[Drug resistance of Acinetobacter baumannii in pediatric intensive care unit]

Objective: To investigate the drug resistance and related gene expression of Acinetobacter baumannii (AB) among the patients in pediatric intensive care unit (PICU). Methods: Drug resistance of 311 clinical cultured AB strains in PICU of Shengjing Hospital of China Medical University between January 2014 to December 2018 were analyzed retrospectively. According to the results of drug resistance test, all strains were divided into carbapenem-resistant Acinetobacter baumannii (CRAB) and non-carbapenem-resistant Acinetobacter baumannii (non-CRAB). The CRAB closely related genes were tested by real time quantitative polymerase chain reaction (RT-PCR). Comparison between the groups was analyzed by t test, Mann-Whitney U test, Chi-square test or Fisher exact test. Multivariate logistic regression was used for multivariate statistics. Results: A total of 166 patients with 311 AB strains were enrolled in this research, including 101 males and 65 females. The children's age ranged from 1 month to 14 years. The main primary diseases of 166 children were severe pneumonia (66/166, 39.8%), central nervous system infection (28/166, 16.9%), and trauma (17/166, 10.2%). Drug sensitivity tests showed that AB was sensitive to tigecycline (280/311, 90.0%), amikacin (250/311, 80.4%), and cefoperazone-sulbactam (193/311, 62.1%). However, most of AB strains were resistant to ciprofloxacin (247/311, 79.4%), ampicillin (244/311, 78.5%), and ceftazidime (245/311, 78.8%). In 311 isolated strains, 82.6% (257/311) strains were CRAB, and 65.9% (205/311) strains were multidrug-resistant Acinetobacter baumannii (MDRAB). Carbapenems were used more often in CRAB group than non-CRAB group before Acinetobacter baumannii cultured (26.2% (34/130) vs. 8.3% (3/36), χ²=5.169, P=0.023), and more patients in CRAB group used the third-generation cephalosporins for more than 7 days (43.8% (57/130) vs. 22.2% (8/36), χ²=5.533, P=0.019). Other broad-spectrum antibiotics or combined antibiotics in CRAB group were also more frequently used than in non-CRAB group (47.7% (62/130) vs. 13.9% (5/36), 46.9%(61/130) vs. 22.2%(8/36); χ²=13.383, 7.082; P<0.01, P=0.008). More patients in CRAB group received interventional procedures than those in non-CRAB group (75.4% (98/130) vs. 50.0% (18/36), χ²=8.631, P=0.003). Multivariate logistic regression showed that using carbapenem antibiotics (OR=3.179, 95%CI 1.247-8.107, P=0.015) and interventional procedures (OR=5.107, 95%CI 1.446-18.042, P=0.011) were independent risk factors for causing CRAB. Both IPM and OXA-24 genes had high expressions in CRAB and non-CRAB groups (89.2% (116/130) vs. 86.1% (31/36), P=0.565; 77.7% (101/130) vs. 72.2% (26/36), P=0.49). VIM and OXA-58 genes were not detected in any group. The expression rates of OXA-23, OXA-51, and efflux pump-related genes AdeABC and AdeFGH in CRAB group were significantly higher than in non-CRAB group (all P<0.01). Conclusions: In PICU, the proportions of CRAB and MDRAB were high and most of AB strains are only sensitive to tigecycline, amikacin, cefoperazone or sulbactam. Using carbapenems and interventional operation are independent risk factors for causing CRAB. Compared with non-CRAB, CRAB had higher expression of β-lactamase-related genes OXA-23 and OXA-51, and efflux pump-related genes AdeABC and AdeFGH.