Infection after use of nonpreserved human amniotic membrane for the reconstruction of the ocular surface

Experimental evaluation of safety and efficacy of plasma-treated poly-ε-caprolactone membrane as a substitute for human amniotic membrane in treating corneal epithelial defects in rabbit eyes

Purpose:

To evaluate biocompatibility and safety of plasma-treated poly-ε-caprolactone (pPCL) membrane compared to the human amniotic membrane in the healing of corneal epithelial defects in an experimental model.

Methods:

This is a prospective, randomized animal study including 12 rabbits. Circular epithelial injury measuring 6 mm in diameter was induced over the central cornea of one eye in twelve rabbits. The rabbits were randomized into two groups; in group A, the defect was covered with human amniotic membrane, while in group B, an artificial membrane made of bio-polymer plasma-treated poly-ε-caprolactone was grafted. Six rabbits were euthanized after 1 month and the other six after 3 months and the corneal epithelium was evaluated histopathologically and with immunohistochemistry.

Results:

Light microscopy of the corneal tissue performed after 1 month and 3 months demonstrated similar findings with no significant complications in either group. Immunohistochemistry with anti-CK-3 antibody showed characteristic corneal phenotype in the healed epithelium. In eyes grafted with pPCL membrane, epithelial healing as estimated by a decrease in size of the defect was significantly better than the group treated with the human amniotic membrane at all time periods monitored (P < 0.05), except day 1 (P = 0.83). The percentage reduction in the size of the epithelial defect was also significantly more in the pPCL membrane group as compared to the human amniotic membrane at all time periods (P < 0.05 at all observations) post-implantation except day 1 (P = 0.73).

Conclusion:

Plasma-treated poly-ε-caprolactone membrane is safe, biocompatible, and effective in the healing of corneal epithelial defects in rabbits.

Surgical alternatives to keratoplasty in microbial keratitis

Penetrating keratoplasty is often required in microbial keratitis not responding to the standard treatments available or the development of complications like corneal perforation. Performing keratoplasty in microbial keratitis has several challenges, the major ones being the availability of donor corneal tissue and the poor success of the corneal graft performed in such a setting. For overcoming these challenges, several alternatives to keratoplasty have been described. Broadly, these options could be categorized into autologous tissues such as conjunctival and tenon tissue, synthetic products like tissue adhesives and therapeutic contact lenses, or biological tissues like amniotic membrane graft. These alternative modalities are not universal. They have their specific indications in microbial keratitis. Most of these alternatives are useful only for small corneal perforations. While autologous tissues are cost-effective and readily available, lack of tectonic support is a significant limitation. Tissue adhesives are excellent alternatives in terms of tectonic support, but surface irregularity and tissue reaction are their potential limitations. The amniotic membrane is useful for small corneal perforations, but availability, cost, and poor tectonic support restrict its use. Herein, we discuss these various alternatives to keratoplasty in microbial keratitis, their indications, advantages, disadvantages, and the various techniques of performing these procedures.

Preparation of Dried Amniotic Membrane for Corneal Repair

Amniotic membrane transplantation is an established therapeutic and biological adjunct for several clinical situations, including treatment of diabetic foot ulcers and ocular surface disease. However, poorly standardized and validated clinical preparation and storage procedures can render the final product highly variable and an unpredictable biomaterial. We have therefore developed a novel, standardized method for processing and dry-preserving amniotic membrane, minimizing biochemical, compositional, and structure damage to produce a potentially superior membrane suitable for clinical use. The intellectual property associated with this methodology was patented by the University of Nottingham and licensed to NuVision^® Biotherapies which formed the basis of the Tereo^® manufacturing process which is used to manufacture Omnigen^®.

