Streptococcus infection and splenectomy

Targeting TREM-1 Signaling in the Presence of Antibiotics is Effective Against Streptococcal Toxic-Shock-Like Syndrome (STSLS) Caused by Streptococcus suis

Streptococcus suis (S.suis), a major swine pathogen, is also a severe threat to human health. Infection with highly virulent strains of S. suis can cause human Streptococcal toxic-shock-like syndrome (STSLS), which is associated with high serum pro-inflammatory cytokine levels and a high mortality rate. Our previous study indicated that highly virulent S. suis infection could activate the TREM-1 signaling pathway, which promotes host clearance of S. suis during early infection. However, it remained to be elicited whether TREM-1 signaling could be a target against STSLS in the presence of antibiotic. In the present study, mice were infected with a highly virulent S. suis strain and then treated with rTREM-1 (the recombinant extracellular domain of TREM-1) to block TREM-1 signaling, antibiotics, both rTREM-1 and antibiotics, or PBS. The survival rates, clinical signs, serum IL-1β and TNF-α levels, and serum bacterial loads were evaluated. Treatment with rTREM-1 could aggravate the outcome of infection as described previously. Although the conventional treatment with antibiotics contributed to effective S. suis clearance, it did not improve survival significantly. In comparison, due to the reduction of the exaggerated pro-inflammatory response, treatment combined with rTREM-1 and antibiotics not only led to efficient bacterial clearance but also alleviated inflammation. In conclusion, TREM-1 signaling contributed to severe inflammatory response and benefited S. suis clearance. Therefore, blocking TREM-1 signaling could still be a target for the treatment of STSLS in the presence of antibiotics.

TREM-1 signaling promotes host defense during the early stage of infection with highly pathogenic Streptococcus suis

Infection with highly pathogenic Streptococcus suis can cause septic shock, which is characterized by high levels of inflammatory cytokines and a high mortality rate. Our previous study indicated that TREM-1 (triggering receptor expressed on myeloid cells 1) was upregulated in swine spleen cells in response to S. suis infection. The role of TREM-1 signaling in enhancement of the proinflammatory response promoted us to examine its effect on the outcome of S. suis infection. In the present study, the recombinant extracellular domain of TREM-1 (rTREM-1) and an agonistic TREM-1 antibody were used to inhibit and activate TREM-1 signaling to evaluate its role in neutrophil activation, pathogen clearance, proinflammatory cytokine response, and the outcome of highly pathogenic S. suis infection in a mouse model. Blockage of TREM-1 signaling caused a more severe proinflammatory response to S. suis infection and increased the mortality rate, while its activation had the opposite effect. Blockage or activation of TREM-1 signaling lowered or raised the number of neutrophils in the blood, which correlated well with host clearance of S. suis. In conclusion, the TREM-1-mediated innate immune response played an essential role in the activation of neutrophils and S. suis clearance, which further reduced severe inflammation and finally benefited the outcome of the infection.

Mycotic abdominal aortic aneurysm due to Streptococcus suis: a case report

BACKGROUND

Streptococcus suis is a common infection of pigs. Human infection is often related to accidental inoculation through skin injuries during occupational exposure to pigs and pork. The disease may present as meningitis, bacteremia, and less commonly endocarditis, arthritis, or bronchopneumonia.

METHODS

Case report and review of the literature.

RESULTS

We report a case of bacteremia and severe sepsis caused by S. suis serotype 2 complicated by septic arthritis in a 56-year-old male with history of a prior contact with unprocessed pork. The causative agent was isolated from blood cultures and aspirated synovial fluid. The patient's condition improved after treatment with penicillin, but he was found subsequently to have an abdominal aortic aneurysm, confirmed by computed tomography (CT) scan. The mycotic aneurysm was successfully repaired using an in situ graft reconstruction. Tissue samples analyzed using polymerase chain reaction identified S. suis serotype 2 as the causative organism. After completion of two weeks of parenteral antibiotics, an oral form of ciprofloxacin (0.25 g twice a day) was continued for one month. The patient was discharged from our institution after uncomplicated recovery. Clinical review, a CT scan, and inflammatory markers nine months after surgery revealed no evidence of infection.

CONCLUSION

This is the first report of mycotic aneurysm caused by S. suis, which may be an etiologic agent of mycotic aneurysms, especially when complicated by bacteremia in adults with a recent history of contact with pigs or unprocessed pork.

Streptococcus suis: a new emerging or an old neglected zoonotic pathogen?

Infections caused by Streptococcus suis are considered a global and an economical problem in the swine industry. Moreover, S. suis is an agent of zoonosis that afflicts people in close contact with infected pigs or pork-derived products. Although sporadic cases of S. suis infections in humans (mainly meningitis) have been reported during the last 40 years, a large outbreak due to this pathogen emerged in the summer of 2005 in China. The severity of the infection in humans during the outbreak, such as a shorter incubation time, more rapid disease progression and higher rate of mortality, attracted a lot of attention from the scientific community and the general press. In fact, the number of publications on S. suis (including the number of reported human cases) has significantly increased during recent years. In this article we critically review the present knowledge on S. suis infection in humans, we discuss the hypotheses that may explain the 2005 outbreak and the repercussion of such an episode on the scientific community.

Streptococcus suis infections in humans: the Chinese experience and the situation in North America

Infections caused by Streptococcus suis are considered a global problem in the swine industry. In this animal species, S. suis is associated with septicemia, meningitis, endocarditis, arthritis and, occasionally, other infections. Moreover, it is an agent of zoonosis that afflicts people in close contact with infected pigs or pork-derived products. Although sporadic cases of S. suis infection in humans have been reported, a large outbreak due to S. suis serotype 2 emerged in the summer of 2005 in Sichuan, China. A similar outbreak was observed in another Chinese province in 1998. Symptoms reported in these two outbreaks include high fever, malaise, nausea and vomiting, followed by nervous symptoms, subcutaneous hemorrhage, septic shock and coma in severe cases. The increased severity of S. suis infections in humans, such as a shorter incubation time, more rapid disease progression and higher rate of mortality, underscores the critical need to better understand the factors associated with pathogenesis of S. suis infection. From the 35 capsular serotypes currently known, serotype 2 is considered the most virulent and frequently isolated in both swine and humans. Here, we review the epidemiological, clinical and immunopathological features of S. suis infection in humans.

Streptococcus suis: an emerging zoonotic pathogen

Streptococcus suis is a major porcine pathogen worldwide, and can be transmitted to human beings by close contact with sick or carrier pigs. S suis causes meningitis, septicaemia, endocarditis, arthritis, and septic shock in both pigs and human beings, and mortality is high. Human infection with S suis occurs mainly among certain risk groups that have frequent exposure to pigs or pork. Outbreaks of human S suis infection are uncommon, although several outbreaks have occurred in China in recent years. In July, 2005, the largest outbreak of human S suis infection occurred in Sichuan province, China, where 204 people were infected and 38 of them died. There have been 409 cases of human S suis infection worldwide, most of which have occurred in China, Thailand, and the Netherlands, and these infections have led to 73 deaths. This review provides background information on the biology and molecular characteristics of this Gram-positive bacterium, and describes the clinical signs, pathology, epidemiology, diagnosis, and treatment of human infection with S suis.