Epidemiology of pathogens isolated from blood cultures processed at the “Salam Center for Cardiac Surgery” in Khartoum (Sudan)

Abstract

Introduction. Sepsis is a systemic inflammatory response to infection and it is a common cause of morbidity and mortality particularly in elderly, immunocompromised and critically ill patients. Blood culture represents the gold standard for bacteraemia diagnosis. Aim of our study was to assess Gram positive and Gram negative microorganisms isolated from bloodcultures collected from patients hospitalized in “Salam Center for Cardiac Surgery” of Khartoum (Sudan). Methods. The study was conduced from april 2008 and march 2009. In this period we analyzed 328 samples collected from hospitalized patients already operated or waiting for surgery, presenting fever of unknown origin (temperature >38°C). We analyzed at least 3 bloodcultures for each patient, which were incubated at 37°C for 8-10 days. During the incubation period the bottles were periodically examined for macroscopic evidence of growth and the laboratory staff performed blind subcultures after 48 h one from each other starting from the inoculation time. The isolated bacteria were finally tested for antibiotics sensitivity. Results. Of 328 bloodcultures processed 57 were positive (17.4%), of whom 40.3% caused by gram positive microorganisms and 59.7% by gram negative. The identification tests showed that among gram positive-related infections those caused by MRSA (Methicillin Resistant Staphylococcus aureus) predominated (65.2%), while the most prevalent causative agents among gram negative-related infections were Enterobacter spp. (20.6%), Serratia spp. (14.7%), Pseudomonas spp (8.8%) and Escherichia coli (8.8%). Conclusion. In this study we observed that the most frequent isolates were MRSA, whereas no infection caused by CNS (Coagulase-negative Staphylococci) was revealed. Susceptibility tests showed presence of presumptive extended-spectrum ß-lactamases (ESBLs) in Enterobacteriaceae and that aminoglycosides were the most effective antibiotics against both Gram positive and Gram negative bacteria. The infection process interested patients already operated more than patients waiting for surgery.

Keywords

• Blood culture, Bacteraemia, Bacteria identification, Sensitivity test, Critically ill patients