Molecular epidemiological analyses of Clostridioides difficile isolates in a university hospital in Japan

Background

We performed molecular epidemiological analyses of Clostridioides difficile isolates in a university hospital in Japan to reveal the risk of C. difficile infection.

Methods

Cultured isolates from 919 stool samples from 869 patients obtained from July 2015 to August 2016 were subjected to toxin gene detection, ribotyping, multilocus sequence typing, antimicrobial susceptibility testing, and quantitative real-time polymerase chain reaction testing for C. difficile toxin gene expression.

Results

Of the 919 stool samples from 869 patients, C. difficile was isolated from 153 samples (16.6%), of which 49 (32%) and 104 (68%) were from patients with and without C. difficile infection, respectively. Analyses showed genetic diversity, with ST8 and ST17 strains of healthcare-associated infections, some of which caused C. difficile infections. There was no significant difference in the transcription levels of C. difficile toxin genes between isolates from patients with and without C. difficile infection.

Conclusions

Major Japanese clonal strains, ST8 and ST17, have been in the hospital environment for a long time and cause healthcare-associated C. difficile infections. The C. difficile toxin genes were transcribed in the isolates from both patients with and without C. difficile infection but were no significant relationship with the development of C. difficile infection.

Enterococcal Linear Plasmids Adapt to Enterococcus faecium and Spread within Multidrug-Resistant Clades

Antimicrobial resistance (AMR) of bacterial pathogens, including enterococci, is a global concern, and plasmids are crucial for spreading and maintaining AMR genes. Plasmids with linear topology were identified recently in clinical multidrug-resistant enterococci. The enterococcal linear-form plasmids, such as pELF1, confer resistance to clinically important antimicrobials, including vancomycin; however, little information exists about their epidemiological and physiological effects. In this study, we identified several lineages of enterococcal linear plasmids that are structurally conserved and occur globally. pELF1-like linear plasmids show plasticity in acquiring and maintaining AMR genes, often via transposition with the mobile genetic element IS1216E. This linear plasmid family has several characteristics enabling long-term persistence in the bacterial population, including high horizontal self-transmissibility, low-level transcription of plasmid-carried genes, and a moderate effect on the Enterococcus faecium genome alleviating fitness cost and promoting vertical inheritance. Combining all of these factors, the linear plasmid is an important factor in the spread and maintenance of AMR genes among enterococci.

Elucidation of host diversity of the VanD-carrying genomic islands in enterococci and anaerobes

Background

VanD is a rare type of vancomycin resistance worldwide. However, the host diversity of the vanD gene cluster and the structural similarity of their genomic islands are not well understood.

Methods

Three VanD-type Enterococcus faecium strains (AA620, AA622 and AA624) isolated from a Japanese patient who underwent vancomycin treatment in 2017 were analysed. This study utilized WGS analysis to characterize the three VanD-type E. faecium strains and describes the diversity of hosts possessing VanD-carrying genomic islands.

Results

The three isolates exhibited variable MICs of vancomycin. In the relatively vancomycin-resistant AA620, mutations were identified in vanS_D and ddl. The strains AA622 and AA624 had intact ddl and harboured two vanD gene clusters. qRT-PCR results revealed the ddl mutation to be a factor affecting the high vancomycin resistance range of AA620. WGS data showed the 155 kb and 185 kb genomic islands harbouring the vanD gene cluster inserted in the coding region of the lysS gene, located in the chromosome in AA620 and AA622/624, respectively. Comparing the VanD-carrying genomic islands to available sequences of other enterococci and enteric anaerobes revealed how the genomic islands of these organisms isolated worldwide shared similar core genes and backbones. These anaerobes belonged to various genera within the order Eubacteriales. The phylogenetic cluster of the genomic island core genome alignment did not correlate with the host-species lineage, indicating horizontal gene transfer in the gut microbiota.

Conclusions

By horizontal gene transfer, various bacteria forming the gut microbiota maintain VanD-carrying genomic islands.

Isolation of Serratia fonticola Producing FONA, a Minor Extended-Spectrum β-Lactamase (ESBL), from Imported Chicken Meat in Japan

Five novel strains of Serratia fonticola that produce FONA, a minor extended-spectrum beta-lactamase (ESBL), were isolated during routine surveillance of ESBL-producing Enterobacteriaceae in imported chicken meat in Japan in 2017 and 2018. These strains exhibited a clear ESBL phenotype in susceptibility tests carried out in the presence of clavulanic acid; however, all strains tested negative in a multiplex polymerase chain reaction assay used to detect TEM, SHV, and CTX-M β-lactamase genes. After identification of the bacterial species as S. fonticola, full length bla_FONA genes were amplified and the DNA sequences were determined. The bla_FONA genes from all 5 strains were different from those previously reported (bla_FONA-1 to bla_FONA-6); they clustered close to one another but were distinct from previously reported bla_FONA genes in a phylogenic analysis based on amino acid sequences.

