Causes of death in febrile granulocytopenic cancer patients receiving empiric antibiotic therapy

Características clínicas y microbiológicas de pacientes con neutropenia febril en un hospital universitario

Objetivo: Describir las características clínicas, demográficas, frecuencia, tipo de aislamientos microbiológicos y resistencia a los antimicrobianos de pacientes con neoplasias hematológicas que presentaron como complicación neutropenia febril en el Hospital Universitario de San IgnacioMétodos: Estudio descriptivo observacional, se tomaron datos de historias clínicas de los pacientes adultos hospitalizados en la Unidad de Hematología y Trasplante de Médula Ósea, que cumplieron criterios de neutropenia febril entre enero de 2013 y diciembre de 2014Resultados: se recolectaron 345 episodios de neutropenia febril, correspondientes a 193 pacientes. Se documentó foco infeccioso en el 68,1% de los episodios, con aislamiento microbiológico en el 62.9% de los episodios, con predominio de bacilos gram negativos, en 63,7% de los casos, seguido por los cocos gram positivos en 27,9% y hongos en 4,9%. En cuanto a los mecanismos de resistencia, en los aislamientos Escherichia coli y Klebsiella peumoniae se encontró producción de Beta Lactamasas de Espectro Extendido (BLEEs) en 17,5 y 13,8%; Carbapenemasas tipo KPC en 1,25 y 2,8% respectivamente. En cuanto a Staphylococcus aureus, se encontró resistencia a meticilina en 6,8% de los aislamientos. Mortalidad asociada a infección en 16,5% de los casos.Conclusión: En pacientes con Neoplasias Hematológicas con neutropenia febril post quimioterapia en el Hospital Universitario de San Ignacio encontramos alta probabilidad de documentación de foco infeccioso, con predominio de microorganismos gram negativos, especialmente enterobacterias; con comportamiento similar en pacientes post trasplante de precursores hematopoyéticos.

[The patient with leukemia in the intensive care unit]

Leukämiepatienten entwickeln häufig leukämie- oder therapieassoziierte kritische Komplikationen, die eine intensivmedizinische Behandlung nötig machen. Bei vielen dieser Patienten besteht ein kuratives Therapieziel und sie haben die Aussicht auf eine Langzeit- Remission, vorausgesetzt die Phasen der therapieassoziierten Komplikationen können erfolgreich intensivmedizinisch beherrscht werden. Nachfolgend sollen typische Komplikationen bei Leukämiepatienten, die eine intensivmedizinische Therapie erforderlich machen, beziehungsweise für den Leukämiepatienten typische Aspekte bei der Anwendung invasiver Techniken auf der Intensivstation, das Management auf der Intensivstation, die aktuelle Studienlage über intensivmedizinische Maßnahmen bei Leukämiepatienten und ethische Aspekte abgehandelt werden.

Piperacillin/tazobactam vs ceftazidime in the treatment of neutropenic fever in patients with acute leukemia or following autologous peripheral blood stem cell transplantation: a prospective randomized trial

Piperacillin/tazobactam was compared with ceftazidime for the empirical treatment of febrile neutropenia in patients with acute leukemia or following autologous peripheral blood stem cell transplantation. Owing to inclusion criteria, it was possible for the same patient to be randomized several times. A total of 219 individual patients were admitted to a prospective randomized clinical study: 24 patients were included twice. Patients (23.5%) remained afebrile. Patients who developed febrile neutropenia were randomized to receive intravenous ceftazidime (n = 74 patients, group I) or piperacillin/tazobactam (n = 87 patients, group II). Response to first-line antibiotic treatment was seen in 55% (group I) and 53% (group II). After the addition of vancomycin, a further 19% (group I) and 24% (group II) of the patients became afebrile. Causes of fever were: microbiologically documented infection in 36 and 34 patients of group I and II; Clostridium difficile in eight and 12 patients of group I and II, and fever of unknown origin in 30 and 41 patients of group I and II. One patient died in each group. Single-agent therapy with piperacillin/tazobactam is as effective as ceftazidime in the treatment of neutropenic fever and is well tolerated. Direct and indirect costs of both treatment regimes are equivalent.

Gammagrafía con 99mTc-ceftizoxima en ratas normales y en ratas con absceso inducido

This study aimed to investigate the biodistribution of the 99mTc-ceftizoxime in normal rats and in rats bearing septic and sterile induced abscess.

MATERIAL AND METHODS

Three groups of rats were studied. a) Six normal rats b) 15 rats with E. coli induced abscess and c) 15 rats with sterile zymosan induced abscess. Septic abscess was induced with 2 x 10(8) colony forming units of E. coli and sterile one with 0.1 mL of 5% sterile Zymosan. 24 h after the abscess induction, 12 MBq of 99mTc-CFT were injected iv. and whole body images were collected at 30 min, 1, 2, 4 and 6 h p.i. Areas of interest were drawn and lesion/background index was calculated. The 6 normal rats were scanned at the same times, killed at 6 h p.i and kidney, liver, spleen, lung, heart and muscle activity were measured. Each organ was weighed, cut and its activity measured. Parallelly, the biological activity of the labeled antibiotic and its binding to the E. coli and S. aureus bacteria were analyzed.

RESULTS

High biliary excretion was seen in all rats. Organ measurement showed the maximal uptake in kidney and very low uptake in muscles. Mean +/- s.d abscess/background ratio at 30 min, 1, 2, 4 and 6 h were 2.60 +/- 0.36, 2.67 +/- 0.66, 2.6 0 +/- 0.58, 2.78 +/- 0.84, 3.24 +/- 1.00 for septic abscess and 2.37 +/- 0.39, 2.10 +/- 0.38, 1.97 +/- 0.34, 1.82 +/- 0.25, 1.65 +/- 0.23 for aseptic abscess. The 99mTc-CFT uptake was significantly higher in the septic abscess than in sterile one (p < 0.05). The 99mTc-CFT uptake in the septic abscess remains stable or increases until along the 6 h. The 99mTc-CFT uptake in the aseptic abscess decreases along the time.

CONCLUSIONS

The scintigraphy with 99mTc-CFT seems able to differentiate sterile inflammation from infection. High biliary excretion limits its application in abdomen. Main application could be diagnosis of osteoarticular infection.

