Clearance of Staphylococcus aureus from In Vivo Models of Chronic Infection by Immunization Requires Both Planktonic and Biofilm Antigens

Staphylococcus aureus is a causative agent of chronic biofilm-associated infections that are recalcitrant to resolution by the immune system or antibiotics. To combat these infections, an antistaphylococcal, biofilm-specific quadrivalent vaccine against an osteomyelitis model in rabbits has previously been developed and shown to be effective at eliminating biofilm-embedded bacterial populations. However, the addition of antibiotics was required to eradicate remaining planktonic populations. In this study, a planktonic upregulated antigen was combined with the quadrivalent vaccine to remove the need for antibiotic therapy. Immunization with this pentavalent vaccine followed by intraperitoneal challenge of BALB/c mice with S. aureus resulted in 16.7% and 91.7% mortality in pentavalent vaccine and control groups, respectively (P < 0.001). Complete bacterial elimination was found in 66.7% of the pentavalent cohort, while only 8.3% of the control animals cleared the infection (P < 0.05). Further protective efficacy was observed in immunized rabbits following intramedullary challenge with S. aureus, where 62.5% of the pentavalent cohort completely cleared the infection, versus none of the control animals (P < 0.05). Passive immunization of BALB/c mice with serum IgG against the vaccine antigens prior to intraperitoneal challenge with S. aureus prevented mortality in 100% of mice and eliminated bacteria in 33.3% of the challenged mice. These results demonstrate that targeting both the planktonic and biofilm stages with the pentavalent vaccine or the IgG elicited by immunization can effectively protect against S. aureus infection.

Topical therapy for refractory rhinosinusitis caused by methicillin-resistant Staphylococcus aureus: First report in a prospective series

OBJECTIVE

The incidence of refractory chronic rhinosinusitis (CRS) associated with methicillin-resistant Staphylococcus aureus (MRSA) is rising and remains a therapeutic challenge. The goal of this study is to demonstrate the efficacy of a non-invasive topical therapy against MRSA in these patients.

METHODS

Seventeen patients with refractory CRS caused by MRSA were treated with a topical therapy protocol. Treatment consisted of weekly endoscopic sinus debridement followed by intra-sinus installation of a hydroxyl-ethylcellulose gel that releases mometasone and a culture-directed antibiotic for a period of 6 weeks, along with daily nasal nebulization of mometasone with the same antibiotic and saline rinses. Clinical outcome was assessed using the Lund-Kennedy (LK) symptom and endoscopic appearance scores. Sinus mucosal tissue was homogenized and cultured, and microbial biofilm burden was assessed based on colony forming units (CFUs) counts.

RESULTS

Rhinotopic therapy resulted in clearance of MRSA in 13 of 16 patients (81.2%). Treated patients also demonstrated significant improvement clinically as measured by the LK scores. In addition, a significant decrease in mucosal CFUs was observed post-therapy.

CONCLUSION

Our findings demonstrate that topical therapy is an effective method for treating MRSA-associated refractory CRS.

Mucosal expression of aquaporin 5 and epithelial barrier proteins in chronic rhinosinusitis with and without nasal polyps

OBJECTIVES

The purpose of this study is to characterize the association between altered epithelial barrier function, represented by changes in histology and differential expression of the mucosal water membrane permeability protein aquaporin 5 (AQP5), and the pathophysiology of chronic refractory sinusitis (CRS) in patients with and without nasal polyposis.

STUDY DESIGN

Prospective clinical study.

SETTING

Tertiary rhinology referral center.

PARTICIPANTS

Sinonasal samples were obtained from seven CRS subjects with nasal polyps (CRSwNP), seven CRS without nasal polyposis (CRSsNP), and five control healthy patients.

METHODS

Mucosal membrane changes were evaluated through hematoxylin and eosin staining of the membrane barrier and immunohistochemical staining of AQP5 expression, a membrane channel protein that affects trans-epithelial water permeability and tissue edema. AQP5 expression was confirmed by real-time PCR (rt-PCR) and western blot. Levels of other membrane proteins, including E-cadherin and Septin-2, were also assessed.

RESULTS

CRSwNP patients showed substantial histologic evidence of membrane remodeling with increased edema and glandular hyperplasia. The epithelial expression of AQP5 was significantly lower in CRSwNP as compared to CRSsNP or control. There was no significant difference in the expression of E-cadherin and Septin-2.

CONCLUSIONS

Collectively, these data suggest that the mucosal epithelial barrier is compromised in the context of CRS (predominantly in CRSwNP) when compared to control and that AQP5 acts as a key tight junction protein in the maintenance of mucosal water homeostasis. We hypothesize that AQP5 plays a possible role in the pathophysiology of mucosal edema and polyp formation.

