Role of an intraperitoneal catheter implant in the pathogenesis of experimental Staphylococcus epidermidis peritoneal infection in renal failure mice

The influence of a permanent peritoneal catheter implant on the response of renal failure and control mice to peritoneal inoculation with 10(6) colony-forming units (CFU) Staphylococcus epidermidis was assessed 48 h after bacterial challenge. Two weeks after the surgical induction of renal failure or sham surgery, a segment of a peritoneal dialysis catheter was implanted entirely within the confines of the peritoneal cavity of mice. One month later peritoneal S. epidermidis inoculation was performed by transcutaneous injection through the abdominal wall either directly into the peritoneal cavity (i.p.) or via the catheter lumen (i.c.). Following i.p. inoculation, minimal bacterial growth was recovered from the peritoneal structures of all mice, including the peritoneal catheter. In contrast, following i.c. S. epidermidis challenge, the catheter site remained heavily colonized while peritoneal washings and parietal peritoneum again presented minimal bacterial recoveries. S. epidermidis recovery from the catheter site of renal failure mice was significantly greater than from the respective site of sham-operated controls. Scanning electron microscopy of catheter segments recovered from mice following i.c. inoculation revealed single cocci or microcolonies associated with the catheter surface and differential leukocyte counts of fluid aspirated from the catheter lumen revealed evidence of acute inflammation. Signs of inflammatory processes in peritoneal washings and peripheral blood, however, were not observed. These results are discussed in relation to S. epidermidis peritonitis and continuous ambulatory peritoneal dialysis.     

Affinity of Staphylococcus epidermidis to various prosthetic graft materials.

BACKGROUND: Abdominal wall hernias have always been a major problem for general surgeons. The techniques of repairing primary, recurrent, and incisional hernias have evolved throughout the years at an accelerating trend, especially after production of prosthetic graft materials. Although looked upon with suspicion due to infection, fistula formation, and foreign body reaction, prosthetic graft materials are used deliberately in primary and recurrent hernias. The present study was designed to evaluate bacterial adherence to frequently used prosthetic graft materials. MATERIALS AND METHODS: The study was carried out in five different groups with each group consisting of 10 identical samples of the same kind of prosthetic graft material. The prosthetic graft materials used in the study were polypropylene, polyglactin 910, polyester fibers, steel, and polytetrafluoroethylene (PTFE). These prosthetic graft materials were incubated in vitro with a Staphylococcus epidermidis strain which was ++++ adhesion positive. The degree of adhesion of S. epidermidis to prosthetic graft materials was assessed by the ELISA method. RESULTS: Vicryl grafts showed significantly minimal bacterial adhesion whereas PTFE grafts tended to have more adhesion but this did not reach a statistical significance. Other graft materials did not show any difference for bacterial adhesion (Table 3). CONCLUSION: These results suggest that in vitro S. epidermidis adhesion to Vicryl grafts is less than other types of prosthetic graft materials (P < 0.05 for all comparisons). Further in vitro and in vivo studies are required to confirm these results and to understand the complex interactions among bacteria, graft material, microenvironment, and surgical technique.     

Linezolid alone and in combination with rifampicin prevents experimental vascular graft infection due to methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis

BACKGROUND: In this report we describe the in vivo antibacterial activity of linezolid in an experimental graft infection model in rats and compare it with teicoplanin. The objective of this study was also to determine the effects of the interaction of linezolid when it was combined with rifampicin and test this effect against strains of methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis. MATERIALS AND METHODS: Graft infections were established in the subcutaneous tissue of 130 Wistar rats by implantation of Dacron grafts followed by a topical inoculation with 2 x 10(7) CFU of clinical isolates of MRSA and MRSE. The study included a control group and six groups for each of the staphylococcal strains: an inoculated group that did not receive any antibiotic prophylaxis, two inoculated groups that received intraperitoneal prophylaxis with teicoplanin or linezolid alone, an inoculated group that received rifampicin-soaked grafts, and two inoculated groups that received a combination prophylaxis consisting of intraperitoneal teicoplanin or linezolid and rifampicin-soaked grafts. RESULTS: There was a reduction in the quantitative bacterial graft cultures in all prophylaxis groups when compared with inoculated control groups. There was not a statistically significant difference between linezolid and teicoplanin prophylaxis groups. The best results were obtained by a combination of rifampicin-soaked grafts with linezolid or teicoplanin. CONCLUSIONS: We found no evidence to suggest that linezolid differs from teicoplanin regarding effectiveness in the prevention of prosthetic vascular graft infection. Linezolid plus rifampicin and teicoplanin plus rifampicin are demonstrated to be valuable prophylactic regimens.     