Isolation of thymidine-dependent and extended-spectrum-β-lactamase-producing Escherichia coli small-colony variant from urine of a septuagenarian female patient with recurrent cystitis: A case report with genetic investigation

Thymidine-dependent small-colony variant (TD-SCV) of Escherichia coli was isolated from urine of a septuagenarian female patient on hemodialysis suffering from recurrent cystitis. The patient had been treated with frequent administrations of trimethoprim sulfamethoxazole (SXT), every time her cystitis symptoms developed. In the TD-SCV isolate, the deletion was detected in the thyA gene associated with thymidylate synthase. Interestingly, the isolate was found to produce extended-spectrum β-lactamase (ESBL), and the experiment on conjugational transfer of the resistance trait was successful. By means of genetic analysis, the isolate was found to carry bla_{CTX-M-1 group}. To the best of our knowledge, this is the first report of urinary tract infection caused by the transmissible ESBL-producing TD-SCV of E. coli. MICs of the TD-SCV were obtained only on the Mueller Hinton agar media supplemented with appropriate concentrations of thymidine, which might lead to the difficulty for proper chemotherapy in daily medicine. Furthermore, transmission of the ESBL gene via plasmid should be of concern.

Novel Multidrug-Resistant Enterococcal Mobile Linear Plasmid pELF1 Encoding vanA and vanM Gene Clusters From a Japanese Vancomycin-Resistant Enterococci Isolate

Vancomycin-resistant enterococci are troublesome pathogens in clinical settings because of few treatment options. A VanA/VanM-type vancomycin-resistant Enterococcus faecium clinical isolate was identified in Japan. This strain, named AA708, harbored five plasmids, one of which migrated during agarose gel electrophoresis without S1 nuclease treatment, which is indicative of a linear topology. We named this plasmid pELF1. Whole genome sequencing (WGS) analysis of the AA708 strain revealed that the complete sequence of pELF1 was 143,316 bp long and harbored both the vanA and vanM gene clusters. Furthermore, mfold analysis and WGS data show that the left end of pELF1 presumably forms a hairpin structure, unlike its right end. The pELF1 plasmid was not digested by lambda exonuclease, indicating that terminal proteins were bound to the 5′ end of the plasmid, similar to the Streptomyces linear plasmids. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis results were also consistent with the exonuclease assay results. In retardation assays, DNAs containing the right end of proteinase K-untreated pELF1 did not appear to move as well as the proteinase K-treated pELF1, suggesting that terminal proteins might be attached to the right end of pELF1. Palindromic sequences formed hairpin structures at the right terminal sequence of pELF1; however, sequence similarity with the well-known linear plasmids of Streptomyces spp. was not high. pELF1 was unique as it possessed two different terminal structures. Conjugation experiments revealed that pELF1 could be transferred to E. faecalis, E. faecium, E. casseliflavus, and E. hirae. These transconjugants exhibited not only high resistance levels to vancomycin, but also resistance to streptomycin, kanamycin, and erythromycin. These results indicate that pELF1 has the ability to confer multidrug resistance to Enterococcus spp. simultaneously, which might lead to clinical hazards.

Dissemination and genetic analysis of the stealthy vanB gene clusters of Enterococcus faecium clinical isolates in Japan

Background

VanB-type vancomycin (VAN) resistance gene clusters confer VAN resistances on Enterococcus spp. over a wide range of MIC levels (MIC = 4–1000 mg/L). However, the epidemiology and the molecular characteristics of the VAN susceptible VanB-type Enterococcus still remain unclear.

Results

We characterized 19 isolates of VanB-type Enterococcus faecium that might colonize in the gut and were not phenotypically resistant to VAN (MIC = 3 mg/L). They were obtained from two hospitals in Japan between 2009 and 2010. These isolates had the identical vanB gene cluster and showed same multilocus sequence typing (MLST) (ST78) and the highly related profiles in pulsed-field gel electrophoresis (PFGE). The vanB gene cluster was located on a plasmid, and was transferable to E. faecium and E. faecalis. Notably, from these VanB-type VREs, VAN resistant (MIC≥16 mg/L) mutants could appear at a frequency of 10^− 6–10^− 7/parent cell in vitro. Most of these revertants acquired mutations in the vanS_B gene, while the remainder of the revertants might have other mutations outside of the vanB gene cluster. All of the revertants we tested showed increases in the VAN-dependent expression of the vanB gene cluster, suggesting that the mutations affected the transcriptional activity and increased the VAN resistance. Targeted mutagenesis revealed that three unique nucleotide substitutions in the vanB gene cluster of these strains attenuated VAN resistance.

Conclusions

In summary, this study indicated that stealthy VanB-type E. faecium strains that have the potential ability to become resistance to VAN could exist in clinical settings.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1342-1) contains supplementary material, which is available to authorized users.

