Biofilms and their relevance to veterinary medicine

Targeted treatment for biofilm-based infections using PEGylated tobramycin

Chronic infections often involve biofilm-based bacteria, in which the biofilm results in significant resistance against antimicrobial agents and prevents eradication of the infection. The physicochemical barrier presented by the biofilm matrix is a major impediment to the delivery of many antibiotics. Previously, PEGylation has been shown to improve antibiotic penetration into biofilms in vitro. In these studies, PEGylating tobramycin was investigated both in vitro and in vivo. Two distinct PEGylated tobramycin molecules were synthesized (mPEG-SA-Tob and mPEG-AA-Tob). Then, in a P. aeruginosa biofilm in vitro model, we found that mPEG-SA-Tob can operate as a prodrug and showed 7 times more effectiveness than tobramycin (MIC80: 14 μM vs.100 μM). This improved biofilm eradication is attributable to the fact that mPEG-SA-Tob can aid tobramycin to penetrate through the biofilm and overcome the alginate-mediated antibiotic resistance. Finally, we used an in vivo biofilm-based chronic pulmonary infection rat model to confirm the therapeutic impact of mPEG-SA-Tob on biofilm-based chronic lung infection. mPEG-SA-Tob has a better therapeutic impact than tobramycin in that it cannot only stop P. aeruginosa from multiplying in the lungs but can also reduce inflammation caused by infections and prevent a recurrence infection. Overall, our findings show that PEGylated tobramycin is an effective treatment for biofilm-based chronic lung infections.

TCM formula for trauma treatment screening and its role of promoting infectious wound coalescence investigating

In pet clinics, the number of cases using trauma drugs accounts for >10% of the total number of cases, and most wounds are healing by second intention. The prolongation of wound healing time causes inconvenience and burden to pets and pet owners. Therefore, how to reduce wound healing time and achieve maximum recovery of tissue function and aesthetics is one of the focuses of veterinary clinical practice. Wound suppuration caused by Staphylococcus aureus and Pseudomonas aeruginosa is the main cause of delaying wound healing. Clinically, available antimicrobial treatments are almost exhausted due to the production of large numbers of resistant bacteria. At present, there are no bacteria resistant to traditional Chinese medicine (TCM), which makes TCM have the potential to become an effective drug for the treatment of bacterial infections, so the use of TCM in the treatment of traumatic infections has broad prospects. Based on the characteristics of infection syndrome, three different prescriptions were formulated in our laboratory, and the most effective prescription and dosage form was screened and named Lianrong Healing Cream (LRHC). The results showed that LRHC regulated the expression of fibroblast growth factor-2 (FGF-2), epidermal growth factor-1 (EGF-1), transforming growth factor-β (TGF-β) and vascular endothelial growth factor-1 (VEGF-1) genes in wound tissues and fibroblasts, thereby accelerating wound healing and repairing wound appearance and function. The results of this study may be help to develop TCM formulation for traumatic infections.

Antibiotic Resistance: Do We Need Only Cutting-Edge Methods, or Can New Visions Such as One Health Be More Useful for Learning from Nature?

Antibiotic resistance is an increasing global problem for public health, and focusing on biofilms has provided further insights into resistance evolution in bacteria. Resistance is innate in many bacterial species, and many antibiotics are derived from natural molecules of soil microorganisms. Is it possible that nature can help control AMR diffusion? In this review, an analysis of resistance mechanisms is summarized, and an excursus of the different approaches to challenging resistance spread based on natural processes is presented as "lessons from Nature". On the "host side", immunotherapy strategies for bacterial infections have a long history before antibiotics, but continuous new inputs through biotechnology advances are enlarging their applications, efficacy, and safety. Antimicrobial peptides and monoclonal antibodies are considered for controlling antibiotic resistance. Understanding the biology of natural predators is providing new, effective, and safe ways to combat resistant bacteria. As natural enemies, bacteriophages were used to treat severe infections before the discovery of antibiotics, marginalized during the antibiotic era, and revitalized upon the diffusion of multi-resistance. Finally, sociopolitical aspects such as education, global action, and climate change are also considered as important tools for tackling antibiotic resistance from the One Health perspective.

Biofilm-a Syntrophic Consortia of Microbial Cells: Boon or Bane?

Biofilm is the conglomeration of microbial cells which is associated with a surface. In the recent times, the study of biofilm has gained popularity and vivid research is being done to know about the effects of biofilm and that it consists of many organisms which are symbiotic in nature, some of which are human pathogens. Here, in this study, we have discussed about biofilms, its formation, relevance of its presence in the biosphere, and the possible remediations to cope up with its negative effects. Since removal of biofilm is difficult, emphasis has been made to suggest ways to prevent biofilm formation and also to devise ways to utilize biofilm in an economically and environment-friendly method.

Collective behavior and virulence arsenal of the fish pathogen Piscirickettsia salmonis in the biofilm realm

Piscirickettsiosis is a fish disease caused by the Gram-negative bacterium Piscirickettsia salmonis. This disease has a high socio-economic impact on the Chilean salmonid aquaculture industry. The bacterium has a cryptic character in the environment and their main reservoirs are yet unknown. Bacterial biofilms represent a ubiquitous mechanism of cell persistence in diverse natural environments and a risk factor for the pathogenesis of several infectious diseases, but their microbiological significance for waterborne veterinary diseases, including piscirickettsiosis, have seldom been evaluated. This study analyzed the in vitro biofilm behavior of P. salmonis LF-89^T (genogroup LF-89) and CA5 (genogroup EM-90) using a multi-method approach and elucidated the potential arsenal of virulence of the P. salmonis LF-89^T type strain in its biofilm state. P. salmonis exhibited a quick kinetics of biofilm formation that followed a multi-step and highly strain-dependent process. There were no major differences in enzymatic profiles or significant differences in cytotoxicity (as tested on the Chinook salmon embryo cell line) between biofilm-derived bacteria and planktonic equivalents. The potential arsenal of virulence of P. salmonis LF-89^T in biofilms, as determined by whole-transcriptome sequencing and differential gene expression analysis, consisted of genes involved in cell adhesion, polysaccharide biosynthesis, transcriptional regulation, and gene mobility, among others. Importantly, the global gene expression profiles of P. salmonis LF-89^T were not enriched with virulence-related genes upregulated in biofilm development stages at 24 and 48 h. An enrichment in virulence-related genes exclusively expressed in biofilms was also undetected. These results indicate that early and mature biofilm development stages of P. salmonis LF-89^T were transcriptionally no more virulent than their planktonic counterparts, which was supported by cytotoxic trials, which, in turn, revealed that both modes of growth induced important and very similar levels of cytotoxicity on the salmon cell line. Our results suggest that the aforementioned biofilm development stages do not represent hot spots of virulence compared with planktonic counterparts. This study provides the first transcriptomic catalogue to select specific genes that could be useful to prevent or control the (in vitro and/or in vivo) adherence and/or biofilm formation by P. salmonis and gain further insights into piscirickettsiosis pathogenesis.