CD4 lymphopenia as a risk factor for febrile neutropenia and early death after cytotoxic chemotherapy in adult patients with cancer

BACKGROUND

Lymphopenia is frequently observed in patients with cancer and correlates with the risk of febrile neutropenia and early death after chemotherapy. The phenotype of the depleted lymphocyte populations was investigated in the current study.

METHODS

Peripheral blood lymphocyte subsets (CD3, CD4, CD8, CD19, CD56) were quantified on Day 1 using fluorescence-activated cell sorting in a prospective study of 213 patients with cancer treated with chemotherapy in a single oncology ward during 12 months. Correlations between lymphocyte phenotype, clinical characteristics, and the risk of febrile neutropenia and early death within 31 days after chemotherapy were investigated in univariate and multivariate analyses.

RESULTS

Total lymphocyte count and CD3, CD4, and CD8 lymphocyte subsets were significantly lower in patients who experienced febrile neutropenia. Total lymphocyte count and CD3, CD4, CD8, CD19, and CD56 lymphocyte subsets were significantly lower in patients who died within 31 days after chemotherapy. Using logistic regression, CD4 lymphopenia (< 450/muL; odds ratio [OR] = 2.9, 95% confidence interval [CI] = 1.5-5.9) and the dose of chemotherapy (OR = 3,9, 95% CI = 2.0-7.8) were both identified as independent risk factors for febrile neutropenia. Fifty-four percent of patients with both risk factors experienced febrile neutropenia. CD4 lymphocyte count < 450/muL was also an independent risk factor for early death (OR = 7.7, 95% CI = 1.7-35). Thirteen percent of patients with a CD4 lymphocyte count </= 450/muL died within 31 days after chemotherapy. Eighty-seven percent (14 of 16) of patients who died before Day 31 had a CD4 lymphocyte count < 450/muL.

CONCLUSIONS

A low CD4 count was an independent risk factor for febrile neutropenia and early death in patients receiving cytotoxic chemotherapy.

Identification of patients at risk for early death after conventional chemotherapy in solid tumours and lymphomas

1-5% of cancer patients treated with cytotoxic chemotherapy die within a month after the administration of chemotherapy. Risk factors for these early deaths (ED) are not well known. The purpose of this study was to establish a risk model for ED after chemotherapy applicable to all tumour types. The model was delineated in a series of 1051 cancer patients receiving a first course of chemotherapy in the Department of Medicine of the Centre Léon Bérard (CLB) in 1996 (CLB-1996 cohort), and then validated in a series of patients treated in the same department in 1997 (CLB-1997), in a prospective cohort of patients with aggressive non-Hodgkin's lymphoma (NHL) (CLB-NHL), and in a prospective cohort of patients with metastatic breast cancer (MBC series) receiving first-line chemotherapy. In the CLB-1996 series, 43 patients (4.1%) experienced early. In univariate analysis, age > 60, PS > 1, lymphocyte (ly) count <or= 700 microl(-1)immediately prior to chemotherapy (d1), d1-platelet count <or= 150 Gl(-1), and the type of chemotherapy were significantly correlated to the risk of early death (P<or= 0.01). Using logistic regression, PS > 1 (hazard ratio 3.9 (95% Cl 2.0-7.5)) and d1-ly count <or= 700 microl(-1) (3.1 (95% Cl 1.6-5.8)) were identified as independent risk factors for ED. The calculated probability of ED was 20% (95% Cl 10-31) in patients with both risk factors, 6% (95% Cl 4-9) for patients with only 1 risk factor, and 1.7% (95% Cl 0.9-3) for patients with none of these 2 risk factors. In the CLB-97, CLB-NHL and MBC validation series, the observed incidences of early death in patients with both risk factors were 19%, 25% and 40% respectively and did not differ significantly from those calculated in the model. In conclusion, poor performance status and lymphopenia identify a subgroup of patients at high risk for early death after chemotherapy.

Infectious complications of combination anticancer chemotherapy for urogenital cancers

We reviewed the infectious complications in 207 courses of anticancer chemotherapy to 93 patients with urogenital cancer. Thirty episodes (14.5%) of neutropenic fever containing 9 cases (4.3%) of infection were observed. Five patients (16.7%) had pyelonephritis, one (3.3%) had acute prostatitis, two (6.6%) had pneumonia and one (3.3%) had bacteraemia. Multivariate analysis revealed that the infectious complications during anticancer chemotherapy were mainly associated with urinary diversion, hydronephrosis and duration of severe neutropenia (<500/mm3). These results suggest that infectious complications should be prevented in patients with urinary diversion, hydronephrosis and severe neutropenia during anticancer chemotherapy for urogenital cancer.

Pharmacokinetics of oral fluconazole when used for prophylaxis in bone marrow transplant recipients

The pharmacokinetics of fluconazole was investigated in 20 bone marrow transplant patients following oral administration of 200 mg of this drug. Blood samples were collected from each patient at different time intervals within 48 h after the first dose, and fluconazole was measured in plasma by high-performance liquid chromatography with UV detection. Urine was collected from 14 of these patients and analyzed similarly. The plasma concentration-time data exhibited the characteristics of the one-compartment model with first-order absorption quite well. The means +/- standard deviations of half-lives for absorption and elimination, peak concentration, time to peak, mean residence time, apparent volumes of distribution, area under the curve, and apparent oral clearance observed in these patients were 2.84 +/- 1.34 h, 19.94 +/- 18.7 h, 4.45 +/- 1.86 microg/ml, 8.34 +/- 5.97 h, 39.57 +/- 20.5 h, 0.874 +/- 0.48 liter/kg, 156.0 +/- 60.6 microg x h/ml, and 0.0256 +/- 0.0138 liter/h x kg, respectively. The amount of fluconazole excreted in urine in 24 h was 67.1 +/- 83 mg, which represents 33.55% +/- 41.6% of the dose administered. Patients who developed hemorrhagic cystitis excreted significantly (P < or = 0.0094) more fluconazole in 24 h than did those who did not.

