ABSTRACT

       Typing of bacteria is an important part of epidemiological studies on nosocomial infections. Bacterial identification methods have dramatically improved in recent years, which is mainly due to advancements in the field of molecular biotechnology. In many cases, molecular techniques have replaced phenotypic typing methods.

Currently, a wide range of bacterial typing techniques is used that are different from one another in the aspects of study objectives, costs, reliability and discriminatory power. None of the typing methods can achieve all desired objectives of a study alone.

Different typing methods are used for various purposes including: 1. confirmation of epidemiological relationships in spread of an infection, 2. providing epidemiological hypotheses about epidemiological relationships between bacteria in the absence of epidemiological data, 3. describing the distribution of bacterial types and identification of affecting factors. Inferences of epidemiological studies depend on the chosen typing technique and objectives of the study.

Therefore, the typing technique can be useful and effective in increasing our understanding of the pathogenesis, transmission and prevention of possible diseases. The aim of this study was to evaluate various methods of molecular typing of bacteria and to compare these methods from different aspects.

      

ABSTRACT

       Background and Objective: Staphylococcus aureus is the most common and important infectious agent. This bacterium can enter the bloodstream and cause some complications in the intensive care unit (ICU).This organism can frequently be found in the nose and transmitted by the carriers. This study aimed to determine the efficiency of eradicating S. aureus from the nose of ICU personnel in reducing the risk of S. aureus infections in the Panje Azar Hospital in Gorgan, Iran.

        Methods: Sampling was done using sterile swabs collected from the anterior nasal passages.All samples containing Gram-positive cocci were sent to the laboratory of Faculty of Medicine for identification and evaluation of methicillin resistance. All S. aureus nasal carriers were treated with mupirocin ointment b.d for 5 days. The Samples were cultured again after five weeks to evaluate the eradication of S. auerus from the nose of subjects.

       Results: Overall, seven ICU personnel (11.7%) were S. aureus carriers. Two isolates (3.3%) were found as methicillin resistant using both methods of disc diffusion and PCR. The frequency distribution of positive cases indicated a significant difference in terms of work experience (P = 0.012).

        Conclusion: The findings show that treatment of carriers with 2% mupirocin topical ointment eradicates S. aureus from the nose. No S. aureus isolates was found in reculture of nasal samples. Treatment of healthy carriers can significantly reduce the risk of infections caused by the bacterium in the ICU.

  

ABSTRACT

        Background and Objective: Antibiotic-resistant Staphylococcus aureus strains have become a problem in treatment of infections caused by S. aureus. This study aimed to evaluate antibiotic resistance in S. aureus isolates from raw milk and detect femA gene in these isolates, as a confirmatory test for identification of S. aureus species.

        Methods: This cross-sectional study was performed on 110 raw milk samples. After culture in Cooked Meat broth, presence of S. aureus in grown colonies was confirmed in accordance with Iranian National Standard, No. 1194. Antibiotic resistance was then evaluated according to guidelines recommenced by the Clinical Laboratory Standards Institute. FemA-specific polymerase chain reaction was performed on antibiotic-resistant strains using specific primers and standard strains to differentiate S. aureus from other species.

         Results: S. aureus were found in 43 (39.09%) of the 110 collected samples. Among these isolates, 79.07% and 76.75% were phenotypically resistant to penicillin and ceftazidime, respectively. In addition, the femA gene was detected in all isolates.

          Conclusion: The results of this study show a high prevalence of resistance to penicillin and ceftazidime among S. aureus strains isolated from raw milk.

        Keywords: Staphylococcus aureus, Antibiotic Resistance, PCR.

Background and Objective: Nowadays, incidence of antibiotic-resistance among pathogenic bacteria has increased due to indiscriminate use of antimicrobial drugs for treatment of diseases, especially urinary tract infections. Medicinal plants are also of great importance as antibacterial agents. Therefore, the aim of this study was to determine the antibacterial effect of ethanolic extract of nettle (Urtica dioica L.) leaves using two methods of disk diffusion and well diffusion.

         Methods: Ethanolic extract of nettle leaves was prepared by the percolation method. Effect of different concentrations of the extract on Escherichia coli (PTCC1399), Staphylococcus aureus (PTCC 1431), Staphylococcus epidermidis (PTCC 1435) and Staphylococcus saprophyticus (PTCC1440) was evaluated using the disk diffusion and well diffusion methods by measuring diameter of growth inhibition zone. Gentamicin and propylene glycol were used as positive and negative control, respectively.

