Listeria monocytogenes infection of Caco-2 cells: role of growth temperature

Modulation of actA gene expression in Listeria monocytogenes by iron

“…The clinical isolate of L. monocytogenes LM1 used in this study was a haemolytic, wild-type strain capable of invading and multiplying in Caco-2 and HeLa cells, similar to L. monocytogenes ATCC 7644 [19]. Iron limitation (Fe 3 , 1 ìM) was achieved by culturing bacteria in low iron medium (LIM) Brain Heart Infusion (BHI; Merck) plus Chelex-100 [10] and with 100 ìM ethylenediamine-di-o-hydroxyphenylacetic acid (EDDHA).…”

“…After incubation for a further 48 h, iron content was lowered from 125 pM to 18 pM=10 6 Caco-2 cells, as determined by measurement in cytosolic fractions with an atomic adsorption spectrophotometer with a minor modi®ca-tion of the procedure described by Mikogami et al [21]. Invasion assays of iron-depleted or iron-loaded Caco-2 cells were performed as described previously [19], at an infective dose of c. 100 log-phase bacteria=cell. After incubation for 1 h at 378C, infected monolayers were washed ®ve times in MEM, and 1 ml of fresh medium containing gentamicin 5ìg=ml was added to each well.…”

“…After incubation for a further 1 h at 378C, the cells were lysed by the addition of cold Triton X-100 0.1% and plated to determine the number of viable intracellular bacteria. The intracellular replication of L. monocytogenes in iron-depleted or iron-loaded Caco-2 cells was determined according to the method of Conte et al [19].…”

Natural milk fatty acids affect survival and invasiveness of Listeria monocytogenes

“…Semi-confluent monolayers, grown in 24-well plates without antibiotics, were infected with 0·5 ml bacterial suspensions in logarithmic phase at a multiplicity of infection of 100 bacteria per cell (Conte et al 1994). The infection was carried out for 60 min at 37°C in the presence or absence of the fatty acids dissolved in minimal essential medium (MEM) pH 7·2.…”

“…Recently, outbreaks of gastroenteritis and fever caused by the ingestion of L. monocytogenes-contaminated milk have been described (Dalton et al 1997;Schlech 1997). The occurrence and pathogenicity of the bacterium in milk and dairy products is guaranteed by its ability to survive and to invade at low and high temperatures and at low pH (Ryser et al 1985;Faber and Peterkin 1991;Leimeister-Watchter et al 1992;Conte et al 1994).…”