Use of the quinolones for the prophylaxis and therapy of infections in immunocompromised hosts

Trends in fluoroquinolone (ciprofloxacin) resistance in enterobacteriaceae from bacteremias, England and Wales, 1990-1999

The Public Health Laboratory Service receives antibiotic susceptibility data for bacteria from bloodstream infections from most hospitals in England and Wales. These data were used to ascertain resistance trends to ciprofloxacin from 1990 through 1999 for the most prevalent gram-negative agents: Escherichia coli, Klebsiella spp., Enterobacter spp., and Proteus mirabilis. Significant increases in resistance were observed for all four species groups. For E. coli, ciprofloxacin resistance rose from 0.8% in 1990 to 3.7% in 1999 and became widely scattered among reporting hospitals. The prevalence of resistance in Klebsiella spp. rose from 3.5% in 1990, to 9.5% in 1996 and 7.1% in 1999, while that in Enterobacter spp. rose from 2.1% in 1990 to 10.5% in 1996 and 10.9% in 1999. For both Klebsiella and Enterobacter spp., most resistance was localized in a few centers. Resistance was infrequent and scattered in P. mirabilis, but reached a prevalence of 3.3% in 1999.

Integrating fluoroquinolones into the hospital formulary

With the increasing availability of new agents, selection of fluoroquinolones for formulary inclusion can be difficult. Appropriate evaluation of the important characteristics (pharmacokinetic and pharmacodynamic properties, antimicrobial activity, efficacy, tolerability, cost) of these agents should allow selection of the most cost-effective ones. Evidence from in vitro studies and clinical trials indicates differences exist among fluoroquinolones, especially in terms of activity against gram-positive, aerobic organisms. For selected clinical situations, it may be important to choose an agent that is available in both intravenous and oral formulations. Comparative drug costs, as well as costs associated with potential clinical failure and adverse events, should be evaluated carefully. Dosage regimens should be considered, as shorter durations of therapy and less frequent dose administration may lead to reduced labor costs and increased patient compliance, thereby improving effectiveness and economic efficiency.

The use of itraconazole as prophylaxis against invasive fungal infection in blood and marrow transplant recipients

Invasive fungal infections play a key role in contributing to morbidity and mortality in patients undergoing treatment for haematological malignancies and related diseases. Risk factors for development of invasive fungal infections after blood or bone marrow transplantation include the use of broad-spectrum antibiotics, steroids, mismatched or unrelated donor transplant, right atrial catheters, and prolonged or profound neutropenia. Previous attempts at use of oral itraconazole as antifungal prophylaxis in the setting of chemotherapy-induced neutropenia were unsuccessful because of its poor absorption in capsule form. Itraconazole-cyclodextrin is well absorbed even in the presence of chemotherapy-induced neutropenia. Plasma levels of 250-500 ng/ml are required for prophylaxis. Studies to date show a favourable outcome in patients receiving itraconazole as prophylaxis against invasive fungal infections, although many studies looked at small numbers of patients and the incidence of invasive fungal infection in the control groups was low, prohibiting meaningful statistical evaluation. Fungi differ in their sensitivity to antifungal agents, and itraconazole is not the agent of choice in all patients. With the widespread use of antifungal prophylaxis, the possibility of resistance to antifungal agents and an increase in the number of invasive fungal infections caused by ubiquitous fungi previously considered nonpathogenic must be considered as potential problems.