Metagenomic investigation of bacteria associated with dental lesions : a cross-sectional study

Dental caries is considered as one of the most significant global health problem over the world. Dental caries initiates from bacterial shifts within the supragingival biofilm, then a polymicrobial biofilm is formed on the surface of tooth, and finally various bacterial species aggregate in a complex-organized manner. The exploiting variability in 16S rRNA gene sequence has been considered as a cost-efficient high-throughput characterization approach in human oral microbiome investigations. The aim of this study is to characterize bacterial species associated with superficial dental biofilm, underlying carious dentine and root caries lesion by16S rRNA gene-based metagenomic analysis. Herein, the bacterial communities in carious dentin lesion, biofilm and root canal samples of 30 subjects (aged 4?76 years) admitted to a clinic in Tehran during 2017 were investigated using a culture independent approach. Total genomic DNA of each tissue was subjected to metagenomic identification of bacteria using a nested PCR assay and 16S rRNA library construction method. 31 samples collected from 30 consenting patients (29 samples from 29 patients ant two biofilm samples from one patient). Bioinformatics analyses of a-800bp sequences of the second step of Nested-PCR revealed presence of 156 bacterial isolates in carious (n=45), biofilm (n=81) and root canal (n=30) specimens. Prevotella spp., Lactobacillus vaginalis, and streptococcus spp. showed higher prevalence in carious dentin, root and biofilm samples, respectively. Exploring the dental microbiota and comparing them in health or diseased conditions is critical step in the determination of human general health. The method applied in this study could identify bacteria related to the three dental lesions. However, due to lack of data for comparison in Genbank or because of the sequence similarity lower than 98% for most identified bacteria, the use of more powerful approaches like NGS platforms or typing of multiple loci (MLST) in future studies is recommended

Cone-Beam Computed Tomography for Evaluation of Apical Transportation in Root Canals Prepared by Two Rotary Systems

Introduction: Due to the importance of apical transportation during root canal preparation, the aim of the current study was to use cone-beam computed tomography (CBCT) to assess the extent of apical transportation caused by ProTaper and Mtwo files. Methods and Materials: Forty extracted maxillary first molars with 19-22 mm length and 20-40 degrees of curvature were selected. The mesiobuccal canals were prepared using either Mtwo or ProTaper rotary files (n=20). CBCT images were obtained before and after canal preparation to compare the apical transportation in different cross-sections of mesial and distal surfaces. The apical transportation values were analyzed using the SPSS software. The results were compared with student’s t-test and Mann-Whitney U test. Results: There was no significant difference in the extent of apical transportation between Mtwo and ProTaper systems in different canal cross-sections. The apical transportation value was less than 0.1 mm in most of the specimens, which was clinically acceptable. Conclusion: Considering the insignificant difference between the two systems, it can be concluded that both system have low rates of apical transportation and can be assuredly used in clinical settings

Erratum to: Nanoparticles Impact the Expression of the Genes Involved in Biofilm Formation in S. aureus, a Model Antimicrobial-Resistant Species

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Biofilm formation in clinical isolates of nosocomial Acinetobacter baumannii and its relationship with multidrug resistance

AbstractObjectiveTo check biofilm formation by Acinetobacter baumannii (A. baumannii) clinical isolates and show their susceptibility to different antibiotics and investigate a possible link between establishment of biofilm and multidrug resistance.MethodsThis study was performed on clinical samples collected from patients with nosocomial infections in three hospitals of Tehran. Samples were initially screened by culture and biochemical tests for the presence of different species of Acinetobacter. Identifications were further confirmed by PCR assays. Their susceptibilities to 11 antibiotics of different classes were determined by disc diffusion method according to Clinical and Laboratory Standards Institute guidelines. The ability to produce biofilm was investigated using methods: culture on Congo red agar, microtiter plate, and test tube method.ResultsFrom the overall clinical samples, 156 specimens were confirmed to contain A. baumannii. The bacteria were highly resistant to most antibiotics except polymyxin B. Of these isolates, 10.26% were able to produce biofilms as shown on Congo red agar. However, the percentage of bacteria with positive biofilm in test tube, standard microtiter plate, and modified microtiter plate assays were 48.72%, 66.66%, and 73.72%, respectively. At least 92% of the biofilm forming isolates were multidrug resistant.ConclusionsSince most of the multidrug resistant strains produce biofilm, it seems necessary to provide continuous monitoring and determination of antibiotic susceptibility of clinical A. baumannii. This would help to select the most appropriate antibiotic for treatment

Integron-associated Antibiotic Resistance in Clinical Isolates of Klebsiella from Karaj

