Vol 2 No 3-4 (2013)

Original Articles

  • XML | PDF | downloads: 1095 | views: 5099 | pages: 1-10
    Background: Incidence of  white  spots due  to  demineralization of  enamel  and  gingival problems  is  an  unacceptable  result  of  orthodontic  treatment.  Plaque  accumulation  and bacterial biofilm growth are responsible for these phenomena. The resin-based dental composites used as bonding agents in orthodontics play a major role in mentioned problems. As recent researches assert the antimicrobial effects of chitosan (CS) and zinc oxide (ZnO) nanoparticles  (NPs),  it  seems  that  adding  these  nanoparticles  to  the  composite  can  be beneficial in reducing the number and function of microorganisms. The aim of this study was to  evaluate  the  antimicrobial  effects  of  ZnO-NP  and  CS-NP-containing  orthodontic composite.Methods: Antibacterial effectiveness of ZnO-NPs and CS-NPs was assessed in four groups against Streptococcus mutans, Streptococcus sanguis and Lactobacillus acidophilus grown both planktonic and as a biofilm on composites. One group as the unmodified control group and  three  groups  consisting  of  three  different  concentrations of  ZnO-NPs  and  CS-NPs mixture: 1%, 5% and 10% (1:1 w/w). 108 CFU/ml microorganism suspensions were provided with spectrophotometer. Biofilm formation was quantified by viable counts. Disc agar diffusion (DAD) test was carried out to determine antimicrobial effects of nanoparticles by measuring the inhibition diameter on brain heart infusion agar plates. Finally,viable counts of microorganisms on days 3, 15 and 30 were collected for the antimicrobial effects of eluted components from composite discs.Results: In biofilm formation test, a reduction in bacterial counts was observed with 10% nanoparticle-containing composites compared with their unmodified counterpart. In the DAD test only 10% nanoparticle-containing specimens showed statistically significant inhibition. The only noticeable datain eluted component test was on day 30 for 10% nanoparticle- containing discs, inhibiting L. acidophilus.Conclusion: It seems that a mixture of ZnO-NPs and CS-NPs has induced an antibacterial activity in resin composite; especially in 10% weight concentrations which was significantly higher than other groups.
  • XML | PDF | downloads: 516 | views: 453 | pages: 11-16
    Background: The emergence and rapid spread of metallo-beta-lactamase (MBL) producing Acinetobacter spp. are of great concern worldwide due to limited treatment options. Epidemiologic studies of the causing genes are important for prevention.Methods:  In  this  study,  70  imipenem-resistant  Acinetobacter  strains  were isolated from health care associated infections. These isolates were screened for detection of metallo-beta-lactamase (MBL) using inhibitor potentiated disk diffusion tests with thylenediaminetetraacetic acid (EDTA). PCR was designed for detection of bla vim and bla imp-1 using specific primers.Results: Among these 70 strains, 50 strains appeared to produce metallo-beta-lactamase. Three isolates were detected by PCR to carry metallo-beta-lactamase gene bla vim, but bla imp-1 gene was not detected.Conclusion: These findings suggest that in our area other genetic elements are responsible for resistance against metallo-beta-lactams.
  • XML | PDF | downloads: 497 | views: 523 | pages: 17-25
    Background: Health care-associated infections are an important cause of morbidity and mortality in hospitals. Reports have shown that nurses’ uniforms are sources of health care-associated infection transmission. The present study assessed the rate of bacterial contamination of healthcare worker’s white coats in two tertiary hospitals in Mashhad, Iran.Methods: 300 healthcare workers participated in the study from July to October 2011. Samples were obtained with a sterile swab from the outer surfaces of three sites of the white coat including the cuff, pocket mouth of the dominant hand and abdominal region. The samples were examined according to standard procedures. Results: Overall, 1220 microorganisms belonging to 13 different genera were isolated from a total of 900 samples. All 300 white coats were contaminated by bacteria of which 282 (94%) were pathogenic. The abdominal region had significantly higher number of isolates than the pocket and sleeve (p = 0.02). The white coats of “cardiac surgery ICU” and “surgery ward” had the mean highest number  of  isolates.  Gram-positive  Bacilli  (36.1%)  were  the  most  common isolates followed by Staphylococcus aureus (28%) and coagulase-negative Staphylococci (24.8%).Conclusion: Health care workers’ white coats are contaminated with a variety of bacteria. In order to reduce cross contamination from white coats to patients, re- educational programs and stricter rules of laundering and changing white coats are suggested.
