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Identifier

000380978

Title

Επιδημιολογία και παράγοντες κινδύνου για αποικισμό από Εντερόκοκκο ανθεκτικό στη βανκομυκίνη σε ένα τριτοβάθμιο αντικαρκινικό κέντρο

Alternative Title

Epidemiology and risk factors for colonization by vancomycin resistante enterococcus at a rertiary care center

Author

Αλμυρούδης, Νικόλαος Γ

Thesis advisor

Σαμώνης, Γεώργιος

Reviewer

Γεωργούλιας, Β.
Γκίκας, Α.
Μαυρουδής, Δ.
Παπαδάκη, Ε.
Γανωτάκης, Ε.
Κοφτερίδης, Δ.

Abstract

ΑΓΓΛΙΚΗ ΠΕΡΙΛΗΨΗ - SUMMARY IN ENGLISH OBJECTIVE: Patients with hematologic malignancies are at high risk for colonization and infection by vancomycin resistant Enterococcus (VRE). We studied the molecular epidemiology of colonization and bacteremia by VRE in patients with hematologic malignancies. The purpose of the study was to determine the clonal or sporadic nature of the outbreak, as part of an investigation that aimed to define interventions to prevent colonization and infection by VRE. In the second part of the thesis we performed a case-control study to identify risk factors for colonization by VRE, other than exposure to the hospital environment. The purpose of the study was to identify potentially modifiable risk factors for colonization that could be altered in order to contain the outbreak. Based on the results of the case-control study that demonstrated an association between exposure to ceftazidime and colonization by VRE, the treatment strategy of neutropenic fever was modified to reduce patients’ exposure to ceftazidime. The ceftazidime was substituted by piperacillin-tazobactam as the antibiotic of choice for the treatment of neutropenic fever. We studied the impact of this strategy on the incidence of colonization and bacteremia by VRE in patients with hematologic malignancies. PATIENTS AND METHODS: The genotypic analysis included patients with hematologic malignancies and recipients of hematopoietic stem cell transplantation admitted at the hematology units at Roswell Park Cancer Institute. According to the infection prevention policies all patients with hematologic malignancies underwent weekly surveillance with perianal swabs for VRE and if colonized were placed in contact isolation. The molecular epidemiology was studied with pulsed field gel electrophoresis on samples from perirectal swabs and blood cultures collected over a period of one year. Digestion of the bacterial chromosome was performed with SmaI restriction enzyme. Risk factors for colonization by VRE were identified through a retrospective "case-control" study. The study included patients with hematologic malignancies and recipients of hematopoietic stem cell transplantation admitted to the hospital during a period of three years. Colonized patients were placed in strict contact isolation. Cases included patients colonized by VRE and controls patients negative for VRE colonization. Cases and controls were matched individually by age, gender and admitting service in a 1:2 allocation. All variables were recorded from admission to the time of colonization for the cases and an equal time for controls. 15 The study on the impact of substitution of ceftazidime by piperacillin-tazobactam on the incidence of colonization and bacteremia by VRE included all patients with hematologic malignancies and recipients of hematopoietic stem cells transplantation admitted at the hospital for any reason. During the study periods, all inpatients were undergoing weekly surveillance cultures on rectal swabs and if positive they were placed in contact isolation. Data on the incidence of colonization and bacteremia were recorded prospectively while data on antibiotic utilization were collected retrospectively. The impact of colonization and bacteremia was calculated in number of events per 1,000 patient days of care during two periods, of three years duration each. These periods corresponded to the time when either ceftazidime or piperacillin-tazobactam was the antibiotic of choice for the treatment of neutropenic fever. The total antibiotic use was calculated for the entire population, as days on antibiotics per 1,000 patient days of care. Pearson correlation coefficient was used to correlate the incidence of colonization and bacteremia with the antibiotic use. RESULTS: Molecular genotyping showed that with the exception of small clones the isolates of VRE from colonized or bacteremic patients were primarily genetically distinct. This finding demonstrates the principally sporadic nature of the outbreak. The case-control study on risk factors for colonization showed that colonization occurred at a median of 14 days and was associated with longer hospital stay. Previous use of ceftazidime was associated with colonization (p:<0.001), while intravenous vancomycin and antibiotics with anaerobic activity did not emerge as risk factors. There was no association with neutropenia or presence of colonic mucosal disruption, and severity of illness was similar in both groups. During the time period when piperacillin-tazobactam was used as initial therapy for the management of febrile neutropenia, the incidence of colonization by VRE decreased from 6.04 to 5.52 per 1,000 patient days of care but not at a statistically significant level (p: 0.65). During the same time period, the incidence of bacteremia due to VRE decreased from 3.97 to 2.62 episodes per 1,000 patient days of care (p: 0.004). The Pearson correlation coefficient demonstrated a negative association between bacteremia and piperacillin-tazobactam use (p: 0.005), and a trend towards a positive correlation between the incidence of bacteremia and ceftazidime use (p: 0.05). No correlation between the incidence of bacteremia and the overall use of antibiotics was identified. CONCLUSION: Molecular studies showed that in the majority of colonized or bacteremic patients the strains were unique, arguing that VRE acquisition was sporadic rather than resulting from a common source of transmission. Exposure to antibiotics, namely ceftazidime, 16 predicts the risk for colonization by VRE and not host factors or breaches in the infection prevention practices. A therapeutic strategy that involves the use of piperacillin-tazobactam as initial therapy for the management of neutropenic fever may reduce the incidence of bacteremia due to VRE in patients with hematologic malignancies.

Language

Greek

Subject

Bacteremia

Colonization

Enterococcus

Epidemiology

Hematologic malignancies

Hematopoietic stem cell transplantation

Risk factors

Vancomycin resistance

Αντοχή στη Βανκομυκίνη