Positive biofilms to guide surface microbial ecology in livestock buildings

The increase in human consumption of animal proteins implies changes in the management of meat production. This is followed by increasingly restrictive regulations on antimicrobial products such as chemical biocides and antibiotics, used in particular to control pathogens that can spread zoonotic diseases. Aligned with the One Health concept, alternative biological solutions are under development and are starting to be used in animal production. Beneficial bacteria able to form positive biofilms and guide surface microbial ecology to limit microbial pathogen settlement are promising tools that could complement existing biosecurity practices to maintain the hygiene of livestock buildings. Although the benefits of positive biofilms have already been documented, the associated fundamental mechanisms and the rationale of the microbial composition of these new products are still sparce. This review provides an overview of the envisioned modes of action of positive biofilms used on livestock building surfaces and the resulting criteria for the selection of the appropriate microorganisms for this specific application. Limits and advantages of this biosecurity approach are discussed as well as the impact of such practices along the food chain, from farm to fork.

The Occurrence of Microplastics and the Formation of Biofilms by Pathogenic and Opportunistic Bacteria as Threats in Aquaculture

Aquaculture is the most rapidly growing branch of animal production. The efficiency and quality of the produced food depends on sustainable management, water quality, feed prices and the incidence of diseases. Micro- (MP < 5 mm) and nanoplastic (NP < 1000 nm) particles are among the current factors causing serious water pollution. This substance comes solely from products manufactured by humans. MP particles migrate from the terrestrial to the aquatic environment and adversely affect, especially, the health of animals and humans by being a favorable habitat and vector for microbial pathogens and opportunists. More than 30 taxa of pathogens of humans, aquacutural animals and plants, along with opportunistic bacteria, have been detected in plastic-covering biofilm to date. The mobility and durability of the substance, combined with the relatively closed conditions in aquacultural habitats and pathogens’ affinity to the material, make plastic particles a microbiological medium threatening the industry of aquaculture. For this reason, in addition to the fact of plastic accumulation in living organisms, urgent measures should be taken to reduce its influx into the environment. The phenomenon and its implications are related to the concept of one health, wherein the environment, animals and humans affect each other’s fitness.

Cellulose Acetate Membranes Modification by Aminosilane Grafting in Supercritical Carbon Dioxide towards Antibiofilm Properties

The study explores the grafting of cellulose acetate microfiltration membranes with an aminosilane to attain antibiofilm properties. The grafting reaction was performed in the supercritical carbon dioxide used as a transport and reaction medium. The FTIR analyses and dissolution tests confirmed the covalent bonding between the aminosilane and polymer. The membranes' microstructure was investigated using a dual-beam SEM and ion microscopy, and no adverse effects of the processing were found. The modified membranes showed a more hydrophilic nature and larger water permeate flow rate than the neat cellulose acetate membranes. The tests in a cross-filtration unit showed that modified membranes were considerably less blocked after a week of exposure to Staphylococcus aureus and Escherichia coli than the original ones. Microbiological investigations revealed strong antibiofilm properties of the grafted membranes in experiments with Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Salmonella Enteritidis.

In vitro antibacterial and antibiofilm effects of cold atmospheric microwave plasma against Pseudomonas aeruginosa causing canine skin and ear infections

BACKGROUND

Pseudomonas aeruginosa is an opportunist pathogen that causes purulent inflammation in the skin and in the ears of dogs. Among the various virulence factors of P. aeruginosa, biofilms have been reported to result in antibiotic resistance, leading to therapeutic limitations. Cold atmospheric microwave plasma (CAMP) is known to have a high antimicrobial effect, which causes physical cell wall rupture and DNA damage.

HYPOTHESIS/OBJECTIVES

The objective of this study was to evaluate the antibacterial and antibiofilm effects of CAMP against planktonic bacteria and the biofilm of P. aeruginosa.

METHODS AND MATERIALS

The antibacterial effect of CAMP against P. aeruginosa ATCC10145 and clinical isolates (n = 30) was evaluated using the colony count method. We also assessed the effect of CAMP on biofilm of P. aeruginosa ATCC strain by the colony count method, water-soluble tetrazolium salt (WST) assay and confocal laser scanning microscopy (CLSM).

RESULTS

The complete eradication of P. aeruginosa (ATCC strain and clinical isolates) was achieved within 120 s at 50 W, and clinical isolates required 60 s shorter than the ATCC strain for complete eradication at 50 W. We also confirmed the time-dependent bactericidal effect of CAMP at 50 W against ATCC strain biofilm.

CONCLUSIONS AND CLINICAL IMPORTANCE

CAMP was effective against both planktonic bacteria and biofilm formation of P. aeruginosa. However, further studies on in vivo efficacy and safety in canine skin and ears are necessary to fully validate its clinical application.

Antibacterial and antibiofilm activities and synergism with florfenicol from the essential oils of Lippia sidoides and Cymbopogon citratus against Aeromonas hydrophila

AIMS

Aeromonas hydrophila is an opportunistic bacterium, with a high capacity for biofilm production, which can cause severe damage in aquaculture. The objective of this study was to identify the chemical compounds of the essential oils of Lippia sidoides (EOLS) and Cymbopogon citratus (EOCC), and to evaluate the biocidal, antibiofilm and synergistic action with the antimicrobial florfenicol of these essential oils (EOs) against A. hydrophila.

METHODS AND RESULTS

The antibacterial activity of EOLS and EOCC was verified by the minimum bactericidal concentration and by the action of these EOs against both forming and consolidated biofilms. The synergistic activity of EOs with florfenicol was performed using the checkerboard technique. The main component of EOLS and EOCC was carvacrol (44.50%) and α-citral (73.56%), respectively. Both EOs showed weak inhibitory activity (≥3125.00 µg ml^-1 ). Two bacterial isolates were able to produce biofilm, and EOLS and EOCC acted upon the bacterial isolates to prevent biofilm formation. A bactericidal effect was verified for EOLS in the previously consolidated biofilm for both isolates and for EOCC in only one of the isolates. In general, EOLS had a synergistic effect with florfenicol, while EOCF had an additive effect.

CONCLUSIONS

Both EOs were able to interfere with biofilm formation and did not have an antagonistic effect in combination with florfenicol. The best results were found for EOLS, which showed a synergistic effect with florfenicol and the ability to interfere in the formation of consolidated biofilm.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study highlights the potential of EOLS and EOCC to interfere in biofilm and act in synergy with florfenicol to reduce the occurrence of A. hydrophila. Development of these compounds may contribute to the development of herbal medicines in aquaculture.

