فهرست مطالب

Medical Bacteriology - Volume:4 Issue: 1, 2015
  • Volume:4 Issue: 1, 2015
  • تاریخ انتشار: 1394/05/20
  • تعداد عناوین: 12
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  • Mojtaba Moosavian, Maryam Torabipour Pages 1-7
    Background
    One of the most important agents in hospital-acquired infections is Staphylococcus aureus. Treatment of methicillin-resistant S. aureus (MRSA) infections with decreased susceptibility to vancomycin has recently been more difficult. The aim of this study was to evaluate the possible presence of vancomycin intermediate S. aureus (VISA) and vancomycin- resistant S. aureus (VRSA) and also to determine the frequency of MRSA in clinical specimens.
    Methods
    In this study, 195 S. aureus isolates were collected from the patients were examined. All of the isolates were identified using standard biochemical tests. Susceptibility of S. aureus isolates against 10 antibiotics was detected by disk diffusion method and was followed by E-test and vancomycin screen agar methods. Minimum inhibitory concentration (MIC) of vancomycin was determined according to the CLSI guidelines. Also, detection of mecA gene was performed by PCR and finally, the results were compared.
    Results
    All of the isolates were susceptible to vancomycin (i.e. MIC range of vancomycin was between 0.25-2 µg/ml). Out of 195 S. aureus isolates, 99 isolates (50.8%) were resistant tomethicillin, and mecA gene was detected in 96 isolates. These results also showed that thehighest and lowest resistance rate of isolates was to penicillin (96.9%) and chloramphenicol(0%), respectively.
    Conclusion
    Our findings showed that vancomycin can still be used as a valuable drug fortreatment of S. aureus infections in our region. However, periodic evaluation of vancomycinMIC of S. aureus isolates is critical for monitoring MRSA and preventing the spread of VISA orVRSA among patients.
    Keywords: Methicillin, Resistant, Staphylocccus aureus, mecA gene, Polymerase Chain, Reaction, Vancomycin, Staphylococcal, infections
  • Fatemeh Andalibi, Mehdi Fatahi Bafghi, Parvin Heidarieh, Masoumeh Rasouli Nasab, Shadi Habibnia, Mohammad Reza Pourmand, Seyyed Saeed Eshraghi Pages 8-14
    Introduction
    Nocardia is saprophytic soil bacterium of the actinomycetes families. Nocardia has high diversity of species and due to species diversity of Nocardia, phenotypic tests areessential for early identification of Nocardia species.
    Methods
    155 soil samples from different regions of North Khorasan province in Iran were collected, including: urban and rural areas. Isolation of Nocardia was performed by paraffin baiting Technique. Identification of Nocardia species was performed by phenotypic methods that are including: hydrolysis of the amino acids, acid production of carbohydrates and, growth at 35° C and 45°C.
    Results
    From 155 soil samples, 8 isolates (5.2%) were identified as the genus Nocardia. These bacteria were related to the gardens, the sands soils, and soil of town square. No growth was observed at 45°C. As the result, our isolates were identified as Nocardia asteroides complex.
    Conclusion
    Isolation and identification of Nocardia spp. from soil of different regions in North Khorasan province in Iran can help to enhance our understanding of epidemiological and ecological of the pathogenic Nocardia species.
  • Ali Ahmadi, Farzaneh Khodaei, Maryam Esghaei, Gholamreza Irajian, Malihe Talebi Pages 15-20
    Introduction
    Streptococcus pneumoniae (S. pneumoniae) cause morbidity and mortality in infants and younger children. Because of high prevalence of penicillin resistance, rapid and reliable diagnostic techniques for penicillin non-susceptible S. pneumoniae (PNSSP) are important for prevention and treatment. We investigated the association of the restriction length polymorphism (RFLP) patterns for pbp2b to distinguish between penicillin susceptible and resistant S. pneumoniae isolates.
    Methods
    In this study, a total of 70 pneumococcal isolates were collected from different clinical sources. MIC of these isolates was determined and pbp2b gene was amplified by PCR and they were digested by HaeІІІ enzyme.
    Results
    Of the 70 isolates, 86% (60) and 14% (10) pneumococcal isolates were found to be PNSSP (penicillin intermediate S. pneumoniae (PISP) and penicillin resistant S. pneumoniae (PRSP)) and penicillin susceptible S. pneumoniae (PSSP). In addition, 10 RFLP patterns (A-J)which were based on the HaeІІІ digestion of pbp2b gene were observed. All PSSP isolates showed that they belonged to pattern D, whereas, all PNSSP showed 10 different patterns.
