Use Of Fluoroquinolone Prophylaxis Research Articles

Fluoroquinolone Prophylaxis in Children With Cancer: A Pro/Con Discussion.

There are conflicting recommendations on whether to use or not to use fluoroquinolone prophylaxis in pediatric oncology patients. An international pediatric clinical practice guideline (CPG) recommends administering levofloxacin prophylaxis in patients with acute myeloblastic leukemia and relapsed acute lymphoblastic leukemia receiving intensive chemotherapy as this practice has been found to reduce episodes of fever and bacteremia. A separate European CPG does not recommend levofloxacin prophylaxis because of concerns for adverse effects, including potentiation of fluoroquinolone resistance and possible increased resistance to other classes of antibiotics. The nuance of the decision to give or not give prophylaxis is discussed in the context of published evidence defining the risks and benefits of levofloxacin prophylaxis for pediatric leukemia patients at high risk for bacterial infection. Knowledge gaps are also identified to guide further investigations to optimize the use of fluoroquinolone prophylaxis in pediatric patients receiving chemotherapy for cancer or undergoing a hematopoietic cell transplantation.

Fluoroquinolone prophylaxis in patients with neutropenia at high risk of serious infections: Exploring pros and cons.

The use of fluoroquinolones to prevent infections in neutropenic patients with cancer or undergoing hematopoietic stem cell transplantation (HSCT) is a controversial issue, with international guidelines providing conflicting recommendations. Although potential benefits are clear, concerns revolve around efficacy, potential harms, and antimicrobial resistance (AMR) implications. Fluoroquinolone prophylaxis reduces neutropenic fever (NF) bloodstream infections and other serious bacterial infections, based on evidence from systematic reviews, randomized controlled trials, and observational studies in adults and children. Fluoroquinolone prophylaxis may also reduce infection-related morbidity and healthcare costs; however, evidence is conflicting. Adverse effects of fluoroquinolones are well recognized in the general population; however, studies in the cancer cohort where it is used for a defined period of neutropenia have not reflected this. The largest concern for routine use of fluoroquinolone prophylaxis remains AMR, as many, but not all, observational studies have found that fluoroquinolone prophylaxis might increase the risk of AMR, and some studies have suggested negative impacts on patient outcomes as a result. The debate surrounding fluoroquinolone prophylaxis calls for individualized risk assessment based on patient characteristics and local AMR patterns, and prophylaxis should be restricted to patients at the highest risk of serious infection during the highest risk periods to ensure that the risk-benefit analysis is in favor of individual and community benefit. More research is needed to address important unanswered questions about fluoroquinolone prophylaxis in neutropenic patients with cancer or receiving HSCT.

Bloodstream infections due to Gram-negative bacteria in patients with hematologic malignancies: updated epidemiology and risk factors for multidrug-resistant strains in an Italian perspective survey

Bloodstream infections (BSI) caused by Gram-negative bacteria (GNB) in patients with hematological malignancies (HM) have been associated with high mortality rates, particularly with infections caused by antibiotic-resistant strains.A multicenter cohort study including all consecutive episodes of GNB BSI in HM patients was conducted to update the epidemiology and antibiotic resistance patterns (compared to our previous survey conducted between 2009 and 2012) and investigate risk factors for GNB BSI due to multidrug-resistant (MDR) isolates.A total of 834 GNB were recovered in 811 BSI episodes from January 2016 to December 2018. Compared to the previous survey, there was a significant reduction in use of fluoroquinolone prophylaxis and a significant recovery in susceptibility rates to ciprofloxacin among Pseudomonas aeruginosa, Escherichia coli and Enterobacter cloacae isolates. In addition, there was a shift to a significantly increased susceptibility of P. aeruginosa isolates to ceftazidime, meropenem, and gentamicin. A total of 256/834 (30.7%) isolates were MDR. In multivariable analysis, MDR bacteria culture-positive surveillance rectal swabs, previous therapy with aminoglycosides and carbapenems, fluoroquinolone prophylaxis, and time at risk were independently associated with MDR GNB BSI.In conclusion, despite the persistence of a high prevalence of MDR GNB, there was a shift to a reduced use of fluoroquinolone prophylaxis and increased rates of susceptibility to fluoroquinolones in almost all isolates and to almost all antibiotics tested among P. aeruginosa isolates, compared to our previous survey. Fluoroquinolone prophylaxis and previous rectal colonization by MDR bacteria were independent risk factors for MDR GNB BSI in the present study.