Initial empirical antibiotic therapy for neutropenic fever: analysis of the causes of death

We have reviewed the records of all patients who were included in EORTC-IATCG protocols for the empirical treatment of febrile neutropenia at the Institut Jules Bordet from 1984 to 1994. Of the 410 granulocytopenic patients, 49 died during or after febrile neutropenia. Among these, 19 died from infection, 18 from progressive neoplasia, and 12 from other causes. Fatal bacterial infection occurred in 10 patients and arose during the first 10 days; fatal fungal infection occurred in 7 patients, all of whom had a profound and protracted granulocytopenia (polymorphoneutrophil count < 100/mm3 for more than 20 days). In comparison with a previous similar study (1974-1983) our present observations shows a decrease of overall mortality during or after febrile neutropenia and an increase of gram-positive microorganisms and fungal pathogens as a cause for infectious deaths.

Recombinant human granulocyte-macrophage colony-stimulating factor in septic neutropenic pediatric cancer patients: detection of circulating hematopoietic precursor cells correlates with rapid granulocyte recovery

Cycling intensive chemotherapy currently used to treat pediatric solid tumors induces severe neutropenia. Prolonged neutropenia is a major risk factor for septic death which occurs in up to 5% of febrile or septic neutropenic episodes. We treated 18 neutropenic pediatric cancer patients (eight females, 10 males) during 30 febrile and/or septic episodes with single daily doses of E. coli-derived non-glycosylated recombinant human granulocyte-macrophage colony-stimulating factor (rh-GM-CSF, 5 micrograms per kg of body weight). The cytokine was administered for a median period of 6.5 days (2-12 days). Analysis of circulating hematopoietic progenitor cells was performed at day 1 (baseline) and day 5 of rh-GM-CSF treatment and included flow cytometric CD34 analysis as well as the methylcellulose-based clonogenic assay. Prompt hematopoietic recovery and resolution of septic problems was observed in all children. The counts of leukocytes (WBC), absolute neutrophils (ANC), and platelets (PLT) rose above 1,000/microL, 1,000/microL, and 50,000/microL within 4 days (0-9), 5.5 days (2-13), and 6 days (0-14), respectively. Faster granulocyte recovery and improved recruitment of circulating hemopoietic precursors was observed in children with detectable amounts (> 0.1%) of CD34-positive mononuclear cells prior to rh-GM-CSF treatment. We conclude that, to some extent, the efficacy of rh-GM-CSF treatment in neutropenic cancer patients is influenced by the hematopoietic recovery status on the progenitor cell level. Although they respond more slowly to the treatment, patients without circulating CD34-positive progenitor cells may gain most from growth factor therapy. Rh-GM-CSF can be safely administered to febrile and/or septic neutropenic children treated for cancer.

Intensive care and oncology

Intensive care is increasingly used in the management of cancer patients. The main reasons for admitting a cancer patient to an intensive-care unit are postoperative recovery, critical complications of the cancer disease and its treatment, the administration and monitoring of intensive anticancer treatment, and acute disease unrelated to cancer or its treatment. The present review is focused on the prognosis of critically ill cancer patients, on the description of the types of complications requiring intensive care, on specific aspects of the application of critical-care techniques in cancer patients, on ethical considerations and on ICU organization in the context of oncology.

Enhanced killing of methicillin-resistant Staphylococcus aureus in human macrophages by liposome-entrapped vancomycin and teicoplanin

The antibacterial effects of liposomal vancomycin and teicoplanin against intracellular methicillin-resistant Staphylococcus aureus (MRSA) were evaluated using a macrophage infection model. Human blood-derived monocytes were cultured for 7 days to obtain adherent macrophages. Uptake of each drug by macrophages was markedly enhanced by liposomal encapsulation. Following phagocytosis and removal of residual extracellular MRSA, the infected macrophages were exposed to clinically achievable concentrations of teicoplanin and vancomycin. The free (untrapped) and liposome-entrapped forms of each drug were used at the same concentration. The number of intracellular surviving bacteria was determined by colony counts after lysis of the macrophages at different time intervals following drug treatment. Intracellular antimicrobial effect of each drug was significantly (p < 0.001) increased by entrapment in liposomes. Also, the efficacies of the free and liposomal forms of both drugs were correspondingly comparable (p > 0.05). It is, therefore, concluded that liposomal encapsulation of vancomycin and teicoplanin results in an increased availability of the antibiotics for efficient elimination of intracellular MRSA infection.

Economic study of neutropenia induced by myelotoxic chemotherapy

This article describes the economic and social impact of neutropenia induced by myelotoxic chemotherapy in patients with cancer during the period 1 January-31 December 1991. Neutropenia is a life-threatening complication of chemotherapy in patients with cancer. The episodes of fever and infections originating from neutropenia require hospitalization of the patient until the granulocyte levels are restored. The calculation of the economic cost was based on the following parameters: length of stay in hospital, analytical tests performed on the patient, type and cost of drug therapy administered, blood transfusions performed, health assistance received, cost of isolation and absence from work. The overall economic cost of neutropenia in patients with cancer reached 329,775 pesetas ($2,893). Cost of the health-care staff was the largest budget item in relation to the total health resources estimated.

Host defense mechanism in the pathogenesis of UTI and UTI in immunocompromised patients

Defects in the immune system determine the clinical manifestations and severity of urinary tract infections (UTI) and the rates of complication but they only have an indirect role in influencing susceptibility to infection. The rates of UTI in diabetics, renal transplant, recipients, neutropenic patients, and patients with AIDS are primarily determined by the degree and duration of urinary tract manipulation and the higher perineal prevalence of potential pathogens that result from frequent hospitalization and antimicrobial use. Prompt recognition and treatment of established infections is critical to prevent life-threatening complications (e.g. bacteremia, emphysematous pyelonephritis) but routine screening for asymptomatic bacteriuria is indicated only in kidney recipients less that 3 months post-transplantation.

