Integrated proteomic and metabolomic analysis reveals that rhodomyrtone reduces the capsule in Streptococcus pneumoniae

A Novel Antibiotic, Rhodomyrtone: Pharmacokinetic Studies in a Murine Model and Optimization and Validation of High-Performance Liquid Chromatographic Method for Plasma Analysis

Rhodomyrtone has indisputable and undeniable potential as a new antibiotic for antibiotic-resistant Gram-positive bacteria. Therefore, the main objective of this study was to determine the pharmacokinetics profiles of orally administered rhodomyrtone in rats. A reverse-phase HPLC-UV method was developed, optimized and validated for the analysis of rhodomyrtone concentrations in rat plasma. The retention time of papaverine and rhodomyrtone was 3.928 and 5.937 min, with no interference with the excipients used. The lower limit of quantification (LLOQ) of rhodomyrtone in the plasma sample was 0.04 μg/mL, the accuracy of rhodomyrtone at the LLOQ level ranged from 93.64 to 106.36%, precision was 6.59%, 80-120% for accuracy and <20% CV for precision. The calibration curve was linear at concentrations ranging from 0.04 to 128 µg/mL with a correlation coefficient (r) value of equal to or greater than 0.999. Sprague Dawley rats received a single dose of rhodomyrtone at 50 and 100 mg/kg. Blood samples were collected from tail veins. The peak plasma concentration was observed at 2 h, and the area under the curve of rhodomyrtone at 50 mg/kg and 100 mg/kg was 3.41 ± 1.04 and 7.82 ± 1.53 μg·h/mL, respectively. The results demonstrated linear pharmacokinetics characteristics at the studied dosage range. The plasma concentration of rhodomyrtone was above the minimal inhibition concentrations of several common pathogenic bacteria of medical importance. The proposed HPLC-UV method is fast, cost-effective, reliable and reproducible, and it is proposed for the routine analysis of rhodomyrtone.

Piper betle extract and its application in bovine teat dipping solution inhibit and eliminate biofilms in bovine mastitis-inducing staphylococci

Background and Aim

Staphylococci, including Staphylococcus aureus, Staphylococcus chromogenes, and Staphylococcus haemolyticus, are significant bacteria that induce bovine mastitis, primarily because they can form biofilms in bovine teat canals. This study aimed to investigate the efficacy of Piper betle extract and a bovine teat dipping solution containing P. betle extract (BSP) against these mastitis-causing staphylococci.

Materials and Methods

BSP was prepared using P. betle extract as the bioactive compound. The antibacterial activity of the plant extract and BSP against the pathogens was investigated using a broth microdilution method. The activity of the extract and BSP against the pathogen biofilms was also determined. A stability test was performed to observe the pH, color, turbidity, homogeneity, precipitation, and separation of BSP stored at 4°C and 25°C for up to 4 weeks.

Results

The extract exhibited potent antibacterial activity against S. aureus and S. haemolyticus, with similar values for minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) ranging from 0.03 mg/mL to 0.125 mg/mL. The MIC and MBC values of the extract against S. chromogenes were 0.5-1 mg/mL and 0.5-2 mg/mL, respectively. Moreover, BSP exhibited MIC and MBC values of 12.5-50 v/v against all tested staphylococci isolates. When used at 1/2 and 1/4 × MIC, the extract and BSP significantly inhibited the formation of staphylococcal biofilms (p < 0.05) in the tested strains. The results indicated that treatment with 1/2 × MIC of the extract and BSP resulted in biofilm inhibition ranging from 30%-66% and 19%-39%, respectively. Furthermore, the extract at 16 × MIC eliminated 54%-86% of established mature isolate biofilms, whereas BSP removed 41%-61% of mature biofilm viability. Storage of BSP at 4°C did not change the factors associated with stability from the 1st to 4th week.

Conclusion

These findings suggest that BSP may exhibit potential medicinal benefits in inhibiting the growth and biofilm formation of mastitis-inducing staphylococci in bovines.