Mycobacterium tuberculosis pellicles express unique proteins recognized by the host humoral response

Mycobacterium tuberculosis (MTB) causes both acute and chronic infections in humans characterized by tolerance to antibiotics and reactivation to cause secondary tuberculosis. These characteristics have led to renewed interest in the in vitro pellicle, or biofilm mode of growth, where bacteria grow to produce a thick aggregate at the air-liquid interface and exhibit increased phenotypic resistance to antibiotics. We infected guinea pigs with the virulent H37Rv strain of MTB for 60 days at which point we collected blood. To identify antigenic proteins, membrane protein extracts of MTB H37Ra pellicles and shaken cultures grown for 3, 5, or 7 weeks were probed with the infected animals' sera after the proteins were separated by two-dimensional gel electrophoresis (2DGE). Antigenic proteins were then identified using MALDI-TOF/TOF mass spectrometry peptide mass fingerprinting. Antigenic pellicle proteins were compared across the three timepoints to identify those that were produced consistently during pellicle growth. They were also compared to those membrane proteins identified from harvested shaken cultures to determine pellicle-specific vs. universally expressed proteins. Using this technique, we identified 44 distinct antigenic proteins, nine of which were pellicle-specific. The sequence of antigenic pellicle-specific proteins was checked for sequence conservation across 15 sequenced MTB clinical isolates, three other members of the MTB complex, as well as M. avium and M. smegmatis. The antigenic pellicle-specific protein Rv0097 was found to have very high sequence conservation within the MTB complex but not with related mycobacteria, while FabG4 was highly conserved in all mycobacteria analyzed. These conserved pellicle-specific proteins represent targets for the development of future diagnostic tests and vaccines.

Expression of antimicrobial drug tolerance by attached communities of Mycobacterium tuberculosis

There is an urgent need to improve methods used to screen antituberculosis drugs. An in vitro assay was developed to test drug treatment strategies that specifically target drug-tolerant Mycobacterium tuberculosis. The H37Rv strain of M. tuberculosis survived antimicrobial treatment as attached microbial communities when maintained in tissue culture media (RPMI-1640) with or without lysed human peripheral blood leukocytes. When cultured planktonically in the presence of Tween-80, bacilli failed to form microbial communities or reach logarithmic phase growth yet remained highly susceptible to antimicrobial drugs. In the absence of Tween, bacilli tolerated drug therapy by forming complex microbial communities attached to untreated well surfaces or to the extracellular matrix derived from lysed human leukocytes. Treatment of microbial communities with DNase I or Tween effectively dispersed bacilli and restored drug susceptibility. These data demonstrate that in vitro expression of drug tolerance by M. tuberculosis is linked to the establishment of attached microbial communities and that dispersion of bacilli targeting the extracellular matrix including DNA restores drug susceptibility. Modifications of this in vitro assay may prove beneficial in a high-throughput platform to screen new antituberculosis drugs especially those that target drug-tolerant bacilli.

Modeling the response of a biofilm to silver-based antimicrobial

Biofilms are found within the lungs of patients with chronic pulmonary infections, in particular patients with cystic fibrosis, and are the major cause of morbidity and mortality for these patients. The work presented here is part of a large interdisciplinary effort to develop an effective drug delivery system and treatment strategy to kill biofilms growing in the lung. The treatment strategy exploits silver-based antimicrobials, in particular, silver carbene complexes (SCC). This manuscript presents a mathematical model describing the growth of a biofilm and predicts the response of a biofilm to several basic treatment strategies. The continuum model is composed of a set of reaction-diffusion equations for the transport of soluble components (nutrient and antimicrobial), coupled to a set of reaction-advection equations for the particulate components (living, inert, and persister bacteria, extracellular polymeric substance, and void). We explore the efficacy of delivering SCC both in an aqueous solution and in biodegradable polymer nanoparticles. Minimum bactericidal concentration (MBC) levels of antimicrobial in both free and nanoparticle-encapsulated forms are estimated. Antimicrobial treatment demonstrates a biphasic killing phenomenon, where the active bacterial population is killed quickly followed by a slower killing rate, which indicates the presence of a persister population. Finally, our results suggest that a biofilm with a ready supply of nutrient throughout its depth has fewer persister bacteria and hence may be easier to treat than one with less nutrient.

Topical gel therapy for sinonasal polyposis in Samter's triad: preliminary report

OBJECTIVES

Rhinosinusitis and polyposis are difficult to treat in patients with Samter's triad; they commonly recur despite sinus surgery, antibiotics, and/or nasal steroids. The present study assesses the efficacy of a multimodal regimen that includes topical corticosteroids and antibiotics delivered through a hydroxyethyl cellulose gel and by nebulization.

METHODS

Eleven patients with Samter's triad who had polyposis and rhinosinusitis that recurred despite endoscopic sinus surgery were treated with a 6-week course of multimodal topical therapy consisting of a hydroxyethyl cellulose gel that releases corticosteroids and antibiotics, topical nebulization of corticosteroids and antibiotics, saline solution rinses, and sinus debridement. Clinical outcomes were evaluated by Lund-Kennedy endoscopic and symptom scores. Histologic assessment was evaluated by hematoxylin and eosin staining before and after treatment.

