Diagnosis by real-time polymerase chain reaction of pathogens and antimicrobial resistance genes in bone marrow transplant patients with bloodstream infections

BACKGROUND Early identification of pathogens and antimicrobial resistance in bloodstream infections (BSIs) decreases morbidity and mortality, particularly in immunocompromised patients. The aim of the present study was to compare real-time polymerase chain reaction (PCR) with commercial kits for detection of 17 pathogens from blood culture (BC) and 10 antimicrobial resistance genes. METHODS A total of 160 BCs were taken from bone marrow transplant patients and screened with Gram-specific probes by multiplex real-time PCR and 17 genus-specific sequences using TaqMan probes and blaSHV, blaTEM, blaCTX, blaKPC, blaIMP, blaSPM, blaVIM, vanA, vanB, and mecA genes by SYBR Green. RESULTS Twenty-three of 33 samples identified by phenotypic testing were concordantly positive by BC and real-time PCR. Pathogen identification was discordant in 13 cases. In 12 of 15 coagulase-negative staphylococci, the mecA gene was detected and four Enterococcus spp. were positive for vanA. Two blaCTX and three blaSHV genes were found by quantitative PCR. The blaKPC and metallo-β-lactamase genes were not detected. Five fungal species were identified only by real-time PCR. CONCLUSIONS Real-time PCR could be a valuable complementary tool in the management of BSI in bone marrow transplants patients, allowing identification of pathogens and antimicrobial resistance genes.