First case report of bacteremia caused by Dysgonomonas mossii

We here report a case of Dysgonomonas mossii bacteremia with cholangitis. An 85-year-old male patient with recurrent hepatitis B surface antigen-negative/anti-hepatitis C virus-negative hepatocellular carcinoma came to our hospital in poor physical condition. Two sets of blood cultures revealed a positive result for D. mossii. As matrix-assisted laser desorption/ionization time-of-flight mass spectrometry failed to identify D. mossii, analysis of 16S rRNA gene sequencing was performed; however, this gene is not specific enough to distinguish between D. mossii and D. oryzarvi. Finally, D. mossii infection was confirmed by gyrB and recA sequencing. To our knowledge, this is the first report of D. mossii causing human infection, which was identified in culture and confirmed using a combination of 16S rRNA, gyrB, and recA sequencing.

Oxygen Limitation Enhances the Antimicrobial Activity of Fosfomycin in Pseudomonas aeruginosa Following Overexpression of glpT Which Encodes Glycerol-3-Phosphate/Fosfomycin Symporter

Fosfomycin is resurfacing as a "last resort drug" to treat infections caused by multidrug resistant pathogens. This drug has a remarkable benefit in that its activity increases under oxygen-limited conditions unlike other commonly used antimicrobials such as β-lactams, fluoroquinolones and aminoglycosides. Especially, utility of fosfomycin has being evaluated with particular interest to treat chronic biofilm infections caused by Pseudomonas aeruginosa because it often encounters anaerobic situations. Here, we showed that P. aeruginosa PAO1, commonly used in many laboratories, becomes more susceptible to fosfomycin when grown anaerobically, and studied on how fosfomycin increases its activity under anaerobic conditions. Results of transport assay and gene expression study indicated that PAO1 cells grown anaerobically exhibit a higher expression of glpT encoding a glycerol-3-phosphate transporter which is responsible for fosfomycin uptake, then lead to increased intracellular accumulation of the drug. Elevated expression of glpT in anaerobic cultures depended on ANR, a transcriptional regulator that is activated under anaerobic conditions. Purified ANR protein bound to the DNA fragment from glpT region upstream, suggesting it is an activator of glpT gene expression. We found that increased susceptibility to fosfomycin was also observed in a clinical isolate which has a promoted biofilm phenotype and its glpT and anr genes are highly conserved with those of PAO1. We conclude that increased antibacterial activity of fosfomycin to P. aeruginosa under anaerobic conditions is attributed to elevated expression of GlpT following activation of ANR, then leads to increased uptake of the drug.

Membrane-active antimicrobial poly(amino-modified alkyl) β-cyclodextrins synthesized via click reactions

The emergence of drug-resistant bacteria has led to the high demand for new antibiotics. In this report, we investigated membrane-active antimicrobial β-cyclodextrins. These contain seven amino-modified alkyl groups on a molecule, which act as functional moieties to permeabilize bacterial cell membranes. The polyfunctionalization of cyclodextrins was achieved through a click reaction assisted by microwave irradiation. A survey using derivatives with systematically varied functionalities clarified the unique correlation of the antimicrobial activity of these compounds with their molecular structure and hydrophobicity/hydrophilicity balances. The optimum hydrophobicity for the compounds being membrane-active was specific to bacterial strains and animal cells; this led to specific compounds having selective toxicity against bacteria including multidrug-resistant pathogens. The results demonstrate that cyclodextrin is a versatile molecular scaffold for rationally designed structures and can be used for the development of new antibiotics.

Genetic shifts in methicillin-resistant Staphylococcus aureus epidemic clones and toxin gene profiles in Japan: comparative analysis among pre-epidemic, epidemic and post-epidemic phases

PURPOSE

The decline in methicillin-resistant Staphylococcus aureus (MRSA) isolation rates has become a general observation worldwide, including Japan. We hypothesized that some genetic shift in MRSA might cause this phenomenon, and therefore we investigated the genetic profiles among MRSA clinical isolates obtained from three different epidemic phases in Japan.

METHODOLOGY

A total of 353 MRSA isolates were selected from 202 medical facilities in 1990 (pre-epidemic phase), 2004 (epidemic phase) and 2016 (post-epidemic phase). Molecular typing was performed by PCR detection of 22 genes using the polymerase chain reaction (PCR)-based ORF typing (POT) system, including an additional eight genes including small genomic islets and seven toxin genes.

RESULTS

Isolates with a POT1 of score 93, identified as presumed clonal complex (pCC)5-staphylococcal cassette chromosome mec (SCCmec) type II including ST5-SCCmec type II New York/Japan clone, represented the major epidemic MRSA lineage in 1990 and 2004. In 2016, however, a marked decrease in isolates with a POT1 score of 93, along with changes in the epidemiology of toxin genes carried, was noted, where the carriers of tst genes including the tst-sec combination were markedly reduced, and those possessing the seb gene alone were markedly increased. Rather, isolates with a POT1 score of 106, including pCC1 or pCC8 among the isolates with SCCmec type IV, which often links to community-associated MRSA, were predominant. Interestingly, the pCC1 and pCC8 lineages were related to sea and tst-sec carriage, respectively.

