Identification of Pathogenic Bacteria in Blood Cultures and Susceptibility Testing of Isolates With Various Antibiotics

Abstract

Background: Blood infections are an extensive range of disorders that can vary from limited bacteremia to fatal septicemia. Bac- teremia refers to the transient presence of a bacterium in the bloodstream. A delay in the diagnosis and treatment of sepsis can cause mortality, with a 20% - 50% prevalence rate. Objectives: Due to the changing patterns of antibiotic resistance, as well as dierences in patterns over time in dierent settings, we decided to identify infectious agents and their antibiotic resistance patterns in blood cultures. Materials and Methods: This study was conducted at Shahid Beheshti hospital, Hamadan, Iran, during a one-year period (March 21, 2014, to March 22, 2015). From patients with suspected bloodstream infections, 5-10 mL of blood was collected three times and inoculated into culture bottles. After identifying the types of microorganisms, susceptibility testing was performed according to CLSI standards, and the results were analyzed with statistical software. Results: In the present study, 2,130 blood cultures were obtained from 710 patients (384 females and 326 males). Of these cultures, 232 (18.9%) were positive; 107 (46%) and 125 (54%) were from females and males, respectively. Most of the positive cultures were re- lated to the internal medicine and hematology wards, which had 132 cases (56.9%), and the ICU, with 37 cases (16%). The most frequent isolates were Pseudomonas aeruginosa, Escherichia coli, Acinetobacter baumannii, and coagulase-negative Staphylococcus aureus, with prevalence rates of 18.2%, 24.1%, 10.3%, and 10.3%, respectively. The most eective antibiotic against Gram-positive isolates was van- comycin. Conclusions: This study revealed that the most eective antibiotics against two Gram-negative and Gram-positive groups were amikacin and norfloxacin, so it is recommended that these antibiotics be used empirically, at least in the setting where this study was conducted, before performing the culturing and antibiogram process.