Intracellular Survival and Translocation Ability of Human and Avian Campylobacter jejuni and Campylobacter coli Strains.

Campylobacter acts using complex strategies to establish and promote intestinal infections. After ingestion via contaminated foods, this bacterium invades and can survive within the intestinal cells, also inducing epithelial translocation of non-invasive intestinal bacteria. In this investigation, the ability of human and avian C. jejuni and C. coli isolates to survive within two different intestinal epithelial cells lines, Caco-2 and INT 407, as well as the intestinal translocation phenomenon, was assessed. Our data demonstrated that both C. jejuni and C. coli strains survived in Caco-2 (81.8% and 100% respectively) and INT 407 monolayers (72.7% and 100% respectively) within the first 24 h post-infection period, with a progressive reduction in the prolonged period of 48 h and 72 h post-infection. The translocation of the non-invasive E. coli 60/06 FB was remarkably increased in C. jejuni treated Caco-2 monolayers (2.36 ± 0.42 log cfu/mL) (P < 0.01) and less in those treated with C. coli (1.2 ± 0.34 log cfu/mL), compared to E. coli 60/06 FB alone (0.37 ± 0.14 log cfu/mL). Our results evidenced the ability of both human and avian strains of C. jejuni and C. coli to efficiently survive within intestinal cells and induce the translocation of a non-invasive pathogen. Overall, these findings stress how this pathogen can interact with host cells and support the hypothesis that defects in the intestinal barrier function induced by Campylobacter spp. could have potentially negative implications for human health.

Rapamycin Re-Directs Lysosome Network, Stimulates ER-Remodeling, Involving Membrane CD317 and Affecting Exocytosis, in Campylobacter Jejuni-Lysate-Infected U937 Cells.

The Gram-negative Campylobacter jejuni is a major cause of foodborne gastroenteritis in humans worldwide. The cytotoxic effects of Campylobacter have been mainly ascribed to the actions of the cytolethal distending toxin (CDT): it is mandatory to put in evidence risk factors for sequela development, such as reactive arthritis (ReA) and Guillain-Barré syndrome (GBS). Several researches are directed to managing symptom severity and the possible onset of sequelae. We found for the first time that rapamycin (RM) is able to largely inhibit the action of C. jejuni lysate CDT in U937 cells, and to partially avoid the activation of specific sub-lethal effects. In fact, we observed that the ability of this drug to redirect lysosomal compartment, stimulate ER-remodeling (highlighted by ER-lysosome and ER-mitochondria contacts), protect mitochondria network, and downregulate CD317/tetherin, is an important component of membrane microdomains. In particular, lysosomes are involved in the process of the reduction of intoxication, until the final step of lysosome exocytosis. Our results indicate that rapamycin confers protection against C. jejuni bacterial lysate insults to myeloid cells.

Lactobacillus spp. inhibit the growth of Cronobacter sakazakii ATCC 29544 by altering its membrane integrity.

The effect of the cell-free culture supernatants (CFCSs) from different Lacobacillus spp. on growth ability of Cronobacter sakazakii ATCC 29544 was investigated by time-killing studies. The antimicrobial effect was evaluated using crude and 2.5 × concentrated CFCSs. Most of the CFCSs showed a dose-dependent antimicrobial activity, with the greatest C. sakazakii growth inhibition exerted by the CFCS 2.5 × of Lactobacillus casei rhamnosus ATCC 7469. Indeed, C. sakazakii growth was completely inhibited after 4 h of incubation with the crude CFCSs of L. casei rhamnosus and Lactobacillus acidophilus and after only 2 h using the related 2.5 × CFCSs. The flow cytometric analysis revealed that CFCSs altered the permeability of C. sakazakii cell membrane, showing 55% of live cells after 30 min of treatment with 2.5 × CFCSs of L. casei rhamnosus and L. acidophilus, reaching 1% of live cells after 2 h of exposure. The CFCSs of L. casei rhamnosus and L. acidophilus have showed anti-Cronobacter activity, determining a progressively inhibition of C. sakazakii growth as result of alterations in its membrane permeability.