    Conclusion
    In general, the present study suggests that RFLP can be a powerful tool in differentiation between the penicillin resistant and susceptible strains.
  • Hassan Hashemi, Mahdi Safari, Abbas Khodabakhshi Pages 21-26
    Introduction
    Antibiotics have the potential to adversely affect the microbial community. For anaerobic digestion, a sufficient methanogenic population needs to be preserved in the system.The main aim of this study was determination of inhibitory concentration of oxytetracycline on methanogenic bacteria.
    Methods
    A 120 mL jacketed bioreactor with a 90 mL working volume was inoculated granular sludge from an anaerobic digester, substrate and different concentration of oxytetracycline with 10 days cycles and intermittent mixing. The reactor was operated at 35 ± 2 ° C. The inhibitoryeffect of antibiotic was evaluated by monitoring biogas production.
    Results
    Based on the findings from each batch, complete inhibitory concentration of oxytetracycline was in concentration of 800 mg L-1.Significant relation was seen between inoculated antibiotic concentrations and methane production (r=-0.86).
    Conclusion
    The addition of antibiotics to the biomass affected the utilization of fatty acids, resulting in unfavorable effects on methanogenesis. Thus, overusing of antibiotics can adverse effects of intestinal flora.
  • Rashid Ramazanzadeh, Samaneh Rouhi, Pegah Shakib Pages 27-34
    Introduction
    ESBLs are a B -lactamases which had ability to hydrolyse third-generationcephalosporins and aztreonam. ESBLs producer bacteria are resistant to a wide variety of antimicrobials and they made a serious global health concern for treatment strategies. So, aim of this study as to molecular detection of ESBLs in bacteria isolated from blood cultures in Hospitals from Kurdistan Province, Iran.
    Methods
    Biochemical test, antimicrobial susceptibility test by disc method, ESBL detection by NCCLs Phenotypic and PCR method for ESBL detection were applied. Results were analyzed by using SPSS 11.5 (p < 0.05).
    Results
    96 gram negative bacilli isolated from blood cultures, E. coli, Enterobacter spp.,Klebsiella spp., P. aeruginosa, Salmonella spp., C. freundii, S. maltophilia, also S. aureus, and S.epidermis. Maximum resistance was 75% for CP and minimum resistance was 25% for GM. Of the 96 isolates, 20 (20.83%) produced ESBLs. Also 11.46%, 20.83%, 12.5%, 9.38% and 2.08% were positive for TEM, CTX-M, SHV, OXA-1 and OXA-2 ensymes, respectively.
    Conclusion
    Inappropriate therapy for infections with ESBL producers is cause of prolongs hospital stay and mortality. So, more research on drug resistance with ESBL is necessary.
  • Reza Khashei, Hadi Sedigh Ebrahim, Saraie, Mohammad Motamedifar, Mehrdad Zalipour, Jamal Sarvari Pages 35-42
    Introduction
    Biofilm producing Staphylococcus aureus is known as one of the major causative agents of infections, failure of implanted devices and persistent infection among hospitalized patients. The aim of the present study was to determine the frequency of biofilm producing S. aureus isolates amongst the clinical specimens.
    Methods
    This cross-sectional study was conducted during 2012 to 2013 in two teaching hospitals in Shiraz, southwest of Iran. Totally, 345 S. aureus isolates from various clinical specimens were included. Biofilm producing isolates were phenotypically detected using Congo Red Agar (CRA) and genotypically by PCR assay for the icaA and icaD genes.
    Results
    Of the 345 S. aureus isolates, 42.3% were methicillin-resistant S. aureus (MRSA) and subsequently 57.7% were methicillin susceptible isolates. The results of CRA plates showed that 77 (52.7%) and 74 (37.2%) of MRSA and MSSA were biofilm producing isolates. The frequency of icaA/D genes among MRSA and MSSA isolates was 127 (87%) and 167 (83.9%), respectively.
    Conclusion
    Such a high rate of icaA/D harboring S. aureus among clinical isolates suggest the risk for establishing persistent infections in the hospital settings.
  • Ahmadreza Zarifian, Yasin Setayesh, Emran Askari, Aminreza Amini, Mohammad Rahbar, Mahboubeh Naderinasab Pages 43-52
    Introduction
    Staphylococcus aureus is a prominent human pathogen. One of the drugs used in the treatment of staphylococcal infections (particularly infections of skin and soft tissue), is clindamycin. Resistance to clindamycin includes two types: inducible and constitutive. Routine laboratory methods of antibiotic susceptibility testing cannot detect the inducible type and Dtest is required for its detection. The purpose of this systematic review was to determine the relative prevalence of this type of resistance in Iran.
