The Staphylococcal Biofilm: Adhesins, Regulation, and Host Response

Comparative lipidomics profiles of planktonic and biofilms of methicillin-resistant and -susceptible Staphylococcus aureus

Staphylococcus aureus is a significant human pathogen causing acute life-threatening, and chronic infections often linked to biofilms. This study conducted a comparative lipidomic analysis of a methicillin-resistant (MRSA) and a methicillin-susceptible (MSSA) S. aureus strain in both planktonic and biofilm cultures using liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy. The developed protocol successfully differentiates between the strains in various living states (planktonic and biofilm) and growth media (Tryptic Soy Broth and Brain Heart Infusion) using S. aureus USA300 LAC (MRSA) and S. aureus Newman (MSSA). LC-MS and NMR lipidomics profiles revealed global differences and particular ones among the following classes of bacterial lipids: phosphatidylglycerols, diacylglycerols, monoglycosyldiacylglycerols, diglycosyldiacylglycerols, and cardiolipins. Lipid content was higher in the biofilm states for most of these classes. Growth media differences were significant, while differences between MRSA and MSSA were less pronounced but still detectable. Additionally, we provide data on hundreds of unknown compounds that differ based on living state, strain background, or growth media. This study offer insights into the dynamic nature of S. aureus lipid composition and the used methods are adaptable to other organisms.

Repurposing Benzbromarone as an Antibacterial Agent against Gram-Positive Bacteria

The rise of antibiotic-resistant Gram-positive pathogens, particularly methicillin-resistant Staphylococcus aureus (MRSA), presents a significant challenge in clinical settings. There is a critical need for new antibacterial agents to combat these resistant strains. Our study reveals that the uricosuric drug Benzbromarone (Benz) exhibits potent antibacterial activity against Gram-positive pathogens, with minimum inhibitory concentrations (MICs) ranging from 8 to 32 μg/mL and minimum bactericidal concentrations (MBCs) ranging from 32 to 128 μg/mL against clinical isolates of S. aureus, S. epidermidis, Enterococcus faecalis, and Streptococcus agalactiae. Furthermore, Benz significantly inhibits biofilm formation at subinhibitory concentrations and eradicates mature biofilms at higher concentrations. Benz also suppresses the hemolytic activity of S. aureus, indicating its potential to reduce virulence. Proteomic and in vitro induced resistance analyses indicate that Benz inhibits protein synthesis and turnover. Additionally, Benz induces membrane depolarization and increases membrane permeability, likely by targeting the membrane phospholipid phosphatidylethanolamine (PE). In the mouse wound infection model, Benz promotes wound healing and significantly reduces bacterial load. These findings suggest that Benz is a promising candidate for developing new antibacterial therapies against Gram-positive bacterial infections.

Investigating the Translational Value of Periprosthetic Joint Infection Models to Determine the Risk and Severity of Staphylococcal Biofilms

With the advent of antibiotic-eluting polymeric materials for targeting recalcitrant infections, using preclinical models to study biofilms are crucial for improving the treatment efficacy in periprosthetic joint infections. The stratification of risk and severity of infections is needed to develop an effective clinical dosing framework with better treatment outcomes. We use in vivo and in vitro implant-associated infection models to demonstrate that methicillin-sensitive and resistant Staphylococcus aureus (MSSA and MRSA) have model-dependent distinct implant and peri-implant tissue colonization patterns. The maturity of biofilms and the location (implant vs tissue) were found to influence the antibiotic susceptibility evolution profiles of MSSA and MRSA, and the models could capture the differing host-microbe interactions in vivo. Gene expression studies revealed the molecular heterogeneity of colonizing bacterial populations. The comparison and stratification of the risk and severity of infection across different preclinical models provided in this study can guide clinical dosing to prevent or treat PJI effectively.

Bacterial Communities and Their Role in Bacterial Infections

Since infections associated with microbial communities threaten human health, research is increasingly focusing on the development of biofilms and strategies to combat them. Bacterial communities may include bacteria of one or several species. Therefore, examining all the microbes and identifying individual community bacteria responsible for the infectious process is important. Rapid and accurate detection of bacterial pathogens is paramount in healthcare, food safety, and environmental monitoring. Here, we analyze biofilm composition and describe the main groups of pathogens whose presence in a microbial community leads to infection (Staphylococcus aureus, Enterococcus spp., Cutibacterium spp., bacteria of the HACEK, etc.). Particular attention is paid to bacterial communities that can lead to the development of device-associated infections, damage, and disruption of the normal functioning of medical devices, such as cardiovascular implants, biliary stents, neurological, orthopedic, urological and penile implants, etc. Special consideration is given to tissue-located bacterial biofilms in the oral cavity, lungs and lower respiratory tract, upper respiratory tract, middle ear, cardiovascular system, skeletal system, wound surface, and urogenital system. We also describe methods used to analyze the bacterial composition in biofilms, such as microbiologically testing, staining, microcolony formation, cellular and extracellular biofilm components, and other methods. Finally, we present ways to reduce the incidence of biofilm-caused infections.

Microbial signatures in chronic thromboembolic pulmonary hypertension thrombi: Insights from metagenomic profiling of fresh and organized thrombi

OBJECTIVE

Many studies have reported microbial signatures in thrombi at major vascular sites, such as the coronary artery and the middle cerebral artery, which are critical for maintaining proper blood flow and oxygenation. Chronic thromboembolic pulmonary hypertension (CTEPH) is a condition involving non-resolving thrombosis that has not been fully studied. This study explored the microbial taxonomy and functional profiles of both fresh and organized thrombi associated with CTEPH to investigate the role of microbiota in thrombus non-resolving.

METHODS

In this study, 12 CTEPH fresh thrombi and 12 organized thrombi were collected from 14 patients with CTEPH. Metagenomic sequencing was employed to explore the genomic information of all microorganisms in the thrombus samples.

RESULTS

Our data demonstrated a diverse range of microorganisms in CTEPH thrombi, whether fresh or organized. Notably, a considerable proportion (54.7 %) of sequencing data could not be classified into the relative microbial taxa, highlighting the complexity and novelty of the thrombus ecosystem. Although there were no significant differences in microbial community structure between the two groups, the abundance of dominant microbial species varied. Leuconostoc sp. DORA 2, Staphylococcus aureus, and Aliidongia dinghuensis were common dominant species in CTEPH thrombus. Organized thrombus significantly increased the relative abundance of Staphylococcus aureus, which was confirmed to effectively distinguish between organized and fresh thrombi by LeFSe analysis and random forest analysis. Functional annotation using both the KEGG and eggNOG databases revealed that organized thrombi exhibit stronger metabolic functions, particularly in amino acid metabolism.

CONCLUSIONS

Our findings suggest that microbial composition and function may play an important role in thrombus organization. Targeting inflammation to prevent thrombosis presents promising opportunities for further research in this area.

Biological Therapy on Infected Traumatic Wounds: A Case-Control Study

Background:Traumatic wound is a great challenging issue to surgeons, because of large in size, heavily contaminated, infected and unscenic. Infection proceeded to progressive tissue necrosis, septicemia, organ failure or even death. Majority has polymicrobial infections. Bacteriohage therapy will have revolutionized in the treatment of wound. The present study was planned to evaluate the efficacy of topical bacteriophage therapy on large traumatic wounds in comparison with conventional therapy. Methods:The Study conducted from Sept. 2018 to July 2020. Samples between 12- 60 years was taken into study. Customized bacteriophage applied over the wound after serial debridement in case and conventional dressing in control. Fifty four wounded person met the clinical inclusion criteria; 27 in each group. Wound swab and tissue biopsy was taken for bacterial isolation. Isolated specific phage was applied over the wound on alternate day till the wound become sterile and fit for further definitive management. Results: A significant and rapid improvement was observed in wound healing in cases then control group. Average number of day required for complete granulation of wound and attaining sterility was half in cases then control. The hospital stay of the patients on BT was half (20days) than those on CT (40 days). The financial analysis also favours the BT over CT as only 1/third expenditure incurred in BT group as compared to CT Conclusion:Topical Bacteriophage therapy is efficient, effective to clearing the infection in shorter length of time and cost effective for infected traumatic wounds as compared to conventional dressing.

The influence of marine fungal meroterpenoid meroantarctine A toward HaCaT keratinocytes infected with Staphylococcus aureus

A new biological activity was discovered for marine fungal meroterpenoid meroantarctine A with unique 6/5/6/6 polycyclic system. It was found that meroantarctine A can significantly reduce biofilm formation by Staphylococcus aureus with an IC50 of 9.2 µM via inhibition of sortase A activity. Co-cultivation of HaCaT keratinocytes with a S. aureus suspension was used as an in vitro model of skin infection. Treatment of S. aureus-infected HaCaT cells with meroantarctine A at 10 µM caused a reduction in the production of TNF-α, IL-18, NO, and ROS, as well as LDH release and caspase 1 activation in these cells and, finally, recovered the proliferation and migration of HaCaT cells in an in vitro wound healing assay up to the control level. Thus, meroantarctine A is a new promising antibiofilm compound which can effective against S. aureus caused skin infection.

