A new anti-infective strategy to reduce the spreading of antibiotic resistance by the action on adhesion-mediated virulence factors in Staphylococcus aureus

Serratiopeptidase exhibits antibiofilm activity through the proteolytic function of N-terminal domain and versatile function of the C-terminal domain

BACKGROUND

Serratiopeptidase, a serine protease traditionally used as an oral anti-inflammatory drug has been found to show antibiofilm action. Structurally, it comprises of two distinct domains; viz-the N-terminal catalytic domain (Ncat) and a C-terminal RTX (Repeat-In-Toxin) domain (Crtx). Understanding the antibiofilm action of the serratiopeptidase molecule, as well as the antibiofilm action of each of its two domains, was the objective of this study.

RESULTS

Separate clones to express the complete recombinant serratiopeptidase protein and its variant containing a mutation in the catalytic site, the N-terminal catalytic domain and its mutant, and the C-terminal Repeat-In-Toxin domain were prepared, and the proteins were purified. The impact of these proteins on pre-existing biofilms, as well as their effect upon addition of these proteins during biofilm formation was investigated.

CONCLUSIONS

In our investigation, we have been able to analyze the antibiofilm action of serratiopeptidase in detail. Obtained results conclude that while N-terminally located proteolytic domain of serratiopeptidase conventionally acts against biofilms by hydrolytic activity, the C-terminal domain regulates or prevents biofilm formation by yet unknown mechanism in addition to its known function as an C-terminal located calcium modulated internal chaperone ensuring the proper folding and secretion of the molecule. The study's findings give new evidence that the Crtx domain plays a significant role in antibiofilm action. The proteolytic Ncat domain breaks down pre-formed biofilms. The C-terminal domain, on the other hand, acts as an inhibitor of biofilm formation by regulating or preventing biofilm development.

Advances and challenges in serratiopeptidase topical formulation

Enzymes are a key part of most metabolic processes and are required for the correct functioning of the human body, either directly or indirectly. Proteolytic enzymes aid in the digestion of proteins in the body. Proteolytic enzymes are created in the pancreas naturally, but they can also be found in certain diets. Serratiopeptidase is an enzyme found in the stomach wall of silkworms and produced from S. marcescens strain. Less solubility, toxicity, instability, incompatibility, and less penetration are all common issues with Serratiopeptidase drug delivery. Because of its proteinaceous nature, serratiopeptidase is susceptible to enzymatic breakdown in the gastrointestinal system. It also has a low permeability through the intestinal barrier due to its hydrophilic nature. Depending on the features of the medicine, a suitable delivery mechanism is required. Topical formulation may eliminate the risk of gastric degradation of drug and increase direct permeation through skin and show effects. Topical SRP may effectively lower inflammatory markers, as it has been found to have superior anti-inflammatory effects than topical NSAIDs. Serratiopeptidase topical formulations could be more effective than nonsteroidal anti-inflammatory medications in treating local inflammation. This article reviews studies on various topical formulations.

Unveiling antibiofilm potential: proteins from Priestia sp. targeting Staphylococcus aureus biofilm formation

Staphylococcus aureus is the etiologic agent of many nosocomial infections, and its biofilm is frequently isolated from medical devices. Moreover, the dissemination of multidrug-resistant (MDR) strains from this pathogen, such as methicillin-resistant S. aureus (MRSA) strains, is a worldwide public health issue. The inhibition of biofilm formation can be used as a strategy to weaken bacterial resistance. Taking that into account, we analysed the ability of marine sponge-associated bacteria to produce antibiofilm molecules, and we found that marine Priestia sp., isolated from marine sponge Scopalina sp. collected on the Brazilian coast, secretes proteins that impair biofilm development from S. aureus. Partially purified proteins (PPP) secreted after 24 hours of bacterial growth promoted a 92% biofilm mass reduction and 4.0 µg/dL was the minimum concentration to significantly inhibit biofilm formation. This reduction was visually confirmed by light microscopy and Scanning Electron Microscopy (SEM). Furthermore, biochemical assays showed that the antibiofilm activity of PPP was reduced by ethylenediaminetetraacetic acid (EDTA) and 1,10 phenanthroline (PHEN), while it was stimulated by zinc ions, suggesting an active metallopeptidase in PPP. This result agrees with mass spectrometry (MS) identification, which indicated the presence of a metallopeptidase from the M28 family. Additionally, whole-genome sequencing analysis of Priestia sp. shows that gene ywad, a metallopeptidase-encoding gene, was present. Therefore, the results presented herein indicate that PPP secreted by the marine Priestia sp. can be explored as a potential antibiofilm agent and help to treat chronic infections.

An up-to-date review of biomedical applications of serratiopeptidase and its biobetter derivatives as a multi-potential metalloprotease

Serratiopeptidase is a bacterial metalloprotease used in a variety of medical applications. The multidimensional properties of serratiopeptidase make it noticeable as a miraculous enzyme. Anti-coagulant, anti-inflammatory and anti-biofilm activity of serratiopeptidase making it useful in reducing pain and swelling associated with various conditions including arthritis, diabetes, cancer, swelling, pain and also thrombolytic disorders. It breaks down fibrin, thins the fluids formed during inflammation and due to its anti-biofilm activity, can be used in the combination of antibiotics to reduce development of antibiotic resistance. However, some drawbacks like sensitivity to environmental conditions and low penetration into cells due to its large size have limited its usage as a potent pharmaceutical agent. To overcome such limitations, improved versions of the enzyme were introduced using protein engineering in our previous studies. Novel functional serratiopeptidases with shorter length and higher stability have seemingly created a hope for using this enzyme as a more effective therapeutic enzyme. This review explains the structural properties and functional aspects of serratiopeptidase, its main characteristics and properties, pre-clinical and clinical applications of the enzyme, improved qualities of the modified forms, different formulations of the enzyme, and the potential future developments.

