Molecular epidemiology of methicillin-resistant Staphylococcus aureus at a low-incidence hospital over a 4-year period

OBJECTIVE: To study the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) over a prolonged period of time with the aid of a molecular typing method (ribotyping). SETTING: A 1,000-bed tertiary university medical center. PATIENTS AND METHODS: Defined epidemiological data were recorded for all patients culture-positive for MRSA between 1989 and 1992. Ribotyping of MRSA strains was performed using three restriction enzymes: EcoRV, HindIII, and KpnI. RESULTS: From 1989 to 1992, MRSA was isolated from clinical specimens in 98 patients and from surveillance cultures in 27 patients. Among the 122 isolates available for typing, 26 different ribotypes were identified. In 20% of the cases, MRSA was community-acquired, and a third of these patients never had been hospitalized previously. Nine ribotypes were responsible for more than one case (2 to 64 patients); 17 appeared only once. Epidemiological data correlated with ribotyping results revealed 14 epidemiologic clusters involving six different ribotypes, whereas only three outbreaks were suspected initially. The median follow-up after the last isolation of a given ribotype was 14 months (range, 1 to 42) for clusters and 25 months (range, 1 to 46) for ribotypes that appeared only once. During clusters, only 16% of the cases occurred after the implementation of control measures in the ward (breakthrough cases). CONCLUSIONS: The high diversity of MRSA strains observed over 4 years suggested that new strains were introduced continuously in our hospital. Furthermore, that 17 ribotypes were isolated only once, that breakthrough cases represented only 16% of the cases in clusters, and that the follow-up duration after the last isolation of a given ribotype was more than 14 months suggest that infection control measures were effective in limiting the nosocomial spread of MRSA over a prolonged period of time

A Light Weight Name Service and its use within a Collaborative Editor.

This paper presents the LWNS a light weight name service specially designed for groupware applications and an example of its use. The chosen application, called Duplex, is a collaborative editing environment for users connected through the Internet. It proposes a model based on splitting the document into independent parts, maintained individually and replicated within a distributed kernel. Naming is an important aspect of such application since objects (document parts) are replicated and distributed over the large heterogeneous network. However, this set is small (typically a few dozen elements) and composed of objects whose names are contextual to the document. Replicas are however maintained in heterogeneous file systems with no global naming scheme consistent with the name space of the collaboration. This requires a dedicated name service specially designed to solve this problem in large scale distributed applications. 1 Introduction Distributed application such that a collaborati..

A Light Weight Name Service and its use within a Collaborative Editor

\begin{abstract} This paper presents the LWNS a light weight name service specially designed for groupware applications and an example of its use. The chosen application, called {\sc Duplex}, is a collaborative editing environment for users connected through the Internet. It proposes a model based on splitting the document into independent parts, maintained individually and replicated within a distributed kernel. Naming is an important aspect of such application since objects (document parts) are replicated and distributed over the large heterogeneous network. However, this set is small (typically a few dozen elements) and composed of objects whose names are contextual to the document. Replicas are however maintained in heterogeneous file systems with no global naming scheme consistent with the name space of the collaboration. This requires a dedicated name service specially designed to solve this problem in large scale distributed applications. \end{abstract

Quantitative antibiogram typing using inhibition zone diameters compared with ribotyping for epidemiological typing of methicillin-resistant Staphylococcus aureus

Antibiogram typing of methicillin-resistant Staphylococcus aureus with selected antibiotics was evaluated as a primary epidemiological typing tool and compared with ribotyping. Antibiograms were derived with the Kirby-Bauer disk diffusion method by using erythromycin, clindamycin, cotrimoxazole, gentamicin, and ciprofloxacin. For typing, antibiogram data were analyzed by similarity analysis of disk zone diameters (quantitative antibiogram typing). One hundred seventy-two isolates were typed. Reproducibility reached 98% for the quantitative antibiogram and 100% for ribotyping. With three selected restriction enzymes (EcoRV, HindIII, and KpnI), 40 epidemiologically unrelated isolates could be classified into 21 ribotypes, whereas quantitative antibiogram typing classified these isolates into 19 groups. To evaluate the discriminatory power of the methods, we calculated an index of discrimination from data obtained with these 40 isolates. This index takes into consideration both the number of types defined by the typing method and their relative frequencies. With both ribotyping and quantitative antibiogram typing, high discrimination indices (0.972 and 0.954, respectively) were obtained. When epidemiological links between patients (ward, period of hospitalization, and contacts between staff and patients) were compared with the results of ribotyping or the quantitative antibiogram typing method, it appeared that both methods were able to discriminate epidemiological clusters, with only a few discrepancies. In conclusion, quantitative antibiogram typing, although not necessarily based on genomic markers, is a simple method which enables a reliable workup of methicillin-resistant S. aureus epidemic when sophisticated molecular typing methods are not available