TR-Dizin Açık Erişimli Yayınlar

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Author: search.filters.author.Basustaoglu, AhmetHas files: Yes

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    In vitro Activity of Delafloxacin against Methicillin-Resistant Staphylococcus aureus Isolated from Various Clinical Specimens
    (2021) Mirza, Hasan Cenk; Basustaoglu, Ahmet; Yanik Yalcin, Tugba; 0000-0002-8853-3893; F-1232-2015
    Introduction: Delafloxacin is a novel fluoroquinolone which has anionic and weak acid character at neutral pH. Activity of delafloxacin is reported to be increased in acidic environments. Many infections are characterized by acidic pH. Staphylococcus aureus is a microorganism which can survive and multiply in mildly acidic environments. The aim of this study was to compare the activity of delafloxacin and other fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) against MRSA isolates at neutral (7.4) and acidic (5.5) pH. Materials and Methods: A total of 51 MRSA isolated from various clinical specimens were included in the study. Disk diffusion method was used for antimicrobial susceptibility testing. The pH of Mueller Hinton Agar was adjusted to 7.4 or 5.5, and used as the medium for antimicrobial susceptibility testing. EUCAST breakpoints were used for ciprofloxacin, levofloxacin and moxifloxacin. FDA breakpoints were used for delafloxacin. Results: The most active fluoroquinolones against MRSA isolates at neutral pH were delafloxacin and moxifloxacin. Delafloxacin and moxifloxacin susceptibility rates of isolates were same (82.4%) at neutral pH. Of the isolates, 9.8% and 17.6% were resistant to delafloxacin and moxifloxacin, respectively. Four moxifloxacin-resistant isolates were categorized as intermediate to delafloxacin. Of the isolates, 76.5% and 78.4% were 'I - susceptible, increased exposure' to ciprofloxacin and levofloxacin, respectively. Of the isolates, 23.5% and 21.6% were resistant to ciprofloxacin and levofloxacin, respectively. At acidic pH; ciprofloxacin, levofloxacin and moxifloxacin susceptibility rates of isolates were not changed. However, all delafloxacin resistant/intermediate isolates at neutral pH became susceptible to delafloxacin at acidic pH. Conclusion: Delafloxacin was the most active fluoroquinolone against MRSA isolates at acidic pH. Based on our findings, delafloxacin may represent a treatment option for MRSA infections characterized by low pH.
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    Determination of Biofilm Formation Properties of Methicillin Sensitive and Resistant Staphylococcus aureus Isolates by Conventional and Molecular Methods
    (2020) Hortac Istar, Elvan; Aliskan, Hikmet Eda; Basustaoglu, Ahmet; 0000-0002-2571-0637; 0000-0001-9060-3195; 32723278; AAI-8926-2021; AAE-2282-2021
    Biofilm-related infections are considered as among the foremost causes of treatment failure nowadays. One of the most common causes of biofilm-related infections is Staphylococcus aureus. It becomes extremely difficult to determine the appropriate treatment protocol while biofilm-related infections are coexisting with bacterial methicillin resistance. The aim of this study was to observe the potential of biofilm formation of methicillin-sensitive and -resistant S.aureus strains isolated from different clinical specimens and to determine reliable and effective methods for biofilm detection. A total of 200 S.aureus strains (100 methicillin-resistant and 100 methicillin-susceptible) isolated from 107 wound, 93 blood and catheter specimens, which were accepted as causative agents, included in the study. In order to determine the methicillin sensitivity, oxacillin minimal inhibitory concentration value obtained by an automated system and cefoxitin disc diffusion method were evaluated together. Biofilm formation was investigated by modified Christensen (MC), MTT, BioTimer and Congo Red Agar (CRA) methods, and the presence of ica operon responsible for biofilm formation was also observed by polymerase chain reaction. It has been shown that methicillin-resistant isolates produce biofilms in a shorter time and higher rate, and their biofilm structure is denser than methicillin-sensitive isolates in all MC, MTT and BioTimer methods. There was no difference between blood and wound isolates in biofilm formation. The most sensitive and specific conventional methods were MTT and BioTimer methods respectively. There was no significant difference between the isolates containing a gene region of icaADBC operon and the biofilm forming isolates according to MC, MTT, BioTimer and CCA methods. There was a high correlation between the presence of biofilm and ica positivity, and the tendency to form biofilm augmented as the number of ica genes increased. It has been emphasized that more virulent strains such as methicillin-resistant S.aureus have a higher tendency to form biofilm, and these two resistance mechanisms have been shown to support each other as cascade. ica detection may be an important reagent in itself for the detection of virulent strains, thus detection of the ica presence may be an early marker of treatment decisions, determination of protection strategies, and struggle with biofilm-related infections. In cases where molecular methods are not available, the existence of quick, easy-to-apply and reliable conventional methods to detect biofilm formation is extremely important. All conventional methods used in this study seem to be sufficient in this respect. MC and MTT methods stand out in terms of biofilm quantitation. BioTimer method is a very new and remarkable test used to detect biofilm formation. In conclusion, determining the potential of biofilm formation of colonizing or causative agents and taking essential precautions before interventional procedures will decrease biofilm related infections and related morbidity and mortality.