Preparation and Physicochemical Characterization of Hyaluronic Acid-Lysine Nanogels Containing Serratiopeptidase to Control Biofilm Formation

Remarkable resistance of bacterial biofilms to high doses of antimicrobials and antibiotics is one of their main challenges. Encapsulation of proteolytic enzymes is one of the suggested strategies to tackle this problem. In this regard, the antibacterial and anti-biofilm activity of biocompatible hyaluronic acid- Lysine nanogels containing serratiopeptidase (SRP-loaded HA-Lys nanogel) was assessed against P. aeruginosa and S. aureus strains. SRP-loaded HA-Lys nanogel was prepared using dropping method and optimized by Box-Behnken experimental design. These formulations were studied for physical characterization, release profile, stability, bioactivity, and anti-biofilm effects. The particle size, polydispersity index (PDI), and surface charge were measured by Zetasizer Nano ZS. The average particle size and zeta potential of the optimum sample were 156 nm and -14.1 mV, respectively. SRP release showed an initial burst followed by sustained release and the highest release was around 77%. Enzyme biological activity data revealed the higher efficiency of free SRP compared to SRP-loaded HA-Lys nanogel. The time-kill assay showed that both forms of SRP-loaded HA-Lys nanogel and blank HA-Lys nanogel showed significant antimicrobial activity against examined bacteria in comparison to the free enzyme. The obtained results demonstrated improved anti-biofilm efficacy and down regulation of tested biofilm genes for both SRP-loaded HA-Lys nanogel 100% and blank HA-Lys nanogel 100% compared to SRP 100%.

In vitro and in silico evaluation of the serrapeptase effect on biofilm and amyloids of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an emerging threat for hospitalized and cystic fibrosis patients. Biofilm, a microbial community embedded in extracellular polymeric substance, fortifies bacteria against the immune system. In biofilms, the expression of functional amyloids is linked with highly aggregative, multi-resistant strains, and chronic infections. Serrapeptase (SPT), a protease possessing similar or superior anti-microbial properties with many antibiotics, presents anti-amyloid potential. However, studies on the employment of SPT against Pseudomonas biofilms and Fap amyloid, or the possible mechanisms of action are scarce. Here, SPT inhibited biofilm formation of P. aeruginosa ATCC 27853 on both plastic and glass surfaces, with an IC50 of 11.26 µg/mL and 0.27 µg/mL, respectively. The inhibitory effect of SPT on biofilm was also verified with optical microscopy of crystal violet-stained biofilms and with confocal microscopy. Additionally, SPT caused a dose-dependent decrease of bacterial viability (IC50 of 3.07 µg/mL) as demonstrated by MTT assay. Reduction of bacterial functional amyloids was also demonstrated, employing both fluorescence microscopy with thioflavin T and photometrical determination of Congo-red-positive compounds. Both viability and functional amyloids correlated significantly with biofilm inhibition. Finally, in silico molecular docking studies provided a mechanistic insight into the interaction of SPT with FapC or FapD, proving that both peptides are possible targets of SPT. These results offer new insights into the biofilm formation of P. aeruginosa and potentiate the involvement of SPT in the prevention and eradication of Pseudomonas biofilms. KEY POINTS: • Serrapeptase inhibits biofilm formation of P. aeruginosa on plastic and glass. • Biofilm inhibition correlated with reduced viability and functional amyloid levels. • In silico studies indicated that serrapeptase may target FapC and FapD peptides.

Serrapeptase impairs biofilm, wall, and phospho-homeostasis of resistant and susceptible Staphylococcus aureus

Staphylococcus aureus biofilms are implicated in hospital infections due to elevated antibiotic and host immune system resistance. Molecular components of cell wall including amyloid proteins, peptidoglycans (PGs), and lipoteichoic acid (LTA) are crucial for biofilm formation and tolerance of methicillin-resistant S. aureus (MRSA). Significance of alkaline phosphatases (ALPs) for biofilm formation has been recorded. Serrapeptase (SPT), a protease of Serratia marcescens, possesses antimicrobial properties similar or superior to those of many antibiotics. In the present study, SPT anti-biofilm activity was demonstrated against S. aureus (ATCC 25923, methicillin-susceptible strain, methicillin-susceptible S. aureus (MSSA)) and MRSA (ST80), with IC₅₀ values of 0.67 μg/mL and 7.70 μg/mL, respectively. SPT affected bacterial viability, causing a maximum inhibition of - 46% and - 27%, respectively. Decreased PGs content at [SPT] ≥ 0.5 μg/mL and ≥ 8 μg/mL was verified for MSSA and MRSA, respectively. In MSSA, LTA levels decreased significantly (up to - 40%) at lower SPT doses but increased at the highest dose of 2 μg/mL, a counter to spectacularly increased cellular and secreted LTA levels in MRSA. SPT also reduced amyloids of both strains. Additionally, intracellular ALP activity decreased in both MSSA and MRSA (up to - 85% and - 89%, respectively), while extracellular activity increased up to + 482% in MSSA and + 267% in MRSA. Altered levels of DING proteins, which are involved in phosphate metabolism, in SPT-treated bacteria, were also demonstrated here, implying impaired phosphorus homeostasis. The differential alterations in the studied molecular aspects underline the differences between MSSA and MRSA and offer new insights in the treatment of resistant bacterial biofilms. KEY POINTS: • SPT inhibits biofilm formation in methicillin-resistant and methicillin-susceptible S. aureus. • SPT treatment decreases bacterial viability, ALP activity, and cell wall composition. • SPT-treated bacteria present altered levels of phosphate-related DING proteins.