CONCLUSIONS

Over time, a transition in MRSA genetic profiles from a POT1 score of 93 in 1990 and 2004 to 106 in 2014 was found in Japan.

New colony multiplex PCR assays for the detection and discrimination of vancomycin-resistant enterococcal species

New colony multiplex PCR assays for detection of seven types of vancomycin-resistance determinants and eight types of Enterococcus species were developed. For 135 enterococcal isolates examined in this study, these assays showed high sensitivity and specificity, and could provide the rapid and accurate detection of vancomycin-resistant determinants and Enterococcus spp.

Tongue-palatal contact changes in patients with skeletal mandibular prognathism after sagittal split ramus osteotomy: an electropalatography study

The purpose of this study was to investigate the changes in tongue-palatal contact patterns using electropalatography (EPG) before and after sagittal split ramus osteotomy (SSRO) in patients with mandibular prognathism. Nine clients who underwent SSRO for mandibular setback and seven control subjects were participated in this study. Tongue-palatal contact patterns for /t/, /s/ and /k/ production were investigated using EPG before surgery and 3 months after surgery. The mean value of whole total of palate contact (WT) in the maximum contact frame was examined before and after SSRO. The correlation quantity between the change of center of gravity (COG) value and the amount of mandibular setback was also evaluated. The mean value of WT for /t/ and /s/ significantly increased after SSRO, and the EPG pattern became normal. However, a remarkable change in WT for /k/ was not observed, and the mean value was significantly larger in the SSRO group before and after surgery than in the control group. A negative correlation between COG variation and the amount of mandibular setback for /t/ and positive correlation for /s/ was observed. This study demonstrated that tongue-palatal contact patterns for /t/ and /s/ articulation improved clearly after SSRO. There was a significant correlation between COG variation and the amount of mandibular setback. However, no significant change was detected through perceptual assessment before and after SSRO. Further investigation is needed to determine whether these results will change over time.

Cooperative Actions of CRP-cAMP and FNR Increase the Fosfomycin Susceptibility of Enterohaemorrhagic Escherichia coli (EHEC) by Elevating the Expression of glpT and uhpT under Anaerobic Conditions

Bacterial infections to anaerobic site are often hard to be treated because the activity of most of antimicrobials decreases under anaerobic conditions. However, fosfomycin rather provides a greater activity under anaerobic conditions than aerobic conditions. Previously, we found that expression of glpT and uhpT, fosfomycin symporters in enterohaemorrhagic Escherichia coli (EHEC) was upregulated by FNR, a global regulator during the anaerobiosis of the bacterium, which led to increased uptake and susceptibility to this drug. In this study, we showed that expression of glpT and uhpT is induced by CRP-cAMP, the regulator complex under both aerobic and anaerobic conditions. The activity of CRP-cAMP in EHEC was elevated under anaerobic conditions because levels of both CRP and cAMP were higher in the cells when grown anaerobically than those when grown aerobically. Results of expression study using mutants indicated that CRP-cAMP is indispensable for expression of glpT but not uhpT—whereas that of uhpT requires UhpA that is the response regulator composing of two-component system with the sensor kinase, UhpB. The CRP-cAMP protein bound to a region that overlaps RNA polymerase binding site for glpT and region upstream of UhpA binding site for uhpT. FNR bound to a region further upstream of CRP-cAMP binding site on region upstream of the glpT gene. These combined results suggested that increased antibacterial activity of fosfomycin to EHEC under anaerobic conditions is due to activation of FNR and increment of CRP-cAMP activity. Then, FNR enhances the expression of glpT activated by CRP-cAMP while CRP-cAMP and FNR cooperatively aids the action of UhpA to express uhpT to maximum level.

Detection of Vascular Disease Risk in Women by Panoramic Radiography

Low bone mineral density and rapid bone loss of the skeleton are associated with mortality risk from vascular diseases in post-menopausal women. Panoramic radiographic measurements are considered as indicators of skeletal bone mineral density or bone turnover. We hypothesize that such measurements may be associated with vascular disease risk in post-menopausal women. Associations of mandibular cortical shape and width on panoramic radiographs with skeletal bone mineral density and risk factors related to vascular diseases were investigated in 87 post-menopausal women. Cortical shape was associated with skeletal bone mineral density, low-density lipoprotein cholesterol, apolipoprotein B, resting heart rate, and endothelial dysfunction. Cortical width was associated with skeletal bone mineral density, low-density lipoprotein cholesterol, and apolipoprotein A1. Dentists may be able to refer women with increased risk of vascular diseases, as well as low bone mineral density, to medical professionals for further examination by panoramic findings.

