Molecular characterization of a carbon dioxide-dependent Proteus mirabilis small-colony variant isolated from a clinical specimen.

INTRODUCTION: Carbon dioxide-dependent Proteus mirabilis has been isolated from clinical specimens. It is not clear whether mutations in carbonic anhydrase are responsible for the carbon dioxide dependence of P. mirabilis. The pathogenicity of carbon dioxide-dependent P. mirabilis also remains unclear. The purpose of this study was to determine the cause carbon dioxide dependence of P. mirabilis and its pathogenicity. METHODS: The DNA sequence of can encoding carbonic anhydrase of a carbon dioxide-dependent P. mirabilis small colony variant (SCV) isolate was analyzed. To confirm that impaired carbonic anhydrase activity is responsible for the formation of the carbon dioxide-dependent SCV phenotype of P. mirabilis, we performed complementation experiments using plasmids with intact can. Additionally, mouse infection experiments were performed to confirm the change in virulence due to the mutation of carbonic anhydrase. RESULTS: We found that the can gene of the carbon dioxide-dependent P. mirabilis SCV isolate showed had a frameshift mutation with a deletion of 1 bp (c. 173delC). The can of P. mirabilis encodes carbonic anhydrase was also found to function in Escherichia coli. The cause of the carbon dioxide-dependent SCV phenotype of P. mirabilis was an abnormality in carbonic anhydrase. Nevertheless, no changes were observed in virulence due to the mutation of carbonic anhydrase in mouse infection experiments. CONCLUSIONS: The can gene is essential for the growth of P. mirabilis in ambient air. The mechanisms underlying this fitness advantage in terms of infection warrant further investigation.

A case of acute bacterial cystitis caused by carbon dioxide-dependent Escherichia coli with a deletion mutation in the can.

A small-colony variant (SCV) of carbon dioxide-dependent Escherichia coli was isolated from a patient with acute bacterial cystitis. After the urine sample was inoculated on 5% sheep blood agar and incubated overnight at 35 °C in ambient air, no colony formation was observed. However, after overnight incubation at 35 °C in 5% CO2-enhanced ambient air, numerous colonies were obtained. We failed to characterize or identify the SCV isolate using the MicroScan WalkAway-40 System because the isolate did not grow in the system. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and 16S rRNA sequencing were useful for identifying this SCV isolate. Genome sequencing analysis of the isolates revealed the presence of an 11-bp deletion mutation leading to premature translational truncation in the carbonic anhydrase gene, can, and the presence of 10 known antimicrobial resistance genes. The results of the antimicrobial susceptibility tests performed under CO2-enhanced ambient air were consistent with the presence of antimicrobial resistance genes. Our results also showed that Can is important to grow E. coli in ambient air, and that antimicrobial susceptibility testing of carbon dioxide-dependent SCVs should be performed in 5% CO2-enhanced ambient air. A revertant strain was obtained by passaging the SCV isolate, but the deletion mutation in can remained. To the best of our knowledge, this is the first case in Japan of acute bacterial cystitis caused by carbon dioxide-dependent E. coli with a deletion mutation in can.

First description of a clinical glutamine-dependent Escherichia coli with a missense mutation in the glnA.

INTRODUCTION: Small-colony variants (SCVs) of bacteria are subpopulations with a small colony size, low growth rate, and atypical colony morphology. The purpose of this study was to comprehensively elucidate the characteristics and underlying mechanism of the development of a glutamine-dependent SCV of E. coli, GU-92SCV, isolated from the blood of a patient with pyelonephritis. METHODS: The GU-92SCV strain was tested for auxotrophy testing for glutamine. DNA mutations in genes related to glutamine synthesis were analysed by sequencing. The isolate's proliferation and antimicrobial susceptibility in Mueller-Hinton II medium supplemented with glutamine were examined. RESULTS: The colony of the GU-92SCV strain did not grow on Mueller-Hinton II agar, but growth around the filter paper containing l-glutamine was enhanced on Mueller-Hinton II agar. The GU-92SCV strain had a single nucleotide substitution in glnA, c.193G>A, corresponding to p.Asp65Asn. Changing c.193G>A to the wild-type sequence in glnA restored these phenotypes. Because GU-92SCV did not grow in Mueller-Hinton II broth, antimicrobial susceptibility test results were not obtained; however, in the presence of 10 mg mL-1l-glutamine, the results were consistent with those of the revertant strain GU-92REV. CONCLUSION: To the best of our knowledge, this is the first clinical isolation of a glutamine-dependent E. coli SCV from a patient blood culture. Our data showed that glnA was important for the growth of E. coli in Mueller-Hinton II medium, which also required the presence of glutamine when performing antimicrobial susceptibility testing for glutamine-dependent SCV strains.

Serological Screening of Immunoglobulin G against SARS-CoV-2 Nucleocapsid and Spike Protein before and after Two Vaccine Doses among Healthcare Workers in Japan.

