Background: According to the studies, Iran’s per capita antibiotic consumption is remarkable. Since the emergence of Antibiotic Resistant Organisms (AROs) is considered a global problem in the community and hospitals, this study aimed to investigate the pattern of antibiotic resistance in Gram-negative bacteria isolated from patients in an academic and a non-academic hospital in Arak, Iran.

Materials and Methods: This descriptive cross-sectional study included all specimens referred to the microbiology laboratory at Amir Al-Momenin Hospital (academic hospital) and Imam Khomeini Hospital (non-academic hospital) in a one-year period from June 2012 to June 2013. The susceptibility of the isolated Gram-negative bacteria against the important antibiotics used in clinical practice was determined using the disk diffusion method.

Results: A total of 846 specimens were collected from patients in the two hospitals where 520 (61.5%) were Gram-negative bacteria, of which 63.3% were E. coli. The prevalence of Gram-negative organisms in the academic and the non-academic hospital was measured 79.8% and 20.2%, respectively (p=0.097). It was also determined that there is a significant difference between the two hospitals in the prevalence of ESBL (Extended-Spectrum Beta-Lactamase) Gram-negative bacteria (p=0.003).

Conclusion: There was a significant difference between the two hospitals in the prevalence of ESBL Gram-negative bacteria. Therefore, conducting regional surveillance programs to examine the patterns of antibiotic resistance is recommended.

Background: This study aimed to examine the antibacterial effect of Polyamidoamine-G4 dendrimer on Escherichia coli, Enterobacter cloacae, Bacillus subtilis and Staphylococcus aureus.

Materials and Methods: In this experimental study, the antibacterial effects of Polyamidoamine-G4 dendrimer were studied by disc diffusion and micro-dilution method. Different concentrations of Polyamidoamine-G4 inoculated onto blank disks and were placed in Mueller-Hinton agar media. Zone of inhibition was investigated by bacterial inoculation according to the McFarland standard 0.5. Minimum inhibitory concentration and minimum bactericidal concentration of Polyamidoamine-G4 dendrimer were determined by micro-dilution method in nutrient broth culture.

Results: Zone of inhibition in concentration 500 &mug/ml of Polyamidoamine-G4 dendrimers for Escherichia coli, Enterobacter cloacae, Bacillus subtilis and Staphylococcus aureus were 14, 0, 35 and 29mm, respectively. Concerning the Zone of inhibition in gram negative bacteria with gram positive ones was p<0.05 and had significant difference. The minimum inhibitory concentration of Polyamidoamine-G4 dendrimer for Escherichia coli, Bacillus subtilis and Staphylococcus aureus were 1250, 2.5, and 1 &mug/ml, respectively. The minimum bactericidal concentration of Polyamidoamine-G4 dendrimer belonged to Escherichia coli, Bacillus subtilis and Staphylococcus aureus were 2500, 5 and 5 &mug/ml, respectively. Polyamidoamine-G4 dendrimer had not bacteriostatic and bactericidal effects on Enterobacter cloacae.

Conclusion: According to the results, Polyamidoamine-G4 dendrimer can eliminate Escherichia coli, Staphylococcus aureus and Bacillus subtilis effectively. It is suggested in the rest of this study that the probable toxicity of nanostructured compounds examined in drinking water and, economic studies is done for synthesis and their applications in case of prevention of using.