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Controlling an outbreak of Staphylococcus aureus in a vascular and cardiac surgery ward

Abstract number: 1733_808

Kristóf K., Antmann K., Szalay Z., Pesti N., Nagy K., Rozgonyi F.

Objectives: Since January 2001 a fluctual increase in S. aureus infections has been recognized in a vascular and cardiac surgery ward of the Semmelweis University. The outbreak has been characterised and the S. aureus infections were monitored both phenotypically and genotypically.

Methods: From January 2001 to September 2006 a total of 511 S. aureus isolates were cultured. Identification of S. aureus strains was carried out on the basis of catalase positivity, gold pigment, beta-haemolysis and clumping factor. The presence of mecA and nucA genes was detected by PCR. Both the disc diffusion and the microdilution methods were used according to NCCLS/CLSI recommendations to determine the antibacterial sensitivity to vancomycin, teicoplanin, gentamicin, tobramycin, amikacin, netilmicin, ciprofloxacin, trimethoprim/sulphamethoxasole, doxycycline and linesolid. The clonal relationship of the isolates was determined by pulsed field gel-electrophoresis using SmaI enzyme digestion. Multilocus sequence typing of the representative MRSA isolates is in process.

Results: 511 cases of S. aureus infection were identified during the investigation period. The incidence of MRSA was the highest in the year 2005 (27.6% of all S. aureus isolates), while the earlier frequency was 7.14%, 5.66%, 7.5% and 6.24% from 2001 to 2004. Twelve antibiotic resistance patterns were found among the MRSA isolates. The commonest was the multiple resistance to all aminoglycosides, erythromycin, clindamycin and ciprofloxacin. This phenotype showed a mean incidence of 59% of all MRSA isolates in 2005–2006. Its evolution ranging from 0% in 2003 to the alarming proportion of 63.9% in 2005. The spread of this epidemic strain was stopped after introducing strict hygienic measures with a close cooperation between microbiologists and hygienists. In 2006, the MRSA incidence decreased to 10.7%. PFGE analysis revealed MRSA strains form four types with different frequency. PFGE type C was the most common.

Conclusions: Although the outbreak was sufficiently controlled in the point of view of hospital hygiene, however multiple resistant MRSA strains of similar clonality could select causing a disadvantage in the entire microbiological eradication of them.

Supported by OTKA No.: T 46186

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Subject:
Location: ICC, Munich, Germany
Presentation type:
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