Systemic Candida Infections A Preliminary Study Of The Molecular Diagnostics

Systemic candidiasis is a major nosocomial infection in patients given immunosuppressive chemotherapy for cancer treatment or organ transplantation and in patients undergoing cordial or abdominal surgery. Patients with candidemia have a poorer prognosis than those with nosocomial bacteremia. Mortality rate among those with systemic candidiasis remain high, ranging from 50%~80%, despite adequate treatment. However, the sensitivity of blood cultures for diagnosis of systemic candidiasis is low at the early stage of the infection. Recently, non-culture-dependent assays such as PCR assays have been developed for the earliest possible diagnosis of systemic candidiasis.It has been demonstrated that PCR can be performed either on blood samples or on urine samples. However, the efficiencies of the same PCR assay applied simultaneously to blood or urine have never been formally compared. In the blood sample, there are at least two types of samples, whole blood samples and plasma samples. Similarly, there are also at least two types in urine samples, supernatant liquid and sediment. Indeed, only free template DNA should be detectable in plasma samples and urinous supernatant liquid, since fungal cells are eliminated by centrifugation without having been lysed to release intracellular DNA. By contrast, when whole blood samples and urine sediment are used, both free DNA and intracellular DNA could be present when the sample is drawn from the patient. However, because of the presence in blood and urine of PCR inhibitors, such as hemoglobin, a decontamination step, including lysis of blood cells and washing, is performed first. Thus, depending on the sample used, the origin of the detected DNA probably varies. This may result in a difference in the sensitivity of the assay and in its clinical significance. To our knowledge these issues have not been fully investigate. This is why, in the present study, our efforts have been focused on that question. We have used a mice model of experimental candidemia specifically developed in this laboratory. We used DNA coding for the 18S rRNA as the target for amplification, and we have compared the positivities of the PCR on blood and urine, using cultures as the reference assay.First, according to the index of international experimental animal, ICR mice were used in these studies. Immunosuppression was induced by...