Culture conditions affect cytotoxin production by Serratia marcescens

Abstract

Cytotoxins have been implicated in the pathogenesis of bacterial infections. In this study, the influence of different culture conditions was evaluated on cytotoxin production of Serratia marcescens. Parameters such as culture media, incubation temperature, starting pH of culture medium, aeration, anaerobiosis, carbon sources, iron concentration in he culture media, and release of cell-bond toxin by polymyxin B were investigated. The data suggest that this cytotoxin is predominantly extracellular and is not induced by iron limitation. Aerobic culture with shaking resulted in higher cytotoxicity than static aerobic or anaerobic culture. Bacteria grown in glucose, sucrose or galactose were more cytotoxic than those grown in inositol or maltose. The culture conditions that were identified as optimal for cytotoxin production by Serratia marcescens were incubation temperature ranging from 30 to 37 degrees C, in medium adjusted pH 8.5, with shaking. This work will contribute to further studies on the identification of this cytotoxic activity.

Some like it hot: the effects of climate change on reproduction, immune function and disease resistance in the cricketGryllus texensis

“…Tanaka et al, 2004). Neither of the bacteria used here is thought to become less virulent with temperature (up to 37°C) [S. marcescens (Carbonell et al, 1996) B. cereus (Carlin et al, 2010)]. Although S. marcescens stops producing the red pigment prodigiosin and the biosurfactant serrawettin at 37°C (Tanaka et al, 2004), it increases its production of cytotoxic molecules from 18°C to a maximum at 37°C (Carbonell et al, 1996).…”

Characterization of a Cytotoxic Factor in Culture Filtrates of Serratia marcescens

“…In general, S. marcescens infections induce inflammation and fever, but fatal bacteremia can develop in patients weakened by previous infection, surgery, or immunosuppression (24,59,64,67). Despite numerous reported S. marcescens infections and the emergence of antibiotic-resistant strains (7,14,23,62), the virulence mechanisms of this organism are poorly understood.Carbonell and coworkers reported that S. marcescens culture filtrates exhibited pronounced in vitro cytotoxicity to cultured mammalian cells (11,12). Importantly, cytotoxicity was detected to various extents in all the strains that were tested, regardless of biotype or serotype (12).…”

Biological activity of Serratia marcescens cytotoxin

“…The cytotoxicity assays were performed as described in Ref. 6. Briefly, after formation of a cell monolayer, the medium was removed from each well and replaced with fresh medium without serum and containing the cytotoxin.…”

“…In order to compare the sensitivities of the cell lines to S. marcescens cytotoxin, cell viability after the cytotoxic assay was quantified by the neutral red cytotoxicity assay (6). The concentration of toxin that killed 50% of CHO cells (CD 50 ) was calculated as described in Ref.…”

“…Moreover, this cytotoxic activity is not mediated by plasmids. The S. marcescens toxin is extracellular and heat labile, and optimal culture conditions were incubation at temperatures ranging from 30 to 37ºC for 24 h under shaking in medium adjusted to pH 8.5 (6).…”