Topic:

Diagnostics

Abstract No.:

ISE.444

Title:

Comparison of mecA polymerase chain reaction with phenotypic methods for the detection of methicillin-resistant Staphylococcus aureus

Author(s):

L. M. Junie¹, I. Spiliopoulou², E. D. Anastassiou², L. M. Simon¹, M. Flonta³, A. Almasanu³, D. Homorodean⁴, A. Jodal⁴, R. Ilie¹; ¹University of Medicine and Pharmacy , Microbiology, Cluj Napoca/RO, ²University of Patras, Department of Microbiology, Patras/GR, ³Infectious Diseases Hospital, Laboratory, Cluj Napoca/RO, ⁴Leon Daniello Pneumoftiziological Hospital, Microbiology, Cluj Napoca/RO

Abstract:

Background: Methicillin resistant strains of Staphylo-coccus aureus (MRSA) were identified shortly upon the introduction of methicillin into the clinical practice. Previous study showed MRSA had risen up to 33% in hospitals. Standardized methods of the susceptibility test have been used for the detection of resistant strains. However, phenotypic expression of methicillin-resistance is usually heterogeneous. In addition, methicillin-resistance is influenced by culture conditions. Rapid detection of of MRSA is desirable. Several PCR assays based on the DNA sequence information have been used for detection of MRSA strains. The PCR methods have high sensitivity and specificity and were independent of the physical and chemical conditions of culture.
Methods: Bacterial strains: The study included 47 strains of S.aureus isolated from patients hospitalizes in Universities Hospitals in Cluj Napoca (Infectious Diseases Clinic and Leon Danielli Hospital), during March-April 2008. The identification of S. aureus strains was made by phenotypic methods, ApiBioMerieux and automated methods (Vitek2Compact bioMerieux). The PBP2’ latex agglutination test, Cefoxitin E-test and Oxacillin MIC as phenotypic methods of MRSA detection were evaluated and compared with molecular method (mecAdetection by PCR). mecA detection by PCR has been made at the University Hospital of Patras, Greece.
Results: Strains were isolated from patients of different ages. S. aureus strains were isolated from hospitalized patients, including intensive care wards and other units. S. aureus strains were isolated from different pathological products. We followed the detection of MecA gene by PCR as the standard method to identify MRSA strains. 57,45 % of  strains isolated strains (27/47) were MRSA and 42,56 % (20) were MSSA. The PBP2’ latex agglutination test detected the penicillin-binding protein 2a (PBP2a) antigen in 26 (55,32% ) of 47 tested strains leading to a sensitivity of 96,3% with mec A gene detection.