Abstract
Acinetobacter baumannii, an important emerging pathogen of nosocomial infections, is known for its ability to form biofilms. Biofilm formation increases the survival rate of A. baumannii on dry surfaces and may contribute to its persistence in the hospital environment, which increases the probability of nosocomial infections and outbreaks. This study was undertaken to characterize the biofilm production of different strains of A. baumannii and the effects of chemical compounds, especially antibiotics, on biofilm formation. In this study, no statistically significant relationship was observed between the ability to form a biofilm and the antimicrobial susceptibility of the A. baumannii clinical isolates. Biofilm formation caused by A. baumannii ATCC 17978 after gene knockout of two-component regulatory system gene baeR, efflux pump genes emrA/emrB and outer membrane coding gene ompA revealed that all mutant strains had less biofilm formation than the wild-type strain, which was further supported by the images from scanning electron microscopy and confocal laser scanning microscopy. The addition of amikacin, colistin, LL-37 or tannic acid decreased the biofilm formation ability of A. baumannii. In contrast, the addition of lower subinhibitory concentration tigecycline increased the biofilm formation ability of A. baumannii. Minimum biofilm eradication concentrations of amikacin, imipenem, colistin, and tigecycline were increased obviously for both wild type and multidrug resistant clinical strain A. baumannii VGH2. In conclusion, the biofilm formation ability of A. baumannii varied in different strains, involved many genes and could be influenced by many chemical compounds.
Highlights
Acinetobacter baumannii, as an important emerging pathogen of nosocomial infection, is known for its ability to form biofilms (Longo, Vuotto & Donelli, 2014)
We have demonstrated that EmrAB contributes to adaptation to osmotic stress and resistance to colistin in A. baumannii (Lin, Lin & Lan, 2017a), its role in biofilm formation still needs to be clarified
We found that A. baumannii American Type Culture Collection (ATCC) 17978 decreased biofilm formation upon exposure to subinhibitory concentrations of amikacin, imipenem and colistin
Summary
Acinetobacter baumannii, as an important emerging pathogen of nosocomial infection, is known for its ability to form biofilms (Longo, Vuotto & Donelli, 2014). Biofilm formation increases the survival rate of A. baumannii on dry surfaces and may contribute to its. Characterization of biofilm production in different strains of Acinetobacter baumannii and the effects of chemical compounds on biofilm formation. The mechanisms to explain the increased drug resistance of bacteria related with biofilms are various and at least included delayed penetration of the antimicrobial agents into the biofilm and reduced growth rate of the microorganisms within the biofilm (Donlan, 2000). A positive correlation between biofilm formation and antimicrobial resistance in A. baumannii has been confirmed (Badave & Kulkarni, 2015), one study suggested an inverse relationship between biofilm production and meropenem resistance in nosocomial A. baumannii isolates (Perez, 2015). The ability to form a biofilm may affect antibiotic susceptibility and clinical failure, even when the dose administered is in the susceptible range (Kim et al, 2015)
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