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KARAASLAN, ELİF

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Author: Karaaslan, ELİF × Has files: false × Type: Article ×

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    Antibacterial and anti-biofilm activities of melittin and colistin, alone and in combination with antibiotics against Gram-negative bacteria
    (2016-01-01T00:00:00Z) Dosler, Sibel; Karaaslan, ELİF; Gerceker, A. Alev; KARAASLAN, ELİF
    In vitro antibacterial and anti-biofilm activities of antimicrobial cationic peptides (AMPs) melittin and colistin both alone and in combination with antibiotics were evaluated against clinical isolates of Gram-negative bacteria. Minimum inhibitory concentration (MIC) and fractional inhibitory concentration (FIG) index were determined by the microbroth dilution and chequerboard techniques, respectively. The time-kill curve (TKC) method was used for determining the bactericidal activities of AMPs alone and in combination. Measurements of anti-biofilm activities were performed spectrophotometrically for both inhibition of attachment and 24-hour biofilm formation at MIC or subMIC. According to MIC, values, the most active agents against Pseudomonas aeruginosa, Escherichia colt and Klebsiella pneumoniae were colistin, imipenem and ciprofloxacin, respectively. In combination studies, synergistic effects were mostly seen with colistin imipenem against E. coif and K. pneumoniae (50 and 54%, respectively), colistin ciprofloxacin against P. aeruginosa (77%). In TKC studies, synergism was observed with almost all expected combinations, even more frequently than chequerboard method. All of the antimicrobial agents were able to inhibit attachment and 24-hour biofilm formation between 0-57% at 1/10 x MIC and 7-73% at 1 x or 1/10 x MIC, respectively. AMPs seem to be a good candidate for antimicrobial chemotherapy with their antibacterial and anti-biofilm activities as a single agent or in combination with antibiotics.
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    Comparison of antibacterial activities of polymyxin B and colistin against multidrug resistant Gram negative bacteria
    (2019-07-11T00:00:00Z) Doymaz, MEHMET ZİYA; Karaaslan, ELİF; DOYMAZ, MEHMET ZIYA; KARAASLAN, ELİF
    Background: Polymyxin B and colistin have similar structures except for one amino acid. Usually, physicians choose either polymyxin B or colistin for treatment of infections caused by multidrug-resistant (MDR) organisms. The preference is based on previous experience. Not much data are found in the literature comparing the two drugs against the same microorganisms. In this study, we compared in vitro antimicrobial activities of the two polymyxins against a panel of highly resistant and susceptible microorganisms. Methods: Eighty-nine clinical isolates (27 Klebsiella pneumoniae, 31 Acinetobacter baumannii and 31 Pseudomonas aeruginosa) were tested in broth microdilution assays. Time-kill curve experiments were carried out on selected isolates. Results: Significantly lower MICs for polymyxin B than for colistin were found against all species tested including K. pneumoniae (p < .02), A. baumannii (p < .001) and P. aeruginosa (p < .01). The low MICs caused a change in categorical interpretations of only two K. pneumoniae and two P. aeruginosa. Similar results were obtained in time-kill curve experiments with both susceptible and resistant clinical isolates. Conclusions: Significantly lower MICs were found for polymyxin B against three of the most critical MDR species. Even though differences in categorical interpretations were not striking, lower MICs might be a critical consideration in clinical management of select cases where the concentration of these toxic antibiotics matters because of underlying co-morbidities. These results provide support to previous suggestions that re-consideration of breakpoint interpretations for polymyxins might be needed.