Cyclic Mechanical Strain Regulates the PTHrP Expression in Cultured Chondrocytes via Activation of the Ca2+ Channel

The association between mechanical stimulation and chondrocyte homeostasis has been reported. However, the participation of PTHrP (parathyroid-hormone-related protein) in the mechano-regulation of chondrocyte metabolism remains unclear. We determined whether mechanical stimulation of chondrocytes induces the expression of PTHrP and, further, whether the mechano-modulation of PTHrP is dependent on the maturational status of chondrocytes. Cyclic mechanical strain was applied to rat growth plate chondrocytes at the proliferating, matrix-forming, and hypertrophic stages at 30 cycles/min. Cyclic mechanical strain significantly increased PTHrP mRNA levels in chondrocytes at the proliferating and matrix-forming stages only. The induction of PTHrP was dependent on loading magnitude at the proliferating stage. Using specific ion channel blockers, we determined that mechano-induction of PTHrP was inhibited by nifedipine, a Ca2+ channel blocker. These results suggest that mechanical induction of PTHrP possibly provides the environment for greater chondrocyte replication and matrix formation that would subsequently affect cartilage formation.

The transcribed-ultraconserved regions in prostate and gastric cancer: DNA hypermethylation and microRNA-associated regulation

The transcribed-ultraconserved regions (T-UCRs) are a novel class of non-coding RNAs, which are absolutely conserved (100%) between the orthologous regions of the human, rat and mouse genomes. Previous studies have described that several T-UCRs show differential expressions in cancers and might be involved in cancer development. We investigated the transcriptional levels of representative 26 T-UCRs and determined the regions that were differently expressed in prostate cancer (PCa) and gastric cancer (GC). A quantitative reverse transcription-polymerase chain reaction analysis revealed the downregulation of Uc.158+A expression by a DNA methylation-associated mechanism, which was restored by 5-Aza-dC (5-aza-2'-deoxycytidine) treatment. Bisulfite genomic sequencing using cell lines and tissue samples demonstrated cancer-specific CpG hypermethylation in both GC and PCa. However, Uc.416+A was only overexpressed in GC and we identified an miR-153 binding site in the possible regulatory region of Uc.416+A using online databases. Along with a forced expression or knockdown of miR-153 in MKN-74 GC cells, the transcriptional levels of Uc.416+A were significantly disturbed. A luciferase reporter gene assay supported the direct regulation of Uc.416+A expression by miR-153. Furthermore, Uc.416+A was associated with cell growth through the regulation of IGFBP6 (insulin-like growth factor-binding protein 6) in GC. These findings suggest an oncogenic role of Uc.416+A in GC, which suggests that our approach would provide new insights into functional studies of T-UCRs in cancer biology.

Variation in patient position and impact on carbon-ion scanning beam distribution during prostate treatment

OBJECTIVE

We assessed the impact of changes in patient position on carbon-ion scanning beam distribution during treatment for prostate cancer.

METHODS

68 patients were selected. Carbon-ion scanning dose was calculated. Two different planning target volumes (PTVs) were defined: PTV1 was the clinical target volume plus a set-up margin for the anterior/lateral sides and posterior side, while PTV2 was the same as PTV1 minus the posterior side. Total prescribed doses of 34.4 Gy [relative biological effectiveness (RBE)] and 17.2 Gy (RBE) were given to PTV1 and PTV2, respectively. To estimate the influence of geometric variations on dose distribution, the dose was recalculated on the rigidly shifted single planning CT based on two dimensional-three dimensional rigid registration of the orthogonal radiographs before and after treatment for the fraction of maximum positional changes.

RESULTS

Intrafractional patient positional change values averaged over all patients throughout the treatment course were less than the target registration error = 2.00 mm and angular error = 1.27°. However, these maximum positional errors did not occur in all 12 treatment fractions. Even though large positional changes occurred during irradiation in all treatment fractions, lowest dose encompassing 95% of the target (D95)-PTV1 was >98% of the prescribed dose.

CONCLUSION

Intrafractional patient positional changes occurred during treatment beam irradiation and degraded carbon-ion beam dose distribution. Our evaluation did not consider non-rigid deformations, however, dose distribution was still within clinically acceptable levels.

ADVANCES IN KNOWLEDGE

Inter- and intrafractional changes did not affect carbon-ion beam prostate treatment accuracy.

