Enterococcal bacteremia: risk factors for vancomycin resistance and predictors of mortality.

OBJECTIVE: To identify risk factors for vancomycin resistance and mortality in enterococcal bacteremia. DESIGN: Historical cohort study. SETTING: A large academic medical center with a high prevalence of vancomycin-resistant enterococci (VRE). PATIENTS: Two hundred sixty patients with enterococcal bacteremia, of whom 72 (28%) had VRE. RESULTS: Independent risk factors for infection with VRE were the mean number of antibiotic days (P<.001), renal insufficiency (P<.001), mean days of vancomycin use (P = .005), and neutropenia (P = .013). A trend toward a significant association between metronidazole use and VRE also was noted (P = .068). Mortality was attributable to the bacteremia in 96 patients (37%). Severity of illness (P<.001) and age (P = .020) were independent risk factors for mortality. Vancomycin resistance was not, however, an independent predictor of mortality. CONCLUSION: These results suggest that restrictions on antibiotic use, particularly in patients with renal insufficiency and neutropenia, may help to combat the rising incidence of VRE. Although patients with VRE bacteremia demonstrated higher mortality rates than patients with infection due to susceptible isolates, vancomycin resistance was not an independent predictor of mortality in these patients and likely serves more as a marker of underlying severity of illness.     

Early bacteremia in pediatric hematopoietic stem cell transplant patients on oral antibiotic prophylaxis

BACKGROUND: Bacteremia occurs during hematopoietic stem cell transplant (HSCT) in 20%-25% of patients and the use of gut decontamination (GD) to decrease this risk is controversial. Our purpose was to determine the incidence of bacteremia and antimicrobial resistance post-HSCT in pediatric patients receiving GD, and to identify risk factors associated with infection. PROCEDURES: This was a retrospective cohort study of 182 pediatric patients undergoing first HSCT for malignant disease at The Children's Hospital of Philadelphia from January, 1999 to December, 2002. We examined the impact of age, sex, race, diagnosis, disease status, conditioning regimen, recent bacteremia, stem cell source, donor, graft versus host disease prophylaxis agents, and mucositis severity using Cox proportional hazard models. GD consisted of amoxicillin (azithromycin, if penicillin allergic) and oral gentamicin. Outcome was first episode of bacteremia prior to absolute neutrophil count (ANC) 500/mm(3). Antibiotic susceptibilities were performed on all isolates. RESULTS: Seventy-four patients (41%) developed bacteremia. The majority were Gram-positive cocci, with Staphylococcal (50%) and Streptococcal species (28%) the most common. Gram-negative organisms were identified in 22% with Pseudomonas (5.7%) and Klebsiella species (3.4%) the most common. Of the Streptococcal infections, 72% were resistant to ampicillin; only 25% of the Gram-negative bacteria were resistant to gentamicin. Race was the only factor associated with early bacteremia (hazard ratio 2.3 for non-Caucasian, non-African-American patients, CI 1.3-4.3, P = 0.007). CONCLUSIONS: Early bacteremia is common after HSCT, despite the use of GD. Resistant Gram-positive organisms predominate, consistent with recent trends in immunocompromised patients. Although used in practice, there is no clear evidence for the efficacy of GD and this study provides the basis upon which to develop a randomized clinical trial evaluating the current GD regimen with placebo.     

Patients' request for and emergency physicians' prescription of antimicrobial prophylaxis for anthrax during the 2001 bioterrorism-related outbreak

Background  

Inappropriate use of antibiotics by individuals worried about biological agent exposures during bioterrorism events is an important public health concern. However, little is documented about the extent to which individuals with self-identified risk of anthrax exposure approached physicians for antimicrobial prophylaxis during the 2001 bioterrorism attacks in the United States.     

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Ohne Zusammenfassung     

Investigating the association between antibiotic use and antibiotic resistance: impact of different methods of categorising prior antibiotic use

Many studies have explored the association between antibiotic use and antibiotic resistance. However, methods employed in these studies to categorise prior antibiotic use (e.g. by class, by spectrum) have not been well described. The impact of using different categorisation methods on identifying risk factors for resistance is unknown. To explore these issues, we focused on extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella spp. (ESBL-EK) as a model. First, we conducted a systematic review of studies of risk factors for ESBL-EK to characterise past approaches to categorising antibiotic use. Second, we re-analysed data from a prior study of risk factors for ESBL-EK. Two separate multivariate models of risk factors for ESBL-EK were constructed: one with prior antibiotic use categorised by class and the other with prior antibiotic use categorised by spectrum of activity. Among the 20 articles that met the inclusion criteria for the systematic review, there was tremendous variability in how prior antibiotic use was categorised (e.g. by agent, class, spectrum and/or a combination of these). No study justified its choice of categorisation method. In the re-analysis of the existing data set, multivariate models of risk factors for ESBL-EK using 'class' and 'spectrum' categorisations differed substantially. In conclusion, there has been no consistent approach to categorising antibiotic use in studies of risk factors for ESBL-EK. Different categorisation schemes were shown to have a substantial impact on study results, particularly for the antibiotic exposures associated with resistance. Elucidating these issues is critical if effective strategies to curb resistance are to be designed.     

Obesity and NK cells affect the expression of the long form of the leptin receptor Ob-Rb in liver of F344 rats

In obesity, the regulatory effects of leptin, a primarily adipocyte-derived hormone, are severely disturbed affecting the control of energy homeostasis and immune functions. In addition, recent studies indicate that specific immune cells can affect glucose and lipid metabolism of liver. However, the contribution of body weight and immune cells, such as Natural Killer (NK) cells, to the regulation of the leptin-receptor expression remains elusive. Therefore, we investigated the expression of the signal-transducing long form of the leptin receptor (Ob-Rb) in diet-induced obesity and after adoptive cross-over NK cell transfer between normal weight and obese male F344 rats. Expression of Ob-Rb was significantly increased in liver in diet-induced obese rats as compared to normal weight littermates. Similarly, the expression of Ob-Rb was higher in liver of obese animals that received NK cells from either obese or normal weight donors as compared to normal weight animals that received NK cells from normal weight donors. Interestingly, normal weight animals that were transferred with NK cells from obese donors also showed a tendency towards a higher Ob-Rb expression. In contrast to the findings in liver, the expression of Ob-Rb in spleen or lung remained unaffected by changes in body weight or cross-over NK cell transfer. Our results suggest that the expression of Ob-Rb mRNA in liver, but not in spleen or lung, is dependent on the body weight but can also be influenced by NK cells, thereby indicating a bidirectional cross-talk between the metabolic and the immune system.