Larsen Mette K S, Thomsen Trine R, Moser Claus, Høiby Niels, Nielsen Per H
Department of Biotechnology, Chemistry, and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark.
BMC Clin Pathol. 2008 Oct 28;8:10. doi: 10.1186/1472-6890-8-10.
Catheters are the most common cause of nosocomial infections and are associated with increased risk of mortality, length of hospital stay and cost. Prevention of infections and fast and correct diagnosis is highly important.
In this study traditional semiquantitative culture-dependent methods for diagnosis of bacteria involved in central venous catheter-related infections as described by Maki were compared with the following culture-independent molecular biological methods: Clone libraries, denaturant gradient gel electrophoresis, phylogeny and fluorescence in situ hybridization.
In accordance with previous studies, the cultivation of central venous catheters from 18 patients revealed that S. epidermidis and other coagulase-negative staphylococci were most abundant and that a few other microorganisms such as P. aeruginosa and K. pneumoniae occasionally were found on the catheters. The molecular analysis using clone libraries and sequencing, denaturant gradient gel electrophoresis and sequencing provided several important results. The species found by cultivation were confirmed by molecular methods. However, many other bacteria belonging to the phyla Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes were also found, stressing that only a minor portion of the species present were found by cultivation. Some of these bacteria are known to be pathogens, some have not before been described in relation to human health, and some were not closely related to known pathogens and may represent new pathogenic species. Furthermore, there was a clear difference between the bacterial species found in biofilm on the external (exluminal) and internal (luminal) side of the central venous catheter, which can not be detected by Maki's method. Polymicrobial biofilms were observed on most of the catheters and were much more common than the cultivation-dependent methods indicated.
The results show that diagnosis based on molecular methods improves the detection of microorganisms involved in central catheter-related infections. The importance of these microorganisms needs to be investigated further, also in relation to contamination risk from improper catheter handling, as only in vivo contaminants are of interest. This information can be used for development of fast and more reliable diagnostic tools, which can be used in combination with traditional methods.
导管是医院感染最常见的原因，与死亡率增加、住院时间延长及费用上升相关。预防感染以及快速准确的诊断至关重要。
在本研究中，将Maki所描述的用于诊断中心静脉导管相关感染中细菌的传统半定量培养依赖性方法与以下非培养分子生物学方法进行了比较：克隆文库、变性梯度凝胶电泳、系统发育分析和荧光原位杂交。
与先前研究一致，对18例患者的中心静脉导管进行培养发现，表皮葡萄球菌和其他凝固酶阴性葡萄球菌最为常见，导管上偶尔还会发现一些其他微生物，如铜绿假单胞菌和肺炎克雷伯菌。使用克隆文库和测序、变性梯度凝胶电泳和测序进行的分子分析得出了几个重要结果。培养所发现的菌种通过分子方法得到了证实。然而，还发现了许多其他属于变形菌门、厚壁菌门、放线菌门和拟杆菌门的细菌，这表明培养仅发现了现存菌种中的一小部分。其中一些细菌已知是病原体，一些以前未与人类健康相关联进行描述，还有一些与已知病原体关系不密切，可能代表新的致病菌种。此外，中心静脉导管外部（管腔外）和内部（管腔内）生物膜中发现的细菌种类存在明显差异，而Maki方法无法检测到这种差异。在大多数导管上观察到了多微生物生物膜，其比培养依赖性方法所显示的更为常见。
结果表明，基于分子方法的诊断提高了对中心导管相关感染中微生物的检测能力。这些微生物的重要性还需要进一步研究，也涉及到因导管处理不当导致的污染风险，因为只有体内污染物才是关注对象。这些信息可用于开发快速且更可靠的诊断工具，其可与传统方法联合使用。
