Neonatal Intensive Care Unit Of Multiple Drug Resistance Bowman Acinetobacter Resistance Mechanisms And Homology

Objective To analyze the nosocomial infections, antimicrobial resistance pattern of multidrug-resistant Acinetobacter baumannii(MDR-AB) in our neonatal intensive care unit (NICU); to determine distribution the role ofβ-lactamase, the outer membrane protein(OMP) and the capacity of forming biofilm among MDR-ABs; to study the homology of MDR-AB; so as to provide basis for comprehensive exposition of resistance mechanisms, drug development, clinical treatment and control of nosocomial infections.Methods 1. Twenty six isolates of MDR-AB were collected from clinical specimens in our NICU for analysis. The minimum inhibitory concentrations (MICs) of 13 antimicrobial agents were determined by ager dilution method.2. oxa-23, oxa-24, oxa-51, oxa-58, ampC, imp-1, imp-4 and vim-2 genes for these strains were amplified by PCR and sequenced.3. OMPs of these clones were extracted by sonication and ultracentrifuge and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).4. The biofilm formation ability of multidrug-resistant Acinetobacter baumannii was measured by 96-well microtiter plates with crytal violet staining. To observe the formation and characteristics of MDR-AB bacterial biofilm by confocal laser scanning microscopy(CLSM).5. Pulse field gel electrophoresis(PFGE) was performed to analyze homology of 26 clinical isolates.Results 1. The resistant rates of the 26 strains to Ceftazidime, Cefoxitin, Ccfoperazone-sulbactam and Ciprofloxacin were 100%, followed by Cefoperazone (96.15%), Imipenem(92.31%), Meropenem(92.31%), Cefoperazone-sulbactam(92.31%), Sulfamethoxazole-trimethoprim(92.30%), Cefepime(84.61%), Levofloxacin(80.77%), Amikacin(80.76%), and all the strains were sensitive to Polymyxin B.2. Among the 26 MDR-AB strains,77%(20) strains possessed oxa-23 gene,54%(14) carried ampC gene, both oxa-23 and ampC were indentified in 42%(11) of the strains, while oxa-24, oxa-58, imp-1, imp-4 or vim-2 gene was not identified.3. The analysis of outer membrane proteins showed that around 25KDa-band deficiency or decreasing was found in multi-drug Acinetobacter baumannii.4. Among the 26 MDR-AB strains,19(73.1%) isolates formed biofilm, and capacities of most isolates were higher than ATCC19606's. CLSM revealed that the biofilm of clincical strains was more pyknotic than that of the standard strain.5. All the strains belonged to 4 clones according to the PFGE DNA patterns. Clone A included 21 strains, while clone B, clone C, clone D included 3strains,1strain and 1 strain, respectively.Conclusions Multidrug-resistant Acinetobacter baumannii are resistant to most agents. The resistance of MDR-AB in our NICU is serious. The resistant mechanism of MDR-AB is probably related to possess (3-lactamases, lack of the outer membrane protein and ability of formation biofilm. Clone dissemination plays a major role in MDR-AB infections. So it is important to take effective measures to control the spread of MDR-AB.