Antimicrobial susceptibility of periodontopathogenic bacteria

Objectives The aim of this study was to evaluate the resistance profiles of Aggregatibacter (Actinobacillus) actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia/Prevotella nigrescens and to detect possible changes in antibiotic resistance over the time period of 1991-2005. Methods A. actinomycetemcomitans (125 strains), P. gingivalis (152 strains) and P. intermedia/P. nigrescens (326 strains) isolated during the years 1991-2005 were tested for their susceptibility to amoxicillin/clavulanic acid, clindamycin, metronidazole, phenoxymethylpenicillin and tetracycline using the Etest. Results No antibiotic resistance was detected in P. gingivalis, whereas a few isolates of P. intermedia were not susceptible to clindamycin (0.9%), phenoxymethylpenicillin (13.5%) or tetracycline (12.6%). Amoxicillin/clavulanic acid, tetracycline and metronidazole were the most effective antibiotics against A. actinomycetemcomitans with 0%, 0.8% and 20.8% non-susceptible isolates, respectively. However, 88% of the A. actinomycetemcomitans isolates were non-susceptible to phenoxymethylpenicillin and 88% to clindamycin. When strains isolated in the years 1991-94 were compared with those isolated in the years 2001-04, there was no statistically significant difference in the percentage of A. actinomycetemcomitans strains non-susceptible to clindamycin, metronidazole or phenoxymethylpenicillin, or in the percentage of P. intermedia strains non-susceptible to phenoxymethylpenicillin or tetracycline (P > 0.4 each). Conclusions Increasing antibiotic resistances in periodontopathogenic bacteria are not yet a problem in the Northern part of Switzerlan

Identification of archaeal rDNA from subgingival dental plaque by PCR amplification and sequence analysis

A PCR assay for the amplification of small subunit ribosomal DNA (SSU rDNA) of Euryarchaea was developed and used to detect archaeal rDNA in 37 (77%) out of 48 pooled subgingival plaque samples from 48 patients suffering from periodontal disease. One major group of cloned periodontal sequences was identical to Methanobrevibacter oralis and a second minor group to Methanobrevibacter smithii. These two groups and a third novel group were found to be more than 98% similar to each other over an 0.65-kb segment of the 16S rRNA gene sequenced. M. oralis was found to be the predominant archaeon in the subgingival dental plaque. Phylogenetic analysis of partial SSU rDNA sequences revealed evidence for a distinct cluster for human and animal Methanobrevibacter sp. within the Methanobacteriaceae famil

Antibiotic Resistance among Fusobacterium, Capnocytophaga, and Leptotrichia Species of the Oral Cavity

PURPOSE Antibiotics play an important role in treating periodontal diseases. Due to the effectiveness of antibiotic therapies, their usage in dentistry has significantly increased. The aim of this study focused on the in-vitro susceptibility of different gram-negative oral bacteria species - which are associated with periodontal diseases (Fusobacterium spp., Capnocytophaga spp. and Leptotrichia buccalis) and have different geographical origins (Asia and Europe) - against antimicrobials that are clinically relevant in dental therapy. MATERIALS AND METHODS A total of 45 strains were tested (29 Fusobacterium spp., 13 Capnocytophaga spp. and 3 L. buccalis) that were either isolated from Chinese patients or were obtained from different strain collections. Their antimicrobial susceptibility to the antimicrobial agents benzylpenicillin, amoxicillin, amoxicillin-clavulanic acid, ciprofloxacin, moxifloxacin, clindamycin, doxycycline, tetracycline and metronidazole was tested using the E-Test. Strains with particular resistance to penicillin, clindamycin and metronidazole were further analysed for resistance genes. RESULTS All tested bacterial isolates were sensitive to amoxicillin, amoxicillin-clavulanic acid, doxycycline and tetracycline, but showed variable sensitivity towards other antibiotics such as benzylpenicillin, ciprofloxacin, moxifloxacin, clindamycin and metronidazole. CONCLUSION The results of the present study suggest that certain periodontal disease-related bacterial strains can be resistant towards antimicrobial agents commonly used in adjuvant periodontal therapy

