Characterization of nosocomial strains of Enterobacter aerogenes by arbitrarily primed-PCR analysis and ribotyping

To study the spread of strains of Enterobacter aerogenes in our hospital in 1992 and 1993 by using two genotypic markers, and to evaluate these methods for the epidemiological investigation of this species.

Ribotyping (using two endonucleases) and arbitrarily primed (AP)-PCR (using two different 10-mer primers) were applied to the epidemiological typing of clinical strains of E aerogenes isolated from hospitalized patients.

The intensive care unit (ICU; 5 patients, 13 isolates), nephrology units (3 patients, 5 isolates), and surgery units (2 patients, 2 isolates) of the university hospital of Saint-Etienne (France).

Eight epidemiologically unrelated isolates, chosen as controls, exhibited distinct profiles, both by AP-PCR and ribotyping. Two clones of E aerogenes circulated in the ICU; both were isolated successively from samples of a single patient who stayed in the unit for almost 1 year. A third clone was recovered from patients of surgery units. A fourth clone was shown to have infected patients of nephrology units.

Ribotyping and AP-PCR appear to be reliable methods for typing E aerogenes strains implicated in nosocomial infection. The spread of independent clones of E aerogenes in different units of our hospital in 1992 and 1993 was demonstrated by both methods. This study emphasizes the need to choose the endonucleases or primers with care to obtain high discriminatory results in genotypic investigations.