Increased Frequency of Large R-Plasmids in Klebsiella pneumoniae Colonizing Patients with Spinal Cord Injury

Abstract From 1978 to 1988 strains of gentamicin-susceptible (Gm s ) and gentamicin-resistant (Gm r ) Klebsiella pneumoniae were saved from annual surveillance cultures of the perineal region of patients with spinal cord injury (SCI). Of 38 strains selected for further study (24 Gm s and 14 Gm r ), there were 23 different serotypes (two nontypable). Fourteen Gm s as well as 14 Gm r strains displayed no common plasmid patterns, but all contained a large plasmid of 168–208 kb. Among the 14 Gm r strains, nine had large conjugative plasmids of approximately the same size (166–193 kb), which conferred to a susceptible Escherichia coli host an identical resistance pattern: ampicillin, chloramphenicol, gentamicin, piperacillin, trimethoprim-sulfamethoxazole, tetracycline, and tobramycin. Of the nine transconjugants, eight contained a single plasmid. One transconjugant contained a 168-and 80-kb plasmid. Restriction endonuclease digestion patterns of the R-plasmids revealed minimal similarity. We conclude that, during a 10-year period, different large R-plasmids have spread among multiple serotypes of K. pneumoniae in spinal cord injury (SCI) patients in one rehabilitation hospital. We hypothesize that other genes located on large, R-, and non-R-plasmids may confer an additional advantage for colonization by K. pneumoniae in SCI patients.