Abstract
Following the release of biotechnology agents, detection methods for monitoring human exposure to these microorganisms should be available. Enzymatic markers from chromosomal ( lacZY ) and plasmid ( xylE ) DNA were evaluated in an in vivo mouse model. Mice were treated orally or intranasally with Pseudomonas aureofaciens 3732RN-L11 (lacZY), 3732RN-L11::pRO1940 ( lacZY xylE ), or ATCC 13985. All strains were cleared within 5 days from the cecum or lungs. Direct plating, without intermediate antibiotic resistance selection, was used to detect the genetic markers. Chromosomal-linked lacZ was stable in vivo and in vitro but plasmid-linked xylE was not. Of the isolates recovered, 75% ( in vivo, oral), 98% ( in vivo, intranasal), and 16% ( in vitro ) remained XyIE +. Though more tedious to enumerate, both lacZY and xylE are plausible alternatives to antibiotic resistance markers for in vivo biotechnology risk assessment studies.