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Imipenem is a member of Carbapenem with stability against most β-lactamases. It is of particular use in the treatment of infections associated with drug resistant gram negative bacteria harboring ESBL and AmpC genes. The aim of this study was to determine the imipenem resistance in gram negative bacteria causing nosocomial infections and the presence of metallo-β-lactamases (MBLS) in resistant isolates.

Minimum inhibitory concentration (MIC) of imipenem was determined for 276 multiple drug resistant gram negative bacteria by agar dilution method. Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 700603 and Pseudomonas aeruginosa ATCC 27853 were used as standard strains. Disk diffusion method with disks containing imipenem and imipenem+10µl EDTA (0.5 M) was used for determination of the presence of metallo-β-lactamases. Zone diameter ≥7mm of imipenem tested in combination with EDTA versus imipenem alone was considered as MBL positive.

From a total of 276 β-lactamase producing isolates including K. pneumoniae (n=38), E. coli (n=169) and P.aeruginosa (n=69), 3 isolates with MIC=32µg/ml were found to be resistant to Imipenem. From these isolates, one strain of K. pneumoniae and one strain of P.aeruginosa isolates were determined to be MBL producers by phenotypic method.

According to the presence of metallo β- lactamases in bacterial strain in the region, resistance to this valuable therapeutic agent is not unexpected.

In this study, Antibacterial and antioxidant activities of the essential oil and methanolic extract of the endemic plant, Zataria multiflora Boiss. have been studied. The antioxidant potential of the samples was evaluated using two separate methods of inhibition of free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ammonium thiocyanate systems. Antibacterial activity was determined by using disc diffusion method. The antibacterial test results showed that the essential oil of the plant strongly inhibited the growth of all of the microorganisms studied especially the Gram-negative strains. The polar fraction of methanolic extract showed inhibitory effect on Gram-positive strains, while the non-polar fraction showed similar activity similar to the essential oil but not as strong as that. Essential oil and sub fractions of the methanolic extract were able to reduce the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) with an IC50 of 22.4 ± 1.0 for essential oil and 21.7 ± 1.6 and 16.2 ± 1.6? g/ml respectively for non-polar and polar fractions, which the activity of the latter is almost equal to synthetic antioxidant BHA (18.2±1.9? g/ml). Inhibition values of linoleic oxidation were calculated to be 82.4% and 80.3% for the polar and non-polar fractions respectively. The essential oil showed more inhibitory activity (89.7 ± 2.5) that is similar to the synthetic antioxidants BHA (97.8 ± 2.9) and ascorbic acid (93.2 ± 2.1). The chemical composition of hydrodistilled essential oils of Z. multiflora was analyzed by GC/MS. A total of 25 compounds representing 99.78% of the oil were identified. Thymol (37.59%), carvacrol (33.65%); para cymene (7.72%), gamma terpinene (3.88%) and beta caryophyllene (2.06%) were the main components comprising 84.9% of the oil. The obtained results show that the essential oil and methanolic extract of Z. multiflora possess antioxidant and antibacterial activities, therefore Z. multiflora could be used as a natural preservative ingredient in food and drug industries.

Povidone Iodine and Cetrimide-c are important and valuable antiseptic compounds that have been used for many years, as disinfectant for wounds, burns, instruments and the environments such as surgical rooms in the hospitals. Recently, bacterial resistances to these antiseptics have been reported in multi-drugs resistance bacteria such as Enterococci, which are important causes of nosocomial infections. This study was done to confirm the antiseptic activity of these agents. In this study 5 isolates of Escherichia coli and 13 isolates of Enterococci being resistant or sensitive to at least 5 antibacterial agents, including vancomycin, isolated from urinary tract infections were used. The concentrations of 1:2, 1:5, 1:10, 1:20 and 1:100, of povidon Iodoine, and 1:200 and 1: 500 for cetrimide-c were used. Concentrations of 5 ×107 and 1×107 CFU/ml (Colony Forming Unit) of the bacteria were tested at room temperature in the presence of Povidone-Iodine and Cetrimide-c for 2, 10, 30 minutes. After treatment of the bacteria with antibacterial agents the bacteria were washed three times with phosphate buffer in order to remove the small amounts of antibacterial agents that were present in the inoculums used for bacterial growth. The results shows that in all cases the bacteria which were in contact with the antiseptic agents were unable to grow on solid media, whereas the control bacteria which were not in contact with the antibacterial agents had complete growth on the solid medium. Since resistance to the above mentioned antiseptics were not detected at different concentrations of antibacterial agents and the bacterial suspensions, these agents can still be used in the hospitals and other clinical centers for the disinfection of the skin and contaminated instruments. However continuous monitoring of the antiseptic activity of these compounds is recommended.

Obective:Resistance to heavy metal ions has been reported in many bacteria. Since any change in the bacterial activity can have important consequnesc both from scientific and clinical aspects, this study was performed for the determination of potassium tellurite resistance in the clinical isolates of Escherichia coli. Subjects and The minimum inhibitory concentration (MIC) of potassium tellurite was determined for 449 isolates of Escherichia coli, isolated from infected urinary tract or normal fecal flora, using standard agar dilution method. Approximatley half (48.7%) of the isolates had MIC of ≤1µg/ml after 24 hours of incubation at 35 ºC. Many of the bacteria that were cultured with low concentrations of potassium tellurite, ≤ 5 µg/ml, overcame the toxicity of this heavy metal when they were re-incubated for the additional 24 hours. The MIC for these isolates was increased, so that the difference between the MIC after 24 and 48 hours of incubation became significant (P ≤ 0.001). In medium containing ≥10 μg/ml of potassium tellurite, the bacteria formed typical black colonies. No statistically significant difference was found between the MIC of bacteria that where isolated from urinary tract infection or normal fecal flora.Since resistance to heavy metals can be simultaneous with resistance to antibacterial agents, determination of simultaneous resistance to antibacterial agents and other heavy metals in this bacterium and other bacterial genus is necessary in this region.