Validation and assessment of an antibiotic-based, aseptic decontamination manufacturing protocol for therapeutic, vacuum-dried human amniotic membrane

Amniotic membrane (AM) is used to treat a range of ophthalmic indications but must be presented in a non-contaminated state. AM from elective caesarean sections contains natural microbial contamination, requiring removal during processing protocols. The aim of this study was to assess the ability of antibiotic decontamination of AM, during processing by innovative low-temperature vacuum-drying. Bioburden of caesarean section AM was assessed, and found to be present in low levels. Subsequently, the process for producing vacuum-dried AM (VDAM) was assessed for decontamination ability, by artificially loading with Staphylococcus epidermidis at different stages of processing. The protocol was highly efficient at removing bioburden introduced at any stage of processing, with antibiotic treatment and drying the most efficacious steps. The antibacterial activity of non-antibiotic treated AM compared to VDAM was evaluated using minimum inhibitory/biocidal concentrations (MIC/MBC), and disc diffusion assays against Meticillin-resistant Staphylococcus aureus, Meticillin-resistant S. epidermidis, Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis. Antibacterial activity without antibiotic was low, confirmed by high MIC/MBC, and a no inhibition on agar lawns. However, VDAM with antibiotic demonstrated effective antibacterial capacity against all bacteria. Therefore, antibiotic decontamination is a reliable method for sterilisation of AM and the resultant antibiotic reservoir is effective against gram-positive and –negative bacteria.

Antimicrobial efficiency and stability of two decontamination solutions

Two decontamination solutions, commercially produced BASE•128 and laboratory decontamination solution (LDS), with analogous content of antibiotic and antimycotic agents, were compared in their antimicrobial efficiency and stability (pH and osmolarity). Both solutions were compared immediately after thawing aliquots frozen for 1, 3 or 6 months. Agar well diffusion method was used to test their antimicrobial efficiency against five human pathogens: Staphylococcus aureus, Pseudomonas aeruginosa, Proteus mirabilis, Escherichia coli and Enterococcus faecalis. The difference in the inhibition of growth between the two decontamination solutions was mostly not statistically significant, with few exceptions. The most pronounced difference between the LDS and BASE•128 was observed in their decontamination efficacy against E. coli and E. faecalis, where the LDS showed to be more efficient than BASE•128. The osmolarity value of LDS decreased with cold-storage, the osmolarity values of the BASE•128 could not be measured as they were below the range of the osmometer. Slight changes were found in pH of the less stable LDS solution, whose pH increased from initial value 7.36 ± 0.07 to 7.72 ± 0.19 after 6 m-storage. We verified that BASE•128 and LDS are similarly efficient in elimination of possible placental bacterial contaminants and may be used for decontamination of various tissues.

High-resolution optical coherence tomography in a case of descemetocele managed with amniotic membrane transplantation

Amniotic membrane transplantation is a useful in the management of corneal melts and descemetocele. We describe high-resolution anterior segment optical coherence tomography (OCT) (Optovue) in a patient with descemetocele who was managed surgically with amniotic membrane transplantation. A 60-year-old female presented with a corneal melt in the right eye. She was a case of rheumatoid arthritis and was on systemic treatment with immunomodulators. Slit lamp examination revealed a severe thinning paracentrally. High-resolution OCT was performed at the site of descemetocele. She underwent amniotic membrane transplantation using fibrin glue and bandage contact lens application. At 6 weeks postoperative, the bandage contact lens was removed. The area of thinning healed with scarring. OCT at the healed site revealed stable surface and an increase in stromal thickness to 281 μ this case describes the utility of amniotic membrane in the healing of sterile corneal melts by providing tectonic support and its integration in the stroma. The stromal healing and increased thickness at the site of descemetocele could be delineated on high-resolution OCT imaging.

