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CARDIOVASCULAR ANESTHESIA

Early Identification of Bacteria Leading to Central Venous Catheter Contamination

Christian Jeske, MD^*, Claus Raedler, MD^*, Achim von Goedecke, MD^*, Andreas Mayr, MD^*, Guido Hinterberger, Ch. Aspoeck, MD, Cornelia Lass-Floerl, MD, and Arnulf Benzer, MD^*

*Department of Anaesthesia and Department of Hygiene, University Hospital Innsbruck, Innsbruck, and Department of Hygiene, General Hospital St. Poelten, St. Poelten, Austria

Correspondence to: Dr. A Benzer, Department of Anesthesia and Critical Care Medicine, University Hospital Innsbruck, A-6020 Innsbruck, Austria. Address e-mail to arnulf.benzer{at}uibk.ac.at

	Abstract

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Catheter-related bloodstream infections (CRBSI) are a common problem in patients after central venous catheterization. Using DNA analysis we compared bacteria found on the tip of central venous catheters removed because of clinical signs of CRBSI with bacteria found on needle, dilator, and guidewire used for insertion of these catheters. In five of seven central venous catheters removed because of clinical signs of CRBSI, bacteria on the catheter tip were genetically identical to bacteria found on the insertion device, proving that catheter contamination in these cases was caused by contacting bacteria during the initial puncture. These findings may be important for antibiotic prophylaxis or therapy in patients at risk for CRBSI.

IMPLICATIONS: In five of seven central venous catheters removed because of clinical signs of catheter-related blood infections, DNA analysis showed bacteria found on the catheter tip to be identical with bacteria found on the puncture kits used for insertion of these catheters.

	Introduction

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Penetrating the natural defense barrier of the skin, central venous catheter (CVC)-induced catheter-related bloodstream infection (CRBSI) has become a common cause of nosocomial bacteremia, thereby substantially contributing to morbidity and mortality in the critically ill. The probability of insertion of a CVC has been estimated at nearly 50% per day in intensive care patients, with an average of 5.3 CRBSIs per 1000 catheter days (1). Microorganisms can be found on the distal tip of the CVC 90 minutes after puncture (2), but no data have been reported about specific bacteria impacted by the catheter insertion procedure itself in patients developing clinical signs of CRBSI.

Our study was performed to test the hypothesis that bacteria impacted during central venous puncture may be identical to those colonizing the catheter tip several days later in patients with suspected CRBSI. We focused on patients in whom a CVC was inserted prior to routine major abdominal, cardiac, and orthopedic surgery, reasoning that such patients represent a clinically relevant majority of those at risk for CRBSI and that the results of such an investigation might therefore have practical implications.

	Methods

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A total of 112 complete CVC insertion kits were assessed for contamination after use. The introducer needle, dilator, and guidewire were collected separately in sterile containers and sampled for microorganisms. In seven patients with clinical evidence of CRBSI (redness around the insertion site, fever, or bacteremia) catheter tips were sampled immediately after catheter removal. Bacteria found on CVC tips were compared with bacteria found on the corresponding insertion equipment.

The study protocol was approved by the IRB; patient consent was waived. CVCs (triple- and four-lumen CVC [Arrow International, Inc., Reading, PA]) were inserted according to institutional guidelines of the intensive care unit (ICU) of the University of Innsbruck. The aseptic technique is specified by protocol and includes thorough disinfection of hands before putting on sterile coat, sterile gloves, mask, and cap. The skin was thoroughly disinfected with Isozid H® (Gebro Pharma, Fieberbrunn, Austria), waiting 1 min so that the solution could achieve its maximum disinfecting effect on the skin. The area around insertion was generously covered with sterile cloths before CVC insertion was performed. After insertion, the insertion site was disinfected once daily. Single-use gloves were used when the CVC was manipulated. No prophylactic antibiotics were administered.

If there were no signs of CRBSI, the CVCs were removed after 14 days according to institutional guidelines. If there were clinical signs of CRBSI such as redness around the insertion site with fever and/or clinical symptoms of an infection, the CVC was removed immediately. A solitary redness around the insertion site without fever or clinical signs of infection was tolerated until day 10. If the CVC was placed for more than 10 days and redness occurred, it was removed.

Detection of bacterial contamination proceeded as follows: Needles, dilator, and guidewire were transferred into 5 mL Tryptic Soy Broth® (Merck, Darmstadt, Germany), vortexed, and incubated under aerobic conditions at 37°C. In order to determine the colony and to concurrently differentiate between microorganisms, each sample was applied on Columbia Blood Agar (Becton Dickinson, Cockeysville, MD) at time 0, 24, and 48 h and incubated at 37°C for 48 h. Differential analysis of the microorganisms was effected following incubation using morphological, physiological, and serological criteria. Plasma coagulase negative and positive staphylococci were identified using a commercial test kit (Pastorex Staph Plus®, Sanofi Pasteur Diagnostics, Chaska, MN) and the classical tube coagulation test. Other Gram-positive cocci, Gram-negative rods, and yeasts were identified by using commercially available test kits (API®, Bio Merieux, Marcy Lètoile, France). Aerobic spore forming bacteria, microscopically examined as Gram-positive rods, were identified by catalase production and aerobic endospore formation. All laboratory procedures were performed under a laminar-flow hood, with the worker wearing protective gloves. The specimens were processed promptly upon arrival in the laboratory.

