Department of Bacteriology (1992 - Present)
Medical Microbiology
, Tarbiat Modares University,
bacteriology
, Tarbiat Modares University,
Laboratory sciences
, Tabriz University of Medical Sciences,
Some Staphylococcus aureus strains produce Panton-Valentine leukocidin (PVL), a bi-component pore-forming toxin, which causes leukocyte lysis and tissue necrosis. Currently, there is very limited information on the molecular epidemiology of PVL-encoding S. aureus strains in Iran. This study aimed to determine the molecular epidemiology and genetic background of PVL-positive S. aureus clinical strains isolated from Iranian patients. A total of 28 PVL-positive S. aureus strains were detected from 600 S. aureus isolates between February 2015 and March 2018 from different hospitals in Tehran, Iran. Antimicrobial susceptibility testing was performed according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Molecular genot
The ability of V. cholerae to survive and spread in the aquatic environment combined with the scarcity of effective antimicrobial agents, especially those effective against multidrug-resistant strains highlights the need for alternative non-antibiotic approaches for the treatment of V. cholerae infections. The aim of this study was to specifically examine the potential direct effect of unstimulated MSC secretome on V. cholerae killing and biofilm formation as a representative of non-invasive enteric bacterial pathogen. The bmMSCs were characterized by the presence of CD44 and CD73 and the absence of CD45 and CD34 molecular markers. Moreover, self-regeneration and differentiation capacity of MSCs into adipocytes and osteogenic lineages was a
Vaccines are the front line in the fight against diseases. However, setbacks with existing cholera vaccines have ignited a considerable effort to develop more suitable vaccine formulations. In this study, we aim to investigate the effect of antigen stability and controlled release in inducing an immune response. Therefore, two types of silica and carbon mesoporous nanoparticles of the same size and shape but different pore architectures were synthesized and loaded with recombinant cholera toxin subunit B to serve as a model for antigen stability and controlled release of antigenic CTB. In order to evaluate immune response efficacy for these model formulations, IgG and IgA responses and fluid accumulation (FA) index were measured in immunize
Background Regarding the role of gut microbial dysbiosis in hyperglycemia, we aimed to compare the main gut bacterial composition among type 1 and type 2 diabetic patients and healthy non-diabetic adults. Methods A total of 110 adult subjects (49 patients diagnosed with type 2 diabetes, 21 patients diagnosed with type 1 diabetes and 40 healthy persons) were included in this case-control study. The intestinal microbiota composition was investigated by quantitative real-time polymerase chain reaction (qPCR) method targeting bacterial 16S rRNA gene. Comparison between three groups was done using one-way analysis of variance. Results The participants’ mean age in the type 1 diabetes, type 2 diabetes and control groups was 35.4, 57.2 and
AimThe aim of the present study was to evaluate the in vitro antimicrobial and antibiofilm activity of chitosan nanoparticles (CS NPs) incorporated with mesenchymal stem cells-derived conditioned media (MSCs CM) on MDR Vibrio cholerae strains.Materials and MethodsChitosan NPs were prepared and characterized by dynamic light scattering (DLS), scanning electron microscope (SEM) and zeta potential measurement. MSCs CM were prepared and entrapped into MSCs CM-CS NPs composite and its release efficiency was measured. Antibacterial efficacy of nano structures was determined by disk diffusion and broth microdilution methods. Antibiofilm activity was assessed by crystal violet assay.ResultsBM-MSCs were characterized to be negative for CD34 and CD45
IntroductionEscherichia coli is the primary pathogen in complicated and uncomplicated urinary tract infections (UTIs). Today, the emergence of E. coli strains resistant to carbapenem antibiotics is a significant concern in UTIs treatment. The main carbapenemase enzymes in the E. coli are bla OXA-48, bla KPC, bla NDM, and to a less extent bla VIM and bla IMP. The aim of this study was the molecular screening of carbapenemase genes in Uropathogenic Escherichia coli (UPEC) isolated from the community- and hospital-associated UTIs.Material and methodsA total of 300 E. coli isolates were collected from outpatient and admitted patients in Tehran. The presence of bla OXA-48, bla KPC, bla NDM, bla VIM and bla IMP genes was detected by the PCR metho