Antibacterial Mechanisms and Clinical Impact of Sitafloxacin

Sitafloxacin is a 4th generation fluoroquinolone antibiotic with broad activity against a wide range of Gram-negative and Gram-positive bacteria. It is approved in Japan and used to treat pneumonia and urinary tract infections (UTIs) as well as other upper and lower respiratory infections, genitourinary infections, oral infections and otitis media. Compared to other fluoroquinolones, sitafloxacin displays a low minimal inhibitory concentration (MIC) for many bacterial species but also activity against anaerobes, intracellular bacteria, and persisters. Furthermore, it has also shown strong activity against biofilms of P. aeruginosa and S. aureus in vitro, which was recently validated in vivo with murine models of S. aureus implant-associated bone infection. Although limited in scale at present, the published literature supports the further evaluation of sitafloxacin in implant-related infections and other biofilm-related infections. The aim of this review is to summarize the chemical-positioning-based mechanisms, activity, resistance profile, and future clinical potential of sitafloxacin.

Green nanotechnology in phytosynthesis and its efficiency in inhibiting bacterial biofilm formation: implications for medicine

Nanotechnology is used in several biomedical applications, including antimicrobial and antibiofilm applications using nanomaterials. Bacterial biofilm varies according to the strain; the matrix is very strong and resistant. In this sense, phytosynthesis is an important method for combating bacterial biofilms through the use of metallic nanoparticles (silver, gold, or copper) with increased marketing and technical-scientific potential. In this review, we seek to gather the leading publications on the use of phytosynthesized metallic nanoparticles against bacterial biofilms. Furthermore, this study aims to understand the main characteristics and parameters of these nanomaterials, their antibiofilm efficiency, and the presence or absence of cytotoxicity in these developed technologies.

Cutibacterium acnes invades submicron osteocyte lacuno-canalicular networks following implant-associated osteomyelitis

Cutibacterium acnes, part of normal skin flora, is increasingly recognized as an opportunistic pathogen capable of causing chronic prosthetic joint infections (PJI) associated with total hip and knee arthroplasty. However, there is a paucity of literature examining the pathogenesis of C. acnes during PJI. To study this, we developed an implant-associated osteomyelitis murine model in which 8-10-week-old C57BL6 mice were subjected to transtibial implantation of titanium or stainless-steel L-shaped pins contaminated with C. acnes. Postsurgery, mice were killed on Days 14 and 28 for terminal assessments of (1) bacterial load in bone, implant, and internal organs (heart, spleen, kidney, and liver), (2) bone osteolysis (micro-CT), (3) abscess formation (histology), and (4) systematic electron microscopy (EM). In vitro scanning EM (SEM) confirmed that C. acnes can form biofilms on stainless-steel and titanium implants. In mice, C. acnes could persist for 28 days in the tibia. Also, we observed C. acnes dissemination to internal organs. C. acnes chronic osteomyelitis revealed markedly reduced bone osteolysis and abscess formation compared to Staphylococcus aureus infections. Importantly, transmission EM (TEM) investigation revealed the presence of C. acnes within canaliculi, demonstrating that C. acnes can invade the osteocyte lacuno-canalicular networks (OLCN) within bone. Our preliminary pilot study, for the first time, revealed that the OLCN in bone can be a reservoir for C. acnes and potentially provides a novel mechanism of why C. acnes chronic implant-associated bone infections are difficult to treat.

Point-Prevalence Survey of Antimicrobial Use and Healthcare-Associated Infections in Four Acute Care Hospitals in Kazakhstan

BACKGROUND/OBJECTIVES

Few studies have examined the prevalence of healthcare-associated infections (HAIs) and antimicrobial use (AMU) in acute care hospitals in Kazakhstan. This study aimed to address this gap by conducting a point-prevalence survey (PPS) of HAIs and AMU, as well as evaluating hospital antibiotic consumption via internationally recognized methodologies.

METHODS

PPS was conducted in four acute care hospitals in Kazakhstan on 11 May 2022, following the methodology of the European Center for Disease Prevention and Control, and included 701 patients. Antibiotic consumption in the same hospitals was assessed via the Global Antimicrobial Resistance and Use Surveillance System methodology.

RESULTS

HAIs were observed in 3.8% of patients (27/701), with intensive care unit wards accounting for 48.1% of these cases (13/27). Pseudomonas aeruginosa was the most frequently identified pathogen (5 out of 14 documented cases, 35.7%). Resistance to carbapenems was the most common resistance, followed by resistance to glycopeptides and third-generation cephalosporins. The rate of AMU was 38.2%, with an average of 1.37 antibiotics administered per patient. Surgical prophylaxis lasting more than one day was the most common indication for antimicrobial prescription (44.8%). Ceftriaxone and cefazolin are the most commonly used antibiotics.

CONCLUSIONS

The results of this study are important for understanding the current situation in Kazakhstan and for informing national antimicrobial stewardship and infection control strategies.

Horse Meat Microbiota: Determination of Biofilm Formation and Antibiotic Resistance of Isolated Staphylococcus Spp

Domestic horses could be bred for leisure activities and meat production, as is already the case in many countries. Horse meat is consumed in various countries, including Kazakhstan and Kyrgyzstan, and with the increase in this consumption, horses are registered as livestock by the Food and Agricultural Organization. In this study, horse meat microbiota of horse samples (n = 56; 32 samples from Kazakhstan and 24 samples from Kyrgyzstan) from two countries, Kazakhstan (n = 3) and Kyrgyzstan (n = 1), were investigated for the first time by next-generation sequencing and metabarcoding analysis. The results demonstrated that Firmicutes, Proteobacteria, and Actinobacteria were the dominant bacterial phyla in all samples. In addition, three (5.4%) Staphylococcus strains were isolated from the Uzynagash region, Kazakhstan. Staphylococcus strains were identified as Staphylococcus warneri, S. epidermidis, and S. pasteuri by partial 16S rRNA DNA gene Sanger sequencing. All three Staphylococcus isolates were nonbiofilm formers; only the S. pasteuri was detected as multidrug-resistant (resistant to penicillin, cefoxitin, and oxacillin). In addition, S. pasteuri was found to carry mecA, mecC, and tetK genes. This is the first study to detect potentially pathogenic Staphylococcus spp. in horse meat samples originating from Kazakhstan. In conclusion, it should be carefully considered that undercooked horse meat may pose a risk to consumers in terms of pathogens such as antibiotic-resistant Staphylococcus isolates.

In silico testing to identify compounds that inhibit ClfA and ClfB binding to the host for the formulation of future drugs against Staphylococcus aureus colonization and infection

Introduction

Staphylococcus aureus is a highly resistant pathogen. It has multiple virulence factors, which makes it one of the most pathogenic bacteria for humankind. The vast increase in antibiotic resistance in these bacteria is a warning of existing healthcare policies. Most of the available antibiotics are ineffective due to resistance; this situation requires the development of drugs that target specific proteins and are not susceptible to resistance.

Methods

In this study, we identified a compound that acts as an antagonist of ClfA and ClfB by inhibiting their binding to host cells.

Results

The shortlisted compound's binding activity was tested by docking and molecular dynamics during its interaction with proteins. The identified compound has excellent binding energy with both ClfA (-10.11 kcal/mol) and ClfB (-11.11 kcal/mol).

Discussion

The molecular dynamics of the protein and compound were stable and promising for further in vitro and in vivo tests. The performance of our compound was tested and compared with that of the control molecule allantodapsone, which was reported in a previous study as a pan inhibitor of the clumping factor. An ADMET study of our selected compound revealed its reliable drug likeliness. This compound is an ideal candidate for in vitro studies.

Low concentrations of tetrabromobisphenol A promote the biofilm formation of methicillin-resistant Staphylococcus aureus

The effect and underlying mechanism of tetrabromobisphenol A (TBBPA), a plastic additive, on biofilm formation of methicillin-resistant Staphylococcus aureus (MRSA USA300) remain unknown. This study first investigated the impact of different concentrations of TBBPA on the growth and biofilm formation of USA300. The results indicated that a low concentration (0.5 mg/L) of TBBPA promoted the growth and biofilm formation of USA300, whereas high concentrations (5 mg/L and 10 mg/L) of TBBPA had inhibitory effects. Further exploration revealed that the low concentration of TBBPA enhance biofilm formation by promoting the synthesis of extracellular proteins, release of extracellular DNA (eDNA), and production of staphyloxanthin. RTqPCR analysis demonstrated that the low concentration of TBBPA upregulated genes associated with extracellular protein synthesis (sarA, fnbA, fnbB, aur) and eDNA formation (atlA) and increased the expression of genes involved in staphyloxanthin biosynthesis (crtM), suggesting a potential mechanism for enhanced resistance of USA300 to adverse conditions. These findings shed light on how low concentrations of TBBPA facilitate biofilm formation in USA300 and highlight the indirect impact of plastic additives on pathogenic bacteria in terms of human health. In the future, in-depth studies about effects of plastic additives on pathogenicity of pathogenic bacteria should be conducted. CAPSULE: The protein and eDNA contents in biofilms of methicillin-resistant Staphylococcus aureus are increased by low concentrations of TBBPA.