To test our hypothesis we used a chromosomal DNA restriction pattern produced by pulsed-field gel electrophoresis (PFGE). All strains isolated from a single patient were compared for their relationship by means of molecular typing using PFGE (3). Enzyme restriction was performed with SmaI® (Boehringer Mannheim, Ingelheim, Germany), and electrophoresis with the CHEF MAPPER® electrophoresis cell (Bio-Rad, Melville, NY). Bacteriophage lambda DNA concatamers were used as size standards. The gels were stained with ethidium bromide and photographed; interpretation of the PFGE banding patterns was done visually according to international guidelines (Fig. 1).

View larger version (38K): [in this window] [in a new window]   Figure 1. Pulsed-field gel electrophoresis (PFGE) of SmaI digested chromosomal DNA of two strains (catheter-tip; dilator) of staphylococcus-epidermidis showing similar PFGE banding patterns in Patient 1 (m = molecular weight markers).

	Results

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	Discussion

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Our study found that in five of seven patients with clinical signs of CRBSI, the initial catheter insertion procedure itself was the first step to developing contamination of the CVC, because it mechanically contacted bacteria. The microorganisms most frequently found in our study were coagulase-negative staphylococci, which are typical skin organisms. This is in agreement with the literature, which shows that coagulase negative staphylococci, the predominant species on the human skin, are the most common agents of catheter-related infections (1). Microorganisms that colonize the skin of patients, such as Staphylococci, Candida, and Bacillus species, cause the majority of these infections. Assuming that catheter contamination can occur during the insertion procedure, some centers administer antibiotics empirically and prophylactically during insertion of a CVC (1). Even in the case of suspected CRBSI, antibiotic therapy is often initiated empirically and narrowed after identification of a specific pathogen.

On the basis of our data, it seems likely that in five of seven patients early knowledge of the type of microorganisms found on insertion devices would have been able to influence therapeutic approaches (i.e., [non]removal of CVC depending on clinical situation, specific antibiotic therapy). If the earliest samples are taken from the catheter tip only at its removal, the time loss for treatment can be significant, especially in the critically ill. In our study, the rate of contamination and colonization of the insertion device (2) as well as the incidence of CRBSI was similar to results found by others (4).

The present investigation, which was part of a quality assurance program, found a very high incidence of contamination due to insertion of a CVC, even when good clinical practice was used for insertion. Maximum care is needed for proper prepping and aseptic insertion. Unfortunately, even when this is done and the frequency of insertion-derived CRBSIs is reduced, insertion per se will probably remain an inevitable cause of CRBSI.

Unfortunately, most techniques used for diagnosis of catheter colonization require removal of the catheter, and the catheter removed is rarely contaminated. Other techniques, i.e., timing of positive blood culture growth from a CVC versus a peripheral blood sample, showed a highly variable sensitivity and specificity dependent on indwelling time (5). Moreover, in uncomplicated cases, when the infecting organism is a coagulase-negative staphylococcus and there is no suspicion of local or metastatic complications, the CVC may be retained.

However, when a metastatic complication is suspected and the CVC is removed, a correlation between bacteria found on guidewire/dilator/needle and bacteria found on CVC tip confirms the cause of the bloodstream infection. If no correlation is found, further investigation of the source of infection is needed. This additional information is particularly helpful for patients with many possible sources for the bloodstream infection, such as trauma patients. This can be seen as quality management of the therapeutic measures undertaken.

Microbiological analysis of insertion devices costs 20 Euros per device (needle + dilator + guidewire = 60 Euros). We believe that in high-risk patients, such as those in an ICU, this method is a very small financial investment for a tool that evaluates whether an antibiotic regimen is adequate, whether the CVC is really the cause of a blood stream infection, or whether further investigations are necessary to determine the source of infection. It should be kept in mind that the cost of one CRBSI case is estimated to range from 3,700 Euros to 29,000 Euros (1). Inadequate treatment or inaccurate diagnoses in the case of a CRBSI patient will increase hospitalization costs and threaten health and life in a very vulnerable time frame.

Our investigation confirms previous findings that in a majority of patients with clinical signs of CRBSI, microorganisms from the patient’s own skin contaminate the CVC (1,2,4,5); a simple antibiogram derived early from bacteria found on the catheter insertion device may provide additional cost- and time-effective information needed for prophylaxis or treatment of CRBSI.

	References

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1. Mermel LA. Prevention of intravascular catheter-related infections. Ann Intern Med 2000; 132: 391–402.[Abstract/Free Full Text]
2. Elliott TS, Moss HA, Tebbs SE, et al. Novel approach to investigate a source of microbial contamination of central venous catheters. Eur J Clin Microbiol Infect Dis 1997; 16: 210–3.[Web of Science][Medline]
3. Livesley MA, Tebbs SE, Moss HA, et al.. Use of pulsed field gel electrophoresis to determine the source of microbial contamina- tion of central venous catheters. Eur J Clin Microbiol Infect Dis 1998; 17: 108–12.[Web of Science][Medline]
4. Poldermann KH, Girbes ARJ. Central venous catheter use. Part 2: infectious complications. Intensive Care Med 2002; 28: 18–28.[Web of Science][Medline]
5. Lane RK, Matthay MA. Central line infections. Curr Op Crit Care 2002; 8: 441–8.[Medline]

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