Thus, despite the lack of cross-study comparison of ftsI DNA sequences, the examples above indicate that clonal distribution is a more likely explanation

for the occurrence of PBP3 type A and compatible selleck screening library patterns in separate studies from four continents [3, 4, 9, 11, 12, 16, 18, 20],[22–25] than independent development of this substitution pattern by convergence. Importantly, an invasive high-level resistant rPBP3 isolate with the same combination of MLST allelic profile (ST155) and PBP3 substitution pattern learn more as the two group III-like isolates in the present study was recently reported from Spain [24]. A single-locus variant (ST1118) with an identical substitution pattern was also reported. These observations are notable and support the need of global surveillance initiatives. We here show that combining MLST and PBP3 typing provides a tool for cross-study identification of rPBP3 strains and clones. The previously suggested system YM155 order for subgrouping of group II isolates [38] does not separate PBP3 types [11, 16] and is unsuitable for

this purpose. Preferably, MLST should be combined with ftsI DNA sequencing. The ftsI gene is nearly 200 kb from its nearest MLST neighbor (mdh) and distortion of the MLST results due to linkage is thus very unlikely. With recent technological development reducing both costs and analysis time of whole-genome sequencing, and smaller bench-top sequencers becoming readily available, MLST-ftsI typing will probably be possible to perform for surveillance purposes in the near future. We are aware of a number of previous studies where MLST and ftsI sequencing was performed [3, 4, 12, 23–25, 43–45]. To our knowledge, much four reports have linked MLST data and PBP3 substitution patterns: one presented the allelic profiles of 83 group III respiratory isolates from Japan [43]; another presented the substitution pattern of a single group II ST368 NTHi isolate causing meningitis in Italy [44]; and two most recent publications presented the substitution patterns and STs of 95 respiratory [25] and 18 invasive isolates [24] from Spain.

However, the present study is to our knowledge the first to connect STs to ftsI alleles. PFGE is highly discriminative and generally considered suited for assessment of relatedness between epidemiologically connected isolates, particularly in populations with high recombination rates such as NTHi [39, 46]. In this study, PFGE clusters correlated well to MLST clonal complexes. Band patterns were stable over time and also traced phylogenetic relationship not detected by MLST and parsimony analysis. Combining MLST and PFGE for typing of NTHi may thus increase both sensitivity and resolution of clone detection. Development of resistance As discussed above, clonal expansion is important for the spread of rPBP3. However, the PBP3 type A-encoding, highly divergent ftsI allele lambda-2 was distributed among several unrelated STs.