Biofilm Growth on Orthopaedic Cerclage Materials: Nonmetallic Polymers Are Less Resistant to Methicillin-Resistant Staphylococcus Aureus Bacterial Adhesion

BACKGROUND

Data on bacterial adhesion to cerclage cables are sparse. We aimed to compare 5 cerclage products for methicillin-resistant Staphylococcus aureus (MRSA) adhesion to determine the claim: Are nonmetallic polymer cables more resistant to bacterial adhesion than common metallic wires and cables?

METHODS

The following 5 cerclage products were compared: (1) monofilament stainless steel (SS) wires; (2) multifilament SS cables; (3) multifilament cobalt chrome cables; (4) multifilament Vitallium alloy (cobalt-chrome-molybdenum [Co-Cr-Mo]) cables; and (5) multifilament nonmetallic polymer cables. Each was cut into 2 cm lengths and placed into 12-well plates. Of the wells, 5 were wire or cables in trypticase soy broth with MRSA, with the remaining wells being appropriate controls incubated for 24 hours at 37° C and 5% CO2 with shaking. Wires and cables were prepared and randomly imaged via scanning electron microscopy, with bacterial counts performed on 3 images of 3 different wires or cables per study group. The scanning electron microscopy technician and counting investigator were blinded. Additionally, SS wire and polymer cables were analyzed by microcalorimetry for metabolic activity and bacterial load.

RESULTS

Bacterial attachment differed significantly between study groups in the middle section (P = .0003). Post hoc comparison showed no difference between groups individually (all P > .05) apart from polymer cables (median 551 bacteria) having significantly increased attached bacteria compared to the Vitallium alloy cable (157, P = .0004), SS cable (101, P = .0004), and SS wire (211, P = .0004). There was no difference between polymer and cobalt chrome cables (133, P = .056). Microcalorimetry supported these results, as polymer cables had a shorter time to max heat flow (6.2 versus 7.5 hours, P = .006), increased max heat flow (117 versus 64 uW, P = .045), and increased colony-forming units, indicating an increased bacterial load compared to SS wires.

CONCLUSIONS

This in vitro study demonstrated that polymer cables have increased MRSA adhesion compared to common metallic wires and cables. Future studies are necessary to confirm the translation of increased bacterial adherence on polymer cables to increased rates of orthopaedic infections.

Sticking together: independent evolution of biofilm formation in different species of staphylococci has occurred multiple times via different pathways

BACKGROUND

Staphylococci cause a wide range of infections, including implant-associated infections which are difficult to treat due to the presence of biofilms. Whilst some proteins involved in biofilm formation are known, the differences in biofilm production between staphylococcal species remains understudied. Currently biofilm formation by Staphylococcus aureus is better understood than other members of the genus as more research has focused on this species.

RESULTS

We assembled a panel of 385 non-aureus Staphylococcus isolates of 19 species from a combination of clinical sources and reference strains. We used a high-throughput crystal violet assay to assess the biofilm forming ability of all strains and assign distinct biofilm formation categories. We compared the prevalence of Pfam domains between the categories and used machine learning to identify amino acid 20-mers linked to biofilm formation. This identified some domains within proteins already linked to biofilm formation and important domains not previously linked to biofilm formation in staphylococci. RT-qPCR confirmed the expression of selected genes predicted to encode important domains within biofilms in Staphylococcus epidermidis. The prevalence and distribution of biofilm associated domains showed a link to phylogeny, suggesting different Staphylococcus species have independently evolved different mechanisms of biofilm production.

CONCLUSIONS

This work has identified different routes to biofilm formation in diverse species of Staphylococcus and suggests independent evolution of biofilm has occurred multiple times across the genus. Understanding the mechanisms of biofilm formation in any given species is likely to require detailed study of relevant strains and the ability to generalise across the genus may be limited.

Mechanism of antibacterial resistance, strategies and next-generation antimicrobials to contain antimicrobial resistance: a review

Antibacterial drug resistance poses a significant challenge to modern healthcare systems, threatening our ability to effectively treat bacterial infections. This review aims to provide a comprehensive overview of the types and mechanisms of antibacterial drug resistance. To achieve this aim, a thorough literature search was conducted to identify key studies and reviews on antibacterial resistance mechanisms, strategies and next-generation antimicrobials to contain antimicrobial resistance. In this review, types of resistance and major mechanisms of antibacterial resistance with examples including target site modifications, decreased influx, increased efflux pumps, and enzymatic inactivation of antibacterials has been discussed. Moreover, biofilm formation, and horizontal gene transfer methods has also been included. Furthermore, measures (interventions) taken to control antimicrobial resistance and next-generation antimicrobials have been discussed in detail. Overall, this review provides valuable insights into the diverse mechanisms employed by bacteria to resist the effects of antibacterial drugs, with the aim of informing future research and guiding antimicrobial stewardship efforts.

Investigating the translational value of Periprosthetic Joint Infection (PJI) models to determine the risk and severity of Staphylococcal biofilms

With the advent of antibiotic-eluting polymeric materials for targeting recalcitrant infections, using preclinical models to study biofilm is crucial for improving the treatment efficacy in periprosthetic joint infections. The stratification of risk and severity of infections is needed to develop an effective clinical dosing framework with better outcomes. Here, using in-vivo and in-vitro implant-associated infection models, we demonstrate that methicillin-sensitive and resistant Staphylococcus aureus (MSSA and MRSA) have model-dependent distinct implant and peri-implant tissue colonization patterns. The maturity of biofilms and the location (implant vs tissue) were found to influence the antibiotic susceptibility evolution profiles of MSSA and MRSA and the models could capture the differing host-microbe interactions in vivo. Gene expression studies revealed the molecular heterogeneity of colonizing bacterial populations. The comparison and stratification of the risk and severity of infection across different preclinical models provided in this study can guide clinical dosing to effectively prevent or treat PJI.

Diclofenac sodium effectively inhibits the biofilm formation of Staphylococcus epidermidis

Staphylococcus epidermidis is an opportunistic pathogen commonly implicated in medical device-related infections. Its propensity to form biofilms not only leads to chronic infections but also exacerbates the issue of antibiotic resistance, necessitating high-dose antimicrobial treatments. In this study, we explored the use of diclofenac sodium, a non-steroidal anti-inflammatory drug, as an anti-biofilm agent against S. epidermidis. In this study, crystal violet staining and confocal laser scanning microscope analysis showed that diclofenac sodium, at subinhibitory concentration (0.4 mM), significantly inhibited biofilm formation in both methicillin-susceptible and methicillin-resistant S. epidermidis isolates. MTT assays demonstrated that 0.4 mM diclofenac sodium reduced the metabolic activity of biofilms by 25.21-49.01% compared to untreated controls. Additionally, the treatment of diclofenac sodium resulted in a significant decrease (56.01-65.67%) in initial bacterial adhesion, a crucial early phase of biofilm development. Notably, diclofenac sodium decreased the production of polysaccharide intercellular adhesin (PIA), a key component of the S. epidermidis biofilm matrix, in a dose-dependent manner. Real-time quantitative PCR analysis revealed that diclofenac sodium treatment downregulated biofilm-associated genes icaA, fnbA, and sigB and upregulated negative regulatory genes icaR and luxS, providing potential mechanistic insights. These findings indicate that diclofenac sodium inhibits S. epidermidis biofilm formation by affecting initial bacterial adhesion and the PIA synthesis. This underscores the potential of diclofenac sodium as a supplementary antimicrobial agent in combating staphylococcal biofilm-associated infections.

Residents or Tourists: Is the Lactating Mammary Gland Colonized by Residential Microbiota?

The existence of the human milk microbiome has been widely recognized for almost two decades, with many studies examining its composition and relationship to maternal and infant health. However, the richness and viability of the human milk microbiota is surprisingly low. Given that the lactating mammary gland houses a warm and nutrient-rich environment and is in contact with the external environment, it may be expected that the lactating mammary gland would contain a high biomass microbiome. This discrepancy raises the question of whether the bacteria in milk come from true microbial colonization in the mammary gland ("residents") or are merely the result of constant influx from other bacterial sources ("tourists"). By drawing together data from animal, in vitro, and human studies, this review will examine the question of whether the lactating mammary gland is colonized by a residential microbiome.

A review of chemical signaling mechanisms underlying quorum sensing and its inhibition in Staphylococcus aureus

Staphylococcus aureus is a significant bacterium responsible for multiple infections and is a primary cause of fatalities among patients in hospital environments. The advent of pathogenic bacteria such as methicillin-resistant S. aureus revealed the shortcomings of employing antibiotics to treat bacterial infectious diseases. Quorum sensing enhances S. aureus's survivability through signaling processes. Targeting the key components of quorum sensing has drawn much interest nowadays as a promising strategy for combating infections caused by bacteria. Concentrating on the accessory gene regulator quorum-sensing mechanism is the most commonly suggested anti-virulence approach for S.aureus. Quorum quenching is a common strategy for controlling illnesses triggered by microorganisms since it reduces the pathogenicity of bacteria and improves bacterial biofilm susceptibility to antibiotics, thus providing an intriguing prospect for drug discovery. Quorum sensing inhibition reduces selective stresses and constrains the emergence of antibiotic resistance while limiting bacterial pathogenicity. This review examines the quorum sensing mechanisms involved in S. aureus, quorum sensing targets and gene regulation, environmental factors affecting quorum sensing, quorum sensing inhibition, natural products as quorum sensing inhibitory agents and novel therapeutical strategies to target quorum sensing in S. aureus as drug developing technique to augment conventional antibiotic approaches.