Comparison of impact of two decontamination solutions on the viability of the cells in human amnion

Human amniotic membrane (HAM) is used as an allograft in regenerative medicine or as a source of pluripotent cells for stem cell research. Various decontamination protocols and solutions are used to sterilize HAM before its application, but little is known about the toxicity of disinfectants on HAM cells. In this study, we tested two decontamination solutions, commercial (BASE·128) and laboratory decontamination solution (LDS), with an analogous content of antimycotic/antibiotics for their cytotoxic effect on HAM epithelial (EC) and mesenchymal stromal cells (MSC). HAM was processed in a standard way, placed on nitrocellulose scaffold, and decontaminated, following three protocols: (1) 6 h, 37 °C; (2) 24 h, room temperature; (3) 24 h, 4 °C. The viability of EC was assessed via trypan blue staining. The apoptotic cells were detected using terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL). The mean % (±SD) of dead EC (%DEC) from six fresh placentas was 12.9 ± 18.1. Decontamination increased %DEC compared to culture medium. Decontamination with BASE·128 for 6 h, 37 °C led to the highest EC viability (81.7%). Treatment with LDS at 24 h, 4 °C resulted in the lowest EC viability (55.9%) in the set. MSC were more affected by apoptosis than EC. Although the BASE·128 expresses lower toxicity compared to LDS, we present LDS as an alternative decontamination solution with a satisfactory preservation of cell viability. The basic formula of LDS will be optimised by enrichment with nutrient components, such as glucose or vitamins, to improve cell viability.

Amniotic membrane in ophthalmology: properties, preparation, storage and indications for grafting-a review

The use of amniotic membrane in ophthalmic surgery and other surgical procedures in the fields of dermatology, plastic surgery, genitourinary medicine and otolaryngology is on the increase. Furthermore, amniotic membrane and its epithelial and mesenchymal cells have broad use in regenerative medicine and hold great promise in anticancer treatment. Amniotic membrane is a rich source of biologically active factors and as such, promotes healing and acts as an effective material for wound dressing. Amniotic membrane supports epithelialization and exhibits anti-fibrotic, anti-inflammatory, anti-angiogenic and anti-microbial features. Placentas utilised in the preparation of amniotic membrane are retrieved from donors undergoing elective caesarean section. Maternal blood must undergo serological screening at the time of donation and, in the absence of advanced diagnostic testing techniques, 6 months postpartum in order to cover the time window for the potential transmission of communicable diseases. Amniotic membrane is prepared by blunt dissection under strict aseptic conditions, then is typically transferred onto a nitrocellulose paper carrier, usually with the epithelial side up, and cut into multiple pieces of different dimensions. Amniotic membrane can be stored under various conditions, most often cryopreserved in glycerol or dimethyl sulfoxide or their mixture with culture medium or buffers. Other preservation methods include lyophilisation and air-drying. In ophthalmology, amniotic membrane is increasingly used for ocular surface reconstruction, including the treatment of persistent epithelial defects and non-healing corneal ulcers, corneal perforations and descemetoceles, bullous keratopathy, as well as corneal disorders with associated limbal stem cell deficiency, pterygium, conjunctival reconstruction, corneoscleral melts and perforations, and glaucoma surgeries.

Human Amniotic Membrane-Derived Products in Sports Medicine: Basic Science, Early Results, and Potential Clinical Applications

BACKGROUND

Amniotic membrane (AM)-derived products have been successfully used in ophthalmology, plastic surgery, and wound care, but little is known about their potential applications in orthopaedic sports medicine.

PURPOSE

To provide an updated review of the basic science and preclinical and clinical data supporting the use of AM-derived products and to review their current applications in sports medicine.

STUDY DESIGN

Systematic review.

METHODS

A systematic search of the literature was conducted using the Medline, EMBASE, and Cochrane databases. The search term amniotic membrane was used alone and in conjunction with stem cell, orthopaedic, tissue engineering, scaffold, and sports medicine.