Ex vivo pharmacodynamic study of piperacillin alone and in combination with tazobactam, compared with ticarcillin plus clavulanic acid

Ten volunteers received piperacillin (4 g), piperacillin (4 g) plus tazobactam (0.5 g) (Tazocin), and ticarcillin (3 g) plus clavulanic acid (0.2 g) (Timentin) intravenously over 30 min in a cross-over blinded scheme. Blood samples were obtained 0.5 and 3 h after the end of infusion to measure by (high-pressure liquid chromatography) the concentration and bactericidal titers against 70 gram-negative bacilli. Serum time-kill curves were done against 35 strains to measure killing rates and area under the time-kill curve. Using the measure of serum bactericidal activity, ticarcillin-clavulanic acid and piperacillin-tazobactam were equally effective against Pseudomonas aeruginosa, Escherichia coli, Enterobacter cloacae, Serratia marcescens, and Bacteroides fragilis. Piperacillin-tazobactam was superior to ticarcillin-clavulanic acid against piperacillin-resistant Klebsiella pneumoniae (4 to 16 times) and S. marcescens (2 to 4 times). By using the area under the time-kill curve, piperacillin-tazobactam was equivalent to ticarcillin-clavulanic acid against piperacillin-susceptible strains; piperacillin-tazobactam was significantly more active than piperacillin against piperacillin-resistant strains and was more active than ticarcillin-clavulanic acid when the sample obtained 3 h after the end of infusion to volunteers was considered. Serum piperacillin concentrations (mean +/- standard error of the mean; in mg/liter) were 115 +/- 13 at 0.5 h and 7.4 +/- 1.4 at 3 h after the administration of piperacillin alone and 105.5 +/- 12.6 (0.5 h) and 7.7 +/- 1.6 after the administration of piperacillin-tazobactam. Serum tazobactam concentrations (in milligram per liter) were 13.1 +/- 1.4 at 0.5 h and 1.2 +/- 0.2 at 3 h. The piperacillin-tazobactam ratio was 8 +/- 0.3 at 0.5 h and 6.2 +/- 0.5 at 3 h. Piperacillin-tazobactam appears promising against beta-lactamase-producing gram-negative bacilli.

Recombinant granulocyte colony stimulating factor reduces the infectious complications of cytotoxic chemotherapy

The aim of this study was to determine the usefulness of recombinant human granulocyte colony stimulating factor (r-metHuG-CSF) following conventional chemotherapy for small cell lung cancer. 130 previously untreated patients were randomised to receive either r-metHuG-CSF (230 micrograms/m2) or placebo on days 4-17 following CDE (cyclophosphamide, doxorubicin and etoposide) chemotherapy. Over all cycles, 53% of 64 patients on placebo and only 26% of 65 patients on r-metHuG-CSF had at least one experience of neutropenia with fever defined as a neutrophil count less than 1.0 x 10(9)/l and a temperature > or = 38.2 degrees C (P < 0.002). It resulted in a reduction in the requirement for parenteral antibiotics from 58% in placebo patients compared with 37% in the r-metHuG-CSF group (P < 0.02), and a significant reduction in the incidence of infection-related hospitalisation. Chemotherapy doses were reduced by 15% or more at least once in 61% of the placebo group compared with 29% in the r-metHuG-CSF group (P < 0.001). 47% of the patients treated with placebo and 29% of the patients treated with r-metHuG-CSF experienced at least one cycle with a delay of 2 days or more in the administration of chemotherapy (P < 0.04). r-metHuG-CSF was well tolerated. There were no significant differences between the two groups in terms of response or survival.

Impact of the duration of infection on the activity of ceftazidime, gentamicin and ciprofloxacin in Klebsiella pneumoniae pneumonia and septicemia in leukopenic rats

An experimental Klebsiella pneumoniae pneumonia and septicemia in leukopenic rats was used to study the impact of the duration of infection on the bactericidal activity of ceftazidime, gentamicin and ciprofloxacin. It appeared that the number of bacteria persisting after a single intravenous injection progressively increased with delay of antibiotic administration up to 3 h after bacterial inoculation with each of the drugs tested. This effect was most pronounced for ciprofloxacin. An inoculum effect could not explain this decrease in bacterial killing. It was also observed that a single injection with a particular dose of each of the respective drugs did not kill all the Klebsiella pneumoniae organisms in the lung. Persisting bacteria did not represent a preexisting less susceptible subpopulation selected after antibiotic administration. In further experiments the impact of delay of the start of treatment on the efficacy of ceftazidime or ciprofloxacin after administration for a period of four days with intramuscular injections at 6 h intervals was investigated. Treatment was started at 5, 12 or 24 h after bacterial inoculation. The therapeutic efficacy of both drugs decreased with the increase of duration of infection, which may be at least in part due to the progressive number of bacteria persisting after antibiotic administration. These data underline the need to start antimicrobial treatment as soon as possible.

Home treatment of febrile neutropenia: an empirical oral antibiotic regimen

Between May 1988 and November 1989, 68 consecutive febrile courses supervening after polychemotherapy for lymphoma outpatients (median age 50 years) were treated by the combination of oral Pefloxacin/Amoxicillin Clavulanic acid. In terms of median data, neutropenia appeared on d9 [d1-d17], and lasted 5 days [2-9] with a PMN nadir observed at 0.104 x 10(9) [0-0.5 x 10(9)/l], while fever rose on d10 [1-24]. In 59 cases (87%), fever and/or focal symptoms disappeared within 3 days, after which treatment was maintained for 7 days. Nine failures were observed, of which 2 were due to abandonment of treatment, 2 to vomiting and 5 to persistence of the original symptoms. Meti Susceptible-Staphylococci were found in blood samples from 2 patients, one of whom, with grade IV lymphoma that had proved resistant to chemotherapy, died. The treatment was found to be effective and well tolerated, offering a good alternative to hospitalization during a transient chemotherapy-induced neutropenia.

Infections in the compromised child

Children receiving chemotherapy for malignant diseases show different patterns of infection depending on their underlying disease and its therapy. Granulocytopenia carries the risk of bacterial infection, and also, if prolonged, of fungal infection. Impairment of cell-mediated immunity predisposes to infections with Pneumocystis carinii and is thought to be responsible for severe primary infections with varicella and measles, as well as the severe cytomegalovirus infections seen after allogeneic bone marrow transplantation. Absence or impairment of splenic function predisposes to overwhelming septicaemia with encapsulated organisms, while defects in the normal mechanical barriers to infection provide routes for bacterial and fungal invasion. Despite the lack of physical signs of a normal inflammatory response, clinical evaluation may be critical to the localization of infection in the immunocompromised child. Blood culture and biopsy remain pivotal investigations in the achievement of a microbiological diagnosis. Empirical treatment with a combination of antibiotics has been shown in comparative studies to be effective in initial management of the febrile neutropenic patient: continuing studies are evaluating the role of monotherapy and of different antibiotic combinations, particularly in the light of changing patterns of bacterial infections. Empirical antifungal therapy has been shown to be necessary for persistent or recurrent fever, particularly as persistent fungal infection may compromise the outcome of continuing cytotoxic therapy. Continuing uncertainties over many aspects of management of the infected immunocompromised child provide scope for clinical trials in parallel with trials evaluating new anticancer regimens. The use of new diagnostic methods, the role of prophylaxis, the most appropriate empirical regimen, the evaluation of new antimicrobial agents, all require careful evaluation for efficacy and safety. Perhaps the greatest dilemma of all is how far results from trials in adults can be extrapolated to paediatric practice.

