Typing and Subtyping of 83 Clinical Isolates Purified from Surgically Implanted Silicone Feeding Tubes by Random Amplified Polymorphic DNA Amplification

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Abstract
In this study, 83 clinical isolates purified from biofilms colonizing 18 silicone gastrostomy devices (12 “buttons” and six tubes converted to skin level devices) were selected for subtype characterization utilizing genetic analysis. The tubes, previously used for feeding, remained in place for 3 to 47 months (mean, 20.0 months) in children ranging in age from 6 months to 17 years. Classification of specific microbes using random amplified polymorphic DNA (RAPD) analysis revealed genetic similarities and differences among isolates belonging to the same genus. Both gram-positive and -negative bacteria were investigated, including 2 isolates of Bacillus brevis, 4 isolates of Bacillus licheniformis , 2 isolates of Bacillus pumilus , 3 isolates of Enterococcus durans , 19 isolates of Enterococcus faecalis , 8 isolates of Enterococcus faecium , 2 isolates of Enterococcus hirae , 7 isolates of Escherichia coli , 8 isolates of Lactobacillus plantarum , 19 isolates of Staphylococcus aureus , 2 isolates of Staphylococcus epidermidis , and 7 isolates of Staphylococcus saprophyticus. Amplified DNA fragments (amplicons) provided species-specific fingerprints for comparison by agarose gel electrophoresis. A total of 62 distinct RAPD types were categorized from the five genera studied. Typing analysis suggested cross acquisition of E. coli , E. faecalis , and S. aureus in three patient pairs. Genomic polymorphism detection proved efficient and reliable for classifying bacterial subtypes isolated from biofilms adhering to various portions of commonly employed enteral access tubes.