        Results: In both methods, especially in the well diffusion, the ethanolic extract of nettle leaves had favorable inhibitory effect on the growth of S. aureus, S. epidermidis and S. saprophyticus. In the well diffusion method, the highest rate of susceptibility to the extract (89%) was related to S. saprophyticus and S. epidermidis.

         Conclusion: The ethanolic extract of nettle leaf has good inhibitory effect on the growth of S. aureus (especially in the well diffusion method), which confirms the traditional use of this plant for the treatment of urinary tract infections.

          Keywords: Antibacterial Effect, Staphylococcus, E. Coli, Ethanolic Extract, Nettle (Urtica dioica L.).

ABSTRACT

         Background and Objective: Biofilms are community of bacteria that attach to inanimate surfaces or living tissues via production of extracellular polymers and exopolysaccharide matrix. Microbial biofilms on various surfaces of the hospital environment are considered as a reservoir of infection spread. The present study aimed to evaluate the disinfecting effect of benzalkonium chloride on some bacterial isolates causing nosocomial infections.

       Methods: First, 13 isolates from four bacteria including Pseudomonas aeruginosa, Staphylococcus aureus, Acinetobacter and Enterobacter were obtained from Microbiology Laboratory of Al-Zahra Hospital in Isfahan, Iran. The samples were transferred to Microbiology Laboratory of Faculty of Veterinary Medicine of Shahrekord University for testing. Evaluation of biofilm formation and determination of minimum inhibitory concentration (MIC) of the disinfectant and effect of the disinfectant on planktonic growth and biofilm formation were performed.

        Results: All bacterial isolates (52 cases) produced biofilm. Mean MIC of benzalkonium chloride for P. aeruginosa, S. aureus, Enterobacter and Acinetobacter was 0.14, 0.2, 0.18, 0.17 g/ml, respectively. Planktonic growth of all four bacteria was inhibited at concentrations of 2MIC, MIC and 1/2MIC. Biofilm was not produced in MIC and 2MIC concentrations, and biofilm formation capability increased by reducing the concentration of benzalkonium chloride.

          Conclusion: The results show that the use of appropriate concentration of benzalkonium chloride can prevent the growth of different bacterial species, but sub-MIC dose of this disinfectant may stimulate biofilm formation.

            Keywords: Biofilm, Benzalkonium Chloride, Pseudomonas Aeruginosa, Staphylococcus Aureus, Enterobacter, Acinetobacter.

ABSTRACT
        Background and objectives: Synthesis and characterization of several metal complexes (metal ions: Co2+, Ti4+ and Ce3+) of macroacyclic Schiff base ligand have been reported. The Schiff base ligand is prepared from the condensation reaction of 1, 4-di-(4-fluoro-2-aminophenoxy) butane with salicylaldehyde in ethanol. In addition, antibacterial activity of metal ions, Schiff base ligand and their complexes have been investigated. Recent studies show that many Schiff base complexes have antibacterial activity against Gram-positive and Gram-negative bacteria. Therefore, we aimed to synthesize new Schiff base complexes and evaluate their antibacterial activity against a number of Gram-positive and Gram-negative bacteria.
         Methods: Schiff base ligand and their complexes were characterized by mass spectrometry and IR, H-NMR and C-NMR spectroscopy. The in vitro antibacterial activity of the Schiff base ligand, metal ions and their complexes were evaluated against some Gram-positive and Gram-negative bacteria by disk diffusion method and determining minimum inhibitory concentration.
          Results: In this study, the Schiff base complexes had good antibacterial activity, but the Schiff base ligand and metal ions did not show any antibacterial effect. In some cases, the antibacterial effect of the complexes was higher than that of the standard antibiotics tetracycline and gentamycin. The titanium complex showed the highest antibacterial activity in both methods. This complex created the largest growth inhibition zone (diameter: 100mm) against Staphylococcus aureus, and had the lowest minimum inhibitory concentration against Bacillus subtilis (6.75 mg/ml).
          Conclusion: The compounds synthesized in our study have strong antibacterial activity.
          Keywords: Schiff base complex, Schiff base ligand, antibacterial activity, Staphylococcus aureus, Bacillus subtilis.