Virulence factors and quorum sensing as targets of new therapeutic options by plant-derived compounds against bacterial infections caused by human and animal pathogens

The emergence of antibiotic-resistant bacteria and hospital-acquired bacterial infection has become rampant due to antibiotic overuse. Virulence factors are secondary to bacterial growth and are important in their pathogenesis, and therefore, new antimicrobial therapies to inhibit bacterial virulence factors are becoming important strategies against antibiotic resistance. Here, we focus on anti-virulence factors that act through anti-quorum sensing and the subsequent clearance of bacteria by antimicrobial compounds, especially active herbal extracts. These quorum sensing systems are based on toxins, biofilms, and efflux pumps, and bioactive compounds isolated from medicinal plants can treat bacterial virulence pathologies. Ideally, bacterial virulence factors are secondary growth factors of bacteria. Hence, inhibition of bacterial virulence factors could reduce bacterial pathogenesis. Furthermore, anti-virulence factors from herbal compounds can be developed as novel treatments for bacterial infection. Therefore, this narrative review aims to discuss bacterial virulence factors acting through quorum sensing systems that are preserved as targets for treating bacterial infection by plant-derived compounds.

Transcriptomic and Metabolomic Profiling Reveals That KguR Broadly Impacts the Physiology of Uropathogenic Escherichia coli Under in vivo Relevant Conditions

Urinary tract infections are primarily caused by uropathogenic Escherichia coli (UPEC). In contrast to the intestinal E. coli strains that reside in nutrient-rich gut environment, UPEC encounter distinct niches, for instance human urine, which is an oxygen- and nutrient-limited environment. Alpha-ketoglutarate (KG) is an abundant metabolite in renal proximal tubule cells; and previously we showed that two-component signaling system (TCS) KguS/KguR contributes to UPEC colonization of murine urinary tract by promoting the utilization of KG as a carbon source under anaerobic conditions. However, knowledge about the KguR regulon and its impact on UPEC fitness is lacking. In this work, we analyzed transcriptomic and metabolomic changes caused by kguR deletion under anaerobiosis when KG is present. Our results indicated that 620 genes were differentially expressed in the ΔkguR mutant, as compared to the wild type; of these genes, 513 genes were downregulated and 107 genes were upregulated. Genes with substantial changes in expression involve KG utilization, acid resistance, iron uptake, amino acid metabolism, capsule biosynthesis, sulfur metabolism, among others. In line with the transcriptomics data, several amino acids (glutamate, lysine, etc.) and uridine 5′-diphosphogalactose (involved in capsule biosynthesis) were significantly less abundant in the ΔkguR mutant. We then confirmed that the ΔkguR mutant, indeed, was more sensitive to acid stress than the wild type, presumably due to downregulation of genes belonging to the glutamate-dependent acid resistance system. Furthermore, using gene expression and electrophoretic mobility shift assays (EMSAs), we demonstrate that KguR autoregulates its own expression by binding to the kguSR promoter region. Lastly, we performed a genome-wide search of KguR binding sites, and this search yielded an output of at least 22 potential binding sites. Taken together, our data establish that in the presence of KG, KguR broadly impacts the physiology of UPEC under anaerobiosis. These findings greatly further our understanding of KguS/KguR system as well as UPEC pathobiology.

Extracellular Vesicles from Different Pneumococcal Serotypes Are Internalized by Macrophages and Induce Host Immune Responses

Bacterial extracellular vesicles are membranous ultrastructures released from the cell surface. They play important roles in the interaction between the host and the bacteria. In this work, we show how extracellular vesicles produced by four different serotypes of the important human pathogen, Streptococcus pneumoniae, are internalized by murine J774A.1 macrophages via fusion with the membrane of the host cells. We also evaluated the capacity of pneumococcal extracellular vesicles to elicit an immune response by macrophages. Macrophages treated with the vesicles underwent a serotype-dependent transient loss of viability, which was further reverted. The vesicles induced the production of proinflammatory cytokines, which was higher for serotype 1 and serotype 8-derived vesicles. These results demonstrate the biological activity of extracellular vesicles of clinically important pneumococcal serotypes.

