Showing 8 results for Virulence
A Talebi Bezminabadi, T Taghvaei,
Volume 8, Issue 1 (4-2014)
Abstract
Abstract
Undoubtedly, H. pylori is the major human gastric pathogen, which infects the mucosal epithelium in 50% of world population. However, H. pylori infection is relatively prevalent globally the majority of infected individuals are asymptomatic. The recent epidemiological studies show that the various gastro intestinal complications can be the result of genetic variation in H. pylori strains. To date, different virulence factors had been suggested for H. pylori, but none of them can be a good biomarker for specific gastric disorders. In this review article, we aim to describe a comprehensive view on what we found in H. pylori virulence research in Iran. Hopefully, in parallel with new advances in sequencing systems, we will have better overview of virulence phenomenon of H. pylori in near future.
Keywords: Helicobacter pylori, Iran, virulence, homB, dupA
Hadi Koohsari , Ezzat Allah Ghaemi , Nour Amir Mozaffari , Abdolvahab Moradi ,
Volume 10, Issue 1 (1-2016)
Abstract
Abstract
Background and Objective: Agr is the most important regulatory system for the expression of Staphylococcus aureus virulence factors in different conditions. Agr acts as a quorum sensing system in this bacterium which is activated by increased cell concentration during the transition from logarithmic growth phase to stationary phase. Its role is to upregulate the secretory virulence factors such as alpha-hemolysin and inhibit the transcription of surface proteins including protein A-encoding gene. The aim of this study was to assess the relationship between the agr system expression and some virulence factors of Staphylococcus aureus in Brain-heart infusion (BHI) culture medium.
Methods: The expression level of agrA and RNAIII genes from the agr locus along with the expression of hla, spa and mecA genes in BHI broth were assessed in different growth phases using Real time-PCR. Also, gyrB was used as an internal control in this study.
Results: The growth curve of the five tested isolates in BHI broth at 24 hours showed that all the isolates had relatively similar growth patterns. AgrA gene expression in the stationary phase was decreased by 0.89-fold compared with the logarithmic phase. Although the expression of RNAIII gene increased by 3-fold, hla expression decreased by 0.47-fold.
Conclusion: An inactive agr system is observed in the BHI broth medium. BHI broth medium contains high amounts of suitable nutrients for the growth of Staphylococcus aureus, thus the bacteria do not require the activity of the agr system for the regulation of the virulence genes in these conditions.
Leili Shokoohizadeh,
Volume 10, Issue 2 (3-2016)
Abstract
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.
Rhokhsareh Akbari, Leila Asadpour,
Volume 11, Issue 1 (1-2017)
Abstract
ABSTRACT
Background and Objectives: Klebsiella pneumoniae is one of the most important nosocomial pathogens. Its capsular polysaccharide is considered as the first and most important virulence factor of this bacterium. This study aimed to investigate the presence of capsular serotypes K1 and K2 in K. pneumoniae isolates to examine the virulence potency of the isolates.
Methods: Overall, 65 capsulated K. pneumoniae isolates were collected from patients with urinary tract infections in Rasht, Iran. The isolates were examined using biochemical tests and CPS gene amplification using PCR. Mucoid phenotype of the isolates was determined by the string test. The presence of K1 and K2 genes was evaluated by PCR using specific primers for the genes.
Results: Of 65 K. pneumoniae isolates, seven (10.77%) were positive for the presence of the K1 gene and four (6.15%) were positive for the presence of the K2 gene. In addition, six serotype K1 isolates (27.27%), four serotype K2 isolates (18.18%), and 12 non-K1/K2 serotype isolates (54.54%) had hypermucoviscosity phenotypes.
Conclusion: Our results confirm the presence of the capsular serotypes in K. pneumoniae isolates, with a relatively high prevalence for the capsular serotype K1. This study clarifies the importance of rapid diagnosis and suitable treatment of infections caused by K. pneumoniae in prevention of complicated infections.
Keywords: Klebsiella pneumoniae, Virulence factors, Capsular polysaccharide.
Azizollah Ebrahimi, Younes Daryalal, Mohamadreza Mahzounieh, Sharareh Lotfalian,
Volume 12, Issue 4 (7-2018)
Abstract
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.
Mahsa Yazdi, Majid Bouzari, Ezzat Allah Ghaemi,
Volume 12, Issue 5 (9-2018)
Abstract
ABSTRACT
Background and objectives: Urinary tract infections (UTIs) are one of the most common infectious diseases caused by bacteria. The primary etiologic agent of UTIs is Escherichia coli. Uropathogenic E.coli (UPEC) strains have a number of specific virulence factors, which can worsen UTIs. This study was performed to detect fim, pap, sfa and afa genes among E.coli strains isolated from UTIs.
