Induction of apoptosis of the host cells has been considered to be a putative virulence mechanism that may cause CC-5013 tissue damage and facilitate further colonization [5].S. marcescens strains associated with hospital outbreaks are mostly nonpigmented [2]. Despite considerable clinical data regarding their role in nosocomial infections, the pathogenic mechanism has not been elucidated. In this study we evaluated interactions between nonpigmented strains and human erythrocytes, epithelial cells, and murine macrophages originating from a well-established cell line, J774. 2. Materials and Methods2.1. Bacterial StrainsA total of 30 strains identified as Serratia marcescens by biochemical test kit API20E (bioM��rieux) were used in this study.

These strains were isolated from various specimens of hospitalized patients: 9 from urine (MPU S3, 12, 18, 21, 30, 33, 35, 36, and 37), 5 from postoperative wounds (MPU S6, 11, 26, 27, and 29) and 5 from ulcerations (MPU S1, 4, 7, 23, 42), 5 from secretions: aspirate, a conjunctival sac, and pus; from the pharynx, ear and drain (MPU S2, 28, 5, 14, and 13), 3 from intubation tubes (MPU S31, 34, and 41), and 1 from blood (MPU S22), stool (MPU S15), and a catheter (MPU S20). The isolates were maintained at ?75��C in trypticase soy broth (TSB, Difco) containing 50% (vol/vol) glycerol. The HEp-2 and J774 monolayers were infected separately with an E. coli K-12 C600 strain as the negative control.2.2. Cell CultureThe murine macrophage cell line, J774, was maintained in a growth medium (GM), containing RPMI 1640 (Biomed, Poland) supplemented with 10% heat-inactivated fetal calf serum (FCS, Gibco), gentamicin (5mgmL?1), and 2mM L-glutamine (Sigma).

Human laryngeal epithelial cells (HEp-2) were cultured in a growth medium (GM), including the Minimum Essential Medium Eagle (MEM, Biomed) supplemented with 5% fetal calf serum, 2mM glutamine, 80IU penicillin per mL, 80��g streptomycin, and 1mgmL?1 of nystatin. The cells were seeded with 100mL of suspension in number of 2 �� 106/mL and incubated at 37��C in an atmosphere with 5% CO2 [6�C8].2.3. Infection ConditionsFor each experiment, HEp-2 and J774 cells at the concentration of 2 �� 106/mL were seeded into 96-well plates (Nunc) and allowed to attach overnight. The strains were cultivated on Luria-Bertani agar (LB, Difco), harvested and resuspended in PBS to 1 on the McFarland scale, and diluted 1:100 in GM Dacomitinib to a number of approximately 2 �� 107/mL. The aliquots were diluted in PBS and viable bacteria quantified.