Background and Aim: In recent years, Multidrug resistance has been increasing among Klebsiella isolates. The aim of this study was to survey existence of integrons and its relation with antibiotic resistance among clinical isolates of Klebsiella. Materials and Methods: From Jun 2015 to May 2016, 129 Klebsiella isolates collected from Karaj hospitals and laboratories. Statistical population included 80.6% female and 19.4% male. Antimicrobial susceptibility was performed using Kirby-Bauer disk diffusion and ESBLs producer were screened. Integrons were detected using PCR. Ethical Considerations: This study with research ethics code IR.IAU.K.REC.1396.16 has been approved by research ethics committee at Islamic Azad University of Karaj, Iran. Findings: The highest and lowest percentage of sensivity were found to ofloxacin (89.1%) and amoxcicillin (6.2%), respectively. 82.9% of isolates were resistant to more than two antibiotics from different classes. Among 129 isolates, 19.3% of the isolates harbour integrons. Frequencies of MDR among integron-positive isolates were 100%. Also, 71.3% and 28.7% of isolates were ESBLs positive and negative respectively. Conclusion: Results showed integron elements were prevalent among MDR isolates. Integron-associated resistance genes can be served as reservoirs of multi drug resistance within clinical isolates and presence of integron can be used as a marker to identify MDR isolates. Prevalence of ESBLs among clinical isolates of Klebsiella showed that antibiotics like ampicillin or amoxicillin-clavulanic acid are not effecvtive anymore in treatment of UTIs

A CBCT Assessment of Apical Transportation in Root Canals Prepared with Hand K-Flexofile and K3 Rotary Instruments

Introduction: Apical transportation changes the physical shape and physiologic environment of the root canal terminus. The aim of the present experimental study was to determine the extent of apical transportation after instrumentation with hand K-Flexofile and K3 rotary instruments by means of cone-beam computed tomography (CBCT). Methods and Materials: Forty mesiobuccal root canals of maxillary first molars, with 19-22 mm length and 20-40° canal curvature, were selected and assigned into two preparation groups. The first group was prepared with K-Flexofile with passive step-back technique and the second group was prepared with K3 rotary instruments. Pre and post instrumentation CBCT images were taken under similar conditions. The amount of root canal transportation was evaluated by Mann-Whitney U test and the chi-square test was used for the qualitative evaluation. Results: The amounts of apical canal transportation with the K3 and K-Flexofile instruments were 0.105±0.088 and 0.150±0.127 mm, respectively with no statistically significant differences. In the manual technique, 25% of the canals had no apical transportation; while 30% of the canals in the K3 group were transportation free. Conclusion: Both systems were able to preserve the initial curvature of the canals and both had sufficient accuracy. Preparation with K3 rotary instruments resulted in apical transportation similar to that of K-Flexofile

Comparing the Coronal Flaring Efficacy of Five Different Instruments Using Cone-Beam Computed Tomography

Introduction: Fearless removal of tooth structure during canal preparation and shaping has negative effects on the prognosis of treatment. On the other hand, sufficient pre-enlargement facilitates exact measurement of the apical size. The present in vitro study aimed to compare the efficacy of Gates-Glidden drills, K3, ProTaper, FlexMaster and RaCe instruments in dentin removal during coronal flaring using cone-beam computed tomography (CBCT). Methods and Materials: A total of 40 mandibular molars were selected and the coronal areas of their mesiobuccal and mesiolingual root canals were randomly prepared with either mentioned instruments. Pre- and post-instrumentation CBCT images were taken and the thickness of canal walls was measured in 1.5- and 3-mm distances from the furcation area. Data were analyzed using the one-way ANOVA. Tukey’s post hoc tests were used for two-by-two comparisons. Results: At 1.5-mm distance, there was no significant difference between different instruments. However, at 3-mm distances, Gates-Glidden drills removed significantly more dentin compared to FlexMaster files (mean=0.18 mm) (P<0.02); however, two-by-two comparisons did not reveal any significant differences between the other groups. Conclusion: All tested instruments can be effectively used in clinical settings for coronal pre-enlargement.Keywords: Cone-Beam Computed Tomography; Coronal Flaring; Coronal Pre-Enlargement; Root Canal Treatment; Root Canal Preparatio

Nanoparticles Impact the Expression of the Genes Involved in Biofilm Formation in S. aureus, a Model Antimicrobial-Resistant Species

