Analysis of Host Factor related to Patient's Mortality due to Viridans Streptococcal Bacteremia

Abstract

In their study entitled Factors associated with infective endocarditis and predictors of three-month mortality in patients with Viridans streptococcal [1], Suh et al. suggest that underlying valvular heart disease and persistent bacteremia are independently associated with viridans streptococcal infective endocarditis (VSIE). The authors recommend routine echocardiography in patients who have these conditions. Previous steroid use and immunosuppressive therapy have both been shown to be associated with poor prognosis in patients with viridans streptococcal bacteremia (VSB) [1]. Many studies have shown that viridans streptococci cause various and severe infections [2-4] and play an important role in the etiology of primary bacteremia following immunosuppressive therapy [5]. In light of these findings, there is growing interest among clinicians about viridans streptococci and their role in infection. Suh et al. reported that previous steroid use and immunosuppressive therapy are independently associated with mortality due to VSB. However, it is difficult to ascertain which specific host comorbidities are linked with increased mortality in VSB because Suh et al. did not specifically identify underlying conditions in patients with a history of steroid use and immunosuppressive therapy. Therefore, the aim of this study was to analyze the relationship between underlying disease, steroid use, chemotherapy, malignancy, infective endocarditis, and comorbidity in patients who died of VSB and compare our results with those of Suh et al. In this study, of 259 patients diagnosed with VSB between October 2002 and December 2012 in a university-affiliated hospital, 106 patients younger than 18 years were excluded, leaving 153 patients for final analysis. Of these, 19 patients (12.4%) died before the end of the study (Table 1). Of the 19 patients, three (15.8%) had VSIE and two had a history of heart disease (one mitral valvuloplasty and one hypertrophic cardiomyopathy). Of the 19 patients who died of VSB, six (31.6%) took immunosuppressive therapy and, three (15.8%) also took steroids. None of the patients received steroid monotherapy. Of the six patients (31.6%) who had undergone immunosuppressive therapy, four were diagnosed with hematological malignancy and two were diagnosed with solid tumors (one lung cancer and one pancreatic cancer). Four of the 19 patients who died (21.1%) were diagnosed with diabetes mellitus, two (10.5%) had cerebral hemorrhage, and two (10.5%) had no underlying disease. Table 1 The mortality cases of viridans streptococcal bacteremia in a tertiary university hospital In this study, the proportion of patients with VSIE to patients who died from VSB is higher than that reported by Suh et al. (15.8% vs. 8.3%). Because two of the three patients diagnosed with VSIE in the present study had underlying heart disease, echocardiography was required to evaluate the presence of infective endocarditis. Mortality due to VSB was high among the immunocompromised patients who received chemotherapy for hematological malignancies or solid tumors. Therefore, extensive assessment and early diagnosis of VSB are necessary in these patients. Unlike the study by Suh et al., 13 (68.4%) of 19 patients in our study who had not received steroid or immunosuppressive therapy died of VSB. Therefore, it is important to note that mortality is still high in immunocompetent patients. In conclusion, we recommend appropriate care for VSB patients who have underlying heart disease and immunosuppressed patients (especially after chemotherapy for hematological malignancy or solid tumors) who are currently taking steroids. Moreover, we must keep in mind that VSB occurs in various hosts. This was a small, single-center, retrospective study and therefore had limitations. Collection of data on a national level, possibly including analyses of large administrative datasets or prospective comparisons, should be performed to confirm these observations.