Approaching In Vivo Models of Pneumococcus-Host Interaction: Insights into Surface Proteins, Capsule Production, and Extracellular Vesicles

Infections caused by the Gram-positive bacterium Streptococcus pneumoniae have become a major health problem worldwide because of their high morbidity and mortality rates, especially in developing countries. This microorganism colonizes the human upper respiratory tract and becomes pathogenic under certain circumstances, which are not well known. In the interaction with the host, bacterial surface structures and proteins play major roles. To gain knowledge into gradual changes and adaptive mechanisms that this pathogen undergoes from when it enters the host, we mimicked several in vivo situations representing interaction with epithelial and macrophage cells, as well as a condition of presence in blood. Then, we analyzed, in four pneumococcal strains, two major surface structures, the capsule and extracellular vesicles produced by the pneumococci, as well as surface proteins by proteomics, using the “shaving” approach, followed by LC-MS/MS. We found important differences in both surface ultrastructures and proteins among the culture conditions and strains used. Thus, this work provides insights into physiological adaptations of the pneumococcus when it interacts with the host, which may be useful for the design of strategies to combat infections caused by this pathogen.

Rhodomyrtone Accumulates in Bacterial Cell Wall and Cell Membrane and Inhibits the Synthesis of Multiple Cellular Macromolecules in Epidemic Methicillin-Resistant Staphylococcus aureus

As the burden of antibacterial resistance worsens and treatment options become narrower, rhodomyrtone—a novel natural antibiotic agent with a new antibacterial mechanism—could replace existing antibiotics for the treatment of infections caused by multi-drug resistant Gram-positive bacteria. In this study, rhodomyrtone was detected within the cell by means of an easy an inexpensive method. The antibacterial effects of rhodomyrtone were investigated on epidemic methicillin-resistant Staphylococcus aureus. Thin-layer chromatography demonstrated the entrapment and accumulation of rhodomyrtone within the bacterial cell wall and cell membrane. The incorporation of radiolabelled precursors revealed that rhodomyrtone inhibited the synthesis of macromolecules including DNA, RNA, proteins, the cell wall, and lipids. Following the treatment with rhodomyrtone at MIC (0.5–1 µg/mL), the synthesis of all macromolecules was significantly inhibited (p ≤ 0.05) after 4 h. Inhibition of macromolecule synthesis was demonstrated after 30 min at a higher concentration of rhodomyrtone (4× MIC), comparable to standard inhibitor compounds. In contrast, rhodomyrtone did not affect lipase activity in staphylococci—both epidemic methicillin-resistant S. aureus and S. aureus ATCC 29213. Interfering with the synthesis of multiple macromolecules is thought to be one of the antibacterial mechanisms of rhodomyrtone.

Bacterial biofilm-derived antigens: a new strategy for vaccine development against infectious diseases

INTRODUCTION

Microorganisms can develop into a social organization known as biofilms and these communities can be found in virtually all types of environment on earth. In biofilms, cells grow as multicellular communities held together by a self-produced extracellular matrix. Living within a biofilm allows for the emergence of specific properties for these cells that their planktonic counterparts do not have. Furthermore, biofilms are the cause of several infectious diseases and are frequently inhabited by multi-species. These interactions between microbial species are often critical for the biofilm process. Despite the importance of biofilms in disease, vaccine antigens are typically prepared from bacteria grown as planktonic cells under laboratory conditions. Vaccines based on planktonic bacteria may not provide optimal protection against biofilm-driven infections.

AREAS COVERED

In this review, we will present an overview of biofilm formation, what controls this mode of growth, and recent vaccine development targeting biofilms.

EXPERT OPINION

Previous and ongoing research provides evidence that vaccine formulation with antigens derived from biofilms is a promising approach to prevent infectious diseases and can enhance the protective efficacy of existing vaccines. Therefore, research focusing on the identification of biofilm-derived antigens merits further investigations.

