2009. Misidentification Rate of Acinetobacter baumannii Isolated From Invasive Infections in Children

BACKGROUND: Acinetobacter baumannii (AB) invasive infections are known to have a worse clinical outcome than non-baumannii Acinetobacter infections. However, currently, phenotypic identification by semi-automated commercial identification systems struggle to distinguish Acinetobacter subspecies; especially the four closely related subspecies of the Acinetobacter calcoaceticus–Acinetobacter baumannii (ACB) complex. The purpose of this study was to examine the rate of misidentification of AB isolated from invasive infections in children. METHODS: From January 2001 to December 2017, patients 18 years old and below who were treated for invasive AB infections at Seoul National University Hospital and Chungnam National University Hospital were included. Acinetobacter baumannii, identified by commercial identification systems, cultured from sterile body fluids of the study participants were prospectively collected. The DNA from the stored bacteria were isolated, and subspecies identification was carried out by PCR and sequencing of the partial gyrB gene. Clinical data were retrospectively reviewed. RESULTS: During the 17-year study period, 113 AB isolates were obtained from patients treated for invasive infections. The median age of the patients was 2 (IQR 0–7) years old and 47 (49.5%) were male. Duplicate isolates were eliminated, and a total 95 isolates underwent further investigation. The isolates were retrieved from the blood (n = 82), peritoneal fluid (n = 8), pleural fluid (n = 2), cerebrospinal fluid (n = 2), and bronchoalveolar fluid (n = 1). Of the AB isolates identified by the commercial identification systems, 55 (57.9%) were AB. Of the non-AB isolates identified by partial gyrB sequencing, 22 (23.2%) were identified as A. nosocomialis, 8 (8.4%) as A. pittii, and 1 (1.1%) as A. calcoaceticus. Non-ACB complex subspecies included A. soli (n = 3), A. seifertii (n = 3), A. iwoffii (n = 1), A. bereziniae (n = 1), and A. junnii (n = 1). CONCLUSION: There was a high rate of misidentification of the Acinetobacter subspecies causing invasive infections in children. Further studies are needed to analyze the burden that misidentification has on the treatment and outcome of patients with invasive infections. DISCLOSURES: H. Lee, Korean Society of Pediatric Infectious Diseases: Member, Research grant.