Phage Therapy as a Focused Management Strategy in Aquaculture

Therapeutic bacteriophages, commonly called as phages, are a promising potential alternative to antibiotics in the management of bacterial infections of a wide range of organisms including cultured fish. Their natural immunogenicity often induces the modulation of a variated collection of immune responses within several types of immunocytes while promoting specific mechanisms of bacterial clearance. However, to achieve standardized treatments at the practical level and avoid possible side effects in cultivated fish, several improvements in the understanding of their biology and the associated genomes are required. Interestingly, a particular feature with therapeutic potential among all phages is the production of lytic enzymes. The use of such enzymes against human and livestock pathogens has already provided in vitro and in vivo promissory results. So far, the best-understood phages utilized to fight against either Gram-negative or Gram-positive bacterial species in fish culture are mainly restricted to the Myoviridae and Podoviridae, and the Siphoviridae, respectively. However, the current functional use of phages against bacterial pathogens of cultured fish is still in its infancy. Based on the available data, in this review, we summarize the current knowledge about phage, identify gaps, and provide insights into the possible bacterial control strategies they might represent for managing aquaculture-related bacterial diseases.

Biofilm and Equine Limb Wounds

In chronic wounds in humans, biofilm formation and wound chronicity are linked, as biofilms contribute to chronic inflammation and delayed healing. Biofilms are aggregates of bacteria, and living as biofilms is the default mode of bacterial life; within these aggregates, the bacteria are protected from both antimicrobial substances and the immune response of the host. In horses, delayed healing is more commonly seen in limb wounds than body wounds. Chronic inflammation and hypoxia are the main characteristics of delayed wound healing in equine limbs, and biofilms might also contribute to this healing pattern in horses. However, biofilm formation in equine wounds has been studied to a very limited degree. Biofilms have been detected in equine traumatic wounds, and recent experimental models have shown that biofilms protract the healing of equine limb wounds. Detection of biofilms within wounds necessitates advanced techniques that are not available in routine diagnostic yet. However, infections with biofilm should be suspected in equine limb wounds not healing as expected, as they are in human wounds. Treatment should be based on repeated debridement and application of topical antimicrobial therapy.

Antibiofilm activity of silver nanoparticles against biofilm forming Staphylococcus pseudintermedius isolated from dogs with otitis externa

BACKGROUND

Silver nanoparticles (AgNPs) are known to possess antimicrobial properties. Although the antibiofilm activity of AgNPs has been demonstrated in humans, this activity has not yet been elucidated in veterinary medicine.

OBJECTIVES

The purpose of this study was to evaluate the antibiofilm activity of silver nanoparticles against Staphylococcus pseudintermedius.

METHODS

Ten isolates of S. pseudintermedius obtained from dogs with otitis externa were treated with AgNPs, and the antibiofilm activity was measured using a modified microtiter plate and Congo red agar (CRA) method and scanning electron microscopy.

RESULTS

AgNPs displayed a significant dose-dependent antibiofilm activity and reduced biofilm formation at concentrations of 20 and 10 µg/ml (p < 0.05). S. pseudintermedius exposed to 20 µg/ml of AgNPs formed less bacterial slime compared to the controls on CRA plates. Scanning electron micrographs showed that the biofilm had few individually scattered cells along its surface when treated with AgNP concentrations of 20 and 10 µg/ml. Untreated surfaces showed an aggregated biofilm.

CONCLUSIONS

Our results suggested that AgNP may be a valuable alternative antibiofilm agent for canine otitis externa.

Evaluation of the antioxidant, antibacterial, and antibiofilm activity of the sesquiterpene nerolidol

The aim of this study was to evaluate the antioxidant, antibacterial, and antibiofilm activities of nerolidol. The antioxidant activity of nerolidol was determined using the total antioxidant activity method. Antibacterial activity was performed using the microdilution method to determine the minimum inhibitory concentration (MIC) against seven standard strains of the ATCC and four bacterial clinical isolates with a resistance profile, following the Clinical and Laboratory Standards Institute (CLSI). The antibiofilm activity of nerolidol was performed using the crystal violet method. The results of the antioxidant test revealed a total antioxidant activity of 93.94%. Nerolidol inhibited the growth of Staphylococcus aureus (MIC = 1 mg/mL), Streptococcus mutans (MIC = 4 mg/mL), Pseudomonas aeruginosa (MIC = 0.5 mg/mL), and Klebsiella pneumoniae (MIC = 0.5 mg/mL). For clinical isolates, nerolidol showed an inhibitory potential against multidrug-resistant P. aeruginosa, K. pneumoniae carbapenemase (MIC = 0.5 mg/mL), methicillin-susceptible S. aureus (MIC = 2 mg/mL), and methicillin-resistant S. aureus (MIC = 2 mg/mL). Nerolidol showed similar antibacterial activity against ATCC strains and hospital clinical isolates with resistance profile, suggesting that even though these strains are resistant to antibiotics, they are still sensitive to nerolidol. Nerolidol exerted a dose-dependent effect on the inhibition of biofilm formation, even at subinhibitory concentrations. Nerolidol inhibited bacterial biofilms of ATCC strains at a rate ranging from 51 to 98%, at concentrations ranging from 0.5 to 4 mg/mL. For clinical bacterial isolates, biofilm inhibition ranged from 6 to 60%. Therefore, the present study showed the antioxidant, antibacterial, and antibiofilm properties of nerolidol.

Pulmonary biofilm-based chronic infections and inhaled treatment strategies

Certain pulmonary diseases, such as cystic fibrosis (CF), non-CF bronchiectasis, chronic obstructive pulmonary disease, and ventilator-associated pneumonia, are usually accompanied by respiratory tract infections due to the physiological alteration of the lung immunological defenses. Recurrent infections may lead to chronic infection through the formation of biofilms. Chronic biofilm-based infections are challenging to treat using antimicrobial agents. Therefore, effective ways to eradicate biofilms and thus relieve respiratory tract infection require the development of efficacious agents for biofilm destruction, the design of delivery carriers with biofilm-targeting and/or penetrating abilities for these agents, and the direct delivery of them into the lung. This review provides an in-depth description of biofilm-based infections caused by pulmonary diseases and focuses on current existing agents that are administered by inhalation into the lung to treat biofilm, which include i) inhalable antimicrobial agents and their combinations, ii) non-antimicrobial adjuvants such as matrix-targeting enzymes, mannitol, glutathione, cyclosporin A, and iii) liposomal formulations of anti-biofilm agents. Finally, novel agents that have shown promise against pulmonary biofilms as well as traditional and new devices for pulmonary delivery of anti-biofilm agents into the lung are also discussed.

