Characterization of tetracycline resistance genes in tetracycline-resistant Enterobacteriaceae obtained from a coliform collection

Tetracycline resistance has been used as the key determinant to monitor resistance genes in natural environments such as rivers, lakes or seawater. The aim of this study was evaluate the frequency of tetA, tetB, tetC, tetD and tetE genes in 52 tetracycline-resistant Enterobacteriacea isolated from river water in the North East Black Sea Region of Turkey. In 52 tetracycline-resistant strains, resistance was mediated by tetA in eight (15.3%) strains, tetB in ten (19.2%) strains and both tetA and tetB in one (1.9%) strain. No tetC, tetD or tetE-mediated resistance was detected. In conclusion, the river water may be considered as a reservoir for the antibiotic resistance genes and the people living in this area may be under risk. To our knowledge, this is the first report for molecular characterization of tetracycline resistance in Enterobacteriaceae of river water origin in Turkey. © 2010 Springer Science+Business Media B.V

Cloning, expression, purification and characterisation of a thermostable chitinase from Bacillus licheniformis A1

The chitinase B gene (ch/B65) of Bacillus licheniformis A1 (BlicA1) isolated from Diyadin hotspring in Turkey was cloned and sequenced. The gene is 1779 bp long and encodes a protein 592 amino acids with a 35-amino acid signal peptide at N-terminal. The gene has 99% percent similarity to chiB gene of Bacillus licheniformis under the GenBank number AY205293. The gene without signal peptide was overexpressed in Escherichia coli and the recombinant protein purified by nickel affinity chromatography. The activity of enzyme was shown on SDS-PAGE with the flourogenic substrate 4-methylumbelliferyl ß-D-N,N?-diacetylchitobioside. Kinetic characterisation of the enzyme was performed at 65 °C by using chromogenic substrate p-nitrophenyl N,N?-diacetyl-ß-D-chitobioside, and Km and V max were found to be 0.02 ?M and 1017 U/mg protein, respectively. Enzyme has maximal activity at pH 6.0 and was stable over a broad pH range of 5.0-9.0 for 24 h at room temperature and 4 h at 65 °C. Enzyme was 60% stable at 65 °C for 1.5 h. The inhibition or activation of some substances on the activity of enzyme was determined. High kinetic properties of enzyme open the possibility of an extensive structural and enzyme-substrate interaction studies

Prevalence of integrons and a new dfrA17 variant in Gram-negative bacilli which cause community-acquired infections

PubMed: 20236427A hundred and eleven Gram-negative bacilli from community-acquired infections were characterized by antimicrobial susceptibility testing, screened for class 1 and 2 integrons, and statistically evaluated for the association between antibiotic profile and the presence of integrons. The frequency with which integrons were harbored was 28.8%. Three E. coli strains contained a dfrA17 variant inserted in a class 1 integron. Results of PFGE indicated that some E. coli strains carrying integrons were clonally related. Carriage of gene cassettes was significantly associated with resistance to certain antibiotics (P < 0.05). © 2010 The Societies and Blackwell Publishing Asia Pty Ltd

Molecular analysis of antimicrobial resistance in Yersinia ruckeri strains isolated from rainbow trout (Oncorhynchus mykiss) grown in commercial fish farms in Turkey

In this study, molecular characterization of antimicrobial resistance of 116 Yersinia ruckeri strains isolated from rainbow trout (Oncorhynchus mykiss) with enteric redmouth disease (ERM) in commercial fish farms in the Northern and Eastern regions of Turkey was performed. The putative Y ruckeri strains isolated were confirmed by PCR assays specific to the 16S rRNA gene of bacterium Y. ruckeri. Eighty-six (74.1%) strains were identified to belong to serovar O1 by agglutination test in which type O1 antibody was used. No strains carried antimicrobial gene cassettes inserted into intégrons. Neither TEM- nor SHV-type ß-lactamase gene was found in ampicillin-resistant strains (33/116). tetA and tetB genes were screened in 41/116 oxytetracycline-resistant strains by PCR, and it was found that 21 (51.2%) carried a tetA and/or tetB gene. We conclude that the antimicrobial resistant Y ruckeri strains may act as a reservoir of antimicrobial resistance genes within fish farm environments

Comparison of DIG-11-dUTP utilization by Geobacillus caldoxylosilyticus TK4, Mycobacterium tuberculosis and Escherichia coli DNA polymerases

