The incidence of methicillin-resistant Staphylococcus aureus (MRSA) with reduced susceptibility to vancomycin in the University Medical Centre Ljubljana between the years 2005 and 2010

• Main Authors: Nina Cerkvenik, Bojana Beović, Manica Mueller–Premru
• Format: Article
• Language: English
• Published: Slovenian Medical Association 2014-08-01
• Series: Zdravniški Vestnik
• Subjects: hVISA; VISA; MIC; Etest; Vitek 2
• Online Access: http://vestnik.szd.si/index.php/ZdravVest/article/view/1253
• ISSN: 1318-0347; 1581-0224

<p><strong>Background</strong>: Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important antibiotic-resistant bacteria causing nosocomial infections in the world. A first-line treatment for infections with MRSA continues to be vancomycin. Due to its increased consumption, three MRSA phenotypes with reduced susceptibility to vancomycin (hVISA, VISA, VRSA) have emerged. We wanted to know to what extent these phenotypes occur in the University Medical Centre Ljubljana.</p><p><strong>Material and methods</strong>: We tested susceptibility to vancomycin of 101 MRSA isolates obtained from blood samples of patients admitted to the University Medical Centre Ljubljana between August 2005 and September 2010; the isolates were stored in the database of the Laboratory of blood cultures at the Institute of Microbiology and Immunology. We carried out Etests to determine the minimum inhibitory concentration (MIC) and Etest macro-method to identify heterogeneous vancomycin-intermediate S. aureus strains (hVISA).</p><p><strong>Results</strong>: 100 MRSA isolates were susceptibile to vancomycin with Etest, and one was vancomycin-intermediate S. aureus (VISA). With Etest macro-method, four isolates were additionally characterized as hVISA. Average MIC values of vancomycin show a minimal growth over the years.</p><p>Conclusions: hVISA and VISA isolates from blood samples are still rare in the University Medical Centre Ljubljana. MIC values will have to be closely monitored in the future. At the same time, we will have to reduce the use of vancomycin.</p>