Outbreak of Pseudomonas aeruginosa Bacteremia Infections among Stem-Cell Transplant Patients Related to Change in Prophylaxis

Background:Pseudomonas aeruginosa outbreaks can originate from various sources and can cause severe complications in posttransplant patients. Antibiotic prophylaxis can decrease posttransplant infections; however, consideration must be given to P. aeruginosa coverage as we outline an outbreak among the stem-cell transplant (SCT) population. Methods: A multidisciplinary outbreak investigation was conducted to evaluate sources of contamination and changes in clinical processes. Positive blood cultures from SCT patients and environmental isolates were analyzed using whole-genome sequencing (WGS). Incidence density rates for P. aeruginosa blood cultures from January 2019 through October 2020 were calculated per 10,000 patient days and stratified by unit, specimen, and transplant type. Statistical analysis was calculated with significance at p < 0.05. Results: A cluster of 8 SCT patients was identified between May and September 2020. Moreover, 10 environmental samples were positive for P. aeruginosa including drains, water sources prior to the point-of-use (POU) filter and blood-bank thaw machines. Phylogenetic analysis revealed 1 cluster of 2 patients who shared the same room, 5 patients with unique P. aeruginosa isolates, and 2 separate clusters of environmental isolates with relatedness only to each other. Review of clinical processes showed a change from fluoroquinolone prophylaxis to cephalosporin in the spring of 2020. Also, 5 P. aeruginosa bacteremia infections occurred prior to June (11.78 cases per 10,000 patient days). During the period of cephalosporin use, 8 infections were identified (58.27 cases per 10,000 patient days) (P = .006). Following the restart of fluoroquinolone, zero infections have occurred to date, as of January 28, 2021. Conclusions: Discontinuation of fluoroquinolone prophylaxis was associated with P. aeruginosa bacteremia infections in SCT patients. Use of fluoroquinolone prophylaxis in SCT patients is protective from P. aeruginosa bacteremia infections. There have been no further infections in the following 3 months after the change back to the use of fluoroquinolone. Additionally, WGS showed that most patient isolates did not have a common source, suggesting that P. aeruginosa gastrointestinal colonization may play a role in seeding these bacteremia infections.Funding: NoDisclosures: None

Quality of inpatient antimicrobial use in hematology and oncology patients.

To compare antimicrobial prescribing practices in Australian hematology and oncology patients to noncancer acute inpatients and to identify targets for stewardship interventions. Retrospective comparative analysis of a national prospectively collected database. Using data from the 2014-2018 annual Australian point-prevalence surveys of antimicrobial prescribing in hospitalized patients (ie, Hospital National Antimicrobial Prescribing Survey called Hospital NAPS), the most frequently used antimicrobials, their appropriateness, and guideline concordance were compared among hematology/bone marrow transplant (hemBMT), oncology, and noncancer inpatients in the setting of treatment of neutropenic fever and antibacterial and antifungal prophylaxis. In 454 facilities, 94,226 antibiotic prescriptions for 62,607 adult inpatients (2,230 hemBMT, 1,824 oncology, and 58,553 noncancer) were analyzed. Appropriateness was high for neutropenic fever management across groups (83.4%-90.4%); however, hemBMT patients had high rates of carbapenem use (111 of 746 prescriptions, 14.9%), and 20.2% of these prescriptions were deemed inappropriate. Logistic regression demonstrated that hemBMT patients were more likely to receive appropriate antifungal prophylaxis compared to oncology and noncancer patients (adjusted OR, 5.3; P < .001 for hemBMT compared to noncancer patients). Oncology had a low rate of antifungal prophylaxis guideline compliance (67.2%), and incorrect dosage and frequency were key factors. Compared to oncology patients, hemBMT patients were more likely to receive appropriate nonsurgical antibacterial prophylaxis (aOR, 8.4; 95% CI, 5.3-13.3; P < .001). HemBMT patients were also more likely to receive appropriate nonsurgical antibacterial prophylaxis compared to noncancer patients (OR, 3.1; 95% CI, 1.9-5.0; P < .001). However, in the Australian context, the hemBMT group had higher than expected use of fluoroquinolone prophylaxis (66 of 831 prescriptions, 8%). This study demonstrates why separate analysis of hemBMT and oncology populations is necessary to identify specific opportunities for quality improvement in each patient group.

