Trends in Microorganisms Isolated from Blood Cultures at a Veterans Hospital from 2012 to 2015

Abstract

Blood culture is important to detecting bacteremia and fungemia in patients with suspected sepsis. We observed a four-year trend of blood culture isolates in the frequency by age group and in vitro antimicrobial susceptibility patterns obtained at VHS Medical Center, the largest veterans hospital in Korea. Blood cultures collected between 2012 and 2015 were analysed retrospectively. Of 68,352 blood specimens, 7,901 isolates were identified during the study period. Seventy-two percent of the isolates were gram-positive cocci, 18% were gram-negative rods, and 6% were fungi. The frequency of bacteremia/fungemia in patients who were 80-89 years old was 43.8%, the highest rate among all age groups, and the mean age of patients diagnosed by blood culture was 77 years old. Coagulase-negative staphylococcus (52.3%), Staphylococcus aureus (8.3%), enterococci (7.5%), Escherichia coli (6.4%), and Klebsiella pneumoniae (3.9%) were the bacteria most commonly isolated. The percentage of methicillin-resistant S. aureus increased in 2015 (76%) relative to that in 2012-2014 (63%-65%), and that of vancomycin-resistant Enterococcus faecium was 17%-22% with no significant changes through time. Among the gram-negative isolates, the ciprofloxacin resistance rate increased to 51.4% (E. coli) and 31.1% (K. pneumoniae) in 2015, but imipenem or ertapenem resistance was still very rare, with resistance rates of less than 0.5%. Acinetobacter baumannii showed a high rate of resistance (over 70%) to imipenem and ciprofloxacin throughout the study. In Pseudomonas aeruginosa, the resistance rates of imipenem and ciprofloxacin increased dramatically over time. This analysis confirmed a decrease in antimicrobial susceptibility of gram-negative rods isolated by blood culture.