ABSTRACT
       Background and Objectives: Mastitis caused by Staphylococcus aureus is a widely distributed disease in cattle, goats and sheep. The infection is often subclinical in cattle, leading to reduced milk production and quality, but acute catarrhal or even gangrenous inflammation may also occur. The aim of this study was to investigate resistance of S. aureus isolates from bovine subclinical mastitis to a number of antibiotics.
          Methods: Milk samples were collected from 120 cows in different regions of Tabriz, Iran. Milk samples were cultured and bacteriological identification was performed. Antimicrobial susceptibility of the isolates was assessed by determining minimum inhibitory concentration. Plasmid DNA was extracted by an alkaline lysis method. 
         Results: The highest frequency of resistance was observed against gentamicin (100%) and β- lactam antibiotics including amoxicillin (96%), ampicillin (40%) and penicillin (96%). The isolates mostly contained large plasmids, which might harbor acquired antibiotic resistance.
         Conclusion: The results confirm the high frequency of antibiotic resistance among staphylococci isolated from bovine subclinical mastitis.
           Keywords: Anti-infective Agents, Cattle, Staphylococcus Aureus, Mastitis, Plasmids.

ABSTRACT
        Background and Objectives: Several virulence factors are involved in the pathogenesis of Staphylococcus aureus. Surface proteins such as collagen binding proteins (Cna) and fibronectin-binding proteins (FnBP) are important factors in adhesion and invasion of S. aureus. The aim of this study was to evaluate the frequency of adherence genes cna, fnbA and fnbB S. aureus isolates from traditional cheese.
        Methods: All 22 isolates tested were identified as S. aureus. The isolates were tested for the presence of adherence genes cna, fnbA and fnbB using specific primers in polymerase chain reaction assay. 
        Results: Six isolates (27.27%) were positive for the can gene. Of the 22 isolates studied, one isolate was positive for fnbA and one was positive for the fnbB. Co-presence of the genes examined was not observed in any of the isolates.
        Conclusion: The results indicate the weak biofilm formation ability of the S. aureus isolates from traditional cheese.
        Keywords: Staphylococcus aureus, Biofilm, Genes, Cheese. 

ABSTRACT
          Background and Objectives: Determining the genetic relationship between S. aureus isolates is important for epidemiological surveillance and control of infections caused by this bacterium. The present study was conducted to determine polymorphisms of coagulase gene (coa) among S. aureus isolates from pastry and cheese samples using restriction fragment length polymorphism (RFLP) analysis.
         Methods: Overall, 65 S. aureus isolated from pastry (n=45) and cheese (n=20) samples were examined for the coa gene by polymerase chain reaction (PCR). PCR products were digested with AluI enzyme and the products were assessed using gel electrophoresis.
          Results: Except for two isolates, all isolates were positive in coa-PCR and produced four different PCR products, with molecular sizes ranging from 570 to 970 bp. Overall; five distinct RFLP patterns were detected (I-V). Although pattern types I and III were present in isolates from both samples, types I and IV were mainly present in isolates from cheese and pastry samples, respectively.
        Conclusion: PCR-RFLP analysis of the coa gene indicates that S. aureus isolates from pastry and cheese samples may be originated from different sources. However, as one pattern type was predominant in each group, it can be concluded that majority of the isolates may have the same origin.
          Keywords: Staphylococcus aureus, PCR-RFLP, Coagulase, Pastry, Cheese.

ABSTRACT
         Background and Objectives: Silver nanoparticles (AgNPs) have physical and surface properties that could threaten human and environmental health. AgNPs are classified as ‘very toxic’ to eukaryotic organisms and are less toxic to bacteria. The aim of the present study was to study the effects of different sub-minimum inhibitory concentrations (MICs) of AgNPs on some virulence factors of Staphylococcus aureus as a pathogenic bacterial model.
         Methods: Tube double serial dilution method was used to determine MIC of AgNPs against standard strain and ten field isolates of S. aureus. Tube cultures of isolates in LB broth were supplemented with different concentrations of AgNPs and were incubated at 37 °C with constant shaking under aerobic conditions. Samples from each tube were streaked on blood agar plates and assay for hemolysins, coagulase and DNase production were performed.
         Results: The MIC of AgNPs against all examined isolates was determined as 50 µg/mL. The results showed that 1/2, 1/4 and 1/8 MIC of AgNPs had no negative effect on DNase and coagulase production but inhibited alpha- and beta-hemolysin production in most isolates (64-91%). In addition, production of delta-hemolysin was inhibited by 1/2 MIC of AgNPs.
         Conclusion: The effects of sub-MIC of AgNPs on bacterial growth appear at 4-8 hours post-exposure and then the bacteria follow a normal growth trend. This toxic effect may affect ecosystems species.
         Keywords: Silver particles, Minimum inhibitory concentration, Virulence factors, Staphylococcus aureus.

