Isolation of bacterial DNA followed by sequencing and differing cytokine response in peritoneal dialysis effluent help in identifying bacteria in culture negative peritonitis

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Peritonitis rate has improved over the years with the advancement in connectology and peritoneal dialysis (PD) techniques; however, it remains as one of the leading causes of morbidity, mortality and technique failure in PD patients. Accurate and timely diagnosis of bacterial peritonitis is crucial for effective and targeted treatment. Delayed diagnosis may result in treatment failure. The standard microbiological culture methods are inherently slow and inefficient. In many cases, culture yield is negative despite the presence of clinical evidence of infection.1 The incidence of culture negative peritonitis varies from 2% to 20%; however it has been reported up to 36.9% in some studies.3 The culture negative peritonitis is treated with non‐specific antibiotics and decision of antibiotics is difficult in this scenario. The empiric non‐specific antibiotics not only increase the cost of treatment but also increases the risk of antibiotic resistance producing beta‐lactamases, the commonest cause of resistance to beta‐lactam antibiotics.5 It is of great concern for the medical fraternity and in general for the whole society, particularly in developing countries where inappropriate therapy and overuse of antibiotics are the main causes driving multidrug resistance microbes, a major global threat for human health as also identified by the World Health Organization.6 Presently, the basis of diagnosis of infection in any body fluid is isolation of the organisms, which is based on the principles of Koch's postulate. The alternative modality is needed to diagnose the infection as in most cases, especially for those agents that cannot be cultivated in the laboratory; a causal relationship based on Koch's original postulates cannot be firmly established. Fredricks and Relman had suggested an alternative and revised set of Koch's postulates, which depends on isolation of bacterial DNA and sequence‐based identification of microbial pathogens.8 However, this sequence based method has not been explored in PD peritonitis. The isolation of bacterial DNA in effluent PD patients has recently been reported to predict relapsing peritonitis.9 Recently, Lin et al. showed distinct pathogen‐specific humoral and cellular responses that can be assessed quantitatively and qualitatively in PD patients. The Gram‐positive and Gram‐negative bacterial infection shows differential expression of cytokine in PD peritonitis.10 The isolation of bacterial DNA and various cytokines response can be exploited by identifying the micro‐organisms in peritonitis in PD patients. We undertook this study with objectives to isolate bacterial DNA from PD effluent and identify the specific organisms at genus and species level on gene sequencing and moreover, to identify the cytokine profile from PD effluent as immune fingerprints of infection, which can be used to identify bacteria causing peritonitis and as a possible guide to therapy.
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