Serratiopeptidase Affects the Physiology of Pseudomonas aeruginosa Isolates from Cystic Fibrosis Patients

Pseudomonas aeruginosa is frequently involved in cystic fibrosis (CF) airway infections. Biofilm, motility, production of toxins and the invasion of host cells are different factors that increase P. aeruginosa's virulence. The sessile phenotype offers protection to bacterial cells and resistance to antimicrobials and host immune attacks. Motility also contributes to bacterial colonization of surfaces and, consequently, to biofilm formation. Furthermore, the ability to adhere is the prelude for the internalization into lung cells, a common immune evasion mechanism used by most intracellular bacteria, such as P. aeruginosa. In previous studies we evaluated the activity of metalloprotease serratiopeptidase (SPEP) in impairing virulence-related properties in Gram-positive bacteria. This work aimed to investigate SPEP's effects on different physiological aspects related to the virulence of P. aeruginosa isolated from CF patients, such as biofilm production, pyoverdine and pyocyanin production and invasion in alveolar epithelial cells. Obtained results showed that SPEP was able to impair the attachment to inert surfaces as well as adhesion/invasion of eukaryotic cells. Conversely, SPEP's effect on pyocyanin and pyoverdine production was strongly strain-dependent, with an increase and/or a decrease of their production. Moreover, SPEP seemed to increase swarming motility and staphylolytic protease production. Our results suggest that a large number of clinical strains should be studied in-depth before drawing definitive conclusions. Why different strains sometimes react in opposing ways to a specific treatment is of great interest and will be the object of future studies. Therefore, SPEP affects P. aeruginosa's physiology by differently acting on several bacterial factors related to its virulence.

Non-antibiotic strategies for prevention and treatment of internalized Staphylococcus aureus

Staphylococcus aureus (S. aureus) infections are often difficult to cure completely. One of the main reasons for this difficulty is that S. aureus can be internalized into cells after infecting tissue. Because conventional antibiotics and immune cells have difficulty entering cells, the bacteria can survive long enough to cause recurrent infections, which poses a serious burden in healthcare settings because repeated infections drastically increase treatment costs. Therefore, preventing and treating S. aureus internalization is becoming a research hotspot. S. aureus internalization can essentially be divided into three phases: (1) S. aureus binds to the extracellular matrix (ECM), (2) fibronectin (Fn) receptors mediate S. aureus internalization into cells, and (3) intracellular S. aureus and persistence into cells. Different phases require different treatments. Many studies have reported on different treatments at different phases of bacterial infection. In the first and second phases, the latest research results show that the cell wall-anchored protein vaccine and some microbial agents can inhibit the adhesion of S. aureus to host cells. In the third phase, nanoparticles, photochemical internalization (PCI), cell-penetrating peptides (CPPs), antimicrobial peptides (AMPs), and bacteriophage therapy can effectively eliminate bacteria from cells. In this paper, the recent progress in the infection process and the prevention and treatment of S. aureus internalization is summarized by reviewing a large number of studies.

Multi-targeted metallo-ciprofloxacin derivatives rationally designed and developed to overcome antimicrobial resistance

Antimicrobial resistance is a major global threat to human health due to the rise, spread and persistence of multi-drug-resistant bacteria or 'superbugs'. There is an urgent need to develop novel chemotherapeutics to overcome this overarching challenge. The authors derivatized a clinically used fluoroquinolone antibiotic ciprofloxacin (Cip), and complexed it to a copper phenanthrene framework. This resulted in the development of two novel metallo-antibiotics of general formula [Cu(N,N)(CipHA)]NO₃ where N,N represents a phenanthrene ligand and CipHA represents a hydroxamic acid of Cip derivative. Comprehensive studies, including a detailed proteomic study in which Staphylococcus aureus cells were exposed to the complexes, were undertaken to gain an insight into their mode of action. These new complexes possess potent antibacterial activity against S. aureus and methicillin-resistant S. aureus. In addition, they were found to be well tolerated in vivo in Galleria mellonella larvae, which has both functional and structural similarities to the innate immune system of mammals. These findings suggest that proteins involved in virulence, pathogenesis, and the synthesis of nucleotides and DNA repair mechanisms are most affected. In addition, both complexes affected similar cell pathways when compared with clinically used Cip, including cationic antimicrobial peptide resistance. The Cu-DPPZ-CipHA (DPPZ = dipyrido[3,2-a:2',3'-c]phenazine) analogue also induces cell leakage, which leads to an altered proteome indicative of reduced virulence and increased stress.

