In vitro interference of tigecycline at subinhibitory concentrations on biofilm development by Enterococcus faecalis
Microbiology Department, Hospital Central de la Defensa Gómez-Ulla, Madrid, Spain. Journal of Antimicrobial Chemotherapy
(Impact Factor: 5.31).
02/2012; 67(5):1155-8. DOI: 10.1093/jac/dks014
Since biofilm formation is the hallmark of Enterococcus faecalis isolates, the aim of this study was to quantify biofilm formation in the presence of subinhibitory concentrations of tigecycline.
Interference of tigecycline on biofilm formation was spectrophotometrically quantified using 20 biofilm-producing E. faecalis isolates with tigecycline MICs of 0.12 (8 strains) or 0.25 mg/L (12 strains). Biofilm production was measured in antibiotic-free tryptic soy broth supplemented with 1% glucose and compared with biofilm production in the same medium with tigecycline at subinhibitory concentrations (0.25× or 0.5× MIC, similar to trough concentrations in serum or concentrations in the colon after a standard dose) by reading the optical density at 450 nm (OD(450)) after staining with Crystal Violet.
In the presence of subinhibitory tigecycline concentrations, pooled OD(450) values for the 20 strains [median (IQR)] were significantly lower than those for controls: 0.468 (0.379-0.516) for antibiotic-free controls versus 0.295 (0.200-0.395) for 0.25× MIC tigecycline (P < 0.001) and 0.287 (0.245-0.479) for 0.5× MIC tigecycline (P < 0.001), with significant differences between pooled OD(450) values obtained with each concentration of tigecycline (P = 0.022). In 17 out of 20 (85%) strains the OD(450) obtained with 0.25× MIC tigecycline was significantly (P < 0.05) lower than the basal OD(450), while this occurred in 12 out of 20 (60%) strains with 0.5× MIC.
In vitro tigecycline subinhibitory concentrations were able to interfere with biofilm formation by E. faecalis.
Available from: Rasha Bassyouni
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ABSTRACT: In recent years there has been an increase in life-threatening infections caused by Acinetobacter baumannii with multiple antibiotic resistance, especially, in case of biofilm formation. This study aimed at assessing the rate of multidrug resistance (MDR) among A.baumannii isolates, incidence of biofilm formation and evaluating the role of, recently produced medications from 2 different antibiotic classes; tigecycline (glycylcyclines) and moxifloxacin (flouroquinolones), in prevention of Acinetobacter biofilm formation.
Methods: The current investigation was carried out on 30 strains of A. baumannii isolated from different samples at King Khalid University Hospital. Strains were identified and characterized for their antibiotic sensitivity. The MICs tests were conducted to all yields for tigecyclin and moxifloxacin antibiotics. The frequency of biofilm formation and strength was determined by modified microtitre plate method. Finally, prevention of biofilm formation was done using 1X MIC, 2X MIC and 0.5X MIC concentrations of tigecyclin and moxifloxacin.
Results: All A. baumannii isolates were found to be MDR strains, resistance to tested antibiotic discs were found to be 100% in 23.3% of the tested strains, 90% of them were biofilm formers. MIC to tigecyclin was found to be 100% sensitive to all yields with MIC90 and MIC50 equal to 0.5 μg/ml and 0.25 μg/ml respectively. However, 83.3 % of the
strains were resistant to moxifloxacin with MIC90 and MIC50 equal to 32 μg/ml. In testing their ability in avoidance of biofilm formation, unexpectedly, the reduction in biofilm formation were more noticed in the tested concentrations of moxifoloxacin with high significance compared with controls in the 3 concentrations tested with (p < 0.001). While,
tigecycline gave a gradual reduction; double MIC, MIC, 0.5 MIC concentrations showed the significance of (p < 0.001, < 0.01 and < 0.05) respectively.
Conclusion and Recommendations: Most A. baumannii isolates are MDR isolates with high tendency of biofilm formation, tigecyclin was the most effective tested antibiotic used on the planktonic cells while its effect on biofilm was exceeded by moxifloxacin. Further investigation is needed to understand the molecular basis of such an interesting
Life Science Journal 01/2012; 3(9). · 0.17 Impact Factor
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ABSTRACT: The widespread use of antibiotics results in the generation of antibiotic concentration gradients in humans, livestock and the environment. Thus, bacteria are frequently exposed to non-lethal (that is, subinhibitory) concentrations of drugs, and recent evidence suggests that this is likely to have an important role in the evolution of antibiotic resistance. In this Review, we discuss the ecology of antibiotics and the ability of subinhibitory concentrations to select for bacterial resistance. We also consider the effects of low-level drug exposure on bacterial physiology, including the generation of genetic and phenotypic variability, as well as the ability of antibiotics to function as signalling molecules. Together, these effects accelerate the emergence and spread of antibiotic-resistant bacteria among humans and animals.
Nature Reviews Microbiology 05/2014; 12(7). DOI:10.1038/nrmicro3270 · 23.57 Impact Factor
Advances in Experimental Medicine and Biology 01/2015; 831:137-46. DOI:10.1007/978-3-319-09782-4_9 · 1.96 Impact Factor
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