Four novel mrkD alleles namely mrkD(V1), mrkD(V2), mrkD(V3), and mrkD(V4) were identified in seventeen Klebsiella pneuntoniae meningitis strains using PCR-RFLP and sequence determination. Comparative analysis revealed a most variable region containing an RGD motif in the receptor domain of MrkD(V3). In order to determine if the sequence confers the K pneumoniae mrkD(V3) the highest level of the fimbrial activity, a type 3 fimbriae display system was constructed in Escherichia coli. The E coli JM 109[pmrkABCD(V3)F] displaying meshwork-like fimbriae also had the most fimbrial activity, supporting a possible role of the varied sequences. In a dose-dependent manner, the GRGDSP hexapeptide appeared to inhibit the adhesion of the E. coli JM109[pmrkABCD(V3)F] to HCT-8, an ileocecal epithelial cell line. In addition, the adhesion activity was reduced by the addition of anti-alpha 5 beta 1 integrin monoclonal antibody, indicating that the RGD containing region in MrkD(V3) is responsible for the binding of type 3 fimbriae to integrin. (c) 2006 Elsevier Inc. All rights reserved.