Background and Aims: Staphylococcus aureus as a�Gram- positive coccus causes a variety of infections in humans. It is one of the infectious agents in hemodialysis patients. Those patients who carry this organism at their nose are exposed to infection and possible morbidity and mortality due to this bacterium. Resistance to antibiotics in staphylococci is increasing. Resistance development is due to mutation and by plasmid DNA transmission. The aim of this study was to determine plasmid profile and antibiotic resistance of Staphylococcus aureus strains isolated from nasal carriers in dialysis patients in Imam Khomeini Medical Center. Susceptibility testing to antibiotics, plasmid extraction and analysis and epidemiologic relationship of these isolates were investigated.�

  Methods: In this study nasal specimens of 107 patients in dialysis ward of Imam Khomeini Medical Center were collected and cultured on blood agar plates. The colonies were identified as S.aureus strains. The susceptibility of 50 strains isolated from the patients against 12 antibiotics were tested using Kirby- Bauer standard method. A standard S.aureus strain (ATCC29213) was used to control quality of antibiotic discs. The isolates were cultured on LB medium and plasmid DNAs were extracted and electrophoresed on agarose gel using Parisi et al method.

  Results : The results of resistance rate against 12 used antibiotics were as follows: resistance of the strains against gentamicin, oxacillin, neomycin, clindamycin, erythromycin, cotrimoxazole, choloramphenicole, tetracycline, and ciprofloxacin were 20%, 28%, 30%, 26%, 30%, 44%, 32%, 36%, and 10%, respectively. All of the strains were resistant to amoxycillin and penicillin and none of them were resistant to vancomycin. Of 50 S. aureus strains, only 27 strains contained plasmid DNA. Most of the strains revealed a big plasmid. Plasmid profiles of the strains will be presented.

  Discussion: Our results showed that there was a close relationship between high resistance to antibiotics and presence of plasmids in S. aureus strains. Similarities among resistance to antibiotics and plasmid profiles in our strains isolated from the same ward showed that these strains were from the same sources and indicated a unique clonal possibility. The resistance to antibiotics of the strains lacking plasmids could be from choromosomal resistance

  Background and Objectives: Pseudomonas aeruginosa is a nosocomial pathogen that presents high antibiotic resistance.There are phenotyping and genotyping methods for epidemiologic study of Pseudomonas aeruginosa such as antibiotic resistance pattern and plasmid profile analysis. Plasmid analysis provides useful information concerning the source of the strains and number of clones present in the epidemies. Thus, this study was conducted to evaluate antibiotic and plasmid profiles of P. aeruginosa strains isolated from in-patients of the Sina Medical Centre of Tabriz to clarify epidemyological correlation among isolated strains.

  Methods: During 13 months, 135 strains of P. aeruginosa were isolated from different infections in hospitalized patients at Sina Medical Center of Tabriz. Antibiotic susceptibility tests were performed using disc agar diffusion test. For plasmid DNA extraction and detection of open circular bands from supercoiled ones, modified alkaline lysis procedure and two dimensional electrophoresis were used, respectively. Enzymatic digestion of plasmids was carried out by EcoRI and HincII restriction enzymes.

  Results: Resistance rates of strains against antibacterial agents were recorded as: Aztreonam (77%), colistin (74%), ceftazidime (69%), pipracillin (67%), ofloxacin (62%), tobramycin (56%), carbenicillin (54%), gentamicin (51%), ciprofloxacin (22%), amikacin (15%), polymixin B (13%) and imipenem (2%). Plasmid profiles of our test strains revealed that only 67 strains harbored plasmid(s). Number of isolated plasmids ranged 1-6 in each strain with molecular mass of 0.5kb-21kb. When the isolated plasmids were digested using restriction endonuclease enzymes (EcoRI and HincII), in 32% of them similar digestion profiles were obtained by EcoRI indicating a unique source for them.

  Conclusion : Our findings suggest high antibiotic resistance and plasmid presence in P. aeruginosa strains isolated from different infections, and there were remarkable similarities among isolated plasmids. Since our test strains had been isolated from various wards in a short period of time, the results raise the possibility of unique source for some strains or high prevalence of genetic exchange among P. aeruginosa strains.

  Background & Objectives: Pseudomonas aeruginosa is a Gram-negative and aerobic bacterium. Exotoxin A is one of the important toxins produced by the bacterium and it is the main cause of mortality. About 90% of P. aeruginosa strains produce this toxin. Biofilm is a functional consortium of microorganisms attached to the body surfaces and bacteria are embedded in extracellular polymeric substances produced by the microorganisms. This bacterium is nontoxic in the planktonic form, but as a biofilm is highly toxic. In this study, we examined the association between the presence of exo-A gene and antibiotic resistance patterns with biofilm formation in Pseudomonas aeruginosa strains.

  Methods: In this study 110 strains of Pseudomonas aeruginosa isolated from various infections with defined antibiotic resistance patterns were used. The PCR method was used to detect the presence or absence of Exotoxin A gene (exo-A). Ability of biofilm formation was evaluated by spectrophotometry. Association between exo-A gene and antibiotic resistance patterns with biofilms formation was analyzed statistically by Fishers and Chi-square tests.

  Results: exo-A gene was detected in 93 strains (84.5%). Sixty two strains were multidrug resistant and they produced broad spectrum beta-lactamase enzyme. Results showed that, exo-A positive strains had significantly higher ability to biofilm formation in comparison with exo-A negative strains (p<0.05). Also the biofilm formation was significantly higher in multidrug resistant and ESBL producing strains (p<0.05).

  Conclusion: The results of this study indicate that there is a significant association between exo-A gene as well as antibiotic resistance pattern and ESBl producing with biofilm formation in Pseudomonas aeruginosa. Because of importance of biofilms in the pathogenesis of this bacterium, our study could open a new window for investigation of the molecular processes involved in the formation of biofilms.

  Background & Objectives: Nowadays, appearance of ESBL producing bacteria is medical problem in the treatment of infections. Uropathogenic Escherichia coli like many other bacteria can produce these types of enzymes. T he assessment of the ESBL production by clinical isolates is not done routinely in laboratories. The aim of this study was to determine the prevalence of ESBL producing E.coli and its antibiotic resistance pattern in Kermanshah.

  Methods: This cross - sectional study was done on 200 Uropathogenic E. coli strains isolated from people in Kermanshah. Sensitivity of isolates to different antibiotics was determined by disk diffusion test and ESBL production was assessed by DDST method.

  Results: The E. coli strains showed high susceptibility to imipenem (100%), amikacin (97%), nitrofurantoin (95.5%), gentamicin (85%), cefepime (75%), ceftazidime (74%), ofloxacin (73.5%), ciprofloxacin, ceftriaxone and aztreonam (71%) and cefotaxime (70%) respectively. The highest resistance was seen to ampicillin (77%), carbenicillin (76%), pipracillin (74%) and SXT (62.5% ). Resistance rate to third generation cephalosporins was 63-75%. Fifty seven isolates (27%) were ESBL producers and 47 isolates (87%) produced all four types of ESBL enzymes.

  Conclusion: There are some similarities and differences in the antibiotic resistance pattern and ESBL production among the isolates in different areas of Iran and other countries. Identification of ESBL producing bacteria and determining its antimicrobial resistance pattern are recommended to effective treatment of infections.