The Effect of G-CSF in an Experimental MRSA Graft Infection in Mice

Wound infection after prosthetic material implantation is a troublesome complication with an incidence of 2% to 10%. The effect of granulocyte colony-stimulating factor (G-CSF) was studied in an experimental methicillin-resistant Staphylococcus aureus (MRSA) graft infection model. Eighty adult mice were used. Under general anesthesia an abdominal incision of 2 cm in length was performed. A subcutaneous cavity of 2 × 2 cm in size was created. Polypropylene mesh pieces of 2 × 1 cm and MRSA solution of 0.1ml of 10⁸ CFU/mL were used. G-CSF was applied systemically or locally in a dosage of 0.02 MU/30 g body weight. There were 8 groups: group I, wound + MRSA; group II, wound + mesh + MRSA; group III, wound + mesh + MRSA + G-CSF (ip, 48 h before operation); group IV, wound + mesh + MRSA + G-CSF (ip, 24 h before operation); group V, wound + mesh + MRSA + G-CSF (locally, into the cavity); group VI, wound + mesh (incubated in G-CSF solution for 4 h) + MRSA; group VII, wound + mesh + MRSA + G-CSF, ip, 24 h from operation; and group VIII (positive control group), wound + mesh + MRSA + Teicoplanin (0.03 mg/30 g body weight, ip, 1/2 h before operation). Three days after, animals were killed and incisions were examined for possible infection or abscess formation and wound failure. Meshes were removed; after vortexing and dilution, samples were incubated with 5% agar media. Results of bacterial incubation were evaluated 24 h and 48 h later. There were symptoms of wound infection and abscess formation in all groups except group VIII. In group VIII, MRSA was isolated in 7 events with a colony count below 10³. Bacterial counts were above 10⁶ (10⁶–10⁸) in all other groups. Thus, it was observed that wound infection could be created with this model, but G-CSF could not prevent the development of wound infection, whether it was administered systemically or locally. Teicoplanin decreased the number of colony-forming units of MRSA, and prevents wound infection in this MRSA wound infection model.     

Gelatin-sealed dacron graft is not more susceptible to MRSA infection than PTFE graft.

OBJECTIVES: The purpose of this experimental study was to compare the susceptibility of gelatin-sealed Dacron and PTFE prostheses to infection by MRSA. DESIGN: Prospective, randomized, controlled animal study. MATERIALS AND METHODS: Graft infections were established in the subcutaneous tissues of 60 female Spraque-Dawley rats by the implantation of gelatin-sealed Dacron or PTFE prostheses followed by topical inoculation with methicillin-resistant Staphylococcus aureus. The study groups were as follows: (1A) uncontaminated gelatin-sealed Dacron group, (1B) untreated contaminated gelatin-sealed Dacron group, (1C) contaminated gelatin-sealed Dacron group with intraperitoneal teicoplanin treatment, (2A) uncontaminated PTFE group, (2B) untreated contaminated PTFE group, and (2C) contaminated PTFE group with intraperitoneal teicoplanin treatment. The grafts were removed after 7 days and evaluated for infection by counting the number of adherent bacteria on the graft material after rinsing and sonication. The perigraft tissue was harvested for histopathological study. To investigate the existence of any infection, blood samples were collected by cardiopuncture for a culture analysis. RESULTS: No significant difference in bacteria counts was observed between gelatin-sealed Dacron and PTFE grafts. In groups 1A and 2A, there was no infection detected. The bacterial counts for MRSA were 7.4 x 10(5) in group 1B and 8.6 x 10(5) in group 2B. There was also no infection in groups 1C and 2C. While the difference between group 1B and 2B was not significant (p>.05), bacterial counts in group 1B or 2B were significantly higher than those in other groups. Blood cultures were only positive in four rats in group 1B and in two rats in group 2B. The severities of the inflammation of the perigraft tissues was low in groups 1A and 2A, high in groups 1C and 2C, and between the range from low to moderate in groups 1B and 2B. CONCLUSION: The susceptibility of gelatin-sealed Dacron to bacterial infection was not higher than that of PTFE.     

整形外科患者创面感染MRSA的感染率及对应治疗观察

目的:探讨整形外科创面感染的特点及复方新诺明对创面耐甲氧西林金黄色葡萄球菌感染的治疗作用。方法:2013年1月~12月,共收治70例慢性创面患者,其中12例MRSA感染,创面大小1.5cm×1.5cm~20cm×15cm,通过每日复方新诺明悬浮液进行治疗,观察临床疗效、细菌清除情况及不良反应。结果:治疗创面1周后MRSA转阴率83.3%,治疗2周后MRSA转阴率91.67%,未出现明显的不良反应。结论:整形外科慢性局部创面MRSA感染不能忽视,复方新诺明可作为治疗局部创面MRSA感染的首选局部用药。     

The protective effect of heparin in experimental bladder infection.