RESULTS

Both Lund-Kennedy symptom and endoscopic scores showed.a progressive and statistically significant decline throughout the course of treatment, reaching at 6 weeks 42% of the pretreatment values (p = 0.005) for the Lund-Kennedy symptom score and 34% (p = 0.002) for the endoscopic score, respectively; however, the significance of the improvement was lost with time.

CONCLUSIONS

Topical gel therapy improves clinical symptoms, endoscopic findings, and sinus membrane histologic features in patients with refractory Samter's triad, but the improvement is transient, suggesting that a longer therapeutic period might be needed.

Regulation of murine sinonasal cilia function by microbial secreted factors

BACKGROUND

Chronic rhinosinusitis is a multifactorial disease resulting in impaired mucociliary clearance. Recent literature suggests that different bacterial species are associated with varied disease severity. We examined the immediate effect of microbial secreted factors on sinonasal ciliary function.

METHODS

Murine primary sinonasal cultures were established in an air-liquid interface (ALI). Bacterial supernatants were isolated from H. influenza, S. pneumoniae, S. aureus, and P. aeruginosa cultures, as well as co-cultures of H. influenza/S. pneumoniae and S. aureus/P. aeruginosa. Controlling for pH and osmolarity, supernatants were administered at 50% concentration to the apical surface of the ALI culture. Basal ciliary beat frequency (CBF) was recorded for 20 minutes, at 5-minute intervals. Control groups were treated with culture broth. At minimum, experiments were performed in triplicate. Stimulated CBF was recorded after mechanical stimulation via short bursts of pressurized air (55 mmHg).

RESULTS

All supernatants reduced basal CBF. S. pneumoniae and P. aeruginosa caused significant reduction in CBF at all time points, with the largest decrease of -46.3 ± 1.6% (p < 0.001) for S. pneumoniae and -27.1 ± 2.8% (p < 0.001) for P. aeruginosa. S. aureus caused the basal CBF to decline by -33.0 ± 2.8% (p < 0.001) at 5 minutes, which reversed by 20 minutes. Overall, H. influenza yielded the least change in CBF (-20.0 ± 2.8%, p < 0.002). Co-cultures (H. influenza/S. pneumoniae and S. aureus/P. aeruginosa) resulted in delayed CBF reduction compared with monocultures. P. aeruginosa also blunted stimulated CBF (p < 0.02).

CONCLUSION

Results demonstrated acute decreases in murine sinonasal CBF after exposure to bacterial supernatants. Moreover, P. aeruginosa resulted in diminished ciliary stimulation capacity.

Regulation of virulence gene expression resulting from Streptococcus pneumoniae and nontypeable Haemophilus influenzae interactions in chronic disease

Chronic rhinosinusitis (CRS) is a common inflammatory disease of the sinonasal cavity mediated, in part, by polymicrobial communities of bacteria. Recent molecular studies have confirmed the importance of Streptococcus pneumoniae and nontypeable Haemophilus influenzae (NTHi) in CRS. Here, we hypothesize that interaction between S. pneumoniae and NTHi mixed-species communities cause a change in bacterial virulence gene expression. We examined CRS as a model human disease to validate these polymicrobial interactions. Clinical strains of S. pneumoniae and NTHi were grown in mono- and co-culture in a standard biofilm assay. Reverse transcriptase real-time PCR (RTqPCR) was used to measure gene expression of key virulence factors. To validate these results, we investigated the presence of the bacterial RNA transcripts in excised human tissue from patients with CRS. Consequences of physical or chemical interactions between microbes were also investigated. Transcription of NTHi type IV pili was only expressed in co-culture in vitro, and expression could be detected ex vivo in diseased tissue. S. pneumoniae pyruvate oxidase was up-regulated in co-culture, while pneumolysin and pneumococcal adherence factor A were down-regulated. These results were confirmed in excised human CRS tissue. Gene expression was differentially regulated by physical contact and secreted factors. Overall, these data suggest that interactions between H. influenzae and S. pneumoniae involve physical and chemical mechanisms that influence virulence gene expression of mixed-species biofilm communities present in chronically diseased human tissue. These results extend previous studies of population-level virulence and provide novel insight into the importance of S. pneumoniae and NTHi in CRS.

In vitro antimicrobial studies of silver carbene complexes: activity of free and nanoparticle carbene formulations against clinical isolates of pathogenic bacteria

OBJECTIVES

Silver carbenes may represent novel, broad-spectrum antimicrobial agents that have low toxicity while providing varying chemistry for targeted applications. Here, the bactericidal activity of four silver carbene complexes (SCCs) with different formulations, including nanoparticles (NPs) and micelles, was tested against a panel of clinical strains of bacteria and fungi that are the causative agents of many skin and soft tissue, respiratory, wound, blood, and nosocomial infections.