The Less Expensive Choice: Bacterial Strategies to Achieve Successful and Sustainable Reciprocal Interactions

Bacteria, the first organisms that appeared on Earth, continue to play a central role in ensuring life on the planet, both as biogeochemical agents and as higher organisms' symbionts. In the last decades, they have been employed both as bioremediation agents for cleaning polluted sites and as bioconversion effectors for obtaining a variety of products from wastes (including eco-friendly plastics and green energies). However, some recent reports suggest that bacterial biodiversity can be negatively affected by the present environmental crisis (global warming, soil desertification, and ocean acidification). This review analyzes the behaviors positively selected by evolution that render bacteria good models of sustainable practices (urgent in these times of climate change and scarcity of resources). Actually, bacteria display a tendency to optimize rather than maximize, to economize energy and building blocks (by using the same molecule for performing multiple functions), and to recycle and share metabolites, and these are winning strategies when dealing with sustainability. Furthermore, their ability to establish successful reciprocal relationships by means of anticipation, collective actions, and cooperation can also constitute an example highlighting how evolutionary selection favors behaviors that can be strategic to contain the present environmental crisis.

Insights on toxin genotyping, virulence, antibiogram profiling, biofilm formation and efficacy of disinfectants on biofilms of Clostridium perfringens isolated from poultry, animals and humans

AIMS

This study aimed to determine the toxin genotypes, virulence determinants and antibiogram of Clostridium perfringens isolated from poultry, animals and humans. Biofilm formation and the efficacy of disinfectants on C. perfringens biofilms were studied.

METHODS AND RESULTS

Thirty C. perfringens isolates (20 clinical and 10 from chicken carcasses) were genotyped by PCR and all isolates were genotype A (cpa+). The overall prevalence of cpe, cpb2, netB and tpeL virulence genes was 6·7, 56·7, 56·7 and 36·7% respectively. Twenty-one isolates (70%) were multidrug-resistant, 8 (26·7%) were extensive drug-resistant and one isolate (3·3%) was pan drug-resistant. The average multiple antibiotic resistance index was 0·7. Biofilms were produced by 63·3% of C. perfringens isolates and categorized as weak (36·7%), moderate (16·7%) and strong (10%). Sodium hypochlorite caused significant reduction in C. perfringens biofilms (P < 0·0001).

CONCLUSIONS

All C. perfringens strains in this study were type A, resistant to multiple antibiotics and most of them were biofilm producers. Sodium hypochlorite showed higher efficacy in reducing C. perfringens biofilms.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study reported the efficacy of disinfectants in reducing C. perfringens biofilms of economic and public health concern and recommends application on surfaces in farms, food processing plants and slaughterhouses.

Polymicrobial Biofilm Interaction Between Histophilus somni and Pasteurella multocida

Histophilus somni and Pasteurella multocida are two of multiple agents responsible for bovine respiratory disease (BRD) in cattle. Following respiratory infection of calves with H. somni, P. multocida may also be isolated from the lower respiratory tract. Because H. somni may form a biofilm during BRD, we sought to determine if P. multocida can co-exist with H. somni in a polymicrobial biofilm in vitro and in vivo. Interactions between the two species in the biofilm were characterized and quantified by fluorescence in situ hybridization (FISH). The biofilm matrix of each species was examined using fluorescently tagged lectins (FTL) specific for the exopolysaccharide (EPS) using confocal laser scanning microscopy. Bacterial interactions were determined by auto-aggregation and biofilm morphology. Pasteurella multocida and H. somni were evenly distributed in the in vitro biofilm, and both species contributed to the polymicrobial biofilm matrix. The average biomass and biofilm thickness, and the total carbohydrate and protein content of the biofilm, were greatest when both species were present. Polymicrobial bacterial suspensions auto-aggregated faster than single species suspensions, suggesting physical interactions between the two species. Almost 300 P. multocida genes were significantly differentially regulated when the bacteria were in a polymicrobial biofilm compared to a mono-species biofilm, as determined by RNA-sequencing. As expected, host genes associated with inflammation and immune response were significantly upregulated at the infection site following H. somni challenge. Encapsulated P. multocida isolates not capable of forming a substantial biofilm enhanced an in vitro polymicrobial biofilm with H. somni, indicating they contributed to the polymicrobial biofilm matrix. Indirect evidence indicated that encapsulated P. multocida also contributed to a polymicrobial biofilm in vivo. Only the EPS of H. somni could be detected by FTL staining of bovine tissues following challenge with H. somni. However, both species were isolated and an immune response to the biofilm matrix of both species was greater than the response to planktonic cells, suggesting encapsulated P. multocida may take advantage of the H. somni biofilm to persist in the host during chronic BRD. These results may have important implications for the management and prevention of BRD.

Discovery and characterization of a Gram-positive Pel polysaccharide biosynthetic gene cluster

Our understanding of the biofilm matrix components utilized by Gram-positive bacteria, and the signalling pathways that regulate their production are largely unknown. In a companion study, we developed a computational pipeline for the unbiased identification of homologous bacterial operons and applied this algorithm to the analysis of synthase-dependent exopolysaccharide biosynthetic systems. Here, we explore the finding that many species of Gram-positive bacteria have operons with similarity to the Pseudomonas aeruginosa pel locus. Our characterization of the pelDEADAFG operon from Bacillus cereus ATCC 10987, presented herein, demonstrates that this locus is required for biofilm formation and produces a polysaccharide structurally similar to Pel. We show that the degenerate GGDEF domain of the B. cereus PelD ortholog binds cyclic-3',5'-dimeric guanosine monophosphate (c-di-GMP), and that this binding is required for biofilm formation. Finally, we identify a diguanylate cyclase, CdgF, and a c-di-GMP phosphodiesterase, CdgE, that reciprocally regulate the production of Pel. The discovery of this novel c-di-GMP regulatory circuit significantly contributes to our limited understanding of c-di-GMP signalling in Gram-positive organisms. Furthermore, conservation of the core pelDEADAFG locus amongst many species of bacilli, clostridia, streptococci, and actinobacteria suggests that Pel may be a common biofilm matrix component in many Gram-positive bacteria.

