The effects of extracellular slime from Staphylococcus epidermidis on phagocytic ingestion and killing

Local Antibiotic Delivery Options in Prosthetic Joint Infection

Prosthetic Joint Infection (PJI) causes significant morbidity and mortality for patients globally. Delivery of antibiotics to the site of infection has potential to improve the treatment outcomes and enhance biofilm eradication. These antibiotics can be delivered using an intra-articular catheter or combined with a carrier substance to enhance pharmacokinetic properties. Carrier options include non-resorbable polymethylmethacrylate (PMMA) bone cement and resorbable calcium sulphate, hydroxyapatite, bioactive glass, and hydrogels. PMMA allows for creation of structural spacers used in multi-stage revision procedures, however it requires subsequent removal and antibiotic compatibility and the levels delivered are variable. Calcium sulphate is the most researched resorbable carrier in PJI, but is associated with wound leakage and hypercalcaemia, and clinical evidence for its effectiveness remains at the early stage. Hydrogels provide a versatile combability with antibiotics and adjustable elution profiles, but clinical usage is currently limited. Novel anti-biofilm therapies include bacteriophages which have been used successfully in small case series.

Challenges and New Therapeutic Approaches in the Management of Chronic Wounds

Chronic non-healing wounds are estimated to cost the US healthcare $28-$31 billion per year. Diabetic ulcers, arterial and venous ulcers, and pressure ulcers are some of the most common types of chronic wounds. The burden of chronic wounds continues to rise due to the current epidemic of obesity and diabetes and the increase in elderly adults in the population who are more vulnerable to chronic wounds than younger individuals. This patient population is also highly vulnerable to debilitating infections caused by opportunistic and multi-drug resistant pathogens. Reduced microcirculation, decreased availability of cytokines and growth factors that promote wound closure and healing, and infections by multi-drug resistant and biofilm forming microbes are some of the critical factors that contribute to the development of chronic non-healing wounds. This review discusses novel approaches to understand chronic wound pathology and methods to improve chronic wound care, particularly when chronic wounds are infected by multi-drug resistant, biofilm forming microbes.

Thai herbal formulation 'Ya-Pit-Samut-Noi': Its antibacterial activities, effects on bacterial virulence factors and in vivo acute toxicity

ETHNOPHARMACOLOGICAL RELEVANCE

A Thai herbal formulation 'Ya-Pit-Samut-Noi' containing Nigella sativa (seed), Piper retrofractum (fruit), Punica granatum (pericarp), and Quercus infectoria (nutgall) has long been traditionally used to treat diarrhea or bloody mucous diarrhea. Scientific information is very important to support its therapeutic effects and traditional drug development.

AIM OF THE STUDY

This study aimed to evaluate the antibacterial activities of Ya-Pit-Samut-Noi against diarrhea-causing bacteria and determine its effects on bacterial virulence factors and in vivo acute toxicity.

MATERIALS AND METHODS

Ethanol and water extracts of Ya-Pit-Samut-Noi and its plant components were prepared. The agar diffusion method was used for preliminary screening of antibacterial activity of the extracts against diarrhea-causing bacteria including Staphylococcus aureus, Vibrio cholerae, and Vibrio parahaemolyticus. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were assessed using broth microdilution method. The effects on bactericidal activity, bacterial cell wall, and cell membrane were examined by time-kill, lysis, and leakage assays, respectively. The effects on bacterial virulence factors including quorum-sensing system, biofilm production, and swarming motility were determined. Phytochemical screening was carried out to identify the group of chemical compounds present in the formulation extracts. Acute toxicity study was conducted by a single oral dose of 2000 mg/kg body weight in Wistar albino rats.