METHODS

MIC, MBC and multidose experiments were conducted against a broad range of bacteria and fungi. Time-release and cytotoxicity studies of the compounds were also carried out. Free SCCs and SCC NPs were tested against a panel of medically important pathogens, including methicillin-resistant Staphylococcus aureus (MRSA), multidrug-resistant Acinetobacter baumannii (MRAB), Pseudomonas aeruginosa, Burkholderia cepacia and Klebsiella pneumoniae.

RESULTS

All four SCCs demonstrated strong efficacy in concentration ranges of 0.5-90 mg/L. Clinical bacterial isolates with high inherent resistance to purified compounds were more effectively treated either with an NP formulation of these compounds or by repeated dosing. Overall, the compounds were active against highly resistant bacterial strains, such as MRSA and MRAB, and were active against the biodefence pathogens Bacillus anthracis and Yersinia pestis. All of the medically important bacterial strains tested play a role in many different infectious diseases.

CONCLUSIONS

The four SCCs described here, including their development as NP therapies, show great promise for treating a wide variety of bacterial and fungal pathogens that are not easily killed by routine antimicrobial agents.

Staphylococcus aureus biofilms: properties, regulation, and roles in human disease

Increasing attention has been focused on understanding bacterial biofilms and this growth modality's relation to human disease. In this review we explore the genetic regulation and molecular components involved in biofilm formation and maturation in the context of the Gram-positive cocci, Staphylococcus aureus. In addition, we discuss diseases and host immune responses, along with current therapies associated with S. aureus biofilm infections and prevention strategies.

Management of Refractory Nasal Polyposis in Samter’s Triad

Objective: Rhinosinusitis and polyposis in Samter triad is difficult to treat, commonly recurring despite sinus surgery, antibiotics, and/or nasal steroids. Systemic steroids are limited by side effects. The present study assesses the efficacy of a gel placed into the sinuses, releasing steroids and antibiotics, along with topical nebulization of the same medications.

Method: Ten Samter patients with recurrent rhinosinusitis after sinus surgery received weekly intra-sinus placement of a hydroxycellulose gel-releasing mometasone and antibiotics, along with endoscopic sinus debridement, for 6 weeks. Outcome was evaluated by Lund-Kennedy (LK) endoscopic and symptom scales immediately, 3 weeks, 6 weeks, and 10 weeks after the beginning of the protocol.

Results: Both LK symptoms and endoscopic scores showed a progressive and statistically significant decline throughout the course of therapy, reaching at the end of treatment 56% ( P = .003) and 59% ( P = .004) improvement of pretreatment values, respectively. At 1 month posttreatment, mild relapse was noted.

Conclusion: A topical membrane therapy regimen consisting of gel-releasing corticosteroids and antibiotics, along with topically nebulized corticosteroids and antibiotics, regular saline hydrotherapy, and sinus debridement, improves symptoms and endoscopic findings in recurrent Samter sinonasal polyposis.

Microbial interactions and differential protein expression in Staphylococcus aureus -Candida albicans dual-species biofilms

The fungal species Candida albicans and the bacterial species Staphylococcus aureus are responsible for a majority of hospital-acquired infections and often coinfect critically ill patients as complicating polymicrobial biofilms. To investigate biofilm structure during polymicrobial growth, dual-species biofilms were imaged with confocal scanning laser microscopy. Analyses revealed a unique biofilm architecture where S. aureus commonly associated with the hyphal elements of C. albicans. This physical interaction may provide staphylococci with an invasion strategy because candidal hyphae can penetrate through epithelial layers. To further understand the molecular mechanisms possibly responsible for previously demonstrated amplified virulence during coinfection, protein expression studies were undertaken. Differential in-gel electrophoresis identified a total of 27 proteins to be significantly differentially produced by these organisms during coculture biofilm growth. Among the upregulated staphylococcal proteins was l-lactate dehydrogenase 1, which confers resistance to host-derived oxidative stressors. Among the downregulated proteins was the global transcriptional repressor of virulence factors, CodY. These findings demonstrate that the hyphae-mediated enhanced pathogenesis of S. aureus may not only be due to physical interactions but can also be attributed to the differential regulation of specific virulence factors induced during polymicrobial growth. Further characterization of the intricate interaction between these pathogens at the molecular level is warranted, as it may aid in the design of novel therapeutic strategies aimed at combating fungal–bacterial polymicrobial infection.

Biofilms in chronic rhinosinusitis: a review

BACKGROUND

Bacterial biofilms consist of a complex, organized community of bacteria that anchor to both biotic and abiotic surfaces. They are composed of layers of embedded, live bacteria within extruded exopolymeric matrix. This configuration allows for evasion of host defenses and decreased susceptibility to antibiotic therapy while maintaining the ability to deliberately release planktonic bacteria, resulting in recurrent acute infections. Thus, bacterial biofilms were hypothesized to contribute to the progression and persistence of chronic rhinosinusitis.

