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Volume 61, Issue 6 (9-2003)
Background: Staphylococci as a micro-organism, has the most importance to cause nosocomial infections, particularly in patients with indwelling catheters or other medical devices. Unfortunately 90% of Staphylococci isolated from the nosocomial infections are resistant to methicillin, and methicillin resistance strains are also resistant to a wide range of antimicrobial drugs, therefore detecting of these strains are valuable to eradicate the infection elements. Despite guidelines published by the national committee for clinical laboratory standards (NCCLS) for testing of susceptibility to methicillin for Staphylococci, the phenotypic method for detecting methicillin resistance remains controversial. Therefore, the genetic assays have been used to detect antimicrobial susceptibility of Staphylococci to methicillin.
Materials and Methods: Resistance to methicillin is coded by mec A gene in staphylococcus, and this gen must be detected in genetic assays. In this study 155 clinical staphylococcal isolates (70 coagulase- negative staphylococcus and 85 coagulase- Positive staphylococci) were evaluated for susceptibility to methicillin by using disk diffusion method.
ResuIts&Conclusion: Methicillin resistance was shown in 62 coagulase- negative staphylococcus (72.9%) and 27 coagulas positive staphylococcus (38.6%) but 63 coagulase negative Staphylococci (74%) and 28 coagulase positive isolates with mec a gene associated resistance were detected by PCR method. The results of this test were compared to the results for mec A gene detection by PCR test as a gold standard. The sensitivity, specifity and accuracy of the disk diffusion test for coagulase-negative staphylococcus were 96.8%, 95.45% and 96.47% and for coagulase positive staphylococci were 98.43%, 95.45% and 98.32% respectively.
Volume 65, Issue 3 (6-2007)
Background: Staphylococcus aureus is one of the most common causes of nosocomial infections with high morbidity and mortality rate. Traditionally, methicillin resistant staphylococcus aureus has been considered a major nosocomial pathogen in healthcare facilities, but in the past decade, it has been observed emerging in the community as well. Informations regarding hospital microbial colonization could be an important step for prevention of nosocomial infections. Our objective was clarifying the prevalence of methicillin resistant and vancomycin resistant staphylococcus aureus colonization in nasopharynx.
Methods: A descriptive cross sectional study was carried on 106 patients and nursing staff of surgery and hemodialysis wards in Amir-Alam hospital from April 2005 to July 2005. The samples were collected from nasal region of cases using cotton swab by two experienced technician and were sent to laboratory for culture and antibiogram.
Results: Twenty six (29.5%) out of 106 cases were nasopharyngeal carriers of staphylococcus aureus. Eight cases (7.5%) had methicillin resistant staphylococcus aureus. The most frequent colonization rate was seen in hemodialysis nursing staff and in all of them methicillin resistant staphylococcus aureus was reported. Carrier rates in hemodialysis patients were twice compared to surgery ward patients. The interesting point was that no sample of vancomycin resistant staphylococcus aureus was isolated.
Conclusion: Prevalence of methicillin resistant staphylococcus aureus colonization seems to be increased therefore proper management for controlling this problem is mandatory. The results of the present study suggest that the prevalence of methicillin resistant staphylococcus aureus infections is higher than was expected in Iran and vigorous preventive strategies should therefore be taken to stop the growth of this major health problem.
Volume 67, Issue 7 (10-2009)
Background: Staphylococcus aureus is a major foodborne pathogen throughout the world. Enterotoxins and toxic shock syndrome toxin-1 are important virulence factors and as pyrogenic toxin superantigens have profound effects on the ir host. Thus circulation of TSST1 producing S.aureus among people and food chain is a worrying issue. The present paper was conducted to study Prevalence of tst, entC, entA and entA/C genes in staphylococcus aureus strains isolated from different foods.
Methods: Over 1040 food samples have been analyzed differentially according to Iran national standard (number= 1194) for S.aureus identification. After DNA extraction, PCR reactions were carried out by reference strain as positive control, adequate primers.
Results: At present study, prevalence of foodstuffs contaminated by S.aureus isolates was about 9.5% (100 strains). Of 25% of isolates producing entC, 28% (seven strains) had tst gene at the same time and of 8% of isolates producing entA, 12.5% (one strain) were positive for tst genes simultaneously. Altogether of 9% isolates producing combination of entC and entA, 44.4% (four strains) were also producer of tst gene.