Evaluation of three techniques for documenting Staphylococcus epidermidis vascular prosthetic graft infections

Staphylococcus epidermidis (S. epidermidis) vascular prosthetic graft infections are notoriously hard to detect. Three different techniques of determining whether vascular prosthetic grafts were infected using a dog model were evaluated. Aortic angiograms were compared with nuclear magnetic resonance (NMR) imaging and systemic norepinephrine (NE) kinetics to determine if either newer technique would be more reliable than standard angiograms. Twelve dogs were randomized to control (n = 6) or infected groups (n = 6). All dogs had a 5 cm section of their infrarenal aorta replaced with knitted Dacron vascular prosthetic graft. The grafts in the infected group were contaminated by soaking them in a broth containing S. epidermidis. NE production and clearance rates were calculated for all animals after an infusion of 3H-NE using the steady-state radionuclide tracer methodology. One week following graft insertion, dogs were reanesthetized, and the 3H-NE infusion and measurements were repeated. Standard angiograms and NMR imaging were also performed. Once all tests were performed, the prosthetic grafts were removed for cultures. Comparisons between the initial and final norepinephrine measurements for each group were made using the nonparametric Wilcoxon two-sample test, while comparisons between the groups were made by chi square or the Student's t test. Angiogram results were similar for control and infected animals. Angiograms missed disruption of the proximal anastomosis found in three of the six infected dogs at graft removal. None of the six control animals, while five of the six infected animals, had localized areas of high signal intensity on NMR imaging (P less than 0.01) suggesting abscess formation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Foreign-body-associated experimental osteomyelitis induced with Bacteroides fragilis and Staphylococcus epidermidis in rabbits

Bacteroides fragilis and Staphylococcus epidermidis, alone and in combination, were used to induce foreign-body-associated osteomyelitis in a rabbit model. In this model, a catheter, used as a foreign body, was implanted into the medullary cavity of the tibia. Only two of five animals infected with S. epidermidis alone developed culture-positive osteomyelitis, whereas all three animals infected with B. fragilis alone developed osteomyelitis. All six animals infected with both microorganisms developed culture-positive osteomyelitis. Roentgenographic and histologic evaluations confirmed the diagnosis of osteomyelitis. Transmission and scanning electron microscopy showed that when the two microorganisms are involved in a mixed infection, S. epidermidis predominates on the foreign body and B. fragilis predominates in the infected bone and marrow.     

Gelatin-sealed polyester resists Staphylococcus epidermidis biofilm infection.

BACKGROUND: The purpose of this study was to show that gelatin-impregnated polyester grafts inhibit Staphylococcus epidermidis biofilm infection in a canine model of aortic graft interposition. A clinically native species and two engineered strains, which differed in slime and adhesin antigen components, were compared to determine differential gelatin and slime interactions. METHODS: In vitro bacterial graft colonization was validated by immersion of graft segments in inoculating solutions (10(6) colony forming units/ml) of a clinically native species RP62A and two genetically engineered S. epidermidis species, M187sn3 (SN3: slime and adhesin negative) or M187sp11 (SP11: slime and adhesin positive), for 18 h at 23 degrees C. The grafts were washed, sonicated, and cultured to assess in vitro bacterial graft adherence. Grafts similarly inoculated were placed as aortic interposition grafts in dogs. Three sterile grafts were implanted as controls. Grafts were excised after 6 weeks and cultured for bacterial growth as in the in vitro study. Infection was defined by a positive culture in the excised grafts. Data were analyzed with nonparametric statistical methods. RESULTS: In vitro bacterial graft adherence in colony forming units per milliliter was similar at 18 h postsonication for RP62A (8 x 10(4) +/- 1 x 10(4)), SN3 (7 x 10(4) +/- 2 x 10(4)), and SP11 (6 x 10(4) +/- 2 x 10(4)) (P = NS). Only one of five grafts inoculated with RP62A was culture positive after 6 weeks. No grafts inoculated with the engineered strains SN3 or SP11 were culture positive after explanation. CONCLUSION: In vitro bacterial inoculation of gelatin-impregnated polyester was similar among the species and not dependent upon the presence of slime and adhesin components. Gelatin-impregnated polyester grafts demonstrated in vivo resistance to coagulase-negative staphylococcal biofilm infection.     