RESULTS

The search identified 6870 articles, 80 of which, after screening of the titles and abstracts, were considered relevant to this study. Fifty-five articles described the anatomy, basic science, and nonorthopaedic applications of AM-derived products. Twenty-five articles described preclinical and clinical trials of AM-derived products for orthopaedic sports medicine. Because the level of evidence obtained from this search was not adequate for systematic review or meta-analysis, a current concepts review on the anatomy, physiology, and clinical uses of AM-derived products is presented.

CONCLUSION

Amniotic membranes have many promising applications in sports medicine. They are a source of pluripotent cells, highly organized collagen, antifibrotic and anti-inflammatory cytokines, immunomodulators, and matrix proteins. These properties may make it beneficial when applied as tissue engineering scaffolds, improving tissue organization in healing, and treatment of the arthritic joint. The current body of evidence in sports medicine is heavily biased toward in vitro and animal studies, with little to no human clinical data. Nonetheless, 14 companies or distributors offer commercial AM products. The preparation and formulation of these products alter their biological and mechanical properties, and a thorough understanding of these differences will help guide the use of AM-derived products in sports medicine research.

Human amniotic membrane transplantation: Different modalities of its use in ophthalmology

The amniotic membrane (AM) is the inner layer of the fetal membranes and consist of 3 different layers: the epithelium, basement membrane and stroma which further consists of three contiguous but distinct layers: the inner compact layer, middle fibroblast layer and the outermost spongy layer. The AM has been shown to have anti-inflammatory, anti-fibrotic, anti-angiogenic as well as anti-microbial properties. Also because of its transparent structure, lack of immunogenicity and the ability to provide an excellent substrate for growth, migration and adhesion of epithelial corneal and conjunctival cells, it is being used increasingly for ocular surface reconstruction in a variety of ocular pathologies including corneal disorders associated with limbal stem cell deficiency, surgeries for conjunctival reconstruction, as a carrier for ex vivo expansion of limbal epithelial cells, glaucoma surgeries and sceral melts and perforations. However indiscriminate use of human AM needs to be discouraged as complications though infrequent can occur. These include risk of transmission of bacterial, viral or fungal infections to the recipient if the donors are not adequately screened for communicable diseases, if the membrane is not processed under sterile conditions or if storage is improper. Optimal outcomes can be achieved only with meticulous case selection. This review explores the ever expanding ophthalmological indications for the use of human AM.

Bacterial contamination of amniotic membrane in a tissue bank from Iran

Human Amniotic Membrane (AM) transplantation can promote tissue healing and reduce inflammation, tissue scarring and neovascularization. Homa Peyvand Tamin (HPT) tissue bank has focused on manufacturing human cell and tissue based products including AM. The purpose of this study is to evaluate and identify bacterial contamination of AMs that is produced by HPT for several ophthalmic applications. From July 2006 to April 2011, 122 placentas from cesarean sections were retrieved by HPT after obtaining informed consent from the donors. Besides testing donor's blood sample for viral markers, microbiological evaluation was performed pre and post processing. During tissue processing, decontamination was performed by an antibiotic cocktail including; Gentamicin, Ceftriaxone and Cloxacillin. Of 271 cesarean section AM donors who were screened as potential donors, 122 were accepted for processing and assessed for microbiological contamination. Donors' age were between 21 and 41 years (Mean = 27.61 ± 0.24). More than 92% of mothers were in their first or second gravidity with full term pregnancies. The most prevalent organisms were Staphylococci species (72.53%). After processing, contamination rates markedly decreased by 84.62% (p value = 0.013). According to our results, most of bacterial contaminations were related to donation process and the contamination pattern suggests procurement team as a source. Therefore we recommend that regular training programs should be implemented by tissue banks for procurement staff. These programs should focus on improved donor screening and proper aseptic technique for tissue retrieval. We also suggest that tissue banks should periodically check the rate and types of tissue contaminations. These data help them to find system faults and to update processing methods.