Conclusion: Prevalence of TSST1 producing strains in combination with enterotoxin genes is considerable especially with entC and A plus C. On the other hand, circulation of these isolates in humans, animals, foods and environment has hazardous effect for general public health.
Volume 69, Issue 6 (9-2011)
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MicrosoftInternetExplorer4 Background: Staphylococcus aureus infection pervasively occurs in communities and
hospitals and observing related guidelines is essential in preventing development
of antibiotic resistance in Hospitals. In this study we tried to determine the
prevalence of Methicillin and vancomycine resistant staphylococcus aureus (MRSA
& VRSA) and find the most suitable diagnostic tool and
treatment in affected patients.
Methods: This study was performed on hospitalized patients in Sina Hospital in Tehran,
Iran during 2009-2010. Eighty-five staphylococcus
aureus samples were evaluated for resistance to oxacillin and vancomycine
by both disc diffusion and E-test methods.
Results: The study population included 46 male and 39
female patients. The mean age of the participants was 51.46±19.21
years. The MRSA frequency was 50%.
67 (78.8%) patients had hospital-acquired
staphylococcus infection. The rate of hospital-acquired MRSA
was 93%. Length of hospital stay, undergoing invasive
methods, history of antibiotic use three months prior to hospitalization and its
kind were recognized as MRSA risk factors. There
were no reports of VRSA except one case of vancomycine-intermediate
S. aureus (VISA). The results of disk effusion and E-test
methods were consistent.
Conclusion: Considering
the prevalence of methicillin resistance in hospital-acquired infections, it seems
that oxacillin should not be used as the first-line option for empiric therapy
against S. aureus till
antibiogram results are available. Disc diffusion can also be reliably used
instead of the more expensive E-test.
Volume 70, Issue 9 (12-2012)
Background: Staphylococcus aureus is the most common pathogen responsible for skin and soft tissue infections worldwide. Methicillin-resistant S. aureus is a major cause of both nosocomial and community acquired infections. The emergence of antimicrobial-resistant S. aureus is of global concern. Fluoroquinolone antimicrobials including ciprofloxacin, levofloxacin, and moxifloxacin are used to treat skin and soft tissue infections due to S. aureus. Emergence of ciprofloxacin resistance has increased in community acquired methicillin-resistant S. aureus strains. The aim of this study was to evaluate the minimum inhibitory concentration of ciprofloxacin and hexahydroquino-line derivatives against methicillin- and ciprofloxacin-resistant S. aureus.
Methods: Identification of S. aureus was performed by routine microbiological tests in the Department of Pathobiology in Winter 2012. The susceptibility of S. aureus strains to both methicillin and ciprofloxacin was examined by the Kirby-Bauer disk-diffusion method. The minimum inhibitory concentration of ciprofloxacin, hexahydroquinoline derivatives and their combination were separately determined by broth microdilution method against methicillin- and ciprofloxacin-resistant S. aureus.
Results: The minimum inhibitory concentration of ciprofloxacin decreased in the presence of hexahydroquinolinein derivatives in comparison with ciprofloxacin alone.
Conclusion: This study showed that hexahydroquinoline derivatives enhance the antibacterial effect of ciprofloxacin against methicillin- and ciprofloxacin-resistant S. aureus. Therefore, these derivatives could be used as inhibitors of antibiotic resistance in combination therapies. This enhancement may be related to the inhibitory effect of hexahydroquinoline derivatives on the expression of antibiotic efflux pump in the bacteria. However, the structural features of a fluoroquinolone that determine whether it is affected by efflux transporters are not fully defined.
