Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleAçık Erişim2016Kinetic characterization of GES-22 β-lactamase harboring the M169L clinical mutation
Saral, Aysegul; Leonard, David A; Duzgun, Azer Ozad; Cicek, Aysegul Copur; June, Cynthia M; Sandalli, Cemal
The class A β-lactamase GES-22 has been identified in Acinetobacter baumannii isolates in Turkey, and subsequently shown to differ from GES-11 by a single substitution (M169L). Because M169 is part of the omega loop, a structure that is known to have major effects on substrate selectivity in class A β-lactamases, we expressed, purified and kinetically characterized this novel variant. Our results show that compared with GES-116×His, GES-226×His displays more efficient hydrolysis of penicillins, and aztreonam, but a loss of efficiency against ceftazidime. In addition, the M169L substitution confers on GES-22 more efficient hydrolysis of the mechanistic inhibitors clavulanic acid and sulbactam. These effects are highly similar to other mutations at the homologous position in other class A β-lactamases, suggesting that this methionine has a key structural role in aligning active site residues and in substrate selectivity across the class.
- MakaleAçık Erişim2016Comparison of verona integron-borne metallo-β-lactamase (VIM) variants reveals differences in stability and inhibition profiles
Makena, Anne; Düzgün, Azer Ö.; Brem, Jürgen; McDonough, Michael A.; Rydzik, Anna M.; Abboud, Martine I.; Saral, Ayşegül; Çiçek, Ayşegül Č.; Sandalli, Cemal; Schofield, Christopher J.
Metallo-β-lactamases (MBLs) are of increasing clinical significance; the development of clinically useful MBL inhibitors is challenged by the rapid evolution of variant MBLs. The Verona integron-borne metallo-β-lactamase (VIM) enzymes are among the most widely distributed MBLs, with>40 VIM variants having been reported. We report on the crystallographic analysis of VIM-5 and comparison of biochemical and biophysical properties of VIM-1, VIM-2, VIM-4, VIM-5, and VIM-38. Recombinant VIM variants were produced and purified, and their secondary structure and thermal stabilities were investigated by circular dichroism analyses. Steady-state kinetic analyses with a representative panel of β-lactam substrates were carried out to compare the catalytic efficiencies of the VIM variants. Furthermore, a set of metalloenzyme inhibitors were screened to compare their effects on the different VIM variants. The results reveal only small variations in the kinetic parameters of the VIM variants but substantial differences in their thermal stabilities and inhibition profiles. Overall, these results support the proposal that protein stability may be a factor in MBL evolution and highlight the importance of screening MBL variants during inhibitor development programs.
- Editöre MektupAçık Erişim2016A novel integron gene cassette harboring VIM-38 metallo-β-lactamase in a clinical pseudomonas aeruginosa isolate
Beriş, Fatih Şaban; Akyildiz, Esma; Düzgün, Azer Özad; Coşkun, Umut Safiye Say; Sandalli, Cemal; Çiçek, Ayşegül Çopur
- MakaleAçık Erişim2015Distribution of β-Lactamase Genes Among Carbapenem-Resistant Klebsiella pneumoniae Strains Isolated From Patients in Turkey
Iraz, Meryem; Düzgün, Azer Ozad; Sandalli, Cemal; Doymaz, Mehmet Ziya; Akkoyunlu, Yasemin; Saral, Aysegul; Peleg, Anton Y.; Özgümüs, Osman Birol; Beris, Fatih Saban; Karaoglu, Hakan
Background: The emergence of carbapenem-resistant Klebsiella pneumoniae poses a serious problem to antibiotic management. We investigated the beta-lactamases in a group of carbapenem-resistant K. pneumoniae clinical isolates from Turkey. Methods: Thirty-seven strains of K. pneumoniae isolated from various clinical specimens were analyzed by antimicrobial susceptibility testing, PCR for the detection of p-lactamase genes, DNA sequencing, and repetitive extragenic palindronic (REP)- FOR analysis. Results: All 37 isolates were resistant to ampicillin, ampicillin/sulbactam, piperacillin, piperacillin/tazobactam, ceftazidime, cefoperazone/sulbactam, cefepime, imipenem, and meropenem. The lowest resistance rates were observed for colistin (2.7%), tigecycline (11%), and amikacin (19%). According to FOR and sequencing results, 98% (36/37) of strains carried at least one carbapenemase gene, with 32 (86%) carrying OXA-48 and 7 (19%) carrying NDM-1. No other carbapenemase genes were identified. All strains carried a CTX-M-2-like beta-lactamase, and some carried SHV- (97%), TEM- (9%), and CTX-M-1-like (62%) beta-lactamases. Sequence analysis of bla(TEM) genes identified a bla(TEM-166) with an amino acid change at position 53 (Arg53Gly) from bla(TEM-1b), the first report of a mutation in this region. REP-FOR analysis revealed that there were seven different clonal groups, and temporo-spatial links were identified within these groups. Conclusions: Combinations of beta-lactamases were found in all strains, with the most common being OXA-48, SHV, TEM, and CTX-M-type (76% of strains). We have reported, for the first time, a high prevalence of the NDM-1 (19%) carbapenemase in carbapenem-resistant K. pneumoniae from Turkey. These enzymes often co-exist with other beta-lactamases, such as TEM, SHV, and CTX-M beta-lactamases.
