Infection is the main treatment-related cause of mortality in cancer patients. Rapid and accurate diagnosis to facilitate specific therapy of febrile neutropenia is therefore urgently warranted. Here, we evaluated a commercial PCR-based kit to detect the DNA of 20 different pathogens (SeptiFast) in the setting of febrile neutropenia after chemotherapy. Seven hundred eighty-four serum samples of 119 febrile neutropenic episodes (FNEs) in 70 patients with hematological malignancies were analyzed and compared with clinical, microbiological, and biochemical findings. In the antibiotic-naïve setting, bacteremia was diagnosed in 34 FNEs and 11 of them yielded the same result in the PCR. Seventy-three FNEs were negative in both systems, leading to an overall agreement in 84 of 119 FNEs (71%). During antibiotic therapy, positivity in blood culture occurred only in 3% of cases, but the PCR yielded a positive result in 15% of cases. In six cases the PCR during antibiotic treatment detected a new pathogen repetitively; this was accompanied by a significant rise in procalcitonin levels, suggestive of a true detection of infection. All patients with probable invasive fungal infection (IFI; n ‫؍‬ 3) according to the standards of the European Organization for Research and Treatment of Cancer had a positive PCR result for Aspergillus fumigatus; in contrast there was only one positive result for Aspergillus fumigatus in an episode without signs and symptoms of IFI. Our results demonstrate that the SeptiFast kit cannot replace blood cultures in the diagnostic workup of FNEs. However, it might be helpful in situations where blood cultures remain negative (e.g., during antimicrobial therapy or in IFI).While systemic infection is the most common cause of a febrile neutropenia episode (FNE) with significant effects on morbidity and mortality, only 30% of blood cultures taken at the onset of fever are positive (11,15). Nonetheless, patients with FNEs are treated with broad-spectrum antimicrobial agents regardless of the result of their blood culture (7) because potentially life-threatening infections need early treatment to ensure better clinical outcome. Noninfective causes of a systemic reaction culminating in a rise in temperature such as tumor fever, drug fever, or transfusion reactions complicate the diagnostic challenge in cancer patients. In addition, the etiology of a deterioration of an FNE during antimicrobial therapy is often difficult to elucidate, since blood cultures are infrequently positive once effective antimicrobial therapy has started (4). Pathogens such as molds which are rarely found in blood cultures are not uncommon in patients with FNEs, particularly if they suffer from hematological malignancies. For these reasons, FNE is one of the conditions where new diagnostic tools to distinguish an infection from a nonmicrobial cause for fever or to identify rare pathogens are most urgently needed. In the past, raised levels of indirect markers such as procalcitonin (PCT) and interleukin 6 (3, 16) have been shown to be ...

Contamination of polymerase chain reaction (PCR) reagents continues to be a major problem when consensus primers are used for detection of low concentrations of bacterial DNA. We designed a real-time polymerase chain reaction (PCR) for quantification of bacterial DNA by using consensus primers that bind specifically to the 16S region of bacterial DNA. We have tested four different methods of decontamination of PCR reagents in a project aimed at detecting bacterial DNA at low concentrations: deoxyribonuclease (DNAse) treatment, restriction endonuclease digestion, UV irradiation, and 8-methoxypsoralen in combination with long-wave UV light to intercalate contaminating DNA into double-stranded DNA. All four methods result in inhibition of the PCR reaction, and most of the decontamination procedures failed to eliminate the contaminating bacterial DNA. Only the DNAse decontamination proved to be efficient in eliminating contaminating DNA while conserving PCR efficiency. All four decontamination methods are time consuming and have the possibility of carrying new contamination into the reaction mixture. However, decontamination with DNAse may help, together with the use of highly purified PCR reagents, in detecting small amounts of bacterial DNA in clinical specimens.

We introduce a consensus real-time PCR protocol for the detection of bacterial DNA from laboratoryprepared specimens such as water, urine, and plasma. This prototype detection system enables an exact Gram stain classification and, in particular, screening for specific species of 17 intensive care unit-relevant bacteria by means of fluorescence hybridization probes and melting-curve analysis in a one-run experiment. One strain of every species was tested at a final density of 10 6 CFU/ml. All bacteria examined except Staphylococcus aureus and Staphylococcus epidermidis could be differentiated successfully; S. aureus and S. epidermidis could only be classified as "Staphylococcus species." The hands-on time for preparation of the DNA, performance of the PCR, and evaluation of the PCR results was less than 4 h. Nevertheless, this prototype detection system requires more clinical validation.The early detection and adequate treatment of bacterial infections are critical for successful outcomes for patients with systemic infections (5).Efforts aimed at the species-specific detection of bacterial DNA have been made (1-4, 6, 8, 9). This approach would require several PCR experiments in series or in parallel, which would be expensive and time-consuming. Therefore, the aim of this study was to introduce a prototype system for the detection of bacterial DNA that enables a hands-on time of less than 4 h, including the time for the preparation of DNA and evaluation of the PCR results. For this purpose we developed a prototype rapid real-time PCR protocol for the amplification of bacterial DNA from biological fluids. This approach enables Gram stain classification with the goal of the reliable detection and differentiation of significant pathogens in the intensive care unit (ICU) by means of fluorescence hybridization probes with calculated mismatches and melting-curve analysis in a one-run experiment. MATERIALS AND METHODS Whole organisms of 17 ICU-relevant bacteria species (Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Proteus vulgaris, Haemophilus influenzae, Enterobacter aerogenes, Enterobacter cloacae, Serratia marcescens, Bacteroides fragilis, Acinetobacter baumannii, Legionella pneumophila, Stenotrophomonas maltophilia, Enterococcus faecalis, Enterococcus faecium, Streptococcus pyogenes, Staphylococcus epidermidis, Staphylococcus aureus)were spiked in different biological fluids (water, plasma, urine), and the DNA was extracted and used for subsequent experiments. A quantitative PCR was performed on a real-time PCR instrument (LightCycler; Roche) with broad-range primers for amplification of a highly conserved region of the bacterial 16S DNA locus. The PCR products were hybridized with two fluorescence dye-labeled hybridization probes that specifically bind only to either gram-positive or gram-negative bacteria. The different fluorescence signals (640 and 705 nm, respectively) were detected by the LightCycler instrument and enabled differentiation of bacteria according to their Gram stain classificati...

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We developed a consensus real-time PCR protocol that enables us to detect spiked bacterial 16S DNA from specimens such as water, urine, plasma, and sputum. The technique allows an exact Gram stain classification of 17 intensive care unit-relevant bacteria by means of fluorescence hybridization probes. All tested bacteria were identified correctly, and none gave a false-positive signal with the opposite Gram probe.