Staphylococcus aureus Internalization in Osteoblast Cells: Mechanisms, Interactions and Biochemical Processes. What Did We Learn from Experimental Models?

Bacterial internalization is a strategy that non-intracellular microorganisms use to escape the host immune system and survive inside the human body. Among bacterial species, Staphylococcus aureus showed the ability to interact with and infect osteoblasts, causing osteomyelitis as well as bone and joint infection, while also becoming increasingly resistant to antibiotic therapy and a reservoir of bacteria that can make the infection difficult to cure. Despite being a serious issue in orthopedic surgery, little is known about the mechanisms that allow bacteria to enter and survive inside the osteoblasts, due to the lack of consistent experimental models. In this review, we describe the current knowledge about S. aureus internalization mechanisms and various aspects of the interaction between bacteria and osteoblasts (e.g., best experimental conditions, bacteria-induced damages and immune system response), focusing on studies performed using the MG-63 osteoblastic cell line, the best traditional (2D) model for the study of this phenomenon to date. At the same time, as it has been widely demonstrated that 2D culture systems are not completely indicative of the dynamic environment in vivo, and more recent 3D models—representative of bone infection—have also been investigated.

Serratiopeptidase: Insights into the therapeutic applications

Therapeutic applications of enzymes have been widely accepted in clinical practices for decades. Proteolytic enzymes in particular, have been used for the treatment of diseases and disorders. Serratiopeptidase is a proteolytic enzyme having immense applications in therapeutic areas which have been validated by several in vitro, in vivo, and clinical studies as well as through anecdotal evidences. These applications are attributable to its versatile properties including anti-inflammatory, anti-biofilm, analgesic, anti-edemic, and fibrinolytic effects. The significant impact of serratiopeptidase reported needs to be backed by more scientific data. This review encompasses the details of therapeutic applications of serratiopeptidase based on available in vitro, in vivo, and clinical studies. We found some strong evidences regarding the efficacy of serratiopeptidase. However data on safety, tolerability, and its mechanism of action need detailing. This review aims to further explore the available literature on serratiopeptidase as well as provide scientific details for existing applications.

The Process of Osteoblastic Infection by Staphylococcus Aureus

Bone infection is difficult to cure, and relapse frequently occurs, which is a major treatment problem. One of the main reasons for the refractory and recurrent nature of bone infection is that bacteria, such as Staphylococcus aureus (S. aureus), can be internalized into osteoblasts after infecting bone tissue, thereby avoiding attack by the immune system and antibiotics. Understanding how bacteria (such as S. aureus) are internalized into osteoblasts is key to effective treatment. S. aureus is the most common pathogenic bacterium that causes bone infection. This paper reviews the literature, analyzes the specific process of osteoblastic S. aureus infection, and summarizes specific treatment strategies to improve bone infection treatment.

Virulence of MRSA USA300 is enhanced by sub-inhibitory concentration of two different classes of antibiotics

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) USA300 is responsible of many kinds of infections of skin and soft-tissue. Antibiotic resistance, biofilm formation and the ability to adhere and invade are virulence factors that contribute to MRSA pathogenesis. In some cases, decreased bioavailability of antibiotics in systemic circulation could result; in these conditions sub-therapeutic levels of the antibiotics may be established, exposing bacteria to sub-inhibitory concentrations. On the basis of several published scientific data it is fair to assume that all these events could induce an increase of bacterial virulence. In the present study, we investigated this process by measuring the effects of low doses of two different classes of antibiotics on some virulence features of MRSA USA300 isolate, like the ability to adhere and invade eukaryotic cells. Results obtained strongly support the importance of the respect of a correct dosage of antibiotic in therapy to escape the insurgence of more virulent phenotypes.

In vitro antimicrobial efficacy of laser exposed chlorpromazine against Gram-positive bacteria in planktonic and biofilm growth state

Aqueous chlorpromazine solutions exposed to 266 nm generated as fourth harmonic of Nd:YAG pulsed laser along time intervals from 1 min to 240 min were investigated for their antimicrobial activity against planktonic and adherent Gram-positive bacterial strains. Qualitative and quantitative assays based on microbiological methods and flow cytometry assays were performed to establish the minimum inhibitory and minimum biofilm eradication concentrations and to reveal some of the possible mechanisms of antimicrobial activity. Optimal irradiation conditions and combinations of photoproducts for achieving the best antimicrobial and antibiofilm effects are suggested. It was confirmed that chlorpromazine solutions irradiated for 15 min and 30 min have the best antimicrobial and antibiofilm activity against Staphylococcus aureus ATCC 6538, methicillin susceptible Staphylococcus aureus, methicillin resistant Staphylococcus aureus, Enterococcus faecium 17-VAR, Enterococcus faecalis 2921, and Bacillus subtilis 6633. Flow cytometry revealed that two of the possible mechanisms of the antimicrobial activity of irradiated chlorpromazine are the inhibition of efflux pumps activity and induction of cellular membrane lesions.