- MakaleYalnız künye2014Characterization of novel VIM carbapenemase, VIM-38, and first detection of GES-5 carbapenem-hydrolyzing β-lactamases in Pseudomonas aeruginosa in Turkey
Iraz, Meryem; Duzgun, Azer Ozad; Cicek, Aysegul Copur; Bonnin, Remy A.; Ceylan, Aysenur; Saral, Aysegul; Nordmann, Patrice; Sandalli, Cemal
Pseudomonas aeruginosa isolates were collected form a Turkish hospital. Antimicrobial susceptibility was performed using the Vitek 2 Compact system, and 24 isolates were categorized as multidrug resistant (n = 18), extensively-drug resistant (n = 5), or pan-drug resistant (n = I). PCR and DNA sequence analysis revealed that 1 strain possessed the bla(GES-5) and another carried a novel bla(VIM) variant, named VIM-38. This new gene exhibited 1 amino acid substitution (Ala265Val) in comparison to its closest variant, VIM-5. Both VIM encoding genes were clones and demonstrated similar susceptibility profile when expressed in identical background. The presence of VIM-38 increases the diversity of carbapenemases in Turkey. (C) 2014 Elsevier Inc. All rights reserved.
- MakaleAçık Erişim2013Detection of class 1 integron in Acinetobacter baumannii isolates collected from nine hospitals in Turkey
ÇIÇek, Ayşegül Çopur; Düzgün, Azer Özad; Saral, Ayşegül; Kayman, Tuba; ÇIzmecI, Zeynep; Balci, Pervin Özlem; Dal, Tuba; Firat, Mehmet; Tosun, Ismail; Alitntop, Yasemin Ay
Objective: To investigate the antibiotic resistance genes inserted into class 1 and class 2 integrons in Acinetobacter baumannii (A. baumannii) isolates obtained from nine different cities in Turkey. Methods: A collection of 281 A. baumannii clinical isolates were collected from nine diferent state hospitals in Turkey and were confirmed as A. baumannii by conventional biochemical, API testing and bla-OXA-51 specific PCR. The isolates were examined by PCR for existence of class 1 and 2 integron gene cassettes. Results: They were characterized by antimicrobial susceptibility testing and the highest resistance rates were determined for piperacillin (90.03%), ciprofloxacin (87.54%), cefepime and trimethoprim/sulfamethoxazole (81.13%). The lowest resistance rates was for cefotaxime (3.55%). class I integrons were detected in 6.4% (18/281) of A. baumannii strains and no class 2 integron was detected. The gene cassettes of class 1 integrons AacC1-AAC(3) I-aadA1, AacC1-aadA1, AAC(3)-I, AAC(3)-I -AAC(3)-I -aadA1, TEM-1, AAC(3)-I-aadA1 - AAC(3)-I -AAC(3)-I, AAC(3)-I -AAC(3)-I -AAC(3)-I -aadA1, AAC(3)-I - aadA1, AAC(3)-I-AAC(3)-I, AAC(3)-I-aadA1-AAC(3)-I-aadA1, AAC(3)-I-AAC(3)-I-aadA1-AAC(3)-I-aadA1 were detected in eighteen strains. The aac genes family were most frequently found integrated into the class 1 integrons and it was followed by aadA genes and TEM-1 genes. Conclusions: This is an extensive study on the distribution of class 1 integron among A. baumannii in Turkey. In addition to these, two new alleles were observed. Their percentage rates of similarity to other cassettes are 95% aadA1 (TKA18) and 89% aadA1 (ANKA3).