Introduction: Pseudomonas aeruginosa

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In 1882, Carle Gessard (1850-1925) first isolated Pseudomonas aeruginosa¹ from wound infections of soldiers whose bandages had a blue and green color. Walter Migula (1863-1938) first proposed the genus Pseudomonas in 1894 to encompass all gram-negative, rod-shaped aerobic bacilli that had polar flagella. Because this definition was so broad, unrelated organisms were added to the genus to the point that in 1984, there were over 100 species of Pseudomonas listed in Bergey's Manual of Systematic Bacteriology.^2,3 When molecular-based methods were developed that involved sequencing and comparing 16S ribosomal RNA from all of these organisms, scientists were able to reassign many organisms originally classified as Pseudomonas into other genera. First, rRNA-DNA hybridization studies described by Palleroni⁴ divided the genus into five groups called rRNA Groups I-V. Over the last 30 years, members of rRNA Groups II-V have been all moved to different genera such as Burkholderia, Ralstonia, Acidovorax, and Brevundimonas.³ The only remaining species of Pseudomonas are members of rRNA Group I and are divided into the following eight groups: P. aeruginosa, P. chlororaphis, P. fluorescens, P. pertucinogena, P. putida, P. stutzeri, P. syringae and incertae sedis, which is Latin for uncertain placement.

P. aeruginosa is a common organism in the soil and in water and it can also be found on plants and animals. It is an aerobic, saccharolytic, non-spore forming gram-negative bacillus measuring 0.5 to 0.8 μm by 1.5 to 3.0 μm.⁵ Most strains of P. aeruginosa possess a single polar flagellum that is used for motility. Pseudomonas aeruginosa…

ABBREVIATIONS: RNA = ribonucleic acid; rRNA = ribosomal ribonucleic acid