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Infection of prosthetic vascular grafts presents as a significant complication of peripheral arterial reconstruction with high morbidity and mortality. Acute graft infection is often associated with Staphylococcus aureus or Pseudomonas aeruginosa contamination and presents within days to weeks of revascularization. Late onset infections typically present months to years post-implantation. Staphylococcus epidermidis is the predominant isolate found in these late occurring infections and slime-positive strains are often recovered from culture. Multiple factors potentiate these late infections and complicate management.

BACKGROUND/OBJECTIVE: Superficial incisional site infections (SIS) account for 40% to 60% of all surgical site infections. Traditional efforts to reduce SIS infections focus on skin antisepsis, timely and appropriate surgical prophylaxis, and meticulous wound care. Selective predicated antiseptic-impregnated biomedical devices have demonstrated microbiological and clinical efficacy by reducing microbial surface colonization and lowering the risk of nosocomial infection in medical/surgical patient populations. A triclosan-impregnated (TI) vicryl suture was studied under in vitro conditions to evaluate its effectiveness at preventing microbial adherence. METHODS: 1-cm segments (5X) of triclosan-impregnated (3–0) vicryl suture material were exposed to MRSA, glycocalyx-producing S. epidermidis , VRE, E. coli , and Pseudomonas aeruginosa , acquired from surgical site infections. The TI segments were exposed to one of two standardized inoculum, 2.0 and 5.0 log10 CFU/mL at 5- and 120-second exposure times. The TI segments were sonicate, serial diluted, and quantitative cultures performed to determine CFU per cm suture segment. Control studies were performed using non-impregnated vicryl (3–0). RESULTS: The TI-impregnated device compared to non-impregnated controls was effective at reducing or preventing microbial adherence against all gram-positive and gram-negative clinical isolates (p Pseudomonas aeruginosa and an exopolysaccharide-producing strain of S. epidermidis , regardless of inoculum challenge or exposure time. CONCLUSION: These findings suggest that TI sutures are effective at preventing microbial adherence of selected nosocomial pathogens and by extension may reduce the risk of SIS infection in at-risk surgical populations. Additional studies are warranted validating the antimicrobial and clinical efficacy of this innovative device in surgical patients.

The cationic reagent ruthenium red (RR) has been used to enhance ultrastructural preservation and staining of the bacterial glycocalyx. Lysine was needed in prefixation to preserve the polysaccharide glycocalyx material for the gram-positive, coagulase-negative staphylococci species. The inclusion of lysine in the prefixative of glutaraldehyde (GA)-RR enhanced observation of elaborate and extensive glycocalyx material. However, prefixation in 75 mM lysine in GA-RR is restricted to 20 minutes because gelling or solidification frequently occurs at longer intervals resulting in loss of sample. To improve the utility of this approach, the effect of the Karnovsky ratio of 2% paraformaldehyde to 2.5% GA was investigated.Cells of gram-positive, coagulase-negative staphylococci species, Staphylococcus epidermidis RP62, a polysaccharide producer, and Staphylococcus epidermidis M187-SN3, a polysaccharide negative mutant, were recovered from frozen storage and grown on blood agar plates. After 24 hours, cells were transferred to trypticase soy broth for 18 hours, and incubated at 35°C. Half of the cells were prefixed in 75 mM L-lysine, 0.075% RR, 2.5% GA in 0.1 M sodium cacodylate pH 7.2 for 20 minutes.

Specimens from 152 abdominal infections were examined to determine which groups of endogenous bacteria participate in infection emanating from different sites in the gastrointestinal tract. A notable finding was the predominance of anaerobic microflora from infections of ischemic versus perforated small bowel. Empiric antibiotic treatment for ischemic bowel should include focused coverage for anaerobes.

Previous studies in our laboratory have questioned the efficacy of antibiotic impregnated bone cement to prevent staphylococcal colonization of orthopaedic implants following surgery. Teicoplanin a glycopeptide antibiotic with excellent anti-staphylococcal activity was added to polymethylmethacrylate in concentrations ranging from 2-5 wt%. Five staphylococcal strains recovered from orthopaedic implant infections were chosen for study: 2-Staphylococcus aureus and 3-Staphylococcus eoidermidis. Two of the staphylococcal isolates were identified as producing an exopolysaccharide slime following alcian blue staining with lysine. The in vitro release of antibiotic from the resin surface was determined by biological assay at 0, 12, 24, 48, 96 and 10 days post-study. Mean teicoplanin concentrations ranged from 200 to 430 ug/ml at 0 hour and 22 to 50 ug/ml at 10 days post-study. Teicoplanin impregnated and drug free resin controls were exposed to standardized inoculum (5.0 log10 colony forming units/ml) of the staphylococcal clinical isolates and incubated at 35°C in physiologic buffered saline with 0.25% dextrose.

