Virulence patterns of Staphylococcus aureus hospital strains isolated in Bucharest, Romania

Staphylococcus (S.) aureus is an opportunistic pathogen with the ability to invade and persist in unprofessional phagocytes. Romania is amongst the countries with the highest prevalence of methicillin-resistant S. aureus, with level of incidence about 70% from all isolated S. aureus strains. The objective of this study was to analyse and compare the virulence patterns of isolated methicillin resistant S. aureus strains. Materials and methods. The study was realized on the 144 MRSA strains isolated from nasal secretions and nosocomial infections between 2011-2014, from patients of the Emergency Institute for Cardiovascular Diseases "Prof. Dr. C. C. Iliescu", Bucharest. The strains were identified using conventional methods and confirmed using the Vitek 2 System analyzer. The presence of some virulence factors was tested phenotypically using specific substrata and also at molecular level, by simplex and multiplex PCR. Results and discussions. The comparative analysis of the distribution of virulence factors depending on the isolation site revealed that at least one virulence factor is expressed in all samples. The most virulent strains were isolated from blood cultures and the peritoneal fluid. Conclusions. This study has provided evidence that S. aureus strains express different virulence patterns according to isolation sources.