Comparison of unit-specific and hospital-wide antibiograms: potential implications for selection of empirical antimicrobial therapy.

OBJECTIVE: To identify differences between unit-specific and hospital-wide antibiograms and to determine the potential impact of these differences on selection of empirical antimicrobial therapy. SETTING: A 625-bed tertiary care medical center. METHODS: Antimicrobial susceptibility results were collected for all inpatient clinical bacterial isolates recovered over a 3-year period; isolates were categorized by the hospital location of the patient at the time of sampling and by the anatomic site from which the isolate was recovered. Antibiograms from each unit were compiled for the most commonly isolated organisms and were compared to the hospital-wide antibiogram. RESULTS: A total of 9,970 bacterial isolates were evaluated in this study, including 2,646 enterococcal isolates, 2,806 S. aureus isolates, 2,795 E. coli isolates, and 1,723 Pseudomonas aeruginosa isolates. The percentages of bacterial isolates resistant to antimicrobials were significantly higher in the medical ICU and surgical ICU than the hospital-wide antibiogram would have predicted, whereas the percentages of isolates susceptible to antimicrobials were significantly higher in the non-ICU units, compared with the hospital overall. However, on general medicine units, the prevalence of susceptibility to levofloxacin was significantly lower than that for the hospital overall. CONCLUSIONS: Unit-specific antibiograms are important for making informed decisions about empirical antimicrobial therapy, because the hospital-wide antibiogram may mask important differences in susceptibility rates across different units. These differences may have important implications for selecting the optimal empirical antimicrobial therapy.

Limiting the emergence of extended-spectrum Beta-lactamase-producing enterobacteriaceae: influence of patient population characteristics on the response to antimicrobial formulary interventions.

BACKGROUND: Effective methods to control the emergence of extended-spectrum beta -lactamase-producing Escherichia coli and Klebsiella species (ESBL-EK) remain unclear. Variations in the patient populations at different hospitals may influence the effect of antimicrobial formulary interventions. METHODS: To examine variations across hospitals in the response to antimicrobial interventions (ie, restriction of ceftazidime and ceftriaxone) designed to curb the spread of ESBL-EK, we conducted a 5-year quasi-experimental study. This study was conducted at 2 hospitals within the same health system: Hospital A is a 625-bed academic medical center, and Hospital B is a 344-bed urban community hospital. All adult patients with a healthcare-acquired clinical culture of ESBL-EK from July 1, 1997 through December 31, 2002 were included. RESULTS: After the interventions, the use of ceftriaxone decreased by 86% at Hospital A and by 95% at Hospital B, whereas the use of ceftazidime decreased by 95% at Hospital A and by 97% at Hospital B. The prevalence of ESBL-EK at Hospital A decreased by 45% (P < .001), compared with a 22% decrease at Hospital B (P = .36). The following variables were significantly more common among ESBL-EK-infected patients at Hospital B: residence in a long-term care facility (adjusted odds ratio, 3.77 [95% confidence interval, 1.70-8.37]), advanced age (adjusted odds ratio, 1.04 [95% confidence interval, 1.01-1.06]), and presence of a decubitus ulcer (adjusted odds ratio, 4.13 [95% confidence interval, 1.97-8.65]). CONCLUSIONS: The effect of antimicrobial formulary interventions intended to curb emergence of ESBL-EK may differ substantially across institutions, perhaps as a result of differences in patient populations. Variability in the epidemiological profiles of ESBL-EK isolates at different hospitals must be considered when designing interventions to respond to these pathogens.

High rate of coadministration of di- or tri-valent cation-containing compounds with oral fluoroquinolones: risk factors and potential implications.

BACKGROUND: The characteristics of fluoroquinolone use that increase the risk of selecting for fluoroquinolone resistance remain unclear. Exposure to subtherapeutic levels of fluoroquinolone promotes bacterial development of fluoroquinolone resistance. Oral fluoroquinolone absorption is significantly impaired by coadministration with many common di- or tri-valent cation-containing compounds (DTCCs), and this interaction has been associated with therapeutic failure. However, the prevalence of, and risk factors for, in-hospital coadministration of oral fluoroquinolones with DTCCs is unknown. DESIGN: Case-control study. SETTING: A 625-bed, tertiary-care medical center. PATIENTS: All inpatients who were dispensed oral levofloxacin from July 1, 1999, to June 30, 2001, were included. Coadministration was defined by documented administration of any DTCC within 2 hours of levofloxacin. Complete coadministration was defined as coadministration complicating every dose of a course of levofloxacin. RESULTS: A subset of 3,227 (41.0%) of 7,871 doses of levofloxacin that occurred during the same calendar day as any DTCC was selected for further review. Overall, 1,904 (77.1%) of 2,470 doses of oral levofloxacin reviewed were complicated by coadministration with at least one DTCC. On multivariable analysis, an increased number of prescribed medications was significantly associated with complete coadministration (per increase of one medication: OR, 1.05; CI95, 1.01-1.10; P = .036), whereas patient location in an ICU was protective (OR, 0.51; CI95, 0.30-0.87; P = .013). If our prevalence results are extrapolated to all patients receiving oral levofloxacin at our hospital, approximately one in three doses was complicated by coadministration. CONCLUSION: Coadministration of fluoroquinolones with DTCCs is extremely common and significantly associated with polypharmacy.