Serratiopeptidase reduces the invasion of osteoblasts by Staphylococcus aureus

Finding new strategies to counteract periprosthetic infection and implant failure is a main target in orthopedics. Staphylococcus aureus, the leading etiologic agent of orthopedic implant infections, is able to enter and kill osteoblasts, to stimulate pro-inflammatory chemokine secretion, to recruit osteoclasts, and to cause inflammatory osteolysis. Moreover, by entering eukaryotic cells, staphylococci hide from the host immune defenses and shelter from the extracellular antibiotics. Thus, infection persists, inflammation thrives, and a highly destructive osteomyelitis occurs around the implant. The ability of serratiopeptidase (SPEP), a metalloprotease by Serratia marcescens, to control S. aureus invasion of osteoblastic MG-63 cells and pro-inflammatory chemokine MCP-1 secretion was evaluated. Human osteoblast cells were infected with staphylococcal strains in the presence and in the absence of SPEP. Cell proliferation and cell viability were also evaluated. The release of pro-inflammatory chemokine MCP-1 was evaluated after the exposure of the osteoblast cells to staphylococcal strains. The significance of the differences in the results of each test and the relative control values was determined with Student's t-test. SPEP impairs their invasiveness into osteoblasts, without affecting the viability and proliferation of bone cells, and tones down their production of MCP-1. We recognize SPEP as a potential tool against S. aureus bone infection and destruction.

Chitosan nanoparticles as alternative anti-staphylococci agents: Bactericidal, antibiofilm and antiadhesive effects

Chitosan is a biocompatible, bioactive, non-toxic polymer that due to these characteristics has been widely used as a carrier for targeted delivery of bioactive molecules. In recent years, and considering that chitosan has a strong antimicrobial potential, the scientific community's focus has shifted onto the possible antimicrobial activity of chitosan nanoparticles. With this in mind, the aim of this work was to produce low molecular weight chitosan nanoparticles, through the ionic gelation method and characterize their potential biological activity against three staphylococci (MSSA, MRSA and MRSE) in planktonic and sessile environments. The chitosan nanoparticles produced had an average size of 244±12nm, an average charge of 17.3±1.4mV and had a MIC of 1.25mg/mL for all tested microorganisms. Bactericidal activity was only registered for MSSA and MRSA with the time-inhibition curves showing bactericidal activity within 1h. Assays regarding chitosan nanoparticles' impact upon sessile populations showed that they were effective in preventing MRSE adhesion and highly effective in reducing MRSA and MSSA biofilm formation.

Anti-biofilm activity of pseudoalteromonas haloplanktis tac125 against staphylococcus epidermidis biofilm: Evidence of a signal molecule involvement?

Staphylococcus epidermidis is recognized as cause of biofilm-associated infections and interest in the development of new approaches for S. epidermidis biofilm treatment has increased. In a previous paper we reported that the supernatant of Antarctic bacterium Pseudoalteromonas haloplanktis TAC125 presents an anti-biofilm activity against S. epidermidis and preliminary physico-chemical characterization of the supernatant suggested that this activity is due to a polysaccharide. In this work we further investigated the chemical nature of the anti-biofilm P. haloplanktis TAC125 molecule. The production of the molecule was evaluated in different conditions, and reported data demonstrated that it is produced in all P. haloplanktis TAC125 biofilm growth stages, also in minimal medium and at different temperatures. By using a surface coating assay, the surfactant nature of the anti-biofilm compound was excluded. Moreover, a purification procedure was set up and the analysis of an enriched fraction demonstrated that the anti-biofilm activity is not due to a polysaccharide molecule but that it is due to small hydrophobic molecules that likely work as signal. The enriched fraction was also used to evaluate the effect on S. epidermidis biofilm formation in dynamic condition by BioFlux system.

Anti-Biofilm Activity of a Long-Chain Fatty Aldehyde from Antarctic Pseudoalteromonas haloplanktis TAC125 against Staphylococcus epidermidis Biofilm

Staphylococcus epidermidis is a harmless human skin colonizer responsible for ~20% of orthopedic device-related infections due to its capability to form biofilm. Nowadays there is an interest in the development of anti-biofilm molecules. Marine bacteria represent a still underexploited source of biodiversity able to synthesize a broad range of bioactive compounds, including anti-biofilm molecules. Previous results have demonstrated that the culture supernatant of Antarctic marine bacterium Pseudoalteromonas haloplanktis TAC125 impairs the formation of S. epidermidis biofilm. Further, evidence supports the hydrophobic nature of the active molecule, which has been suggested to act as a signal molecule. In this paper we describe an efficient activity-guided purification protocol which allowed us to purify this anti-biofilm molecule and structurally characterize it by NMR and mass spectrometry analyses. Our results demonstrate that the anti-biofilm molecule is pentadecanal, a long-chain fatty aldehyde, whose anti-S. epidermidis biofilm activity has been assessed using both static and dynamic biofilm assays. The specificity of its action on S. epidermidis biofilm has been demonstrated by testing chemical analogs of pentadecanal differing either in the length of the aliphatic chain or in their functional group properties. Further, indications of the mode of action of pentadecanal have been collected by studying the bioluminescence of a Vibrio harveyi reporter strain for the detection of autoinducer AI-2 like activities. The data collected suggest that pentadecanal acts as an AI-2 signal. Moreover, the aldehyde metabolic role and synthesis in the Antarctic source strain has been investigated. To the best of our knowledge, this is the first report on the identification of an anti-biofilm molecule form from cold-adapted bacteria and on the action of a long-chain fatty aldehyde acting as an anti-biofilm molecule against S. epidermidis.