RESULTS

Ethanol and water extracts of Ya-Pit-Samut-Noi and Quercus infectoria demonstrated antibacterial efficacy against all bacterial strains as revealed by zones of inhibition ranging from 7.0 to 24.5 mm. The ethanol and water extracts of Ya-Pit-Samut-Noi and Quercus infectoria produced strong bacteriostatic activity against V. parahaemolyticus (n = 11) with an MIC range of 7.81-250 μg/ml. Only the ethanol extract of Ya-Pit-Samut-Noi produced MBC values less than or equal to 1000 μg/ml against all V. parahaemolyticus. Based on time-kill study, no surviving V. parahaemolyticus (ATCC 17802 and 5268) cells were detected within 6-12 h after treatment with the ethanol extract of Ya-Pit-Samut-Noi at MBC-4MBC concentrations. Vibrioparahaemolyticus ATCC 17802 cells treated with the ethanol extract of Ya-Pit-Samut-Noi demonstrated no lysis or leakage through the bacterial membrane was not observed. At low concentrations (0.125-0.25 μg/ml) the ethanol extract of Ya-Pit-Samut-Noi inhibited violacein production by Chromobacterium violaceum DMST 21761 without affecting the bacterial growth. The ethanol (31.25-62.5 μg/ml) and water (31.25-250 μg/ml) extracts of Ya-Pit-Samut-Noi inhibited biofilm production by S. aureus. The ethanol and water extracts of Ya-Pit-Samut-Noi at 1000 μg/ml reduced the swarming motility of Escherichia coli O157: H7 by 74.98% and 52.65%, respectively. Tannins and terpenoids were detected in both the ethanol and water extracts. Flavonoids were present only in the ethanol extract. Alkaloids and antraquinones were not noticed in either extract. In the acute toxicity study, there were no significant changes in hematological and biochemical parameters nor were adverse effects on mortality, general behaviors, body weight, or organ weights detected.

CONCLUSIONS

The scientific evidence from this study supported the therapeutic effects and safety of the traditional Thai herbal formulation 'Ya-Pit-Samut-Noi' which has been used as an alternative treatment for gastrointestinal infections in Thailand.

Development and characterization of an oral multispecies biofilm implant flow chamber model

Peri-implant infections are the most common cause of implant failure in modern dental implantology. These are caused by the formation of biofilms on the implant surface and consist of oral commensal and pathogenic bacteria, which harm adjacent soft and hard tissues and may ultimately lead to implant loss. In order to improve the clinical situation, there has to be a better understanding of biofilm formation on abiotic surfaces. Therefore, we successfully developed a system to cultivate an oral multispecies biofilm model in a flow chamber system, optimized for the evaluation of biofilm formation on solid materials by direct microscopic investigation. The model contains four relevant oral bacterial species: Streptococcus oralis, Actinomyces naeslundii, Veillonella dispar and Porphyromonas gingivalis in ratios similar to the native situation. The reliability of the developed “Hanoverian Oral Multispecies Biofilm Implant Flow Chamber” (HOBIC) model was verified. Biofilm volume and live/dead distribution within biofilms were determined by fluorescence staining and confocal laser scanning microcopy (CLSM). The individual species distribution was analyzed using quantitative real time PCR with propidium monoazide pretreatment (PMA-qRT-PCR) and by urea-NaCl fluorescence in situ hybridization (urea-NaCl-FISH). This in vitro model may be used to analyze biofilm formation on dental implants in more detail and to develop future implant systems with improved material properties.

Silver-zinc redox-coupled electroceutical wound dressing disrupts bacterial biofilm

Pseudomonas aeruginosa biofilm is commonly associated with chronic wound infection. A FDA approved wireless electroceutical dressing (WED), which in the presence of conductive wound exudate gets activated to generate electric field (0.3–0.9V), was investigated for its anti-biofilm properties. Growth of pathogenic P. aeruginosa strain PAO1 in LB media was markedly arrested in the presence of the WED. Scanning electron microscopy demonstrated that WED markedly disrupted biofilm integrity in a setting where silver dressing was ineffective. Biofilm thickness and number of live bacterial cells were decreased in the presence of WED. Quorum sensing genes lasR and rhlR and activity of electric field sensitive enzyme, glycerol-3-phosphate dehydrogenase was also repressed by WED. This work provides first electron paramagnetic resonance spectroscopy evidence demonstrating that WED serves as a spontaneous source of reactive oxygen species. Redox-sensitive multidrug efflux systems mexAB and mexEF were repressed by WED. Taken together, these observations provide first evidence supporting the anti-biofilm properties of WED.

Interactions of Staphylococci with Osteoblasts and Phagocytes in the Pathogenesis of Implant-Associated Osteomyelitis

In spite of great advancements in the field of biomaterials and in surgical techniques, the implant of medical devices is still associated with a high risk of bacterial infection. Implant-associated osteomyelitis is a deep infection of bone around the implant. The continuous inflammatory destruction of bone tissues characterizes this serious bone infectious disease. Staphylococcus aureus and Staphylococcus epidermidis are the most prevalent etiologic agents of implant-associated infections, together with the emerging pathogen Staphylococcus lugdunensis. Various interactions between staphylococci, osteoblasts, and phagocytes occurring in the peri-prosthesis environment play a crucial role in the pathogenesis of implant-associated osteomyelitis. Here we focus on two main events: internalization of staphylococci into osteoblasts, and bacterial interactions with phagocytic cells.