The surface mucopolysaccharide layer of the urinary bladder has been shown to interfere with bacterial attachment, and we therefore consider it to be the primary mechanism of combatting bacterial colonization and subsequent infection. Experimentally, hydrochloric acid alters this layer in such a way as to permit massive bacterial adsorption to the vesical mucosa. Heparin, an acid mucopolysaccharide, was instilled into rabbit bladders that had their naturally occurring mucopolysaccharide altered by hydrochloric acid. Heparin was shown to inhibit the attachment of inoculated Escherichia coli to these acid-treated bladder mucosas, and the degree of protection afforded was similar to that of the mucopolysaccharide layer of the intact urothelium.     

The prevention and treatment of vascular graft infection with a Triclosan (Irgasan)-bonded Dacron graft: an experimental study in the pig.

Objectives: to evaluate the role of Triclosan (Irgasan(R)) in the prevention of prosthetic graft infection. Material and methods: fifty-one pigs were assigned randomly to six groups. Group I (graft) and II (graft and Triclosan) were control groups. Groups III (graft) and IV (grafts and Triclosan) were contaminated with 2 x 10(7)CFU/ml S. aureus. Groups V (graft) and VI (graft and Triclosan) were intraoperatively contaminated with 2 x 10(7)CFU/ml S. aureus and reoperated on after 7 days. Remaining animals were sacrificed on day 28. The end point of the investigation was vascular graft infection, defined as the bacteriological and/or histological proof of infection. Results in both control groups no vascular graft infections were detected in Groups I and II. All of the group III animals presented but none of the group IV developed a graft infection (p <0.02). All of the group V animals presented and 10 of 12 animals developed a graft infection. Conclusion: in this animal model Triclosan bonding appears effective in preventing prosthetic graft infection. However, the in situ replacement of Triclosan-protected grafts was not successful in the treatment of graft infection.     

The immunosuppressive effect of fresh allogeneic bone graft in mice

Summery. We investigated the immunosuppressive effect of fresh bone allografts after donor specific spleen cell transfusion in mice. Allografts from major histocompatibility complex incompatible mice were performed one week after the transfusion. Cellular and humoral immune responses were recorded by measuring alloreactive cytotoxic T-lymphocyte activity and antibody activity. Survival in days of a second set skin graft was measured for determining clinical immunity. Alloreactive cytotoxic T-lymphocyte activity was stimulated at 17 days (10 days after bone grafting) and then suppressed at 31 days (24 days after bone grafting). The survival of the second set skin graft was not diminished at this time. This outcome indicates that the spleen cell stimulated cellular immune response was suppressed after fresh bone allografts, suggesting that these allografts have an immunosuppressive effect and induce immunosuppressive actions.

---

Résumé. Nous avons fait des recherches sur l’effet immunosuppresseur des greffes d’os allogéniques fra?ches après la transfusion de cellules spléniques spécifiques de donneurs chez les souris. Des greffes d’os allogéniques provenant de souris à complexes tissulaires incompatibles ont été effectuées 1 semaine après la transfusion de cellules spléniques spécifiques de donneurs. Les réponses immunes aussi bien cellulaires que humorales ont été enregistrées en mesurant l’activité de lymphocyte T cytotoxique alloréactive et l’activité d’anticorps. La survivance (en jours) d’une greffe de peau de deuxième application a été mesurée pour déterminer l’immunité clinique. L’activité de lymphocyte T cytotoxique alloréactive a été stimulée une fois à 17 jours (10 jours après la greffe d’os), puis supprimée à 31 jours (24 jours après la greffe d’os). La survivance de la greffe de peau de deuxième application n’avait pas diminuée à 31 jours (24 jours après la greffe d’os). Ce résultat indique que la réponse immune cellulaire stimulée des cellules de rate a été supprimée après la greffes d’os allogénique fra?che. Ceci suggère que les greffes d’os allogéniques présentent un effet immunosuppresseur et induisent des actions d’immunosuppresseur retardées.

