Staphylococcus aureus infection after splenectomy and splenic autotransplantation in BALB/c mice

Abstract

Splenectomy results in an increased risk of sepsis. The autogenous transplant of the spleen is an option for preserving splenic functions after total splenectomy. In this study, the capacity of animals undergoing autogenous spleen transplantation to respond to Staphylococcus aureus infection was investigated. BALB/c mice were divided into three groups: splenectomy followed by autotransplantation in the retroperitonium (AT), splenectomized only (SP) and operated non-splenectomized sham control (CT). Thirty days after surgery the mice were infected intravenously with S. aureus. Splenectomized mice had a higher number of colony-forming units (CFU) of S. aureus in liver and lungs in comparison with either AT or with CT mice (P < 0.05). Higher CFU numbers in lung of SP mice correlated with elevated production of interleukin-10 associated with a lower production of interferon-gamma and tumour necrosis factor-alpha. However, systemically, the level of tumour necrosis factor-alpha was higher in the SP group than in CT or AT. Lower titres of specific anti-S. aureus immunoglobulin (Ig)M and IgG1 were observed 6 days after infection in SP mice in comparison either with the AT or CT groups. Thus, splenectomy is detrimental to the immune response of BALB/c mice against infection by S. aureus which can be re-established by autogenous implantation of the spleen.

Fig. 1

Evidence that splenectomized BALB/c mice are more susceptible to Staphylococcus aureus infection and that splenic autotransplantation increases resistance to S. aureus. Groups of BALB/c mice were infected intravenously with 5 × 10⁶S. aureus 30 days after surgery. At day 6 post-infection, the number of colony-forming units per lung and liver was determined. Data represent means of six mice from a representative experiment. CT = control group (white bar), SP = splenectomized group (grey bar), AT = autotransplanted group (black bar). *P < 0·05 versus CT and AT groups.

Fig. 2

Myeloperoxidase (MPO) and N-acetylglucosaminidase (NAG) activity in lung homogenates and morphometric analysis of inflammatory infiltration in the lungs after Staphylococcus aureus infection. Neutrophil (a) and macrophage (b) accumulation in lungs was evaluated by indirect methods based on MPO and NAG activities respectively. Results represent the average of the optical density values of six infected (grey bar) and five non-infected (white bar) mice from a representative experiment. Photomicrograph showing inflammatory infiltration in lungs of S. aureus infected control (c), splenectomized (d) and autotransplanted (e) mice. The inflammatory infiltration area was measured as described previously. *P < 0·05 versus non-infected; #P < 0·05 versus control group. Bar = 100 µm.

Fig. 3

Effect of splenectomy on plasma levels of interferon (IFN)-γ, interleukin (IL)-10 and tumour necrosis factor (TNF)-α and on weight loss after Staphylococcus aureus infection. Groups of BALB/c mice were infected intravenously with 5 × 10⁶S. aureus 30 days after surgery. IFN-γ (a), IL-10 (b) and TNF-α (c) levels in plasma were evaluated at different times after infection by enzyme-linked immunosorbent assay. The body weights of infected mice were recorded before surgery (day –30), before infection (day 0) and at day 6 post-infection. Data represent means of six infected mice. *P < 0·05 versus CT and AT groups; #P < 0·05 versus SP.

Fig. 4

Effect of splenectomy on interferon (IFN)-γ, interleukin (IL)-10 and tumour necrosis factor (TNF)-α levels in lung and liver homogenates after Staphylococcus aureus infection. Mice were infected intravenously with 5 × 10⁶S. aureus 30 days after surgery. IFN-γ (a), TNF-α (b) and IL-10 (c) levels in lung and liver homogenates were evaluated at day 6 post-infection by enzyme-linked immunosorbent assay. Data represent means of six mice from a representative experiment. *P < 0·05 versus CT and AT groups; #P < 0·05 versus CT.

Fig. 5

Effect of splenectomy on serum levels of anti-Staphylococcus aureus immunoglobulin (Ig)M and IgG1 antibodies. Mice were infected intravenously with 5 × 10⁶S. aureus 30 days after surgery. Anti-S. aureus IgM and IgG1 antibodies were evaluated in serum at day 6 post-infection by enzyme-linked immunosorbent assay. Data represent means of six mice from a representative experiment. *P < 0·05 versus CT and AT groups; #P < 0·05 versus CT.