Epidemiological fingerprinting of Enterobacter cloacae by small-fragment restriction endonuclease analysis and pulsed-field gel electrophoresis of genomic restriction fragments

Abstract

A cluster of infections caused by Enterobacter cloacae was observed among preterm neonates in a neonatal intensive care unit (NICU) of a pediatric hospital in Osnabruck, Germany. The presence of similar antimicrobial susceptibility patterns among the bacterial isolates prompted an investigation to determine whether a limited spread of a single strain existed. All 12 E. cloacae isolates from the NICU and 50 nonrelated strains were fingerprinted by small-fragment restriction endonuclease analysis (SF-REA) of EcoRI DNA digests. Selected isolates were further characterized by pulsed-field gel electrophoresis (PFGE) of NotIor XMaI-generated genomic restriction fragments. Epidemiologically unrelated strains were clearly discriminated by both methods. Results achieved by SF-REA and PFGE revealed that of the 12 isolates from the NICU, 11 belonged to the same genotypic cluster. Since all reagents and equipment for both techniques are commercially available, DNA fingerprinting by SF-REA or PFGE is proposed as a useful tool in the microbiology laboratory for investigating the epidemiological relatedness of E. cloacae strains of clinical and environmental origin. * Corresponding author. gel electrophoresis (PFGE) as typing tools for E. cloacae. The results are compared with those achieved by traditional methods available in a routine microbiology laboratory and are evaluated with respect to typeability, reproducibility, discriminatory power, and ease of use.

Characterisation and molecular typing of Burkholderia pseudomallei: Are disease presentations of melioidosis clonally related?

“…Several studies have compared di¡erent typing methods for Listeria monocytogenes [15], Enterobacter cloacae [16] and Neisseria meningitidis [17]. The investigators carrying out these studies have differed in their opinion of which particular typing method is the more discriminatory.…”

Typing of strains from a single-source outbreak of Pseudomonas pickettii

“…Although plasmid typing is straightforward to perform, the results are often inconsistent and unreliable (11,16,31). Plasmid detection is dependent upon the method employed, and special procedures to detect large pseudomonal plasmids may be required.…”

“…Linear electrophoresis of genomic DNA digested with frequent-cutting restriction endonucleases has been shown to differentiate strains, but analytical difficulties due to the generation of large numbers of fragments can arise (16). There is evidence that for some closely related strains, differences may be limited to larger genomic fragments and consequently, unless digestion is complete, these differences may be missed and strains may be erroneously presumed identical.…”

“…Preparation of chromosomal DNA for aqueous analysis subjects the DNA to unavoidable shearing forces, which may result in smearing during linear resolution. PFGE has been shown to be a sensitive and reproducible means of differentiating DNA fragments from closely related bacterial strains (16,28). The use of two infrequent-cutting enzymes enhances the technique.…”

“…The use of two infrequent-cutting enzymes enhances the technique. By this method, 16 of the 20 isolates tested had identical genomic DNA restriction profiles and were biotype 1 by OFBM. Four strains had different profiles.…”