The antimicrobial resistance to Acinetobacter baumannii is significantly high and continues to grow; it has become a global health issue, particularly in regards to carbapenem resistance . The expression of efflux pumps is one of the major mechanisms of antibiotic resistance in A. baumannii by, most prevalently, adeABC of the resistance/nodulation/division family. The detection rate of adeB was the highest in clinical isolates compared to others ( adeFGH, adeIJk ), although it varied among other strains. In this minireview, we explain the adeABC efflux gene in A. baumannii causing antibiotic resistance and compare adeABC with other efflux genes in order to discern the function of adeABC in A. baumannii resistance, which may help in the discovery of new antibacterial agents.

Objective To investigate the clinical features and outcomes of patients with mechanical ventilation-associated pneumonia (VAP) caused by Acinetobacter baumannii (Ab), and to characterize the drug resistance of pathogenic strains and carbapenem resistance-associated genes. Methods Clinical data were collected from the PICU of Shengjing Hospital. Patients who met the diagnostic criteria of VAP and for whom Ab was a pathogen were selected as study participants. The patients were divided into carbapenem-resistant A. baumannii (CRAB) and carbapenem-sensitive A. baumannii (CSAB) groups. The genes closely associated with Ab resistance to carbapenems and the efflux pump-related genes were detected by real-time polymerase chain reaction, and results compared between the two groups. Results The total mechanical ventilation time and the administration time of antibiotics after a diagnosis of Ab infection were significantly higher in the CRAB group. And the CRAB group strains were only sensitive to amikacin, cephazolin, compound sulfamethoxazole, and tigecycline. Genetic test results indicated that IPM expression was not significantly different between two groups. The OXA-51 and OXA-23 in the CRAB group was markedly higher than that in the CSAB group, while OXA-24 expression was markedly lower. The expression of AdeABC and AdeFGH was significantly greater in the CRAB compared to CSAB group. Conclusion In pediatric patients with VAP caused by Ab infection, the detection rate of CRAB strains is far higher than that of CSAB strains; The abnormal expression of β-lactamase-producing genes (OXA-23, OXA-24, and OXA-51) and efflux pump-related genes (AdeABC and AdeFGH) is closely related to the production of CRAB.

Acinetobacter baumannii is a major cause of hospital-acquired infections. Studies showed that carbapenem resistance was related to mortality. Carbapenem resistance depends on expression of β-lactamase in adults. The present study explores the relationship between β-lactamase gene expression and carbapenem resistance and outcomes in children with A. baumannii infections. Patients and Methods: We gathered clinical data of 131 children diagnosed with hospitalassociated A. baumannii infections from the pediatrics unit of Shengjing Hospital of China Medical University. We obtained 131 isolates of A. baumannii, determined the minimal inhibitory concentrations (MICs) for common antibiotics, and measured carbapenemaseencoding genes expression using real-time PCR. Results: We isolated 131 strains, 89 of which were carbapenem-resistant (MIC ≥ 8 µg/mL), and 42 carbapenem-sensitive strains. Univariate analysis identified statistically significant differences between the carbapenem-resistant group and the carbapenem-sensitive group for in-hospital days before infection, previous deep vein catheterization, previous urinary catheterization, previous treatment with a carbapenem (meropenem/imipenem), and expression of oxa-51 and oxa-23. Logistic regression analysis of factors associated with carbapenemresistant A. baumannii infections found significant associations with oxa-23 expression (hazard ratio [HR] 0.005, confidence interval [CI] 95% 0-0.153, P = 0.002) and previous carbapenem treatment (HR 0.031 CI 95% 0.1-0.959, P = 0.042). Of 131 patients, 27 died within 30 days. Cox regression analysis of factors associated with 30-day mortality from A. baumannii infections showed that cephalosporin combined with sulbactam (HR 0.271, CI 95% 0.101-0.723, P = 0.009) was associated with 30-day survival. Conclusion:The expression of oxa-23 and the use of carbapenems were independent risk factors for carbapenem resistance. The use of cephalosporins combined with sulbactam was independently associated with 30-day survival. We recommend using cephalosporins combined with sulbactam in children infected with A. baumannii.

Objective The study investigated the changes in drug resistance profile and genotypes of Acinetobacter baumannii (Ab) in the Pediatric Intensive Care Unit (PICU), northeast China. Methods Data on all Ab strains cultured from clinical isolates between 2012 and 2018 and the usage patterns of broad-spectrum antibiotics during this period were collected retrospectively. These Ab strains were revived and cultured for antimicrobial resistance testing, and the CRAB-related IPM, VIM, OXA-58, OXA-51, OXA-23, and OXA-24 genes were detected by RT–PCR. The test results were analyzed in conjunction with annual antibiotic usage for intergroup comparison. Results 541 Ab-positive specimens were collected, of which 370 strains were finally included in the study. 184 strains were subjected to genetic analysis. The CRAB strains identified were only sensitive to amikacin, cotrimoxazole, tigecycline, and cephazolin, whereas their resistance rates to the remaining nine antibiotics were higher than 50%. The use of cefepime was gradually reduced from 2014 to 2018, whereas cefotaxime sulbactam and ceftriaxone tazobactam was substitutionally increased. In contrast, the use of carbapenems antibiotics has been maintained at a minimal level. The expression levels of OXA-51 and OXA-23 were significantly higher, and OXA24 gene expression was significantly lower in the CRAB group than the CSAB group. Conclusion The detection rate of CRAB in northeastern China from 2012 to 2018 showed an increasing trend each year. The extensive use of the broad-spectrum antibiotic cefepime may be one of the risk factors leading to this high detection rate CRAB. The abnormal expression levels of OXA-51, OXA-23, and OXA24 are all closely related to the development of CRAB, which should be monitored dynamically to detect CRAB strains as early as possible.