Isolation of Pseudomonas aeruginosa from Open Ocean and Comparison with Freshwater, Clinical, and Animal Isolates

Abstract

Pseudomonas aeruginosa is an opportunistic pathogen responsible for morbidity and mortality in humans, animals, and plants. This bacterium has been regarded to be widely present in terrestrial and freshwater environments, but not in open ocean environments. Our purpose was to clarify its presence in open ocean, and their genotypic and physiological characteristics were compared with those of isolates from clinical, animal, and freshwater sources. Water samples were collected from freshwater, bays, and offshore environments in Japan. Sixty-two isolates, including 26 from the open ocean, were identified as P. aeruginosa by phenotypic characteristics and the BD Phoenix System. Pulsed-field gel electrophoresis (PFGE) was performed on all strains, together with 21 clinical and 8 animal strains. The results showed that open ocean strains are composed of a few genotypes, which are separated from other strains. Although some clinical isolates made a cluster, other strains tended to mix together. Different antibiotypes were observed among marine isolates that had similar PFGE and serotyping patterns. Some were multidrug-resistant. Laboratory-based microcosm study were carried out to see the responses of P. aeruginosa toward increased NaCl concentrations in deionized water (DW). Marine strains showed better survival with the increase, whereas river and clinical strains were suppressed by the increase. These findings illustrate the potential significance of open ocean as a possible reservoir of P. aeruginosa, and there may be clones unique to this environment. To our knowledge, this is the first report on the presence and characterization of P. aeruginosa in the open ocean.

Culturability and Survival of Marine, Freshwater and Clinical Pseudomonas aeruginosa

“…Such isolates have been regarded as originating from freshwater or sewage (17,25). Our detailed study on marine P. aeruginosa demonstrated for the first time that this bacterium is common in the open ocean (22,23).…”

“…Strain 1030, a river strain, was isolated in 2003 from the uppermost reaches of the Arakawa River (22). Strains 100 and 1200 are marine strains, isolated from St. N7 and S2 during the KH-05-01 and KT-03-07 cruises of R/V Tansei Maru, Ocean Research Institute, the University of Tokyo and JAMSTEC (22,23). Human influence was considered minimal or absent at these sampling sites.…”

“…Human influence was considered minimal or absent at these sampling sites. Strain 1564 was isolated from a blood sample of a hospital patient from Tokyo, Japan, in 2002 (22). These four strains have different serotypes, antibiotypes and PFGE patterns ( Table 1).…”

“…Pseudomonas aeruginosa is present in the open ocean and marine strains with unique genotypes and forming distinct clusters were recently confirmed by multilocus sequence typing, pulsed field gel electrophoresis (PFGE) and phylogenetic analysis (22,23). In addition, the geographic distribution of these marine strains is related to their phylogenetic position (23).…”

Genotypic Analysis of Enterococci Isolated from Fecal-Polluted Water from Different Sources by Pulsed-Field Gel Electrophoresis (PFGE) for Application to Microbial Source Tracking

“…In addition, pathogenic bacteria with resistance to antibiotics have been detected in river water and coastal water and characterized using PFGE (6). PFGE has also been utilized for the source tracking of Salmonella contamination in marine environments (16) and for comparing genotypes of Pseudomonas aeruginosa collected from the ocean and freshwater (13). However, there have been few cases of PFGE being applied to the MST of fecal bacteria in urban and catchment areas.…”