Bacterial resistance of refrigerated and cryopreserved aortic allografts in an experimental virulent infection model

PURPOSE: The bacterial resistance of refrigerated and cryopreserved aortic allografts in a highly virulent infection in a dog model was studied. METHODS: The infrarenal aorta of 12 dogs was replaced with either a cryopreserved aortic allograft (group I, n = 6) or a refrigerated aortic allograft (group II, n = 6) in infected sites. Allografts were harvested from dogs and stored for 1 week, either by cryopreservation (-140 degrees C) or refrigerated method (4 degrees C), in a preservation medium. At the time of implantation, induction of infection was achieved with an infected piece of knitted Dacron placed just beneath the allograft. The Dacron was contaminated in vitro by soaking it in a solution with Staphylococcus aureus PR209. All 12 dogs received no adjunct antibiotic or antithrombotic therapy. Four weeks after implantation, the animals were killed to recover the grafts for bacteriological and histological analyses. Bacterial results were expressed as colony-forming units (CFU)/cm2 of graft material. RESULTS: In group I, only one allograft grew bacteria at 2. 16 x 10(6 )CFU/cm2, with a blood culture positive for S aureus. In group II, one dog died at 3 weeks from a false septic aneurysm rupture, all the allografts were infected (P <.05) with a mean bacterial count of 9.41 +/- 6.8 x 10(4) CFU/cm2, and three blood cultures were positive for S aureus. The patency of the grafts was analyzed at the time of recovery. Three laminar thrombi without occlusion were present in group I; none were present in group II. A better preserved endothelium in group I was revealed by means of histologic analysis staining with factor VIII antibody before implantation. After 4 weeks of implantation in the infected site, infected allografts presented polynuclear infiltrates in the media with a high degree of inflammatory reaction, and endothelial recovery was more significant in group I, with numerous young plump cells. CONCLUSION: This study demonstrates that cryopreserved allografts implanted in infected sites in a dog model can produce greater bacterial resistance.     

Anastomotic tensile strength following in situ replacement of an infected abdominal aortic graft

The tensile strength and histologic features of anastomotic bonding were studied prior to and following in situ replacement of aortic vascular prostheses infected by Staphylococcus epidermidis. Sterile (n = 6) and infected (n = 19) Dacron grafts were used to replace the abdominal aorta of 25 dogs. After five weeks, grafts were explanted, and peak tensile force (measured in kilograms) required for anastomotic disruption was measured using a linear gain tensiometer. Anastomotic tensile strength (mean +/- SEM) of infected grafts (5.4 +/- 0.5 kg) was decreased when compared with that of sterile, control grafts (9.0 +/- 0.9 kg). The decreased anastomotic tensile strength of infected grafts was the result of an inflammatory aortitis adjacent to the suture line. Only grafts infected with the study strain of bacteria demonstrated signs of infection. In 19 dogs, the graft infection was treated by graft excision, antibiotic administration, and in situ graft replacement (Dacron or polytetrafluoroethylene prostheses). After five weeks and 12 weeks, anastomotic tensile strength of polytetrafluoroethylene (10.6 +/- 0.6 kg) and Dacron (10.8 +/- 0.5 kg) replacement grafts was similar to that of uninfected control grafts. In situ replacement of vascular prostheses infected by S epidermidis can result in graft healing with normal anastomotic bonding.     

Importance of Staphylococcus epidermidis in the bacterial colonization of abdominal drains in surgical patients

Bacterial adherence to biomaterials as an element of clinical relevance is a well-known factor in the pathogenesis of sepsis. Drainages, intravascular catheters, surgical prostheses and other devices are susceptible to bacterial colonization with clinical consequences. In the last few years attention has been paid to coagulase-negative Staphylococcus (S. epidermidis), mainly to some strains able to produce a highly adhesive polysaccharide substance, called glycocalix or slime. This promotes adherence either interbacterial either between bacteria and biologic tissues or synthetic materials acting as a pathogenetic factor in sepsis being able to increase bacterial resistance to phagocytes and antibiotics. Bacterial contamination of 40 abdominal drainage tubes in patients operated in elective and in emergency surgery for various pathology has been evaluated. Sonication of the tip of the drainage was utilized in order to promote the detachment of adherent colonies and its effectiveness was compared to that of microcentrifugation. Culture of 25 drainages (62.5%) showed no bacterial contamination; 7 drainages (17.5%) have proved to be colonized by S. epidermidis, in 4 cases the isolated strains were also methicillin-resistant, 2 of which slime-producing. Out of the 7 drainages colonized by S. epidermidis, 4 were removed from patients operated in emergency: none of the isolated strains was slime-producing. Six drainages (15%) were colonized by Gram+ bacteria (S. fecalis, P-sensible cocci, rods), 1 (2.5%) by E. coli and 1 (2.5%) by P. aeruginosa, S. epidermidis appears to be the chief contaminant of abdominal drainages, especially in emergency surgery; slime production has always been observed in methicillin-resistant strains: this confirms the hypothesis that slime production is typical of specialized, virulent strains.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prophylactic antibiotics prevent bacterial biofilm graft infection.