Sialylation of dietary mucin modulate its digestibility and the gut microbiota of elderly individuals

Food-derived mucins are glycoproteins rich in sialic acid, but their digestive properties and potential health benefits for humans have been scarcely investigated. In this work, ovomucin (OVM, rich in N-acetylneuraminic acid, about 3 %), porcine small intestinal mucin (PSIM, rich in N-glycolylneuraminic acid, about 1 %), the desialylated OVM (AOVM) and the desialylated PSIM (APSIM) were selected to examine their digestion and their impact on the gut microbiota of elderly individuals. The results shown that, the proportion of low-molecular-weight proteins increased after simulated digestion of these four mucins, with concomitant comparable antioxidant activity observed. Desialylation markedly increased the degradation and digestion rate of mucins. In vitro fecal fermentation was conducted with these mucins using fecal samples from individuals of different age groups: young, low-age and high-age elderly. Fecal fermentation with mucin digestive solution stimulated the production of organic acids in the group with fecal sample of the elderly individuals. Among them, the OVM group demonstrated the most favorable outcomes. The OVM and APSIM groups elevated the relative abundance of beneficial bacteria such as Lactobacillus and Bifidobacterium, while diminishing the presence of pathogenic bacteria such as Klebsiella. Conversely, the probiotic effects of AOVM and PSIM were attenuated or even exhibited adverse effects. Hence, mucins originating from different sources and possessing distinct glycosylation patterns exhibit diverse biological functions. Our findings can offer valuable insights for developing a well-balanced and nutritious diet tailored to the elderly population.

Risk factors and prediction model construction for peripherally inserted central catheter-related infections

Objective

To establish a predictive modeling for the risk of bloodstream infection associated with peripherally inserted central catheter (PICC).

Methods

Patients receiving PICC treatment in Shenzhen People's Hospital from June 2020 to December 2020 were retrospectively enrolled and divided into the infection group and the non-infection group according to the presence and absence of PICC-related infections. Then, relevant clinical information of patients was collected and the predictors of PICC-related infection were screened by the least absolute shrinkage and selection operator regression (LASSO) model. Besides, multivariate logistic regression was used to analyze the influencing factors of PICC-related infection, A nomogram was constructed based on the results of the multivariate analysis. Ultimately, a receiver operating characteristic (ROC) curve was plotted to analyze the application value of influencing factors to predict PICC-related infections.

Results

A total of 505 patients were included, including 75 patients with PICC-related infections (14.85%). The main pathogen was gram-positive cocci. The predictors screened by LASSO included age >60 years, catheter movement, catheter maintenance cycle, insertion technique, immune function, complications, and body temperature ≥37.2 °C before PICC placement. Multivariate logistic regression analysis showed that independent risk factors of infections related to PICC included age >60 years [odds ratio (OR) = 1.722; 95% confidence interval (CI) = 1.312-3.579; P = 0.006], catheter movement (OR = 1.313; 95% CI = 1.119-3.240; P = 0.014), catheter maintenance cycle >7 days (OR = 2.199; 95% CI = 1.677-4.653; P = 0.000), direct insertion (OR = 1.036; 95% CI = 1.019-2.743; P = 0.000), poor immune function (OR = 2.322; 95% CI = 2.012-4.579; P = 0.000), complications (OR = 1.611; 95% CI = 1.133-3.454; P = 0.019), and body temperature ≥37.2 °C before PICC placement (OR = 1.713; 95% CI = 1.172-3.654; P = 0.012). Besides, the area under the ROC curve was 0.889.

Conclusion

PICC-related infections are associated with factors such as age >60 years, catheter movement, catheter maintenance cycle, insertion technique, immune function, complications, and body temperature ≥37.2 °C before PICC placement. Additionally, the LASSO model is moderately predictive for predicting the occurrence of PICC-related infections.

Host-derived protease promotes aggregation of Staphylococcus aureus by cleaving the surface protein SasG

Staphylococcus aureus is one of the leading causes of hospital-acquired infections, many of which begin following attachment and accumulation on indwelling medical devices or diseased tissue. These infections are often linked to the establishment of biofilms, but another often overlooked key characteristic allowing S. aureus to establish persistent infection is the formation of planktonic aggregates. Such aggregates are physiologically similar to biofilms and protect pathogens from innate immune clearance and increase antibiotic tolerance. The cell-wall-associated protein SasG has been implicated in biofilm formation via mechanisms of intercellular aggregation but the mechanism in the context of disease is largely unknown. We have previously shown that the expression of cell-wall-anchored proteins involved in biofilm formation is controlled by the ArlRS-MgrA regulatory cascade. In this work, we demonstrate that the ArlRS two-component system controls aggregation, by repressing the expression of sasG by activation of the global regulator MgrA. We also demonstrate that SasG must be proteolytically processed by a non-staphylococcal protease to induce aggregation and that strains expressing functional full-length sasG aggregate significantly upon proteolysis by a mucosal-derived host protease found in human saliva. We used fractionation and N-terminal sequencing to demonstrate that human trypsin within saliva cleaves within the A domain of SasG to expose the B domain and induce aggregation. Finally, we demonstrated that SasG is involved in virulence during mouse lung infection. Together, our data point to SasG, its processing by host proteases, and SasG-driven aggregation as important elements of S. aureus adaptation to the host environment.IMPORTANCEHere, we demonstrate that the Staphylococcus aureus surface protein SasG is important for cell-cell aggregation in the presence of host proteases. We show that the ArlRS two-component regulatory system controls SasG levels through the cytoplasmic regulator MgrA. We identified human trypsin as the dominant protease triggering SasG-dependent aggregation and demonstrated that SasG is important for S. aureus lung infection. The discovery that host proteases can induce S. aureus aggregation contributes to our understanding of how this pathogen establishes persistent infections. The observations in this study demonstrate the need to strengthen our knowledge of S. aureus surface adhesin function and processing, regulation of adhesin expression, and the mechanisms that promote biofilm formation to develop strategies for preventing chronic infections.

Antibacterial copper-filled TiO2 coating of cardiovascular implants to prevent infective endocarditis-A pilot study

BACKGROUND

Infective endocarditis (IE) poses a significant health risk, especially in patients with prosthetic heart valves. Despite advances in treatment, mortality rates remain high. This study aims to investigate the antibacterial properties of a copper titanium dioxide (4× Cu-TiO2) coating on cardiovascular implants against Staphylococcus aureus, a common causative agent of IE.

METHODS

Titanium oxide carriers functionalized with copper ions were employed as an antibacterial coating for heart and vascular prostheses. The coating's antibacterial efficacy was assessed using S. aureus ATCC 29213. Microscopic evaluations were conducted on both biological and artificial materials. Antibacterial activity was qualitatively assessed via a modified disc diffusion method and quantitatively measured through colony counts in NaCl suspensions.

RESULTS

The coating process was successfully applied to all tested cardiovascular prosthetic materials. Qualitative assessments of antibacterial effectiveness revealed an absence of bacterial growth in the area directly beneath the coated valve. Quantitative evaluations showed a significant reduction in bacterial colonization on coated mechanical valves, with 2.95 × 104 CFU per valve, compared to 1.91 × 105 CFU in control valves.

CONCLUSIONS

The 4× Cu-TiO2 coating demonstrated promising antibacterial properties against S. aureus, suggesting its potential as an effective strategy for reducing the risk of bacterial colonization of cardiovascular implants. Further studies are needed to assess the longevity of the coating and its efficacy against other pathogens.

Transvenous lead extraction safety and efficacy in infected and noninfected patients using mechanical-only tools: Prospective registry from a high-volume center

BACKGROUND

Transvenous lead extraction (TLE) is a well-established treatment option for patients with cardiac implantable electronic devices (CIED) complications.

OBJECTIVE

The purpose of this study was to evaluate the safety and efficacy of TLE in CIED infection and non-CIED infection patients.

METHODS

Consecutive patients who underwent TLE between 2016 and 2022 entered the EXTRACT Registry. Models of prediction were constructed for periprocedural clinical and procedural success and the incidence of major complications, including death in 30 days.

RESULTS

The registry enrolled 504 patients (mean age 66.6 ± 12.8 years; 65.7% male). Complete procedural success was achieved in 474 patients (94.0%) and clinical success in 492 patients (97.6%). The total number of major and minor complications was 16 (3.2%) and 51 (10%), respectively. Three patients (0.6%) died during the procedure. New York Heart Association functional class IV and C-reactive protein levels defined before the procedure were independent predictors of any major complication, including death in 30 days in CIED infection patients. The time since the last preceding procedure and platelet count before the procedure were independent predictors of any major complication, including death in 30 days in non-CIED infection patients.

CONCLUSIONS

TLE is safe and successfully performed in most patients, with a low major complication rate. CIED infection patients demonstrate better periprocedural clinical success and complete procedural success. However, CIED infection predicts higher 30-day mortality compared with non-CIED infection patients. Predictors of any major complication, including death in 30 days, differ between CIED infection and non-CIED infection patients.

