engleski

Do phenotypes resistances of Acinetobacter baumannii have an impact on the ability to of clinical isolate produce biofilm?

Objectives: Acinetobacter baumannii is an emerging hospital pathogen, responsible for dramatically increase of carbapenem resistance pattern and hospital acquired infections in the Croatia. Such data have prompted multicenter research among clinical isolates of A. baumannii from southern Croatia. The scope of this study was to investigate if clinical isolates of A. baumannii had various abilities to form biofilm depending on resistance to antibiotics. Methods: This study has analyzed in total 100 prospectively sampled isolates of A. baumannii. After isolation, initial identification was made using commercial tests for the identification of non-fermenting bacteria. Isolates of A. baumannii have confirmed with the presence of an OXA-51 type β-lactamase (specific to A. baumannii), performed by polymerase chain reaction. The susceptibility of isolates to antibiotics was tested by applying a disk diffusion method and by determining the minimum inhibitory concentrations (MICs). The ability to form biofilm in vitro was determined from overnight cultures diluted in Luria Bertani medium. Biofilm was stained with 0.5% crystal violet and quantified at 570 nm. The OD (optical density) corresponds to the amount of biofilm formed by bacteria. The interpretation for OD values: non-biofilm-forming (<0.4), low biofilm-forming (0.4–1.0) and strong biofilm-forming (>1.0). The ability to form biofilm was investigated in comparison with the resistance pattern. The statistical relevance of differences was conducted in the SPSS 17.0 software (SPSS Inc., Chicago, IL, USA). The level of the statistical confidence was determined at P<0.05. Results: Out of the total number of tested isolates, 1/4 of them did not form biofilm, while 3/4 of isolates were biofilm producers. The ability to form biofilm was mostly dependent on the phenotype of sensitivity and resistance to ampicillin/sulbactam, carbapenems and amikacin. The majority of isolates susceptible or intermediate susceptible to the above mentioned antibiotic have a low or strong ability to form biofilm, respectively, but large proportions of isolates resistant to the above mentioned antibiotic do not form any biofilm. Conclusion: Such observations allow us to conclude that the phenotype of resistance of A. baumannii has an impact on the biofilm producing. Moreover, isolates susceptible or intermediate susceptible to antibiotics are more prone to form biofilm in order to use that biofilm to protect themselves from antibiotics.

Acinetobacter baumannii; antibiotics; resistance; biofilm

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