Human hepatic stem cells from fetal and postnatal donors

Human hepatic stem cells (hHpSCs), which are pluripotent precursors of hepatoblasts and thence of hepatocytic and biliary epithelia, are located in ductal plates in fetal livers and in Canals of Hering in adult livers. They can be isolated by immunoselection for epithelial cell adhesion molecule–positive (EpCAM+) cells, and they constitute ∼0.5–2.5% of liver parenchyma of all donor ages. The self-renewal capacity of hHpSCs is indicated by phenotypic stability after expansion for >150 population doublings in a serum-free, defined medium and with a doubling time of ∼36 h. Survival and proliferation of hHpSCs require paracrine signaling by hepatic stellate cells and/or angioblasts that coisolate with them. The hHpSCs are ∼9 μm in diameter, express cytokeratins 8, 18, and 19, CD133/1, telomerase, CD44H, claudin 3, and albumin (weakly). They are negative for α-fetoprotein (AFP), intercellular adhesion molecule (ICAM) 1, and for markers of adult liver cells (cytochrome P450s), hemopoietic cells (CD45), and mesenchymal cells (vascular endothelial growth factor receptor and desmin). If transferred to STO feeders, hHpSCs give rise to hepatoblasts, which are recognizable by cordlike colony morphology and up-regulation of AFP, P4503A7, and ICAM1. Transplantation of freshly isolated EpCAM+ cells or of hHpSCs expanded in culture into NOD/SCID mice results in mature liver tissue expressing human-specific proteins. The hHpSCs are candidates for liver cell therapies

The Magnetoelectric Effect in Transition Metal Oxides: Insights and the Rational Design of New Materials from First Principles

The search for materials displaying a large magnetoelectric effect has occupied researchers for many decades. The rewards could include not only advanced electronics technologies, but also fundamental insights concerning the dielectric and magnetic properties of condensed matter. In this article, we focus on the magnetoelectric effect in transition metal oxides and review the manner in which first-principles calculations have helped guide the search for (and increasingly, predicted) new materials and shed light on the microscopic mechanisms responsible for magnetoelectric phenomena.Comment: 24 pages, 12 figure

Antibiotic Susceptibility Patterns of Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis Strains from Different Decades

The aim of this study was to determine the antibiotic susceptibility patterns of 57 Aggregatibacter actinomycetemcomitans and 56 Porphyromonas gingivalis strains isolated from subgingival biofilm samples of periodontitis patients in Switzerland from 1980 to 2017. The minimal inhibitory concentrations (MIC) of the most commonly used antibiotics in periodontal therapy (amoxicillin, metronidazole, azithromycin, and doxycycline) or in severe body infections (amoxicillin/clavulanic acid, clindamycin, ertapenem, and moxifloxacin) were determined. Furthermore, all the strains were screened for beta-lactamase activity and the presence of selected resistance genes (cfxA, ermF, and tetQ). Overall, there was no significant increase in MIC values over the 37‑year period. Two of the most recent P. gingivalis isolates yielded the highest MIC values. The first isolate was ermF-positive with MIC values >8 µg/mL, 2 µg/mL, and 0.25 µg/mL for clindamycin, azithromycin, and moxifloxacin, respectively. The second isolate showed a high MIC value of 4 µg/mL for moxifloxacin, which was associated with a confirmed single-point mutation in the quinolone resistance-determining region (QRDR) of the gyrA gene. Although there was no significant increase in the antibiotic resistance among the oral bacterial isolates tested, the detection of resistant P. gingivalis isolates underlines the need to optimize the antibiotic therapeutic protocols in dentistry

Antibiotic Susceptibility Patterns of Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis Strains from Different Decades.