    Methods
    Search terms "inducible clindamycin resistant", "D-test", "Staphylococcus aureus" and "Iran" were used to find relevant articles in PubMed, Google Scholar and two Persian search engines. Also, the abstracts of the recent national microbiology congresses were checked. All studies used D-test to find iMLSB (inducible macrolide, lincosamide and streptograminB resistance) phenotype among clinical isolates (not nasal swabs) of S. aureus, were included. In order to perform meta-analysis, we used “comprehensive meta-analysis” software (ver. 2).
    Results
    In total, 9 articles and 8 abstracts related to the topic of the study were found. Random effects meta-analyses showed a pooled estimate for percentage of iMLSB phenotype among 2683 samples of S. aureus was about 10% (95% confidence interval: 0.07-0.12). Using the fixed effect model, the odds of positive iMLSB in methicillin-resistant S. aureus was about 5 times more likely to occur in comparison with methicillin-susceptible S. aureus (95% CI: 3.49 to 7.76).
    Conclusion
    Fortunately, the relative frequency of inducible resistance to clindamycin in our country is relatively low. However, we believe that D-test should be performed for all erythromicin-resistant isolates in order to identify inducible resistance to clindamycin. Moreover, reevaluation of inducible resistance to clindamycin in forthcoming years is highly recommended.
  • Mohammad Bokaeian, Barat Ali Fakheri, Nafise Mahdi Nejad, Mehdi Hassanshahian, Saeide Saeidi Pages 53-57
    Introduction
    Due to more resistance of pathogenic bacteria to new and current antibiotics researchers are looking to find the agents of herbal with antimicrobial activities in order to replace chemical drugs.
    Methods
    The herbal extract of Withani somnifera was done by using a rotary vacuum, 20 strains of Pseudomonas aeruginosa were isolated from urinary infections hospitalized patients in city of Zabol hospital. The MIC Withani somnifera were determined by dilution method in various concentrations. Sensitivity of strains to multiple antibiotics was evaluated by standard disk diffusion Kirby-Bauer.
    Results
    The result showed that P. aeruginosa were resistance to 4 of the agents including ampicillin (85%), nitrofurantoin (65%), nalidixic acid (65%), ciprofloxacin (15%) and for 5 strains of Pseudomonas showed MIC with activity of 100 ppm.
    Conclusion
    This study has suggested the effect of winter cherry extract on P. aeruginosa in the in vitro assay. It s effectiveness of on in vivo system can be examined in future.
  • Detection of icaA/icaD Genes and Biofilm Formation among Clinical Isolates of Staphylococcus aureus from Shiraz, Iran
    Reza Khashei, Hadi Sedigh Ebrahim, Saraie, Mohammad Motamedifar, Mehrdad Zalipour, Jamal Sarvari Page 58
    Introduction
    Biofilm producing Staphylococcus aureus is known as one of the major causative agents of infections, failure of implanted devices and persistent infection among hospitalized patients. The aim of the present study was to determine the frequency of biofilm producing S. aureus isolates amongst the clinical specimens.
    Methods
    This cross-sectional study was conducted during 2012 to 2013 in two teaching hospitals in Shiraz, southwest of Iran. Totally, 345 S. aureus isolates from various clinical specimens were included. Biofilm producing isolates were phenotypically detected using Congo Red Agar (CRA) and genotypically by PCR assay for the icaA and icaD genes.
    Results
    Of the 345 S. aureus isolates, 42.3% were methicillin-resistant S. aureus (MRSA) and subsequently 57.7% were methicillin susceptible isolates. The results of CRA plates showed that 77 (52.7%) and 74 (37.2%) of MRSA and MSSA were biofilm producing isolates. The frequency of icaA/D genes among MRSA and MSSA isolates was 127 (87%) and 167 (83.9%), respectively.
    Conclusion
    Such a high rate of icaA/D harboring S. aureus among clinical isolates suggest the risk for establishing persistent infections in the hospital settings.
  • Inducible Clindamycin Resistant Staphylococcus aureus in Iran: A Systematic Review and Meta-analysis
    Ahmadreza Zarifian, Yasin Setayesh, Emran Askari, Aminreza Amini, Mohammad Rahbar, Mahboubeh Naderinasab Page 59
    Introduction
    Staphylococcus aureus is a prominent human pathogen. One of the drugs used in the treatment of staphylococcal infections (particularly infections of skin and soft tissue), is clindamycin. Resistance to clindamycin includes two types: inducible and constitutive. Routine laboratory methods of antibiotic susceptibility testing cannot detect the inducible type and Dtest is required for its detection. The purpose of this systematic review was to determine the relative prevalence of this type of resistance in Iran.