---

---

Accepted: 12 July 1996     

The prophylactic efficacy of rifampicin-soaked graft in combination with systemic vancomycin in the prevention of prosthetic vascular graft infection: an experimental study

OBJECTIVE: To investigate the prophylactic efficacy of systemic, topical, or combined antibiotic usage in the prevention of late prosthetic vascular graft infection caused by methicillin-resistant Staphylococcus epidermidis (MRSE) and the differential adherence of S. epidermidis to Dacron and ePTFE grafts in a rat model. MATERIALS AND METHODS: Graft infections were established in the back subcutaneous tissue of 120 adult male Wistar rats by implantation of 1-cm(2) Dacron/ePTFE prosthesis followed by topical inoculation with 2 x 10(7) CFU of clinical isolate of MRSE. Each of the series included one group with no graft contamination and no antibiotic prophylaxis (uncontaminated control), one contaminated group that did not receive any antibiotic prophylaxis (untreated control), one contaminated group in which perioperative intraperitoneal prophylaxis with vancomycin (10 mg/kg) was administered, two contaminated groups that received rifampicin-soaked (5 mg/1 ml) or vancomycin-soaked (1 mg/1 ml) grafts, and one contaminated group that received a combination of rifampicin-soaked (5 mg/1 ml) graft with perioperative intraperitoneal vancomycin prophylaxis (10 mg/kg). The grafts were removed sterilely 7 days after implantation and evaluated by using sonication and quantitative blood agar culture. RESULTS: MRSE had significantly greater adherence to Dacron than ePTFE grafts in the untreated contaminated groups (P < 0.001). Rifampicin had better efficacy than vancomycin in topical application, but the difference was not statistically significant (P > 0.05). Intraperitoneal vancomycin showed a significantly higher efficacy than topical vancomycin or rifampicin (P < 0.001). The best results were provided by a combination of intraperitoneal vancomycin in rifampicin-soaked graft groups (P < 0.001). CONCLUSIONS: The combination of rifampicin and intraperitoneal vancomycin seems to be the best choice for the prophylaxis of late prosthetic vascular graft infections caused by MRSE.     

The effect of local infection upon wound healing: an experimental study

Local infection was introduced into rat abdominal wounds using a 10(8) bacterial/ml inoculum. Three groups of infection were used: Staphylococcus aureus, Pseudomonas aeruginosa and a combination group of Escherichia coli and Proteus mirabilis. Infection was shown to delay healing as judged by bursting tests. Fibroblast proliferation was depressed at the wound edges but there was an increase in the total amount of hydroxyproline present. Small vessel angiogenesis was increased in areas of abscess formation but larger vessels were commonly blocked by thrombus or distorted by surrounding inflamed tissue. The possible causes of these effects are discussed.     

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.     

Transmission of cytomegalovirus infection in mice by skin graft

Transmission of infectious disease, including virus, by allogeneic tissue transplants is a major clinical concern. The present study provided evidence for the transfer of murine cytomegalovirus (MCMV) by syngeneic and allogeneic skin grafts transplanted immediately after harvest from acutely infected donor mice. Transfer of MCMV also occurred following skin grafting with cryopreserved syngeneic skin. Recipients of infected skin were first positive for MCMV between 9 and 15 days post transplant, and MCMV was continually detectable through day 30. These results suggest that fresh or banked skin may serve as a source for transmission of cytomegalovirus infections.     

The biological and biomechanical effect of different graft tensioning in anterior cruciate ligament reconstruction: an experimental study

The objective of the present animal experimental study was to determine the effect of initial graft tension (1 N, 7.5 N, 17.5 N) on the biomechanical and histological behavior of the anterior cruciate ligament (ACL) graft using a rabbit model. After 2, 8, and 32 weeks, the femur-ACL-tibia complex was removed, and biomechanical and histomorphometrical studies were performed. The morphometric parameters cellularity, cell nucleus volume, and vascularity increased up to the 8th postoperative week and showed significant differences between the study groups. The values obtained demonstrated that higher pretension had increased the pull-out force and stiffness. However, at 32 weeks postoperatively, the pull-out force was significantly below the values of the normal ACL (40.5% at 1 N, 45.1% at 7.5 N, and 50.8% at 17.5 N). In the present study, it was demonstrated that an intraoperatively selected initial tension of 17.5 N induces histomorphometric changes in the graft, which result in a higher biomechanical loading capacity. The results showed that higher initial graft tension resulted in improved histological and biomechanical parameters. Pathological changes in the graft such as an increased central necrosis rate or cartilage damage due to 'overconstraining' of the knee were not observed at the selected initial tensions.     

The retroperitoneum protects prosthetic graft material from intraperitoneal contamination: an experimental study.