Impact of Primary Antibacterial Prophylaxis on Neutropenic Fever, Infections, and Antimicrobial Resistance in Newly Diagnosed AML Patients

Introduction: Patients with acute myeloid leukemia (AML) have a high risk of infection during induction therapy due to the severity and duration of chemotherapy-induced neutropenia. As a result, the American Society of Clinical Oncology and the Infectious Diseases Society of America recommend fluoroquinolone prophylaxis in this patient population during induction therapy. The initial studies supporting the current guidelines showed decreased risk of neutropenic fever and systemic bacterial infections with fluoroquinolone prophylaxis but no mortality benefit. Notably, the use of fluoroquinolone prophylaxis is associated with colonization and infection with multidrug-resistant organisms, and these studies were conducted in areas with low rates of fluoroquinolone resistance. At our institution, the rates of fluoroquinolone resistance among the 3 most common causes of Gram-negative bacteremia (Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa) ranged from 17% to 45% among inpatients during the study period. We aimed to evaluate the efficacy of fluoroquinolone prophylaxis in a population with high rates of fluoroquinolone resistance. Methods: We performed a retrospective chart review of newly diagnosed adult AML patients who received induction therapy at Mount Sinai Hospital in New York, NY, from 6/1/2012 to 12/31/2016. Patients were excluded if they received antibiotics for &gt;4 days in the 1 week prior to induction therapy, developed a clinically or microbiologically documented infection (CDI or MDI) in the 2 weeks prior to induction therapy, did not develop neutropenia (defined as neutrophil count &lt; 500 cells/μL), or developed fever on the first day of neutropenia. Patients were followed for 6 months after initiation of induction therapy. The primary outcome was development of neutropenic fever. The secondary outcomes were development of infections, infection with multidrug-resistant organisms, and mortality. We used a time-varying (Simon-Makuch) statistical approach to categorize patients into the prophylaxis group or no prophylaxis group. We adjusted each outcome for gender, age at diagnosis, type of AML (de novo vs. secondary), and type of induction therapy. Results: Of the 95 included patients, 77 received primary fluoroquinolone prophylaxis and 18 did not receive any bacterial prophylaxis. There was no difference in median age, gender, or type of induction therapy between the prophylaxis and no prophylaxis groups (Table 1). Although more patients in the prophylaxis group had de novo disease (61% vs. 33%, p=0.003) and received inpatient induction therapy (88% vs. 56%, p=0.003), there was no difference in duration of neutropenia (28 vs. 23 days, p=0.349). There was no statistically significant difference in risk of febrile neutropenia (multivariable HR 1.41 [0.70 - 2.84], p=0.339) or mortality (multivariable HR 0.72 [0.35-1.48], p=0.371), with or without adjustment for baseline confounders. During the induction period and 6-month follow up, there was no difference in rates of bacteremia, invasive fungal infections, Clostridium difficile infections, CDI, MDI, or infection with fluoroquinolone-resistant or multidrug-resistant organisms (Table 2). Conclusions: Use of primary fluoroquinolone prophylaxis during AML induction therapy did not impact rates of neutropenic fever, infections, and antimicrobial resistance during induction and 6 month follow up. Similar to prior studies, fluoroquinolone prophylaxis also did not improve overall survival. This suggests that primary fluoroquinolone prophylaxis in this high-risk population provides neither benefit nor harm. Larger randomized controlled clinical trials are needed to further investigate this topic. Disclosures Jacobs: Ansun Biopharma, Inc.: Consultancy.

1018. Prevalence of Bacteremia/Fungemia and Pneumonia in Remission Induction Chemotherapy for Adult Acute Myeloid Leukemia From 1987 to 2005: Japan Adult Leukemia Study Group (JALSG)