Bacterial biofilm graft infection is due to prostheses colonization by Staphylococcus epidermidis, a pathogen frequently recovered from perigraft tissues of man during vascular procedures despite the use of asepsis and prophylactic antibiotics. The effect of preoperative intraperitoneal cefazolin, administered at a standard (15 or 30 mg/kg) and high (120 mg/kg) dose, on the prevention of bacterial biofilm infection was studied in a rat model. Seventy-four Dacron grafts, colonized in vitro with S. epidermidis to produce an adherent biofilm (3.19 +/- 0.71 x 10(7) colony-forming units/cm2 graft), were implanted in the dorsal subcutaneous tissue at 0.5, 2, and 4 hr after antibiotic administration. The study strain was a slime-producing clinical isolate with minimum inhibitory concentration (MIC) of 15-30 micrograms/ml to cefazolin. Subcutaneous tissue antibiotic levels were determined at each time interval. One week after implantation, the concentration of bacteria in the surface biofilm by quantitative agar culture was significantly decreased (P less than 0.05) only for grafts implanted when antibiotic tissue levels were greater than or equal to the MIC of the study strain. The result of no growth by biofilm broth culture was significantly achieved (P less than 0.01) only for grafts implanted 0.5 hr after high dose cefazolin, in which the tissue antibiotic level was above the MIC of the study strain. Antibiotics can markedly reduce the bacteria concentration of a prosthetic surface biofilm. The effectiveness of prophylactic antibiotics on the prevention of graft infection is dependent upon maintaining an adequate antibiotic level in the perigraft tissues for the duration of the procedure.     

Identification of Staphylococcus epidermidis vascular graft infections: a comparison of culture techniques

Culture of prosthetic material is routinely used to exclude or implicate infection in the pathogenesis of late-appearing graft complications. In a canine model of aortic graft infection caused by a bacterial biofilm, the influence of culture media (blood agar and tryptic soy broth) and mechanical surface biofilm disruption (tissue grinding and ultrasonic oscillation) on microorganism recovery was determined. Dacron prostheses colonized in vitro with Staphylococcus epidermidis were implanted in the infrarenal aortas of 36 dogs. After 3 weeks an infection with anatomic characteristics of late graft infection in humans was present. Explantation (+/- surface biofilm disruption) of infected grafts showed broth culture was superior (p less than 0.001) to agar media in confirming infection. The recovery rate of S. epidermidis was 30% with agar media, was 72% with broth media alone, and was 83% with broth media plus biofilm disruption. In situ replacement of infected grafts plus parenteral antibiotics resulted in early (1 month) healing of 31 grafts without signs of infection. All replacement grafts were sterile when cultured in broth media alone, but the addition of biofilm disruption isolated the study strain from eight (22%) of 36 grafts (p less than 0.01). Biofilm disruption by tissue grinding or sonication increased bacteria recovery equally. When biofilm bacterial concentration was less than 100 colony-forming units/cm2 of graft, only culture in broth media reliably recovered microorganisms. In the absence of perigraft inflammation, microbiologic recovery techniques that identify bacterial biofilms are necessary to exclude infection in studies concerning the pathogenesis of late graft complications or the treatment of S. epidermidis prosthetic infections.     

Antimicrobial susceptibility of coagulase-negative staphylococci on tissue allografts and isolates from orthopedic patients.