Amniotic membrane transplantation: An option for ocular surface disorders

BACKGROUND

Ocular surface disorders (OSD) are challenging to treat. They can introduce serious morbidity and might even lead to visual loss. In such situations, keratoplasty remains the last option. Amniotic membrane transplantation (AMT) has been shown to be effective in the management of ocular surface pathologies. The aim of the study was to assess the efficacy of AMT for various indications of OSD.

MATERIALS AND METHODS

Experience of AMT in 65 patients with different OSD was evaluated. The aim of AMT was to achieve symptomatic relief, reduced inflammation, recurrence, and corneal haze; improve epithelization, stromal healing and visual acuity; and delay keratoplasty. Fresh amniotic membrane was used in all cases by a single surgeon. Follow-up and observations were done to evaluate success of achieving the goal.

RESULTS

Indications for AMT included primary and recurrent pterygium, various types of corneal ulcers (non-healing ulcer, descemetocele, corneal thinning and perforation), spheroidal degenerations, chemical burn and bullous keratopathy. The aim of AMT was different in different etiological indications. Postoperative follow-up was between 6 and 18 months. Success and complication rate were observed. Symptomatic relief (reduced pain and redness) was seen in patients with various corneal ulcers, chemical burn and bullous keratopathy. Improved epithelialization and stromal healing was noted in corneal ulcer cases. In spheroidal degenerations, keratectomy with AMT improved vision. Recurrence of pterygium was low (4.61%); graft failure in the form of graft rejection was seen in only 3.07% cases of acute keratitis. Corneal vascularization (4.61%) was present but not severe enough to hamper vision. Success in gaining intended effect was the most significant result with AMT.

CONCLUSION

AMT in various ocular surface pathologies shows success in achieving the goal of symptomatic relief, improved epithelialization, stromal healing and vision. Reduction in inflammation, corneal haze and recurrence of original disease is achieved with minimum complications.

Ocular surface reconstruction using amniotic membrane following excision of conjunctival and limbal tumors

PURPOSE

To report the clinical results of patients treated by preserved human amniotic membrane transplantation (AMT) following the removal of conjunctival and limbal tumors.

METHODS

Retrospective noncomparative interventional case series of 9 patients (9 eyes) who underwent AMT after removal of conjunctival and limbal tumors with lesion-free margins and perilesional cryotherapy.

RESULTS

The excised tumors were histopathologically examined and included 2 squamous cell carcinomas, 2 papillomas, and 5 nevi. Bulbar conjunctiva was involved in all of the eyes, limbus and cornea in 7 and 3 eyes, respectively. The mean extent of the limbal involvement was 4 clock hours (range 2-9, SD 2.4); the average diameter of the base of the tumor was 12.8 mm (range 10-20, SD 4.4). The mean follow-up time was 38 months (range 13-60, SD 15). No surgical or early postoperative complications were observed. In all eyes, complete healing of the tissue defect occurred, resulting in a stable, wet, and noninflamed epithelium. All eyes demonstrated a smooth ocular surface except one with a clinically insignificant symblepharon after the excision of a squamous cell carcinoma. Superficial peripheral corneal vascularization and opacification as a sign of partial limbal stem cell deficiency developed in 2 eyes. In one case, a recurrence of conjunctival papilloma was diagnosed after a 3-year follow-up.

CONCLUSIONS

Amniotic membrane transplantation is an effective method of reconstruction following a conjunctival and limbal tumor excision and cryotherapy of surgical wound margins. In most cases, complete healing of an ocular surface can be achieved without any clinically significant complications.

Nonpreserved human amniotic membrane transplantation for conjunctival reconstruction after excision of extensive ocular surface neoplasia

PURPOSE

To report our experience on the use of nonpreserved human amniotic membrane transplantation (AMT) in ocular surface reconstruction after excision of extensive ocular surface neoplasia (OSN).

DESIGN

Prospective noncomparative interventional case series.