METHODS

This review summarizes several of the seminal papers supporting this hypothesis.

RESULTS

Multiple reports using various imaging modalities have demonstrated the presence of biofilms in sinonasal mucosa of patients with chronic rhinosinusitis. More recently, several studies have correlated the presence of biofilms with poor clinical outcomes in the disease process. Early therapeutic interventions have generated mixed results.

CONCLUSIONS

Bacterial biofilms appear to contribute to the progression of chronic rhinosinusitis in a subset of patients, although substantial effort toward therapeutic intervention is still necessary.

Synthesis and in vitro Efficacy Studies of Silver Carbene Complexes on Biosafety Level 3 Bacteria

A series of N-heterocyclic carbene silver complexes have been synthesized and tested against the select group of bio-safety level 3 bacteria Burkholderia pseudomallei, Burkholderia mallei, Bacillus anthracis, methicillin-resistant Staphylococcus aureus and Yersinia pestis. Minimal inhibitory concentrations, minimal bactericidal and killing assays demonstrated the exceptional efficacy of the complexes against these potentially weaponizable pathogens.

Biofilms with fungi in chronic rhinosinusitis

OBJECTIVES

Demonstrate that bacterial biofilm in sinus mucosal samples from patients with eosinophilic mucin chronic rhinosinusitis (EMCRS) and allergic fungal rhinosinusitis (AFRS) contains fungal elements; identify specific organisms in the biofilm.

METHODS

Mucosa samples from 11 patients undergoing sinus surgery were collected. Patients were classified as having AFRS, EMCRS, or chronic rhinosinusitis (CRS) based on histopathologic findings. Three mucosal samples from controls were also collected. Samples were stained with specific bacterial fluorescent in situ hybridization (FISH) DNA probes (Haemophilus influenzae, Streptococcus pneumophilia, Staphylococcus aureus, and Pseudomonas aeruginosa) and a general pan-fungal FISH probe. The samples were analyzed for bacterial biofilm ultrastructure and fungal elements using epifluorescent microscopy.

RESULTS

Bacterial biofilm was demonstrated in 9/11 samples and 2/3 controls. H. influenzae was the predominant biofilm present. There was a trend showing more fungal elements in AFRS and EMCRS biofilms than in CRS and controls.

CONCLUSION

This is a preliminary study demonstrating fungal elements within sinus mucosal biofilm and demonstrating biofilm in AFRS.

Osteomyelitis and the role of biofilms in chronic infection

Understanding the mechanisms implicated in the initial attachment, development, and maturation of a biofilm phenotype are of tremendous importance for their effect on the medical, industrial, and public health arenas. This review explores the current understanding of the nature of biofilms and the impact that molecular interactions between the bacteria themselves, as well as between bacteria and the host, may have on biofilm development and phenotype using the nonmotile Gram-positive coccus, Staphylococcus aureus, as an example.

Immunoglobulins to surface-associated biofilm immunogens provide a novel means of visualization of methicillin-resistant Staphylococcus aureus biofilms

Antigens from the methicillin-resistant Staphylococcus aureus (MRSA) cell wall have been shown to be immunogenic in vivo and upregulated during biofilm growth. In this study, we created purified, recombinant forms of selected antigens and biofilm-upregulated, cell wall-associated proteins. These proteins were shown to cause a robust polyclonal immunoglobulin G (IgG) response when used to immunize rabbits. Antibodies against these recombinant proteins bound to the native forms of each protein as harvested from in vitro grown biofilms of MRSA, as determined both via Western blot analysis and immunofluorescence confocal microscopy. These IgGs could be utilized as imaging tools that localize to areas of specific protein production within a biofilm. This work illustrates that immunogenic, cell wall-associated, biofilm-upregulated proteins are promising for in vitro visualization of biofilm growth, architecture, and space-function relationships.

Phenotypic and functional characterization of Bacillus anthracis biofilms

Biofilms, communities of micro-organisms attached to a surface, are responsible for many chronic diseases and are often associated with environmental reservoirs or lifestyles. Bacillus anthracis is a Gram-positive, endospore-forming bacterium and is the aetiological agent of pulmonary, gastrointestinal and cutaneous anthrax. Anthrax infections are part of the natural lifecycle of many ruminants in North America, including cattle and bison, and B. anthracis is thought to be a central part of this ecosystem. However, in endemic areas in which humans and livestock interact, chronic cases of cutaneous anthrax are commonly reported. This suggests that biofilms of B. anthracis exist in the environment and are part of the ecology associated with its lifecycle. Currently, there are few data that account for the importance of the biofilm mode of life in B. anthracis, yet biofilms have been characterized in other pathogenic and non-pathogenic Bacillus species, including Bacillus cereus and Bacillus subtilis, respectively. This study investigated the phenotypic and functional role of biofilms in B. anthracis. The results demonstrate that B. anthracis readily forms biofilms which are inherently resistant to commonly prescribed antibiotics, and that antibiotic resistance is not solely the function of sporulation.

