Discover the most talked about and latest scientific content & concepts.

Concept: Streptococcus viridans


Viridans group streptococci (VGS) are a major cause of bacteraemia in neutropenic cancer patients, particularly those receiving fluoroquinolone prophylaxis. In this study, we sought to understand the molecular basis for fluoroquinolone resistance in VGS causing bacteraemia in cancer patients by assigning 115 VGS bloodstream isolates to specific species using multilocus sequence analysis (MLSA), by sequencing the quinolone resistance-determining regions (QRDRs) of gyrA, gyrB, parC and parE, and by testing strain susceptibility to various fluoroquinolones. Non-susceptibility to one or more fluoroquinolones was observed for 78% of isolates, however only 68.7% of patients were receiving fluoroquinolone prophylaxis. All but one of the determinative QRDR polymorphisms occurred in GyrA or ParC, yet the pattern of determinative QRDR polymorphisms was significantly associated with the fluoroquinolone prophylaxis received. By combining MLSA and QRDR data, multiple patients infected with genetically indistinguishable fluoroquinolone-resistant Streptococcus mitis or Streptococcus oralis strains were discovered. Together these data delineate the molecular mechanisms of fluoroquinolone resistance in VGS isolates causing bacteraemia and suggest possible transmission of fluoroquinolone-resistant S. mitis and S. oralis isolates among cancer patients.

Concepts: Streptococcus, Gram positive bacteria, Streptococcaceae, Group A streptococcal infection, Quinolone, Streptococcus viridans, Streptococcus oralis, Streptococcus mitis


Cerebral microbleeds (CMBs) are an important risk factor for stroke and dementia. We have shown that the collagen binding surface Cnm protein expressed on cnm-positive Streptococcus mutans is involved in the development of CMBs. However, whether the collagen binding activity of cnm-positive S. mutans is related to the nature of the CMBs or to cognitive impairment is unclear. Two-hundred seventy nine community residents (70.0 years) were examined for the presence or absence of cnm-positive S. mutans in the saliva by PCR and collagen binding activity, CMBs, and cognitive function were evaluated. Cnm-positive S. mutans was detected more often among subjects with CMBs (p < 0.01) than those without. The risk of CMBs was significantly higher (odds ratio = 14.3) in the group with S. mutans expressing collagen binding activity, as compared to the group without that finding. Deep CMBs were more frequent (67%) and cognitive function was lower among subjects with cnm-positive S. mutans expressing collagen binding activity. This work supports the role of oral health in stroke and dementia and proposes a molecular mechanism for the interaction.

Concepts: Decision making, Enzyme, Streptococcus, Cognition, Perception, Streptococcaceae, Streptococcus mutans, Streptococcus viridans


To evaluate the effect of naringenin on the biofilm formation of Streptococcus mutans (S. mutans), and to investigate its mechanisms of action and biological toxicity.

Concepts: Streptococcus, Biofilm, Dental plaque, Gram positive bacteria, Streptococcaceae, Streptococcus mutans, Streptococcus viridans


To evaluate the effect of pulsed ultrasound toothbrush on the removal of biofilm formed by Streptococcus mutans (S. mutans).

Concepts: Streptococcus, Biofilm, Dental plaque, Tooth enamel, Gram positive bacteria, Streptococcaceae, Streptococcus mutans, Streptococcus viridans


Adherence capacity is one of the principal virulence factors of Streptococcus mutans, and adhesion virulence factors are controlled by small RNAs (sRNAs) at the post-transcriptional level in various bacteria. Here, we aimed to identify and decipher putative adhesion-related sRNAs in clinical strains of S. mutans.