Urinary tract infection in the impaired host

In general, defects in phagocytosis and in humoral or cellular immunity do not appear to predispose to the acquisition of UTI but do influence the clinical manifestations and the severity, microbiology, and complications of infection once it is established. The incidence of UTI in immunosuppressed patients other than diabetics or renal transplant recipients is not higher than the incidence in nonimmunosuppressed individuals. The higher frequencies of infection seen in diabetics and in renal transplant recipients correlate best with the duration of bladder instrumentation rather than with glycosuria or immunosuppressive regimen. Neutropenia blunts the clinical manifestations of UTI and predisposes to bacteremia. Use of broad spectrum antibiotics results in alterations in indigenous flora, promotes urinary infections with resistant nosocomial pathogens, and predisposes to fungemia with hematogenous seeding of the urinary tract. Routine screening for detection of asymptomatic bacteriuria and prompt institution of antimicrobial therapy is indicated only in renal transplant recipients within 3 months of their surgery and not in any of the other diseases discussed.

In vitro antimicrobial activity of imipenem in combination with vancomycin or teicoplanin against Staphylococcus aureus and Staphylococcus epidermidis

The interaction between imipenem and two glycopeptides against staphylococci was examined for potential synergy. Imipenem in combination with vancomycin or teicoplanin exerted a synergistic or additive effect against a majority of Staphylococcus aureus and Staphylococcus epidermidis isolates tested by the checkerboard method. Synergistic inhibitory effects were frequently accompanied by synergistic bactericidal effects. For a proportion of bacterial isolates of both species, the demonstration of synergy by the checkerboard method was confirmed by time-kill studies using antibiotic combinations at the MICs or at achievable serum antibiotic levels. Only with a single isolate of Staphylococcus epidermidis was antagonism with either antibiotic combination recorded.

Influence of cytostatic treatment on the efficacy of erythromycin and roxithromycin in a staphylococcal infection in mice

Mice made monocytopenic with etoposide or both granulocytopenic and monocytopenic with cyclophosphamide were infected in a thigh muscle with 3 x 10(6) CFU of Staphylococcus aureus; 1 h later erythromycin or roxithromycin was administered, and 4 h after that the number of CFU per thigh was determined. In vitro as well as in vivo, the maximal effect of both antibiotics was only bacteriostatic. Monocytopenia did not diminish the efficacy of either erythromycin or roxithromycin in vivo, whereas the combination of granulocytopenia and monocytopenia markedly decreased the efficacy of both drugs: a 4-fold dose increase was necessary to obtain the same final number of CFU at the site of infection as in the controls. It is concluded that granulocytes contributed substantially to antibiotic efficacy against S. aureus in this short-term infection model.

Multicenter, randomized trial of ciprofloxacin plus azlocillin versus ceftazidime plus amikacin for empiric treatment of febrile neutropenic patients

In a multicenter, randomized clinical trial, the efficacy of ciprofloxacin plus azlocillin was compared with that of a standard regimen of ceftazidime plus amikacin for the initial empiric treatment of fever in neutropenic cancer patients. In addition, the efficacy of early conversion from intravenous therapy to orally administered ciprofloxacin was compared with that of continued ceftazidime plus amikacin. Seventy-one oncology patients with 79 episodes of fever and neutropenia were randomly assigned to receive initial empiric antibiotic therapy with either intravenously administered ciprofloxacin and azlocillin followed by orally administered ciprofloxacin (regimen 1, 25 episodes); ceftazidime and amikacin (regimen 2, 30 episodes); or ceftazidime and amikacin followed by oral ciprofloxacin (regimen 3, 24 episodes). Microbiologically documented infections were the cause of fever in 10 (40 percent), seven (23 percent), and nine (38 percent) episodes in regimens 1, 2, and 3, respectively, including six, five, and four episodes of bacteremia. Patient survival was 90 to 92 percent in each regimen; however, some modification of antimicrobial therapy occurred in 65, 44, and 41 percent of surviving patients in regimens 1, 2, and 3, respectively. The rate of clearance of initial bacteremia was 67 percent (four of six) in regimen 1, 100 percent (five of five) in regimen 2 and 50 percent (two of four) in regimen 3. Patients in regimens 1 and 3 were able to convert to orally administered ciprofloxacin in 32 (65 percent) of 49 episodes after a mean of six days of intravenous therapy. Superinfections occurred in 24, 10, and 12 percent of patients receiving regimens 1, 2, and 3, respectively, and occurred similarly for patients receiving orally administered ciprofloxacin, 12 percent (four of 32), and intravenous therapy, 17 percent (eight of 47). Parenteral ciprofloxacin was generally well tolerated. One (4 percent) of 25 patients receiving regimen 1 experienced oto- or nephrotoxicity, compared with eight (15 percent) of 54 patients receiving regimens 1, 2, and 3 (p = 0.15), including three patients who required premature termination of aminoglycoside therapy. Our data suggest that the combination of ciprofloxacin and azlocillin is an effective alternative to ceftazidime and amikacin for the initial empiric therapy of febrile neutropenic patients, is generally well tolerated, and avoids the oto- and nephrotoxicity associated with aminoglycoside use. In addition, a majority of patients could change to orally administered ciprofloxacin alone after six days of parenteral therapy.