Cranial suture-like gap and bone regeneration after transplantation of cryopreserved MSCs by use of a programmed freezer with magnetic field in rats

Mesenchymal stem cells (MSCs) can be used for regeneration of various organs and tissues. A previous study revealed that cryopreserved MSCs, which were frozen by a programmed freezer with a magnetic field (Cells Alive System: CAS) and cryopreserved for 7 days in a -150°C deep freezer, can maintain high survival and proliferation rates while retaining both adipogenic and osteogenic differentiation abilities. The purpose of this study was to examine MSC viability and tissue regenerative ability after long-term cryopreservation using a CAS freezer. MSCs were isolated from rat femora bone marrow and cryopreserved in a -150°C deep freezer (CAS group) or directly cryopreserved in a deep freezer (Direct group). After 3 years, the cells were thawed and the number of viable cells was counted. Cell proliferation was also examined after 14 days in culture. For histological examination, forty 4-week-old Fischer 344 male rats received bone and sagittal suture defects with a diameter of 6.0mm, and MSCs (CAS or Direct group) cryopreserved for 1 year were grafted with membranes. Non-cryopreserved MSCs (Control group) were transplanted to an additional twenty rats. The rats were sacrificed at 4, 8, 16, and 24 weeks after surgery. The parietal bones, including the sagittal suture, were observed under a light microscope and the extent of bone regeneration was measured. Our results indicate that MSCs survival and proliferation rates were significantly higher in the CAS group than in the Direct group. In the Control and CAS groups, a large amount of new bone formation and a suture-like gap was identified 24 weeks after transplantation, whereas only a small amount of new bone formation was observed in the Direct group. These results suggest that the CAS freezer is amenable to long-term cryopreservation of MSCs, which can be applied to the regeneration of various tissues, including bone tissue with suture-like gap formation.

Effects of enzymatic degradation after loading in temporomandibular joint

Synovial fluid of the joint decreases friction between the cartilage surfaces and reduces cartilage wear during articulation. Characteristic changes of synovial fluid have been shown in patients with osteoarthritis (OA) in the temporomandibular joint (TMJ). OA is generally considered to be induced by excessive mechanical stress. However, whether the changes in synovial fluid precede the mechanical overloading or vice versa remains unclear. In the present study, our purpose was to examine if the breakdown of joint lubrication affects the frictional properties of mandibular condylar cartilage and leads to subsequent degenerative changes in TMJ. We measured the frictional coefficient in porcine TMJ by a pendulum device after digestion with hyaluronidase (HAase) or trypsin. Gene expressions of interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2), matrix metalloproteinases (MMPs), type II collagen, and histology were examined after prolonged cyclic loading by an active pendulum system. The results showed that the frictional coefficient increased significantly after HAase (35%) or trypsin (74%) treatment. Gene expression of IL-1β, COX-2, and MMPs-1, -3, and -9 increased significantly in enzyme-treated TMJs after cyclic loading. The increase in the trypsin-treated group was greater than that in the HAase-treated group. Type II collagen expression was reduced in both enzyme-treated groups. Histology revealed surface fibrillation and increased MMP-1 in the trypsin-treated group, as well as increased IL-1β in both enzyme-treated groups after cyclic loading. The findings demonstrated that the compromised lubrication in TMJ is associated with altered frictional properties and surface wear of condylar cartilage, accompanied by release of pro-inflammatory and matrix degradation mediators under mechanical loading.

Celecoxib exerts protective effects on extracellular matrix metabolism of mandibular condylar chondrocytes under excessive mechanical stress

OBJECTIVE

Excessive mechanical stress is considered a major cause of temporomandibular joint osteoarthritis (TMJ-OA). High magnitude cyclic tensile strain (CTS) up-regulates pro-inflammatory cytokines and matrix metalloproteinases (MMPs) in chondrocytes, while selective cyclooxygenase (COX)-2 inhibition has been shown to be beneficial to cytokine-induced cartilage damage. However, the effect of selective COX-2 inhibitors on mechanically stimulated chondrocytes remains unclear. This study evaluated the effect of celecoxib, a selective COX-2 inhibitor, on extracellular matrix (ECM) metabolism of mandibular condylar chondrocytes under CTS.

METHODS

Porcine mandibular chondrocytes were subjected to CTS of 0.5 Hz, 10% elongation with celecoxib for 24 h. The gene expressions of COX-2, MMPs, aggrecanase (ADAMTS), type II collagen and aggrecan were examined by real-time PCR. Also, prostaglandin E2 (PGE2) concentrations were determined using enzyme immunoassay kit. The levels of MMP and transcription factor NF-κB were measured by western blot while MMP activity was determined by casein zymography.

RESULTS

The presence of celecoxib normalized the release of PGE2 and diminished the CTS-induced COX-2, MMP-1, MMP-3, MMP-9 and ADAMTS-5 gene expressions while recovered the downregulated type II collagen and aggrecan gene expressions. Concurrently, celecoxib showed inhibition of NF-κB and suppression of MMP production and activity.

CONCLUSIONS

Celecoxib exerts protective effects on mandibular condylar chondrocytes under CTS stimulation by diminishing degradation and restoring synthesis of ECM.

