Increased γδ⁺and double negative T cell subsets in children with bacteremia of Salmonella oranienburg: an early diagnostic marker for bacteremia

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Bacteremia of Salmonella is a risk factor of death in Salmonella infection. Early diagnosis to initiate intensive care is a key for favorable outcome, yet no clinical marker is available to detect bacteremia of Salmonella earlier than blood culture. T, natural killer (NK), and B cells play an important role against Salmonella infection and expansion of γδ⁺ T cell subset was shown in the study mainly targeting typhoid Salmonella infection by flow cytometry (FCM) which can analyze immune cell populations within two hours. During outbreak of Salmonella oranienburg (SO) infection, we explored clinical marker to detect bacteremia in children with or without bacteremia of SO and those with enteritis due to other Salmonella using FCM. We also measured serum concentration of immunoglobulins (Igs) to evaluate whether immunocompromised or not. Eighteen children (median age, 6.0 years) were studied and divided into four groups; group A: five children with bacteremia of SO, group B: the same patients of group A who recovered 3 months after the onset of the disease, group C: six children with enteritis due to SO, and group D: seven children with enteritis due to other Salmonella but no bacteremia. The percentages ofγδ⁺ and double negative (DN: CD4^-CD8^-) T cells in CD3⁺ subset were increased in group A as compared to groups B, C and D. There was no difference between groups in the following variables; the percentages of CD3⁺ cells, helper (CD4⁺), and cytotoxic (CD8⁺) T cells, and NK cells, serum levels of Igs or complements. Our data suggest that expanded γδ⁺ and DN T cell subsets in SO bacteremia by FCM can help to detect SO bacteremia in early stage of the disease faster than blood culture.