The aim of this study was to determine the antibiotic susceptibility patterns of 57 Aggregatibacter actinomycetemcomitans and 56 Porphyromonas gingivalis strains isolated from subgingival biofilm samples of periodontitis patients in Switzerland from 1980 to 2017. The minimal inhibitory concentrations (MIC) of the most commonly used antibiotics in periodontal therapy (amoxicillin, metronidazole, azithromycin, and doxycycline) or in severe body infections (amoxicillin/clavulanic acid, clindamycin, ertapenem, and moxifloxacin) were determined. Furthermore, all the strains were screened for beta-lactamase activity and the presence of selected resistance genes (cfxA, ermF, and tetQ). Overall, there was no significant increase in MIC values over the 37‑year period. Two of the most recent P. gingivalis isolates yielded the highest MIC values. The first isolate was ermF-positive with MIC values >8 µg/mL, 2 µg/mL, and 0.25 µg/mL for clindamycin, azithromycin, and moxifloxacin, respectively. The second isolate showed a high MIC value of 4 µg/mL for moxifloxacin, which was associated with a confirmed single-point mutation in the quinolone resistance-determining region (QRDR) of the gyrA gene. Although there was no significant increase in the antibiotic resistance among the oral bacterial isolates tested, the detection of resistant P. gingivalis isolates underlines the need to optimize the antibiotic therapeutic protocols in dentistry

Awareness of vaccine-preventable diseases and self-reported immune status of Swiss dental healthcare workers

INTRODUCTION: Dental healthcare workers are exposed to various infectious agents that may present an occupational risk. Although vaccinations rank among the most cost-effective health measures, vaccine hesitancy is present among healthcare workers. METHODS: A structured anonymous questionnaire was completed by 1111 dental healthcare workers – dentists, dental hygienists, prophylaxis assistants, dental assistants, dental technicians, and dental students. Demographic data and immunisation status, either by vaccination or by immunity after disease, were collected. Additionally, employers and employees were asked about their current workplace vaccination policy, including questions about information provided on the risk of hepatitis B (HBV) infection, whether HBV vaccination was compulsory and who paid for compulsory vaccinations. RESULTS: The overall response rate was 55.7%. Approximately half of the participants were dentists; only 17 technicians completed the questionnaire. The most common immunisation was for HBV (94.7% of participants). Only 19.2% of participants reported immunisation against human papillomavirus. Uncertainty over immunisation status was highest for Haemophilus influenzae type B (46.7%). Only a minority of participants (17.4%) received a yearly vaccination against seasonal influenza, whereas two-thirds never get vaccinated. The participants’ level of awareness related to the seven general vaccinations (HBV, influenza, measles, mumps, rubella, varicella, and tetanus) was medium to high, whereas their level of awareness related to vaccinations against HBV and influenza was medium. Half of the employees stated that they were informed about the risk of HBV at their current workplace and over three-quarters of employers indicated that they provided such information to their employees. Compulsory HBV vaccination was implemented at approximately half of the dental practices. CONCLUSION: The Swiss dental healthcare workers participating in this study had a medium level of awareness towards vaccinations. Almost all participants were vaccinated against HBV, but they were particularly hesitant about the seasonal influenza vaccination. As a considerable number of participants was unaware of their immunisation status, more comprehensive information on infectious diseases, vaccination and prevention is essential

Antimicrobial efficacy of 3 oral antiseptics containing octenidine, polyhexamethylene biguanide, or Citroxx : can chlorhexidine be replaced?

Use of oral antiseptics decreases the bacterial load in the oral cavity

Tolerance and Persister Formation in Oral Streptococci

The aim of this study was to analyze the potential influence of long-term exposure in subinhibitory concentrations of chlorhexidine on the emergence of tolerant and/or persistent cells in oral streptococci. The two oral streptococcal isolates S. mutans ATCC25175 and S. sobrinus ATCC33402 were incubated, after long-term subinhibitory exposure to chlorhexidine, in liquid growth media containing high concentrations of chlorhexidine. A distinct subpopulation of more chlorhexidine-tolerant cells could be detected in streptococci that had been previously exposed to subinhibitory concentrations of chlorhexidine but not in the control strains. These more biocide-tolerant and persisting microbial subpopulations might also arise in vivo. Therefore, the rational and proper use of antimicrobials in dentistry, especially when used over a long period of time, is crucial