Minimum inhibitory concentration of vancomycin to methicillin resistant Staphylococcus aureus isolated from different clinical samples at a tertiary care hospital in Nepal

BACKGROUND

Methicillin resistant Staphylococcus aureus (MRSA) has evolved as a serious threat to public health. It has capability to cause infections not only in health care settings but also in community. Due to the multidrug resistance shown by MRSA, there are limited treatment options for the infections caused by this superbug. Vancomycin is used as the drug of choice for the treatment of infections caused by MRSA. Different studies from all around the world have documented the emergence of strains of S. aureus those are intermediate sensitive or resistant to vancomycin. And recently, there have been reports of reduced susceptibility of MRSA to vancomycin, from Nepal also. So the main purpose of this study was to determine the minimum inhibitory concentration (MIC) of vancomycin to methicillin resistant S. aureus isolated from different clinical specimens.

METHODS

Total 125 strains of S. aureus isolated from different clinical samples at KIST Medical College and Teaching Hospital, Lalitpur, Nepal from Nov 2012 to June 2013, were subjected to MRSA detection by cefoxitin disc diffusion method. The minimum inhibitory concentrations of vancomycin to confirmed MRSA strains were determined by agar dilution method. Yellow colored colonies in mannitol salt agar, which were gram positive cocci, catalase positive and coagulase positive were confirmed to be S. aureus.

RESULTS

Among, total 125 S. aureus strains isolated; 47(37.6%) were MRSA. Minimum inhibitory concentrations of vancomycin to the strains of MRSA ranged from 0.125 μg/ml to 1 μg/ml.

CONCLUSION

From our findings we concluded that the rate of isolation of MRSA among all the strains of S. aureus isolated from clinical samples was very high. However, none of the MRSA strains were found to be vancomycin intermediate-sensitive or vancomycin-resistant.

Large-scale biofilm cultivation of Antarctic bacterium Pseudoalteromonas haloplanktis TAC125 for physiologic studies and drug discovery

Microbial biofilms are mainly studied due to detrimental effects on human health but they are also well established in industrial biotechnology for the production of chemicals. Moreover, biofilm can be considered as a source of novel drugs since the conditions prevailing within biofilm can allow the production of specific metabolites. Antarctic bacterium Pseudoalteromonas haloplanktis TAC125 when grown in biofilm condition produces an anti-biofilm molecule able to inhibit the biofilm of the opportunistic pathogen Staphylococcus epidermidis. In this paper we set up a P. haloplanktis TAC125 biofilm cultivation methodology in automatic bioreactor. The biofilm cultivation was designated to obtain two goals: (1) the scale up of cell-free supernatant production in an amount necessary for the anti-biofilm molecule/s purification; (2) the recovery of P. haloplanktis TAC125 cells grown in biofilm for physiological studies. We set up a fluidized-bed reactor fermentation in which floating polystyrene supports were homogeneously mixed, exposing an optimal air-liquid interface to let bacterium biofilm formation. The proposed methodology allowed a large-scale production of anti-biofilm molecule and paved the way to study differences between P. haloplanktis TAC125 cells grown in biofilm and in planktonic conditions. In particular, the modifications occurring in the lipopolysaccharide of cells grown in biofilm were investigated.

Evaluation of contact lens multipurpose solutions on bacterial biofilm development

OBJECTIVES

No sooner are contact lenses (CLs) inserted into the eyes than lipids, proteins, and glycoproteins rapidly accumulate on their surface, thus favoring the adhesion of commensal bacteria and biofilm formation. Infections may be caused by the proliferation of indigenous flora or other opportunistic pathogens. Our purpose was to evaluate the activity and the capacity of different CL solutions to interfere with the mechanisms of biofilm formation and stability and use of a system to study dynamically biofilm development.

METHODS

We evaluated the antibiofilm activity of three different multipurpose solutions (MPSs): Regard, Biotrue, and OPTI-FREE PureMoist on four bacterial species (Serratia marcescens, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Staphylococcus aureus). Static biofilm assay was first performed to analyze the effect of MPSs. Dynamic assays were performed with the BioFlux system to analyze the effect of the OxyChlorite solution Regard on the biofilm formation.

RESULTS

Our studies show that MPSs are able to completely inhibit biofilm formation of Staphylococcus species and of S. marcescens after only 4 hr of incubation. Moreover, a reduction of biofilm formation by Pseudomonas was noted. Best results on P. aeruginosa were obtained with Regard. Regard was also used for dynamic assay, revealing its ability to disaggregate the mature biofilm. Regard completely inhibited biofilm formation by S. epidermidis and slowed down biofilm development by P. aeruginosa.

CONCLUSIONS

Our findings indicate that the CL solutions tested were all able to reduce biofilm formation. Furthermore, the BioFlux system was proven to be useful for the evaluation of the effectiveness of CL solutions against microbial biofilm formation.