Deciphering the dynamics of methicillin-resistant Staphylococcus aureus biofilm formation: from molecular signaling to nanotherapeutic advances

Methicillin-resistant Staphylococcus aureus (MRSA) represents a global threat, necessitating the development of effective solutions to combat this emerging superbug. In response to selective pressures within healthcare, community, and livestock settings, MRSA has evolved increased biofilm formation as a multifaceted virulence and defensive mechanism, enabling the bacterium to thrive in harsh conditions. This review discusses the molecular mechanisms contributing to biofilm formation across its developmental stages, hence representing a step forward in developing promising strategies for impeding or eradicating biofilms. During staphylococcal biofilm development, cell wall-anchored proteins attach bacterial cells to biotic or abiotic surfaces; extracellular polymeric substances build scaffolds for biofilm formation; the cidABC operon controls cell lysis within the biofilm, and proteases facilitate dispersal. Beside the three main sequential stages of biofilm formation (attachment, maturation, and dispersal), this review unveils two unique developmental stages in the biofilm formation process for MRSA; multiplication and exodus. We also highlighted the quorum sensing as a cell-to-cell communication process, allowing distant bacterial cells to adapt to the conditions surrounding the bacterial biofilm. In S. aureus, the quorum sensing process is mediated by autoinducing peptides (AIPs) as signaling molecules, with the accessory gene regulator system playing a pivotal role in orchestrating the production of AIPs and various virulence factors. Several quorum inhibitors showed promising anti-virulence and antibiofilm effects that vary in type and function according to the targeted molecule. Disrupting the biofilm architecture and eradicating sessile bacterial cells are crucial steps to prevent colonization on other surfaces or organs. In this context, nanoparticles emerge as efficient carriers for delivering antimicrobial and antibiofilm agents throughout the biofilm architecture. Although metal-based nanoparticles have been previously used in combatting biofilms, its non-degradability and toxicity within the human body presents a real challenge. Therefore, organic nanoparticles in conjunction with quorum inhibitors have been proposed as a promising strategy against biofilms. As nanotherapeutics continue to gain recognition as an antibiofilm strategy, the development of more antibiofilm nanotherapeutics could offer a promising solution to combat biofilm-mediated resistance.

Staphylococcus aureus and biofilms: transmission, threats, and promising strategies in animal husbandry

Staphylococcus aureus (S. aureus) is a common pathogenic bacterium in animal husbandry that can cause diseases such as mastitis, skin infections, arthritis, and other ailments. The formation of biofilms threatens and exacerbates S. aureus infection by allowing the bacteria to adhere to pathological areas and livestock product surfaces, thus triggering animal health crises and safety issues with livestock products. To solve this problem, in this review, we provide a brief overview of the harm caused by S. aureus and its biofilms on livestock and animal byproducts (meat and dairy products). We also describe the ways in which S. aureus spreads in animals and the threats it poses to the livestock industry. The processes and molecular mechanisms involved in biofilm formation are then explained. Finally, we discuss strategies for the removal and eradication of S. aureus and biofilms in animal husbandry, including the use of antimicrobial peptides, plant extracts, nanoparticles, phages, and antibodies. These strategies to reduce the spread of S. aureus in animal husbandry help maintain livestock health and improve productivity to ensure the ecologically sustainable development of animal husbandry and the safety of livestock products.

Bacteriophage vB_SepP_134 and Endolysin LysSte_134_1 as Potential Staphylococcus-Biofilm-Removing Biological Agents

Bacteria of the genus Staphylococcus are significant challenge for medicine, as many species are resistant to multiple antibiotics and some are even to all of the antibiotics we use. One of the approaches to developing new therapeutics to treat staphylococcal infections is the use of bacteriophages specific to these bacteria or the lytic enzymes of such bacteriophages, which are capable of hydrolyzing the cell walls of these bacteria. In this study, a new bacteriophage vB_SepP_134 (St 134) specific to Staphylococcus epidermidis was described. This podophage, with a genome of 18,275 bp, belongs to the Andhravirus genus. St 134 was able to infect various strains of 12 of the 21 tested coagulase-negative Staphylococcus species and one clinical strain from the Staphylococcus aureus complex. The genes encoding endolysin (LysSte134_1) and tail tip lysin (LysSte134_2) were identified in the St 134 genome. Both enzymes were cloned and produced in Escherichia coli cells. The endolysin LysSte134_1 demonstrated catalytic activity against peptidoglycans isolated from S. aureus, S. epidermidis, Staphylococcus haemolyticus, and Staphylococcus warneri. LysSte134_1 was active against S. aureus and S. epidermidis planktonic cells and destroyed the biofilms formed by clinical strains of S. aureus and S. epidermidis.

Staphylococcus aureus surface attachment selectively influences tolerance against charged antibiotics

The threat of infection during implant placement surgery remains a considerable burden for millions of patients worldwide. To combat this threat, clinicians employ a range of anti-infective strategies and practices. One of the most common interventions is the use of prophylactic antibiotic treatment during implant placement surgery. However, these practices can be detrimental by promoting the resilience of biofilm-forming bacteria and enabling them to persist throughout treatment and re-emerge later, causing a life-threatening infection. Thus, it is of the utmost importance to elucidate the events occurring during the initial stages of bacterial surface attachment and determine whether any biological processes may be targeted to improve surgical outcomes. Using gene expression analysis, we identified a cellular mechanism of S. aureus which modifies its cell surface charge following attachment to a medical grade titanium surface. We determined the upregulation of two systems involved in the d-alanylation of teichoic acids and the lysylation of phosphatidylglycerol. We supported these molecular findings by utilizing synchrotron-sourced attenuated total reflection Fourier-transform infrared microspectroscopy to analyze the biomolecular properties of the S. aureus cell surface following attachment. As a direct consequence, S. aureus quickly becomes substantially more tolerant to the positively charged vancomycin, but not the negatively charged cefazolin. The present study can assist clinicians in rationally selecting the most potent antibiotic in prophylaxis treatments. Furthermore, it highlights a cellular process that could potentially be targeted by novel technologies and strategies to improve the outcome of antibiotic prophylaxis during implant placement surgery. STATEMENT OF SIGNIFICANCE: The antibiotic tolerance of bacteria in biofilm is a well-established phenomenon. However, the physiological adaptations employed by Staphylococcus aureus to increase its antibiotic tolerance during the early stages of surface attachment are poorly understood. Using multiple techniques, including gene expression analysis and synchrotron-sourced Fourier-transform infrared microspectroscopy, we generated insights into the physiological response of S. aureus following attachment to a medical grade titanium surface. We showed that this phenotypic transition enables S. aureus to better tolerate the positively charged vancomycin, but not the negatively charged cefazolin. These findings shed light on the antibiotic tolerance mechanisms employed by S. aureus to survive prophylactically administered antibiotics and can help clinicians to protect patients from infections.

Bacteriophage therapy for drug-resistant Staphylococcus aureus infections

Drug-resistant Staphylococcus aureus stands as a prominent pathogen in nosocomial and community-acquired infections, capable of inciting various infections at different sites in patients. This includes Staphylococcus aureus bacteremia (SaB), which exhibits a severe infection frequently associated with significant mortality rate of approximately 25%. In the absence of better alternative therapies, antibiotics is still the main approach for treating infections. However, excessive use of antibiotics has, in turn, led to an increase in antimicrobial resistance. Hence, it is imperative that new strategies are developed to control drug-resistant S. aureus infections. Bacteriophages are viruses with the ability to infect bacteria. Bacteriophages, were used to treat bacterial infections before the advent of antibiotics, but were subsequently replaced by antibiotics due to limited theoretical understanding and inefficient preparation processes at the time. Recently, phages have attracted the attention of many researchers again because of the serious problem of antibiotic resistance. This article provides a comprehensive overview of phage biology, animal models, diverse clinical case treatments, and clinical trials in the context of drug-resistant S. aureus phage therapy. It also assesses the strengths and limitations of phage therapy and outlines the future prospects and research directions. This review is expected to offer valuable insights for researchers engaged in phage-based treatments for drug-resistant S. aureus infections.

Synergistic use of anti-inflammatory ketorolac and gentamicin to target staphylococcal biofilms

BACKGROUND

While antibiotics remain our primary tools against microbial infection, increasing antibiotic resistance (inherent and acquired) is a major detriment to their efficacy. A practical approach to maintaining or reversing the efficacy of antibiotics is the use of other commonly used therapeutics, which show synergistic antibacterial action with antibiotics. Here, we investigated the extent of antibacterial synergy between the antibiotic gentamicin and the anti-inflammatory ketorolac regarding the dynamics of biofilm growth, the rate of acquired resistance, and the possible mechanism of synergy.

METHODS

Control (ATCC 12600, ATCC 35984) and clinical strains (L1101, L1116) of Staphylococcus aureus and Staphylococcus epidermidis with varying antibiotic susceptibility profiles were used in this study to simulate implant-material associated low-risk and high-risk biofilms in vitro. The synergistic action of gentamicin sulfate (GS) and ketorolac tromethamine (KT), against planktonic staphylococcal strains were determined using the fractional inhibitory concentration measurement assay. Nascent (6 h) and established (24 h) biofilms were grown on 316L stainless steel plates and the synergistic biofilm eradication activity was determined and characterized using adherent bacteria count, minimum biofilm eradication concentration (MBEC) measurement for GS, visualization by live/dead imaging, scanning electron microscopy, gene expression of biofilm-associated genes, and bacterial membrane fluidity assessment.