An in vitro study of the properties influencing Staphylococcus epidermidis adhesion to prosthetic vascular graft materials.

This study examines the influence of the properties of various vascular graft materials on the bacterial adherence process of two different strains of Staphylococcus epidermidis (mucous and normucous producing). Dacron grafts (both knitted and woven), Teflon grafts, and Dacron grafts coated with one and two layers of silicone were studied because these materials differ significantly in porosity, hydrophobicity, and surface charge (zeta potential). Graft segments were immersed in 3H-labeled bacteria solution for periods ranging from 5 to 180 minutes and liquid scintillation techniques were used to quantify bacterial adherence. The porous knitted Dacron material had a significantly higher rate of bacterial adherence than either the woven Dacron or Teflon (p less than 0.05). Silicone coating (either one or two layers) reduced adherence by a factor of four for the knitted Dacron (p less than 0.05) and by a factor of two for woven Dacron (p less than 0.05). The mucous producing strain of S. epidermidis displayed significantly better adherence to woven and knitted Dacron than the normucous producing strain, but only when 0.25% dextrose was added to the bacteria solution. These findings indicate that the highly porous knitted Dacron grafts have the highest propensity for bacterial adhesion. Graft materials with the most negative zeta potentials are more resistant to bacterial adherence. Silicone coating of Dacron material significantly changed adherence characteristics, suggesting that this may be a viable strategy for protecting implantable medical devices containing materials to which bacteria readily adhere.     

Crescentic glomerulonephritis associated with totally implantable central venous catheter-related Staphylococcus epidermidis infection

A 59-year-old woman was admitted to our hospital for treatment of acute renal insufficiency. She had been under home intravenous hyperalimentation therapy through a totally implantable central venous catheter for 2 years because of post-radiation enteritis. Clinical examination on admission revealed severe renal insufficiency complicated with hypocomplementemia, marked proteinuria and hematuria. Chest roentgenography demonstrated moderate pulmonary congestion. Hemodialysis was initiated and her pulmonary congestion improved. On the 14th and 21st hospital day, blood culture revealed Staphylococcus epidermidis colonization. Cefazolin was administered and C-reactive protein decreased, however, renal insufficiency and hypocomplementemia did not improve. To investigate the genesis of renal insufficiency, renal biopsy was performed. Light microscopic findings of the kidney revealed severe crescentic glomerulonephritis complicated with moderate tubulointerstitial damage. Immunofluorescence-microscopic findings of the kidney revealed positive IgG, IgM, C3 deposition along the capillary lumen. From these laboratory findings and the clinical course, we diagnosed her renal disease as crescentic glomerulonephritis induced by catheter-related bloodstream infection, and the central venous catheter was removed. After removal, urinary output and hypocomplementemia remarkably improved, however, unfortunately, her renal dysfunction did not improve and maintenance hemodialysis needed to be continued. Although her renal disease was not caused by ventriculo-atrial shunt but by central venous catheter-related bloodstream infection, we supposed that the pathogenesis was a closely similar entity to shunt nephritis.     

A rat model of polypropylene graft infection caused by Staphylococcus epidermidis

BACKGROUND: The aim of this study was to constitute a valid graft infection model with Staphylococcus epidermidis in rats. METHODS: Rats were divided into seven groups. In groups 1 and 2, 2 cm x 2 cm polypropylene grafts were incubated with 10(8) c.f.u./mL slime-positive S. epidermidis at 37 degrees C for 2 and 24 h and were then placed subfascially to the groins of rats. In the third group, naive grafts were placed and 0.5 mL of 3 x 10(7) c.f.u. slime-positive S. epidermidis were injected on the inside of the wounds. Rifampicin (30 mg/kg) in group 4 and teicoplanin (20 mg/kg) in group 5 were applied i.p. to rats with 2-h incubated grafts for prophylaxis. The same prophylactic regimens were given to groups 6 and 7 in which rats were incubated for 24 h. At eighth day, rats were killed and wounds were assessed with macroscopic evaluation and cultures. RESULTS: No death occurred in any of the groups. In groups 1 and 2, 100% infection rates were achieved. However, graft infection was detected in only two (20%) of the rats in group 3 (P = 0.001). Prophylactic application of teicoplanin or rifampicin decreased the infection rates significantly in the short-incubation groups. CONCLUSION: Incubation of polypropylene grafts with slime-producing S. epidermidis for 2 and 24 h in the pre-application period achieved the occurrence of a standardized graft infection. Prophylactic use of teicoplanin and rifampicin decreased the infection rates. We propose to use this reproducible and reliable animal model of graft infection in future studies.     