Bacterial Biofilms on the Sinus Mucosa of Human Subjects With Chronic Rhinosinusitis

INTRODUCTION

Chronic rhinosinusitis (CRS) is a common disease poorly controlled by antibiotics. Postulated etiologies of CRS include allergy, fungi, functional factors, and biofilm.

OBJECTIVES

We presented a preliminary study demonstrating bacterial biofilms' presence on the sinus mucosa of patients with CRS using fluorescent in situ hybridization (FISH). The advantage of FISH in biofilm identification is that it is the only method that identifies the specific bacteria creating the biofilm matrix. We now present the results of a larger series of patients.

METHODS

Patients with CRS scheduled for sinus surgery were enrolled in the study. Biopsies of the sinus mucosa and cultures were taken at the time of surgery. Control samples were taken from patients undergoing septoplasty. Specimens underwent FISH testing for Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenza, and Pseudomonas aeruginosa.

RESULTS

Bacterial biofilms were present on 14 of 18 specimens. The predominant species were H. influenzae, S. pneumoniae, and S. aureus. P. aeruginosa biofilm was not identified on any specimens. The intraoperative cultures of the planktonic bacteria present in the sinuses did not correlate with the biofilms identified. Two of the five control samples were positive for biofilm.

CONCLUSION

The presence of biofilms on the mucosa of patients with CRS offers a possible cause of antimicrobial therapy failure and could change the approach to treatment. However, the presence of biofilms on healthy control samples implies that biofilms may simply be colonizers. The precise role that biofilms play in CRS still remains to be determined. Further studies with larger sample sizes are needed.

Identification of Staphylococcus aureus proteins recognized by the antibody-mediated immune response to a biofilm infection

Staphylococcus aureus causes persistent, recurrent infections (e.g., osteomyelitis) by forming biofilms. To survey the antibody-mediated immune response and identify those proteins that are immunogenic in an S. aureus biofilm infection, the tibias of rabbits were infected with methicillin-resistant S. aureus to produce chronic osteomyelitis. Sera were collected prior to infection and at 14, 28, and 42 days postinfection. The sera were used to perform Western blot assays on total protein from biofilm grown in vitro and separated by two-dimensional gel electrophoresis. Those proteins recognized by host antibodies in the harvested sera were identified via matrix-assisted laser desorption ionization-time of flight analysis. Using protein from mechanically disrupted total and fractionated biofilm protein samples, we identified 26 and 22 immunogens, respectively. These included a cell surface-associated beta-lactamase, lipoprotein, lipase, autolysin, and an ABC transporter lipoprotein. Studies were also performed using microarray analyses and confirmed the biofilm-specific up-regulation of most of these genes. Therefore, although the biofilm antigens are recognized by the immune system, the biofilm infection can persist. However, these proteins, when delivered as vaccines, may be important in directing the immune system toward an early and effective antibody-mediated response to prevent chronic S. aureus infections. Previous works have identified S. aureus proteins that are immunogenic during acute infections, such as sepsis. However, this is the first work to identify these immunogens during chronic S. aureus biofilm infections and to simultaneously show the global relationship between the antigens expressed during an in vivo infection and the corresponding in vitro transcriptomic and proteomic gene expression levels.

The exopolysaccharide alginate protects Pseudomonas aeruginosa biofilm bacteria from IFN-gamma-mediated macrophage killing

The ability of Pseudomonas aeruginosa to form biofilms and cause chronic infections in the lungs of cystic fibrosis patients is well documented. Numerous studies have revealed that P. aeruginosa biofilms are highly refractory to antibiotics. However, dramatically fewer studies have addressed P. aeruginosa biofilm resistance to the host's immune system. In planktonic, unattached (nonbiofilm) P. aeruginosa, the exopolysaccharide alginate provides protection against a variety of host factors yet the role of alginate in protection of biofilm bacteria is unclear. To address this issue, we tested wild-type strains PAO1, PA14, the mucoid cystic fibrosis isolate, FRD1 (mucA22+), and the respective isogenic mutants which lacked the ability to produce alginate, for their susceptibility to human leukocytes in the presence and absence of IFN-gamma. Human leukocytes, in the presence of recombinant human IFN-gamma, killed biofilm bacteria lacking alginate after a 4-h challenge at 37 degrees C. Bacterial killing was dependent on the presence of IFN-gamma. Killing of the alginate-negative biofilm bacteria was mediated through mononuclear cell phagocytosis since treatment with cytochalasin B, which prevents actin polymerization, inhibited leukocyte-specific bacterial killing. By direct microscopic observation, phagocytosis of alginate-negative biofilm bacteria was significantly increased in the presence of IFN-gamma vs all other treatments. Addition of exogenous, purified alginate to the alginate-negative biofilms restored resistance to human leukocyte killing. Our results suggest that although alginate may not play a significant role in bacterial attachment, biofilm development, and formation, it may play an important role in protecting mucoid P. aeruginosa biofilm bacteria from the human immune system.