Antimicrobial activity of propolis extract fractions against Staphylococcus spp. isolated from goat mastitis

ABSTRACT: The indiscriminate use of antibiotics in the treatment of caprine mastitis causes the appearance of resistant microorganisms, besides leaving residues in milk, putting at risk to human health. In this way, propolis is an alternative in the treatment of diseases because it has antimicrobial activity, mainly because of the presence of flavonoids in its composition. The aim of this study was to evaluate the antimicrobial potential of propolis to Staphylococcus spp. Isolated from cases of goat mastitis and qualify the crude ethanoic extract by high performance liquid chromatography (HPLC). In this study, the minimum bactericidal concentration values of propolis extracts in ethanol, ethyl acetate and hexane showed that the best concentrations capable of promoting the highest mortality of the isolates of Staphylococcus spp. from mastitis in goats, were 6250, 3125 and 1562.5μg/mL, respectively. By the microplate adherence test, it was found that 20.78% isolates were not able to form biofilm, 14.70% were classified as moderate and 64.70% were weak and none as a strong biofilm producer. Propolis in its different diluents was able to affect the formation of biofilm and showed a pronounced marked antimicrobial activity against Staphylococcus spp. strains and may be indicated for use in in vivo studies.

Influence of some parameters on the ability of Listeria monocytogenes, Listeria innocua, and Escherichia coli to form biofilms

AIM

The present study was conducted to evaluate the capacity of Listeria monocytogenes (L.m), Listeria innocua (L.i), and Escherichia coli to form biofilms on polystyrene support under different parameters by performing crystal violet (CV) staining technique.

MATERIALS AND METHODS

Different suspensions were prepared with single strains and with multiple combinations of strains including two serogroups of L.m (IIa and IIb), L.i, and E. coli strains at different microbial load. Selected strains and combinations were grown in biofilms for 6 days attached to polystyrene microplates under aerobic and microaerophilic conditions. The evaluation of the power of adhesion and biofilm formation was determined by CV staining followed by the measurement of optical density at 24 h, 72 h, and 6 days incubation time with and without renewal of the culture medium.

RESULTS

All the strains tested, presented more or less adhesion power depending on the variation of the studied parameters as well as the ability to form multispecies biofilms. Their development is more important by renewing the culture medium and increasing the initial load of bacteria. The ability to adhere and form biofilms differs from one serogroup to another within the same species. In bacterial combination, strains and species of bacteria adopt different behaviors.

CONCLUSION

The ability to form biofilms is a key factor in the persistence of tested strains in the environment. Our study showed that L.m, L.i, and E. coli could adhere to polystyrene and form biofilms under different conditions. More researches are necessary to understand the mechanisms of biofilm formation and the influence of different parameters in their development.

New in vitro model evaluating antiseptics' efficacy in biofilm-associated Staphylococcus aureus prosthetic vascular graft infection

PURPOSE

To develop a new in vitro model of prosthetic vascular graft infection (PVGI) and evaluate antimicrobial and biofilm-disrupting efficacy of 0.1% octenidine dihydrochloride, 10% povidone-iodine and 0.02% chlorhexidine digluconate against biofilm-producing Staphylococcus aureus (S. aureus).

METHODOLOGY

The effect of antiseptics on the microscopic integrity and antimicrobial effect on S. aureus biofilms was tested by growing biofilms on glass coverslips, in the modified Lubbock chronic wound pathogenic biofilm (LCWPB) model and on the surface of vascular grafts using qualitive and quantitative methods as well as by scanning electron microscopy (SEM).

RESULTS

Chlorhexidine worked best on destroying the integrity of S. aureus biofilms (P=0.002). In the LCWPB model, octenidine and povidone-iodine eradicated all S. aureus colonies (from 1.79 × 10⁹  c.f.u. ml^-1 to 0). In the newly developed PVGI model, the grafts were successfully colonized with biofilms as seen in SEM images. All antiseptics demonstrated significant antimicrobial efficacy, decreasing colony counts by seven orders of magnitude (P=0.002). Octenidine was superior to povidone-iodine (P=0.009) and chlorhexidine (P=0.041).

CONCLUSION

We implemented an innovative in vitro model on S. aureus biofilms grown in different settings, including a clinically challenging situation of PVGI. The strongest antimicrobial activity against S. aureus biofilms, grown on prosthetic vascular grafts, was showed by 0.1% octenidine dihydrochloride. We suggest that combinational therapy of antiseptics between chlorhexidine with either povidone-iodine or octenidine dihydrochloride should be tested in further experiments. Despite the need of further studies, our findings of these in vitro experiments will assist the management of vascular graft infection in clinical cases.

MINIMUM BACTERICIDAL CONCENTRATION OF COMMERCIAL DISINFECTANTS ON STAPHYLOCOCCUS SPP. ISOLATED FROM MASTITIS IN GOATS AND DETECTION OF THE icaD GENE

Abstract This study aimed to evaluate the in vitro efficacy of commercial disinfectants on Staphylococcus spp., isolated from mastitis cases in goats, and to associate the observed resistance with the presence of the icaD gene. Broth microdilution was employed to evaluate the in vitro antimicrobial activity of the disinfectants, whereas the Congo Red technique was used for the evaluation of biofilm production and amplification of the icaD gene. All evaluated samples were sensitive to disinfectants, with the following ranges of activity: quaternary ammonium (0.13 - 21.33 µg/ml), chlorhexidine (4.00 - 313.00 µg/ml) and iodine (190.00 - 12500.00 µg/ml); however, the sodium hypochlorite-based disinfectant showed no bactericidal activity in the concentration range from 15.0 to 0.03 µg/ml. The icaD gene presented a frequency of 14.7% in the isolate samples. Fisher’s exact test showed a significant effect of the relation between the minimum bactericidal concentration value of the quaternary ammonium-based disinfectant and the presence/absence of the icaD gene (P <0.01). Commercial disinfectants with quaternary ammonium, chlorhexidine and iodine active ingredients presented in vitro activity even at concentrations lower than those recommended by the manufacturers. Therefore, the periodic evaluation of the sensitivity profile of the disinfectants must be performed.

Influência do polipirrol e dos níveis de salinidade na formação de biofilme em Aeromonas spp

RESUMO: Bactérias do gênero Aeromonas são patógenos altamente disseminados no ambiente aquático, responsáveis por grandes perdas econômicas na piscicultura de diversos países. São micro-organismos oportunistas e sua patogenicidade está ligada a alguns fatores de virulência, como a formação de biofilme. O estresse salino é um dos fatores que favorecem a formação dessas colônias e, consequentemente, o aumento de infecções. Essas infecções quando estão associadas ao biofilme são ainda mais resistentes aos antimicrobianos. Nesse contexto, o polipirrol destaca-se como uma alternativa antimicrobiana por possuir vários atributos terapêuticos e não apresentar toxicidade aos organismos. Dessa forma, o objetivo desse estudo foi avaliar o perfil de susceptibilidade e a capacidade de formação de biofilme dos isolados de Aeromonas spp. associados aos diferentes níveis de salinidade e polipirrol. Determinou-se a atividade antibacteriana dos isolados e ensaios de motilidade foram realizados com bactérias que carreavam o gene fla. Também verificou-se a capacidade do cloreto de sódio e polipirrol em interferir na formação do biofilme. Os resultados foram evidenciados com a microscopia eletrônica de varredura. As concentrações de 2 e 3% de NaCl inibiram a motilidade bacteriana. Na formação do biofilme, 83% dos isolados bacterianos induziram a produção na concentração de 0,25%. O polipirrol causou a morte de todos os isolados testados na concentração de 125μg/mL. Além disso, esse composto diminuiu a motilidade bacteriana nas concentrações de 0,25 a 3%, sendo que em relação à produção de biofilme, não houve interferência. Esses resultados evidenciam que os diferentes níveis de NaCl influenciam na formação do biofilme favorecendo a persistência da infecção. Este estudo também realçou a potencialidade do polipirrol como agente bactericida, sendo uma alternativa eficaz às drogas antimicrobianas para o tratamento das infecções causadas por Aeromonas spp.

