, 2008). However, no international clone III isolates were identified in this study. Since bacterial motility is a known virulence factor in numerous bacterial species (Han et al., 2008; Alarcon et al., 2009; Proft & Baker, 2009), the motility potential of our 52 clinical isolates was examined. The motility phenotypes in this study were determined using the general classifications for both swarming and twitching (Semmler et al.,

1999; Kaiser, 2007). Our data revealed that all international clone I isolates showed significant twitching. A number of other twitching isolates, not part of this clonal lineage, had the ability to form well developed biofilms compared to the international clone I isolates (see below), Selleck PLX3397 with the exception of A. baumannii strain D1279779. This relatively poor biofilm former (OD595 nm<1) also showed a small twitching zone (approximately 12 mm). Swarming motility was Fluorouracil observed in three noninternational clone isolates, including A. baumannii ATCC 17978, a fully sequenced reference strain. Studies using MH and LB media showed that twitching and swarming phenotypes are largely medium dependent. Furthermore, twitching and swarming

were demonstrated to be distinct characteristics, as many twitchers did not swarm, and A. baumannii strain ATCC 17978 swarmed, but did not twitch. PilA showed a high degree of amino acid sequence conservation within twitching isolates, indicating that type IV pili may play a role in motility in this species. Examination of biofilm formation showed that there was a significant difference between international clone

I and II isolates, correlating with previously published data (de Breij et al., 2010). We also found a significant difference (P < 0.05) between international clone I and noninternational clone isolates, indicating that in general international clone I isolates are limited in their ability to form biofilms. We determined the adherence of selected A. baumannii isolates to eukaryotic cells of nasopharyngeal (Detroit 562) and alveolar (A549) origin. Not only were significant differences observed between strains, two Glutamate dehydrogenase isolates, D1279779 and ATCC 17978, showed significantly lower adherence to nasopharyngeal cells compared to lung epithelial cells. Comparison of the ability to form biofilms and eukaryotic cell adherence revealed no relationship between these two phenotypes in the strains tested. This suggests that the mechanism of adherence to either abiotic or biotic surfaces appears to be different and draws a parallel with the results from other studies (Lee et al., 2008; de Breij et al., 2010). Moreover, previous studies have shown that adherence to abiotic surfaces is in part mediated by the csu type I pili cluster in strain ATCC 19606 (Tomaras et al., 2003), however, in a subsequent study using the same csu knockout strain, no difference was observed in the ability to bind bronchial cells (de Breij et al., 2009).