Allograft infection occurs at a rate not different from that of similar procedures with large allografts or sterilized prosthetic devices and is usually caused by coagulase-negative staphylococci (CNS). CNS are feared for their limited antimicrobial susceptibility. We aimed at investigating this risk. CNS were isolated from 260 of 1461 allograft tissue grafts and compared with 384 consecutive clinical isolates from a general orthopedic population (258 patients). The CNS were identified and examined for their susceptibility to nine antibiotics used in routine practice. Staphylococcus epidermidis was the most commonly identified (35%) and the most resistant species of the allograft isolates. Comparing the overall antibiotic susceptibility patterns, clinical pathogens were significantly more resistant to six of the nine antibiotics (p < 0.01), namely penicillin, oxacillin, erythromycin, clindamycin, ofloxacin, and gentamicin. In conclusion, massive allograft infection is a well-known life-threatening surgical risk. However, we did demonstrate that allograft-related in contrast to orthopedic clinics-related CNS, are susceptible to commonly used first and second line antibiotics.     

Treatment of vascular graft infection by in situ replacement with cryopreserved aortic allografts: An experimental study

Purpose: The purposes of this study were to prove the efficacy of cryopreserved aortic allografts to treat an established vascular graft infection by in situ replacement in an animal model and to evaluate the role of the antibiotics normally used to decontaminate the allografts. Methods: Twenty-three dogs underwent infrarenal aortic replacement with a gelatin-sealed knitted polyester graft contaminated in vitro by staphylococcus epidermidis RP-62. One week later, the 18 surviving animals underwent reoperation for graft removal and were randomized into three groups for in situ replacement: group I (control, n = 6) received a new gelatin-sealed graft; group II (n = 6) received a non–antibiotic-treated cryopreserved allograft; and group III (n = 6) received an antibiotic-treated cryopreserved allograft. Control grafts and allografts were removed 4 weeks after the initial intervention for quantitative bacteriologic analysis and histologic analysis. Bacteriologic results were expressed as colony-forming units per square centimeter of graft material. Qualitative bacteriologic analysis was also obtained from perigraft fluid and tissue. Results: All of the initially implanted grafts and all of the control grafts (group I) were infected at the time of removal. In group II, three out of six allografts were not totally incorporated, whereas in group III incorporation was always complete, with a significantly decreased inflammatory reaction. All of the antibiotic-treated allografts were sterile, whereas three untreated allografts grew bacteria. Conclusions: In this model, cryopreserved aortic allografts were more resistant to reinfection than synthetic grafts after in situ replacement of an infected prosthetic graft. However, the antibiotic loading of the cryopreserved aortic allograft appears to be essential to obtain optimal therapeutic effects. (J Vasc Surg 1998;27:689-98.)     

The clinical use of an antibiotic-bonded graft.

Attempts to produce an antibiotic-bonded prosthesis have failed owing to poor binding, drug toxicity or inadequate antimicrobial activity of the antibiotic particularly against Staphylococcus epidermidis. Rifampicin, with an ideal spectrum, but untested against slime-forming S. epidermidis has recently been shown to bind with carboxyl groups on gelatin-sealed Dacron. We therefore investigated rifampicin activity against 30 slime-forming adherent S. epidermidis colonies, isolated from 40 consecutive aortic graft recipients, and compared it with their methicillin, gentamicin, cefuroxime, tetracycline and vancomycin resistance patterns. The S. epidermidis colonies were highly sensitive to very low levels of rifampicin. Rifampicin was then bonded to gelatin-sealed Dacron aortic prostheses which were inserted in four patients at high risk of developing subsequent infection.     

Adherence of mucin and non-mucin-producing staphylococci to preclotted and albumin-coated velour knitted vascular grafts

The mechanisms involved in bacterial adherence to vascular grafts are important in understanding prosthetic infections. Albumin-coated Dacron (ACD) is a new development in vascular graft fabrication. However, albumin acts as a receptor for certain gram-positive bacterial adhesions. Five pathogenic, coagulase-negative Staphylococcus epidermidis strains were used to measure the differential microbial adherence to ACD versus untreated velour-knitted Dacron (VKD) vascular prostheses. Specimens of VKD, preclotted VKD, and ACD were inoculated with each of the five strains (10(7) colony-forming units/ml) for 2, 4, 8, 12, and 24 hours. After incubation, graft specimens were washed to remove nonadherent organisms and oscillated ultrasonically to remove adherent organisms. The sonication effluent was plated to trypticase soy agar to quantitate the adherent organisms. Adherence was significantly greater (p less than 0.01) to VKD compared with preclotted VKD and ACD at 2, 4, 8, and 24 hours. Four of the five study strains demonstrated significantly greater adherence to VKD than to either ACD or preclotted VKD. Adherence of S. epidermidis increased with exposure time. Albumin bonded to velour-knitted Dacron does not increase coagulase-negative staphylococcal adherence compared with the noncoated vascular prostheses. Binding albumin to vascular prostheses does not increase the risk of staphylococcal colonization.     