BackgroundRemission induction (RI) chemotherapy for acute myeloid leukemia (AML) is one of the most intensive chemotherapy available. Antibiotic prophylaxis and prompt treatment for infectious complications during RI chemotherapy play a major role in supportive care.MethodsWe retrospectively analyzed the infectious complications associated with RI chemotherapy listed in the Japan Adult Leukemia Study Group AML201 protocol, a nationwide study of de novo AMLs, conducted between 2001 and 2005 in Japan. Of the 1,057 cases initially included in the AML201 study, 980 cases with data on infectious complications during RI chemotherapy were analyzed. The incidences of infectious complications and the causative pathogens were compared with previous studies [(period A) 1987–1991, 577 cases; (B) 1992–1995, 669 cases; (C) 1995–1997, 531 cases; (D) 1997–2001, 808 cases; (E) 2001–2005, 980 cases].ResultsIn study period E, the causative pathogens of bacteremia/fungemia were Staphylococcus epidermidis (20.9%), S. aureus (11.6%), Streptococcus sp. (14.0%), and other Gram-positive bacteria (18.6%); P. aeruginosa (12.8%) and other Gram-negative bacteria (10.5%); and fungi (9.3%). Pathogens causing pulmonary infections were Aspergillus sp.(15.8%), P. aeruginosa (7.9%), and other Gram-negative bacteria (6.9%) and Gram-positive bacteria (3.0%). Pulmonary aspergillosis was diagnosed mainly using serological test. The prevalence of bacteremia/fungemia was reported in 11.8%, 9.4%, 8.7%, 9.2%, and 8.3% of cases and pulmonary infections were reported in 24.6%, 16.9%, 13.9%, 12.9%, and 10.3% of cases in the study periods A, B, C, D, and E, respectively. The incidence of Gram-negative bacteremia was significantly lower in period E compared with the periods A, B, and C (2.0% vs. 4.9%, 3.7%, and 3.4%, respectively).ConclusionThe prevalence of Gram-positive bacteremia and pulmonary aspergillosis was higher in period E than in the periods A–D. This trend was possibly due to the wide use of fluoroquinolone prophylaxis in neutropenic patients and high performance of the serological test for aspergillosis. Sufficient monitoring for Gram-positive bacterial infection and mold infection is therefore essential during RI chemotherapy for AML.Disclosures All authors: No reported disclosures.

Ciprofloxacin prophylaxis delays initiation of broad-spectrum antibiotic therapy and reduces the overall use of antimicrobial agents during induction therapy for acute leukaemia: A single-centre study

Background Due to an outbreak of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae, the routine use of fluoroquinolone prophylaxis was questioned. As a result, this study was conducted with the aim to evaluate the impact of ciprofloxacin-prophylaxis on the use of broad-spectrum antibioctics and anti-mycotics. Methods A cohort of 139 consecutive patients with acute leukaemia treated with remission-inducing induction chemotherapy between 2004–2012 at the Department of Haematology in Uppsala University Hospital was analysed. Results Fifty-three patients (38%) received broad-spectrum antibiotics at the initiation of chemotherapy and were not eligible for prophylaxis. Of the remaining patients, the initiation of broad-spectrum antibiotics was delayed by 3 days in those receiving ciprofloxacin prophylaxis (n = 47) compared with those receiving no prophylaxis (n = 39). The median duration of systemic antibiotic treatment was 6 days shorter in patients receiving ciprofloxacin prophylaxis (12 vs 18 days; p = 0.0005) and the cumulative (total) median days on systemic antibiotic treatment was shortened by 8 days (15 vs 23 days, p = 0.0008). Piperacillin/tazobactam (p = 0.02), carbapenems (p = 0.05) and empiric broad-spectrum antifungals (p < 0.01) were used significantly less often when ciprofloxacin prophylaxis was given. Conclusions Ciprofloxacin prophylaxis delayed empiric therapy by 3 days and reduced overall antibiotic use in this study. These benefits must be evaluated vs the risks of development of resistant bacterial strains, making fluoroquinolone prophylaxis an open question for debate.

Garenoxacin Prophylaxis for Febrile Neutropenia after Chemotherapy in Hematological Malignancies

Background: Febrile neutropenia is one of the most serious adverse events in patients with hematological malignancies and chemotherapy. The routine use of fluoroquinolone prophylaxis in patients with hematological malignancies is controversial. Therefore, we prospectively evaluated the efficacy and safety of prophylactic use of garenoxacin for febrile neutropenia. Patients and Methods: Consecutive adult patients with hematological malignancies who were at risk for chemotherapy-induced neutropenia lasting more than seven days were eligible for present study. They received oral garenoxacin (400 mg daily) from the neutrophil count decreased to less than 1000/μl and continued until the neutropenia had resolved. The primary endpoint was incidence of febrile neutropenia, and the secondary endpoints were the type and incidence of adverse events. Results: We enrolled 46 consecutive patients (median age, 59 years). The underlying diseases comprised acute myeloid leukemia (n = 17), acute lymphoblastic leukemia (n = 3), malignant lymphoma (n = 23), and multiple myeloma (n = 3). There were 23 febrile neutropenia episodes and 2 episodes of bacteremia. There were no grade 3 or 4 adverse events; however serum creatinine levels were significantly elevated after garenoxacin administration. The overall prophylactic efficacy of garenoxacin was 50%, and there were no infection-related deaths. Conclusions: Prophylactic use of garenoxacin is effective and safe in patients with hematological malignancies. (Clinical trial registration number: UMIN000004979).

