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Incidence of exotoxin production by Pseudomonas species
Abstract:
Pseudomonas aeruginosa exotoxin A has been shown to catalyze the transfer of the adenosine 5'-diphosphate (ADP)-ribose moiety of nicotinamide adenine dinucleotide onto elongation factor 2, resulting in the inhibition of mammalian protein synthesis. The enzymatic activity (ADP-ribosyl [ADPR]-transferase) is thought to account for the toxicity of exotoxin A. The distribution of the expression of exotoxin A within Pseudomonas species was examined. Laboratory strains as well as clinical isolates of Pseudomonas aeruginosa were tested. The production of exotoxin A was determined by assaying for ADPR-transferase activity in dialyzed frozen (-20 degrees C) and thawed cell-free supernatants from 22-h cultures or in 10-fold-concentrated supernatants. In addition, toxin production was detected immunologically using a modified Elek test. Exotoxin A production was detected in approximately 90% of the 111 isolates of P. aeruginosa. In contrast, none of the other species of Pseudomonas examined produced exotoxin A detectable by either ADPR-transferase activity or immunological reactivity.
Insights
Pseudomonas aeruginosa exotoxin A, an ADP-ribosyltransferase, inhibits protein synthesis. This study found exotoxin A production in 90% of P. aeruginosa isolates but not in other Pseudomonas species.
Area of Science:
- Microbiology
- Molecular Biology
- Toxicology
Background:
- Pseudomonas aeruginosa exotoxin A inhibits mammalian protein synthesis by ADP-ribosylating elongation factor 2.
- The enzyme's ADP-ribosyltransferase activity is linked to exotoxin A's toxicity.
Purpose of the Study:
- To investigate the prevalence of exotoxin A expression across different Pseudomonas species.
- To determine the extent of exotoxin A production in clinical and laboratory isolates of P. aeruginosa.
Main Methods:
- Assessed ADP-ribosyltransferase activity in cell-free supernatants of Pseudomonas cultures.
- Utilized a modified Elek test for immunological detection of exotoxin A.
- Tested 111 isolates of P. aeruginosa and other Pseudomonas species.
Main Results:
- Exotoxin A production was detected in approximately 90% of the P. aeruginosa isolates tested.
- No detectable exotoxin A production was observed in other examined Pseudomonas species using either enzymatic or immunological assays.
Conclusions:
- The majority of P. aeruginosa isolates express exotoxin A, contributing to its role as a significant virulence factor.
- Exotoxin A production appears to be specific to P. aeruginosa among the tested Pseudomonas species.