A comparison of antibiotic disks from different sources on Quicolor and Mueller-Hinton agar media in evaluation of antibacterial susceptibility testing

Background and Objectives: Antibacterial susceptibility testing of clinical bacterial isolates through disk diffusion method plays a major role in antibacterial treatment. One of the main factors affecting the result of these tests is the type, structure and quality of the disks. The main objective of this study was to compare the agreement of antibiotic disks originated from three companies on Quicolor and Mueller-Hinton agar. Materials and Methods: Quicolor and Mueller-Hinton agar media were used in disk diffusion method. Seventy clinical isolates from Enterobacteriaceae family (21 Klebsiella spp., 36 Escherichia coli, 1 Enterobacter spp. and 12 Shigella spp.) were investigated in the study. After obtaining data, the results were interpreted as resistant, sensitive or intermediate. Kappa coefficient measured the agreement of two media. Coefficient of variation (CV) was also calculated for antibiotic disks. Results: The kappa agreement values for three types of antibiotic disks on Quicolor and Mueller-Hinton agar plates were good or excellent for all the examined antibiotics. CV values were also very satisfactory in the majority of cases. Conclusion: Antibiotic disks from three manufacturers can successfully be used on both Quicolor and Mueller-Hinton agar plates

Study of antimicrobial effects of several antibiotics and iron oxide nanoparticles on biofilm producing pseudomonas aeruginosa

Objective(s): Pseudomonas aeruginosa is a nosocomial pathogen resistant to most antimicrobial treatments. Furthermore, it persists in adverse environments thereby forming biofilms on various surfaces. Researchers have therefore focused on antibiofilm strategies using nanoparticles due to their unique physicochemical properties. Superparamagnetic iron oxide nanoparticles (SIONPs) have recently shown to possess antimicrobial and anti-biofilm characteristics. In this study, the effects of SIONPs and some antibiotics were tested against strong biofilmproducing P. aeruginosa isolates.Materials and Methods: 60 isolates of P.aeruginosa were screened for biofilm formation on microtiter plates using 0.1%w/v crystal violet (CV) staining. Twenty isolates producing strong biofilms were selected for further study on the effects of antimicrobial agents. Microdilution method was used to assay twenty isolates susceptible to antibiotics. The effects of antibiotics and SIONPs on biofilm formation were determined by the microdilution method and 0.1% CV staining. The checkerboard dilution technique was used to determine the combined effects of SIONPs and imipenem.      Results: In twenty isolates, the rate of resistance to ciprofloxacin, levofloxacin, amikacin, azithromycin was 65, 75, 45 and 95% respectively. SIONPs at 30 µg/ml reduced biofilm biomass in 11 isolates; however it stimulated biofilm formation in 9 isolates. The effects of SIONPs in combination with imipenem in the 10 isolates were different exhibiting synergistic or antagonistic relationships.Conclusion: P. aeruginosa has increasingly developed resistance to many antimicrobial agents but the resistance to nanoparticles is less frequently been reported. However, iron oxide nanoparticles could enhance biofilm production in isolate- dependent manner because they may possibly utilize this nanoparticle as an iron source, an important element in biofilm production. The exact mechanism of these effects however, remains to be elucidated

Comparison of two methods for quantification of Acinetobacter baumannii biofilm formation

Introduction: ‏ Medical devices are made from a variety of materials such as polypropylene, polycarbonate, poly styrene, glass and etc. by attaching to this surfaces, Acinetobacter baumannii can form biofilms and then cause several device associated infections. Biofilms are communities of bacteria attached to the surfaces. In this study, biofilm formation ability in clinical isolates of Acinetobacter baumannii was assessed by two methods on different surfaces. Materials and methods: ‏ Biofilm formation by 75 clinical isolates of A. baumannii was evaluated on polycarbonate surface (microtiter plate) and polypropylene surface (falcon) by crystal violet and 2,3-Bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide salt (XTT tetrazolium sodium salt) assay methods. Falcon or tube method was carried out under static and agitation conditions. Results: ‏ Results showed the most isolates can form biofilm but higher numbers of isolates form biofilm on polypropylene surface under agitation. XTT method confirmed strong biofilm formation ability of 10 isolates. Discussion and conclusion: Each of the two assays showed an excellent applicability for the quantification of biofilms. The Crystal violet assay is cheap, easy and is usually used for the quantification of biofilms formed by microorganisms but XTT is more reliable and repeatable. Most of A. baumannii isolates have potential to form biofilm on the medical devices which may result in device-associated infections

The effect of Cyclamen coum extract on pyocyanin production by Pseudomonas aeruginosa

Researches have shown that some plants possess antimicrobial activity and the ability to overcome drug-resistant pathogens. Their frequent used in treatment of microbial infections has been led to isolation of the active compounds and evaluation of their antimicrobial properties. Cyclamen coum Miller is one of these plants with a secondary metabolite called saponin which has antimicrobial activity. Pyocyanin is one of the virulence factors in Pseudomonas aeruginosa, an opportunistic pathogen, causing lung diseases. The present study indicates the effect of cyclamen saponin extracts on pyocyanin production by P. aeruginosa. We prepared three different types of plant extracts (ethanolic, aqueous and butanolic) from tuber of C. coum. The effect of 0, 10 and 20 mg of cyclamen saponin were tested by agar disk diffusion technique. Pyocyanin purification was done from microbial broth culture and the extracted pyocyanin was measured by spectrophotometric method. Results showed that the production of pyocyanin was remarkably reduced by ethanolic extract of saponin. In addition increased saponin concentration led to further decrease in pyocyanin content

The Study of Synergistic Effects of n.butanolic Cyclamen coum Extract and Ciprofloxacin on inhibition of Pseudomonas aeruginosa biofilm formation

  Introduction : Infections caused by Pseudomonas aeruginosa biofilm are the major causes of death in patients with cystic fibrosis (CF). Some studies revealed that biofilms are resistant to several antibiotics because of their impermeable structures. In order to re-sensitize bacteria to different antibiotics, biofilm formation should be inhibited. In this research, evaluation of antibiofilm activity of n-butanolic Cyclamen coum extract as a medici­nal plant from Myrsinaceae family, in combination with ciprofloxacin was carried out.   Materials and method s: The biofilm formation ability by P. aeruginosa PAO1 and one clinically isolated P. aeruginosa (PA214) was confirmed by microtiter plate method. Extraction of the tubers of Cyclamen coum was done by fractionation method . The antibiofilm and antibacterial properties of n-butanolic C. coum extract (which includes saponin compounds) alone and in combination with ciprofloxacin by using microdilution and crystal violet methods were examined. The cytotoxicity effect of the n-butanolic extract on HT-29 cells was assayed by MTT (3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyl-tetrazolium bromide) test.   Results : The biofilm formation ability by P. aeruginosa strains was quantitatively confirmed. Saponin content of the n-butanolic C.coum extract was 156 µg/mL. The extract revealed antibacterial activity against the growth of planktonic P. aeruginosa strains. The combination of n-butanolic C.coum extract and ciprofloxacin significantly inhibited P.aeruginosa biofilm formation (ΣFBIC = 0.5). The n-butanolic C.coum extract showed insignificant cytotoxic effect against HT-29 human cancer cell line after 48 hours and 72 hours incubation .   Discussion and conclusion : It can be concluded that n-butanolic C.coum extract in combination with ciprofloxacin significantly revealed antibiofilm activity against P. aeruginosa biofilm however, further clinical investigations are required