Changing causes of septicaemia in paediatric oncology patients: effect of imipenem use. 
One hundred and fifty-four episodes of septicaemia occurred in 78 patients on a Paediatric Oncology Unit over 2 years.  Septicaemias with Gram-positive bacteria were more common than with Gram-negative organisms, coagulase-negative staphylococci (CNS) being the commonest pathogens.  The mortality rate in patients with septicaemia was 1.9%.  Azlocillin and gentamicin comprised the first-line of empirical antibiotic therapy for suspected infection for the first 10 months of the study; imipenem with cilastatin, as monotherapy, was used subsequently.  More isolates of enterococci, and fewer isolates of Enterobacter, were seen after the introduction of imipenem.  The use of imipenem was associated with an increased frequency of resistance to flucloxacillin in CNS.  Such strains have been shown to contain sub-populations of cells that are resistant to imipenem.  A clinical response was achieved in 82.9% of septicaemic episodes treated with imipenem, compared with 62.7% for azlocillin and gentamicin.  However, imipenem as monotherapy may not be appropriate in central venous catheter related infections, owing to the frequent occurrence of imipenem-resistant organisms, CNS and Pseudomonas spp.,  in this situation.