Inflammatory Cytokines for Early Prediction of Gram Positive Bacterial Infection in Cancer Patients under Radiotherapy Treatment

Abstract

Infection is the most common complication of chemotherapy-induced neutropenia. Bacterial infections predominate during the early stages of a neutropenic episode, whereas invasive fungal infections tend to occur later. The epidemiological pattern of bacterial infection continues to evolve globally and locally, as do patterns of antimicrobial susceptibility and resistance. These trends are often associated with local treatment practices and have a significant effect on the nature of empirical antimicrobial therapy. The increasing rates of antimicrobial resistance among both Gram-positive and Gram-negative bacteria isolated from patients with neutropenia are posing new challenges. The present study aimed to prove the relation between microbial infection in feverish cancer and non-cancer patients and inflammatory mediators (IL-6 and TNF- α) secreted by the host immune response at fever onset in predicting the species of involved micro-organism compared to routinely used markers such as total WBCS and CRP, as well as the effect of radiotherapy on selected isolates of Gram positive bacteria cell membrane proteins and their antimicrobial sensitivity. Also, the effect of gamma irradiation on IL-6 serum levels in rats with induced fever of bacterial and non-bacterial origin was investigated through the animal model on forty eight adult rats and comparisons between groups were performed. A total of 100 blood samples collected from feverish cancer and non- cancer patients admitted to the inpatient clinics at the National Cancer Institute, El-Demerdash Educational Hospital, Ain Shams University and from those of the outpatient clinics at the Tumor Treatment Unit, Atomic Energy Authority and El Abassia Fever Hospital were enrolled in the study. Serum and plasma samples separated from blood specimens at fever onset were used for assay of inflammatory biomarkers (IL-6 and TNF- α) using ELISA technique, CRP using latex serology agglutination test. Total WBCs ______________________________________________________ Summary 124 count was determined by coulter counter. Blood culture was done for isolation of Gram positive bacteria which were identified by microscan and API Staph technique and subjected to antibiotic susceptibility test using disc diffusion method. Cell membrane protein profile of 2 selected isolates before and after gamma irradiation was performed by SDS-PAGE to detect the bands responsible for TNF-α production by host cells. Assay of serum IL-6 in rats was also done using ELISA technique. Cesium 137 (137 Cs) Gamma cell 40 located at National Center for Radiation Research and Technology (Cairo, Egypt) was the irradiation source in the study. It was found that out of 100 blood samples collected, there were 64 samples feverish cancer patients and 36 feverish non-cancer patients representing 64% and 36%, respectively. About 69% of blood culture samples collected from cancer patients showed positive bacterial growth and 31% showed negative growth. While, blood samples showing positive growth in non-cancer patients were 25 % and negative 75%. The most common species isolated from both cancer and non-cancer patients out of 53 positive blood culture cases were identified in this study as: S. aureus (16.98%), S. epidermidis (15%), S. hominis (13.2%), S. auriularis (11.32%), S. cohnii (9.43%), S. hysicus (5.66%), S. warneri (3.77%), S. sciuri (3.77%), S. capitis (1.87%), S. lugdunensis (1.87%), S. chromogenes (1.87%), S. intermedius (1.87%) and Micrococcus (13.2%). Results showed that, IL-6 and TNF-α serum levels were higher in feverish patients with positive blood cultures for Gram positive cocci compared to those with non-microbial fever for both cancer and non-cancer patients. There was a significant difference in both mediators’ levels for both cancer and non-cancer patients with Gram positive bacteremia and those without bacteremia, with P-value=0.0017, 0.0261 (for cancer patients), 0.0256 and 0.0023 (for non-cancer patients), respectively. ______________________________________________________ Summary 125 CRP serum level was found positive for agglutination in all cancer and non-cancer patients (with positive blood cultures), could not be detected in serum of healthy controls as well as most of non-infected patients (negative agglutination). The cut-off levels to distinguish bacteremic (positive blood cultures) and non-bacteremic (negative blood cultures) cases were determined using receiver operating characteristic curves (ROC): for IL-6 it was 152 pg/ ml for cancer patients, 157 pg/ ml for non-cancer patients with specificity 100% and 77.8%, sensitivity 81.3% and 77.8%, positive predictive value 100% and 77.8%, negative predictive value 84.2% and 77.8%, and efficacy 90.6% and 77.8%, respectively. While, the cut-off level of serum TNF-α was 14 pg/ ml for cancer patients and 13 pg/ ml for non-cancer patients, with specificity 100% for each, sensitivity 85.7% and 100%, positive predictive value 100% for each, negative predictive value 87.5% and 77.8%, and efficacy 90.6% and 77.8%, respectively. Also, there were direct