RESULTS

Gentamicin-ketorolac (GS-KT) combination demonstrated synergistic antibacterial action against planktonic Staphylococci. Control and clinical strains showed distinct biofilm growth dynamics and an increase in biofilm maturity was shown to confer further resistance to gentamicin for both 'low-risk' and 'high-risk' biofilms. The addition of ketorolac enhanced the antibiofilm activity of gentamicin against acquired resistance in staphylococcal biofilms. Mechanistic studies revealed that the synergistic action of gentamicin-ketorolac interferes with biofilm morphology and subverts bacterial stress response altering bacterial physiology, membrane dynamics, and biofilm properties.

CONCLUSION

The results of this study have a significant impact on the local administration of antibiotics and other therapeutic agents commonly used in the prevention and treatment of orthopaedic infections. Further, these results warrant the study of synergy for the concurrent or sequential administration of non-antibiotic drugs for antimicrobial effect.

Transcriptomic analysis of cell envelope inhibition by prodigiosin in methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading threat to public health as it is resistant to most currently available antibiotics. Prodigiosin is a secondary metabolite of microorganisms with broad-spectrum antibacterial activity. This study identified a significant antibacterial effect of prodigiosin against MRSA with a minimum inhibitory concentration as low as 2.5 mg/L. The results of scanning electron microscopy, crystal violet staining, and confocal laser scanning microscopy indicated that prodigiosin inhibited biofilm formation in S. aureus USA300, while also destroying the structure of the cell wall and cell membrane, which was confirmed by transmission electron microscopy. At a prodigiosin concentration of 1.25 mg/L, biofilm formation was inhibited by 76.24%, while 2.5 mg/L prodigiosin significantly reduced the vitality of MRSA cells in the biofilm. Furthermore, the transcriptomic results obtained at 1/8 MIC of prodigiosin indicated that 235and 387 genes of S. aureus USA300 were significantly up- and downregulated, respectively. The downregulated genes were related to two-component systems, including the transcriptional regulator LytS, quorum sensing histidine kinases SrrB, NreA and NreB, peptidoglycan biosynthesis enzymes (MurQ and GlmU), iron-sulfur cluster repair protein ScdA, microbial surface components recognizing adaptive matrix molecules, as well as the key arginine synthesis enzymes ArcC and ArgF. The upregulated genes were mainly related to cell wall biosynthesis, as well as two-component systems including vancomycin resistance-associated regulator, lipoteichoic acid biosynthesis related proteins DltD and DltB, as well as the 9 capsular polysaccharide biosynthesis proteins. This study elucidated the molecular mechanisms through which prodigiosin affects the cell envelope of MRSA from the perspectives of cell wall synthesis, cell membrane and biofilm formation, providing new potential targets for the development of antimicrobials for the treatment of MRSA.

Quercetin targets SarA of methicillin-resistant Staphylococcus aureus to mitigate biofilm formation

IMPORTANCE

Anti-biofilm is an important strategy against Staphylococcus aureus chronic infection. SarA is a positive regulator of biofilm formation in S. aureus. In this study, we identified the SarA inhibitor quercetin using computer simulation screening. Previous studies have shown that quercetin inhibits biofilm; however, the underlying mechanism remains unknown. This study revealed the inhibitory effect of quercetin on the SarA protein. We also isolated the SarA protein and confirmed its interaction with quercetin in vitro. Besides, the inhibitory effect of quercetin on the transcription and translation levels of the SarA protein was also determined. The effects of quercetin on S. aureus biofilm inhibition and biofilm components were consistent with the changes in the transcription level of biofilm-related genes regulated by SarA. In summary, our study revealed the mechanism by which quercetin affects biofilm formation by inhibiting the transcriptional regulator SarA of S. aureus.

Altered quorum sensing and physiology of Staphylococcus aureus during spaceflight detected by multi-omics data analysis

Staphylococcus aureus colonizes the nares of approximately 30% of humans, a risk factor for opportunistic infections. To gain insight into S. aureus virulence potential in the spaceflight environment, we analyzed RNA-Seq, cellular proteomics, and metabolomics data from the "Biological Research in Canisters-23" (BRIC-23) GeneLab spaceflight experiment, a mission designed to measure the response of S. aureus to growth in low earth orbit on the international space station. This experiment used Biological Research in Canisters-Petri Dish Fixation Units (BRIC-PDFUs) to grow asynchronous ground control and spaceflight cultures of S. aureus for 48 h. RNAIII, the effector of the Accessory Gene Regulator (Agr) quorum sensing system, was the most highly upregulated gene transcript in spaceflight relative to ground controls. The agr operon gene transcripts were also highly upregulated during spaceflight, followed by genes encoding phenol-soluble modulins and secreted proteases, which are positively regulated by Agr. Upregulated spaceflight genes/proteins also had functions related to urease activity, type VII-like Ess secretion, and copper transport. We also performed secretome analysis of BRIC-23 culture supernatants, which revealed that spaceflight samples had increased abundance of secreted virulence factors, including Agr-regulated proteases (SspA, SspB), staphylococcal nuclease (Nuc), and EsxA (secreted by the Ess system). These data also indicated that S. aureus metabolism is altered in spaceflight conditions relative to the ground controls. Collectively, these data suggest that S. aureus experiences increased quorum sensing and altered expression of virulence factors in response to the spaceflight environment that may impact its pathogenic potential.

Phenotypic and Genotypic Assays to Evaluate Coagulase-Negative Staphylococci Biofilm Production in Bloodstream Infections

Coagulase-negative staphylococci (CoNS) are commensal on human body surfaces and, for years, they were not considered a cause of bloodstream infection and were often regarded as contamination. However, the involvement of CoNS in nosocomial infection is increasingly being recognized. The insertion of cannulas and intravascular catheters represents the primary source of CoNS entry into the bloodstream, causing bacteremia and sepsis. They owe their pathogenic role to their ability to produce biofilms on surfaces, such as medical devices. In this study, we evaluate the adhesive capacity of CoNS isolated from blood cultures by comparing a spectrophotometric phenotypic assay with genotypic analysis based on the evidence of the ica operon. We retrospectively reviewed the database of CoNS isolated from blood cultures from January to December 2021 that were considered responsible for 361 bloodstream infections. Eighty-nine CoNS were selected among these. Our data show that Staphylococcus epidermidis was the predominant species isolated, expressing greater adhesive capacities, especially those with the complete operon. Knowledge of the adhesive capabilities of a microorganism responsible for sepsis can be useful in implementing appropriate corrective and preventive measures, since conventional antibiotic therapy cannot effectively eradicate biofilms.

The Effect of Topical Antibiotic Powder Application in the Emergency Department on Deep Fracture-Related Infection in Type III Open Lower Extremity Fractures

OBJECTIVE

Despite advances in management, open fractures are at an elevated risk for deep fracture-related infection (FRI). Time to systemic antibiotic (ABX) administration and intraoperative topical administration of ABX powder have been used to decrease FRI risk. The purpose of this study was to determine whether topical application of antibiotic powder to type III open lower extremity fractures immediately on presentation to the emergency department (ED) reduces the rate of FRI.

METHODS

DESIGN

Prospective cohort compared with retrospective historical control.

SETTING

Level I trauma center.

INTERVENTION

Application of 1 g of vancomycin and 1.2 g of tobramycin powder directly to open fracture wounds on presentation to the ED.

PATIENT SELECTION CRITERIA

Patients with type III open lower extremity fractures treated from July 1, 2019, to September 17, 2022, who received topical ABX powder in the ED were compared with patients from a 4-year historical cohort from July 1, 2015, to June 30, 2019, who were treated without topical ABX powder.

OUTCOME MEASURES AND COMPARISONS

Development of a FRI within 6 months of follow-up. Patient demographics, injury characteristics, and postoperative data were analyzed as risk factors for FRI.

RESULTS

Sixty-six patients received topical ABX powder in the ED and were compared with 129 patients who were treated without topical ABX powder. The rate of FRI in the trial group was 6/66 (9.09%) versus 22/129 (17.05%) in the control cohort ( P = 0.133). Multivariate analysis demonstrated higher body mass index as a risk factor for development of FRI ( P = 0.036).