PARTICIPANTS

In all, 10 eyes of 10 consecutive patients with extensive OSN involving various areas of limbus, conjunctiva, and cornea (conjunctival carcinoma in situ, four eyes; squamous cell carcinoma, three eyes; malignant melanoma, two eyes; conjunctival-orbital lymphangioma, one eye) were included in this prospective noncomparative interventional case series. After excision of the neoplasia with 3-4 mm tumour-free margins, double freeze-thaw cryotherapy was applied to the margins of the remaining conjunctiva, and nonpreserved human amniotic membrane graft was sutured to the adjacent conjunctiva using 8/0 vicryl sutures and cornea using 10/0 nylon sutures, with the epithelial side facing up to cover the bare sclera and cornea. Postoperatively, topical corticosteroids were used for 3 months.

RESULTS

After tumour excision and AMT, a satisfactory result with a wet, stable conjunctiva, and rapid and complete healing was observed in all eyes. Over a mean follow-up of 10.0 months (range, 6-27 months), all but one eye remained free of tumour recurrence. In one eye with conjunctival melanoma, there was a small recurrence, which was treated with excision and cryotherapy. Treatment complications were partial stem cell deficiency in two eyes and symblepharon formation in one eye. Immune graft rejection was not encountered.

CONCLUSION

Nonpreserved human AMT appears to be useful for reconstruction of ocular surface following excision of extensive OSN.

Silica gel dessication of amniotic membrane with related epithelium cells for ocular surface reconstruction

Cornea reparative regeneration when in various pathological states needs creating certain conditions to intensify the potential of regional stem cells mitotic activity.

AIMS OF THE RESEARCH

To find out the degree of the epithelium AM preservation after preliminary processing and conservation by means of dehydration over silica gel with further sterilization; to study the effectiveness of clinical treatment of AM conserved in the surroundings with vital ability epithelium and AM dried over silica gel.

MATERIALS AND METHODS

There was carried out an investigation of 18 samples of native amnion treated with antibiotics and 18 total surface amnion samples conserved by drying over silica gel and then sterilized by gamma rays. Clinical experiments were carried out on patients with severe chemical and thermal burns--18 people (21 eyes). After the burn trauma all the patients underwent the standard procedure of necrectomy, the covering of the eyeball with amniotic membrane dried over silica gel.

CONCLUSION

The drying out of the amniotic membrane over silica gel on frames without being fixed on nitrocellulose paper makes the process of the amniotic membrane conservation simpler and makes it possible to preserve its unique biological qualities. The effectiveness of the regeneration of epithelium tissue of the eyeball surface with amniotic membrane dried over silica gel without the vital capacity cells of the epithelium layer is analogous to the regeneration of epithelium cells with amniotic membrane with vital capacity cells. With eye burns AM coverage hinders the formation of rough conjunctiva cicatrix, provides a favorable out-of-cell matrix substrate for epithelium migration and leads to quicker regeneration of one's own epithelium, makes further visual rehabilitation simpler.

Efficacy of Systemic Cyclosporine A and Amniotic Membrane on Rabbit Conjunctival Limbal Allograft Rejection

PURPOSE

To evaluate the effect of intramuscular cyclosporine A (CsA) and amniotic membrane (AM) on conjunctival limbal allograft survival in a rabbit model.

METHODS

Eighty-two female rabbits (59 New Zealand white rabbits, 23 Dutch pigmented rabbits) were used. The New Zealand white rabbits were divided into 4 treatment groups: group 1 (n=13), conjunctival limbal autograft transplantation; group 2 (n=12), conjunctival limbal allograft transplantation without additional treatment; group 3 (n=18), conjunctival limbal allograft transplantation and human AM; and group 4 (n=16), conjunctival limbal allograft transplantation and systemic CsA (10 mg/kg/day intramuscularly). The 23 Dutch pigmented rabbits were used as limbal stem cell allograft donors. The rejection index, the mean survival time, and the rejection rates were calculated for each group.

