مجله دانشگاه علوم پزشکی اردبیل
پیاپی 45 (پاییز 1391)

Ethambutol is one of the four main drugs in treatment of tuberculosis. The most common mutation associated with this drug resistance usually occurs in codon 306 of embB. The aim of this study was to detect ethambutol resistance using Allele-Specific PCR and Spoligotyping in various subtypes of Mycobacterium tuberculosis.

140 sputum specimens were collected from suspected TB patients. They were digested and decontaminated using Pettrof method before culturing them on LJ medium. Drug susceptibility testing was performed on 106 culture positive specimens using proportional method. DNA was extracted from the isolated organisms and subsequently subjected to Allele-Specific PCR to detect any mutationin embB306. Spoligotyping was then used to determine the subtypes.

Out of 106 cultures positive samples، 36 samples (33. 9%) showed resistance to ethambutol using proportional method. Allele-Specific PCR assay identified 93 as sensitive and 13 (27. 6%) as resistant strains. The results of PCR were in agreement with result of proportional method. The PCR method revealed that 61. 5% of mutation occurred in the first and 38. 5% in third nucleotides. Spoligotyping differentiated Mycobacterium tuberculosis strains into Beijing (10; 9. 4%)، Bovis (2; 1. 8%)، CAS (24; 22. 6%)، EAI (1; 0. 9%)، Haarlem (27; 25. 4%)، LAM (5; 4. 7%)، Manu (5; 4. 7%)، T (27; 25. 4%) and U (2; 1،8%) families. The high frequency of mutation in embB gene was belonged to Haarlem، CAS and T subfamilies.

Based on results current study، mutations in the genes other than embB might have occurred in the resistant strains that gave negative result in Allele-Specific PCR assay. Therefore other mechanisms of resistance to this antibiotic should be investigated.

Several studies have shown that Glucocorticoids affect learning and memory processes by influences on limbic structures such as amygdala. The amygdala is an important region for memory formation. Considering the existence of the muscarinic acetylcholine receptors in the basolateral amygdala (BLA)، the aim of the present study was to investigate the effect of intra-BLA microinjection of pilocarpine on the effect of dexamethasone on memory retrieval.

As a model of learning، using a step-through apparatus، inhibitory avoidance was used for assessment of long-term memory in 80 adult male Wistar rats. All animals were bilaterally implanted with cannulas into the BLA and were trained and tested (with 24 h interval) 7 days after surgery. Memory retrieval was evaluated by recording of the step-through latencies and the time spent in dark chamber of apparatus in the testing day.

Pre-test subcutaneous (s. c) administration of dexamethasone (2 mg/kg) impaired memory retrieval in animals when trained 24 h in advance. Co-pretest microinjection of different doses of pilocarpine (1، 2 μg/rat، intra-BLA)، a muscarinic acetylcholine receptor agonist، with the dexamethasone (2 mg/kg، s. c) caused enhancement of memory retrieval.

Results of this research indicate that impairment effect of dexamethasone on memory processes may be mediates by decrease of mechanisms of BLA muscarinic cholinergic.