Development of a rapid PCR protocol to detect Vibrio parahaemolyticus in clams.

Vibrio parahaemolyticus is part of the natural microflora of estuarine and coastal marine waters and can be also present in seafood, especially shellfish and bivalve molluscs. In this study we compared the reference cultural method ISO 6887-3 with two molecular methods, multiplex PCR and real-time PCR, for the detection of two distinct genetic markers (tlh species-specific gene and tdh virulence gene) of V. parahaemolyticus in bivalve mollusc. The analyses were performed on clams inoculated with V. parahaemolyticus ATCC 43996 at T0 and after a 3 and 6 h of pre-enrichment in alkaline saline peptone water. Counts on agar plates were largely inaccurate, probably due to other Vibrio species grown on the TCBS selective agar. Multiplex PCR assays, performed using primers pairs for tdh and tlh genes, showed a detection limit of 104 CFU/g of shell stock within 6 h of pre-enrichment, respecting however the action level indicated by the National Seafood Sanitation Program guideline. Detection by tdh gene in real-time PCR reached the definitely highest sensitivity in shorter times, 101 CFU/g after 3 h of pre-enrichment, while the sensitivity for the tlh gene was not promising, detecting between 105 and 106 CFU/g after 6 h of pre-enrichment. Our findings provide a rapid routine method of detection of V. parahaemolyticus based on tdh gene by real-time PCR for commercial seafood analysis to identify the risk of gastrointestinal diseases.

[Risk assessment related to galenic products]. / Ipotesi e valutazione dei rischi correlati alle preparazioni galeniche in farmacia.

The risks associated with the preparation of galenic products prepared at a local pharmacy have been hypothesized and evaluated, also carrying out a microbiological environmental monitoring of the used surfaces. Three possible situations risk were evaluated: the first one related to the physical separation of the production phases (medium risk of occurrence), the second to the failure to restore hygienic conditions in the transition from different formulations (high risk of occurrence), the third to contamination caused by the operator itself (unacceptable risk of occurrence). This last analysis was supported by the microbiological data of environmental sampling that showed procedural errors of the operator during the cleaning phases. From our assessments it is advisable to apply a simplified system of self-control based on risk assessment and validation of critical phases including cleaning procedures for the galenic preparations.

Characterization of biosurfactants produced by Lactobacillus spp. and their activity against oral streptococci biofilm.

Lactic acid bacteria (LAB) can interfere with pathogens through different mechanisms; one is the production of biosurfactants, a group of surface-active molecules, which inhibit the growth of potential pathogens. In the present study, biosurfactants produced by Lactobacillus reuteri DSM 17938, Lactobacillus acidophilus DDS-1, Lactobacillus rhamnosus ATCC 53103, and Lactobacillus paracasei B21060 were dialyzed (1 and 6 kDa) and characterized in term of reduction of surface tension and emulsifying activity. Then, aliquots of the different dialyzed biosurfactants were added to Streptococcus mutans ATCC 25175 and Streptococcus oralis ATCC 9811 in the culture medium during the formation of biofilm on titanium surface and the efficacy was determined by agar plate count, biomass analyses, and flow cytometry. Dialyzed biosurfactants showed abilities to reduce surface tension and to emulsifying paraffin oil. Moreover, they significantly inhibited the adhesion and biofilm formation on titanium surface of S. mutans and S. oralis in a dose-dependent way, as demonstrated by the remarkable decrease of cfu/ml values and biomass production. The antimicrobial properties observed for dialyzed biosurfactants produced by the tested lactobacilli opens future prospects for their use against microorganisms responsible of oral diseases.

[Evaluation of the antimicrobial activity of products used for disinfection of work surfaces in the food industry]. / Valutazione dell'attività antimicrobica di prodotti per l'igiene e la disinfezione di superfici nel settore alimentare.