Rhodomyrtone as a New Natural Antibiotic Isolated from Rhodomyrtus tomentosa Leaf Extract: A Clinical Application in the Management of Acne Vulgaris

Rhodomyrtone, a plant-derived principal compound isolated from Rhodomyrtus tomentosa (Myrtaceae) leaf extract, was assessed as a potential natural alternative for the treatment of acne vulgaris. The clinical efficacy of a 1% liposomal encapsulated rhodomyrtone serum was compared with a marketed 1% clindamycin gel. In a randomized and double-blind controlled clinical trial, 60 volunteers with mild to moderate acne severity were assigned to two groups: rhodomyrtone serum and clindamycin gel. The volunteers were instructed to apply the samples to acne lesions on their faces twice daily. A significant reduction in the total numbers of acne lesions was demonstrated in both treatment groups between week 2 and 8 (p < 0.05). Significant differences in acne numbers compared with the baseline were evidenced at week 2 onwards (p < 0.05). At the end of the clinical trial, the total inflamed acne counts in the 1% rhodomyrtone serum group were significantly reduced by 36.36%, comparable to 34.70% in the clindamycin-treated group (p < 0.05). Furthermore, a commercial prototype was developed, and a clinical assessment of 45 volunteers was performed. After application of the commercial prototype for 1 week, 68.89% and 28.89% of volunteers demonstrated complete and improved inflammatory acne, respectively. All of the subjects presented no signs of irritation or side effects during the treatment. Most of the volunteers (71.11%) indicated that they were very satisfied. Rhodomyrtone serum was demonstrated to be effective and safe for the treatment of inflammatory acne lesions.

Rhodomyrtus tomentosa Leaf Extract and Rhodomyrtone Combat Streptococcus pneumoniae Biofilm and Inhibit Invasiveness to Human Lung Epithelial and Enhance Pneumococcal Phagocytosis by Macrophage

Rhodomyrtus tomentosa leaf has been traditionally used to treat many infections. This plant species has been documented to possess a wide spectrum of pharmacological effects. This study aimed to determine the effects of Rhodomyrtus tomentosa leaf extract and its potent purified compound, rhodomyrtone, on Streptococcus pneumoniae virulence factors including biofilms, capsule formation, and invasiveness which play important roles in infections. Ethanol leaf extract and rhodomyrtone demonstrated excellent antibacterial activity against S. pneumoniae with minimal inhibitory concentration (MIC) ranging from 16-32 µg/ml and 0.125-1 µg/ml, respectively. The ability of the extract and rhodomyrtone to prevent biofilm formation and eradicate mature biofilms was assessed. The extract and rhodomyrtone at 1/8 × MIC significantly inhibited biofilm formation in all clinical isolates (P < 0.05). The viability of 8-day biofilm-grown cells significantly decreased following the treatment with the extract and rhodomyrtone at 16 × MIC. 40-90% reduction in the bacterial adhesion and invasion to A549 human alveolar epithelial cells was observed after challenging with the extract and rhodomyrtone, compared with the control within 60 min. Increase in 90-99% phagocytosis of the bacterial cells by RAW264.7 macrophage cell line was detected following the treatment with the extract and rhodomyrtone at 1/2 × MIC, compared with the control. The results suggested potential medicinal benefits of the extract and rhodomyrtone for the treatment of pneumococcal infections.

In vivo safety assessment of rhodomyrtone, a potent compound, from Rhodomyrtus tomentosa leaf extract

BACKGROUND

Rhodomyrtus tomentosa (Aiton) Hassk. has been traditionally used to relieve various diseases. Rhodomyrtone, a bioactive acylphloroglucinol compound isolated from the leaves of Rhodomyrtus tomentosa, has been scientifically evidenced as a potential antibacterial agent. This study aimed to assess safety of rhodomyrtone in both invertebrate and vertebrate models.

MATERIAL AND METHODS

Safety of rhodomyrtone was determined in an invertebrate model, Galleria mellonella as well as vertebrate models including zebrafish (Danio rerio) and murine. In addition, toxicity to human erythrocytes was also measured.

RESULTS

Treatment of Galleria mellonella with rhodomyrtone at 100 mg/kg body weight up to four days showed no visible toxic effects (100 % survival). In zebrafish embryo model, at least 80 % survival of embryos was demonstrated when treated with rhodomyrtone at 0.5 μg/mL for three days. Prior to clinical trial, it is a prerequisite that rhodomyrtone has to be evaluated for its biocompatibility with human blood components. The results displayed that rhodomyrtone at 256 μg/mL did not cause any observable human erythrocyte haemolysis. Furthermore, preclinical assessment of rhodomyrtone formulation justified potential applications of rhodomyrtone in humans. Oral toxicity testing in a mouse model indicated the absence of systemic toxicity when the animals received up to 5000 mg/kg body weight of rhodomyrtone formulation for a period of fourteen days.

