Superinfections during antimicrobial treatment with betalactam-aminoglycoside combinations in neutropenic patients with hematologic malignancies.

The frequency, etiology and risk factors of superinfections during and/or within one week after antibiotic therapy with betalactam-aminoglycoside combinations were evaluated in 631 patients with hematologic malignancies admitted to the Institute of Hematology of Rome from January 1982 to December 1984. 356 patients (56%) developed 402 episodes of proven or presumed infection. Of these patients, 78 developed 102 superinfections. Overall, superinfections responded less satisfactorily to antibiotic therapy than the primary febrile episodes (63% vs. 85%). The distribution of etiologic agents of superinfections differed from those responsible for primary infections, since fungi and anaerobes (especially Clostridium difficile) were mostly isolated after antibiotic therapy had begun. Moreover, among aerobic bacteria, frequently antibiotic-resistant species, such as Pseudomonas aeruginosa, Streptococcus faecalis and Staphylococcus epidermidis were the leading etiologic agents of superinfection. The risk of superinfection appeared to increase with the depth and persistence of granulocytopenia. On the other hand, the length of hospitalization, length of previous antibiotic therapy, previous chemoprophylaxis and presence of indwelling venous catheter did not affect the risk of superinfection.