The molecular mechanism underlying the development of vancomycin-intermediate Staphylococcus aureus (VISA) remains unclear. The abuses of antibacterial compounds lead to a change in the bacterial susceptibility patterns. Therefore, we examined the effect of Chlorhexidine (CHX) on in vitro development of VISA and reported CHX-selected VISA mutant Tm1 with phenotypic features similar to the clinical VISA isolates. WalKR, VraTSR, and GraSR are the most common regulatory systems involved in VISA evaluation. The expression of these systems, as well as walKR-regulated autolysins and VraTSR-regulated cell wall stimulon, were compared, by RT-qPCR, between the mutant and parental strains. The results revealed the downregulation of walKR, vraTSR, atl
Vancomycin-intermediate resistant Staphylococcus aureus (VISA), one of the common causes of nosocomial infection, is developed by mutations, including in walKR, with unclear molecular mechanisms. Although studies have veri ed some of these mutations, there are a few studies to pay attention to the importance of molecular modeling of mutations. Here, the Sanger sequencing for comparing gene sequences of WlKR between a VISA and its parental strain revealed mutation WalK-H364R. Structural protein mapping showed that H364R was located in a functional zinc ion coordinating residue within the cytoplasmic Per-Arnt-Sim (PAS) domain. The structural and functional effects of this mutation were analyzed using molecular computational approaches based o
Background: A rise in multidrug-resistant tuberculosis (MDR-TB), which is defined as the resistance to the two most effective first-line therapeutic drugs, Isoniazid (INH) and Rifampin (RIF), threatens global public health worldwide. Resistance of Mycobacterium tuberculosis to INH results from mutations in several genes most commonly in katG gene, and resistance to RIF is due to mutations in rpoB gene. Therefore, rapid diagnosis of MDR-TB is of high importance in controlling the disease progress and outcome. The accurate detection of the resistant TB strains can be accelerated by developing molecular tests. Objectives: The aim of the present local study was to isolate MDR-TB from the patients who were the residents in the west of Iran and e
The aim of this study was to evaluate the efficacy of selenium nanoparticle (an immune booster) and naloxone (an opioid receptor antagonist) as a new adjuvant in increasing immune responses against killed whole-cell Vibrio cholerae in a mouse cholera model. The Se NPs were synthesized and characterized by UV-visible, DLS, and zeta potential analysis. The SEM image confirmed the uniformity of spherical morphology of nanoparticle shape with 34 nm in size. The concentration of the Se NPs was calculated as 0.654 μg/ml in the ICP method. The cytotoxic activity of Se NPs on Caco-2 cells was assessed by the MTT assay and revealed 82.05% viability of cells after 24 h exposure with 100 μg/ml of Se NPs. Female BALB/C mice were orally immuni
Methods: To conduct the study, 215 isolates of Staphylococcus aureus were collected from clinical specimens. All strains were identified by standard methods. Afterward, the disk diffusion method was used to evaluate antibiotic resistance. The polymerase chain reaction method was performed to detect mecA, tsst1, and pvl genes and agr specific groups.Results: The highest resistance was observed to tetracycline (49.3%). It was also found out that all strains were susceptible to vancomycin. The prevalence of mecA, tsst1, and pvl genes in clinical isolates of Staphylococcus aureus was obtained as 46.04%, 32.3%, and 1.4%, respectively. Moreover, 57.20%, 14.41%, 16.74%, and 11.62% of clinical isolates had agr1, agr2, agr3, and agr4 group, respecti
Bacterial adhesins mediate the attachment and biofilm production leading to the persistence of colonized strains. The aim of this study was evaluation of the association of surface adhesin genes with the biofilm formation among Klebsiella oxytoca isolates. Among 50 isolates of K.?oxytoca from patients with antibiotic-associated diarrhoea, the susceptibility test, MIC (according to CLSI 2016) and phenotypic biofilm formation (with microtitre tissue-plate assay) were performed. The presence of adhesins was investigated using PCR. Thirty-three (66%) isolates produced moderate-level biofilms, but none of them exhibited strong biofilm formation. The presence of adhesins was as follows: fimA, 60% (n?=?30), mrkA, 42% (n?=?21), matB, 96% (n?=?48) a