Fluoroquinolone utilization in the emergency departments of academic medical centers: prevalence of, and risk factors for, inappropriate use.

BACKGROUND: Resistance to fluoroquinolone (FQ) antibiotics has risen markedly in recent years and has been associated with increasing FQ use; however, few data exist regarding FQ use patterns. Designing strategies to limit FQ resistance by optimizing FQ use depends on identifying patterns of inappropriate FQ use. Use of FQs in emergency departments (EDs) has not been studied. METHODS: We studied 100 consecutive ED patients who received an FQ and were subsequently discharged. Appropriateness of the indication for use was judged according to existing institutional guidelines. A case-control study was conducted to identify the prevalence of, and risk factors for, inappropriate FQ use. RESULTS: Of 100 total patients, 81 received an FQ for an inappropriate indication. Of these cases, 43 (53%) were judged inappropriate because another agent was considered first line, 27 (33%) because there was no evidence of infection based on the documented evaluation, and 11 (14%) because of inability to assess the need for antimicrobial therapy. Although the prevalence of inappropriate use was similar across various clinical scenarios, there was a borderline significant association between the hospital in which the ED was located and inappropriate FQ use. Of the 19 patients who received an FQ for an appropriate indication, only 1 received both the correct dose and duration of therapy. CONCLUSIONS: Inappropriate FQ use in EDs is extremely common. Efforts to limit emergence of FQ resistance must address the high level of inappropriate FQ use in EDs. Future studies should evaluate the impact of interventions designed to reduce inappropriate FQ use in this setting.

Changes in the prevalence of vancomycin-resistant enterococci in response to antimicrobial formulary interventions: impact of progressive restrictions on use of vancomycin and third-generation cephalosporins.

This study sought to assess the impact of restricting use of vancomycin and third-generation cephalosporins on vancomycin-resistant enterococci (VRE) prevalence. All clinical enterococcal isolates identified at a large academic medical center during a 10-year period were analyzed. Changes in VRE prevalence after sequential restrictions on use of vancomycin and third-generation cephalosporins were evaluated. The correlation between antibiotic use and VRE prevalence was also investigated. Vancomycin use initially decreased by 23.9% but returned to preintervention levels by the end of the study. Third-generation cephalosporin use decreased by 85.8%. However, VRE prevalence increased steadily from 17.4% to 29.6% during the 10-year period (P<.001). Clindamycin use was significantly correlated with VRE prevalence. Restricting the use of vancomycin and third-generations cephalosporins had little impact on VRE prevalence. The association between clindamycin use and the prevalence of VRE suggests that restriction of this and perhaps other antianaerobic agents might be an important component of future antimicrobial interventions.

Longitudinal trends in fluoroquinolone resistance among Enterobacteriaceae isolates from inpatients and outpatients, 1989-2000: differences in the emergence and epidemiology of resistance across organisms.

We conducted a 12-year study to identify and compare trends in annual prevalence of fluoroquinolone (FQ) resistance among Enterobacteriaceae isolates obtained from inpatients and outpatients in our health care system. A total of 46,070 clinical Enterobacteriaceae isolates underwent susceptibility testing. Although there were significant increases in inpatient FQ resistance for all Enterobacteriaceae, FQ resistance trends differed significantly across Enterobacteriaceae (P<.001). For isolates obtained from outpatients, only Escherichia coli and Proteus mirabilis demonstrated significant increases in FQ resistance (P<.001 for each). Trends in outpatient FQ resistance also differed significantly across Enterobacteriaceae (P<.001). There were significant differences between inpatient and outpatient FQ resistance trends for all Enterobacteriaceae except P. mirabilis and Enterobacter cloacae. Although hospital-wide use of certain antibiotics correlated significantly with inpatient FQ resistance, these correlations differed substantially across organisms. Efforts to elucidate the epidemiology of FQ resistance and identify targets for intervention must recognize and account for the variability of FQ resistance across organisms and clinical settings.

Emergence of resistance to chloramphenicol among vancomycin-resistant enterococcal (VRE) bloodstream isolates.

Therapeutic options for vancomycin-resistant enterococcal (VRE) bloodstream infections are extremely limited. Chloramphenicol is effective when VRE isolates are susceptible to this agent. However, longitudinal trends in chloramphenicol-resistant VRE (CR-VRE) are unknown. The possible association between CR-VRE and antibiotic use has not been studied. We analyzed the antimicrobial susceptibility profiles of all VRE blood isolates from 1991-2000 at our institution. We performed a correlational study to examine the relationship between annual hospital-wide use of specific antibiotics and antibiotic classes and CR-VRE prevalence. During the 10-year study period, the prevalence of CR-VRE increased from 0 to 11% ( P< 0.001, trend). CR-VRE prevalence was correlated only with chloramphenicol use (P=0.05 ) and quinolone use (P= 0.01 ). If these trends continue, dependence on newer, more expensive agents will increase. The correlation between both chloramphenicol use and quinolone use and the prevalence of CR-VRE suggests that efforts to preserve the utility of chloramphenicol in VRE infections may depend on optimizing the use of these agents.