David R. Drake

Thematic Review Series: Skin Lipids. Antimicrobial lipids at the skin surface

The skin surface represents our interface with the external environment, and as such, is our first line of defense against microbial colonization and infection. Lipids at the skin surface are thought to underlie at least part of an antimicrobial barrier. Some of these lipids are synthesized in the epidermis and are carried to the surface as cells differentiate, whereas others are secreted onto the surface from the sebaceous glands. One such group, free sphingoid bases, are known to have broad antimicrobial activity, and our previous studies demonstrate their presence at the skin surface. Free sphingoid bases may be generated by enzymatic hydrolysis of epidermal ceramides. In addition, our preliminary results demonstrate potent antibacterial activity associated with two specific fatty acids derived from sebaceous triglycerides. Most remarkably, one of these fatty acids (sapienic acid, C16:1Δ6), in combination with a low concentration of ethanol, is very effective against methicillin-resistant Staphylococcus aureus (MRSA). In fact, this combination was far more effective than mupirocin with or without ethanol. Mupirocin is a “gold standard” for activity against MRSA.

Bacterial retention in canal walls in vitro: Effect of smear layer

When dentin is planed by endodontic instruments, a smear layer forms. Whether this layer should be removed is unknown and controversial. This study was conducted to assess the effect of the smear layer on retention of bacteria using an in vitro root canal bacterial colonization model. Canals of 26 extracted human canines were step-back prepared using 2.5% NaOCl. Teeth were then randomly divided into two groups based on the type of high volume final flush: 1-20 ml of sterile saline (0.85% wt/vol) or (2-10 ml of 17% EDTA followed by 10 ml of 2.5% NaOCl which removes smear layer. Streptococcus anginosus (milleri) was cultured in trypticase soy broth supplemented with 0.5% yeast extract at 37 degrees C in 5% CO2. Cells were harvested by centrifugation and resuspended in fresh media. Serial dilutions were performed to achieve inocula of 10(6) colony-forming units in a 30-microliters volume. Teeth were inoculated and incubated for 2 h in 5% CO2 at 37 degrees C. Following incubation, teeth were split and processed for microbiological analysis. Numbers of colonizing bacteria were determined by a spiral-plating system. Enumeration of the numbers of bacteria revealed a reproducible, order of magnitude difference (p = 0.0002) between teeth with smear layer (10(4) colony-forming units) versus teeth without smear layer (10(5) colony-forming units). This suggests that smear layer produced during root canal therapy may inhibit bacterial colonization of root canals. One suggested mechanism is that smear layer may block bacterial entry into dentinal tubules.

BACTERIAL PENETRATION THROUGH CANALS OF ENDODONTICALLY TREATED TEETH IN THE PRESENCE OR ABSENCE OF THE SMEAR LAYER

OBJECTIVES The goal of this study is to determine if the smear layer affects the passage of bacteria through or around obturating material as evidenced by penetration of bacteria through and out the canal. Specifically, this study focused on determining the effect of the smear layer on the magnitude of bacterial penetration through the apical foramen. METHODS Thirty extracted, maxillary central or lateral incisors were collected. Teeth were randomly assigned (10 teeth per group) to three groups: (1) smear layer removed, (2) smear layer present, and (3) negative control. Canal preparation and obturation using lateral condensation, gutta percha, and AH 26 sealer was performed on all of the teeth. Removal of the smear layer was accomplished by rinsing with 17% EDTA. The model systems consisted of an upper chamber attached to the cemento-enamel junction and a lower chamber at the apices of the teeth. Standardized bacterial suspensions containing Fusobacterium nucleatum, Campylobacter rectus, and Peptostreptococcus micros were inoculated into the upper chambers. Models were incubated anaerobically at 37 degrees C. At various times over a 60-day period, samples were taken from the lower chamber and spiral-plated on selective-differential media to determine numbers and types of bacteria. RESULTS Leakage results were as follows: (1) smear layer present-6/10 leaked; (2) smear layer removed-0/10 leaked; (3) negative control-0/10 leaked. Profiles of bacterial leakage were similar among the groups. F. nucleatum was the predominant microorganism. CONCLUSIONS This study indicated that removal of the smear layer reduced the leakage of bacteria through the root canal system.

A longitudinal study of dental caries risk among very young low SES children.

