Common Plasmid Specifying Tobramycin Resistance Found in Two Enteric Bacteria Isolated from Burn Patients

Abstract

Tobramycin-resistant burn wound isolates of Klebsiella pneumoniae and Enterobacter cloacae, together with Escherichia coli K-12 transconjugants from these two strains, were examined for plasmid deoxyribonucleic acid (DNA). All the resistant strains contained a common, high-molecular-weight, covalently closed circular DNA plasmid that was absent in the tobramycin-susceptible E. coli recipient strain. The common plasmid residing inELctocae was designated pIE098, and that residing in _..neumatie was designated pIE099. Both plasmid species were found to have a molecular mass of approximately 60 x 106 daltons and a guanine-plus-cytosine content of 50 mol%. The DNA that was extracted from all of the tobramycin-resistant strains tested was able to hybridize to 86 to 100% with pIE098 and pIE099 [3H]DNA generated by EcoRI to produce fragments of a size similar to those generated by BamHI. This study illustrates the) usefulness of simple screening methods for antibiotic resistance plasmids in a( hospital epidemiological situation.Infections caused by gram-negative bacilli currently constitute the most frequent type of nosocomial infection, a fact that has profound implications for patients with major burns. A serious threat to the control of burn wound infections has been the emergence of bacteria harboring transmissible antibiotic resistance plasmids (R plasmids) that are selected for under the pressure of intense antibiotic therapy (13,15,23,25). Minshew et al. (19) have reported the isolation of tobramycin-resistant strains of Klebsiella pneumoniae and Escherichia coli from burn patients undergoing tobramycin therapy. Tobramycin resistance in the Klebsiella and Enterobacter isolates could be transferred to E. coli recipients and was associated with the enzymatic acetylation of tobramycin and other aminoglycosides. The acetylating activities of these strains were found to resemble kanamycin acetyltransferase or an aminoglycoside-6'-acetyltransferase (9).This study reports the isolation and partial characterization of a common, self-transmissible R plasmid specifying tobramycin resistance in the Klebsiella and Enterobacter strains. The presence of a similar plasmid in these two enterobacteria indicates the probability of R-plasmid t Present address: Wenlcome Research Laboratories, Research Triangle Park, NC 27709.tt Present address:

Physical Characterization of Ten R Plasmids Obtained from an Outbreak of Nosocomial Klebsiella pneumoniae Infections

“…However, this technique has seen very limited use in the examination of R plasmids of clinical significance (9, 11). Elwell et al have employed restriction endonucleases to show identity between two plasmids isolated from two different enteric bacteria isolated from burn patients (9). In a more extensive study, Grinter and Barth compared the restriction endonuclease patterns of 12 epidemiologically unrelated plasmids specifying resistance to streptomycin and sulfonamide (11).…”

Dissemination of an antibiotic resistance plasmid in hospital patient flora

“…Purified plasmid DNA was digested with EcoRI (New England Biolabs, Beverly, Mass.) in a reaction mixture containing 7 The sequence of appearance of gentamicinresistant Enterobacteriaceae is shown in Fig. 3.…”

Use of plasmid profiles in epidemiologic surveillance of disease outbreaks and in tracing the transmission of antibiotic resistance

“…N. gonorrhoeae strains that carry plasmids mediating penicillin or tetracycline resistance have been isolated from patients. Different plasmids which encode a TEM betalactamase, conferring penicillin resistance, have been described (54,67,154,199). All of the beta-lactamase-producing plasmids are related to one another (67,178,199).…”