A retrospective study of digital subtraction technique to detect sclerotic changes in alveolar bone on intraoral radiographs of bisphosphonate-treated patients

OBJECTIVES

Several reports have suggested that sclerotic changes in cancellous bone of the jaw and thickening of the lamina dura are characteristic radiographic changes of an early silent stage of bisphosphonate (BP)-related osteonecrosis of the jaw. No quantitative evaluation has been reported to support this hypothesis. Emago(®) software (Oral Diagnostic Systems, Amsterdam, Netherlands) can perform digital subtraction on intraoral radiographs even if they were obtained by non-standardized radiography, provided the dimensional error is within a certain limit. The purpose of this study was to evaluate whether sclerotic changes of alveolar bone or thickening of lamina dura in patients using BP can be detected using the subtraction function of Emago.

METHODS

The authors selected 46 pairs of intraoral radiographs of the mandibular molar area in dental patients. All radiographs were obtained at intervals of 6 months or more. Among the 46 pairs, 7 pairs were from patients who were being treated with BP (study subjects), and 39 pairs were from patients who had not been using BP (controls). All pairs of radiographs underwent digital subtraction by Emago. The number of pixels of the sclerotic areas was counted and compared between subjects and controls.

RESULTS

The sclerotic changes were significantly distinguishable in two of the seven subjects (28.6%) using BP.

CONCLUSIONS

Digital subtraction function of Emago was able to detect sclerotic changes in alveolar bone. Therefore, it is suggested that the subtraction function of Emago is a useful tool for quantitatively detecting sclerotic changes that are observed at an early, silent stage of BP-related osteonecrosis of the jaw.

A retrospective study of digital subtraction technique to detect sclerotic changes in alveolar bone on intraoral radiographs of bisphosphonate-treated patients

OBJECTIVES

Several reports have suggested that sclerotic changes in cancellous bone of the jaw and thickening of the lamina dura are characteristic radiographic changes of an early silent stage of bisphosphonate (BP)-related osteonecrosis of the jaw. No quantitative evaluation has been reported to support this hypothesis. Emago® software (Oral Diagnostic Systems, Amsterdam, Netherlands) can perform digital subtraction on intraoral radiographs even if they were obtained by non-standardized radiography, provided the dimensional error is within a certain limit. The purpose of this study was to evaluate whether sclerotic changes of alveolar bone or thickening of lamina dura in patients using BP can be detected using the subtraction function of Emago.

METHODS

The authors selected 46 pairs of intraoral radiographs of the mandibular molar area in dental patients. All radiographs were obtained at intervals of 6 months or more. Among the 46 pairs, 7 pairs were from patients who were being treated with BP (study subjects), and 39 pairs were from patients who had not been using BP (controls). All pairs of radiographs underwent digital subtraction by Emago. The number of pixels of the sclerotic areas was counted and compared between subjects and controls.

RESULTS

The sclerotic changes were significantly distinguishable in two of the seven subjects (28.6%) using BP.

CONCLUSIONS

Digital subtraction function of Emago was able to detect sclerotic changes in alveolar bone. Therefore, it is suggested that the subtraction function of Emago is a useful tool for quantitatively detecting sclerotic changes that are observed at an early, silent stage of BP-related osteonecrosis of the jaw.

Stenotrophomonas maltophilia strains isolated from a university hospital in Japan: genomic variability and antibiotic resistance

The diversity within the genetic and antibiotic resistance profiles and the production of virulence-associated enzymic activities of 66 Stenotrophomonas maltophilia strains collected from a university hospital in Japan in 2005 were studied. PFGE analysis of the collection indicated that a variety of profiles were present. MLST analysis of nine selected strains showed that four of the six sequence types identified were novel. These results indicated that there was a high degree of genetic diversity between the strains and that S. maltophilia strains isolated in Japan might be genetically divergent from those in Europe. The majority of strains were resistant to piperacillin (93.9 %), ceftazidime (84.8 %), imipenem (100 %), aztreonam (98.5 %), gentamicin (81.8 %), amikacin (87.9 %), ciprofloxacin (84.8 %), tetracycline (97.0 %) and chloramphenicol (78.8 %), although levofloxacin was effective against 77.3 % of the strains. Most of the strains showed multidrug resistance and carried the class 1 integron, but no strain showed transmission of antibiotic resistance by conjugation. Although haemolytic activity was not detected in any of the strains, protease and lipase activities were detected in 86.4 % and 31.8 % of the strains, respectively.

Sympathectomy attenuates excitability of dorsal root ganglion neurons and pain behaviour in a lumbar radiculopathy model

Objectives

In order to elucidate the influence of sympathetic nerves on lumbar radiculopathy, we investigated whether sympathectomy attenuated pain behaviour and altered the electrical properties of the dorsal root ganglion (DRG) neurons in a rat model of lumbar root constriction.

