Molecular typing of Enterobacter cloacae by pulsed-field gel electrophoresis of genomic restriction fragments.

Eleven multiply resistant Enterobacter cloacae isolates were obtained from eight preterm neonates in a neonatal intensive care unit (NICU) of one hospital in Osnabrück, together with one sensitive strain from another infant. The presence of similar antibiograms and biotypes in 11 isolates prompted further characterization of the isolates by pulsed-field gel electrophoresis (PFGE) of NotI generated genomic restriction fragments. For assessment of the discriminatory power of this typing method 50 non-related strains were included in the study. Non-related strains demonstrated a marked variation in restriction fragment patterns and were clearly discriminated one from another. In contrast, 11 of 12 isolates from the NICU exhibited identical restriction profiles, indicating a cluster associated with nosocomial infection. Since the discriminatory power of PFGE is high, reproducibility is good, and all reagents and equipment for DNA fingerprinting are commercially available, this technique is proposed as a useful tool in the microbiology laboratory for investigating the epidemiology of E. cloacae strains.