Infection of vascular prostheses caused by bacterial biofilms

A canine model was developed to study the efficacy of graft replacement as treatment for vascular prosthesis infections from Staphylococcus epidermidis. Infrarenal aortic graft infections were established in 18 dogs by implantation of Dacron prostheses colonized in vitro with a slime-producing strain of S. epidermidis to form an adherent bacteria-laden biofilm (5 X 10(6) colony-forming units/cm2 graft). Study animals developed a graft infection with anatomic and microbiologic characteristics typical of late prosthetic graft infections in humans (sterile perigraft exudate, absent graft incorporation, and normal serum leukocyte count and sedimentation rate). The S. epidermidis study strain was isolated from 14 of 18 explanted grafts (78%) by mechanical disruption of the graft surface biofilm and culture in broth media. Four dogs with sterile graft cultures had histologic evidence of bacterial infection. The established prosthetic surface biofilm infection was treated by graft excision, parenteral cefazolin, and graft replacement with a Dacron or polytetrafluoroethylene (PTFE) vascular prosthesis. One month after graft replacement, no PTFE graft had signs of infection, but perigraft exudate and inflammation involved three of nine Dacron grafts (33%). The study strain was recovered from four of nine PTFE grafts (44%) and two of nine Dacron (22%) replacement grafts (p greater than 0.05). Prosthetic replacement of Dacron prostheses infected by S. epidermidis as a bacteria-laden surface biofilm can result in early graft healing, but persistent colonization of one third of replacement grafts signify that recurrent clinical infection remains a risk.     

Studies in thoracic aortic graft infections: the development of a porcine model and a comparison of collagen-impregnated dacron grafts and cryopreserved allografts.

OBJECTIVE: A porcine model of thoracic aortic graft infection was created, and various anatomic sites and the timing of inoculation of the graft to induce infection were investigated. Ultimately, the ability of cryopreserved allograft to resist infection was compared with that of collagen-impregnated Dacron graft. METHODS: Yorkshire pigs (n = 16) underwent placement of an expanded polytetrafluoroethylene patch graft in the ascending aorta and the left atrial appendage (phase I). Eight animals were immediately given a 50-mL bolus (1 x 10(8) cfu/mL) of Staphylococcus aureus whereas the other 8 received the infusion 24 hours later. Animals were put to death 8 weeks later and the grafts were sterilely explanted and analyzed via microbiologic culture and standard histologic procedures for evidence of infection. The results displayed that the aortic graft and a delay of induced bacteremia of 24 hours were more reliable methods of producing infection. During phase II, 13 pigs were randomized to receive either a collagen-impregnated Dacron graft (n = 6) or a cryopreserved allograft (n = 7) in the ascending aortic position only and infusion of S aureus 24 hours after the operation. The experiment then proceeded to completion. RESULTS: Phase I results displayed that use of an aortic graft and induced bacteremia 24 hours after the operation was a more reliable and reproducible method of producing infection. In phase II, graft infection was present in 38.5% (5/13) of animals, with only 16.7% (1/6) in the collagen-impregnated Dacron graft group and 57.2% (4/7) in the cryopreserved allograft group becoming infected. There was no significant difference between the collagen-impregnated Dacron graft and cryopreserved allograft groups in the incidences of thoracic aortic graft infections (P =.27, Fisher exact test). CONCLUSIONS: This novel porcine model of thoracic aortic graft infection is a reproducible method for the investigation of thoracic aortic graft infections. The phase I study investigated the timing of the induced bacteremia and the most susceptible position of a graft. Phase II demonstrated that collagen-impregnated Dacron grafts are equivalent, if not superior, to cryopreserved allografts in resisting central vascular graft infections in the ascending aorta.     