Atividade antimicrobiana e antibiofilme de nanopartículas de prata sobre isolados de Aeromonas spp. obtidos de organismos aquáticos

RESUMO: O uso indiscriminado de antimicrobianos tem proporcionado a algumas bactérias patogênicas a seleção de cepas multirresistentes, situação que pode ser agravada pela formação do biofilme. Desta forma, as nanopartículas de prata (AgNPs) vêm se destacando como uma alternativa inovadora, de baixo custo e eficiente contra doenças causadas por bactérias. O objetivo deste estudo foi determinar a atividade antimicrobiana das AgNPs e a interferência na formação do biofilme de Aeromonas spp. obtidas de organismos aquáticos. As AgNPs foram sintetizadas quimicamente utilizando como agente redutor o citrato trissódico e caracterizadas por espectrofotometria ultravioleta-visível (UV-Vis). A atividade antimicrobiana foi realizada contra três isolados pelo método de microdiluição em caldo para determinar a concentração bactericida mínima (CBM) e um cultivo com CCCP, um inibidor da bomba de efluxo, foi realizado para complementar o efeito das AgNPs. A interferência no biofilme foi realizada segundo o protocolo de formação e consolidado, além da caracterização desta estrutura de resistência por microscopia eletrônica de varredura. No teste da CBM, as AgNPs não foram capazes de inativar o crescimento dos isolados, ao passo que o nitrato de prata obteve eficiência em diferentes concentrações. Na presença do inibidor de bomba de efluxo, dos isolados analisados, um passou de resistente a sensível na presença das nanopartículas. As AgNPs foram eficazes em diminuir a formação de biofilme, como também atuaram sobre o biofilme consolidado em todos os isolados testados. Estes resultados indicam o potencial das nanopartículas de prata em interferir com o biofilme de Aeromonas spp. de organismos aquáticos e seres humanos.

Evaluation of the biofilm formation capacity of Pasteurella multocida strains isolated from cases of fowl cholera and swine lungs and its relationship with pathogenicity

ABSTRACT: Pasteurella multocida is a Gram-negative bacillus that causes economic losses due to the development of respiratory diseases in several animal species. Among the mechanisms of virulence, the formation of biofilms is an important factor for bacterial survival in hostile environments. Studies of biofilm formation by P. multocida are needed because P. multocida is an important pathogen involved in respiratory infections. However, in contrast to other microorganisms, few studies of biofilm formation have examined P. multocida. Studies comparing the pathogenicity of microbial strains as a function of their biofilm production capacity are also rare. Consequently, the aim of this study was to evaluate the biofilm formation capacity of 94 P. multocida strains isolated from cases of fowl cholera and from swine lungs on polystyrene plates. The associations of the biofilm formation capacity with the pathogenicity index (PI) in vivo and with the presence of four genes (screened by PCR) of the tad locus (tadB, tadD, tadE and tadG), described as adhesion markers, were also determined. Strains from both animal origins were able to form biofilms. However, most of the specimens (52.13%) were classified as weak producers, and more than 40% of the strains of P. multocida (40.42%) did not produce biofilms. There was no significant difference (p>0.05) in the degree of biofilm production between the two sources of isolation. Of the analyzed strains, 56.52% contained all four genes (tadB, tadD, tadE and tadG). The PI arithmetic mean of the strains classified as non-biofilm producers was significantly different (p<0.05) from the PI of moderate-producer strains. The PI of specimens classified as weak biofilm producers also differed significantly (p<0.05) from that of the moderate-producer strains. The results indicate that even though the P. multocida strains isolated from cases of fowl cholera and swine lungs formed biofilms on polystyrene surfaces, adhesion was usually weak. The genes tadB, tadD, tadE and tadG were not significantly associated (p>0.05) with the production of biofilms and with the origin of a given strain. Finally, low virulence strains may suggest a higher biofilm formation capacity on polystyrene plates.

Endometritis: Diagnostic Tools for Infectious Endometritis

Infectious endometritis is among the leading causes of subfertility in the mare. However, the best way to reliably diagnose these cases of infectious endometritis can be confusing to the veterinary practitioner. The goal of this article is to describe how to perform various sample collection techniques, what analyses can be performed on these samples, and how to interpret the results of these analysis. Additionally, future technologies will be presented that are not currently used in equine reproduction practice.

Evaluation of the Impact of Methicillin-Resistant Staphylococcus pseudintermedius Biofilm Formation on Antimicrobial Susceptibility

OBJECTIVE

To compare the minimum inhibitory concentration (MIC) of four antimicrobials in planktonic vs. biofilm-associated Staphylococcus pseudintermedius.

STUDY DESIGN

In vitro study.

SAMPLE POPULATION

78 isolates from dogs colonized or infected with methicillin-resistant S. pseudintermedius (MRSP, n=39) or methicillin-susceptible S. pseudintermedius (MSSP, n=39).

METHODS

Agar dilution was used to determine the MIC of amikacin, cefazolin, enrofloxacin, and gentamicin for planktonic bacteria. A modified broth microdilution assay was used to assess the MIC of biofilm-associated bacteria.

RESULTS

MIC were significantly higher in biofilm-associated vs. planktonic bacteria for all antimicrobials; amikacin (median MIC: biofilm >2,000 μg/mL vs. planktonic 3 μg/mL, P<.0001), cefazolin (>1,000 vs. 0.5 μg/mL, P<.0001), enrofloxacin (>1,000 vs. 0.25 μg/mL, P<.0001), and gentamicin (>1,000 vs. 0.3 μg/mL, P<.001). For all antimicrobials, there were significant differences in planktonic MIC for MRSP and MSSP (all P<.0001) but no differences between biofilm MIC for MRSP and MSSP (P=.08-1.0).

