polypeptide (N1) and blank (N0). Crystal violet staining was performed to test the formation of biofilms and to determine the best concentration of agrC-specific binding polypeptides, and the bacterial inhibitory concentration was also determined. At different time points (6, 12, 18, 24, and 30 h), XTT assay was used to measure bacterial viability, and the real-time quantitative polymerase chain reaction was performed to measure the expression of atlE, icaA, fbe, and icaR genes. The sulfuric acid-phenol method was used to determine polysaccharide intercellular adhesin (PIA) levels.

Results

The biofilm formation ability of S. epidermidis was the lowest after treatment with 800 µg/mL agrC-specific binding polypeptide. After 6 h of culture, agrC-specific binding polypeptide upregulated the expression of atlE, icaA, fbe, and icaR and increased the bacterial viability. However, the polypeptide downregulated the expression of atlE, icaA, fbe, and icaR and inhibited S. epidermidis growth and PIA formation after 12 h of culture. Although agrC-specific binding polypeptide upregulated the expression of atlE, icaA, fbe, and icaR after 18 h, they inhibited bacterial growth and PIA formation.

Conclusions

Thus, agrC-specific binding polypeptide could downregulate the expression of atlE, icaA, fbe, and icaR and inhibit PIA formation by S. epidermidis after 12 h, demonstrating its transient inhibitory effects on the biofilm formation ability of S. epidermidis. Its effective concentration was 800 µg/mL.