DNA polymerases are used for many applications and we comparatively investigated DNA synthesis activity of DNA polymerase I enzymes of Geobacilluscaldoxylosilyticus TK4, Escherichia coli and Mycobacterium tuberculosis with DIG-11-dUTP using synthetic DNA substrates. We showed that Gca polymerase I and Klenow Fragment (KF) used DIG-11-dUTP instead of dTTP almost at the same ratio, but more efficiently than Mtb polymerase I. We considered that Gca polymerase I could be efficiently used to label a DNA oligonucleotide either internally or at the 3?-terminus by DIG-11-dUTP for the generation of non-radioactive labeled DNA substrates at higher temperature than KF. All three polymerases could not elongate the primer terminus after adding ddNTPs into DNA that is characteristic for all known DNA polymerase I enzymes. © Springer Science+Business Media B.V. 2009.Karadeniz Teknik Üniversitesi: BAP-2005.111.004.1 Türkiye Bilimsel ve Teknolojik Araştirma Kurumu: TUBİTAK-105T216Acknowledgment This study was supported by grants from The Scientific and Technical Research Council of Turkey (TUBİTAK-105T216) and Karadeniz Technical University (BAP-2005.111.004.1) and a scholarship to C. Sandalli from TUBİTAK

Klinik Örneklerden izole Edilen Trimetoprim-Sülfametoksazole Dirençli Stenotrophomonas maltophilia Suşlarinda ntegron, sul 1-2 ve dfr Genlerinin Araştirilmasi

PubMed: 24819258Stenotrophomonas maltophilia, which is a non-fermentative gram-negative bacillus, has an increasing importance in nosocomial and opportunistic infections. Since it exhibits resistance to numerous broad-spectrum antibiotics such as aminoglycosides, beta-lactams and tetracyclines, it may considerably limit empirical treatment options. Trimethoprim-sulfamethoxazole (SXT) is recommended as the first-line therapy in the treatment of S.maltophilia infections thanks to its high potency and usefulness in a range of patients. In recent years, however, studies In different geographical regions have started to report resistance to SXT. In this study, we aimed to investigate the genes sul1, sul2, dfrA9, dfrA10, dfrA20 and class I, class II integran gene cassettes which are known to play role In SXT resistance among SXT-resistant S.maltophilia strains. A total of 618 S.maltophilia strains isolated from various clinical samples of 339 patients between January 2006 and October 2011 at the laboratory of Medical Microbiology Department, Faculty of Medicine, Karadeniz Technical University, Trabzon, Turkey, were included in the study. The isolates were identified by both conventional methods and the Phoenix automated identification system (Becton Dickinson, USA). SXT resistance was determined in the isolates of 32 patients (32/339, 9.4%) by both the automated system and agar dilution method of them 29 (90.6%) were hospital-acquired, and 3 (9.4%) were community-acquired. The genes which are known as SXT resistance determining genes including sul1, sul2, dfr genes, and class I and class II integran gene cassettes were analyzed by using specific primers with polymerase chain reaction in the 32 SXT-resistant isolates. Subsequently, nucleotide sequence analysis of the amplified materials was performed. As a result of this assay, the presence of class I integran gene cassette and sul1 gene were detected in one isolate. Nucleotide sequence analysis of the gene cassette revealed oxacilinase (oxo2) type of beta-lactamase, an aminoglycoside 6'-N-acetyltransferase [aac(6')-llc], leading to resistance of aminoglycosides, and a quaternary ammonium compounds resistance gene (gocF), respectively. In conclusion, to best of our knowledge the sequences of class I integran gene cassette including oxa2, aac(6')-llc, gocF genes were identified in S.maltophilia for the first time. It should be kept in mind that the co-presence of a class I integran gene cassette and the sul1 gene in S.maltophilia may lead to the development of multi-drug resistance and may act as a potential source for the dissemination of resistance

Histologic and histomorphometric comparison of immediately placed hydroxyapatite-coated and titanium plasma-sprayed implants: A pilot study in dogs

The purpose of this pilot study was to make a histologic and histomorphometric comparison of hydroxyapatite- (HA) coated and titanium plasma-sprayed (TPS) root-form implants that were placed in 2 mongrel dogs immediately after extraction of mandibular premolars. After 8 weeks of healing, the implant-containing segments of the mandible were removed en bloc and bone blocks including implants were sectioned. Histologic and histomorphometric analyses were performed by evaluating bone sections. The mean bone contact percentage of HA-coated implants was 61.84 +/- 7.84%, with a range of 52.09% to 75.7%, and the mean bone contact percentage of TPS implants was 51.35 +/- 12.1%, with a range of 30.1% to 70.6%. This pilot study suggests that HA-coated implants placed into fresh extraction sockets can achieve better bone contact than TPS implants, but there was evidence that the surface of the HA layer can be resorbed, so long-term stability of HA coatings in immediate implantation must be investigated