To date, the most important genes responsible for tetracycline resistance among Acinetobacter baumannii isolates have been identified as tet A and tet B. This study was carried out to determine the rate of resistance to tetracycline and related antibiotics, and mechanisms of resistance.
Antimicrobial susceptibility and ESBLs genes of 42 imipenem resistant A. baumannii carried out by DDST and PCR. The most antimicrobial agents against A. baumannii strains, harboring blaOXA-23-like carbapenemases, were meropenem (33.4 percent), piperacillin-tazobactam (23.9 percent), ceftazidime (14.3 percent) and gatifoxacin (19.1 percent), respectively. All the 42 isolates harbored the blaTEM gene, but the bla SHV and VEB genes were not present among all the isolates. With the exception of seven isolates, all the A. baumannii strains harbor blaTEM showed ESBL positivity in DDST. The result of this study show that resistance against antimicrobial agents, especially carbapenems, has increased and that blaTEM harboring A. baumannii strains can be help the blaOXA-like carbapenemase genes to code for resistance against carbapenem antibiotics.
In this study, the catalase-like activity of monomeric tau protein was reported in the presence of of zinc (Zn(II)) ions at low pH value. Monomeric tau protein contains two SH groups that are a target of disulfide bond formation. However these SH groups are able to interact with Zn(II) ion at pH 7.2 which creates a thiol bond as a mimetic model of chloroperoxidase active site which performs catalase like activity at low pH. Zn(II)/tau protein complex decomposed H2O2 with a high rate (Vm) as well as an efficient turn oven number (kcat) at pH 3. This remarkable catalase like activity is may be attributed to the conformational reorientation of protein at low pH. Circular dichroism (CD) studies did not demonstrate any secondary structural changes of tau protein after addition of Zn(II) ions at pH 7.2. In addition, tau protein shows identical CD bands at pH 7.2 and 3. Moreover, fluorescence quenching of tau by Zn(II) at pH 7.2 was initiated by complex formation rather than by dynamic collision. A significant red shift (6nm) was observed in the emission maximum of the fluorescence spectra when the protein was dissolved at pH 3 compared to pH 7.2. This conformational change can provide information regarding the rearrangements of the protein structure and exposure of Cys-Zn(II) group to the solvent which induces easy access of active site to H2O2 molecules and corresponding enhanced catalytic activity of Zn(II)/tau protein complex. This study introduces tau protein as a bio-inspired high performing scaffold for transition metal encapsulation and introducing an engineered apoprotein-induced biomimetic enzyme.
Methicillin-resistant Staphylococcus aureus (MRSA) is a pathogen of public health importance. The prevalence of MRSA and its antimicrobial resistance pattern, as well as SCCmec and spa types, remain unclear both in the community and in the hospitals of the western region of Iran.