Comparing the PFGE results using the criteria by selleck screening library Tenover et al. and when a buy Mocetinostat similarity cut-off of 80% was applied, most NT SmaI -MRSA isolates should be classified as one PFGE cluster [31, 32]. However, the Cfr9I PFGE is still better in discriminating possible differences between NT SmaI -MRSA isolates. No geographical relation
could be found in either spa-type. However, most NT SmaI -MRSA isolates are found in areas with the highest pig density. This could be explained by the frequent movement of pigs between farms in the Netherlands. This facilitates the dissemination of ST398 MRSA on a national scale. A similar situation took place during the foot- and -mouth epidemic in England of 2001 . To provide additional resolution on the molecular evolution and dissemination of MRSA lineages, several typing techniques such as PFGE, SCCmec- and spa-typing have been developed. Since PFGE with SmaI does not digest the DNA of ST398 isolates, spa-typing has been the method of choice for characterizing NT SmaI -MRSA isolates. However, given the low diversity in spa-types it is hard to ascertain health care-associated transmission if two or more different spa-types are present in the same institution. Fanoy et al. described an outbreak in a residential care facility where two spa-types (t2383 and t011) were prevalent . After re-examination
of the same isolates the PFGE profiles using Cfr9I were indistinguishable, indicating isogenicity. Moreover, the discriminatory ability of spa-typing of NT SmaI -MRSA is BMS202 molecular weight compromised by the fact that
more than 80% of the NT SmaI -MRSA in the Netherlands belong either to spa-type t011 or t108 . With the modified Cfr9I PFGE a better tool for epidemiological investigation has become available. The results obtained (-)-p-Bromotetramisole Oxalate by Cfr9I PFGE of isolates from veterinarians and their close family members showed possible transmission of ST398. Five out of eight pairs had identical profiles. The family members had themselves no contact with animals and were presumably infected by the occupationally exposed veterinarian. Two pairs of PFGE patterns among family members were not identical. Their isolates also had different spa-types. Family members may have been colonized by one MRSA through the veterinarian and subsequently the veterinarian may have been re-colonized by another MRSA after occupational exposure. One pair differed only in a single PFGE band probably as a consequence of micro-evolution. A study on nine different farms revealed that the PFGE patterns of isolates from seven farms were related, but PFGE patterns varied within and between the farms. For example, farm 7, yielded only 2 very closely related PFGE patterns (D14, D21; similarity 95%), while other farms, like farm 8, showed 5 different PFGE patterns (B1, D1, D3, D4 and K) and had a similarity of only 66%. Different batches of animals entering the farm, carrying different NT SmaI -MRSA, could have caused variation within farms.