Ex vivo study of serum bactericidal titers and killing rates of daptomycin (LY146032) combined or not combined with amikacin compared with those of vancomycin

Twelve volunteers, in two groups of six, received daptomycin at a dose of 1 or 2 mg/kg. In addition, they received in a randomly allocated order amikacin (500 mg), daptomycin-amikacin, and vancomycin (500 mg). Thirty-five clinical isolates, including Staphylococcus aureus, S. epidermidis, Corynebacterium sp. group JK, and Enterococcus faecalis, were tested in vitro for the measure of the serum bactericidal titers and killing rates. The mean peak concentrations of daptomycin in serum 1 h after the administration of 1 and 2 mg/kg were 11 and 20 micrograms/ml, respectively. At 24 h after the administration of 2 mg/kg, the mean level in serum was 1.9 micrograms/ml, which is higher than the MICs for susceptible pathogens. Daptomycin and amikacin provided identical concentrations in serum whether given alone or in combination. Among the six regimens tested, those including daptomycin provided the highest and the most prolonged serum bactericidal titers against S. aureus, S. epidermidis, and E. faecalis. The killing rates measured by the killing curves were correlated with the concentration/MIC and concentration/MBC ratios of daptomycin for all strains tested. Significant killing occurred once the concentration of daptomycin in the serum 4- to 6-fold the MIC or 1- to 1.2-fold the MBC. The combination of daptomycin and amikacin had no effect on either the serum bactericidal titers or the rates of killing. Only vancomycin provided significant killing of the strains of Corynebacterium sp. group JK.

Empiric antifungal therapy in febrile granulocytopenic patients. EORTC International Antimicrobial Therapy Cooperative Group

PURPOSE

The optimal management of fever in granulocytopenic patients remains controversial. Invasive fungal infections are common and life-threatening but are difficult to diagnose early. In this randomized study, we investigated the potential value of empiric administration of amphotericin B (versus no empiric antifungal therapy) in 132 patients remaining febrile and granulocytopenic despite broad-spectrum antibiotic therapy for four days.

PATIENTS AND METHODS

The patients were divided into two groups: 68 who were randomly assigned to receive empiric amphotericin B, and 64 who were randomly assigned to continue only the protocol antibiotics that they were already receiving. Amphotericin B was administered intravenously as follows: every other day at a dose of 1.2 mg/kg body weight or daily at a dose of 0.6 mg/kg body weight. Clinical response was evaluated as success or failure, depending upon the febrile course after randomization.

RESULTS

Based on the evolution of fever, the response rate was 69% in the group of patients receiving empiric amphotericin B and 53% for the other group (p = 0.09). There were six documented (four severe) fungal infections in 64 patients randomized not to receive the antifungal therapy as compared to only one fungemia among 68 patients treated empirically with amphotericin B (p = 0.1). No deaths due to fungal infection occurred among the patients receiving empiric amphotericin B compared to four in the other group (p = 0.05). However, this study did not demonstrate a difference in survival between the two groups of patients (with or without empiric amphotericin B). The benefit of empiric administration of amphotericin B was primarily observed in specific subgroups of patients, such as those who did not receive any antifungal prophylaxis (78% versus 45%, p = 0.04), those who were severely granulocytopenic (69% versus 46%, p = 0.06), febrile patients with a clinically documented infection (75% versus 41%, p = 0.03), and patients older than 15 years of age (67% versus 47%, p = 0.06).

CONCLUSION

These data suggest a benefit for early amphotericin B treatment in granulocytopenic patients with continued fever despite antibiotic therapy.

Empiric antimicrobial therapy for febrile granulocytopenic cancer patients. Lessons from four EORTC trials

The experience from four EORTC trials on antimicrobial therapy for febrile granulocytopenic cancer patients (GCP) is reviewed. A general conclusion from these trials is that studies of the management of infection in GCP should include sufficient numbers of eligible patients to allow for evaluation of bacteremic patients at highest risk of death. The need for large collaborative studies stems directly from these considerations.

Influence of dose frequency on the therapeutic efficacies of ciprofloxacin and ceftazidime in experimental Klebsiella pneumoniae pneumonia and septicemia in relation to their bactericidal activities in vitro

The antibacterial activities of ciprofloxacin versus ceftazidime against Klebsiella pneumoniae in vitro and in vivo were compared. Although there was only a minor difference in MBC values between both drugs ciprofloxacin demonstrated a high and dose-dependent bacterial killing rate in vitro and in lungs of leukopenic rats in contrast to the more time-dependent bactericidal activity of ceftazidime. After treatment of a K.pneumoniae pneumonia and septicemia the efficacy of ciprofloxacin was only slightly influenced by the mode of administration, either at 6-h intervals or continuously, whereas ceftazidime was far more effective after continuous administration. This resulted in a superior efficacy of ciprofloxacin after intermittent treatment as compared to ceftazidime, whereas ceftazidime was more effective after continuous administration as compared to ciprofloxacin. Also ciprofloxacin proved to be bactericidal against bacteria that were not actively growing, both in vitro and in vivo, whereas ceftazidime was not.

Comparative activities of ciprofloxacin and ceftazidime against Klebsiella pneumoniae in vitro and in experimental pneumonia in leukopenic rats

The antibacterial activities of ciprofloxacin and ceftazidime against Klebsiella pneumoniae in vitro and in vivo were compared. Although there was only a minor difference between the MBCs of both drugs, the bacterial killing rate of ciprofloxacin in vitro was very fast in comparison with that of ceftazidime. Similarly, the intravenous administration of ciprofloxacin at 1 h after bacterial inoculation resulted in effective bacterial killing in the lungs of leukopenic rats. This killing was dose dependent, in contrast to the dose-independent bactericidal effect of ceftazidime. The high antibacterial activity of ciprofloxacin in the lungs as compared with that of ceftazidime was also reflected in its therapeutic efficacy in K. pneumoniae pneumonia and septicemia in leukopenic rats when these infections were treated at 6-h intervals over 4 days, starting at 5 h after bacterial inoculation. Concentrations of ciprofloxacin and ceftazidime in lung tissue were not significantly different. Regarding the antibacterial activity of both drugs against K. pneumoniae in relation to the bacterial growth rate in vitro and in the lungs of leukopenic rats, ciprofloxacin killed K. pneumoniae organisms that were not actively growing, whereas ceftazidime did not. In addition, it was demonstrated that when the intravenous administration of antibiotic was delayed from 1 h up to 24 h after bacterial inoculation, ceftazidime lost its antibacterial activity in the lungs and blood of leukopenic rats, whereas ciprofloxacin was still very effective. These data suggest that the capacity of an antibiotic to kill bacteria at a slow growth rate may be relevant for its therapeutic effect in established infections, in which slowly growing bacteria form a substantial part of the total bacterial population.