Endotoxin Level Measurement in Hemodialysis Biofilm Using "The Whole Blood Assay"

Biofilms have been found on the inner surface of silicone tubing inside dialysis machines. Endotoxin releasing from those biofilms increases the bioincompatibility of dialysis liquids and leads to long-term inflammatory complications among dialysis patients. Endotoxin measurement is recommended for the control of dialysis liquids. This article describes the use of a new method, the Whole Blood Assay (WBA), for endotoxin quantification in dialysis biofilms. Biofilms were suspended in sterile water by scraping the tubing samples. Diluted blood samples from healthy donors were stimulated overnight with the contaminated suspension. Stimulated mononuclear cells released IL-1beta in response to endotoxins. IL-1beta level was then measured using an ultrasensitive ELISA method. We demonstrated a semilogarithmic model in which the optical densities measured after the ELISA assay increases linearly with the levels of endotoxin. This model allowed the determination of the amount of endotoxins in biofilm samples with a detection limit of 0.032 EU/mL. Most of the time, the amounts of endotoxin measured by the WBA were higher than those measured by the Limulus Amoebocyte Lysate (LAL) assay. This study suggested the presence of "endotoxin-like" compounds different from the lipopolysaccharides that are not detected by the LAL assay. We concluded that the LAL is necessary but insufficient to have a representative quantification of endotoxins that could be hazardous to patient health.

Impact of polyunsaturated fatty acids on cytoskeletal linkage of L-selectin

Polyunsaturated fatty acid [omega-3 polyunsaturated fatty acids (omega-3PUFAs)] incorporation into cell membranes has been shown to have potent anti-inflammatory activity, though the mechanisms involved are only partially characterized. Here, we show that PUFA enrichment of T cell membranes decreased the overall expression of L-selectin as well as a highly conserved epitope on L-selectin that may serve as a marker for optimal protein function. Additionally, PUFA enrichment inhibited L-selectin cytoskeletal association, which is thought to be important for optimal functional activity. In support of this, PUFA enrichment of gammadelta T cell membranes reduced L-selectin-dependent rolling interactions under conditions mimicking physiological flow. Taken together, these data suggest that the anti-inflammatory activity of omega-3 polyunsaturated fatty acids may be due, in part, to a novel effect on L-selectin, namely PUFA reduction or prevention of cytoskeletal association of L-selectin.

Human leukocytes adhere to, penetrate, and respond to Staphylococcus aureus biofilms

Staphylococcus aureus is a common pathogen responsible for nosocomial and community infections. It readily colonizes indwelling catheters, forming microbiotic communities termed biofilms. S. aureus bacteria in biofilms are protected from killing by antibiotics and the body's immune system. For years, one mechanism behind biofilm resistance to attack from the immune system's sentinel leukocytes has been conceptualized as a deficiency in the ability of the leukocytes to penetrate the biofilm. We demonstrate here that under conditions mimicking physiological shear, leukocytes attach, penetrate, and produce cytokines in response to maturing and fully matured S. aureus biofilm.

Early diagnosis of Johne's disease in the American bison by monoclonal antibodies directed against antigen 85

Several monoclonal antibodies derived from hybridomas from mice that had been immunized with recombinant Mycobacterium bovis antigen 85 (Ag85) were tested for reactivity against antigen 85 (Ag85) from M. bovis and against sera from 100 bison inoculated with M. paratuberculosis and from 100 control bison from a disease-free herd. Monoclonal antibodies mAb85.1, mAb85.44.1, mAb85.44.9, and mAb85.96 reacted against three or four 30-33-kDa bands of the Ag85 complex of M. bovis. Importantly, these mAbs also reacted with bands of similar molecular weight in the sera of bison inoculated with M. paratuberculosis. Additionally, when sera from 198 bison in four herds were reacted against mAb85.1 and mAb85.96, 26 bison reacted positively for the presence of Ag85 by either mAb or by both. These preliminary results indicate that monoclonal antibodies may eventually lead to a reliable diagnostic test for the early detection of M. paratuberculosis infections in ruminants as well as to a means for identifying contaminated dairy products.