RESULTS

After 28 days of follow-up, there were no episodes of limbal rejection in groups 1 and 4, whereas the rejection rate was 100% in groups 2 and 3. There was no significant difference in mean survival time of the rejected grafts between groups 2 and 3.

CONCLUSIONS

A model of rejection of conjunctival limbal transplantation was developed in the rabbit. Intramuscularly injected CsA effectively prevents limbal allograft rejection. Human AM is not useful for this purpose.

Incidence of microbial infection after amniotic membrane transplantation

OBJECTIVE

To report the incidence and characteristics of microbial infection following amniotic membrane transplantation (AMT).

METHODS

We retrieved the clinical and microbiological records of a total of 326 patients undergoing AMT from January 1994 to February 2001 at Bascom Palmer Eye Institute to determine the incidence and characteristics of post-AMT infections with respect to the interval between AMT and the time of microbial culturing, types of organisms, and clinical outcomes and to correlate these infections with the microbiologic results of AM storage media submitted immediately after AMT and the underlying ocular diagnosis.

RESULTS

We subdivided these 326 patients into two groups: 76 patients (from January 1994 to June 1998) used AM prepared from a research laboratory and did not submit AM storage media for culture under an Institutional Review Board-approved protocol, and 250 patients thereafter used AM obtained from a commercial source and routinely submitted AM storage media for culture. A total of 11 culture-positive infections (3.4%) were identified, and among them 7 infections (9.2%) were from the first group, and 4 (1.6%) were from the second group (P = 0.004). All 4 infections (5.2%) occurring within 1 month after AMT were exclusively from the first group (P = 0.003). All AM storage media from the second group were culture negative. Gram-positive organisms were the most frequent isolate (64%). Infections were not correlated with the underlying ocular diagnosis.

CONCLUSIONS

AMT is a safe method for ocular surface reconstruction with a very low rate of microbial infections, especially if AM is prepared according to Good Tissue Banking Practice set forth by FDA. Gram-positive isolates seem to be the most frequent isolates in infections after AMT.

Staphylococcus epidermidis adherence to human amniotic membrane and to human, rabbit, and cat conjunctiva

PURPOSE

To evaluate Staphylococcus epidermidis adherence to human amniotic membrane (HAM) and compare it with S epidermidis adherence to human, rabbit, and cat conjunctiva in vitro.

SETTING

Research laboratory, Loyola University Medical Center, Maywood, Illinois, USA.

METHODS

Commercially available HAM (N = 3) was used. Conjunctival specimens from humans, rabbits, and cats (n = 3 each) were processed similarly to HAM. The tissues were exposed to S epidermidis (3 x 10(8) colony-forming units per milliliter) for 0, 5, 30, and 90 minutes, rinsed in sterile saline, and processed for light, scanning (SEM), and transmission (TEM) electron microscopy. Scanning electron microscopy (x2000) was used to quantify adherent bacteria/mm(2) of tissue (SEM photographs = 144).

RESULTS

The following mean levels (+/- SD) of adherent S epidermidis/mm(2) were found at 0, 5, 30, and 90 minutes: HAM, 3833 +/- 1570, 9060 +/- 2512, 15,431 +/- 10,752, and 30,315 +/- 14,803, respectively; human conjunctiva, 1493 +/- 672, 7218 +/- 3179, 17,273 +/- 7168, and 19,861 +/- 9624, respectively; rabbit conjunctiva, 3385 +/- 5074, 14,386 +/- 14,569, 15,283 +/- 13,679, and 20,113 +/- 24,016, respectively; and cat conjunctiva, 4032 +/- 2240, 12,345 +/- 3413, 8512 +/- 4032, and 19,214 +/- 5584, respectively. No statistically significant differences were found at any time point (P>.16).

CONCLUSION

There was no statistically significant difference in the adherence of S epidermidis to HAM and to human, rabbit, and cat conjunctiva. Bacterial adherence to HAM may be clinically significant.