The gram-positive coagulase-negative staphylococci are opportunistic organisms important in latent infection associated with prosthetic biomaterials. Their highly charged polysaccharide glycocalyx, or slime, aids in proliferation of bacteria on surfaces after an initial adhesion event, possibly at the time of surgical insertion. The cationic reagents, ruthenium red (RR) and alcian blue (AB), in en bloc procedures have aided visualization of the polysaccharide glycocalyx material in TEM or SEM applications. Further, enhancement of RR preservation or staining of slime by inclusion of lysine in a prefixation stage has been observed. The effect of lysine with and without RR and AB on preservation/staining of the staphylococci glycocalyx is investigated further in this study.Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis RP62 (RP62) and Staphylococcus hominis SP2 (SP2) were cultured in trypticase soy broth for 18 hrs at 35°C, following recovery from frozen storage and plating on blood agar plates for 24 hrs. Cells with 75mM lysine in the prefixation were incubated for 20 minutes with 2.5% glutaraldehyde (GA), 2.5% GA and 0.075% RR, or 2.5% GA and 0.075% AB, respectively.

Acquisition of an infection following insertion of a biomaterial device is of great concern to surgeons. The costs associated with these infections are great, both to patients and the institution in which they occur. The concept of implanting a biomaterial resistant to bacterial adherence and colonization has been shown to be valuable in preventing infection and treatment of tissue contamination. The following investigation was conducted to study the efficacy of three bonding methods on the release of antibiotic and its impact on microbial colonization of AICD (Figure 1) patch material. Cefazolin, ciprofloxacin, and teicoplanin were bonded to silicone/titanium AICD patches using either Tridodecylmethylammonium chloride (TDMAC) antibiotic bonding, Silver-antibiotic bonding or TDMAC silver-antibiotic bonding. In vitro drug levels were determined by biological assay. Antibiotic bonded and drug-free (control) AICD material was exposed to standardized inoculum of staphylococcal test isolates. At 4, 8, 24 and 48 hours microbial colonization was determined following ultrasonic oscillation.

Diabetic visceral neuropathy is the most common acquired autonomic neuropathy. Most of the previous studies on the effect of diabetes on the GI tract have focused mainly on extrinsic parasympathetic and sympathetic innervation. The few studies which explored the effects of diabetes on the myenteric and submucosal plexi have reported normal neural morphology even in viscera that were clearly affected by diabetic autonomic neuropathy. The present study was designed to characterize changes in the enteric nervous system in different models of diabetes in rats, and to determine whether treatment with insulin or pancreas transplantation would have any affect on the degenerative process. Specimens from the proximal, middle, and distal small bowel as well as the colon were obtained from Sprague-Dawley streptozocin-induced diabetic rats, from BB/WOR genetically induced diabetic rats, insulin treated streptozocin-induced diabetic Lewis rats, and streptozocin-induced diabetic Lewis rats transplanted with a heterotopic pancreatic isograft. All specimens were obtained one month after induction of diabetes and paired biopsies were also obtained from age matched controls (Fig. 1). Tissues were processed fore lectron microscopic and immunohisto chemical studies (for the detection of substance P and VIP).

While the overall incidence of infection following joint and hip replacement is low, infection when it occurs is often catastrophic and requires replacement of the contaminated prosthetic. The addition of antibiotics to polymethylmethacrylate (PMM) in total joint and hip replacements has been suggested to reduce the risk of post-surgical infection. However, no studies have demonstrated the effect of antibiotic impregnation on microbial adherence and colonization of the resin surface. In the present study cefazolin, tobramycin, or ciprofloxacin were added to the polymethylmethacrylate prior to polymerization and exposed to one of four microbial strains: Staphylococcus aureus (LDE26), Staphylococcus epidermidis (RP62 mucin + or SP2 mucin -) and Escherichia coli (PB103) for a period of 48 hours in PBS with 0.25% dextrose. All bacteria were sensitive to the three test drugs. At 2, 8, 24, and 48 hours a resin block was removed from the test solution, rinsed (3x) and ultrasonically oscillated to remove adherent bacteria. The sonicate was serially diluted, plated to antibiotic free media and microbial quantitation expressed as the log10 colony forming units (cfu) per mg of bone cement. Antibiotic free resin blocks were run in parallel with impregnated samples.

The coagulase negative staphylococci (CNS) are a ubiquitous group of microorganisms which comprise a major component of the microbial flora of the skin and adjacent glands. Historically, the CNS were viewed as insignificant contaminants with little clinical importance. However, over the last decade these organisms have emerged as important etiologic agents of biomaterial associated infections. Furthermore, many of the Staphylococcus epidermidis strains recovered from catheter or prosthetic infections exhibit the capacity to produced an extracellular capsular polysaccharide (slime) which is viewed as an important factor in biomaterial adherence and persistence. Bacterial capsular material is composed of hydrated polysaccharides and has been visualized by transmission electron microscopy when lysine is added to the fixation protocol. This study reports on the use of a lysine-ruthenium redglutaraldehyde fixation technique for visualizing the polysaccharide capsule on two coagulase negative staphylococcal reference strains, S. epidermidis RP62A (ATCC 35984) and S. hominis SP2 (ATCC 35982).