This study sought to evaluate the effects of two vaccine doses and the extent of SARS-CoV-2 infection among healthcare workers. We measured immunoglobulin G antibody titers against SARS-CoV-2 nucleocapsid and spike protein among healthcare workers at Gunma University Hospital. In March 2021, prior to BNT-162b2 vaccination, two of 771 participants were seropositive for nucleocapsid and spike protein, whereas 768 were seronegative. The remaining one participant was seropositive for nucleocapsid protein but seronegative for spike protein. A total of 769 participants were seropositive for spike protein after two vaccination doses. The two seropositive participants prior to vaccination showed the highest antibody titers after the second vaccination. They were probably infected with SARS-CoV-2 without clinical symptoms before March 2021. Four weeks after the second vaccination, a younger age was associated with higher antibody titers against SARS-CoV-2 spike protein. Thirty-two weeks after the second vaccination, blood samples were collected from 342 of 769 participants. Antibody titers at 32 weeks after the second vaccination significantly decreased compared with those at 4 weeks after the second vaccination among all age groups. The rate of decrease in antibody titers between 4 and 32 weeks after the second vaccination was greater in the female participants. No sex differences were observed in the antibody titers within each age group. BNT-162b2 vaccination thus induced seroconversion in an age-dependent manner. Serological screening could further establish the likelihood of subclinical SARS-CoV-2 infection.

Effects of Er:YAG and Diode Laser Irradiation on Dental Pulp Cells and Tissues.

Vital pulp therapy (VPT) is to preserve the nerve and maintain healthy dental pulp tissue. Laser irradiation (LI) is beneficial for VPT. Understanding how LI affects dental pulp cells and tissues is necessary to elucidate the mechanism of reparative dentin and dentin regeneration. Here, we show how Er:YAG-LI and diode-LI modulated cell proliferation, apoptosis, gene expression, protease activation, and mineralization induction in dental pulp cells and tissues using cell culture, immunohistochemical, genetic, and protein analysis techniques. Both LIs promoted proliferation in porcine dental pulp-derived cell lines (PPU-7), although the cell growth rate between the LIs was different. In addition to proliferation, both LIs also caused apoptosis; however, the apoptotic index for Er:YAG-LI was higher than that for diode-LI. The mRNA level of odontoblastic gene markers-two dentin sialophosphoprotein splicing variants and matrix metalloprotease (MMP)20 were enhanced by diode-LI, whereas MMP2 was increased by Er:YAG-LI. Both LIs enhanced alkaline phosphatase activity, suggesting that they may help induce PPU-7 differentiation into odontoblast-like cells. In terms of mineralization induction, the LIs were not significantly different, although their cell reactivity was likely different. Both LIs activated four MMPs in porcine dental pulp tissues. We helped elucidate how reparative dentin is formed during laser treatments.

Potential function of TGF-ß isoforms in maturation-stage ameloblasts.

OBJECTIVES: To investigate potential functions of transforming growth factor-beta (TGF-ß) isoforms in maturation-stage ameloblasts during amelogenesis. METHODS: In vivo activation of TGF-ß was characterized by using matrix metalloproteinase 20 null (Mmp20-/-) and wild-type (Mmp20+/+) mice. Using mHAT9d cells cultured in the presence of each TGF-ß isoform, (1) cell proliferation was determined by MTS assay, (2) immunostaining with anti-cleaved caspase-3 monoclonal antibody was performed and apoptotic indices were measured, (3) gene expression was analyzed by RT-qPCR, and (4) the uptake of amelogenin into mHAT9d cells was directly observed using a fluorescence microscope. RESULTS: TGF-ß1 and TGF-ß3 were present in the enamel matrix of developing teeth which were activated by MMP20 in vivo. A genetic study revealed that the three TGF-ß isoforms upregulate kallikrein 4 (KLK4) mRNA levels but downregulate carbonic anhydrase II. Moreover, TGF-ß1 and TGF-ß2 significantly upregulated the mRNA level of amelotin, whereas TGF-ß3 dramatically downregulated the mRNA levels of odontogenic ameloblast-associated protein (ODAM), family with sequence similarity 83 member H (FAM83H), and alkaline phosphatase (ALP). Immunostaining analysis showed that the apoptosis of mHAT9d cells is induced by three TGF-ß isoforms, with TGF-ß3 being most effective. Both TGF-ß1 and TGF-ß3 induced endocytosis of amelogenin. CONCLUSIONS: We propose that TGF-ß is regulated in an isoform-specific manner to perform multiple biological functions such as gene expression related to the structure of basal lamina/ameloblasts, mineral ion transport, apoptosis, and endocytosis in maturation-stage ameloblasts.

The dynamics of TGF-ß in dental pulp, odontoblasts and dentin.

Transforming growth factor-beta (TGF-ß) is critical for cell proliferation and differentiation in dental pulp. Here, we show the dynamic mechanisms of TGF-ß in porcine dental pulp, odontoblasts and dentin. The mRNA of latent TGF-ß1 and TGF-ß3 is predominantly expressed in odontoblasts, whereas the mRNA expression level of latent TGF-ß2 is high in dental pulp. TGF-ß1 is a major isoform of TGF-ß, and latent TGF-ß1, synthesized in dental pulp, is primarily activated by matrix metalloproteinase 11 (MMP11). Activated TGF-ß1 enhances the mRNA expression levels of MMP20 and full-length dentin sialophosphoprotein (DSPP) in dental pulp cells, coinciding with the induction of odontoblast differentiation. Latent TGF-ß1 synthesized in odontoblasts is primarily activated by MMP2 and MMP20 in both odontoblasts and dentin. The activity level of TGF-ß1 was reduced in the dentin of MMP20 null mice, although the amount of latent TGF-ß1 expression did not change between wild-type and MMP20 null mice. TGF-ß1 activity was reduced with the degradation of DSPP-derived proteins that occurs with ageing. We propose that to exert its multiple biological functions, TGF-ß1 is involved in a complicated dynamic interaction with matrix metalloproteinases (MMPs) and/or DSPP-derived proteins present in dental pulp, odontoblasts and dentin.