Inhibition of biofilm formation, quorum sensing and infection in Pseudomonas aeruginosa by natural products-inspired organosulfur compounds

Using a microplate-based screening assay, the effects on Pseudomonas aeruginosa PAO1 biofilm formation of several S-substituted cysteine sulfoxides and their corresponding disulfide derivatives were evaluated. From our library of compounds, S-phenyl-L-cysteine sulfoxide and its breakdown product, diphenyl disulfide, significantly reduced the amount of biofilm formation by P. aeruginosa at levels equivalent to the active concentration of 4-nitropyridine-N-oxide (NPO) (1 mM). Unlike NPO, which is an established inhibitor of bacterial biofilms, our active compounds did not reduce planktonic cell growth and only affected biofilm formation. When used in a Drosophila-based infection model, both S-phenyl-L-cysteine sulfoxide and diphenyl disulfide significantly reduced the P. aeruginosa recovered 18 h post infection (relative to the control), and were non-lethal to the fly hosts. The possibility that the observed biofilm inhibitory effects were related to quorum sensing inhibition (QSI) was investigated using Escherichia coli-based reporters expressing P. aeruginosa lasR or rhIR response proteins, as well as an endogenous P. aeruginosa reporter from the lasI/lasR QS system. Inhibition of quorum sensing by S-phenyl-L-cysteine sulfoxide was observed in all of the reporter systems tested, whereas diphenyl disulfide did not exhibit QSI in either of the E. coli reporters, and showed very limited inhibition in the P. aeruginosa reporter. Since both compounds inhibit biofilm formation but do not show similar QSI activity, it is concluded that they may be functioning by different pathways. The hypothesis that biofilm inhibition by the two active compounds discovered in this work occurs through QSI is discussed.

Molecular basis of Staphylococcus epidermidis infections

Staphylococcus epidermidis is the most important member of the coagulase-negative staphylococci and one of the most abundant colonizers of human skin. While for a long time regarded as innocuous, it has been identified as the most frequent cause of device-related infections occurring in the hospital setting and is therefore now recognized as an important opportunistic pathogen. S. epidermidis produces a series of molecules that provide protection from host defenses. Specifically, many proteins and exopolymers, such as the exopolysaccharide PIA, contribute to biofilm formation and inhibit phagocytosis and the activity of human antimicrobial peptides. Furthermore, recent research has identified a family of pro-inflammatory peptides in S. epidermidis, the phenol-soluble modulins (PSMs), which have multiple functions in immune evasion and biofilm development, and may be cytolytic. However, in accordance with the relatively benign relationship that S. epidermidis has with its host, production of aggressive members of the PSM family is kept at a low level. Interestingly, in contrast to S. aureus with its large arsenal of toxins developed for causing infection in the human host, most if not all "virulence factors" of S. epidermidis appear to have original functions in the commensal lifestyle of this bacterium.

Staphylococcus epidermidis uses distinct mechanisms of biofilm formation to interfere with phagocytosis and activation of mouse macrophage-like cells 774A.1

Assembly of adherent biofilms is the key mechanism involved in Staphylococcus epidermidis virulence during device-associated infections. Aside from polysaccharide intercellular adhesin (PIA), the accumulation-associated protein Aap and the extracellular matrix binding protein Embp act as intercellular adhesins, mediating S. epidermidis cell aggregation and biofilm accumulation. The aim of this study was to investigate structural features of PIA-, Aap-, and Embp-mediated S. epidermidis biofilms in more detail and to evaluate their specific contributions to biofilm-related S. epidermidis immune escape. PIA-, Embp-, and Aap-mediated biofilms exhibited substantial morphological differences. Basically, PIA synthesis induced formation of macroscopically visible, rough cell clusters, whereas Aap- and Embp-dependent biofilms preferentially displayed a smooth layer of aggregated bacteria. On the microscopic level, PIA was found to form a string-like organized extracellular matrix connecting the bacteria, while Embp produced small deposits of intercellular matrix and Aap was strictly localized to the bacterial surface. Despite marked differences, S. epidermidis strains using PIA, Aap, or Embp for biofilm formation were protected from uptake by J774A.1 macrophages, with similarly efficiencies. In addition, compared to biofilm-negative S. epidermidis strains, isogenic biofilm-forming S. epidermidis induced only a diminished inflammatory J774A.1 macrophage response, leading to significantly (88.2 to 88.7%) reduced NF-κB activation and 68.8 to 83% reduced interleukin-1β (IL-1β) production. Mechanical biofilm dispersal partially restored induction of NF-κB activation, although bacterial cell surfaces remained decorated with the respective intercellular adhesins. Our results demonstrate that distinct S. epidermidis biofilm morphotypes are similarly effective at protecting S. epidermidis from phagocytic uptake and at counteracting macrophage activation, providing novel insights into mechanisms that could contribute to the chronic and persistent course of biofilm-related S. epidermidis foreign material infections.