Volume 72, Issue 2 (5-2014)
Background: Toxic shock syndrome (TSS), a dangerous consequence of Toxic shock syndrome toxin-1 (TSST-1) caused by Staphylococcus aureus. The early detection for infections of Staphylococcus aureus in burned children is very important, also the pre-vention for consequences of TSST-1. Fever is one of the most noticeable sign in burned children. On the other hand, fever is one of the important consequences of TSST-1 pro-duction. Methods: This study aimed to assess the toxic shock syndrome toxin-1 level in the wound’s specimens of two groups febrile and afebrile in the hospitalized burned chil-dren in Motahari hospital Tehran, Iran in the year 2013. In this case-control study, 90 children who admitted to the burn unit, divided in two groups of 45 patients: febrile (cases group) and afebrile (control group). All of burned children under went wound biopsy, and then all of wound’s specimens were tested by PCR for specific primer of toxin producing genome. Finally all of data collected and statistically analyzed. This data include group febrile and afebrile, demographic characteristics, percentage of burned surface severity and result of PCR. Results: The positive result for PCR test, production of TSST-1 in febrile burned chil-dren (cases group) was 37.7% and in afebrile burned children (control group) was 11.1% that this different was statistically significant (P=0.003). The mean and stan-dard deviation for percentage of burned surface (severity) in samples with positive re-sult for PCR test was 30.9±16.93 and in samples with negative result for PCR test was 20.09±11.02 that this different was statistically significant (P=0.01). There was no dif-ference between positive PCR result and negative PCR result of age and sex. Conclusion: Direct association was approved between the production of TSST-1 and the occurrence of fever in burned children. Increased surface severity of burns also re-lated to the production of TSST-1. Further research is recommended.
Volume 73, Issue 1 (4-2015)
Background: Staphylococcus aureus is the most important cause of nosocomial infections acquired in the community. Protein A is a major component of Staphylococcus aureus cell wall. In analysis of the nucleotide sequence Protein A encoding spa, locus x consists of 24 base pairs which repeat with high polymorphism. In this study, the spa gene of Staphylococcus aureus isolated from clinical specimens were obtained from patients admitted to the hospital and healthy carriers. Methods: In a cross-sectional study, a total of 200 samples were collected. One hundred fifty samples were obtained from hospitalized patients and 50 samples obtained from staff nasal swabs in Hamadan University Hospitals from October 2013 to August 2014. Disk diffusion antibiotic susceptibility tests performed. The antibiotics studied were Vancomycin (30 µg), Cefoxitin (15 µg) Gentamicin (10 µg), Tetracycline (30 µg), Trimethoprim/sulfamethoxazole (25 µg), Ciprofloxacin (5 µg), Erythromycin (15 µg), Clindamycin (2 µg), Rifampin (5 µg). The tests performed according to the guidelines of clinical and laboratory standards institute (CLSI). It also detect the mecA gene of Methicillin-resistant Staphylococcus aureus strains (MRSA) and genes spa which encodes the protein A by polymerase chain reaction (PCR). The PCR products using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method with enzyme Rsa I (Afa I) were prepared. Results: This methicillin-resistant Staphylococcus aureus strain (MRSA) had the highest sensitivity and resistance to ciprofloxacin and clindamycin. Totally, 8 amplicon with different sizes for the spa gene were identified. A total of 9 patterns polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP) were found. Some of these patterns between Staphylococcus aureus isolated from clinical specimens and nasal carriers were common. Conclusion: There is a similar pattern of spa gene among patients admitted to the hospital and staff, according to our findings. Analysis of the patterns can reduced transmission of infection in both hospital staff and patients. Also it can help the physicians for correct management of infections.
Volume 73, Issue 11 (2-2016)
Background: Staphylococcus aureus is a gram positive coccus which is able to cause different kinds of infection in certain condition. The function of this bacteria is to provide the conditions for the invasion of it to the host with the secretion of different sorts of toxins such as Staphylococcus aureus enterotoxin, including important virulence factors that super antigens are all factors digestive inconvenience. Staphylococcus aureus enterotoxin-secreting toxins such conditions provides invasion of host genes. There are different types of SE, but type A enterotoxin (SEA) and type B enterotoxin (SEB) are the most important types. Therefore, in this study, the prevalence of Staphylococcus aureus toxin-producing enterotoxin genes (SEB, SEA) in clinical strains isolated from patients in teaching hospitals of Shahrekord city, Iran, were studied.
Methods: This cross-sectional and descriptive study, which was conducted from May 2014 to December 2014. A hundred and ten isolates of Staphylococcus aureus from patients collected over a period of 8 months and were first identified using standard biochemical methods and laboratory. Using standard methods and laboratory tests were identified and compared with the antibiotic oxacillin minimum inhibitory concentration were determined by broth micro dilution, and then they were assessed by polymerase chain reaction (PCR) technique.
Results: The results indicated that, 110 samples of dairy products infected by Staphylococcus aureus were detected. Two cases (1.8%) of these infected samples were carrying both enterotoxin A and enterotoxin B genes. The frequencies of enterotoxin A genes were twenty-six cases (23/6%) and The frequencies of enterotoxin B genes were two cases (1/8%), respectively.
