investigation of aac[6']-le-aph[2"]-la gene in MDR and HLGR enterococcus faecalis and E. faecium strains isolated from clinical samples

Enterococci are important nosocomial pathogens. Multiple drug resistance [MDR] is common among Enterococci and presents difficulties for treatment. High level gentamicin resistance [HLGR] in enterococci, is a significant therapeutic problem. Bactericidal antimicrobial activity usually is obtained by the synergistic combination of a cell wall active agent such as penicillin or glycopeptide with an aminoglycoside. Enterococci can acquire aminoglycoside resistance genes that mediate production of aminoglycoside-modifying enzymes, which eliminate this synergistic bactericidal effect. The most clinically important HLGR genes is aac [6']-le-aph [2"]-la. In the present study, a total of 437 clinical samples from 5 hospital and 3 private laboratory in Tehran, from azar 1384 to Tir 1385, were collected and 300 enterococcal isolates recovered all of the strains were identified to the species level by conventional biochemical tests and assayed for their susceptibility to 11 antibiotics, ampicillin, tetracycline, erythromycin, ciprofloxacin, high dose gentamicin, vancomycin, cotrimoxazole, quinopristin -daifopristin [synercid], linezolid, teicoplanin and nitrofurantoin by disk diffusion method. Gentamicin MIC was accomplished for HLGR strains. The most frequent species was E. faecalis [81.3%] and then E. faecium [18.7%]. MDR strains were detected in 50% and 95% of E.faecalis and E.faecium, respectively. The number of HLGR strains for E.faecalis and E.faecium were found to be 19.5% and 23.5%, respectively. All HLGR strains showed MIC>1024 microg/mL The PCR results showed that 83% and 100% of E.faecalis and E.faecium strains carried aac[6']-le-aph[2"]-la gene as detected by PCR. The present study indicates high rate dissemination of aac[6']-le-aph[2"]-la gene, suggesting the possible mechanism of transfer of gentamicin resistant genes within the enterococcal population and in this case probable need to new aminoglycosides or other antibiotics would be predictable

Effect of heat treatment on marginal integrity of metal-ceramic casting in base metal alloy

Increasing PFM restorations longevity is one of the objectives in restorative dentistry and marginal fitness is an important factor to gain this purpose. In this study the effects of heat treatment on marginal fitness using both base metal and precious alloys are surveyed. Forty wax pattern on 40 standard model has been provided. Thirty of them with base alloy and 10 with precious alloy were cast. After divesting, marginal gap for each model have been measured [reflective microscope x 200]. Then samples were divided into 4 groups as follows: Group 1: Cold working- oxidizing- marginal gap measuring. Group 2: Reinvesting the model- heat treating at 1100°C for 20 minutes- ensuing stages same as group 1. Group 3: These samples were made from precious alloy and all procedures were followed as group 2. Group 4: Oxidation- gap measurement - ensuing stages same as group 1. Data were analyzed by ANOVA, T-test and Duncan test. Mean marginal gap in group I was the most and in group III was the least. Mean marginal gap in group II was Lesser than IV and in base alloy was more than precious. Heat treatment of metal framework make marginal adaptation better. If metal framework is reinvested and heat treated before any cold working and oxidization, marginal adaptation will improve