A NEW FIMBRIAL ANTIGEN HARBORED BY CAZ-5 SHV-4-PRODUCING KLEBSIELLA-PNEUMONIAE STRAINS INVOLVED IN NOSOCOMIAL INFECTIONS/

We purified and characterized a new fimbria termed KPF-28 (Klebsiella pneumoniae fimbria with a fimbrin molecular mass of 28 kDa) involved i n K. pneumoniae adherence to the human carcinoma cell line Caco-2. Ele ctron microscopy of bacterial surface protein preparations and immunog old labeling of bacterial cells showed that KPF-28 was a long, thin, a nd flexible fimbria about 4 to 5 nm in diameter and 0.5 to 2 mu m long . The N-terminal amino acid sequence of the KPF-28 major fimbrial subu nit showed no homology with type 1 and type 3 pili of K. pneumoniae bu t showed 61.7% identity with residues 6 to 19 of the N-terminal amino acid sequence of PapA, the Pap major pilus subunit expressed by uropat hogenic Escherichia coli strains, Total amino acid content determinati on showed that the KPF-28 major subunit composition was close to that of the GVVPQ fimbrial family major subunits expressed by pathogenic E, coli strains, The study of the prevalence of KPF-28 among K. pneumoni ae strains involved in nosocomial infections revealed that KPF-28 was found in the great majority of the K. pneumoniae strains producing the CAZ-5/SHV-4 extended-spectrum beta-lactamase, As shown by curing and mating experiments, the R plasmid encoding the CAZ-5/SHV-4 enzyme was found to be involved in but not solely responsible for KPF-28 expressi on. Hybridization experiments using an oligonucleotide probe correspon ding to the N-terminal part of the 28-kDa protein revealed that the st ructural gene encoding the KPF-28 major subunit was localized on this R plasmid, KPF-28 is a putative colonization factor of the human gut, since the ceftazidine-sensitive derivative strain CF914-1C no longer a dhered and since the Fab fragments of antibodies raised against KPF-28 inhibited adhesion of K. pneumoniae CF914-1 to the Caco-2 cell line.