Background:     Infection with resistant bacteria are still reported in hospitals despite the routine cleaning of hospital surfaces. Presence of drug-resistant microbes in the on environment of hospitals and on medical equipment is indicative of the need for control measures which could impact the emergence of such microbes. In addition, biofilms are increasingly associated with human infections and it necessitates careful considerations on usage of a diverse range of medical devices, such as catheters, implants and pacemakers in hospitals.  Methods:      This study was designed to compare the effect of silver, ZnO nanoparticles and curcumin on drug-resistant Gram-positive and Gram-negative bacteria which were already isolated from different wards of the hospital. The MIC value were determined for silver, curcumin and ZnO nanoparticles. As the second step, the expression level of the genes involved in biofilm formation in S. aureus, including icaA, icaD, fnbA and fnbB, was studied to analyze the physiological reaction to controlled concentrations of such nanoparticles using RT-qPCR assessments. Results:     In this study, a total of 172 bacterial isolates were recovered from clinical and environmental samples (96 and 76 isolates, respectively). API-20 test revealed that these isolates belonged to 8 species. All antimicrobial resistant isolates were susceptible to the metal oxide nanoparticles. The results of q-PCR in this study showed that the expression of icaA and icaD genes in the presence of silver, curcumin and zinc nanoparticles were not significantly reduced compared to the control samples. But, exposure to nanoparticles reduced the expression of fnbA and fnbB genes from 0.46 to 0.06. Conclusion:  The results of our study showed that nanoparticles are highly effective on antibiotics- resistant isolates and these compounds can be used in the treatment of resistant bacteria. In addition, this study also demonstrates the promising potential of using nanoparticles as anti-biofilm formation agents

Evaluation of Apical Transportation in Root Canals Prepared with Hand File and Two Rotary Files by Cone Beam Computed Tom ography

The purpose of the mechanical cleaning of the root canal is to create a conical shape for 3D filling of the canal area. Excessive dentin removal from one side of the canal, as compared to other parts located at an equal distance to the longitudinal axis of the tooth, causes an error called the canal transportation. In this study, the canal transportation was evaluated by hand K-flexo file Mtwo and,Dia-pt rotary file using Cone Beam Computed Tomography (CBCT). This is an Ex-vivo study conducted on 60 extracted first molars. Root curvature was measured by Schneider's method. Preparation was performed in three groups of 20 with manual and Mtwo and Dia-pt files. CBCT images were prepared before and after clearing the canals. Data were analyzed using SPSS 18 Software. Based on the results of the kruskal wallis test, there are differences between the three files in the 2 and 3 mm sections (respectively (p = 0.01) (p = 0.01)). However, there is no difference in the cross-section of 2.5 mm based on kruskal wallis test (p = 0.16). The results of this study indicate that the channel displacement in the Mtwo system is the least. And this system is better than K-Flexo file and Dia-pt in following the shape of the canal and creating a conical canal with the least deviation from the channel

Detection of tetracycline resistance genes, aminoglycoside modifying enzymes, and coagulase gene typing of clinical isolates of Staphylococcus aureus in the Southwest of Iran

Objective(s): The aim of the present study was to determine the aminoglycoside modifying enzymes (AMEs) encoded genes, tetracycline resistance genes, and the coa based typing of Staphylococcus aureus isolates in the Southwest of Iran. Materials and Methods: Antimicrobial susceptibility of isolates was carried out by agar disk diffusion methods. Two sets of multiplex PCR mixture were used for detection of AME genes and tet genes.  All of the isolates were typed with the coagulase gene typing method. Of the 121 isolates, 29.75% and 47.93% were resistant to at least one aminoglycosides and tetracyclines, respectively. Results: The aac(6')-Ie-aph(2'') was the most frequent gene (97.22%), and aph (3')-IIIa and ant (4')-Ia genes were detected in 61.11% and 11.11% of aminoglycoside resistant isolates, respectively. The tetK and tetM genes were detected in 82.75% and 56.9% of tetracycline resistant isolates, respectively. Overall 31.4% of isolates were MRSA. Totally 17 distinct coa gene RFLP patterns, numbered C1 to C17, were observed.  The C5 was the most frequent coa type with 31 isolates. Conclusion: The aac(6')-Ie-aph(2'') and aph (3')-IIIa genes were the most important genes contributing to aminoglycosides resistance, while resistance to tetracyclines was mediated by tetK and tetM genes. Interestingly all S. aureus with C5 as the most prevalent coa-type were resistant to at least one of the aminoglycoside antibiotics and tetracycline simultaneously. Moreover, 30 out of 31 isolates with this coa type were MRSA, indicating the importance of the C5 coa-type in MRSA strains and also in isolates that were resistant to aminoglycosides and tetracycline