Interactions entre Staphylococcus aureus et Pseudomonas aeruginosa dans des cultures in vitro et au cours d'infections expérimentales

Abstract

Staphylococcus aureus and Pseudomonas aeruginosa are often found in succession or in association in infections. To study experimentally their interactions, we have used systems of growth or survival of mixed cultures of both species in vitro in a semisynthetic medium and in vivo in the peritoneal cavity of mice. Conditions for maximum growth in vitro of both species in mixed cultures are about similar to those in pure culture when the pH is maintained between 6.0 and 7.3. The inhibition of S. aureus growth by some antimetabolites or antibiotics, e.g., 5-methyltryptophan and D-cycloserine, is antagonized in mixed cultures. Staphylococcus coagulase, DNase, and alpha toxin were present either in mixed cultures or after mixing pure culture supernatants of both species, but P. aeruginosa slime was not observed in these conditions. In vivo, the survival of S. aureus seemed greater in mixed infections with P. aeruginosa than in those with S. aureus alone. In our systems, S. aureus may have benefited from the presence of P. aeruginosa whereas the reverse was not observed. These observations on interbacterial ecology could help to explain the importance and the behavior of some species at the initiation of pyogenic infections, either their interactions or their selection.

Caractéristiques de l'accroissement de la résistance de la souris contre Pseudomonas aeruginosa provoqué par Staphylococcus aureus

“…Les conditions et I'evaluation de la croissance de S. aiireiis et de P. aeriigitlosn ont deja ete decrites (7,9).…”

Growth and enterotoxin B synthesis by Staphylococcus aureus S6 in associative growth with Pseudomonas aeruginosa

“…has been studied by several authors (6,10,17,18,20,21). Graves and Frazier (10) used microorganisms isolated from foods and studied interactions by spot-plate tests.…”

“…group stimulated the growth of S. aureus. De Repentigny et al (6) observed that the inhibitory effect of antimetabolites such as 5-methyltryptophan on the growth of S. aweus was relieved by Pseudomonas aeruginosa grown in association with S . aureus.…”