Survival and growth of Stenotrophomonas maltophilia in free-living amoebae (FLA) and bacterial virulence properties

Abstract

Stenotrophomonas maltophilia is found ubiquitously in the environment and is an important emerging nosocomial pathogen. S. maltophilia has been recently described as an Amoebae-Resistant Bacteria (ARB) that exists as part of the microbiome of various free-living amoebae (FLA) from waters. Co-culture approaches with Vermamoeba vermiformis demonstrated the ability of this bacterium to resist amoebal digestion. In the present study, we assessed the survival and growth of six environmental and one clinical S. maltophilia strains within two amoebal species: Acanthamoeba castellanii and Willaertia magna. We also evaluated bacterial virulence properties using the social amoeba Dictyostelium discoideum. A co-culture approach was carried out over 96 hours and the abundance of S. maltophilia cells was measured using quantitative PCR and culture approach. The presence of bacteria inside the amoeba was confirmed using confocal microscopy. Our results showed that some S. maltophilia strains were able to multiply within both amoebae and exhibited multiplication rates up to 17.5 and 1166 for A. castellanii and W. magna, respectively. In contrast, some strains were unable to multiply in either amoeba. Out of the six environmental S. maltophilia strains tested, one was found to be virulent. Surprisingly, this strain previously isolated from a soil amoeba, Micriamoeba, was unable to infect both amoebal species tested. We further performed an assay with a mutant strain of S. maltophilia BurA1 lacking the efflux pump ebyCAB gene and found the mutant to be more virulent and more efficient for intra-amoebal multiplication. Overall, the results obtained strongly indicated that free-living amoebae could be an important ecological niche for S. maltophilia.

Stenotrophomonas maltophilia Encodes a VirB/VirD4 Type IV Secretion System That Modulates Apoptosis in Human Cells and Promotes Competition against Heterologous Bacteria, Including Pseudomonas aeruginosa

“…Based upon the range of target cells utilized in this study, we strongly suspect that the S. maltophilia T4SS can modulate the death program of a wide range of cellular targets, including killing other mammalian cells that are part of the immune system (e.g., neutrophils) or other bacteria that inhabit its niches, whether planktonic in nature or coinfecting plant, animal, or human hosts. In regard to the proapoptotic effect that the K279a VirB/D4 T4SS has on macrophages, it is tempting to speculate that this function evolved as a result of S. maltophilia interacting with predatory protozoans (amoebae) in nature (113)(114)(115)(116)(117). Despite demonstrating the importance of the S. maltophilia T4SS in influ- encing the death of other cells, we do not believe that this is the only function of this VirB/D4 T4SS, given what is known about T4SS in general (35)(36)(37).…”

Persistence of Escherichia coli in the microbiomes of red Romaine lettuce (Lactuca sativa cv. ‘Outredgeous’) and mizuna mustard (Brassica rapa var. japonica) - does seed sanitization matter?

“…Previously classified as a pseudomonad, Stenotrophomonas has been isolated in soil, plant, water and human tissues. In soil and plants, it is known for production of plant hormones and is very persistent in the roots, and once established, is not easily out-competed [ 51 , 52 ].…”

Potential biofilm control strategies for extended spaceflight missions

“…While this concept is certainly appealing several issues must be considered. Some bacteria, notably Legionella pneumophila and Stenotrophomonas maltophila have evolved mechanisms to persist within amoeba and presumably other protozoa wherein they can gain access to nutrients within the amoeba cytoplasm while inhibiting the host cell enzymatic digestive processes [ 177 , 178 ]. Several investigators have examined biofilm susceptibility to protozoa and other bacteria-ingesting organisms in monoculture and polymicrobial settings (e.g.…”