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Molecular characterisation of methicillin-resistant Staphylococcus aureus isolates in a tertiary hospital in Madrid (Spain)

Abstract number: P530

García-Cañas A., Vindel A., García-Hierro P., Trincado P., Boquete T., Ballesteros C., Bautista V., Alos J.I.

Objectives: The aim of this study was to determine which clones of methicillin-resistant Staphylococcus aureus (MRSA) are circulating in our hospital and to analyse the genetic relationships of these strains.

Methods: We studied a total of 52 MRSA strains isolated from clinical samples of 52 hospitalised adult patients (10 patients were admitted to the medical/surgical intensive care unit, ICU, and 4 to the burn ICU) during 2007 at the Department of Microbiology of Getafe University Hospital in Madrid. The sources of the isolates were nares (65%), oropharyngeal (15%), rectal (7%) and wound (13%) swabs. The 52 MRSA were characterised by phage typing using the 23 phages of the Basic International Set at 100 RTD and 1,000 RTD, pulsed-field gel electrophoresis (PFGE) following SmaI digestion of chromosomal DNA as described by Cuevas et al. (Clin Microbiol Infect 2007;13: 250–256) and SCCmec typing wich was performed using several multiplex PCR strategies [1–3].

Results: Of the 52 MRSA isolates, 33 (63%) belonged to phage group III and 5 (10%) belonged to phage group III and also were lysed by phage 81. The rest (14 strains) were non-typeable. Genotyping by PFGE showed that the majority of the strains belonged to the clones E-7 (16 isolates, 31%) and E-8 (14 isolates, 27%) with the next subtypes: 5 strains belonged to E-7a, 8 to E-7b, 3 to E-7c, 8 to E-8a, 5 to E-8b and 1 to E-8c. We observed two isolates belonging to E-11, one to E-13 and one to E-20. The remaining 18 MRSA belonged to sporadic clones but 3 of these strains presented the same PFGE pattern and were isolated from 3 different patients who were admitted to the burn ICU at the same time.

SCCmecIV accounted for 46 (88%) of the isolates (76% IVa, 22% IVc and 2% IVh). The remaining 6 strains (12%) carried SCCmecI and all were sporadic clones.

Conclusions: The majority of the strains showed the most common PFGE types present throughout Spain (E-7 and E-8). The genotypes E7, E8, E11 and E20 belong to the clonal group 5 (paediatric clon). We also found one strain with the PFGE profile E-13 (SCCmecIVh) belonging to the EMRSA-15 clone which is epidemic in the United Kingdom. It is important to note that we observed an outbreak in the burn ICU of a sporadic clone carried SCCmecIVa.

References

1. Milheirico et al. J  Antimcrob Chemother 2007 Jul; 60(1): 42–8

2. Milheirico et al. Antimicrob Agents Chemother 2007 Sep; 51(9): 3374–7

3. Oliveira et al. Antimicrob Agents Chemother 2002 Jul; 46(7): 2155–61.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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