Disinfection of work surfaces is a critical step in the food industry. In this study, we evaluated the antimicrobial efficacy of four commercial products against target pathogens, using the suspension test indicated in the European Standard EN 1276: 2009. The data obtained indicate that the product containing benzalkonium chloride ("A") was the most effective with a logarithmic reduction > 5 against all microorganisms after 5 minutes of contact in simulated dirty and clean conditions. Efficacy of the product based on sodium hypochlorite ("B") was dependent on the experimental conditions applied, while for products containing hydrogen peroxide and citric acid ("C" and "D" respectively), 15 min of contact were required, in both the experimental conditions, to obtain a logarithmic reduction> 5. Exposure time to disinfectants and applied conditions appear to be important in reducing bacterial load to safe levels in the food industry.

In vitro activity of Carvacrol against titanium-adherent oral biofilms and planktonic cultures.

OBJECTIVE: The aim of this study was to test the effect of Carvacrol against oral pathogens and their preformed biofilms on titanium disc surface. METHODS: Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and biofilm inhibitory concentration (BIC) were performed to evaluate Carvacrol antibacterial activity, while flow cytometry (FCM) was used to verify the Carvacrol effect on esterase activity and membrane permeability. Carvacrol was tested in vitro on single- and multi-species biofilms formed on titanium disc by Streptococcus mutans ATCC 25175, Porphyromonas gingivalis ATCC 33277 or Fusobacterium nucleatum ATCC 25586, in different combinations, comparing its effect to that of chlorhexidine. RESULTS: The pathogens were sensitive to Carvacrol with MICs and MBCs values of 0.25 % and 0.50 % and BICs of 0.5 % for S. mutans ATCC 25175 and 1 % for P. gingivalis ATCC 33277 and F. nucleatum ATCC 25586. FCM analysis showed that treatment of planktonic cultures with Carvacrol caused an increase of damaged cells and a decrement of bacteria with active esterase activity. Moreover, Carvacrol demonstrated greater biofilm formation preventive property compared to chlorhexidine against titanium-adherent single- and multi-specie biofilms, with statistically significant values. CONCLUSIONS: Carvacrol showed inhibitory activity against the tested oral pathogens and biofilm formation preventive property on their oral biofilm; then, it could be utilized to control and prevent the colonization of microorganisms with particular significance in human oral diseases. CLINICAL RELEVANCE: This natural compound may be proposed in daily hygiene formulations or as an alternative agent supporting traditional antimicrobial protocols to prevent periodontal diseases in implanted patients.

CadF expression in Campylobacter jejuni strains incubated under low-temperature water microcosm conditions which induce the viable but non-culturable (VBNC) state.

Campylobacter jejuni is a major gastrointestinal pathogen that colonizes host mucosa via interactions with extracellular matrix proteins such as fibronectin. The aim of this work was to study in vitro the adhesive properties of C. jejuni ATCC 33291 and C. jejuni 241 strains, in both culturable and viable but non-culturable (VBNC) forms. To this end, the expression of the outer-membrane protein CadF, which mediates C. jejuni binding to fibronectin, was evaluated. VBNC bacteria were obtained after 46-48 days of incubation in freshwater at 4 °C. In both cellular forms, the expression of the cadF gene, assessed at different time points by RT-PCR, was at high levels until the third week of VBNC induction, while the intensity of the signal declined during the last stage of incubation. CadF protein expression by the two C. jejuni strains was analysed using 2-dimensional electrophoresis and mass spectrometry; the results indicated that the protein, although at low levels, is also present in the VBNC state. Adhesion assays with culturable and VBNC cells, evaluated on Caco-2 monolayers, showed that non-culturable bacteria retain their ability to adhere to intestinal cells, though at a reduced rate. Our results demonstrate that the C. jejuni VBNC population maintains an ability to adhere and this may thus have an important role in the pathogenicity of this microorganism.

Antagonistic activity of Lactobacillus acidophilus ATCC 4356 on the growth and adhesion/invasion characteristics of human Campylobacter jejuni.