急性坏死性胰腺炎并发感染的机理研究

目的观察急性坏死性胰腺炎时肠屏障损伤与细菌移位情况,探讨急性胰腺炎继发感染的机理。方法１５只犬于肠道内定植ＰＵＣ１８质粒菌ＪＭ１０９后,分对照组（ｎ＝７）和急性坏死性胰腺炎组（ＡＮＰ,ｎ＝８）。ＡＮＰ组经主胰管注入牛磺胆酸钠和胰蛋白酶制作ＡＮＰ模型。结果ＡＮＰ组较对照组血胰淀粉酶显著升高（Ｐ＜０．０１）;尿中乳果糖／甘露醇比值高出对照组２～１２倍;空、回、盲肠粘膜及肠内容物中大肠杆菌明显增加（Ｐ＜０．０１）,双歧杆菌、乳酸杆菌明显减少（Ｐ＜０．０１、Ｐ＜０．０５）。对照组犬血培养阴性,除２只犬肠系膜淋巴结培养出细菌外,其余脏器培养均阴性。ＡＮＰ组犬血和脏器细菌培养阳性率均为１００％,且每只犬都能检出术前定植于肠道的质粒菌ＪＭ１０９;胰腺腺泡出血、坏死;肠粘膜绒毛破坏;血浆、回肠组织二胺氧化酶活性下降。结论ＡＮＰ时肠粘膜屏障功能严重受损,发生肠道细菌移位,成为继发性胰腺感染的潜在根源。     

Staphylococcus epidermidis ventriculitis treated with vancomycin and rifampin

Two cases of ventriculitis with Staphylococcus epidermidis that failed on therapy with an antistaphylococcal penicillin are presented. Both infections responded to a combination of intravenous and intraventricular vancomycin and rifampin. Vancomycin and rifampin represent an important antibiotic regimen for the management of resistant infections of the central nervous system, especially with those due to S. epidermidis or methicillin-resistant Staphylococcus aureus.     

Risk of methicillin-resistant Staphylococcus aureus prosthetic joint infection in elective total hip and knee arthroplasty following eradication therapy

Re-screening following methicillin-resistant Staphylococcus aureus (MRSA) decolonization will be helpful to minimize the development of prosthetic joint infection among MRSA colonizers.     

Systemic and local antibiotic prophylaxis in the prevention of prosthetic vascular graft infection: an experimental study.

AIM: to determine if local, in addition to systemic antibiotic prophylaxis (compared to that provided by systemic prophylaxis alone) provides additional benefit in terms of reducing graft infection. METHODS: gelatin-sealed Dacron grafts were interposed in the infrarenal aorta of 36 mongrels and inoculated with 1 ml of a S. aureus suspension. Group 1 (control group) received no prophylaxis and were inoculated with 1 ml containing 10(9)cfu/ml. Group 2 (n=6) received systemic prophylaxis (1 g cephamandole) and were inoculated with 10(5) cfu/ml (n=3) or 10(7) cfu/ml (n=3). Group 3 received systemic prophylaxis (1 g cephamandole) and were inoculated with 109 cfu/ml. Group 4 received systemic prophylaxis (2 g cephamandole) and were inoculated with 10(9)cfu/ml. In group 5 and 6 grafts were soaked in a rifampicin solution before use and inoculated with 10(9) cfu/ml. Group 5 received no systemic prophylaxis and group 6 received systemic prophylaxis (1 g cephamandole). Grafts were harvested at 2 weeks, and peritonitis, perigraft abscess, anastomotic disruption and graft occlusion recorded. Swabs were taken of the graft, the perigraft tissues and the peritoneal fluid. Graft segments were incubated in broth medium. RESULTS: inoculation with 10(9) cfu/ml ensured graft infection. Systemic or local prophylaxis alone failed to prevent graft infection. Only systemic and local antibiotic prophylaxis provided significant better results than no prophylaxis at all (p<0.01) and local prophylaxis alone (p<0.05). However, total "graft sterility" was not achieved as bacteriologic analysis of the graft segments showed low bacterial counts (<10 bacteria/graft) in 5 of 6 grafts. CONCLUSION: local and systemic prophylaxis provided more protection as demonstrated by the significant decrease in the incidence of "overt" graft infection. Total "graft sterility" cannot be expected in the case of an overwhelming bacterial challenge.