  • XML | PDF | downloads: 570 | views: 741 | pages: 26-31
    Background: One of the main mechanisms of resistance to carbapenems is potential of Klebsiella pneumoniae to produce K. pneumoniae Carbapenemase (KPC). KPC is an important type of carbapenemase, which can hydrolyze carbapenems and other beta-lactam antibiotics. Modified Hodge Test (MHT) and  use  of  boronic  acid  as  a  KPC  inhibitor  are  two  types  of  phenotypic methods, which are used for detection of carbanemase-producing bacteria. Specificity of these two phenotypic tests for identification of KPC was assessed in this study.Methods:   Forty-four   K.   pneumoniae   strains   were   isolated   from  wound infections   of   burn   patients.   All   isolates   were   identified   with   specific biochemical tests. Carbapenem-resistant K. pneumoniae isolates were identified by disc diffusion method and analyzed with cut off-points of CLSI 2011 guideline.   For   detection   of   KPC-producing   strains,   carbapenem-resistant isolates were examined with two different phenotypic (i.e. MHT and Boronic acid) methods. Subsequently, strains with positive phenotypic methods were examined by PCR as a molecular method.Results: Twenty-eight (64%) out of 44 isolates were resistant to carbapenem according  to  CLSI  breakpoints  and  16  (36%)  were  susceptible.  MHT  was positive in all of carbapenem-resistant isolates but none of them have had the synergism effect between meropenem and boronic acid. Also, all isolates were negative for presence of KPC genes on gel electrophoresis. According to results MHT has not enough specificity for detection of KPC.
  • XML | PDF | downloads: 290 | views: 484 | pages: 32-40
    Background: Quorum-sensing systems regulate expression of several virulence factors in Pseudomonas aeruginosa. This study investigated the relation between expression of the las quorum-sensing system and expression of mexY and ampC in35 clinical isolates of P. aeruginosa.Methods: Antibiotic susceptibility was determined by the disc diffusion method according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Expression of genes including lasI, lasR, mexY, ampC and ampR was assessed by real time RT-PCR.Results: Twenty eight isolates with elevated expression of mexY and ampC (compared to  P. aeruginosa PAO1) were resistance to ceftazidime, imipenem, ciprofloxacin and amikacin. Also these isolates demonstrated increased expression of lasI and lasR. The remaining seven isolates showed intermediate resistance to ciprofloxacin and amikacin. These seven isolates with elevated ampR expression demonstrated decreased expression of mexY, ampC, lasI and lasR.Conclusion: In contrast to previous study, current study demonstrated that the expression pattern of ampC was identical to the lasI expression pattern among clinical isolates. Furthermore according to previous study we expected that AmpR positively regulated ampC expression but in our study, some of the isolates with elevated ampR expression showed decreased ampC expression. The expression pattern of lasR and mexY was identical in all of the isolates. It seems there was a direct or indirect relation between expression of lasR and mexY expression in P. aeruginosa.