The aim of this research was to determine the potential probiotic activity of Lactobacillus acidophilus ATCC 4356 against several human Campylobacter jejuni isolates. The ability to inhibit the pathogen's growth was evaluated by co-culture experiments as well as by antimicrobial assays with cell-free culture supernatant (CFCS), while interference with adhesion/invasion to intestinal Caco-2 cells was studied by exclusion, competition, and displacement tests. In the co-culture experiments L. acidophilus ATCC 4356 strain reduced the growth of C. jejuni with variable percentages of inhibition related to the contact time. The CFCS showed inhibitory activity against C. jejuni strains, stability to low pH, and thermal treatment and sensitivity to proteinase K and trypsin. L. acidophilus ATCC 4356 was able to reduce the adhesion and invasion to Caco-2 cells by most of the human C. jejuni strains. Displacement and exclusion mechanisms seem to be the preferred modalities, which caused a significant reduction of adhesion/invasion of pathogens to intestinal cells. The observed inhibitory properties of L. acidophilus ATCC 4356 on growth ability and on cells adhesion/invasion of C. jejuni may offer potential use of this strain for the management of Campylobacter infections.

A proposal for the reference intervals of the Italian microbiota "scaffold" in healthy adults.

Numerous factors, ranging from genetics, age, lifestyle, and dietary habits to local environments, contribute to the heterogeneity of the microbiota in humans. Understanding the variability of a "healthy microbiota" is a major challenge in scientific research. The gut microbiota profiles of 148 healthy Italian volunteers were examined by 16S rRNA gene sequencing to determine the range and diversity of taxonomic compositions in the gut microbiota of healthy populations. Possible driving factors were evaluated through a detailed anamnestic questionnaire. Microbiota reference intervals were also calculated. A "scaffold" of a healthy Italian gut microbiota composition was identified. Differences in relative quantitative ratios of microbiota composition were detected in two clusters: a bigger cluster (C2), which included 124 subjects, was characterized by more people from the northern Italian regions, who habitually practised more physical activity and with fewer dietary restrictions. Species richness and diversity were significantly higher in this cluster (C2) than in the other one (C1) (C1: 146.67 ± 43.67; C2: 198.17 ± 48.47; F = 23.40; P < 0.001 and C1: 16.88 ± 8.66; C2: 35.01 ± 13.40; F = 40.50; P < 0.001, respectively). The main contribution of the present study was the identification of the existence of a primary healthy microbiological framework that is only marginally affected by variations. Taken together, our data help to contextualize studies on population-specific variations, including marginal aspects, in human microbiota composition. Such variations must be related to the primary framework of a healthy microbiota and providing this perspective could help scientists to better design experimental plans and develop strategies for precision tailored microbiota modulation.

Comparative effect of chlorhexidine and some mouthrinses on bacterial biofilm formation on titanium surface.

The aim of the present study was to evaluate the effectiveness of chlorhexidine digluconate (CHX) and commonly used mouthrinses to single- and poly-species biofilms by S. mutans, S. aureus and P. aeruginosa, on titanium discs of grade IV. The formation of single- and poly-species biofilms at 16.5, 40.5 and 64.5-h incubation on titanium surface was evaluated by plate count (CFU ml⁻¹) before and after exposure to CHX and four mouthrinses (Curasept, Listerine, Meridol and Buccagel) and expressed as percentage of Inhibitory Activity (IA%). The application of the different anti-plaque formulations on biofilm can reduce the adhesion of bacteria to titanium surface with different degrees. The higher efficacy was observed for Listerine that shows IA% = 100 on the biofilm formed by S. mutans at 16.5 h. Log count of CFU was dependent to culture time and four mouthrinses for S. mutans and S. aureus, whilst was not dependent to culture time but to mouthrinses for P. aeruginosa. In general, the efficacy was particularly lesser to poly-species biofilms; no statistical differences were evidenced between all the mouthrinses and CHX as control group. The tested mouthrinses, compared to reference CHX 0.2%, have demonstrated a significant lower antibacterial activity than Listerine towards the experimental biofilms. This "in vitro" biofilm model should prove extremely useful for pre-clinical testing of anti-plaque agents, which inhibit biofilm formation, can prevent subsequent implant failure.

