Antimicrobial Resistance Patterns of the Gram-positive Bacteria Isolated from Children with Bloodstream Infection in an Iranian Referral Hospital: A 6-year Study

Background: Bloodstream infections (BSI) are considered as a serious cause of morbidity and mortality in children. The aim of this study was to report the common Gram-positive bacteria (GPB) responsible for bloodstream infections in children and determine their antimicrobial resistance patterns in Children Medical Center (CMC) Hospital, Tehran, Iran. Methods: This retrospective study was conducted within a six-year period (March 2011 to September 2016) for pediatric patients with BSI. Standard bacteriological methods were performed for identification of the bacteria. Antimicrobial susceptibility tests were evaluated by using the disk diffusion method according to the CLSI recommendations. Results: Among 68233 blood cultures, 2349 isolates were obtained which 59% of them (N=1393) were GPB and 41% (n=956) were Gram-negative. The most common GPB isolates were Coagulase negative Staphylococcus (CoNS) (N= 609, 44%), followed by Staphylococcus aureus (N=319, 23%), Enterococcus spp. (N=139, 10%), Streptococcus pneumonia (N= 106, 8%), Streptococci viridans (N= 180, 13%) Micrococcus spp. (N=24, 1.7%) and Streptococcus group B (N= 16, 1%). The rate of methicillin resistance in S. aureus and CoNS was 47% (N=116/246) and 91% (N=557/609), respectively. Isolates of S. pneumoniae showed high-level of resistance to trimethoprim/sulfamethoxazole (N=28/33, 85%) and erythromycin (N=59/91, 65%). S. viridans isolates and Micrococcus spp. were highly sensitive to linezolid (100%). All of the tested isolates of Streptococcus group B were sensitive to all the antibiotics used in this study. Among Enterococcus spp., 52% (N=69/133) of the m were resistant to vancomycin. Conclusions: Our results emphasize the importance of a valuable guide in identifying resistance trends and selecting appropriate antibiotic.