Methods

Sprague-Dawley rats were divided into three experimental groups. In the root constriction group, the left L5 spinal nerve root was ligated proximal to the DRG as a lumbar radiculopathy model. In the root constriction + sympathectomy group, sympathectomy was performed after the root constriction procedure. In the control group, no procedures were performed. In order to evaluate the pain relief effect of sympathectomy, behavioural analysis using mechanical and thermal stimulation was performed. In order to evaluate the excitability of the DRG neurons, we recorded action potentials of the isolated single DRG neuron by the whole-cell patch-clamp method.

Results

In behavioural analysis, sympathectomy attenuated the mechanical allodynia and thermal hyperalgesia caused by lumbar root constriction. In electrophysiological analysis, single isolated DRG neurons with root constriction exhibited lower threshold current, more depolarised resting membrane potential, prolonged action potential duration, and more depolarisation frequency. These hyperexcitable alterations caused by root constriction were significantly attenuated in rats treated with surgical sympathectomy.

Conclusion

The present results suggest that sympathectomy attenuates lumbar radicular pain resulting from root constriction by altering the electrical property of the DRG neuron itself. Thus, the sympathetic nervous system was closely associated with lumbar radicular pain, and suppressing the activity of the sympathetic nervous system may therefore lead to pain relief.

Amelogenin enhances the osteogenic differentiation of mesenchymal stem cells derived from bone marrow

Amelogenins are the major constituent of developing extracellular enamel matrix proteins and are understood to have an exclusively epithelial origin. Recent studies have demonstrated that amelogenins can be detected in other tissues, including bone marrow mesenchymal stem cells (MSCs), but the role of amelogenins in MSCs remains unclear. The purpose of this study was to examine the effect of recombinant human full-length amelogenin (rh174) on the osteogenic differentiation of cultured human MSCs. MSCs isolated from human bone marrow were cultured in osteoblastic differentiation medium with 0, 10 or 100 ng/ml rh174. The mRNA levels of bone markers were examined by real-time PCR analysis. Alkaline phosphatase (ALP) activity and calcium concentration were determined. Mineralization was evaluated by alizarin red staining. The mRNA levels of ALP, type I collagen, osteopontin and bone sialoprotein in the MSCs treated with rh174 became significantly higher than those in non-treated controls. Treatment of MSCs with rh174 also enhanced ALP activity and calcium concentration, resulting in enhanced mineralization, as denoted by high intensity of alizarin red staining. In conclusion, the present study showed that rh174 enhances the mineralization accompanied by the upregulation of bone markers in human bone marrow MSCs during osteogenic differentiation, suggesting a certain role of amelogenin in the modulation of osteogenic differentiation of MSCs.

Correlation between genotype and supernumerary tooth formation in cleidocranial dysplasia

INTRODUCTION

Cleidocranial dysplasia (CCD, MIM#119600), for which the responsible gene is RUNX2, is a genetic disorder characterized by hypoplasia or aplasia of the clavicles, patent fontanelles, and a short stature. Supernumerary teeth and delayed eruption and impaction of permanent teeth are frequently associated with CCD. Our previous study reported wide intrafamilial variation in supernumerary tooth formation associated with a mutation in the RUNT-domain of RUNX2, suggesting a low correlation between the genotype and supernumerary tooth formation. To further clarify this point, a more precise evaluation was performed.

DESIGN

Gene mutational analysis of nine Japanese individuals with CCD was performed. Dental and skeletal characteristics were examined based on patient examinations and radiographs.

RESULTS

Four different gene mutations, including one novel mutation in RUNX2 gene (NM_001024630), were identified. Among them, four individuals had the R225Q mutation, three siblings had the P224S mutation, and the other two individuals had different frame-shift mutations. Wide variations in supernumerary tooth formation were observed in individuals with identical gene mutations, and discordance was seen between monozygotic twins. Asymmetric supernumerary tooth formation was noted in five out of the nine individuals.

CONCLUSION

Individuals with identical gene mutations showed a wide variation in the supernumerary tooth formation. Not only the genotype but also environmental factors and a complex system including epigenetics and copy number variation might regulate supernumerary tooth formation in CCD.

Radiographic findings and prognosis of simple bone cysts of the jaws

OBJECTIVE

The aim was to evaluate the possibility of radiographic prediction of the prognosis of simple bone cysts (SBCs) of the jaws.

METHODS

The relationship between the radiographic findings and treatment outcome (healing or recurrence) was investigated in 31 cases treated in the authors' hospital and 108 published cases.

RESULTS

In 17 of our 31 cases, the lesions had radiographic findings of a preserved lamina dura adjacent to the lesion, with a smooth margin, and no or smooth bone expansion, and all of them healed after surgery. In the other 14 cases, there was resorption of the lamina dura, a scalloped margin, nodular bone expansion, root resorption, a sclerotic mass or multiple cavities, and nine cases of recurrence. Although there was incomplete information in the published case studies, similar results were noted.

CONCLUSIONS

It was concluded that there was a relationship between the radiographic features of the lesions and prognosis. Radiographic examination should be used not only for discovering and diagnosing the lesions, but also for predicting possible prognosis.