gms | German Medical Science

Background: Bloodstream infections (BSIs) due to bacteria and invasive fungal infections (IFIs) are major causes of infection-related mortality in patients with cancer. Timely diagnosis of severe infection in the neutropenic host is especially problematic due to nonspecific clinical signs and symptoms and low sensitivity of conventional cultures. Blood cultures (BC) are positive in only 20-50% of febrile neutropenic events, and slow. Approaches encompassing nucleic acid-based amplification platforms and serological tests are therefore increasing used to facilitate time-critical diagnosis.

Aim: Determine if the real time PCR and DNA sequencing techniques used to identify the main pathogens and some important antimicrobial resistance genes causing bloodstream infections can improve the early diagnosis and adequate therapy in oncology pediatric patients. Methods: During October 2010 to June 2012 we conducted a prospective study, on Oncology Pediatric Institute (IOP-GRAACC-Bra zil). BCs were collected from all patients with fever and/or other signs of infections and blood samples in tubes containing EDTA K2 gel were obtained for molecular analysis directly from blood. BCs were performed using the BACTEC® 9240 system. Total DNA was extracted from the 500µL BC used BRAZOL® method, following resistance genes were detected: blaIMP; blaSPM (metallo-ß lactamase); vanA and vanB (glycopeptideos resistance); blaSHV; blaTEM; blaCTX (extended-spectrum ß-lactamase-ESBL-carbapenen resistance), and mecA gene (meticilin resistance).

Results: 93 BSIs by BACTEC system were studied in 64 pediatric patients with cancer. The average age was 7.8 years; 57.8% males. The most frequent diagnosis was ALL 18.8% followed by CNS tumor and HSCT (hematopoietic stem cell transplantation) 10.9% each. Of 93 episodes; 46 were neutropenic; 79 had central line; 33.3% ocurred before 72 hours of hospitalization; 15 (16.1%) were polimicrobial. Of 78 episodes monomicrobial, 44 (56.4%) were by Gram positive bacteria: 19 (43.2%) SCoN, 10 (22.7%) S. aureus, 9 (20.4%) Streptococcus spp, 9 (20.4%) gram positive bacilli, 2 (4.6%) enterococos, 28 (35.9%) gram negative bacteria: with 15 enterobacterias; 10 non fermented and 3 others; yeasts: 6 (7.7%) For gram positive bacteria: 26 (89.6%) of Staphylococcus were meticilin resistant, and 1(50%) of Enterococcus were vancomycin resistant. For gram negative bacteria 10 (35.7%) were cefepime resistant and 6 (21.4%) meropenem resistant. In 32.1% of 78 monomicrobial episodes the empiric antibiotic therapy was considered adequate and 5 (6.4%) were corrected according final result. Detection of mecA gene was concordant in 86% and detection of van A gene was 100%. For gram negatives blaSPM was concordant in 75% of Pseudomonas aeruginosa and blaCTX and blaTEM was 63% concordant for enterobacteriaces.

Conclusion: Real time PCR can be an useful additional tool in the early identification of pathogens and antimicrobial resistance genes in the bloodstream infections of pediatric oncologic patients.