CONCLUSIONS

As the minimal inhibitory concentration of rhodomyrtone against most Gram-positive pathogens is 0.5-1 μg/mL, the results suggest that it should produce no toxic effects at concentrations used in human, thus support further development in pharmaceutical industries and public health applications.

Antibacterial mechanism of rhodomyrtone involves the disruption of nucleoid segregation checkpoint in Streptococcus suis

Rhodomyrtone has been recently demonstrated to possess a novel antibiotic mechanism of action against Gram-positive bacteria which involved the multiple targets, resulting in the interference of several bacterial biological processes including the cell division. The present study aims to closely look at the downstream effect of rhodomyrtone treatment on nucleoid segregation in Streptococcus suis, an important zoonotic pathogen. The minimum inhibition concentration (MIC) and the minimum bactericidal concentration (MBC) values of rhodomyrtone against the recombinant S. suis ParB-GFP, a nucleoid segregation reporter strain, were 0.5 and 1 µg/ml, respectively, which were equivalent to the potency of vancomycin. Using the fluorescence live-cell imaging, we demonstrated that rhodomyrtone at 2× MIC caused incomplete nucleoid segregation and septum misplacement, leading to the generation of anucleated cells. FtsZ immune-staining of rhodomyrtone-treated S. suis for 30 min revealed that the large amount of FtsZ was trapped in the region of high fluidity membrane and appeared to be able to polymerize to form a complete Z-ring. However, the Z-ring was shifted away from the midcell. Transmission electron microscopy further confirmed the disruption of nucleoid segregation and septum misplacement at 120 min following the rhodomyrtone treatment. Asymmetric septum formation resulted in either generation of minicells without nucleoid, septum formed over incomplete segregated nucleoid (guillotine effect), or formation of multi-constriction of Z-ring within a single cell. This finding spotlights on antibacterial mechanism of rhodomyrtone involves the early stage in bacterial cell division process.

Antibiotic Discovery: Where Have We Come from, Where Do We Go?

Given the increase in antibiotic-resistant bacteria, alongside the alarmingly low rate of newly approved antibiotics for clinical usage, we are on the verge of not having effective treatments for many common infectious diseases. Historically, antibiotic discovery has been crucial in outpacing resistance and success is closely related to systematic procedures—platforms—that have catalyzed the antibiotic golden age, namely the Waksman platform, followed by the platforms of semi-synthesis and fully synthetic antibiotics. Said platforms resulted in the major antibiotic classes: aminoglycosides, amphenicols, ansamycins, beta-lactams, lipopeptides, diaminopyrimidines, fosfomycins, imidazoles, macrolides, oxazolidinones, streptogramins, polymyxins, sulphonamides, glycopeptides, quinolones and tetracyclines. During the genomics era came the target-based platform, mostly considered a failure due to limitations in translating drugs to the clinic. Therefore, cell-based platforms were re-instituted, and are still of the utmost importance in the fight against infectious diseases. Although the antibiotic pipeline is still lackluster, especially of new classes and novel mechanisms of action, in the post-genomic era, there is an increasingly large set of information available on microbial metabolism. The translation of such knowledge into novel platforms will hopefully result in the discovery of new and better therapeutics, which can sway the war on infectious diseases back in our favor.

Antioxidant Properties and Antibacterial Effects of Eucalyptus camaldulensis Ethanolic Leaf Extract on Biofilm Formation, Motility, Hemolysin Production, and Cell Membrane of the Foodborne Pathogen Listeria monocytogenes