Methods: A total of 100 E. coli isolates from patients with UTI was collected between June and December 2015 from Mosavi and Sayyad Shirazi hospitals in Gorgan, Iran. All bacterial isolates were identified via standard biochemical testing and Gram straining. Presence of the genes was assessed by polymerase chain reaction.
Results: The frequency of the fim, pap, sfa and afa genes was 100%, 79%, 69% and 8%, respectively. All isolates contained at least one virulence gene. Prevalence of multiple adhesion genes was 6% for all genes and 65% for three genes (fim, pap and sfa) together. In addition, the frequency of the fim gene was significantly higher than that of the other genes (P<0.0001).
Conclusion: The results of this study indicate the high prevalence of virulence factors that can enhance pathogenicity of E. coli. Therefore, these factors could be used as diagnostic markers or vaccine targets.
Keywords: Virulence factors, Urinary tract infection, Uropathogenic Escherichia coli.
Azizollah Ebrahimi, Soheila Rabiaee, Sharareh Lotfalian, Saied Habibian,
Volume 14, Issue 4 (7-2020)
Abstract
ABSTRACT
Background and objectives: Clove (Syzygium aromaticum) essential oil is a food additive with proven antimicrobial and antioxidant properties. Thus, it may be a good candidate for controlling foodborne pathogens, such as Staphylococcus aureus. The aim of the present study was to evaluate effects of sub–minimum inhibitory concentrations (MICs) of clove oil on some virulence factors of S. aureus.
Methods: The standard strain and 12 field isolates of S. aureus were obtained from our microbial collections. The broth tube dilution method was used to determine the MIC of clove oil against the isolates. Sterile 96-well flat bottom polystyrene microtiter plates were used for planktonic growth and biofilm formation assays. Slide coagulase test was used for assaying effect of clove oil on clumping factor production. Production of α- and β-hemolysins was assessed by culture on 5% bovine blood agar.
Results: The results showed that sub-MIC concentrations of clove oil inhibited α- and β-hemolysins and biofilm production and planktonic growth of the examined isolates. However, clumping factor was not affected by sub-MIC concentrations of clove oil.
Conclusion: Our results indicate the favorable inhibitory effects of sub-MIC concentrations of clove oil against growth and biofilm and hemolysins production of S. aureus isolates.
Zahra Askari, Zeynab Mirzapour, Tooba Shafighi, Reyhaneh Ghorbanpour,
Volume 19, Issue 1 (1-2025)
Abstract
Background: Urinary tract infections (UTIs) caused by uropathogenic Escherichia coli (UPEC) represent a significant global health concern. Virulence factors (VFs) expressed by UPEC strains play a crucial role in promoting bacterial pathogenicity within the urinary tract. Effective treatment of these infections is frequently complicated by the high prevalence of antimicrobial resistance exhibited by Escherichia coli. The objective of this study was to investigate the VFs and antibiotic susceptibility profiles of UPEC strains isolated in the northern region of Iran.
Methods: One hundred and five urine specimens were collected from female patients diagnosed with UTIs in Rasht, located in the north of Iran. These samples underwent culturing on both Eosin Methylene Blue (EMB) agar and MacConkey agar. Following a 24-hour incubation period at 37°C, pure bacterial isolates were identified through Gram staining and a battery of standard biochemical assays. The prevalence of six VF genes - papC, sfa/foc, fimH, afa, ibeA, and neuC - within UPEC strains was determined utilizing polymerase chain reaction (PCR) and subsequently confirmed via direct sequencing. Antibiotic susceptibility testing (AST) was conducted using the disk diffusion method, adhering to the guidelines established by the Clinical and Laboratory Standards Institute (CLSI M02).
Results: The study identified 65.71% of the isolates as Escherichia coli. Among the virulence genes examined, fimH exhibited the highest prevalence (100%), while afa was the least frequent (1.44%). Antibiotic resistance analysis revealed the highest rate against Cefazolin (66.66%) and the lowest against Gentamicin (24.63%). Notably, the prevalence of multi-drug resistance (MDR) was determined to be 73.91%.
Conclusion: This study underscored the significance of localized surveillance of UPEC isolates. This emphasis stems from the pathogen's considerable capacity for genetic mutation, coupled with the influence of environmental variables and individual patient characteristics. Understanding these dynamic factors at a local level is crucial for formulating the most effective strategies to combat UTIs.