Serum bactericidal activity and postantibiotic effect in serum of patients with urinary tract infection receiving high-dose amikacin

Ten patients received a 30-min infusion of amikacin (30 mg/kg) on day 1 and 15 mg/kg on day 2. Mean serum creatinine was 1.1 +/- 0.3 (standard deviation) mg/dl before and 1.0 +/- 0.3 mg/dl 3 days after the second infusion. Mean serum amikacin concentrations before, at the end of infusion, and 1, 6, 12, and 24 h after 30 and 15 mg/kg were 0, 157, 79, 31, 16, 5, 5, 85, 51, 19, 12, and 5 mg/liter, respectively. Five strains each of Staphylococcus aureus, Staphylococcus epidermidis susceptible and resistant to oxacillin, Streptococcus (Enterococcus) faecalis, corynebacterium sp. strain JK, Listeria monocytogenes, Mycobacterium fortuitum (three strains), Klebsiella pneumoniae, Serratia marcescens, Acinetobacter calcoaceticus, and Pseudomonas aeruginosa were tested. Serum bactericidal activities (SBAs) were greater than or equal to 1:8 in greater than or equal to 80% of the sera 1 and 6 h after 30 mg/kg and in greater than or equal to 60% of the sera 1 and 6 h after 15 mg/kg against Staphylococcus aureus and Staphylococcus epidermidis susceptible to oxacillin, A. calcoaceticus, and K. pneumoniae. L. monocytogenes, Serratia marcescens, and P. aeruginosa had lower SBAs. Very low or no activity was observed against oxacillin-resistant staphylococci and Streptococcus faecalis. The study of the killing rate in serum confirmed these results. Postantibiotic effect was studied by incubating a strain from each species in serum samples obtained 1 and 6 h after both regimens for 0.5, 1, or 2 h. The duration of postantibiotic effect depended on the duration of contact and the concentration of amikacin for the following organisms: oxacillin-susceptible staphylococci, L. monocytogenes, P. aeruginosa, A. calcoaceticus, K. pneumoniae, and Serratia marcescens. M. fortuitum was killed after 30 min of contact. No postantibiotic effect was observed with Streptococcus faecalis, Corynebacterium sp. strain JK, or oxacillin-resistant staphylococci. Amikacin at 30 mg/kg provided high levels and SBAs against susceptible pathogens. Prolonged postantibiotic effects were observed. No signs of nephrotoxicity occurred.

Bactericidal activity and killing rate of serum in volunteers receiving teicoplanin alone or in combination with oral or intravenous rifampin

A total of 10 volunteers, in two groups of 5 each, received the following on separate days: group 1,200 mg of teicoplanin intravenously (i.v.), 600 mg of rifampin orally, or teicoplanin-rifampin; group 2,400 mg of teicoplanin i.v., 300 mg of rifampin i.v. in 60 min, or teicoplanin-rifampin. Blood samples were obtained before, at the end, and at 1 and 6 h after the administration of the antibiotics. Bactericidal activity in serum (SBA) was measured in microtiter plates against 20 clinical isolates (five strains each) of oxacillin-susceptible and-resistant Staphylococcus aureus and Staphylococcus epidermidis. The endpoint of the SBA corresponded to 99.9% killing. Killing rates were measured in serum obtained at 1 and 6 h. The concentrations of each antibiotic were measured by bioassay. The antibiotic concentrations in serum obtained at the peak and at 1 and 6 h after the end of administration were as follows: group 1, teicoplanin, 26, 15.6, and 8.4 mg/liter; rifampin, not determined, 8.3, and 3.8 mg/liter; group 2, teicoplanin, 66, 29.4, and 11.5 mg/liter; rifampin, 14.8, 3.8, and 1.2 mg/liter. Higher median SBAs were obtained after treatment with rifampin than after that with teicoplanin. No interaction was observed between rifampin and teicoplanin. This was confirmed by determination of the killing rate in serum. Teicoplanin killed more slowly than rifampin. The combination had the same killing rate as rifampin alone. Rifampin neither improved nor antagonized the bactericidal activity of teicoplanin, as determined by the SBAs or the rate of killing.

Bactericidal activity and killing rate of serum in volunteers receiving ciprofloxacin alone or in combination with vancomycin

Ten healthy volunteers received the following regimen on different days: vancomycin, 500 mg intravenously; ciprofloxacin, 200 mg intravenously; vancomycin plus ciprofloxacin. Concentrations in serum measured microbiologically at the end of infusion and 1 and 6 h after the end of infusion were, respectively (mean [standard deviation] in milligrams per liter): 32.3 (5.5), 14.2 (2.6), and 4 (0.9) for vancomycin and 3.12 (0.86), 0.78 (0.18), and 0.19 (0.05) for ciprofloxacin. Vancomycin concentration was not affected by the simultaneous administration of ciprofloxacin. The serum bacteriostatic and bactericidal (SBA) activities were measured 1 and 6 h after the end of infusion against five strains each of Staphylococcus aureus susceptible and resistant to oxacillin, Staphylococcus epidermidis susceptible and resistant to oxacillin, Corynebacterium strain JK, and Listeria monocytogenes and three strains of Mycobacterum fortuitum. Ciprofloxacin alone provided low SBAs against the tested strains even 1 h after administration. Vancomycin provided adequate SBAs against staphylococci and Corynebacterium strain JK 1 h after administration. None of the regimens tested showed adequate bactericidal activity against L. monocytogenes and M. fortuitum. The combination of vancomycin with ciprofloxacin was indifferent. This was confirmed by studying the rate of killing in serum. Vancomycin plus ciprofloxacin appeared to be promising for the empiric treatment of infection in immunocompromised patients.