Consumer concerns toward chemical preservatives have resulted in increased search for healthy green alternative. In this study, the antioxidant activity and antibacterial effects of Eucalyptus camaldulensis ethanolic leaf extract against Listeria monocytogenes, a serious foodborne pathogen, was evaluated. Total phenolic and flavonoid contents of the extract were 11.10 mg garlic acid equivalent/mg extract and 15.05 mg quercetin equivalent/mg extract, respectively. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration of the extract was 64-128 μg/mL and 256-512 μg/mL, respectively. Time-kill assay revealed growth inhibitory effects after 4-h treatment of the bacteria with the extract. A reduction of ≈2-3 log colony-forming units per milliliter was observed against the tested food and environmental isolates after challenging the pathogens with the extract at MIC for 6 h. Sub-MICs of the extract significantly inhibited motility and listeriolysin O production up to 80%, with 60% inhibition of biofilm formation (p < 0.05). Antioxidant assay revealed free radical scavenging activity with 50% inhibitory concentration (IC₅₀) of 57.07 μg/mL for 2,2-diphenyl-1-picrylhydrazyl and 29.01 μg/mL for ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] assay. Ferric reducing antioxidant power assay further showed a total antioxidant power equivalent to 92.93 μM ascorbic acid equivalent/mg extract. As the extract exhibited profound antilisterial activity and good radical scavenging ability, it might serve as a potential alternative source of biopreservative agent against L. monocytogenes.

Rhodomyrtone decreases Staphylococcus aureus SigB activity during exponentially growing phase and inhibits haemolytic activity within membrane vesicles

Sigma factor B (SigB) controls the expression of Staphylococcus aureus genes including virulence factors and plays a role in the bacterial secretion system through membrane vesicle production. Inhibition of SigB could attenuate SigB dependent virulence and secretion system. The objective of this study was to determine the effects of rhodomyrtone on SigB and virulence factors related to SigB. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values of rhodomyrtone against 67 clinical methicillin-resistant S. aureus isolates were 0.25-8 μg/ml, which were similar to those of vancomycin. Using luciferase gene fused to SigB dependent promoters of asp23, five time reduction in SigB activity was observed when the bacteria were treated with rhodomyrtone for 3 h. Rhodomyrtone significantly reduced SigB activity in a concentration dependent manner in exponentially growing cells (P < 0.05). In addition, sigB mutant was more sensitive towards increasing concentrations of rhodomyrtone than the wild type and yabJ-spoVG mutant. Rhodomyrtone at 0.625 μg/ml reduced the growth of sigB mutant by approximately 99%, compared with the yabJ-spoVG mutant and the wild type. Membrane vesicles were significantly reduced in the bacterial cells when treated with 0.5 × MIC rhodomyrtone (P < 0.05). Decreased haemolytic activity was detected within rhodomyrtone-treated membrane vesicles. The results indicated that rhodomyrtone inhibited S. aureus SigB activity during exponentially growing phase and inhibited haemolytic activity within membrane vesicles.

The Health Beneficial Properties of Rhodomyrtus tomentosa as Potential Functional Food

Rhodomyrtus tomentosa (Aiton) Hassk. is a flowering plant belonging to the family Myrtaceae, native to southern and southeastern Asia. It has been used in traditional Vietnamese, Chinese, and Malaysian medicine for a long time for the treatment of diarrhea, dysentery, gynecopathy, stomachache, and wound healing. Moreover, R. tomentosa is used to make various food products such as wine, tea, and jam. Notably, R. tomentosa has been known to contain structurally diverse and biologically active metabolites, thus serving as a potential resource for exploring novel functional agents. Up to now, numerous phenolic and terpenoid compounds from the leaves, root, or fruits of R. tomentosa have been identified, and their biological activities such as antioxidant, antibacterial, anti-inflammatory, and anticancer have been evidenced. In this contribution, an overview of R. tomentosa and its health beneficial properties was focused on and emphasized.

Structures and Bioactive Properties of Myrtucommulones and Related Acylphloroglucinols from Myrtaceae

Myrtaceae are a group of plants that include a number of renowned species used in ethnomedicine in many areas worldwide. Their valuable therapeutic properties have stimulated a fruitful research activity addressed to the identification of the bioactive components of their extracts yielding a great diversity of terpenes; polyphenols; and other exclusive products. Among the latter, starting with the discovery of myrtucommulone A from myrtle (Myrtus communis), a series of structurally-related acylphloroglucinol compounds have been characterized from several species that represent the basic active principles to be considered in view of possible drug development. Aspects concerning chemical and biological properties of these products are reviewed in the present paper.