CONCLUSION

No statistically significant difference in rates of FRI in open lower extremity fractures treated with immediate topical ABX administration in the ED versus standard-of-care treatment without topical ABX was found. These findings may have been limited by insufficient power. Further large-scale study is warranted to determine the significance of topical antibiotic powder application in the ED.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Biofilms: A developmental niche for vancomycin-intermediate Staphylococcus aureus

Staphylococcus aureus are gram-positive bacteria responsible for a wide array of diseases, ranging from skin and soft tissue infections to more chronic illnesses such as toxic shock syndrome, osteomyelitis, and endocarditis. Vancomycin is currently one of the most effective antibiotics available in treating patients infected with methicillin-resistant S. aureus (MRSA), however the emergence of vancomycin-resistant S. aureus (VRSA), and more commonly vancomycin-intermediate S. aureus (VISA), threaten the future efficacy of vancomycin. Intermediate resistance to vancomycin occurs due to mutations within the loci of Staphylococcal genes involved in cell wall formation such as rpoB, graS, and yycG. We hypothesized the VISA phenotype may also arise as a result of the natural stress occurring within S. aureus biofilms, and that this phenomenon is mediated by the RecA/SOS response. Wildtype and recA null mutant/lexAG94E strains of S. aureus biofilms were established in biofilm microtiter assays or planktonic cultures with or without the addition of sub-inhibitory concentrations of vancomycin (0.063 mg/l - 0.25 mg/L ciprofloxacin, 0.5 mg/l vancomycin). Efficiency of plating techniques were used to quantify the subpopulation of biofilm-derived S. aureus cells that developed vancomycin-intermediate resistance. The results indicated that a greater subpopulation of cells from wildtype biofilms (4.16 × 102 CFUs) emerged from intermediate-resistant concentrations of vancomycin (4 μg/ml) compared with the planktonic counterpart (1.53 × 101 CFUs). Wildtype biofilms (4.16 × 102 CFUs) also exhibited greater resistance to intermediate-resistant concentrations of vancomycin compared with strains deficient in the recA null mutant (8.15 × 101 CFUs) and lexA genes (8.00 × 101 CFUs). While the VISA phenotype would be an unintended consequence of genetic diversity and potentially gene transfer in the biofilm setting, it demonstrates that mutations occurring within biofilms allow for S. aureus to adapt to new environments, including the presence of widely used antibiotics.

Clonal Diversity, Antibiotic Resistance, and Virulence Factor Prevalence of Community Associated Staphylococcus aureus in Southeastern Virginia

Staphylococcus aureus is a significant human pathogen with a formidable propensity for antibiotic resistance. Worldwide, it is the leading cause of skin and soft tissue infections (SSTI), septic arthritis, osteomyelitis, and infective endocarditis originating from both community- and healthcare-associated settings. Although often grouped by methicillin resistance, both methicillin-resistant (MRSA) and methicillin-sensitive (MSSA) strains are known to cause significant pathologies and injuries. Virulence factors and growing resistance to antibiotics play major roles in the pathogenicity of community-associated strains. In our study, we examined the genetic variability and acquired antibiograms of 122 S. aureus clinical isolates from SSTI, blood, and urinary tract infections originating from pediatric patients within the southeast region of Virginia, USA. We identified a suite of clinically relevant virulence factors and evaluated their prevalence within these isolates. Five genes (clfA, spA, sbi, scpA, and vwb) with immune-evasive functions were identified in all isolates. MRSA isolates had a greater propensity to be resistant to more antibiotics as well as significantly more likely to carry several virulence factors compared to MSSA strains. Further, the carriage of various genes was found to vary significantly based on the infection type (SSTI, blood, urine).

Ciprofloxacin enhances the biofilm formation of Staphylococcus aureus via an agrC-dependent mechanism

Staphylococcus aureus readily forms biofilms on host tissues and medical devices, enabling its persistence in chronic infections and resistance to antibiotic therapy. The accessory gene regulator (Agr) quorum sensing system plays a key role in regulating S. aureus biofilm formation. This study reveals the widely used fluoroquinolone antibiotic, ciprofloxacin, strongly stimulates biofilm formation in methicillin-resistant S. aureus, methicillin-sensitive S. aureus, and clinical isolates with diverse genetic backgrounds. Crystal violet staining indicated that ciprofloxacin induced a remarkable 12.46- to 15.19-fold increase in biofilm biomass. Confocal laser scanning microscopy revealed that ciprofloxacin induced denser biofilms. Phenotypic assays suggest that ciprofloxacin may enhance polysaccharide intercellular adhesin production, inhibit autolysis, and reduce proteolysis during the biofilm development, thus promoting initial adhesion and enhancing biofilm stability. Mechanistically, ciprofloxacin significantly alters the expression of various biofilm-related genes (icaA, icaD, fnbA, fnbB, eap, emp) and regulators (agrA, saeR). Gene knockout experiments revealed that deletion of agrC, rather than saeRS, abolishes the ciprofloxacin-induced enhancement of biofilm formation, underscoring the key role of agrC. Thermal shift assays showed ciprofloxacin binds purified AgrC protein, thereby inhibiting the Agr system. Molecular docking results further support the potential interaction between ciprofloxacin and AgrC. In summary, subinhibitory concentrations of ciprofloxacin stimulate S. aureus biofilm formation via an agrC-dependent pathway. This inductive effect may facilitate local infection establishment and bacterial persistence, ultimately leading to therapeutic failure.

Whole-Genome Investigation of Zoonotic Transmission of Livestock-Associated Methicillin-Resistant Staphylococcus aureus Clonal Complex 398 Isolated from Pigs and Humans in Thailand

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) has been widespread globally in pigs and humans for decades. Nasal colonization of LA-MRSA is regarded as an occupational hazard to people who are regularly involved in livestock production. Our previous study suggested pig-to-human transmission caused by LA-MRSA clonal complex (CC) 398, using traditional molecular typing methods. Instead, this study aimed to investigate the zoonotic transmission of LA-MRSA CC398 using whole genome sequencing (WGS) technologies. A total of 63 LA-MRSA isolates were identified and characterized in Thailand. Further, the 16 representatives of LA-MRSA CC9 and CC398, including porcine and worker isolates, were subjected to WGS on the Illumina Miseq platform. Core-genome single nucleotide polymorphism (SNP)-based analyses verify the zoonotic transmission caused by LA-MRSA CC398 in two farms. WGS-based characterization suggests the emergence of a novel staphylococcal cassette chromosome (SCC) mec type, consisting of multiple cassette chromosome recombinase (ccr) gene complexes via genetic recombination. Additionally, the WGS analyses revealed putative multi-resistant plasmids and several cross-resistance genes, conferring resistance against drugs of last resort used in humans such as quinupristin/dalfopristin and linezolid. Significantly, LA-MRSA isolates, in this study, harbored multiple virulence genes that may become a serious threat to an immunosuppressive population, particularly for persons who are in close contact with LA-MRSA carriers.

A novel small-molecule compound S-342-3 effectively inhibits the biofilm formation of Staphylococcus aureus

IMPORTANCE

Biofilms are an important virulence factor in Staphylococcus aureus and are characterized by a structured microbial community consisting of bacterial cells and a secreted extracellular polymeric matrix. Inhibition of biofilm formation is an effective measure to control S. aureus infection. Here, we have synthesized a small molecule compound S-342-3, which exhibits potent inhibition of biofilm formation in both MRSA and MSSA. Further investigations revealed that S-342-3 exerts inhibitory effects on biofilm formation by reducing the production of polysaccharide intercellular adhesin and preventing bacterial adhesion. Our study has confirmed that the inhibitory effect of S-342-3 on biofilm is achieved by downregulating the expression of genes responsible for biofilm formation. In addition, S-342-3 is non-toxic to Galleria mellonella larvae and A549 cells. Consequently, this study demonstrates the efficacy of a biologically safe compound S-342-3 in inhibiting biofilm formation in S. aureus, thereby providing a promising antibiofilm agent for further research.

Diabetes mellitus promotes the nasal colonization of high virulent Staphylococcus aureus through the regulation of SaeRS two-component system

Diabetic foot infections are a common complication of diabetes. Staphylococcus aureus is frequently isolated from diabetic foot infections and commonly colonizes human nares. According to the study, the nasal microbiome analysis revealed that diabetic patients had a significantly altered nasal microbial composition and diversity. Typically, the fasting blood glucose (FBG) level had an impact on the abundance and sequence type (ST) of S. aureus in diabetic patients. We observed that highly virulent S. aureus ST7 strains were more frequently colonized in diabetic patients, especially those with poorly controlled FBG, while ST59 was dominant in healthy individuals. S. aureus ST7 strains were more resistant to human antimicrobial peptides and formed stronger biofilms than ST59 strains. Critically, S. aureus ST7 strains displayed higher virulence compared to ST59 strains in vivo. The dominance of S. aureus ST7 strains in hyperglycemic environment is due to the higher activity of the SaeRS two-component system (TCS). S. aureus ST7 strains outcompeted ST59 both in vitro, and in nasal colonization model in diabetic mice, which was abolished by the deletion of the SaeRS TCS. Our data indicated that highly virulent S. aureus strains preferentially colonize diabetic patients with poorly controlled FBG through SaeRS TCS. Detection of S. aureus colonization and elimination of colonizing S. aureus are critical in the care of diabetic patients with high FBG.