The destruction of Escherichia coli biofilms using high-intensity focused ultrasound

High-intensity focused ultrasound (HIFU) has shown great potential for replacing surgery in many applications. In this work, HIFU was used to destroy Escherichia coli (E. coli) biofilms that had been grown on chambered microscope slides. Biofilms are central to the pathogenesis and persistence of nosocomial (hospital-acquired) infections associated with indwelling medical devices. The slides were exposed to 9.1 mus pulses at a pulse repetition frequency of 1000 Hz. The pulses were generated by a 1.1 MHz spherically focused source with a focal length of 6.3 cm and an active diameter of 7 cm. The peak rarefactional pressure for the pulses was varied as 3.1, 4.1, 5.2, 6.2 and 7.6 MPa in addition to a sham where the biofilms were not exposed. The effectiveness of the treatment was assessed by determining the number of colony forming units (CFU) remaining following exposure of the bacteria to HIFU. Most of the biofilms treated at the higher exposures of 6.2 and 7.6 MPa had no detectable CFU, indicating that bacteria in the biofilm were killed by the treatment or that treatment disrupted the biofilm and released bacteria from the slide. However, the ability of some bacteria to survive at the higher exposure settings needs to be resolved prior to implementing the treatment clinically.

Biofilm formation induces C3a release and protects Staphylococcus epidermidis from IgG and complement deposition and from neutrophil-dependent killing

BACKGROUND

Biofilm formation is considered to be an important virulence factor of the opportunistic pathogen Staphylococcus epidermidis. We hypothesized that biofilm formation could interfere with the deposition of immunoglobulins and complement on the bacterial surface, leading to diminished activation of the complement system and protection from killing by human phagocytes.

METHODS

The killing of biofilm-encased and planktonically grown wild-type (wt) S. epidermidis and the killing of an isogenic biofilm-negative ica mutant (ica(-)) by human polymorphonuclear neutrophils (PMNs) were compared. C3a induction and deposition of C3b and immunoglobulin G (IgG) on the bacteria after opsonization with human serum were assessed by enzyme-linked immunosorbent assay, flow cytometry, and electron microscopy. The virulence of the bacterial strains was compared in a mouse model of catheter-associated infection.

RESULTS

Biofilm-embedded wt S. epidermidis was killed less well by human PMNs and induced more C3a than planktonically grown wt and ica(-) S. epidermidis. However, the deposition of C3b and IgG on the bacterial surface was diminished in biofilm-encased staphylococci. wt S. epidermidis was more virulent in implant-associated infections and was killed more slowly than ica(-) in ex vivo assays of killing by PMNs.

CONCLUSIONS

The results indicate that prevention of C3b and IgG deposition on the bacterial surface contributes to the biofilm-mediated protection of S. epidermidis from killing by PMNs.

Biofilms in ear, nose, and throat infections: how important are they?

BACKGROUND

Biofilms present a new challenging concept in sustaining chronic, common antibiotic-resistant ear, nose, and throat (ENT) infections. They are communities of sessile bacteria embedded in a matrix of extracellular polymeric substances of their own synthesis that adhere to a foreign body or a mucosal surface with impaired host defense. The aim of this paper is to review the literature on ENT diseases that can be attributed to biofilm formation and to discuss options for future treatment.

MATERIALS AND METHODS

Literature review from Medline and database sources. Electronic links and related books were also included.

STUDY SELECTION

Controlled clinical trials, animal models, ex vivo models, laboratory studies, retrospective studies, and systematic reviews.

