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Increased frequency of large R-plasmids in Klebsiella pneumoniae colonizing patients with spinal cord injury
J Z Montgomerie1, J F John, L M Atkins
1University of Southern California School of Medicine, Los Angeles.
Abstract:
From 1978 to 1988 strains of gentamicin-susceptible (Gms) and gentamicin-resistant (Gmr) 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 Gms and 14 Gmr), there were 23 different serotypes (two nontypable). Fourteen Gms as well as 14 Gmr strains displayed no common plasmid patterns, but all contained a large plasmid of 168-208 kb. Among the 14 Gmr 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.
Insights
Gentamicin-resistant Klebsiella pneumoniae strains spread large R-plasmids among spinal cord injury patients over ten years. These plasmids conferred multiple antibiotic resistances, suggesting a role in colonization.
Area of Science:
- Microbiology
- Genetics
- Epidemiology
Background:
- Klebsiella pneumoniae is an opportunistic pathogen.
- Antibiotic resistance is a growing public health concern.
- Patients with spinal cord injury (SCI) are susceptible to infections.
Purpose of the Study:
- To investigate the genetic basis of gentamicin resistance in Klebsiella pneumoniae strains from SCI patients.
- To determine plasmid patterns and antibiotic resistance profiles over a decade.
Main Methods:
- Collection of Klebsiella pneumoniae strains from SCI patients (1978-1988).
- Plasmid profiling, conjugation experiments, and antibiotic resistance testing.
- Restriction endonuclease digestion of plasmids.
Main Results:
- Multiple serotypes of Klebsiella pneumoniae were identified.
- All strains contained a large plasmid (168-208 kb).
- Nine gentamicin-resistant strains harbored conjugative plasmids conferring resistance to multiple antibiotics (ampicillin, chloramphenicol, gentamicin, piperacillin, trimethoprim-sulfamethoxazole, tetracycline, tobramycin).
Conclusions:
- Different large R-plasmids spread among multiple Klebsiella pneumoniae serotypes in SCI patients over ten years.
- These plasmids likely contribute to K. pneumoniae colonization in SCI patients.