In vitro synergistic activities of essential oils and surfactants in combination with cosmetic preservatives against Pseudomonas aeruginosa and Staphylococcus aureus.

The aim of this study is to evaluate possible synergistic antimicrobial interactions between common cosmetic preservatives and selected essential oils or surfactants. The antimicrobial efficacy of six essential oils, three surfactants and five preservatives against Pseudomonas aeruginosa ATCC 9027 and Staphylococcus aureus ATCC 43387 was assessed by a broth micro-dilution assay. MICs for individual and combined antimicrobials were determined and then transformed to fractional inhibitory concentration (FIC) indexes. All essential oils exhibited antibacterial activity; among surfactants, bacteria resulted most susceptible to the cationic agent. Synergy was observed when essential oils of eucalyptus and mint were combined with methylparaben against P. aeruginosa, while essential oils of mint, oregano and sage combined with propylparaben and imidazolidinyl urea acted against S. aureus. Many binary mixtures of preservatives and surfactants produced synergistic activity with the most effective interactions involving the cationic and amphoteric compounds under study. FIC indexes demonstrated synergistic effects when preservatives were combined with either essential oils or surfactants against both bacterial strains. These results highlight the potential usefulness of essential oils and surfactants to enhance the activities of conventional biocides. This kind of study should contribute to the selection and optimization of preservative systems for cosmetic preparations.

Synergistic combinations of antimicrobial peptides against biofilms of methicillin-resistant Staphylococcus aureus (MRSA) on polystyrene and medical devices.

OBJECTIVES: Antimicrobial research is being focused to look for more effective therapeutics against antibiotic-resistant infections such as those caused by methicillin-resistant Staphylococcus aureus (MRSA). In this regard, antimicrobial peptides (AMPs) appear to be a promising solution. The aim of the present study was to investigate the potential activity of temporin A, citropin 1.1, CA(1-7)M(2-9)NH2 and Pal-KGK-NH2 in synergistic activity against MRSA biofilms developed on polystyrene surface (PSS) and central venous catheter (CVC). METHODS: The study was subdivided into distinct phases to assess the ability of AMPs to inhibit biofilm formation, to identify possible synergy between AMPs, and to eradicate preformed biofilms on PSS and CVC using AMPs alone or in combination. RESULTS: Activity of the AMPs was particularly evident in the inhibition of biofilm formation on PSS and CVC, whilst the eradication of preformed biofilms was more difficult and was reached only after 24h of contact. The synergistic activity of AMP combinations, selected by their fractional inhibitory concentration index (FICI), led to an improvement in the performance of all of the molecules in the removal of different biofilms. CONCLUSION: Overall, AMPs could represent the next generation of antimicrobial agents for a prophylactic or therapeutic tool to control biofilms of antibiotic-resistant bacteria and/or biofilm-associated infections on different medical devices.

Marine Alkaloid 2,2-Bis(6-bromo-3-indolyl) Ethylamine and Its Synthetic Derivatives Inhibit Microbial Biofilms Formation and Disaggregate Developed Biofilms.

The antimicrobial activity of the marine bisindole alkaloid 2,2-bis(6-bromo-3-indolyl) ethylamine (1) and related synthetic analogues (compounds 2⁻8) against target microorganisms was investigated by Minimum Inhibitory Concentration (MIC) determination. Compound 1 showed the greatest antimicrobial activity with the lowest MIC (8 mg/L) against Escherichia coli, Staphylococcus aureus, and Klebsiella pneumoniae, while the derivatives exhibited higher MICs values (from 16 to 128 mg/L). Compounds 1, 3, 4, and 8, the most active ones, were then tested against E. coli, S. aureus, K. pneumoniae, and Candida albicans during biofilms formation as well as on 24 h developed biofilms. The natural alkaloid 1 inhibited the biofilm formation of all the tested microorganisms up to 82.2% and disaggregated biofilms of E. coli, S. aureus, K. pneumoniae, and C. albicans after 30 min of contact, as assessed by viable plate count and crystal violet (CV) staining (optical density at 570 nm). Synthetic derivatives 3, 4, and 8 displayed anti-biofilm activity toward individual bacterial populations. This study highlights the potential of marine bisindole alkaloid 1 as anti-biofilm agent and shows, through a preliminary structure activity relationship (SAR), the importance of halogens and ethylamine side chain for the antimicrobial and antibiofilm activities of this bisindole series.

