Concurrent Infection of Orientia Tsutsugamushi with Rickettsia spp. Including Rickettsia felis in North Central Bangladesh.

Rickettsial diseases are one of the leading causes of treatable acute febrile illness in Asia pacific region. This cross-sectional descriptive study was conducted at Department of Microbiology, Mymensingh Medical College to diagnose scrub typhus by rapid Immunochromatographic Test (ICT) and Nested PCR followed by molecular identification of possible Rickettsial coinfection among suspected febrile patients in Mymensingh, Bangladesh from March 2019 to February 2020. Among the enrolled 402 patients, 89 samples (22.13%) were seropositive by Immunochromatographic Test (ICT) and 65 samples (16.16%) were positive for O. tsutsugamushi DNA by Nested PCR, targeting 47KDa gene. Therefore, 113/402 (28.10%) samples were positive for scrub typhus by PCR and/or ICT. All the scrub typhus positive samples were further subjected to Nested PCR targeting 17 KDa gene for identification of Rickettsial co-infection and 13/113 (11.50%) were documented as positive. Then 13 Rickettsial co-infected samples were undertaken to automate sequencing and all were genetically confirmed as Rickettsia felis. Findings of the study may help clinicians to expand their list of differential diagnoses for undifferentiated fever and detection of Rickettsial co-infection may guide them to prescribe effective antimicrobials.

Role of Immune Cells and Cytokines for Immune Response in Kala-Azar.

Resolution of leishmanial infection is dependent on the coordinated interactions between components of cell mediated immune response, central to which is the activation of targeted T-cell populations for appropriate cytokine production and activation of infected cells. There is a correlation between the clinical outcome of Leishmania infection and the cytokine response profile. While a protective immune response against Leishmania has been clearly identified to be related to the influence of a type-l response and IFN-γ production, the precise role of T helper (TH) 2 cytokines in non-healing infections requires further exploration. Experimental evidence and clinical studies indicate multifaceted role of various factors leading to parasite survival and multiplication. In early stage of infection, generation of reactive oxygen and nitrogen intermediates play significant role in curtailing the parasite multiplication. In later phase, hepatic resistance is expressed by the dominant role played by nitric oxide synthase (NOS)-2 gene regulation and on the other hand, production of inhibitors of NOS-2 gene expression, interleukin 10 (IL-10) and transforming growth factor-ß (TGF-ß) correlate well with reduced parasite killing. The hepatic infection is usually self-limiting due to production of multiple cytokine responses including moderate level of tumour necrosis factor (TNF) but in spleen excess TNF mediates destructive pathology. CD8+ T cells appear to play multiple roles comprising both cytotoxic activity and secretion of cytokines and chemokines. A better understanding of the innate and acquired immune functioning of the host could aid in rational control and better therapeutic intervention of the disease.