Frequency and antibiotic resistance patterns of isolated bacteria from positive blood culture of hospitalized patients

Bloodstream infections are the most important causes of morbidity and mortality in hospitalized patients. Blood culture plays an important role in identifying most of bacterial agents of bloodstream infections. Knowledge about bacterial agents of bloodstream infections and also antibiotic resistance of these bacteria are important. Antibiotic resistance among bacterial agents of bloodstream infection including Acinetobacter, Klebisella, Pseudomonas, Escherichia coli, Enterobacter, Enterococcus, Staphylococcus aureus and Staphylococcus coagulase negative (CoNS) is one of the major challenges faced by physicians in treating. Therefore, this study was aimed to determine the frequency and antibiotic resistant patterns of bacterial isolates from hospitalized patient's blood cultured samples in the hospital, Tehran, Iran.
This research is a descriptive and retrospective study based on recorded data in Shariati hospital laboratory and under the supervision of Tehran University of Medical Sciences. The bacterial isolates were collected from positive blood cultures from October 2013 to March 2014. The frequency of bacterial isolates were determined by phenotypic and biochemical tests. The antibiotic resistance patterns of isolated bacteria were found by disk diffusion agar method. The diameters of inhibition zone were recorded and interpreted according to Clinical and Laboratory Standards Institute (CLSI) 2013.
The frequency of bacterial isolates was determined among 595 positive blood cultures as followed: 41% Pseudomonas, 20% Staphylococcus epidermidis, 10% Escherichia coli, 6% Acinetobacter lwoffii, 6% Staphylococcus aureus, 5% Stenotrophomonas, 3% Acinetobacter baumannii. The antibiogram test showed that 96.2% of Acinetobacter lwoffii, 92.8% of Acinetobacter baumannii, 66% of Pseudomonas aeruginosa, 85.7% of Staphylococcus epidermidis, 65% of Staphylococcus aureus, 75% of Klebsiella, 73.7% of Escherichia coli, and 50% of Stenotrophomonas were resistant to imipenem, piperacillin, piperacillin, erythromycin, erythromycin, ciprofloxacin, trimethoprim-sulfamethoxazole, and ceftazidime respectively.
The most prevalent bacterial isolate among the blood cultures of patients was Pseudomonas. The patients more than 50 years were more susceptible to blood stream infections. The most bacteria were isolated from the internal medicine department of hospital. The antibiotic resistance was also increasing especially in Acinetobacter, Staphylococcus coagulase negative, Escherichia coil and Klebsiella