New Insight on Epidemiology and Management of Bacterial Bloodstream Infection in Patients with Hematological Malignancies.

Bloodstream infections (BSI) are a significant cause of morbidity and mortality in onco-hematologic patients. The Gram-negative bacteria were the main responsible for the febrile neutropenia in the sixties; their impact declined due to the use of fluoroquinolone prophylaxis. This situation was followed by the gradual emergence of Gram-positive bacteria also following the increased use of intravascular devices and the introduction of new chemotherapeutic strategies. In the last decade, the Gram-negative etiology is raising again because of the emergence of resistant strains that make questionable the usefulness of current strategies for prophylaxis and empirical treatment. Gram-negative BSI attributable mortality is relevant, and the appropriate empirical treatment significantly improves the prognosis; on the other hand the adequate delayed treatment of Gram-positive BSI does not seem to have a high impact on survival. The clinician has to be aware of the epidemiology of his institution and colonizations of his patients to choose the most appropriate empiric therapy. In a setting of high endemicity of multidrug-resistant infections also the choice of targeted therapy can be a challenge, often requiring strategies based on off-label prescriptions and low grade evidence.In this review, we summarize the current evidence for the best targeted therapies for difficult to treat bacteria BSIs and future perspectives in this topic. We also provide a flow chart for a rational approach to the empirical treatment of febrile neutropenia in a multidrug resistant, high prevalence setting.

Vancomycin-Resistant Enterococcus (VRE) Bacteremia During Acute Myeloid Leukemia (AML) Induction Therapy Is an Independent Predictor of Poor Outcome

AbstractAbstract 1487▪▪This icon denotes a clinically relevant abstractThe presence of VRE bacteremia in hematopoietic stem cell transplant recipients portends a worsening clinical course and poor overall survival (Avery et al; BMT, 2005). The impact of VRE bacteremia on outcome in AML patients (pts) receiving induction chemotherapy (IC) has not been established.We conducted an IRB-approved retrospective study of AML pts who received cytarabine-based IC at Cleveland Clinic between 2000–2008 to determine VRE rates and effect on complete remission (CR) and overall survival (OS). Data on age at AML diagnosis (dx), gender, diabetes, smoking history, history of antecedent hematological disorder, pathologic classification, hematologic parameters at dx and at VRE occurrence, metaphase cytogenetics (per CALGB/Alliance 8461), precedingnon-VRE bacteremias, invasive fungal infection (IFI), time from dx and induction to VRE and number of VRE infections, complete remission (CR) and overall survival (OS) were collected from our AML database.The association of these factors with VRE bacteremia was assessed using Fisher's exact test, the Cochran-Armitage trend test and Wilcoxon rank sum test. The impact of VRE bacteremia on OS was assessed using a 2:1 matched-pairs analysis based on gender and year of dx (+ 3 years), and factors known to influence outcome: age at dx (+ 5 years), etiology, and cytogenetic risk. The timing of VRE was also accounted for in the matching. Frailty models, which included a term for WBC at dx, were use to assess the impact of VRE bacteremia while taking into account both the impact of WBC and the paired nature of the data.Of 350 pts evaluable for analysis, the median age at dx was 57 years (range 19–88); 192 (55%) were male; 114 (33%) had secondary AML; median baseline WBC was 10.4K/mL (range, 0.48–550); cytogenetic risk distribution was favorable (14%), intermediate (54%), and unfavorable (32%); 45% were current or former smokers; 17% had a history of diabetes; and 7% had IFI. With the exception of IFI (16% in pts with VRE versus 6% in non-VRE pts, p=.04) there were no significant differences in these factors between the two groups (all p>.08). Of 37 pts (9.8%) who had documented VRE bacteremias during IC, the median interval from the start of IC to VRE infection was 17 days (range, 9–58). The majority (89%) of VRE bacteremias occurred in pts receiving IC between 2005 and 2008 (infection rate of 22%, 33/152) while only 4 infections occurred in 198 pts treated between 2000 and 2004 (infection rate of 2%). One plausible explanation for this epidemiologic shift could be the frequent use of fluoroquinolone prohylaxis to prevent neutropenic fever, which became routine in 2004. The overall CR rate for the cohort was 73%; 70% in VRE pts and 73% in non-VRE pts (p=0.7). Median follow-up was 72.2 months (range 1.1–145.4). Unadjusted median OS for the entire cohort was 12.8 months (95% C.I. 10.6–15.9); 7.1 months (95% C.I. 3.9–16.5) for VRE pts and 13.1 months (95% C.I. 11.2–16.3) for non-VRE pts (p=0.13, Figure 1A). Using the 2:1 matching to adjust for the impact of age, etiology, and cytogenetics, VRE pts had a significantly inferior OS compared to non-VRE pts even after adjusting for WBC at dx (p=0.04 and.80, respectively, Figure 1B). Mutivariableanalyses confirmed this association.In conclusion, VRE bacteremia in pts undergoing IC for AML is an independent risk factor for worse OS. The routine use of fluoroquinoloneprophylaxis is likely contributing to the increased prevalence of VRE bacteremia. Consideration should therefore be given to escalating VRE appropriate antibiotic care in these patients sooner and in the post-remission setting. [Display omitted] Disclosures:Saunthararajah:Cleveland Clinic Innovation: patent application for oral THU-decitabine., patent application for oral THU-decitabine. Patents & Royalties. Advani:Genzyme: Honoraria, Research Funding; Immunomedics: Research Funding. Maciejewski:NIH: Research Funding; Aplastic Anemia&MDS International Foundation: Research Funding.