Concepts: Bacteria, Molecular biology, Microbiology, Streptococcus, Biotechnology, Streptococcaceae, Streptococcus mutans, Streptococcus viridans


A novel dual-site recognition protocol was developed for chemiluminescent (CL) detection of Streptococcus mutans (S. mutans) based on a designed antibiotic-affinity strategy. Teicoplanin, a broad-spectrum antibiotic against Gram-positive bacteria, was adopted to functionalize magnetic particles and recognize S. mutans utilizing the strong affinity between this agent and D-Alanyl-D-Alanine peptide moieties in the bacterial cell wall. To achieve ideal specificity for S. mutans detection, rat immunoglobulin G2a (rat IgG2a) tagged with horseradish peroxidase (HRP) was used as the second recognition agent and signal tracer since Fab region of rat IgG2a could bind with streptococcal protein G highly expressed in the cell wall of S. mutans. Thus HRP-tagged sandwich complex of teicoplanin/S. mutans/rat IgG2a was formed on the magnetic particles, followed by a CL quantification of S. mutans based on a HRP-catalyzed luminol-H2O2-p-iodophenol CL reaction. This dual-site recognition protocol showed a linear range of 1.0 × 102-1.0 × 106CFU mL-1and a detection limit of 33 CFU mL-1for S. mutans detection. The whole detection process could be completed within 70min. The recovery tests for food, environmental, pharmaceutical and biological samples showed acceptable recovery values between 83.0% and 110.0%, demonstrating its application potential for detection of bacteria in various sample matrixes.

Concepts: Cell, Bacteria, Microbiology, Streptococcus, Bacterial cell structure, Gram positive bacteria, Streptococcus mutans, Streptococcus viridans


Clinical typing methods of the oral pathogen Streptococcus mutans with molecular analysis can be very specific, but expensive. Repetitive extragenic palindromic PCR (rep-PCR) is a relatively inexpensive pre-screening alternative for isolate selection for additional analyses. This study evaluated the prediction accuracy of using rep-PCR to identify S. mutans multilocus sequence typing (MLST) sequence types (ST) among children and their family members. Potential S. mutans strain sources were evaluated for evidence of transmission.

Concepts: Scientific method, Critical thinking, Streptococcus, Mathematical analysis, Sucrose, Streptococcaceae, Streptococcus mutans, Streptococcus viridans



Vitamin D analogs were identified as compounds that induced lysis of planktonic cultures of Streptococcus mutans in a high-throughput screen of FDA-approved drugs. Previous studies have demonstrated that certain derivatives of Vitamin D possess lytic activity against other bacteria, though the mechanism has not yet been established. Through the use of a combinatorial approach, the Vitamin D derivative doxercalciferol was shown to act synergistically with bacitracin, a polypeptide-type drug that is known to interfere with cell wall synthesis, suggesting that doxercalciferol may act in a bacitracin-related pathway. Innate resistance to bacitracin is attributed to efflux by a conserved ABC-type transporter, which in S. mutans is encoded by the mbrABCD operon. S. mutans possesses two characterized resistance mechanisms to bacitracin including the ABC transporter, S. mutansbacitracin resistance (Mbr) cassette, consisting of MbrABCD, and the rhamnose-glucose polysaccharide (Rgp) system, RgpABCDEFGHI. Loss of function of the transporter, in ΔmbrA or ΔmbrD mutants, exacerbated the effect of combination of doxercalciferol and bacitracin. Despite conservation of a transporter homologous to mbrABCD, the combination of doxercalciferol and bacitracin appeared to only be synergistic in streptococcal species. We conclude that Vitamin D-derivatives possess lytic activity against S. mutans and act through a mechanism dependent on the bacitracin-resistance mechanism of MbrABCD.

Concepts: Archaea, Bacteria, Antibiotic resistance, Streptococcus, Cell wall, Streptococcaceae, Streptococcus mutans, Streptococcus viridans


To evaluate the effectiveness of prophylactic systemic moxifloxacin in a rabbit model of Streptococcus viridans (S. viridans) endophthalmitis.

Concepts: Streptococcus, Hemolysis, Gram positive bacteria, Streptococcaceae, Streptococcus mutans, Streptococcus viridans, Optochin