Laser-induced shock waves enhance sterilization of infected vascular prosthetic grafts

BACKGROUND AND OBJECTIVE: Bacteria that cause infection of vascular prosthetic grafts produce an exopolysaccharide matrix known as biofilm. Growth in biofilms protects the bacteria from leukocytes, antibodies and antimicrobial drugs. Laser-generated shock waves (SW) can disrupt biofilms and increase drug penetration. This study investigates the possibility of increasing antibiotic delivery and sterilization of vascular prosthetic graft. STUDY DESIGN/MATERIALS AND METHODS: Strains of Staphylococcus epidermidis and S. aureus were isolated from infected prosthetic grafts obtained directly from patients. Dacron grafts were inoculated with the isolated bacteria, which were allowed to form adherent bacterial colonies. The colonized grafts underwent the following treatments: (a) antibiotic (vancomycin) alone; (b) antibiotic and SW (c) saline only; and (d) saline and SW. Six hours after treatment, the grafts were sonicated, the effluent was cultured and the colony forming units (CFU) were counted. RESULTS: CFU recovered from control grafts colonized by S. epidermidis were comparable: saline, 3.05 x 10(8) and saline+SW 3.31 x 10(8). The number of S. epidermidis CFU diminished to 7.61 x 10(6) after antibiotic treatment but the combined antibiotic+SW treatment synergistically decreased CFU number to 1.27 x 10(4) (P<0.001). S. aureus showed a higher susceptibility to the antibiotic: 2.26 x 10(6) CFU; antibiotic +SW treatment also had an incremental effect: 8.27 x 10(4) CFU (P<0.001). CONCLUSIONS: This study demonstrates that laser-generated shock waves have no effects alone, but can enhance the effectiveness of antibiotics against bacteria associated with prosthetic vascular graft biofilms, suggesting that this treatment may be of value as adjunctive therapy for prosthetic graft infections.     

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.     

去甲万古霉素载药涤纶血管材料体外抗菌活性测定

目的：评价去甲万古霉素（NV）载药涤纶血管材料体外抗菌活性。方法：血管材料剪成直径6mm圆形。分别制成空白涤纶材料和载药（NV）涤纶材料，分别于0，7，14，28d取样观察体外缓释性能。选用耐甲氧西林表皮葡萄球菌（MRSE）和耐甲氧西林金黄色葡萄球菌（MRSA）作为试验菌，分别观察空白和载药涤纶血管材料0．7，14，28d和快慢相的抗菌效果。结果：两种细菌0，7，14，28d载药涤纶材料-细菌混合培养液的菌落数显著少于空白涤纶材料-细菌混合培养液（P均〈0．001）。结论：体外试验证实载NV涤纶材料MRSE和MRSA具有抗菌作用，且可持续维持28d。提示该载药材料具有持久抗菌活性，可用于制备抗感染血管移植物。     

南宁地区某烧伤病房细菌生态学调查及耐药性分析

目的　调查分析南宁地区某烧伤病房近15年来细菌生态学及耐药性的变化。　方法1989年4月—2004年3月,从笔者单位2 269例患者的血培养及创面培养物中分离出5 855株细菌,用K B法进行药物敏感试验。以每5年为1个阶段,分析各阶段标本的细菌检查及耐药情况。　结果　笔者单位烧伤患者感染以革兰阴性杆菌为主(3 559株占60. 79% ),其中铜绿假单胞菌、阴沟杆菌、硝酸盐阴性杆菌各阶段检出率较高;其次为革兰阳性球菌(1 990株占33. 99% ),以金黄色葡萄球菌、表皮葡萄球菌、凝固酶阴性葡萄球菌为主。各主要感染菌种对多种常用抗菌药物如庆大霉素、第三代头孢菌素、诺氟沙星、异丁基哌嗪利福霉素等的耐药率维持在较高水平或呈逐阶段上升趋势,而对临床少用的亚胺培南及万古霉素耐药率则很低。　结论　气候环境及抗菌药物的应用对细菌生态学的分布和耐药性的变化有直接影响。临床治疗中应合理使用抗菌药物。     

肠外瘘并发腹腔感染的致病菌谱与耐药性分析

目的 研究肠外瘘并发腹腔感染的主要致病菌谱及致病菌对常用抗生素的耐药特点.方法 取226例肠外瘘并发腹腔感染患者的腹腔脓液进行细菌培养和抗生素药物敏感试验.结果 获取菌株520株,其中革兰阴性菌333株,革兰阳性菌180株,真菌7株.前10位的为大肠埃希菌131株,金黄色葡萄球菌62株,肠球菌59株,铜绿假单胞菌50株,肺炎克雷伯杆菌23株,鲍曼不动杆菌18株,阴沟肠杆菌17株,奇异变形杆菌15株,摩氏摩根菌15株,粪肠球菌12株.大肠埃希菌和肺炎克雷伯杆菌中表达超广谱13内酰胺酶阳性菌株分别为102株和17株.甲氧两林耐药金黄色葡萄球菌60株.结论 肠外瘘并发腹腔感染的致病菌谱以革兰阴性菌为主,超广谱β内酰胺酶阳性率较高;金黄色葡萄球菌则基本对甲氧西林耐药.     