    Methods
    Search terms "inducible clindamycin resistant", "D-test", "Staphylococcus aureus" and "Iran" were used to find relevant articles in PubMed, Google Scholar and two Persian search engines. Also, the abstracts of the recent national microbiology congresses were checked. All studies used D-test to find iMLSB (inducible macrolide, lincosamide and streptograminB resistance) phenotype among clinical isolates (not nasal swabs) of S. aureus, were included. In order to perform meta-analysis, we used “comprehensive meta-analysis” software (ver. 2).
    Results
    In total, 9 articles and 8 abstracts related to the topic of the study were found. Random effects meta-analyses showed a pooled estimate for percentage of iMLSB phenotype among 2683 samples of S. aureus was about 10% (95% confidence interval: 0.07-0.12). Using the fixed effect model, the odds of positive iMLSB in methicillin-resistant S. aureus was about 5 timesmore likely to occur in comparison with methicillin-susceptible S. aureus (95% CI: 3.49 to 7.76).
    Conclusion
    Fortunately, the relative frequency of inducible resistance to clindamycin in our country is relatively low. However, we believe that D-test should be performed for all erythromicin-resistant isolates in order to identify inducible resistance to clindamycin. Moreover, reevaluation of inducible resistance to clindamycin in forthcoming years is highly recommended.
  • Study the Withani somnifera extraction against resistant strains of Pseudomonas aeruginosa
    Mehdi Hassanshahian Page 60
    Due to more resistance of pathogenic bacteria to new and current antibiotics researchers are willing to find the agents of herbal antimicrobial in order to replacing chemical drugs.
    Material And Method
    The herbal extracts of Withani somnifera were done by using a central vacuum (rotary). 17 strains of pseudomonas aeruginosa were isolated from urinary infections hospitalized patients in zahedan hospital. The MIC Withani somnifera were determined by dilution method in various concentrations. Sensitivity of strains to multiple antibiotics was evaluated by standard disk diffusion Kirby-Bauer.
    Result
    Isolated Pseudomonas was resistant to antibiotics: cefexime (11.94%) and ceftazidime (52.23%).for 5 strains of pseudomonas were in MIC 100ppm.
    Discussion
    This (present) study has suggested the effect of winter cherry extract on found bacteria in laboratory.it can be indicated to the effectiveness of them on alive system.
  • Inducible clindamycin-resistant Staphylococcus aureus in Iran: a systematic review and meta-analysis
    Ahmadreza Zarifian Page 61
    Background And Objectives
    Staphylococcusaureus is a prominent human pathogen. One of the drugs used in the treatment of staphylococcal infections (particularly infections of skin and soft tissue), is clindamycin. Resistance to clindamycin includes two types: inducible and constitutive. Routine laboratory methods of antibiotic susceptibility testing cannot detect the inducible type and D-test is required for its detection. The purpose of this systematic review was to determine the relative prevalence of this type of resistance in Iran.
    Methods
    Search terms «inducible clindamycin resistant», «D-test», «Staphylococcus aureus» and «Iran» were used to find relevant articles in PubMed, Google Scholar and two Persian search engines. Also, the abstracts of the recent national microbiology congresses were checked. All studies used D-test to find iMLSB (inducible macrolide, lincosamide and streptograminB resistance) phenotype among clinical isolates (not nasal swabs) of S. aureus, were included. In order to perform meta-analysis, we used “comprehensive meta-analysis” software (ver. 2).
    Results
    In total, 9 articles and 8 abstracts related to the topic of the study were found. Random effects meta-analyses showed a pooled estimate for percentage of iMLSB phenotype among 2683 samples of S. aureus was about 10% (95% confidence interval: 0. 07-0. 12). Using the fixed effect model, the odds of positive iMLSB in methicillin-resistant S. aureus was about 5 times more likely to occur in comparison with methicillin-susceptible S. aureus (95% CI: 3. 49 to 7. 76).
    Conclusion
    Fortunately, the relative frequency of inducibleresistance to clindamycin in our country is relatively low. However, we believe that D-test should be performed for all erythromicin-resistant isolates in order to identify inducible resistance to clindamycin. Moreover, reevaluation of inducible resistance to clindamycin in forthcoming years is highly recommended.
    Keywords: Staphylococcus aureus, inducible resistance, clindamycin, Iran, systematic review