DATA SYNTHESIS

Biofilm formation is a dynamic five-step process guided by interbacterial communicating systems. Bacteria in biofilms express different genes and have markedly different phenotypes from their planktonic counterparts. Detachment of cells, production of endotoxin, increased resistance to the host immune system, and provision of a niche for the generation of resistant organisms are biofilm processes that could initiate the infection process. Effective prevention and management strategies include interruption of quorum sensing, inhibition of related genes, disruption of the protective extrapolymer matrix, macrolides (clarithromycin and erythromycin), and mechanical debridement of the biofilm-bearing tissues. With regard to medical indwelling devices, surface treatment of fluoroplastic grommets and redesign of cochlear implants could minimize initial microbial colonization.

CONCLUSION

As the role of biofilms in human infection becomes better defined, ENT surgeons should be prepared to deal with their unique and tenacious nature.

BisEDT and RIP act in synergy to prevent graft infections by resistant staphylococci

Staphylococci are a major cause of infections associated with indwelling medical devices. Biofilm formation on these devices adds to the antibiotic resistance seen among clinical isolates. RNAIII-inhibiting peptide (RIP) is a heptapeptide that inhibits staphylococcal pathogenesis, including biofilm formation, by obstructing quorum sensing mechanisms. Bismuth ethanedithiol (BisEDT) also prevents biofilm formation at subinhibitory concentrations. RIP and BisEDT were combined to prevent infections in a rat graft model, using antibiotic sensitive and resistant strains of Staphylococcus aureus and Staphylococcus epidermidis. BisEDT, RIP, or rifampin, or their combinations reduced the graft associated bacterial load over seven days. BisEDT-RIP was the best combination, reducing bacterial load to undetectable levels. BisEDT-RIP may prove useful for coating medical devices to prevent staphylococcal infections.

Isolation, structural characterization, and immunological evaluation of a high-molecular-weight exopolysaccharide from Staphylococcus aureus

Colonization of implanted medical devices by coagulase-negative staphylococci such as Staphylococcus epidermidis is mediated by the bacterial polysaccharide intercellular adhesin (PIA), a polymer of beta-(1-->6)-linked glucosamine substituted with N-acetyl and O-succinyl constituents. The icaADBC locus containing the biosynthetic genes for production of PIA has been identified in both S. epidermidis and S. aureus. Whereas it is clear that PIA is a constituent that contributes to the virulence of S. epidermidis, it is less clear what role PIA plays in infection with S. aureus. Recently, identification of a novel polysaccharide antigen from S. aureus termed poly N-succinyl beta-(1-->6)-glucosamine (PNSG) has been reported. This polymer was composed of the same glycan backbone as PIA but was reported to contain a high proportion of N-succinylation rather than acetylation. We have isolated a glucosamine-containing exopolysaccharide from the constitutive over-producing MN8m strain of S. aureus in order to prepare polysaccharide-protein conjugate vaccines. In this report we demonstrate that MN8m produced a high-molecular-weight (>300,000 Da) polymer of beta-(1-->6)-linked glucosamine containing 45-60% N-acetyl, and a small amount of O-succinyl (approx 10% mole ratio to monosaccharide units). By detailed NMR analyses of polysaccharide preparations, we show that the previous identification of N-succinyl was an analytical artifact. The exopolysaccharide we have isolated is active in in vitro hemagglutination assays and is immunogenic in mice when coupled to a protein carrier. We therefore conclude that S. aureus strain MN8m produces a polymer that is chemically and biologically closely related to the PIA produced by S. epidermidis.

Comparative in vitro activity of vancomycin and levofloxacin in combination with rifampin against planktonic versus sessile cells of Staphylococcus epidermidis

STUDY OBJECTIVE

To evaluate the activity of vancomycin and levofloxacin alone and combined with rifampin against planktonic and sessile cells.

INTERVENTION

Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of the three drugs were determined against a clinical isolate of methicillin-resistant Staphylococcus epidermidis (MRSE 23) and a reference strain of MRSE (ATCC 35984).

MEASUREMENTS AND MAIN RESULTS

The MICs/MBCs of vancomycin, levofloxacin, and rifampin against MRSE 23 were 0.78/0.78 microg/ml, 0.19/0.19 microg/ml or below, and 0.19/0.19 microg/ml or below, and against ATCC 35984 were 0.78/1.56 microg/ml, 0.19/0.19 microg/ml or below, and 0.19/0.19 microg/ml or below, respectively. A 99.9% killing activity was achieved with vancomycin, levofloxacin, and vancomycin-levofloxacin against planktonic cells of MRSE 23 (18.9, 21.3, and 17.5 hrs, respectively) and only with levofloxacin against ATCC 35984 (21.5 hrs). No regimen achieved 99.9% killing activity against sessile cells.