Immunology of Staphylococcal biofilm infections in the eye: new tools to study biofilm endophthalmitis

Endophthalmitis is an important disease of the eye that is most frequently caused by postoperative and post-traumatic introduction of bacteria into the posterior segment of the eye. In the case of severe infections, visual acuity is greatly damaged or completely lost. Much work has focused on the ability of planktonic bacteria to cause infection and ocular damage while little work has focused on chronic infections in endophthalmitis mediated by the formation of bacterial biofilms on the surface of the lens. This review focuses on the interaction of Staphylococcus aureus and Staphylococcus epidermidis lens-associated biofilms in endophthalmitis. Additionally, this review highlights some relevant biofilm-immune system interactions and outlines a new in vivo mouse model to explore biofilm-related infections in endophthalmitis.

Ultrastructural examination of cytoskeletal linkage of L-selectin and comparison of L-selectin cytoskeletal association to that of other human and bovine lymphocyte surface antigens

L-selectin is constitutively expressed on most leukocytes and is responsible for the initial events in cell trafficking termed tethering and rolling. Recently, L-selectin has been shown to associate with the actin-based cytoskeleton under a variety of conditions. In an effort to better understand L-selectin cytoskeletal association and the ultrastructural nature of the cytoskeleton itself, we provide a comparison of the cytoskeletal association of various human and bovine surface proteins in relation to L-selectin. Electron microscopic examination of the cytoskeleton provided further data on the ultrastructure of freshly isolated peripheral lymphocytes as well as demonstrated L-selectin localization to the periphery of the cytoskeleton following low dose detergent treatment of the cell. Clusters of colloidal-gold-stained L-selectin were found on the surface of the detergent-treated lymphocytes, even though these particles completely lacked microvilli. By flow cytometry, we have defined three distinct patterns of cytoskeletal association; constitutive, inductive, and mAb crosslink-induced, and assigned human and bovine CD2, CD3, CD4, CD5, CD8, CD18, CD19, CD44, CD45RA, CD45RO, alphabeta TCR, gammadelta TCR, E-selectin ligands, and L-selectin surface antigens to one of these respective patterns. SDS-PAGE analyses confirmed most of the flow cytometry results. Depending upon its conformation, L-selectin fell into the inductive or mAb crosslink-induced pattern of association, similar to E-selectin ligand(s). Our data provide additional insight into the functional role of L-selectin and the cytoskeleton in immunological events.

Antibody binding to a conformation-dependent epitope induces L-selectin association with the detergent-resistant cytoskeleton

L-Selectin mediates leukocyte rolling on endothelium and immobilized leukocytes. Its regulation has been the subject of much study, and the conformation of the molecule may play an important role in its function. Here we report that a conformational change in L-selectin, induced by an anti-lectin domain mAb (LAM1-116) and recognized by another mAb directed to a conserved epitope on L-selectin (EL-246), predisposed L-selectin to cytoskeletal association. This effect was due to direct binding of the mAb, not to overt signaling events, and was specific to LAM1-116. Nineteen other anti-L-selectin mAbs directed against the lectin, epidermal growth factor, or short consensus repeat domains lacked this activity. The induced conformational change occurred at 37 degrees C, at 4 degrees C, in the presence of sodium azide and tyrosine kinase inhibitors herbimycin A and genistein, and with soluble detergent-extracted L-selectin. In the presence of LAM1-116, EL-246 induced cytoskeletal association of L-selectin in the absence of Ab cross-linking as visualized by L-selectin staining after low dose detergent treatment of the cells. We propose that the conformational change described herein regulates L-selectin-mediated events by exposing a high avidity binding site that, when engaged, triggers association of L-selectin with the cytoskeleton, which may lead to stronger tethers with physiological ligands.

Comparative ultrastructure and expression of L-selectin on bovine alphabeta and gammadelta T cells

Compared to most alphabeta T cells, bovine gammadelta T cells express two to five times the level of L-selectin and have a much higher capacity to roll on monolayers of endothelial cells, platelets, and leukocytes in assays done under physiological flow. To gain additional insight into the basis for these differences, scanning (SEM) and transmission (TEM) electron microscopy were used to compare the cellular ultrastructure of bovine gammadelta and alphabeta T cells and to study the expression of L-selectin on these cells. It is interesting that gammadelta T cells had more than twice as many microvilli and other surface projections on a per cell basis as alphabeta T cells. This was not due to the gammadelta T cell being larger; after adhesion and fixation procedures used for the EM studies, gammadelta T cells averaged 3.9 +/- 0.01 microm in diameter, whereas alphabeta T cells were slightly larger (5.7 +/- 0.01 microm in diameter). As previously shown for human neutrophils and lymphocytes, L-selectin was preferentially localized to the tips of the microvilli. In contrast, WC1, a lineage-specific antigen on gammadelta T cells, was localized on the plasmalemma between the microvilli. Our findings suggest that more effective rolling of gammadelta T cells in various in vitro flow assays may be due to the greater number of microvilli on gammadelta T cells leading to a higher number of contact sites during adhesion events. In addition, this physical parameter may explain the increased level of L-selectin expression on gammadelta versus alphabeta T cells because L-selectin is clustered at the tips of microvilli.