Anti-Biofilm Activities from Marine Cold Adapted Bacteria Against Staphylococci and Pseudomonas aeruginosa

Microbial biofilms have great negative impacts on the world’s economy and pose serious problems to industry, public health and medicine. The interest in the development of new approaches for the prevention and treatment of bacterial adhesion and biofilm formation has increased. Since, bacterial pathogens living in biofilm induce persistent chronic infections due to the resistance to antibiotics and host immune system. A viable approach should target adhesive properties without affecting bacterial vitality in order to avoid the appearance of resistant mutants. Many bacteria secrete anti-biofilm molecules that function in regulating biofilm architecture or mediating the release of cells from it during the dispersal stage of biofilm life cycle. Cold-adapted marine bacteria represent an untapped reservoir of biodiversity able to synthesize a broad range of bioactive compounds, including anti-biofilm molecules. The anti-biofilm activity of cell-free supernatants derived from sessile and planktonic cultures of cold-adapted bacteria belonging to Pseudoalteromonas, Psychrobacter, and Psychromonas species were tested against Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa strains. Reported results demonstrate that we have selected supernatants, from cold-adapted marine bacteria, containing non-biocidal agents able to destabilize biofilm matrix of all tested pathogens without killing cells. A preliminary physico-chemical characterization of supernatants was also performed, and these analyses highlighted the presence of molecules of different nature that act by inhibiting biofilm formation. Some of them are also able to impair the initial attachment of the bacterial cells to the surface, thus likely containing molecules acting as anti-biofilm surfactant molecules. The described ability of cold-adapted bacteria to produce effective anti-biofilm molecules paves the way to further characterization of the most promising molecules and to test their use in combination with conventional antibiotics.

Serratiopeptidase: a well-known metalloprotease with a new non-proteolytic activity against S. aureus biofilm

Background

The use of indwelling medical devices is associated with a significant risk of infections by Staphylococcus aureus (S. aureus) which possesses a variety of virulence factors including many toxins and the ability to invade eukaryotic cells or to form biofilm on biotic and abiotic surfaces. The virulence factors above described are often related to proteins exposed on the bacterial surface. Blocking S. aureus colonization may reduce the incidence of invasive infectious diseases.

Previously reports evaluated the anti-infective properties of serratiopeptidase (Spep), an extracellular metalloprotease produced by Serratia marcescens ATCC 21074 (E-15), in impairing virulence-related staphylococcal properties, such as attachment to inert surfaces and adhesion/invasion on eukaryotic cells. However, to date its mechanism of action is unknown.

Methods

Spep gene was PCR amplified and cloned into expression vector pET28b(+). The mutant EspepA was constructed from plasmid pET28b-Spep applying the one-step overlap extension PCR strategy. There sulting plasmids were costransformed in EcBL21(DE3) cells with the plasmid pRuW4inh1 harboring the Erwinia chrysanthemi secretion system.

Bacterial pellets and supernatants were collected and analyzed by SDS-PAGE and zymography. The unambiguous identification and a detailed structure characterization of both the wild type and the mutant Spep were obtained by mass spectrometric analyses.

The resultant supernatants sterilized by filtration were separately used to condition biofilm formation of S. aureus. Quantification was based on crystal violet method.

Results

In this work we constructed Spep mutant by substituting the glutamic acid in the catalytic site with a residue of alanine. In this manner we were able to evaluate the anti-biofilm activity of Spep mutant in absence of proteolytic activity. As expected, this mutant did not display protease activity but it retained its anti-biofilm properties, suggesting that this action is independent by enzymatic activity.

Conclusions

New knowledge obtained from data reported in this paper calls attention to a novel mechanism of action of Spep. This protein could be developed as a potential “antipathogenic agent” capable to impair the ability of S. aureus to form biofilm on prostheses, catheters and medical devices, exploiting a mechanism different from the proteolytic activity.

Adhesive behaviour and virulence of coagulase negative staphylococci isolated from Italian cheeses

Coagulase-negative staphylococci (CoNS) belong to saprophytic microbiota on the skin and mucous membranes of warm-blooded animals and humans, but are also isolated from foodstuffs such as meat, cheese, and milk. In other circumstances, some CoNS can act as pathogens. Thus the presence of CoNS may not be an immediate danger to public health, but can become a risk factor. In particular antibiotic-resistant genes could be transferred to other potentially pathogenic microorganisms. Furthermore, CoNS are known to be strong biofilm producers and this is also a risk factor for public health. The aim of the present work was to determine the genotypic and phenotypic profiles of 106 CoNS belonging to four different species isolated from five different Italian cheeses for the presence of some adhesion and virulence features. In order to verify a possible correlation between the formation of biofilm and staphylococcal virulence factors, we checked the presence of adhesin genes by PCR and we investigated the ability of these strains to make biofilm at different temperatures. Furthermore, in some conditions, we analyzed surface proteins and autolytic pattern of selected strains. In conclusion, we checked the presence of norA and mecA genes responsible for fluoroquinolones and methicillin resistance, respectively. We found resistant genes in a proportion of the food isolates in amounts of 9.4% (mecA) and 5.7% (norA). These data support the importance to continuously examine the microbiota not only for the creation of a database but also to safeguard public health.