CONCLUSION

The MIC for biofilm-associated S. pseudintermedius are significantly higher than for planktonic bacteria. Standard methods for determining MIC are not appropriate for biofilm-associated infections. This must be considered when determining treatment regimens for infections that potentially involve biofilms, and further study of methods to control biofilm-associated infections is needed.

Impact of Actinobacillus pleuropneumoniae biofilm mode of growth on the lipid A structures and stimulation of immune cells

Actinobacillus pleuropneumoniae (APP), the etiologic agent of porcine pleuropneumonia, forms biofilms on biotic and abiotic surfaces. APP biofilms confers resistance to antibiotics. To our knowledge, no studies have examined the role of APP biofilm in immune evasion and infection persistence. This study was undertaken to (i) investigate biofilm-associated LPS modifications occurring during the switch to biofilm mode of growth; and (ii) characterize pro-inflammatory cytokines expression in porcine pulmonary alveolar macrophages (PAMs) and proliferation in porcine PBMCs challenged with planktonic or biofilm APP cells. Extracted lipid A samples from biofilm and planktonic cultures were analyzed by HPLC high-resolution, accurate mass spectrometry. Biofilm cells displayed significant changes in lipid A profiles when compared with their planktonic counterparts. Furthermore, in vitro experiments were conducted to examine the inflammatory response of PAMs exposed to UV-inactivated APP grown in biofilm or in suspension. Relative mRNA expression of pro-inflammatory genes IL1, IL6, IL8 and MCP1 decreased in PAMs when exposed to biofilm cells compared to planktonic cells. Additionally, the biofilm state reduced PBMCs proliferation. Taken together, APP biofilm cells show a weaker ability to stimulate innate immune cells, which could be due, in part, to lipid A structure modifications.

The pulsed light inactivation of veterinary relevant microbial biofilms and the use of a RTPCR assay to detect parasite species within biofilm structures

The presence of pathogenic organisms namely parasite species and bacteria in biofilms in veterinary settings, is a public health concern in relation to human and animal exposure. Veterinary clinics represent a significant risk factor for the transfer of pathogens from housed animals to humans, especially in cases of wound infection and the shedding of faecal matter. This study aims to provide a means of detecting veterinary relevant parasite species in bacterial biofilms, and to provide a means of disinfecting these biofilms. A real time PCR assay was utilized to detect parasite DNA in Bacillus cereus biofilms on stainless steel and PVC surfaces. Results show that both Cryptosporidium and Giardia attach to biofilms in large numbers (100-1000 oo/cysts) in as little as 72 hours. Pulsed light successfully inactivated all test species (Listeria, Salmonella, Bacillus, Escherichia) in planktonic and biofilm form with an increase in inactivation for every increase in UV dose.

Characterization of Biofilm Formation in [Pasteurella] pneumotropica and [Actinobacillus] muris Isolates of Mouse Origin

[Pasteurella] pneumotropica biotypes Jawetz and Heyl and [Actinobacillus] muris are the most prevalent Pasteurellaceae species isolated from laboratory mouse. However, mechanisms contributing to their high prevalence such as the ability to form biofilms have not been studied yet. In the present investigation we analyze if these bacterial species can produce biofilms in vitro and investigate whether proteins, extracellular DNA and polysaccharides are involved in the biofilm formation and structure by inhibition and dispersal assays using proteinase K, DNase I and sodium periodate. Finally, the capacity of the biofilms to confer resistance to antibiotics is examined. We demonstrate that both [P.] pneumotropica biotypes but not [A.] muris are able to form robust biofilms in vitro, a phenotype which is widely spread among the field isolates. The biofilm inhibition and dispersal assays by proteinase and DNase lead to a strong inhibition in biofilm formation when added at the initiation of the biofilm formation and dispersed pre-formed [P.] pneumotropica biofilms, revealing thus that proteins and extracellular DNA are essential in biofilm formation and structure. Sodium periodate inhibited the bacterial growth when added at the beginning of the biofilm formation assay, making difficult the assessment of the role of β-1,6-linked polysaccharides in the biofilm formation, and had a biofilm stimulating effect when added on pre-established mature biofilms of [P.] pneumotropica biotype Heyl and a majority of [P.] pneumotropica biotype Jawetz strains, suggesting that the presence of β-1,6-linked polysaccharides on the bacterial surface might attenuate the biofilm production. Conversely, no effect or a decrease in the biofilm quantity was observed by biofilm dispersal using sodium periodate on further biotype Jawetz isolates, suggesting that polysaccharides might be incorporated in the biofilm structure. We additionally show that [P.] pneumotropica cells enclosed in biofilms were less sensitive to treatment with amoxicillin and enrofloxacin than planktonic bacteria. Taken together, these findings provide a first step in understanding of the biofilm mechanisms in [P.] pneumotropica, which might contribute to elucidation of colonization and pathogenesis mechanisms for these obligate inhabitants of the mouse mucosa.

Sub-inhibitory concentrations of penicillin G induce biofilm formation by field isolates of Actinobacillus pleuropneumoniae

Actinobacillus pleuropneumoniae is a Gram-negative bacterium and causative agent of porcine pleuropneumonia. This is a highly contagious disease that causes important economic losses to the swine industry worldwide. Penicillins are extensively used in swine production and these antibiotics are associated with high systemic clearance and low oral bioavailability. This may expose A. pleuropneumoniae to sub-inhibitory concentrations of penicillin G when the antibiotic is administered orally. Our goal was to evaluate the effect of sub-minimum inhibitory concentration (MIC) of penicillin G on the biofilm formation of A. pleuropneumoniae. Biofilm production of 13 field isolates from serotypes 1, 5a, 7 and 15 was tested in the presence of sub-MIC of penicillin G using a polystyrene microtiter plate assay. Using microscopy techniques and enzymatic digestion, biofilm architecture and composition were also characterized after exposure to sub-MIC of penicillin G. Sub-MIC of penicillin G significantly induced biofilm formation of nine isolates. The penicillin G-induced biofilms contained more poly-N-acetyl-D-glucosamine (PGA), extracellular DNA and proteins when compared to control biofilms grown without penicillin G. Additionally, penicillin G-induced biofilms were sensitive to DNase which was not observed with the untreated controls. Furthermore, sub-MIC of penicillin G up-regulated the expression of pgaA, which encodes a protein involved in PGA synthesis, and the genes encoding the envelope-stress sensing two-component regulatory system CpxRA. In conclusion, sub-MICs of penicillin G significantly induce biofilm formation and this is likely the result of a cell envelope stress sensed by the CpxRA system resulting in an increased production of PGA and other matrix components.