The discovery of Helicobacter pylori in 1983 challenged researchers around the world to identify this pathogen's major virulence factors. The main rationale for this kind of research was to identify a biomarker associated with specific diseases following H. pylori colonization. Among different investigated virulence factors, duodenal ulcer promoting gene A (dupA) has been found to be associated with duodenal ulcer (DU), but its effect was different in various geographical regions. To determine the prevalence of dupA, we applied both classic primer pairs and our newly developed primers producing a highly conserved segment in PCR method. In our survey, 143 (47%) H. pylori isolates were obtained from 304H. pylori-colonized individuals [age ran
The emergence of CTX-M-1 producing Uropathogenic Escherichia coli (UPEC) has become a serious challenge. In addition to antimicrobial resistance, a number of virulence factors have been shown. Therefore, this study was designed to determine the prevalence of O- serogroups, phylogenetic groups, exotoxin genes, and antimicrobial resistance properties of CTX-M-1- producing UPEC. A total of 248 UPEC isolates were collected. The antibiotic resistance was performed, and PCR was used to detect the blaCTX-M1, exotoxins, serogroups and phylogroups of UPEC. Of 248 isolates, 95 (38.3%) harbored blaCTX-M-1. Of them, serogroups O1 and O25 were predominant, accounting for 20% and 13.7%, respectively. The hlyA was the dominant exotoxin gene (32.6%), follo
Biofilm formation and resistance to last-line antibiotics have restricted chemotherapy options toward infection eradication. Fifty K. oxytoca isolates were collected from patients with antibiotic-associated haemorrhagic colitis (AAHC). Antibiotic susceptibility tests were conducted and phenotypic biofilm formation was assessed using microtitre tissue plate (MTP) assay. PCR was employed to amplify the adhesins, extended-spectrum β-lactamases (ESBLs), carbapenemase and colistin resistance genes. The expression of adhesin genes was evaluated using quantitative real-time PCR (RT-qPCR). Results/Key findings. The previous antibiotic consumption and hospitalization (P< 0.05) and older ages (P= 0.0033) were significantly associated with AAHC. None
Author: Tavakoli M, Journal: Microbial pathogenesis[2019/04].
Pathogenic and drug‐resistant strains of Escherichia coli (E. coli) O25b‐B2‐ST131, O15:H1‐D‐ST393, and CGA (clonal group A) clonal groups have spread worldwide. This study aimed at determining E. coli epidemic clonal groups, their virulence factors, biofilm formation, neutrophils apoptosis, and antimicrobial resistance pattern of uropathogenic E. coli. A total of 95 CTX‐M‐1‐producing E. coli clinical isolates were enrolled. E. coli O25b‐B2‐ST131, CGA, and O15:K52:H1 were identified by serotyping and phylogrouping and allele‐specific polymerase chain reaction‐based assay. Antibiotic susceptibility, biofilm formation, hemolysis, and human serum bactericidal assay were performed. Neutrophil apoptosis was assayed by
The aim of this study was to determine the clonal correlation of Campylobacter strains isolated from diarrheal children under 5 years of age in Iran using the PFGE method and to determine the antimicrobial susceptibility and virulence gene content of strains. Of 750 patients with bacterial diarrhea, 33 (4%) Campylobacter spp., including 31 C. jejuni (94%) and 2 C. coli (6%), were isolated during 18-month period in Tehran, Iran. Except for one strain, remaining Campylobacter strains were positive for the flaA gene. A complete set of cytolethal distending toxin (CDT) encoding genes (cdtABC) were detected in 52% of the C. jejuni strains, while the 2 C. coli isolates under study only harbored cdtA and cdtB of the CDT cluster. All strains were r
Urinary tract infections (UTIs) currently rank among the most prevalent infectious diseases worldwide, with chronic and recurrent infections being especially problematic. Uropathogenic E. coli (UPEC), which is a causative agent in most cases of UTIs, expresses a multitude of virulence factors. Some virulence factors and specific genes were examined by PCR method. Genetic diversity was evaluated by phylogenetic typing groups. To know the genetic linkages among various E. coli, we evaluated clonal relatedness among different sources of E. coli isolates in Iranian children with UTI and age-matched healthy people by PFGE. Some pathogenicity determinants were more prevalent in urinary strains rather than fecal E. coli strains, significantly. The
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