Curcumin rescues Caenorhabditis elegans from a Burkholderia pseudomallei infection

The tropical pathogen Burkholderia pseudomallei requires long-term parenteral antimicrobial treatment to eradicate the pathogen from an infected patient. However, the development of antibiotic resistance is emerging as a threat to this form of treatment. To meet the need for alternative therapeutics, we proposed a screen of natural products for compounds that do not kill the pathogen, but in turn, abrogate bacterial virulence. We suggest that the use of molecules or compounds that are non-bactericidal (bacteriostatic) will reduce or abolish the development of resistance by the pathogen. In this study, we adopted the established Caenorhabditis elegans-B. pseudomallei infection model to screen a collection of natural products for any that are able to extend the survival of B. pseudomallei infected worms. Of the 42 natural products screened, only curcumin significantly improved worm survival following infection whilst not affecting bacterial growth. This suggested that curcumin promoted B. pseudomallei-infected worm survival independent of pathogen killing. To validate that the protective effect of curcumin was directed toward the pathogen, bacteria were treated with curcumin prior to infection. Worms fed with curcumin-treated bacteria survived with a significantly extended mean-time-to-death (p < 0.0001) compared to the untreated control. In in vitro assays, curcumin reduced the activity of known virulence factors (lipase and protease) and biofilm formation. To determine if other bacterial genes were also regulated in the presence of curcumin, a genome-wide transcriptome analysis was performed on curcumin-treated pathogen. A number of genes involved in iron acquisition and transport as well as genes encoding hypothetical proteins were induced in the presence of curcumin. Thus, we propose that curcumin may attenuate B. pseudomallei by modulating the expression of a number of bacterial proteins including lipase and protease as well as biofilm formation whilst concomitantly regulating iron transport and other proteins of unknown function.

A C-type lectin from Bothrops jararacussu venom disrupts Staphylococcal biofilms

Bovine mastitis is a major threat to animal health and the dairy industry. Staphylococcus aureus is a contagious pathogen that is usually associated with persistent intramammary infections, and biofilm formation is a relevant aspect of the outcome of these infections. Several biological activities have been described for snake venoms, which led us to screen secretions of Bothrops jararacussu for antibiofilm activity against S. aureus NRS155. Crude venom was fractionated by size-exclusion chromatography, and the fractions were tested against S. aureus. Biofilm growth, but not bacterial growth, was affected by several fractions. Two fractions (15 and 16) showed the best activities and were also assayed against S. epidermidis NRS101. Fraction 15 was identified by TripleTOF mass spectrometry as a galactose-binding C-type lectin with a molecular weight of 15 kDa. The lectin was purified from the crude venom by D-galactose affinity chromatography, and only one peak was observed. This pure lectin was able to inhibit 75% and 80% of S. aureus and S. epidermidis biofilms, respectively, without affecting bacterial cell viability. The lectin also exhibited a dose-dependent inhibitory effect on both bacterial biofilms. The antibiofilm activity was confirmed using scanning electron microscopy. A pre-formed S. epidermidis biofilm was significantly disrupted by the C-type lectin in a time-dependent manner. Additionally, the lectin demonstrated the ability to inhibit biofilm formation by several mastitis pathogens, including different field strains of S. aureus, S. hyicus, S. chromogenes, Streptococcus agalactiae, and Escherichia coli. These findings reveal a new activity for C-type lectins. Studies are underway to evaluate the biological activity of these lectins in a mouse mastitis model.

Biofilms as a mechanism of bacterial resistance

Inside the biofilm, antimicrobial agents must overcome high cell density, an increased number of resistant mutants, substance delivery, molecular exchanges, such as high levels of beta-lactamases or inducers of efflux pump expression, and specific adaptive cells, so-called persisters. The environment within the biofilm modulates the response to antibiotics, especially when the SOS response or DNA repair systems are involved. Exposure to subinhibitory concentrations of antibiotics can enhance biofilm formation and mutagenesis. Thus, a global response to cell stress seems to be responsible for antibiotic-induced biofilm formation.

Temporal expression of agrB, cidA, and alsS in the early development of Staphylococcus aureus UAMS-1 biofilm formation and the structural role of extracellular DNA and carbohydrates

Extracellular DNA (eDNA) is an important component of the extracellular polymeric substance matrix and is important in the establishment and persistence of Staphylococcus aureus UAMS-1 biofilms. The aim of the study was to determine the temporal expression of genes involved in early biofilm formation and eDNA production. We used qPCR to investigate expression of agrB, which is associated with secreted virulence factors and biofilm dispersal, cidA, which is associated with biofilm adherence and genomic DNA release, and alsS, which is associated with cell lysis, eDNA release and acid tolerance. The contribution of eDNA to the stability of the biofilm matrix was assessed by digesting with DNase I (Pulmozyme) and quantifying structure by confocal microscopy and comstat image analysis. AgrB expression initially increased at 24 h but then dramatically decreased at 72 h in an inverse relationship to biomass, supporting its role in regulating biofilm dispersal. cidA and alsS expression steadily increased over 72 h, suggesting that eDNA was an important component of early biofilm development. DNase I had no effect on biomass, but did cause the biofilms to become more heterogeneous. Carbohydrates in the matrix appeared to play an important role in structural stability.

Responses of Staphylococcus aureus bacterial cells to nanocrystalline nickel nanostructures

A broad range of human diseases are associated with bacterial infections, often initiated by specific adhesion of a bacterium to the target environment. Despite the significant role of bacterial adhesion in human infectious diseases, details and mechanisms of bacterial adhesion have remained elusive. Herein, we study the physical interactions between Staphylococcus aureus, a type of micro-organism relevant to infections associated with medical implants, and nanocrystalline (nc) nickel nanostructures with various columnar features, including solid core, hollow, x-shaped and c-shaped pillars. Scanning electron microscopy results show the tendency of these bacterial cells to attach to the nickel nanostructures. Moreover, unique single bacterium attachment characteristics were observed on nickel nanostructures with dimensions comparable to the size of a single bacterium.