Conclusion: The detection of enterotoxin A and enterotoxin B genes, shows the most important role they have in bringing about superinfection. The detection of enterotoxin A and B genes, shows the most important role they have in bringing about superinfection. Enterotoxins SEA and SEB are heat stable; therefore heating has no effect on dairy products contaminated by enterotoxins and gastritis may occur in a short period of time. As PCR is a rapid, sensitive, specific and inexpensive method, we suggest that it can be replaced to traditionally assays for detecting Staphylococcus aureus enterotoxin.
Volume 75, Issue 2 (5-2017)
Background: Electrolysis is an electrochemical method for the treatment of water. recently water disinfection by electrochemical methods has been increasingly carried out. The aim of this applied research was to investigate the removal of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria from drinking water by using electrolysis method with Al-Fe electrodes parallel with the monopole mode.
Methods: An experimental study was conducted in the laboratory of microbiology, Iran University of Medical Science in May 2017. In this study, the contaminated water samples were prepared through adding 103, 104 and 105 E. coli and S. aureus bacteria per 1 milliliters (mL) of drinking water. Independent variables Included: different concentrations of E.coli and S. aureus bacteria (103, 104 and 105 CFU/ml), reaction time (5, 10, 15, 20 and 25 min), initial pH (7, 8 and 9), electrode gap (1, 2 and 3 cm), current density (0.83, 1.67 and 3.3 mA/cm2) to determine the optimum conditions were investigated. One-way ANOVA was used to analyze the results.
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Results: The results show that in the optimum conditions with increasing the pH from 7 to 9 removal efficiency of bacterial strains of E. coli and S. aureus were decreased significantly from 98 to 73% and 99.1 to 76%, respectively. In initial concentration of 104 CFU/ml, optimum conditions were obtained for current density, reaction time and electrodes gap, 1.67 mA/cm2, 20 min and 2 cm, respectively. With increasing current density and reaction time in both strains of bacteria, were decreased significantly. The electrodes gap do not have much impact on the efficiency of the process. The amount of electrical energy consumed in optimal conditions was calculated 0.5128 kilowatt-hour (kWh/h). Statistical analysis shows that exist significant relationship (P<0.01) between initial concentrations of bacterial strains and efficiency of the process. Conclusion: According to the results, E. coli and S. aureus, removal efficiency were obtained more than 98%, therefore electrolysis process can be used in the removal of pathogenic bacteria from drinking water. |
Volume 77, Issue 4 (7-2019)
Methods: In this cross-sectional study, one-hundred fifty isolates of S. aureus from urine and blood samples of patients that collected from educational hospitals of Imam Hossein and Al Zahra Isfahan University of Medical Sciences, Iran, from February 2018 to October 2018 were analyzed. After bacterial confirmation of isolates by Coa gene in polymerase chain reaction (PCR) technique, to perform coagulase gene typing, the repeated units encoding hypervariable regions of the coagulase gene of S. aureus were amplified by PCR. This was followed by AluI restriction enzyme digestion and analysis of restriction fragment length polymorphism (RFLP) patterns.
Results: Of 150 samples, 45 isolated of S. aureus were confirmed by biochemical methods. Of previous positive samples, 36 (80%) isolates carried Coa gene. Two different genotypes of Coa gene were obtained that include bp680 fragment in 20 specimens and bp750 fragment in 16 specimens. After enzymatic digestion by AluI restriction enzyme for RFLP, four different restriction patterns were obtained that including, the 280+400 pattern in 16 specimens (44.4%), 280+470 pattern in 7 specimens (19.4%), 340+340 pattern in 6 specimens (16.6%) and 750 patterns without digestion were in 7 specimens (19.6%).
Conclusion: Using the present experiments, it was determined that the PCR-RFLP pattern, 280+400, was the dominant pattern in the Staphylococcus aureus samples isolated in Isfahan.
Volume 77, Issue 4 (7-2019)
Methods: In this retrospective study, infective endocarditis patients who were admitted to Sina and Ekbatan hospitals in Hamadan City, Iran, from March 2005 to February 2014, were enrolled. All demographic data, clinical manifestations, physical examinations and echocardiography reports of the patients were recorded in a check list. For all patients, blood cultures in Mueller Hinton agar and antimicrobial susceptibility testing for ceftriaxone, ceftazidime, oxacillin, cefazolin, vancomycin, imipenem, clindamycin, etc. were done by disk diffusion method. All data analyzed by SPSS statistical software, version 16 (IBM, Armonk, NY, USA).