Musculoskeletal Pathology

The current understanding of pathology as it relates to common diseases of the equine musculoskeletal system is reviewed. Conditions are organized under the fundamental categories of developmental, exercise-induced, infectious, and miscellaneous pathology. The overview of developmental pathology incorporates the new classification system of juvenile osteochondral conditions. Discussion of exercise-induced pathology emphasizes increased understanding of the contribution of cumulative microdamage caused by repetitive cyclic loading. Miscellaneous musculoskeletal pathology focuses on laminitis, which current knowledge indicates should be regarded as a clinical syndrome with a variety of possible distinct mechanisms of structural failure that are outlined in this overview.

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.

Antimicrobial considerations in the perioperative patient

Surgical site infections are among the complications that can be reduced with the timely implementation of appropriate antimicrobial therapy. A 3-D approach to judicious antimicrobial use focuses on the de-escalation of systemic antimicrobial therapy, design of dosing regimens, and decontamination of the surgeon, patient, and environment. De-escalation can be accomplished in part through proper antimicrobial prophylaxis. Dosing regimens should be designed to maximize efficacy and minimize resistance. Decontamination includes disinfection of inanimate surfaces and timely application of appropriate antiseptics at concentrations that maximize efficacy.

Comparative studies of the immunogenicity and protective potential of biofilm vs planktonic Staphylococcus aureus vaccine against bovine mastitis using non-invasive mouse mastitis as a model system

This study was undertaken to compare the immunogenicity and protective potential of biofilm vs planktonic Staphylococcus aureus vaccine for the prevention of mastitis using the mouse as a model system. Mice immunized with formalin-killed whole cell vaccine of S. aureus residing in a biofilm when delivered via an intramammary route produced a cell mediated immune response. Mice immunized with this biofilm vaccine showed significant reductions in colonization by S. aureus in mammary glands, severity of clinical symptoms and tissue damage in mammary glands in comparison with the mice immunized with formalin-killed whole cells of planktonic S. aureus. The planktonic vaccine administered by a subcutaneous route produced a significantly higher humoral immune response (IgG1 and IgG) than the biofilm vaccine. However, considering the host response, tissue damage, the clinical severity and colonization of S. aureus in mammary glands, the biofilm vaccine performed better in immunogenicity and protective potential when administered by the intramammary route.

Paracentrin 1, a synthetic antimicrobial peptide from the sea-urchin Paracentrotus lividus, interferes with staphylococcal and Pseudomonas aeruginosa biofilm formation

The rise of antibiotic-resistance as well as the reduction of investments by pharmaceutical companies in the development of new antibiotics have stimulated the investigation for alternative strategies to conventional antibiotics. Many antimicrobial peptides show a high specificity for prokaryotes and a low toxicity for eukaryotic cells and, due to their mode of action the development of resistance is considered unlikely. We recently characterized an antimicrobial peptide that was called Paracentrin 1 from the 5-kDa peptide fraction from the coelomocyte cytosol of the Paracentrotus lividus. In this study, the chemically synthesized Paracentrin 1, was tested for its antimicrobial and antibiofilm properties against reference strains of Gram positive and Gram negative. The Paracentrin 1 was active against planktonic form of staphylococcal strains (reference and isolates) and Pseudomonas aeruginosa ATCC 15442 at concentrations ranging from 12.5 to 6.2 mg/ml. The Paracentrin 1 was able to inhibit biofilm formation of staphylococcal and Pseudomonas aeruginosa strains at concentrations ranging from 3.1 to 0.75 mg/ml. We consider the tested peptide as a good starting molecule for novel synthetic derivatives with improved pharmaceutical potential.

Virulence factors and biofilm production by isolates of Bacteroides fragilis recovered from dog intestinal tracts

Bacteroides fragilis colonizes dog guts both as a commensal and as an opportunistic pathogen. This study aims to evaluate virulence factors of 13 B. fragilis strains isolated from dog intestinal tracts and their ability for biofilm formation. Capsules were detected in all the evaluated strains. A total of 61.5% of all strains were biofilm producers. These attributes most likely play an important role in B. fragilis persistent colonization in the gut.

TolC promotes ExPEC biofilm formation and curli production in response to medium osmolarity

While a high osmolarity medium activates Cpx signaling and causes CpxR to repress csgD expression, and efflux protein TolC protein plays an important role in biofilm formation in Escherichia coli, whether TolC also responds to an osmolarity change to regulate biofilm formation in extraintestinal pathogenic E. coli (ExPEC) remains unknown. In this study, we constructed ΔtolC mutant and complement ExPEC strains to investigate the role of TolC in the retention of biofilm formation and curli production capability under different osmotic conditions. The ΔtolC mutant showed significantly decreased biofilm formation and lost the ability to produce curli fimbriae compared to its parent ExPEC strain PPECC42 when cultured in M9 medium or 1/2 M9 medium of increased osmolarity with NaCl or sucrose at 28°C. However, biofilm formation and curli production levels were restored to wild-type levels in the ΔtolC mutant in 1/2 M9 medium. We propose for the first time that TolC protein is able to form biofilm even under high osmotic stress. Our findings reveal an interplay between the role of TolC in ExPEC biofilm formation and the osmolarity of the surrounding environment, thus providing guidance for the development of a treatment for ExPEC biofilm formation.

Invited review: effect, persistence, and virulence of coagulase-negative Staphylococcus species associated with ruminant udder health

The aim of this review is to assess the effect of coagulase-negative staphylococci (CNS) species on udder health and milk yield in ruminants, and to evaluate the capacity of CNS to cause persistent intramammary infections (IMI). Furthermore, the literature on factors suspected of playing a role in the pathogenicity of IMI-associated CNS, such as biofilm formation and the presence of various putative virulence genes, is discussed. The focus is on the 5 CNS species that have been most frequently identified as causing bovine IMI using reliable molecular identification methods (Staphylococcus chromogenes, Staphylococcus simulans, Staphylococcus haemolyticus, Staphylococcus xylosus, and Staphylococcus epidermidis). Although the effect on somatic cell count and milk production is accepted to be generally limited or nonexistent for CNS as a group, indications are that the typical effects differ between CNS species and perhaps even strains. It has also become clear that many CNS species can cause persistent IMI, contrary to what has long been believed. However, this trait appears to be quite complicated, being partly strain dependent and partly dependent on the host's immunity. Consistent definitions of persistence and more uniform methods for testing this phenomenon will benefit future research. The factors explaining the anticipated differences in pathogenic behavior appear to be more difficult to evaluate. Biofilm formation and the presence of various staphylococcal virulence factors do not seem to (directly) influence the effect of CNS on IMI but the available information is indirect or insufficient to draw consistent conclusions. Future studies on the effect, persistence, and virulence of the different CNS species associated with IMI would benefit from using larger and perhaps even shared strain collections and from adjusting study designs to a common framework, as the large variation currently existing therein is a major problem. Also within-species variation should be investigated.