  • XML | PDF | downloads: 252 | views: 475 | pages: 41-46
    Background: Methicillin-Resistant Staphylococcus aureus (MRSA) is the one of most commonly isolated organisms from clinical samples which can cause life- threatening infections. The emergence and spread of antibiotic resistance makes the treatment of these infections more complicated. In this study, we aimed to determine  the  patterns  of  antibiotic  resistance  among  MRSA  isolates  from Tehran, Iran.Methods: From December 2012 to April 2014, 120 clinical samples were collected. MRSA was identified by cefoxitin disc diffusion. Antimicrobial susceptibility testing was performed on MRSA isolates for eight other antibiotics by disc diffusion method according to CLSI (2013) recommendations. Also, the minimum inhibitory concentration (MIC) was determined for vancomycin by MIC test strips.Results: According to disc diffusion, 60 (50%) isolates showed resistance to cefoxitin. Among these isolates, the rate of resistance to nitrofurantoin, vancomycin, teicoplanin, doxycycline, trimethoprim, erythromycin, clindamycin, and ciprofloxacin were 0%, 0%, 0%, 28.3%, 28.3%, 58.3%, 63.3%, and 70%, respectively. All isolates were susceptible to vancomycin according to disc diffusion and MIC.Conclusion: Compared to other reports from Iran, our study indicated a moderate rate  for  MRSA.  However,  the  rates  of  resistance  to  generally  prescribed antibiotics in these isolates were high. In this situation, it is recommended to monitor the antibiotic resistance in these hospitals.
  • XML | PDF | downloads: 326 | views: 567 | pages: 47-55
    Background: Staphylococcus aureus (S. aureus) has remained always an important pathogen of common infections acquired in community and as  well as serious nosocomial infections. With advent of penicillins and cephalosporins, infections could be effectively treated, but with the global emergence of Methicillin Resistant Staphylococcus aureus strains (MRSA) physicians were  again left  with limited treatment options. This scenario of increasing resistance is even more intense and challenging for developing countries like Pakistan. Hence with this background the study was carried out to establish the frequency of MRSA in clinical specimens and look into the available antibiotic treatment options.Methods: Samples of  pus, blood, urine, body fluids and catheter tips submitted for culture  in  Microbiology department between  August  to  September  2012,  from outdoor and indoor adult patients of Pakistan Institute of Medical Sciences Islamabad, yielding growth of S. aureus were included in the study. After identification by  standard  methods, antibiotic susceptibility of  the  isolates  was performed by Kirby Baeur disc diffusion method. The study was retrospective descriptive and observational.Results: Total  106  S.  aureus  were  isolated. 45.3%  of  them  were  MRSA  and majorities were from pus samples of hospitalized patients. All MRSA were 100% sensitive to vancomycin, whereas 87.5% to chloramphenicol. To rest of the non – beta lactam drugs, resistance of 80% or more was noted.Conclusion: S. aureus is a common clinical isolate from patients in this region of Pakistan and significant number were MRSA especially from hospitalized patients. Treatment options are limited to vancomycin and chloramphenicol.
  • XML | PDF | downloads: 318 | views: 406 | pages: 56-61
    Background: Acinetobacter spp. emerged as an opportunistic pathogen for hospital-acquired infections. Recently, increasing antibiotic resistance among Acinetobacter spp. has worsened the problem. The aim of this study was to investigate  the  emerging  trend  of  infection  due  to Acinetobacter  in Ghaem University Hospital, Mashhad during 2006-2012.Methods: The demographic data and information about redisposing factors was collected. Appropriate bacteriological samples were collected and Acinetobacter spp. was isolated. Antibiotics susceptibility pattern of these isolates against different antimicrobials agents was determined.Results: Results confirmed that Acinetobacter spp. cause 20.9% of nosocomial infection during this period. The trend of Acinetobacter nosocomial infection was increasing and patients with risk factors such as COPD, bronchectasia, diabetes   mellitus   were   more   prone   to   infection.  There   was   significant association   between   these   infections   and   invasive   procedures   such   as catheterization, mechanical ventilation and broad-spectrum antibiotics usage.Conclusion:  Understanding  trends  in  causative  organisms  of  nosocomial infection can help us to better define our infection control policy.