Use of antibacterial prophylaxis in patients with chemotherapy-induced neutropenia

Antibiotic prophylaxis has been found to have multiple benefits in patients receiving intensive chemotherapy at high risk for infection. Interest continues in identifying what additional groups of high-risk patients might potentially benefit from its use. However, concerns about the potential emergence of antibiotic resistance have led to multiple recent studies exploring this issue. The use of antibiotic prophylaxis in pediatric leukemia, myelodysplastic syndromes, and hematopoietic stem cell transplant populations has been evaluated in recent studies. Several centers have noted increased rates of antibiotic resistance in patients receiving prophylaxis. Several single-center studies have emphasized the concern for the emergence of antibiotic resistance associated with the routine use of fluoroquinolone prophylaxis. The potential for antibiotic resistance continues to be worrisome and warrants further ongoing studies.

Clinical impact of fluoroquinolone prophylaxis in neutropenic patients with hematological malignancies

The routine use of fluoroquinolone prophylaxis in patients with neutropenia and hematological malignancies is controversial. This prophylaxis has been reported to have a positive impact in reducing infection-related mortality, but the consequent development of antibiotic resistance has become a concern. This study assessed the effect of discontinuing quinolone prophylaxis on the etiology and the resistance pattern of blood culture isolates and on the prognosis among febrile neutropenic patients receiving chemotherapy. The results of blood cultures obtained from febrile neutropenic patients between January 2003 and June 2009 were analyzed; these results were available through a computer database set up in 2003. Patients receiving quinolone prophylaxis between 2003 and 2005 showed a lower incidence of Gram-negative bacteria than patients not receiving prophylaxis between 2006 and 2009 (13.5%, n=9 vs. 48.1%, n=75). Interestingly, after discontinuing prophylaxis, approximately 70% of the Gram-negative bacteria isolated were quinolone-resistant, and some were extended-spectrum β-lactamase (ESBL) producers. The frequencies of quinolone-resistant Gram-positive bacteria isolated were similar between the period of quinolone prophylaxis and the period with no prophylaxis (61.1% vs. 64.3%). In both periods, all Gram-positive isolates were sensitive to vancomycin. The infection-related mortality was comparable between patients receiving prophylaxis and those not receiving prophylaxis (1.5%, n=1 vs. 1.3%, n=2). These findings suggest that quinolone prophylaxis for neutropenia does not induce a significant increase in the growth of quinolone- and multidrug-resistant bacteria. Rather, discontinuing quinolone prophylaxis may induce a dramatic increase in the growth of Gram-negative bacteria, including ESBL producers. Our results suggest that the necessity for quinolone prophylaxis in neutropenic patients should be determined based on local antibiotic resistance patterns.