Continuous versus intermittent administration of ceftazidime in experimental Klebsiella pneumoniae pneumonia in normal and leukopenic rats

Experimental Klebsiella pneumoniae pneumonia was used to study the influence of cyclophosphamide-induced leukopenia on the relative therapeutic efficacy of continuous and intermittent (6-h intervals) administration of ceftazidime. The antimicrobial response was evaluated with respect to the calculated daily dose that protected 50% of the animals from death (PD50) until 16 days after the termination of a 4-day treatment. When ceftazidime was administered intermittently to leukopenic rats, the PD50 was 24.37 mg/kg per day, 70 times (P less than 0.001) the PD50 of 0.35 mg/kg per day for normal rats. Continuous administration of ceftazidime to leukopenic rats resulted in a PD50 of 1.52 mg/kg per day, four times (P less than 0.001) the PD50 of 0.36 mg/kg per day for normal rats. Continuous administration of ceftazidime in daily doses that protected 100% of normal and leukopenic rats from death resulted in serum levels of 0.06 and 0.38 micrograms/ml, respectively, whereas the MIC for the infecting K. pneumoniae strain was 0.2 micrograms of ceftazidime per ml. The effect of the duration of ceftazidime treatment by continuous infusion on the therapeutic efficacy in relation to the persistence of leukopenia was then investigated in leukopenic rats. The administration of 3.75 mg of ceftazidime/kg per day for 4 days protected all leukopenic rats from death, provided the circulating leukocytes returned at the end of antibiotic treatment. When leukopenia persisted for 8 days this ceftazidime treatment schedule resulted in the mortality of rats (P less than 0.05). However, when ceftazidime treatment was continued for 8 days, until the return of the leukocytes, there was no significant mortality (P greater than 0.05).

Serum bactericidal activity and killing rate for volunteers receiving imipenem, imipenem plus amikacin, and ceftazidime plus amikacin against Pseudomonas aeruginosa

Serum bactericidal activity against 20 strains of Pseudomonas aeruginosa was studied in 10 volunteers after administration of imipenem (25 mg/kg), imipenem (25 mg/kg) plus amikacin (7.5 mg/kg), and ceftazidime (25 mg/kg) plus amikacin (7.5 mg/kg). Eight strains were susceptible and 12 were resistant to ticarcillin. Serum levels were measured microbiologically after 30 and 60 min and were, respectively, 97 and 46 micrograms/ml for imipenem given alone and 79 and 45 micrograms/ml for imipenem given with amikacin. Despite the very large dose of imipenem used, imipenem and imipenem plus amikacin appeared slightly less active than ceftazidime plus amikacin (P less than or equal to 0.1; Wilcoxon matched-pairs test), with respective median titers at 30 min of 1:128, 1:128, and 1:256 against ticarcillin-susceptible strains and 1:32, 1:32, and 1:64 against ticarcillin-resistant strains; however, more than 90% of the serum determinations, regardless of the regimen, had a serum bactericidal activity greater than or equal to 1:8. Amikacin significantly increased the rate of killing in serum of P. aeruginosa by imipenem. Imipenem plus amikacin appeared as effective as ceftazidime plus amikacin in reducing the viable counts of P. aeruginosa after 24 h of incubation.

BRL-36650: in vitro studies and assessment of serum bactericidal activity after single-dose administration in volunteers

Ten healthy volunteers received 1 g of BRL-36650, a new formamido-penicillin derivative, given by intravenous infusion over 15 min. Levels in serum were measured microbiologically 30, 60, and 120 min after the start of the 15-min infusion and were (mean +/- standard deviation) 102.7 +/- 28.4, 59.7 +/- 11.5, and 9.6 +/- 1.9 mg/liter, respectively. A total of 10 strains each of Escherichia coli, Klebsiella pneumoniae, Serratia spp., and Enterobacter spp. and 14 strains of Pseudomonas aeruginosa were selected according to their susceptibility or resistance to piperacillin for the study of serum bactericidal activity (SBA). The MICs and MBCs of these strains were influenced by the choice of medium. Median SBA against E. coli and K. pneumoniae were greater than or equal to 1:2,048 and 1:512, respectively. The SBA against piperacillin-susceptible Serratia spp. (1:256), Enterobacter spp. (1:128), and P. aeruginosa (1:32) were significantly higher than against piperacillin-resistant strains (1:32, 1:8, and 1:4, respectively). Killing curves confirmed the high bactericidal activities obtained against the majority of strains. In the case of one Enterobacter sp. and one P. aeruginosa isolate with an MBC greater than or equal to 32, the absence of killing was noted.

Bactericidal activity and killing rate of serum from volunteers receiving pefloxacin alone or in combination with amikacin

Serum bactericidal activities (SBAs) were studied after intravenous administration of pefloxacin (8 mg/kg) and amikacin (7.5 mg/kg) alone or in combination to 15 human volunteers. About 10 strains each of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus were tested. The serum levels of pefloxacin were measured microbiologically by using E. coli KP 1976-712 as the test organism at 0, 30, 60, 120, and 720 min after infusion; at 0, 30, 60, and 720 min these levels were 7 +/- 1.4, 5 +/- 0.8, 4.5 +/- 0.7, and 2.1 +/- 0.6 mg/liter (mean +/- standard deviation), respectively, with a terminal half-life of 10 h. The serum levels of pefloxacin in the presence of amikacin were measured similarly; 1% sodium polyanethol sulfonate was added to the agar to inactivate amikacin. Treatment with pefloxacin alone resulted in high SBAs against E. coli, K. pneumoniae strains susceptible to cephalothin, and Staphylococcus aureus at the peak concentration; 81 to 100% of the sera had SBAs of greater than or equal to 1:8. However, treatment with pefloxacin alone resulted in low SBAs against K. pneumoniae strains resistant to cephalothin and P. aeruginosa; only 34% of the sera had SBAs of greater than or equal to 1:8. At trough concentrations the percentages of sera with SBAs greater than or equal to 1:8 were 75 to 83% (E. coli), 9 to 27% (K. pneumoniae), 0% (P. aeruginosa), and 10% (S. aureus). The combination of pefloxacin plus amikacin was most often additive; the peak activity was due to amikacin, and the trough activity was due to pefloxacin. Occasionally antagonism occurred with P. aeruginosa, K. pneumoniae, and S. aureus strains. These observations were confirmed by the killing curves in pooled serum obtained at peak and trough levels. Regrowth was observed for seven strains of P. aeruginosa treated with pefloxacin alone; amikacin seemed to prevent this phenomenon.

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.