Experimental approach for a possible integrated protocol to determine sanitizer activity against both planktonic bacteria and related biofilms.

The persistence of pathogenic bacteria in industrial settings is linked to biofilm embedded bacteria resistance to antimicrobial and disinfectant methods effective against planktonic cells. We proposed an experimental approach to evaluate sanitizers effectiveness against both planktonic microorganisms and related biofilms as possible integration of the official EN 1276 procedure. Firstly, the efficacy of three chemicals sanitizers was tested on planktonic cells of Escherichia coli O157:H7 ATCC 35150, Staphylococcus aureus ATCC 43387, Pseudomonas aeruginosa ATCC 9027, Enterococcus faecalis ATCC 29212 and Candida albicans ATCC 14053 using the suspension test indicated by EN 1276 in both dirty and clear simulated conditions (0.3% or 0.03% of bovine serum albumen). The sanitizers were tested against the related biofilms developed on stainless steel for 48 h at room temperature. The sanitizers (SANI 626, SUPERIG, IGIEN 155) reached 5-logarithmic reduction at the manufacture's recommended concentrations after 30 s and 5 min against planktonic microorganisms but, sometimes, the organic load interfered with their activity. The same concentrations tested with the proposed protocol weren't effective against biofilms and a log reduction >3 was reached using higher concentrations of the sanitizers and 15 min of contact, with the exception of IGIEN 155. The efficacy of a disinfectant/sanitizer is assessed against planktonic microorganisms and bacteria adhered to surface, while those embedded in biofilms are not taken into consideration. The proposed protocol could be used to evaluate the effectiveness of a sanitizer also against microorganisms organized in biofilms, in order to give to the users more detailed information on its activity.

Chitosans as new tools against biofilms formation on the surface of silicone urinary catheters.

Urinary catheters contamination by microorganisms is a major cause of hospital acquired infections and represents a limitation for long-term use. In this work, biofilms of Klebsiella pneumoniae and Escherichia coli clinical isolates were developed on urinary catheters for 48 and 72 h in artificial urine medium (AUM) with different molecular weight chitosans (AUM-CS solutions) at pH 5.0. The number of viable bacteria was determined by standard plate count agar while crystal violet (CV) staining was carried out to assess biomass production (optical density at 570 nm) in the mentioned conditions. Re-growth of each strain was also evaluated after 24 h re-incubation of the treated catheters. Significant decreases of log CFU/catheter and biomass production were observed for all the biofilms developed in AUM-CS compared with the controls in AUM. The percentages of biofilm removal were slightly higher for E. coli biofilms (up to 90.4%) than those of K. pneumoniae (89.7%); in most cases, the complete inhibition of bacterial re-growth on treated catheter pieces was observed. Contact time influenced chitosan efficacy rather than its molecular weight or the biofilms age. The results confirmed the potentiality of chitosans as a biomacromolecule tool to contrast biofilm formation and reduce bacterial re-growth on urinary catheters.

Chitosan Loaded into a Hydrogel Delivery System as a Strategy to Treat Vaginal Co-Infection.