OBJECTIVES Early childhood caries (ECC) is a challenging public health problem in the United States and elsewhere; however, there is limited information concerning risk factors in very young children. The purpose of this study was to assess baseline risk factors for 18-month caries prevalence as part of a longitudinal study of high-risk children. METHODS About 212 children, 6-24 months of age were recruited from a rural community in Iowa. Subjects were enrolled in the WIC program, which provides nutritional support for low-income families with children. Dental examinations using d1, d2-3 criteria were conducted at baseline and after 18 months. Caries prevalence was determined at the frank decay level (d2-3 or filled surfaces), as well as at the noncavitated level (d1), and combined (d1, d2-3 or f surfaces). Risk factor data were collected at baseline and after 9- and 18- months. These data included beverage consumption data, presence of visible plaque, and use of fluoride toothpaste for children as well as mutans streptococci (MS) levels of mothers and children and family sociodemographic factors. RESULTS About 128 children (60%) remained in the study after 18 months. Among these children, prevalence of d1,d2-3/f level caries increased from 9% to 77%, while d2-3/f level caries increased from 2% to 20%. Logistic regression models for baseline predictors of d2-3f caries at the 18-month follow-up found the presence of MS in children (OR=4.4; 95% CI: 1.4, 13.9) and sugar-sweetened beverages (OR=3.0; 95% CI: 1.1, 8.6) to be the only significant risk factors. Sociodemographic factors and the use of fluoride toothpaste were not significant in these models. CONCLUSIONS Results suggest that early colonization by MS and consumption of sugar-sweetened beverages are significant predictors of ECC in high-risk populations.

Antimicrobial Susceptibility of Monoculture Biofilms of a Clinical Isolate of Enterococcus faecalis

The purpose of this study was to create a monoculture biofilm of a clinical isolate of Enterococcus faecalis and to determine susceptibility against four antimicrobial irrigants. Biofilms were subjected to 1-, 3-, and 5-minute exposures to one of the following irrigants: 6% sodium hypochlorite (NaOCl), 2% chlorhexidine gluconate (CHX) or one of two new products, <6% NaOCl with surface modifiers (Chlor-XTRA) or 2% CHX with surface modifiers (CHX-Plus) (Vista Dental Products, Racine, WI). It was hypothesized that NaOCl and CHX would be equally effective and that addition of surface modifiers would improve bactericidal activity of the respective irrigants compared to the original formulations. Results indicate that 6% NaOCl and Chlor-EXTRA were significantly superior against E. faecalis biolfilms compared to 2% CHX and CHX-Plus at all time points except five minutes.

Antimicrobial lipids at the skin surface

One of the most common conditions of the skin is Atopic dermatitis (AD) which usually occurs in infants but can also occur among children and adults. The predefined aim of the study was to analyze the affects of AD on the quality of life (QOL) of children or adults and to recognize the most affected areas of a patient’s life. QOL is an expansive concept and covers various dimensions of the human life that deals with the understanding of impacts that a disease can have on the QOL of an individual. It also tries to comprehend the outcomes associated with the treatment of patient and the burden of disease. Currently, the awareness regarding the measurement of QOL has augmented, as it would be helpful for the physicians to have awareness regarding the patient’s views about their illness and its impact on their wellbeing. In order to understand the impact of AD on the patient’s life and to understand whether the QOL of the public differs from that of the AD patient, evaluation of the QOL is imperative in the clinical field. The research in this regards is mandatory to make better decisions regarding resource allocation in dermatology to prevent it from suffering the consequences of lack of knowledge. Life threatening conditions as well as social and psychological consequences of this disease has not been documented yet, but information regarding its impact on QOL will be helpful in overcoming this disease.Results: Sixty histologically diagnosed cutaneous malignancies presented to UCTH, Calabar, [55(92%) patients with primary cutaneous malignancies while 5(8%) were metastatic cutaneous cancer]. The 5 patients comprised 2 men and 3 women with ages that ranged from 3775 years (mean 59.2 years). The site distribution was 3(75%) anterior abdominal wall [2umbilicus, Figure 1a, 1laparotomy scar], 1Back – left scapular region and 1 – wide spread cutaneous lesions (from head to the foot), Figure 2a. Two (40%) patients presented with malignant intestinal obstruction, Table 1. The histology of the cutaneous lesions revealed, 4 (80%) patients with metastatic adenocarcinoma, Figure 1b, 3 from proven colonic sites, one suspicious and one with metastatic olfactory neuroblastoma, Figure 2b. The later was the patient with wide spread cutaneous lesions. These nodules remarkably occurred during chemotherapy and radiotherapy for the primary left eye lesion that appeared to be responding to therapy. The outcomes were uniformly poor due to advanced primary lesions at presentation.Introduction & objective: Acne scars are extremely bothersome to patients and often challenging to treat. Regarding texture, they are divided into the scars with normal texture and the scars with atrophic texture. The acne scars with atrophic texture consist of ice pick, boxcarand rolled scars. Topical, physical, surgical, and light modalities, alone or in combination have been administered in the treatment of acne scars with variable results. Herein, for the first time I introduced serum injection therapy as a novel effective therapeutic option for the atrophic acne scars.

