Isolation and characterization of attenuated strains of {\it Pseudomonas aeruginosa\/} AC869 and PAO1
Abstract
Pseudomonas aeruginosa AC869, a 3,5-dichlorobenzoate degrader, is a mouse pathogen and has a reported LD$\sb{50}$ of 1.05 x 10$\sp7$ CFU when given intranasally to C3H/HeJ mice. LPS extracted from cells of AC869 grown in mouse cecal and lung mucus was typed as O6 while that from Luria broth was nontypable. Pseudomonas aeruginosa PAO1, a clinical isolate, expresses O5, O2, and A-band LPS when grown in Luria broth, mouse cecal mucus and mouse lung mucus, and it has a reported LD$\sb{50}$ of 1.02 x 10$\sp7$ CFU when given intranasally to C3H/HeJ mice. Less virulent mutants, AC869-11 and PAO1-C1, were isolated from their parent strains using phage E79 which adsorbs to the O-side chain of LPS. The mutants produced much less exoenzyme S and were more sensitive to a number of antibiotics when grown either in Luria broth or mouse lung mucus relative to their respective parent strains. Strain AC869-11 produced less protease, less O-side chain on B-band LPS and less A-band LPS than AC869 while strain PAO1-C1 expressed more protease than PAO1 but did not express any O5 on B-band LPS and less A-band LPS. It appears possible that in the case of AC869 a regulator controls the synthesis or secretion of a series of virulence factors including O-side chain, exoenzyme S, protease, and resistance to antibiotics, whereas in the case of PAO1 a similar regulator which appears to control the synthesis of O5, A-band LPS, exoenzyme S, protease, and the sensitivity to a number of antibiotics that is mutant in PAO1-C1. A mouse model was used to examine health effects following pulmonary exposure to Pseudomonas aeruginosa AC869-1 1 and PAO1-C1, and their parent strains. The LD$\rm \sb{50s}$ (50% lethal doses of strain AC869, AC869-11, and PAO1, PAO1-C1 after intranasal administration are 1.91 x 10$\sp8$, 1.55 x 10$\sp9$, 1 x 10$\sp8$ and 2.21 x 10$\sp8$ CFU, respectively, in CD-1 mice. Animals were challenged intranasally with a sublethal dose of microorganisms and clearance rates from the lungs, large intestines, small intestines, ceca, liver, spleen, and mesentric lymphnodes (MLN) were determined. After administration, the clearance rates of AC869-11 and PAO1-C1 from the organs were much faster than that of their parents. Moreover, P. aeruginosa AC869 and PAO1 elicited a relatively stronger inflammatory response than their mutant strains. This study indicates that upon intranasal exposure P. aeruginosa AC869-11 and PAO1-C1 have much less potential to induce adverse health effects in mice, as shown by organ clearance and the pulmonary inflammatory response. ^
Subject Area
Biology, Microbiology
Recommended Citation
Xin Zhou,
"Isolation and characterization of attenuated strains of {\it Pseudomonas aeruginosa\/} AC869 and PAO1"
(1995).
Dissertations and Master's Theses (Campus Access).
Paper AAI9608902.
http://digitalcommons.uri.edu/dissertations/AAI9608902