CONCLUSION

Adding rifampin was antagonistic against planktonic cells and had an additive effect against sessile cells. Activity typically reported using nutrient-rich, planktonic cells may not be applicable to sessile cells under environmental and growth restrictions.

A novel image-analysis technique for measurement of bacterial cell surface tension

Cell-surface hydrophobicity is different for Staphylococcus epidermidis cells grown under different environmental conditions; this might influence attachment and colonization of surfaces. Although a wide variety of techniques has been employed to measure bacterial surface hydrophobicity, including contact angle determinations, adherence to hydrocarbons, hydrophobic-interaction chromatography and salt aggregation, many of these either require large numbers of cells or do not yield comparable quantitative data. This study describes a novel, quantitative method for the determination of bacterial surface tension on the basis of image analysis of cell-cell interactions. S. epidermidis (strains 900 and 901) were suspended in different concentrations of propanol of known surface tension and examined by bright-field microscopy linked via a charge-couple device (CCD) camera to an image analyser. Frames were chosen randomly and the data recorded as a ratio of count/percentage coverage for each frame. The results showed that for strains 900 and 901 this ratio was maximum at surface tensions of 67 and 61 mN m(-1) respectively. At these values of minimal interaction the surface tension of the liquid was equal to the bacterial cell surface tension. The results were in close agreement with those obtained from contact angles. The advantage of surface tension measurements is that, irrespective of the method used, the results generated are quantitative values and are therefore directly comparable. The method reported is reliable, reproducible and is of particular value because the number of cells required is, typically, at least two orders of magnitude lower than is required for commonly used alternative methods.

The inhibitory effect of Staphylococcus epidermidis slime on the phagocytosis of murine peritoneal macrophages is interferon-independent

The extracellular slime produced by Staphylococcus epidermidis has been shown to interfere with several human neutrophil functions in vitro, such as chemotaxis, degranulation and phagocytosis. Slime production has been suggested as a useful marker for clinically significant infections with coagulase-negative Staphylococcus. Since the main role of macrophages in defense mechanisms is phagocytosis, the effect of slime on the phagocytic activity of macrophages was investigated. The phagocytic activity of murine peritoneal macrophages treated with slime in vitro decreased in a dose-dependent fashion. A similar decrease was also observed in macrophages isolated from mice that had previously received intraperitoneal injection of slime. To investigate whether interferon also plays a role in this process, mice were treated with interferon or an interferon inducer, polyinosinic-polycytidylic acid (poly I:C), together with slime before macrophage isolation. The slime-suppressed phagocytic activity of macrophages was partially relieved by both agents, and the recovery effect of poly I:C in slime-suppressed phagocytosis of macrophages in vivo might be attributed to the increased interferon level in peritoneal fluid and sera. However, when slime was given to poly I:C-pretreated mice, the phagocytic activity remained suppressed. Thus, it appears that slime is able to suppress the phagocytic activity of macrophages regardless of the state of macrophage activation by poly I:C. The results suggest that the inhibition of phagocytosis by S. epidermidis slime may be independent from the activation of interferon.

Phagocytosis and oxidative-burst response of planktonic Staphylococcus epidermidis RP62A and its non-slime-producing variant in human neutrophils

The ability of bacterial organisms to produce an extracellular polysaccharide matrix known as slime has been associated with increased virulence and delayed infections in various prosthetic implants. Within a biofilm, this slime may protect the embedded bacteria from host defense mechanisms, especially phagocytosis by polymorphonuclear leukocytes. To determine whether planktonic Staphylococcus epidermidis is protected in a similar way, a novel flow cytometric assay was performed, measuring ingestion and adherence during phagocytosis and the production of superoxide during oxidative burst. Hydrophobicity was determined by hydrophobic interaction chromatography. Slime-producing S. epidermidis RP62A and its phenotypic variant, non-slime-producing RP62A-NA, were compared. The results showed increased phagocytosis of RP62A at 2, 5, 10, and 30 min; increased adherence of RP62A at 30 s and 30 min; and increased superoxide production of RP62A after 2 min. Decreased hydrophobicity of RP62A over RP62A-NA was correlated with a hydrophilic slime coat. The data argue that the host aggressively combats slime-producing S. epidermidis. This biological phenomenon is potentially important during bacteremia to prevent further adhesion, accumulation, and the genesis of a bacterial biofilm on implants or tissue surfaces.