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.
The toxin-antitoxin (TA) system is a regulatory system where two sets of genes encode the toxin and its corresponding antitoxin. In this study, the prevalence of TA systems in independently isolated clinical isolates of Enterococcus faecium and Enterococcus faecalis was determined, the dominant TA system was identified, different virulence genes in E. faecium and E. faecalis were surveyed, the level of expression of the virulence and TA genes in normal and stress conditions was determined, and finally their associations with the TA genes were defined. Remarkably, the analysis demonstrated higBA and mazEF in all clinical isolates, and their locations were on chromosomes and plasmids, respectively. On the other hand, a quantitative analysis of TA and virulence genes revealed that the expression level in both genes is different under normal and stress conditions. The results obtained by anti-mazF peptide nucleic acids demonstrated that the expression level of virulence genes had decreased. These findings demonstrate an association between TA systems and virulence factors. The mazEF on the plasmids and the higBA TA genes on the chromosomes of all E. faecium and E. faecalis strains were dominant. Additionally, there was a decrease in the expression of virulence genes in the presence of anti-mazF peptide nucleic acids. Therefore, it is suggested that mazEF TA systems are potent and sensitive targets in all E. faecium and E. faecalis strains.
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.