992 for PFGE (0.989–0.996 95% CI); DI = 0.91 for AT (0.872–0.947 95% CI) and the global congruence between the typing methods was low (adjusted Rand coefficient = 0.077 (0.012–0.140 95% CI)). The displayed

greater discriminatory power of the PFGE technique compared to AT-typing AZD7762 was concordant with published data [18] and it is a consequence of the different definition of a clone on which these two techniques are based. PFGE/SpeI typing resolves isolates by their SpeI macrorestriction pattern, thus focusing on presence or absence of recognition sites for the selected genome-wide rare-cutter restriction endonuclease (around 36 SpeI sites on the reference P. aeruginosa PAO1 genome [20]). Differently, the ArrayTube genotyping is based on the knowledge of P. aeruginosa Bioactive Compound Library genome organization, and it recognizes presence or absence of 15 a priori well-known SNPs or gene markers (13 single nucleotide polymorphisms (SNPs) and 2 marker genes) [7]. Being the AT-markers less numerous than SpeI restriction sites and based solely on the PAO1-genome, they do not allow

to perform phylogenetic analyses. However, they are well suitable for epidemiological studies, since they are not affected by the genome SN-38 instability exhibited by some epidemic strains, which bias the discrimination power when routine methods are used [18]. For example, the isolates with genotype 4B9A, mostly

found in CF patients, were dispersed in 4 different PFGE clones (D, MM, QQ and UU) (see Additional file 3). Another example is represented Methamphetamine by genotype 6C22, comprising isolates from the same hospital (Verona) and even department (Hematology). According to the PFGE typing, they belonged to 2 different clones, HH and II although closely related (see Additional file 1). This example shows how the microarray typing, despite being less discriminative than PFGE provides a genotype definition which is particularly suitable for epidemiological studies. This finding is striking looking at isolates from the same patient. For example, 2 isolates from patient P54, presenting genotype 1BAE and identical virulence profile, were defined as the same epidemiological clone according to AT approach, but showed 2 different PFGE fingerprints. Besides the evaluation of the discriminatory power of AT versus PFGE typing, we tested whether there was concordance between clusters of clones defined by those techniques. Out of 4 AT clusters of clones identified, only the 3 small clusters had the at least 50% of the clones defined as part of the same cluster by both AT and PFGE (see Additional file 3). The isolates from the main AT cluster instead (including 66 isolates from 11 AT-genotypes) were spread over 19 different PFGE pulsotypes. MLST was also applied to a set of independent isolates (n = 80).