The impact of dioctyl phthalate exposure on multiple organ systems and gut microbiota in mice

Dioctyl phthalate, commonly known as bis(2-ethylhexyl) phthalate (DEHP), is a widely used plasticizer in various industries and has been shown to directly or indirectly impact human health. However, there is a lack of comprehensive studies evaluating the potential health risks associated with DEHP accumulation in different organs across various age groups. This study aimed to assess the effects of low (50 mg/kg·bw) and high (500 mg/kg·bw) doses of DEHP on five different organs in mice at young (4-week-old) and aged (76-week-old) life stages. Our findings revealed that both low and high doses of DEHP exposure led to significant dose-dependent inflammation in the liver, spleen, and kidney. Furthermore, regardless of age, DEHP exposure resulted in elevated activity of alanine aminotransferase (ALT) and alkaline phosphatase (ALP) in the liver, as well as increased levels of creatinine (Cr) and urea in the kidney. Moreover, analysis of the fecal microbiota using 16S rRNA sequencing demonstrated that DEHP exposure disrupted the homeostasis of the gut microbiota, characterized by an increased abundance of pathogenic bacteria such as Desulfovibrio and Muribaculum, and a decreased abundance of beneficial bacteria like Lactobacillus. This study provides compelling evidence that DEHP at different concentrations can induce damage to multiple organs and disrupt gut microbiota composition. These findings lay the groundwork for further investigations into DEHP toxicity in various human organs, contributing to a better understanding of the potential health risks associated with DEHP exposure.

Migratory Deposition of Calcium Pyrophosphate in an Older Patient With Several Femoral Neck Implant Infection Episodes: A Case Report

This case report describes an 86-year-old female patient who presented with complex post-surgical complications following orthopedic surgery for a femoral neck fracture. Initially diagnosed with septic shock due to methicillin-resistant Staphylococcus aureus (MRSA) bacteremia at the surgical site, the patient's treatment course was complicated, involving multiple hospital transfers and varying treatments, including antibiotics and surgical drainage. Despite the absence of infection indicators post treatment, the patient later developed severe thigh pain and was found to have migratory pseudogout, an unusual diagnosis in the context of MRSA and post-surgical complications. This report emphasizes the diagnostic challenges in distinguishing between surgical site infections and other inflammatory conditions like migratory pseudogout, particularly in older patients with comorbidities. It underscores the importance of comprehensive evaluations and the need for general physicians to maintain a broad differential diagnosis when managing post-surgical infections. The case highlights the persistence and recurrence risk of MRSA infections, even post-appropriate antibiotic therapy, and the necessity of considering migratory pseudogout in patients with recurrent infections and systemic soft tissue involvement. The insights from this case contribute to the understanding of complex post-surgical complications and advocate for meticulous assessment and tailored treatment strategies in similar clinical scenarios.

High prevalence of Panton-Valentine Leucocidin among Staphylococcus coagulans isolated from dogs in Rio de Janeiro

AIMS

The purpose of this study was to characterize the capacity for biofilm formation, antimicrobial resistance rates, and search for genetic determinants of resistance and virulence in the species.

METHODS AND RESULTS

Strains were collected from asymptomatic and infected dogs. Identification was conducted using matrix-assisted laser desorption ionization-time of flight (MALDI-TOF), antimicrobial susceptibility using disk diffusion and PCR targeting mecA. Biofilm formation was evaluated on a microtiter plate assay. A total of 27 strains were selected for whole-genome sequencing. We identified 111 Staphylococcus coagulans. The highest number was obtained from infected dogs. The highest resistance rates were observed for penicillin, gentamicin, and ciprofloxacin/erythromycin. Twelve strains were characterized as resistant to methicillin. All isolates had the ability to form biofilm and were strong producers. Among Methicillin Resistant Staphylococcus coagulans (MRSC), SCCmec types IIIA, and Vc were identified. Acquired resistance genes, such as aac(6')-aph(2''), tet(K), blaZ, qacG, qacJ, and erm(C) were found. Different virulence genes were identified. Of note, Panton-Valentine Leucocidin was highly prevalent among the isolates.

CONCLUSION

Staphylococcus coagulans had a high isolation rate among infected dogs and demonstrated significant resistance to commonly used antibiotics such as penicillin and gentamicin.

Staphylococcus aureus Orbital Abscess With Impending Compressive Optic Neuropathy in an Immunocompetent Individual With Subclinical Bacteriuria: A Case Report

This is a case of an orbital abscess evidenced radiologically in a 41-year-old female with no comorbidities. She was healthy and had no history of trauma or infection of the adjacent structures. She denied having symptoms of upper or lower respiratory and urinary tract infections. The decision for surgical drainage was made following a slow response to antimicrobial agents after 24 hours, a progressive painful erythematous eyelid swelling, and further deterioration of vision. Her clinical condition and visual acuity improved following cutaneous incision and drainage. Culture and sensitivity results for urine and orbital abscess were positive for Staphylococcus (S.) aureus. The patient regained full visual recovery without any sequelae. In conclusion, an orbital abscess is a blinding and life-threatening condition that rarely occurs in immunocompetent individuals and uncommonly arises from distant sources. A high index of suspicion, early institution of appropriate diagnostic imaging, and aggressive medical and surgical treatment are necessary for a favorable visual outcome in orbital abscess cases.

Chemical Composition and Evaluation of Antibacterial, Antibiofilm, and Mutagenic Potentials of a Propolis Sample from the Atlantic Forest of Midwest Brazil

Sixteen triterpenoids with various skeletal types, five phenylpropanoid derivatives, and two flavonoids were isolated from a propolis sample produced by Apis mellifera collected in the Atlantic Forest of Midwest Brazil. Among these compounds, six triterpenes, namely 3β,20R-dihydroxylanost-24-en-3-yl-palmitate, (23E)-25-methoxycycloartan-23-en-3-one, 24-methylenecycloartenone, epi-lupeol, epi-α-amyrin, and epi-β-amyrin are being reported for the first time in propolis, while cycloartenone, (E)-cinnamyl benzoate, and (E)-cinnamyl cinnamate are new findings in Brazilian propolis. The presence of cycloartane- and lanostane-type triterpenoids, the latter being a class of compounds of restricted distribution in propolis worldwide, has not been reported in propolis from Midwest Brazil until now. The ethyl acetate phase obtained from the ethanol extract was effective in preventing biofilm formation by Staphylococcus aureus, with an inhibition rate of about 96 % at 0.5 mg.mL-1 , and with quercetin isolated as one of its active constituents. In contrast, the hexane phase exhibited notable antibacterial activity against Pseudomonas aeruginosa, inhibiting bacterial growth by 92 % at 0.5 mg.mL-1 ; however, none of the triterpenoids isolated from this phase proved active against this pathogen. The ethanol extract was neither toxic nor mutagenic at the concentrations tested, as determined by the in vivo SMART assay on Drosophila melanogaster, even under conditions of high metabolic activation.

Microbial Analysis of Obturators During Maxillofacial Prosthodontic Treatment Over an 8-Year Period

The aim of the study was to investigate the microbial colonization (by Candida species, anaerobic and facultative anaerobic bacteria) of maxillary obturators used for the restoration of maxillary defects, including during radiotherapy.

Retrospective cohort study.

Fifteen patients requiring a maxillary obturator prosthesis had swabs of their obturators and adjacent tissues taken at different stages of their treatment over a period of 8 years.

Identification of microbial species from the swabs was carried out using randomly amplified polymorphic DNA polymerase chain reaction (RAPD PCR) analysis, checkerboard DNA-DNA hybridization, CHROMagar Candida chromogenic agar, and DNA sequencing.

Candida species were detected in all patients and all patients developed mucositis and candidiasis during radiotherapy which was associated with an increase in colonization of surfaces with Candida spp., particularly C albicans. Microbial colonization increased during radiotherapy and as an obturator aged, and decreased following a reline, delivery of a new prosthesis, or antifungal treatment during radiotherapy.

Microbial colonization of maxillary obturators was related to the stage of treatment, age of the obturator material, radiotherapy and antifungal medications, and antifungal treatment may be recommended if C albicans colonization of palatal tissues is greater than 105 colony-forming units per cm2 following the first week of radiotherapy.

The combinatorial applications of 1,4-naphthoquinone and tryptophan inhibit the biofilm formation of Staphylococcus aureus

Microorganisms embedded within an extracellular polymeric matrix are known as biofilm. The extensive use of antibiotics to overcome the biofilm-linked challenges has led to the emergence of multidrug-resistant strains. Staphylococcus aureus is one such nosocomial pathogen that is known to cause biofilm-linked infections. Thus, novel strategies have been adopted in this study to inhibit the biofilm formation of S. aureus. Two natural compounds, namely, 1,4-naphthoquinone (a quinone derivative) and tryptophan (aromatic amino acid), have been chosen as they could independently show efficient antibiofilm activity. To enhance the antibiofilm potential, the two compounds were combined and tested against the same organism. Several experiments like crystal violet (CV) assay, protein estimation, extracellular polymeric substance (EPS) extraction, and estimation of metabolic activity confirmed that the combination of the two compounds could significantly inhibit the biofilm formation of S. aureus. To comprehend the underlying mechanism, efforts were further directed to understand whether the two compounds could inhibit biofilm formation by compromising the cell surface hydrophobicity of the bacteria. The results revealed that the cell surface hydrophobicity got reduced by ~ 49% when the compounds were applied together. Thus, the combinations could show enhanced antibiofilm activity by attenuating cell surface hydrophobicity. Further studies revealed that the selected concentrations of the compounds could disintegrate (~ 70%) the pre-existing biofilm of the test bacteria without showing any antimicrobial activity. Hence, the combined application of tryptophan and 1,4-naphthoquinone could be used to inhibit the biofilm threats of S. aureus.