Nielsen J, Ladefoged S D, Kolmos H J
Department of Clinical Microbiology, Hvidovre Hospital, Copenhagen, Denmark.
Nephrol Dial Transplant. 1998 Nov;13(11):2847-52. doi: 10.1093/ndt/13.11.2847.
Dialysis catheters are a common cause of nosocomial septicaemia in haemodialysis units usually due to staphylococci, of which Staphylococcus aureus is the most pathogenic. In this study, the epidemiology and pathogenesis of dialysis catheter-related infections were studied, and methods to identify patients with these infections were evaluated.
A one-year prospective study of 67 catheters in 43 haemodialysis patients was performed. Details about patients and catheters were obtained successively during the catheter period, and biochemical parameters expected to be related to infection were measured. After catheter insertion, all patients were screened for nasal carriage of S. aureus, and a culture was taken from the skin overlying the catheter insertion site. Once a week, cultures were taken from the insertion site and from the hub, and aerobic and anaerobic blood cultures were drawn from the catheter. If clinical signs of septicaemia occurred, peripheral blood cultures were also performed, when it was possible.
The incidence of septicaemia was 49% (21/43) in patients, and 56% of all cases were caused by S. aureus. The mortality was 14% (3/21) and the incidence of severe secondary complications to septicaemia was 24% (5/31). In all, 80% of all severe complications and 75% of all deaths from septicaemia were due to S. aureus. With respect to S. aureus septicaemia, the predictive values of positive (P) and negative (N) S. aureus cultures were as follows: nasal culture, P=36% (10/28), N=90% (35/39); culture from the insertion site, P=72% (13/18), N=98% (48/49); and culture from the hub, P=75% (3/4), N=83% (52/63). The risk ratio for S. aureus septicaemia was 26.2 (6.1-113), P=0.0001, according to the presence of S. aureus at the insertion site, and 3.3 (0.74-15.1), P=0.12 according to nasal carriage of S. aureus. The frequency of S. aureus phage-type Group 2 (43%) was much higher than the general frequency of this phage-type in Denmark, which is about 23%. Catheter blood cultures were positive although there were no clinical signs of septicaemia in 34% (23/67) of all catheter periods--84% of these were due to coagulase-negative staphylococci.
Dialysis catheter-related S. aureus septicaemia was highly unlikely if the patient had not been carrying S. aureus in the nose or at the insertion site during the time the catheter was in place. The best predictor of dialysis catheter-related S. aureus septicaemia was a positive S. aureus culture from the insertion site. Positive catheter blood cultures unrelated to any clinical signs of septicaemia occurred in one-third of all catheter periods, and 84% of these were due to coagulase-negative staphylococci.
透析导管是血液透析单位医院败血症的常见原因，通常由葡萄球菌引起，其中金黄色葡萄球菌致病性最强。本研究对透析导管相关感染的流行病学和发病机制进行了研究，并评估了识别这些感染患者的方法。
对43例血液透析患者的67根导管进行了为期一年的前瞻性研究。在导管留置期间陆续获取患者和导管的详细信息，并测量预期与感染相关的生化参数。导管插入后，对所有患者进行金黄色葡萄球菌鼻腔带菌筛查，并从导管插入部位上方的皮肤取样培养。每周一次，从插入部位和接头处取样培养，并从导管抽取需氧和厌氧血培养。如果出现败血症的临床症状，尽可能进行外周血培养。
患者败血症发生率为49%（21/43），所有病例的56%由金黄色葡萄球菌引起。死亡率为14%（3/21），败血症严重继发并发症发生率为24%（5/31）。所有严重并发症的80%和败血症死亡的75%均由金黄色葡萄球菌引起。对于金黄色葡萄球菌败血症，金黄色葡萄球菌培养阳性（P）和阴性（N）的预测值如下：鼻腔培养，P = 36%（10/28），N = 90%（35/39）；插入部位培养，P = 72%（13/18），N = 98%（48/49）；接头处培养，P = 75%（3/4），N = 83%（52/63）。根据插入部位是否存在金黄色葡萄球菌，金黄色葡萄球菌败血症的风险比为26.2（6.1 - 113），P = 0.0001；根据金黄色葡萄球菌鼻腔带菌情况，风险比为3.3（0.74 - 15.1），P = 0.12。金黄色葡萄球菌噬菌体2型的频率（43%）远高于丹麦该噬菌体类型的一般频率（约23%）。在所有导管留置期间的34%（23/67）中，导管血培养呈阳性，尽管没有败血症的临床症状——其中84%是由凝固酶阴性葡萄球菌引起的。
如果患者在导管留置期间鼻腔或插入部位未携带金黄色葡萄球菌，则极不可能发生透析导管相关的金黄色葡萄球菌败血症。透析导管相关金黄色葡萄球菌败血症的最佳预测指标是插入部位金黄色葡萄球菌培养阳性。在所有导管留置期间的三分之一中，导管血培养阳性但与任何败血症临床症状无关，其中84%是由凝固酶阴性葡萄球菌引起的。