OBJECTIVES: To evaluate the ability of the retroperitoneum to serve as a barrier, against bacterial contamination, between the peritoneal cavity to the retroperitoneal space. METHODS: Seventy rats had a small piece of knitted Dacron graft placed in the retroperitoneal space and 10(6)-10(9) colony forming unit (cfu) Enterococcus faecalis was injected into the peritoneal cavity. In half the retroperitoneal (RP) group, the retroperitoneum was preserved and in the remainder, the open peritoneal (OP) group, needle holes were created. Grafts were harvested after 1, 4, or 7 days and cultured for E. faecalis. A blood sample was collected from three rats in each group for culture before the graft was harvested. RESULTS: Graft infection did not develop in any rat injected with 10(6) or 10(7) cfu in the RP group, while seven out of the 10 graft cultures of the OP group grew E. faecalis (P = 0.003). In rats injected with 10(8) or 10(9) cfu, five out of the 10 graft cultures in the RP group and eight out of 10 in the OP group grew E. faecalis. All blood cultures were negative when the injected bacterial count was 10(7) cfu or less. One out of the three blood cultures was positive at 10(8) cfu, and all were positive at 10(9) cfu. CONCLUSIONS: These results suggest that an intact retroperitroneum acts as a protective barrier against intraperitoneal bacterial contamination, particularly when blood cultures are negative.     

The effect of nitecapone on early graft function in experimental single lung transplantation

Nitecapone is an antioxidant molecule which has been shown to protect the heart against ischemia-reperfusion injury. We investigated whether a similar effect could be detected on lung graft preservation in a porcine model of single lung transplantation. Donors received either nitecapone or placebo in a modified Euro-Collins pulmonary flush solution. After cold storage for 19 h the left lung was transplanted. Patients in the nitecapone group received a nitecapone infusion during the graft reperfusion. A right-side heart bypass was used to measure flow distribution and pulmonary vascular resistance (PVR) in the recipient's transplanted and native lungs, respectively. Pulmonary vein blood samples were analyzed for blood gases, free radical trapping capacity and diene conjugates. PVR was high in the transplanted lung, which received only 20% of the blood flow. Oxygen tension in the transplanted lung was low (2.3-26.7 kPa). Nitecapone treatment increased the plasma free radical trapping capacity threefold. In spite of this increase in antioxidative capacity nitecapone could not protect the lung against ischemia-reperfusion injury when pulmonary hemodynamics, gas exchange or plasma diene conjugates were used as measures of lung graft function.     

Confirmation of infection of an aortic graft

The presentation of an aortic graft infection may be dramatic in the form of an aortoenteric fistula or drainage of pus from the wound. Some cases may be more subtle with presentations of fever of unknown origin. Prior to embarking upon major operative repair for these suspected lesions, it is essential to confirm the presence of infection. Under CT control, a fine needle may be inserted into the peri-graft space, and cultures may be obtained. Further confirmation may be achieved by an injection of a small amount of contrast material which will demonstrate lack of incorporation of the graft into surrounding tissues. Prior confirmation of graft infection permits a staged procedure to repair this technique is illustrated with a case history.     

The effect of splenectomy on pulmonary infection in newborn mice

Overwhelming postsplenectomy infection is a widely discussed and studied problem. The route of infection, the specific organisms involved, and the age at splenectomy and bacterial challenge are crucial factors in determining the genuine threat of the disease. We studied Staphylococcus aureus respiratory infection in 10-day-old mice who had undergone splenectomy or sham operation 7 days earlier. We did not find an increase in fatal staphylococcal pneumonitis under these conditions. Further laboratory definition of this complex issue is warranted.     

MRSA infection in lower extremity wounds

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most frequently isolated bacteria in wound cultures. MRSA has been linked to lengthened wound healing times, an increase in adverse postoperative outcomes, and mortality. This study investigated the incidence of MRSA in lower extremity wounds and examined outcomes associated with MRSA-infected wounds versus non-MRSA-infected wounds. A retrospective study was conducted. Patients with MRSA-infected wounds were compared with those with uninfected wounds in a 1:2 ratio. Demographics, infection, and stay information were collected. Data were analyzed using SPSS 15.0. 51 patients were included (17 with MRSA and 34 without MRSA). Patients with MRSA had increased lengths of stay and a higher incidence of adverse postoperative outcomes compared with non-MRSA patients. An MRSA infection adversely affects a patient's hospital course. Preoperative screening for MRSA and postoperative surveillance should be considered to prevent and eliminate the spread of this virulent bacterium.     

Prosthetic vascular graft infection.

The aetiology, diagnosis and management of prosthetic vascular graft infection are reviewed. The importance of contamination at the time of surgery as the crucial aetiological factor is highlighted. Staphylococcus epidermidis is the causative organism in over 50 per cent of cases and the reasons for this are explored. Sound surgical technique, use of prophylactic antibiotics and the avoidance of a groin incision are emphasized as the most important factors in prevention of graft infection. Difficulties of diagnosis are highlighted and the diagnostic role of various imaging methods is assessed. Graft excision with extra-anatomic revascularization is presented as the conventional surgical solution, while the roles of less radical surgical solutions and non-operative management are discussed.