ABSTRACT
             Background and Objectives: In recent years, infections caused by antibiotic-resistant strains of Staphylococcus aureus have become a major health issue. It has been suggested that the extract or essential oil of cinnamon tree has antibacterial properties. In this study, we investigated the antibacterial effects of polyurethane-cinnamon nanofibers against clinical isolates of S. aureus.
             Methods: Polyurethane-Cinnamomum zeylanicum nanofiber scaffolds were synthesized. Polyurethane nanofiber and cinnamon polymers were also used to prepare the scaffold under the electrospinning process. Infrared spectroscopy, electron microscopy and mechanical tensile test were utilized to assess the scaffolds. Minimum inhibitory concentration of the nanofiber against the bacteria was determined using the broth dilution method according to the Clinical & Laboratory Standards Institute guidelines.
Results: The results of antibiogram test showed that all tested disks were susceptible to S. aureus. Diameter of growth inhibition zone for polyurethane-cinnamon 10% was 41 mm. Minimum inhibitory concentration of the nanofiber against S. aureus isolates was 0.02 μg/mL.
             Conclusion: We demonstrated that the polyurethane-cinnamon nanofiber has favorable antibacterial effects against clinical isolates of S. aureus. It is recommended to conduct further studies on the antibacterial effects of this nanofiber on other bacteria.
             Keywords: Staphylococcus aureus, Cinnamon, Nano fiber.

ABSTRACT
            Background and Objectives: Schiff base ligands are prepared via the condensation reaction of 1, 10- dimethyl–phenantroline aldehyde derivative with some nitrogen donor ligands, such as benzene ring that have different functional groups (-OH, -SH, -OCH₃,-CH₂OH, -Br) in acetonitrile. Recent studies suggest that Schiff bases might have antibacterial activity. Therefore, we aimed to synthesize new Schiff base complexes and evaluate their antibacterial activity against a number of Gram-positive and Gram-negative bacteria.
            Methods: Schiff base ligands and their complexes were characterized by mass spectrometry, infrared spectroscopy and nuclear magnetic resonance spectroscopy. The in vitro antibacterial activity of the Schiff base ligands and metal ions against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa was evaluated by determining minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) using the broth dilution method.
            Results: All synthesized Schiff bases exhibited favorable antibacterial activity against the tested microorganism, but the antibacterial effect of compounds 3OH and 3SH was more significant than that of other compounds.
            Conclusion: Compound 3EOH has favorable antibacterial activity against the tested bacteria.
            Keywords: Schiff bases, antibacterial effect, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa.

          Background and Objectives: Staphylococcus aureus is a common cause of nosocomial infections. The ability of S. aureus to form biofilm and acquire antimicrobial resistance has made this organism a major health problem. In this study, we investigate the biofilm-forming ability of S. aureus isolates from clinical samples.
          Methods: Sixty S. aureus isolates from clinical specimens were collected from the 5th Azar Hospital of Gorgan (Iran) in 2018. The isolates were identified using conventional methods including Gram staining and biochemical tests (catalase and coagulase). Biofilm formation by S. aureus isolates was evaluated using a microplate-based method.
          Results: Of 60 S. aureus isolates, 47 (78.3%) strains were identified as biofilm-forming and 13 (21.7%) strains were non-biofilm-forming.
          Conclusion: The high prevalence of biofilm-producing S. aureus isolates in the 5^th Azar hospital of Gorgan could pose a major health challenge with serious consequences for hospitalized patients. Therefore, it is crucial to disinfect and sterilize hospital surfaces and equipment effectively to minimize the risk of contamination and spread of bacteria in the hospital settings.
          Keywords: Biofilms, Staphylococcus aureus, sample.