Results: A total of 61 patients with definitive infective endocarditis were included in the study, 50 of them (82%) were males and 11 patients (18%) were females. The mean age of the patients was 37.45±14.79 (range 17-74) years and 37 (60.7%) of the patients lived in urban areas. The mean duration of admission was 20±13.59 days. In addition, 38 patients (62.3%) were injection drug users (IDUs) and 23 (37.7%) non-IDU. Meanwhile, 54 (88.5%) of them had normal valve endocarditis and 7 cases (11.5%) had a prosthetic valve endocarditis. Moreover, the most common underlying disease in the natural valve endocarditis was rheumatoid fever (6.6%). Blood cultures were positive in 44.3% of the patients. The most common isolated organism was staphylococcus aureus in 15 cases (55.55%), which had the highest resistance to oxacillin. Most patients were managed by antibiotic therapy, but 15 cases (24.6%) underwent cardiac surgery. In follow up patients between 3 months to 9 years, 19.7% of the patients had complete recovery and 8.2% of them died.
Conclusion: According to the findings, antibiotic resistance pattern of bacterial agents isolated from blood culture of patients with infective endocarditis was changed.
Volume 80, Issue 7 (10-2022)
Methods: In this descriptive cross-sectional study from September 2021 to February 2022, the blood and wound samples of the patients were collected and referred to laboratory. Staphylococcus aureus had identified by phenotypic and biotypic tests. MRSA isolates were screened by showing resistance to Cefoxitin by disc diffusion method and finally confirmed by examining the mecA gene by PCR. The microbial resistance pattern of MRSA was also measured by disk diffusion method and resistance to Vancomycin was confirmed by E.test.
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Results: 41 isolates from 87 Staphylococcus aureus samples were confirmed as MRSA by present the mecA gene. The mecA gene was detected in all MRSA by PCR method. The antibiotic resistance pattern showed the highest sensitivity to Vancomycin and Linezolid with 100% sensitivity and the highest resistance to three antibiotics Erythromycin, Ceftriaxone and Cloxacillin with 97.57%by disk diffusion method. The most MRSA strains were isolated from the ICU department with 13 cases and the least MRSA strains were isolated from the two NICU and pediatric departments with one case.The majority of the population infected with MRSA belonged to the age group of 40-65 years.
Conclusion: The prevalence of microbial resistance with high dispersion was obtained among MRSA strains isolated from clinical samples; which indicates a significant increase in resistant strains and requires a quick and timely diagnosis to prescribe the appropriate antibiotic. |
Volume 81, Issue 10 (1-2024)
Background: Today, Methicillin-Resistant Staphylococcus Aureus (MRSA) has become one of the public health concerns due to its resistance to antimicrobial drugs, and this problem makes treating patients with infections caused by this bacterium difficult. Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) strains are pervasive in both community and hospital settings, primarily attributable to Staphylococcus aureus' capacity to colonize areas like the nose or skin. In this study, with the aim of comparing phenotypic (disc diffusion method) and genotypic (PCR) methods, to detect methicillin-resistant Staphylococcus aureus isolated from patients of hospitals under supervision of Tehran university of medical sciences, and also detection of nor A, that is the one of the most important genes in efflux pump cluster genes.
Methods: The present research was a cross- sectional study that was conducted from February 2022 to September 2023. In this research, 43 isolated strains of Staphylococcus aureus from wound discharge and blood samples, were collected from different departments of Tehran hospitals and had submitted to the research laboratory of the school of allied medical sciences in Tehran university of medical sciences. After identifying the strains, the resistance of the isolates to 14 types of antibiotics was checked by disk diffusion method.
| Results: Staphylococcus aureus diagnostic tests including gram staining on colonies, catalase, coagulase, DNase tests were performed and it was found that all strains were Staphylococcus aureus. In the next step, all samples were resistant to Cloxacillin by disc diffusion method, and the presence of mec A gene in them was confirmed by PCR method, thus the presence of MRSA strains was confirmed from the genotypic point of view. Of the 43 Staphylococcus aureus strains, 26 samples were identified as having the nor A gene by PCR and electrophoresis. Conclusion: The results of the present research have shown that the prevalence of Staphylococcus aureus bacteria in hospital samples is significant and resistance to methicillin and ciprofloxacin has increased in the strains of this bacteria. |
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