, 2011). In our study, amino acid sequence analysis revealed the presence of different A. baumannii NU7441 PilA groups (Fig. 3). The isolates within these PilA groups were clonally related and exhibited the same motility characteristics, e.g. the international clone I isolates shared a highly similar PilA amino acid sequence and all exhibited a twitching phenotype. Interestingly, the PilA sequences from other motile bacterial species clustered with PilA from the motile A. baumannii isolates, e.g. the P. aeruginosa and D. nodosus PilA shared the highest homology levels with PilA from international clone I isolates

and X. fastidiosa PilA with that from ATCC strain 17978. Linking adherence phenotypes to genotypes was also attempted, as multiple adherence mechanisms have been identified. Although Bap (Loehfelm et al., 2008) showed major sequence variation, no direct link between adherence characteristics and sequence homology could be established. The pgaABCD cluster responsible for production of poly-beta-1-6-N-acetylglucosamine (Choi et al., 2009), and ompA (Gaddy et al., 2009) displayed a high level

of conservation between NVP-BKM120 chemical structure the investigated strains, therefore, sequence differences that may be linked to a phenotype could not be observed. In total, four different type I pili clusters were identified in the six sequenced strains included in this study; AB57_1744-1747, AB57_2565-2570 (csu cluster) (Tomaras et al., 2003), AB57_2420-2423 and AB57_2003-2007. The csu gene cluster was well conserved between the strains investigated; however, csuB of ATCC 17978 contained a single base-pair (bp) insertion, which resulted in a truncation Progesterone of the open reading frame. Subsequently, the gap between the csuB and csuC open reading frames increased from 5 bp to 96 bp. Although transcription is unlikely to

be influenced by the single bp insertion, the increase between csuB and csuC may affect translation of csuC and other downstream genes in this operon. Interestingly, this strain showed the lowest level of binding to abiotic surfaces of all A. baumannii strains investigated, with the exception of strain RB02c (Fig. 1). The first open reading frame of the AB57_1744-1747 and AB57_2420-2423 polycistronic gene clusters contained homopolymeric tracts of varying lengths, and were therefore reanalysed by Sanger sequencing. Sequence differences were rebutted for AB57_1744_1747 using Sanger sequencing, however, strains ATCC 17978 and ATCC 19606 appeared to have an additional thymine in AB57_2423, which resulted in a frame-shift. However, even with this additional information, no direct correlation could be determined between the presence of type I pili clusters AB57_1744-1747, AB57_2420-2423 or AB57_2003-2007 and adherence to either biotic or abiotic surfaces. The Australian clinical A. baumannii isolates showed a similar clonal distribution to that found in Europe, viz.