Multi-omic profiling to assess the effect of iron starvation in Streptococcus pneumoniae TIGR4

We applied multi-omics approaches (transcriptomics, proteomics and metabolomics) to study the effect of iron starvation on the Gram-positive human pathogen Streptococcus pneumoniae to elucidate global changes in the bacterium in a condition similar to what can be found in the host during an infectious episode. We treated the reference strain TIGR4 with the iron chelator deferoxamine mesylate. DNA microarrays revealed changes in the expression of operons involved in multiple biological processes, with a prevalence of genes coding for ion binding proteins. We also studied the changes in protein abundance by 2-DE followed by MALDI-TOF/TOF analysis of total cell extracts and secretome fractions. The main proteomic changes were found in proteins related to the primary and amino sugar metabolism, especially in enzymes with divalent cations as cofactors. Finally, the metabolomic analysis of intracellular metabolites showed altered levels of amino sugars involved in the cell wall peptidoglycan metabolism. This work shows the utility of multi-perspective studies that can provide complementary results for the comprehension of how a given condition can influence global physiological changes in microorganisms.

Comparative immunosecretome analysis of prevalent Streptococcus suis serotypes

Streptococcus suis is a major Gram-positive swine pathogen associated with a wide variety of diseases in pigs. The efforts made to develop vaccines against this pathogen have failed because of lack of common cross-reactive antigens against different serotypes. Nowadays the interest has moved to surface and secreted proteins, as they have the highest chances to raise an effective immune response because they are in direct contact with host cells and are really exposed and accessible to antibodies. In this work, we have performed a comparative immunosecretomic approach to identify a set of immunoreactive secreted proteins common to the most prevalent serotypes of S. suis. Among the 67 proteins identified, three (SSU0020, SSU0934, and SSU0215) were those predicted extracellular proteins most widely found within the studied serotypes. These immunoreactive proteins may be interesting targets for future vaccine development as they could provide possible cross-reactivity among different serotypes of this pathogen.

Systematically integrated metabonomic-proteomic studies of Escherichia coli under ciprofloxacin stress

Many antibiotics are used to kill pathogenic Escherichia coli each year, resulting in an increase in the number of antibiotic-resistant strains. In this study, an integrated metabonomic-proteomic method was performed to systematically compare the profiles of metabolites and proteins with or without ciprofloxacin (CFLX) treatment. Proteomics identified 290 altered proteins including 143 with decreased and 147 increased expression, respectively. Metabonomics identified 65 altered metabolites including 58 and 7 with decreased and increased expression, respectively. The integrated analysis showed that the CFLX inhibited the DNA replication and increased the expression of DNA gyrase and DNA topoisomerase 1, while causing a sharp decrease in metabolic activity such as the alanine, aspartate and glutamate metabolism. Moreover, CFLX affected the biosynthesis of aminoacyl- transfer RNAs (tRNAs), leading to an increase in aminoacyl-tRNAs ligases, but limited the aminoacyl-tRNAs-mediated-biosynthesis of related amino acids. In this study, we identified the metabolite and protein profiles under CFLX stress, indicating the mode of action of antibiotics in E. coli. Furthermore, the decreasing metabolic activity in E. coli may be an effective strategy to escape killing by antimicrobials or toxic compounds. The results of this study will advance our understanding of the mechanisms underlying the resistance of bacteria to antibiotics.

BIOLOGICAL SIGNIFICANCE

To investigate the biological impact of antibiotics stress on Escherichia coli, we applied an integrated metabonomic-proteomic method to systematically compare the profiles of metabolites and proteins between with and without antibiotics ciprofloxacin (CFLX) treatment. Following bioinformatics analysis showed that CFLX inhibited the DNA replication and increased the expression of DNA gyrase and DNA topoisomerase, while causing a sharp increase in the alanine, aspartate and glutamate metabolism. Moreover, CFLX affected the biosynthesis of tRNAs and limited the generation of related amino acids metabolites. In a summary, our results will provide the metabolite and protein profiles under CFLX stress, indicating the mode of action of antibiotics in E. coli. The results of this study will advance our understanding of the mechanisms underlying the resistance of bacteria to antibiotics.