A Study on Community Acquired Bloodstream Infections, Molecular Characterization of Resistant Pathogens and Correlation with Inflammatory Markers in a Tertiary Care Hospital

Priyadharshini, A (2019) A Study on Community Acquired Bloodstream Infections, Molecular Characterization of Resistant Pathogens and Correlation with Inflammatory Markers in a Tertiary Care Hospital. Masters thesis, Madras Medical College, Chennai.

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Abstract

INTRODUCTION: Community acquired bloodstream infections refers to the infections detected within 48 hours of hospitalization, showing positive blood culture and develops spontaneously without an association with any prior medical interventions. AIMS AND OBJECTIVES: 1. To identify the clinical profile of patients and to detect the pathogens causing community acquired blood stream infections and their antimicrobial susceptibility pattern. 2. To correlate the inflammatory markers with blood culture positivity and to assess the prognosis, severity and outcome of disease with these markers. 3. To perform the molecular characterization of resistant pathogens. METHODOLOGY: Under strict aseptic precautions, blood samples collected from febrile adult patients admitted within 48hrs with suspected sepsis were processed as per standard protocol and isolates identified based on Gram stain, colony morphology and various biochemical reactions. Antimicrobial susceptibility testing for isolated organisms performed by Kirby-Bauer disk diffusion method as per CLSI guidelines. Vancomycin sensitivity tested using Vancomycin Screen agar and also confirmed by E-strip test. Resistant strains were characterized by PCR.CRP and IL-6 concentrations were detected using latex slide agglutination and sandwich ELISA method respectively. RESULTS: Blood culture in 150 patients, detected 12 patients (8%) with community acquired bloodstream infection, majority in the age group 51-60yrs (50%) with males being predominantly affected (75%).Gram positive organisms 58% (Methicillin sensitive Staphylococcus aureus 85.7% and 14.3% Methicillin resistant Staphylococcus aureus) and 42% Gram negative organisms (Escherichia coli 60% which were ESBL producers, 20% Acinetobacter baumannii and 20% Pseudomonas aeruginosa) were isolated. Gram positive organisms were highly sensitive to Erythromycin, Vancomycin, Linezolid each 100% respectively and Gram negative organisms were highly sensitive to Amikacin, Tetracycline each 100% respectively.bla TEM and bla CTX-M genes were positive among ESBL producing E.coli isolates and mecA gene positive in MRSA isolate, by PCR. Diabetes mellitus (75%) and anaemia (58.3%) were the predominant risk factors and respiratory system was the predominant source (66.7%) associated in patients with community acquired bloodstream infection in this study. CRP and IL-6 concentrations were correlated with blood culture positivity (correlation significant with a p value 0.01), were found positive and significantly elevated in blood culture positive samples (CRP 190-400mg/l and IL-6 >= 200pg/ml).IL-6 was both sensitive and specific than CRP with sensitivity 83% (95% CI- 75%-89%), specificity 84% (95% CI-66%-94%), positive predictive value 95%(95% CI-88%-98%) and the negative predictive value 57% (95% CI-42%-71%) . Also, ROC curve plotted showed, area under the curve for IL-6 (67%) was more than CRP (61%) which proved IL-6, a better early sepsis marker than CRP. Haematological parameters were also correlated with inflammatory markers and blood culture positivity (correlation significant with a p value 0.05).75% patients with community acquired bloodstream infection recovered and (25%) expired. Among those expired, CRP and IL-6 levels were significantly raised (CRP- 300-400mg/l, IL-6-900-1200pg/ml) than the recovered group (CRP - 190-200mg/l, IL-6- 400-800pg/ml). In this study, statistically the median estimated IL-6 level by which the mortality in patients with community acquired sepsis could be predicted was found to be 1180pg/ml and the CRP concentration was 384mg/l. CONCLUSION: Community acquired bloodstream infections are rising as a major health problem in upcoming years due to the emergence of antimicrobial resistant strains in the community as well, like ESBL producers, MRSA etc. Hence, proper surveillance, framing of appropriate antibiotic policy and preventive strategies curtails the spread of these resistant strains in the community. IL-6 found to be a better early sepsis marker than CRP which reveals positivity within 24hrs of onset of sepsis than the conventional blood cultures. But still, blood culture remains the confirmatory and gold standard method in the detection of sepsis.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Community acquired sepsis, Blood culture, C-reactive protein, Interleukin-6.
Subjects: MEDICAL > Microbiology
Depositing User: Subramani R
Date Deposited: 23 Aug 2019 13:28
Last Modified: 23 Aug 2019 13:28
URI: http://repository-tnmgrmu.ac.in/id/eprint/11142

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