Anticipative Diagnosis of Central Venous Catheter Related Bloodstream Infections Using Biphasic PNA FISH and Gram Stain/AOLC Tests

Management of patients with hematologic malignancies, renal failure or diseases requiring intensive care often necessitates the use of central venous catheters (CVC). Beside obvious advantages CVCs bear a great risk for local or systemic infections. In the US estimated 250 000 catheter-related blood stream infection (CRBSIs) occur each year with mortality rates of 12-25%. Diagnosis of CRBSIs remains challenging as systemic clinical signs are unspecific and local signs of infection are often absent. Conventional methods for diagnosing CRBSIs require removal of the CVC. However, only 15% of CVCs removed in patients with clinical suspicion of CRBSI prove to be infected. It has been shown that CRBSI can also be detected by the differential time to positivity (DTP) method without catheter removal. The Gram stain/acridine-orange leukocyte cytospin (AOLC) test and PNA FISH test are another methods for the diagnosis of CRBSI that does not require the removal of the CVC and additionally have shown to be fast. Up to date methods for diagnosis of CRBSI are performed only when CRBSI is clinically suspected. Thus, patients may actually suffer from CRBSI and are at risk to concurrently suffer from or develop complications like endocarditis or septic embolism when diagnostic procedures for the detection of CRBSI are introduced. Since CRBSIs are not entirely preventable by strict hygiene measures earlier diagnosis of CRBSI in subclinical stages is desirable to avoid CRBSI-associated morbidity and mortality. Previously a pilot study showed that Gram stain/AOLC screening of CVCs in neutropenic patients was a useful test to predict the development of CRBSI on average 48 hours before the diagnosis was established by routine measures. In the pilot study Gram stain/AOLC screening test exhibited high specificity whereas sensitivity was moderate. PNA FISH is a specific slide-based staining technique that provides pathogen identification from blood samples containing a given amount of bacteria or fungi within a 1,5 hours. PNA FISH test has a slightly lower detection limit compared to Gram stain/AOLC which might therefore result in higher sensitivity when used as a screening tool. The aim of the project is to investigate a more sensitive and specific test for anticipative diagnosis of CRBSI using biphasic PNA FISH test compared to Gram stain/AOLC test.