Showing papers by "Majid Eslami published in 2016"

Sensing properties of BN nanotube toward carcinogenic 4-chloroaniline: A computational study

Abstract: The viability of using a BN nanotube for detection of para -chloroaniline molecule was studied by means of density functional theory calculations. The results indicate that the molecule prefers to be adsorbed on the intrinsic BN nanotube from its N atom, releasing energy of 0.65 eV without significant effect on the electrical conductivity of the tube. Thus, para -chloroaniline cannot be detected using this intrinsic nanotube. To overcome this problem, a nitrogen atom of the tube wall was replaced by a Si atom. It was shown that the Si-doped tube not only can adsorb the molecule strongly, but also may detect its presence because of the drastic increase of the electrical conductivity of the tube.

High frequency of extended-spectrum β-lactamase-producing Klebsiella pneumoniae and Escherichia coli isolates from male patients' urine.

Abstract: Background: The number of extended-spectrum -lactamase (ESBL)-producing Enterobacteriaceae reported cases all over the world has continued to increase faster than the other resistance mechanisms, particularly in E. coli and K. pneumoniae. Objectives: This cross-sectional study was designed to assess the prevalence of multidrug resistance of ESBL-producing urine isolates of E. coli and K. pneumoniae collected in Tehran hospitals, as well as the molecular characterizations of some ESBL genes, with an emphasis on occurrence rates by sex. Materials and Methods: A total of 190 E. coli and K. pneumoniae isolates were collected from patients’ urine samples in hospitals from Tehran, Iran during 2009 - 2010, and were screened for antibiotic susceptibility, ESBL phenotype, and presence of blaCTX-M and blaTEM genes. Minimal inhibitory concentration (MIC) for ceftazidime and cefotaxime were made by agar dilution method. Results: The ESBL phenotype was detected in 55.5% of E. coli and 46.4% of K. pneumoniae isolates. Presence of blaCTX-M-1 was dominant in both organisms. The prevalence of blaCTX-M-1 carrying isolates among ESBL-producing K. pneumoniae and E. coli isolates were 49.1% and 85.7%, respectively. Among ESBL-producing isolates, 68.5% of E. coli and 59.3% of K. pneumoniae isolates carried the blaTEM genes, and simultaneous carrying of blaCTX-M and blaTEM genes was observed in 68.5% of E. coli and 33.3% of K. pneumoniae isolates. The resistant rate to ceftazidime, cefotaxime, and cefepime was significantly higher in K. pneumoniae and E. coli isolates from male patients urine samples. A significant higher rate of blaCTX-M-1, blaTEM, and co-blaCTX-M-1-blaTEM genes were seen for E. coli and K. pneumoniae isolates in male patients’ urine. Conclusions: The results indicate that the rates of ESBLs are high in urine E. coli and K. pneumoniae isolates from Tehran hospitals. Also this study indicates that the urine isolates from male patients are significantly more resistant than the female isolates.

Antibiotic Susceptibility Profile, ESBL Production and blaCTX-M1, blaSHV and blaTEM Types Among Escherichia coli Blood Isolates

Abstract: Background: Plasmid and chromosomal extended-spectrum beta-lactamases (ESBLs) have been increasingly spread everywhere and blaCTX-M1 is one predominant beta-lactamase. Objectives: This study was fulfilled to determine the production of ESBL and prevalence of blaCTX-M1, blaSHV, and blaTEM among Escherichia coli blood isolates in Tehran. Patients and Methods: Twenty-three isolates were adopted to be studied during 2015-2016. The antibiotic susceptibility testing was performed using Kirby–Bauer method. The combined disk method was used for the detection of phenotypic ESBL production. The most effective antibiotics were piperacillin, amikacin, and ofloxacin. The minimum inhibitory concentration (MIC) of ceftazidime was determined using micro-broth dilution method. Polymerase chain reaction (PCR) was used for detecting the blaCTX-M1, blaSHV, and blaTEM genes. Results: In the broth dilution test, 19 (82%) isolates showed MIC ≥1, and 18 (78.3%) isolates were ceftazidime resistant. In the combined disk test, 19 (82%) isolates were ESBL producers. The results of the MIC and ceftazidime resistance were the same for ESBL selection. The results of MIC, in fact confirmed the disk diffusion in determining the phenotypic ESBL production. The frequency of blaCTX-M1, blaSHV, and blaTEM genes among blood ESBL producing isolates was 26% (n = 6), 8.6% (n = 2), and 0%, respectively. Isolates that showed higher MIC were positive for these genes. Conclusion: The prevalence of multidrug-resistant blood isolates and ESBL phenotype was high in military hospitals. A low number of blood strains amplified blaCTXM1 and blaSHV type beta–lactamases. There was a relationship between the MIC and the presence of beta-lactamase genes.

Detection of hbla and bal genes in bacillus cereus isolates from cheese samples using the polymerase chain reaction

Abstract: Background: Bacillus cereus is a Gram-positive spore-forming bacterium, which causes food poisoning. Spores enable the persistence of B. cereus in the environment, and B. cereus strains can tolerate adverse environmental conditions, such as temperature and insufficient nutrients. B. cereus causes food poisoning via the production of two enterotoxins. Most isolates produce toxins leading to diarrhea (enterotoxins) and vomiting (emetic forms). Diarrhea is caused by the production of three different heat-labile enterotoxins: HBL, NHE, and cytotoxin K. A heat-stable toxin, cereulide, is responsible for emesis. Objectives: This study aimed to detect enterotoxigenic B. cereus isolates in cheese samples using the polymerase chain reaction (PCR). Materials and Methods: Two-hundred pasteurized (n = 100) and nonpasteurized (n = 100) cheese samples were collected. The initial isolation was performed on PEMBA specific medium. Antibiotic susceptibility testing was performed using several antibiotic disks, according to the guidelines of the Clinical Laboratory and Standards Institute. Specific primers amplifying the hblA enterotoxinencoding gene and bal hemolysin-encoding gene were used for the molecular detection of the toxins. Results: Ten samples were positive for the presence of B. cereus, with both Gram staining and biochemical reactions. All the isolates were resistant to penicillin and ampicillin but susceptible to vancomycin, erythromycin, and ciprofloxacin. Six and three isolates were resistant to tetracycline and trimethoprim-sulfamethoxazole, respectively. The hblA and bal genes were amplified in all the B. cereus isolates. Conclusions: The prevalence of B. cereus among the cheese samples was low. All the isolates were positive for genes encoding the hblA enterotoxin and bal toxin.