Treatment of septic olecranon and prepatellar bursitis with percutaneous placement of a suction-irrigation system. A report of 12 cases

Ten cases of septic olecranon bursitis and two cases of septic prepatellar bursitis were treated in the period from 1975 to 1980 with antibiotics and percutaneous tube placement for suction-drainage and local antibiotic irrigation. All patients had positive bacterial cultures: Staphylococcus aureus in nine, beta-hemolytic Streptococcus in two, and Staphylococcus epidermidis in one. Intravenous antibiotics, local suction-drainage, and irrigation with a solution of 1% kanamycin and 0.1% polymyxin controlled the infection in each case. The antibiotic treatment averaged 19 days, compared with 24 days in a series in which suction-irrigation was not used. In contrast with studies in which aspiration or incision and drainage were performed, there were no complications or recurrences. Percutaneous suction-irrigation appears to be a safe, effective method of treatment that is particularly beneficial in severe cases of septic bursitis in which continuous drainage is desirable.     

脊柱外科手术术后伤口感染致病菌分布及药物敏感性

目的分析脊柱手术术后切口感染的致病菌分布特点及药物敏感性,为临床合理用药提供指导。方法收集2004年6月—2014年6月在第二军医大学长海医院骨科行脊柱手术后发生切口感染的165例患者的临床资料,回顾性分析其切口分泌物或脓液的细菌培养药物敏感实验结果。结果共培养分离出致病菌173株。其中革兰阴性菌(G-)114株(65.9%),前3位分别是铜绿假单胞菌32株(18.5%)、鲍曼不动杆菌28株(16.2%)、肺炎克雷伯杆菌21株(12.1%);革兰阳性菌(G+)54株(31.2%),前3位分别是金黄色葡萄球菌22株(12.7%)、凝固酶阴性葡萄球菌10株(5.8%)及表皮葡萄球菌8株(4.6%);真菌感染5株(2.9%)。革兰阴性菌对亚胺培南、美罗培南敏感性最高,对青霉素敏感性最低,对氨苄西林、哌拉西林敏感性也较低。革兰阳性菌对万古霉素敏感性最高,对青霉素敏感性最低。结论革兰阴性菌及革兰阳性菌在脊柱手术后切口感染中均较常见,且革兰阴性菌较革兰阳性菌所占比例更高,临床应根据细菌培养和药敏实验结果合理选用抗生素。     

Iontophoresed segmental allografts in revision arthroplasty for infection

Revision arthroplasty after infection can often be complicated by both extensive bone loss and a relatively high rate of re-infection. Using allograft to address the bone loss in such patients is controversial because of the perceived risk of bacterial infection from the use of avascular graft material. We describe 12 two-stage revisions for infection in which segmental allografts were loaded with antibiotics using iontophoresis, a technique using an electrical potential to drive ionised antibiotics into cortical bone. Iontophoresis produced high levels of antibiotic in the allograft, which eluted into the surrounding tissues. We postulate that this offers protection from infection in the high-risk peri-operative period. None of the 12 patients who had two-stage revision with iontophoresed allografts had further infection after a mean period of 47 months (14 to 78).     

烧伤病房728株感染病原菌的分布特点及耐药性分析

目的了解笔者单位近5年烧伤感染病原菌的分布特点及耐药情况。方法收集2001-2006年笔者单位306例烧伤患者创面分泌物等标本中分离的病原菌，对其菌种分布特点及耐药性进行分析。结果革兰阳性菌378株，其中金黄色葡萄球菌的菌株数居首位，尤以甲氧西林耐药金黄色葡萄球菌居多，表皮葡萄球菌和粪肠球菌的菌株数分别位居第2、3位。革兰阴性杆菌338株，其中鲍氏不动杆菌的菌株数居首位，阴沟肠杆菌和铜绿假单胞菌的菌株数分别位居第2、3位。检出真菌12株。结论笔者单位病原菌的分布情况，可能与甲氧西林耐药葡萄球菌呈多重耐药性以及鲍氏不动杆菌产生各种类型的β内酰胺酶有关。