Clinical implications of icaA and icaD genes in coagulase negative staphylococci and Staphylococcus aureus bacteremia in febrile neutropenic pediatric cancer patients

Abstract

Staphylococci are the most frequently isolated organisms from blood cultures of febrile neutropenic (FN) cancer patients. We aimed to define the nature of these isolates by studying the prevalence of icaA and icaD genes in coagulase-negative staphylococci (CoNS) and Staphylococcus aureus isolates in relation to clinical and microbiological features. Fifty-five CoNS and S. aureus isolates from blood cultures of FN pediatric patients receiving chemotherapy were tested for slime production using Congo red agar plate test (CRA test), and for the presence of icaA and icaD genes by PCR. Of the CoNS isolates, eight were positive for ica genes, and three were slime positive/ica negative. A total of 11 (24.4%) cases of CoNS bacteremia were either ica genes or CRA test positive. There was a concordance between ica genes and CRA test positivity (P < 0.001). S. aureus isolates exhibited icaA and icaD genes more than CoNS isolates (P = 0.03). Vancomycin was significantly more prescribed in episodes of ica-positive cases (P = 0.029). The results of the present study support the hypothesis that the ica genes are important virulence markers for clinically significant CoNS isolates, indicating their ability to produce slime. This could be used to assign a group with higher risk FN. On the other hand, absence of these genes may permit, along with other clinical criteria, the consideration of a low-risk FN episode and allow for safe early discharge.