Risk factors and molecular epidemiology of Acinetobacter baumannii bacteremia in neonates.

Abstract

Acinetobacter baumannii infections in neonates are not uncommon but rarely studied. Clinical and molecular epidemiology of 40 patients with A. baumannii bacteremia in the neonatal intensive care units (NICUs) of a medical center from 2004 to 2014 was analyzed. Multi-drug resistance was found in only 3 isolates (7.5%). Sequence types (STs) of A. baumannii defined by multilocus sequencing typing were diverse, and 72.4% identified isolates belonged to novel STs. Majority of the isolates were susceptible to antibiotics tested. Among the 3 imipenem-resistant A. baumannii (IRAB) isolates, 2 (66.7%) belonged to ST684, a novel ST. All of the 3 isolates were susceptible to tigecycline and colistin. The predominant mechanism of imipenem resistance in these neonatal isolates is ISAba1-blaOXA-80, which has never been reported in Asia before. Most infected newborns were premature (95%), with very low birth weight (70%<1500g), prolonged intubation, usage of percutaneous central venous catheter (65%) and long-term usage of total parenteral nutrition or intravenous lipid (95%). IRAB infection, inappropriate initial therapy, 1-minute Apgar score and early onset infection within the first 10 days of life were found to correlate with mortality by log-rank test. Prior use of imipenem for at least 5 days and use of high frequency oscillation ventilation (HFOV) were statistically significant risk factors for acquiring IRAB infections. To reduce mortality of IRAB infection, it is crucial to consider giving effective agents, such as colistin, in 2 days for high risk neonates who has been given imipenem or used HFOV.