Coronal leakage: Endotoxin penetration from mixed bacterial communities through obturated, post-prepared root canals

Coronal leakage has been considered as one of the major causes of failure in root canal treatment. Bacteria have been shown to penetrate the root canal obturating materials and influence the periapical tissues. Endotoxin, a component of Gram-negative bacteria, is a potent inflammatory agent and may be able to penetrate obturating materials faster than bacteria. This in vitro study examined the possible penetration of post-prepared canals by endotoxin and bacterial cells derived from mixed bacterial communities. Results showed that both bacteria and endotoxin were able to penetrate the obturating materials in post-prepared canals; however, endotoxin penetration was faster than bacterial. If one speculates that a similar sequence of events occurs clinically, then such a rapid penetration of endotoxin could lead to an early periapical reaction, with subsequent treatment failure and need for retreatment or periapical surgery. The need for an immediate and proper coronal restoration after root canal treatment is therefore reinforced.

Antibacterial Activity of Sphingoid Bases and Fatty Acids against Gram-Positive and Gram-Negative Bacteria

ABSTRACT There is growing evidence that the role of lipids in innate immunity is more important than previously realized. How lipids interact with bacteria to achieve a level of protection, however, is still poorly understood. To begin to address the mechanisms of antibacterial activity, we determined MICs and minimum bactericidal concentrations (MBCs) of lipids common to the skin and oral cavity—the sphingoid bases d-sphingosine, phytosphingosine, and dihydrosphingosine and the fatty acids sapienic acid and lauric acid—against four Gram-negative bacteria and seven Gram-positive bacteria. Exact Kruskal-Wallis tests of these values showed differences among lipid treatments (P < 0.0001) for each bacterial species except Serratia marcescens and Pseudomonas aeruginosa. d-Sphingosine (MBC range, 0.3 to 19.6 μg/ml), dihydrosphingosine (MBC range, 0.6 to 39.1 μg/ml), and phytosphingosine (MBC range, 3.3 to 62.5 μg/ml) were active against all bacteria except S. marcescens and P. aeruginosa (MBC > 500 μg/ml). Sapienic acid (MBC range, 31.3 to 375.0 μg/ml) was active against Streptococcus sanguinis, Streptococcus mitis, and Fusobacterium nucleatum but not active against Escherichia coli, Staphylococcus aureus, S. marcescens, P. aeruginosa, Corynebacterium bovis, Corynebacterium striatum, and Corynebacterium jeikeium (MBC > 500 μg/ml). Lauric acid (MBC range, 6.8 to 375.0 μg/ml) was active against all bacteria except E. coli, S. marcescens, and P. aeruginosa (MBC > 500 μg/ml). Complete killing was achieved as early as 0.5 h for some lipids but took as long as 24 h for others. Hence, sphingoid bases and fatty acids have different antibacterial activities and may have potential for prophylactic or therapeutic intervention in infection.

Gas flow dependence for plasma-needle disinfection of S. mutans bacteria

The role of gas flow and transport mechanisms are studied for a small low-power impinging jet of weakly-ionized helium at atmospheric pressure. This plasma needle produces a non-thermal glow discharge plasma that kills bacteria. A culture of Streptococcus mutans (S. mutans) was plated onto the surface of agar, and spots on this surface were then treated with plasma. Afterwards, the sample was incubated and then imaged. These images, which serve as a biological diagnostic for characterizing the plasma, show a distinctive spatial pattern for killing that depends on the gas flow rate. As the flow is increased, the killing pattern varies from a solid circle to a ring. Images of the glow reveal that the spatial distribution of energetic electrons corresponds to the observed killing pattern. This suggests that a bactericidal species is generated in the gas phase by energetic electrons less than a millimetre from the sample surface. Mixing of air into the helium plasma is required to generate the observed O and OH radicals in the flowing plasma. Hydrodynamic processes involved in this mixing are buoyancy, diffusion and turbulence.

Coronal leakage of mixed anaerobic bacteria after obturation and post space preparation

OBJECTIVES The purpose of this study was to assess bacterial leakage of a mixed anaerobic community of organisms in obturated canals after post space preparation. STUDY DESIGN A mixed microbial community of strict anaerobic organisms (F. nucleatum, P. micros and C. rectus) was developed. With the use of an in vitro model system, coronal leakage was assessed in 40 anterior teeth after obturation and post space preparation. The specific leakage time in days for each organism to penetrate through the obturating material was determined. In addition, colonization of the apical canal space was assessed by scanning electron microscope after longitudinal splitting of randomly selected specimens. RESULTS Eighty percent of the teeth demonstrated coronal leakage of F. nucleatum and C. rectus by the 90 day interval. Bacterial penetration occurred from 48 days to 84 days. Scanning electron microscope examination showed a heterogeneous biofilm of coccal and bacillary species colonizing the apical portion of the canal wall. CONCLUSIONS This study demonstrated that coronal leakage phenomena do occur after loss of coronal seals. The model system developed using mixed, anaerobic bacterial cultures is more clinically relevant and may be used to assess bacterial penetration through gutta percha obturation.