pneumoniae, 19 undefined Klebsiella spp., 18 K. oxytoca, one K. ornithinolytica and one K. planticola) isolated from distinct sources were PCR screened for fim2K using primers PR615-PR616. In total, 21 out of 162 strains (13.0%) were identified to be fim2 positive, including 16 K. pneumoniae (16/123 = 13.0%), LY333531 nmr three undefined Klebsiella spp. (3/19 = 15.7%) and two K. oxytoca (2/18 = 11.1%). It must be noted that these species designations are based on biochemical species identifications, which can be problematic in this genus [33]. 93.4% (15/16) of fim2-positive K. pneumoniae strains were also found to

be mrk- and fim-positive by PCR analysis. However, the distribution of the latter were not investigated in other Klebsiella spp. due to recognized species-specific differences in fim and mrk operon sequences [34]. Further examination

suggested that the specimen type from which strains were obtained was not a predictor of the presence or absence of fim2 (Table 2). Notably, fim2-positive strains were not limited to one geographical area. KR116, the index fim2-positive strain, was isolated in the United Kingdom, while other find more fim2-bearing strains were isolated in Germany, Denmark, USA and China, suggesting a sporadic but global spread of the fim2 locus. Table 2 Prevalence of fim2 by specimen type   Totala fim2+b Percentagec Ascitic fluid 9 1 11.1% Biliary fluid 1 0 0% Blood 48 8 16.7% Cerebrospinal fluid 2 0 0% Environmental 11 1 9.0% Pyogenic liver abscess aspirates 11 0 0% Nasopharynx 3 0 0% Sputum 11 1 9.0% Unknown 20 4 20.0% Urine 45 5 11.1% Wound 1 1 100% All 162 21 13.0% a Total number of strains tested. b Total number of strains testing fim2-positive using primers PR615 and PR616. c Percentage of fim2-positive strains. Fim2 genes are expressed under standard in vitro growth conditions Many chaperone/usher operons are poorly expressed under laboratory conditions [35, 36]. To investigate fim2 expression, RNA was isolated from

KR2107, a streptomycin-resistant derivative of KR116, which had been cultured in LB medium for 16 h (37°C, 200 rpm) and a cDNA library constructed using random primer-based RT-PCR. Subsequent PCR analysis of this cDNA Tryptophan synthase library detected transcripts that corresponded to fim2A fim2H and fim2K, while reverse transcriptase-free Selleck GW786034 control reaction mixtures did not yield any products, thus confirming absence of DNA carryover (Figure 2). Follow-up quantitative-PCR experiments on this KR2107 cDNA library showed that under the growth conditions examined fim2A was expressed approximately 30- and 90-fold less than fimA and mrkA, respectively (data not shown). As PCR analysis spanning orf10 to fim2A did not yield a product, whilst that linking fim2H to fim2K produced a specific band, it would appear that the eight gene fim2 cluster was expressed as a single transcript and that orf10 gene was not part of this transcriptional unit (Figure 2).