367. Molecular typing of MRSA-isolates of a university medical center during a time period between 2004 and 2008
Session: Poster Abstract Session: MRSA, MSSA, Enterococci
Thursday, October 3, 2013
Room: The Moscone Center: Poster Hall C
Background:

MRSA is still a challenging problem in most countries worldwide. In Germany the frequency of MRSA is about 20% with a tendency to lower figures in recent years. The contribution of caMRSA strains is still low, whereas in other countries caMRSA begins to displace hospital associated MRSA (haMRSA). The aim  of our study was to analyze the appearance and distribution of molecular MRSA-types in our University Medical Center (UMC) in Mainz.

Methods:

We examined 1114 primary MRSA isolates from a time period between 2004 and 2008; 762 isolates were out of the UMC and were compared with 352 isolates from another big hospital in Mainz (Catholic Clinic Mainz, CCM). Verification of Methicillin resistance was verified by resistance against Cefoxitin (FOX30). Molecular typing was performed by spa-typing and pulsed field gel electrophoresis (PFGE).

Results:

The 1114 MRSA belonged to 64 different spa-types, from which 49 were detected at the UMC and 31 at the CCM. More than 50 % of all spa-types in both clinics were sporadic and only 8 spa-types at the UMC and 6 at the CCM reached percentages over 1 % of the whole sample size. The percentages of those highly presented spa-types in both hospitals are very similar, eg spa-type t003 occurred with a frequency of 74-78 % and t032 with 4-6 %, respectively. PFGE could sub-divide the dominant t003 MRSA into 34 subgroups with different restriction patterns. 6 out of those 34 subgroups were constantly present through the whole examination period. The caMRSA ratio at the UMC was about 6 %, and although spa-type t008 reached percentages over 2 % (17 isolates) at this hospital, only 9 of them could be classified as USA300 caMRSA. Other detected caMRSA strains belonged to spa-types t019 and t044.   

Conclusion:

Overall, the spa-typing results showed a high genetic diversity amongst the 1114 MRSA isolates. On the other hand, a certain spa-type (t003) dominates with over 70 % in both hospitals. PFGE typing demonstrated with 34 subgroups the enormous diversity of this strain. Because of the same high proportions in both hospitals it can be supposed that t003 strain has spread outside the clinics. Regarding caMRSA there is a  low and stable rate during the five years of examination and no indication for displacing haMRSA in hospitals.

Heike Suess, MSc, Wolfgang Kohnen, PhD and Bernd Jansen, MD, PhD, Department of Hygiene and Environmental Medicine, University Medical Center Mainz, Mainz, Germany

Disclosures:

H. Suess, None

W. Kohnen, None

B. Jansen, None

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