Polymeric hydrogels are common dosage forms designed for the topical administration of antimicrobial drugs to treat vaginal infections. One of the major advantages of using chitosan in these formulations is related to the intrinsic and broad antimicrobial activity exerted on bacteria and fungi by this natural polymer. Most vaginal yeast infections are caused by the pathogenic fungus Candida albicans. However, despite the anti-Candida activity towards and strains susceptibility to low molecular weight chitosan being documented, no information is available regarding the antimicrobial efficacy of mixed hydrogels in which chitosan is dispersed in a polymeric matrix. Therefore, the aim of the study is to evaluate the anti-Candida activity against eight different albicans and non-albicans strains of a mixed hydroxypropyl methylcellulose (HPMC)/chitosan hydrogel. Importantly, chitosan was dispersed in HPMC matrix either assembled in nanoparticles or in a monomolecular state to eventually correlate any variation in terms of rheological and mucoadhesive properties, as well as anti-Candida activity, with the chitosan form. Hydrogels containing 1% w/w chitosan, either as free polymer chain or assembled in nanoparticles, showed an improved mucoadhesiveness and an anti-Candida effect against all tested albicans and non-albicans strains. Overall, the results demonstrate the feasibility of preparing HPMC/CS mixed hydrogels intended for the prevention and treatment of Candida infections after vaginal administration.

Antimicrobial Activity of Different Antimicrobial Peptides (AMPs) Against Clinical Methicillin-resistant Staphylococcus aureus (MRSA).

BACKGROUND: Antimicrobial research is being focused to look for more effective therapeutics against antibiotic-resistant infections caused by methicillin-resistant Staphylococcus aureus (MRSA). In this direction, antimicrobial peptides (AMP) appear as promising tool. OBJECTIVES: This study evaluated the antimicrobial activity of different AMPs (Citropin 1.1, Temporin A, Pexiganan, CA(1-7)M(2-9)NH2, Pal-KGK-NH2, Pal-KKKK-NH2, LL-37) against human MRSA clinical isolates. METHODS: The Minimum Inhibitory Concentration (MIC) was assessed for each AMP; then, the most active ones (Citropin 1.1, Temporin A, CA(1-7)M(2-9)NH2 and Pal-KGK-NH2) were tested against selected MRSA strains by time-kill studies. RESULTS: The lowest MIC value was observed for Pal-KGK-NH2 (1 µg/ml), followed by Temporin A (4- 16 µg/ml), CA(1-7)M(2-9)NH2 (8-16 µg/ml) and Citropin 1.1 (16-64 µg/ml), while higher MICs were evidenced for LL-37, Pexiganan and Pal-KKKK-NH2 (> 128 µg/ml). In time-kill experiments, Citropin 1.1 and CA(1-7)M(2-9)NH2 showed a relatively high percentage of growth inhibition (>30 %) for all the tested MRSA clinical isolates, with a dose-dependent activity resulting in the highest percentage of bacterial growth inhibition (89.39%) at 2MIC concentration. CONCLUSION: Overall, our data demonstrated the potential of some AMPs against MRSA isolates, such as Citropin 1.1 and CA(1-7)M(2-9)NH2, that represents a promising area of development for different clinical applications.

Chitosan-based nanosystems and their exploited antimicrobial activity.

Chitosan is a biodegradable and biocompatible natural polysaccharide that has a wide range of applications in the field of pharmaceutics, biomedical, chemical, cosmetics, textile and food industry. One of the most interesting characteristics of chitosan is its antibacterial and antifungal activity, and together with its excellent safety profile in human, it has attracted considerable attention in various research disciplines. The antimicrobial activity of chitosan is dependent on a number of factors, including its molecular weight, degree of deacetylation, degree of substitution, physical form, as well as structural properties of the cell wall of the target microorganisms. While the sole use of chitosan may not be sufficient to produce an adequate antimicrobial effect to fulfil different purposes, the incorporation of this biopolymer with other active substances such as drugs, metals and natural compounds in nanosystems is a commonly employed strategy to enhance its antimicrobial potential. In this review, we aim to provide an overview on the different approaches that exploit the antimicrobial activity of chitosan-based nanosystems and their applications, and highlight the latest advances in this field.