Ethel Suman

Background: Klebsiella pneumoniae is a major pathogen that causes ventilator-associated pneumonia and can produce biofilms on endotracheal tubes. This can act as a diffusive barrier, hindering the treatment of infections caused by multidrug-resistant strains of the pathogen. Treatment of such multidrug-resistant strains has become a major challenge and a global problem. Among the various alternative methods used to combat this problem, the use of specific bacteriophages appears to be quite encouraging. This study aimed to isolate and perform phenotypic characterisation of Klebsiella-specific phage from sewage water and compare the effects of Klebsiella-specific phage and subinhibitory concentrations of meropenem on in vitro biofilm production by the respiratory clinical isolates of Klebsiella pneumoniae . Methods: Isolation and phenotypic characterisation of Klebsiella-specific phage from sewage water was done using K.pneumoniae subspp.pneumoniae ATCC 33495 as the host bacterium. The antibiofilm activity of the isolated phage was studied on 40 respiratory clinical isolates of Klebsiella pneumoniae . Their biofilm production was performed on endotracheal tubing pieces in microtiter plates as well as in the presence of Klebsiella-specific phage, subinhibitory concentrations of meropenem, and a combination of Klebsiella-specific phage and meropenem. Results: Transmission Electron Microscopy (TEM) confirmed a classic Myoviridae structure—an icosahedral head (50-100 nm) with a contractile tail sheath and a complex baseplate. Other characteristics included a latent period of 20 minutes and a burst size of 69 phage particles per cell, with a multiplicity of infection being 10, with strong host-killing ability and was stable and infective at 25 °C and a neutral pH range (6-7) Subinhibitory concentration of meropenem brought about a significant decrease in biofilm production (p<0.001) in 91.3% of meropenem-sensitive but significantly increased in 100% of meropenem-resistant strains. The combination of bacteriophage and meropenem had a synergistic effect, resulting in significant reduction in both the meropenem-sensitive and resistant strains Conclusion: This study suggests the potential application of specific phage-coated and antibiotic-coated endotracheal tubing in preventing biofilms, thereby reducing the risk of ventilator-associated pneumonia.

Background: Antimicrobial resistance exhibited by bacteria against the major-ity of antibiotics has resulted in research on alternative methods of treatment. Aloe vera has a strong tradition as a medical plant with a wide range of therapeutic uses. Objective: The objective of this study is to determine the antibacterial activity of gel and crude ethanol leaf extract of Aloe vera against Staphylococcus aureus and Enterobacter-ales isolated from wound infections. Methods: It is a cross-sectional study conducted over a period of 7 months. Antibacterial effect of the ethanol leaf extract and gel was determined by the punch well method. Min-imum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the ethanol leaf extract were determined by macro broth dilution technique. Results: Aloe vera ethanol leaf extract induced a mean zone size of 13.0 ± 6.0 mm and 16.7 ± 8.4 mm, respectively, for S. aureus and Enterobacterales by Punch Well method (p<0.002). Whereas Aloe vera gel failed to induce any zone of inhibition for all the isolates p<0.001. Mean MIC of Aloe vera leaf extract against 74 S. aureus was 94 ± 41.23 mg/ml and against 73 Enterobacterales, it was 45.6 ± 20 mg/ml p < 0.001. Mean MBC of Aloe vera leaf extract against 74 S.aureus isolates was 188 ± 82.46 mg/ml and against 73 En-terobacterales was 91.18±40 mg/ml p < 0.001. Conclusion: Aloe vera ethanol leaf extract showed a good antibacterial effect against the different strains of bacteria causing wound infection. The present article shows the possi-bility of future use of natural products for the treatment of wound infections.

Background: Dental restorative materials are recognized as artificial niches that facilitate the adherence and accumulation of oral microorganisms. To mitigate oral diseases and extend the lifespan of restorations, it is advantageous to use dental materials that exhibit low susceptibility to bacterial adhesion. Objective: To evaluate and compare bacterial adhesion on two bioactive restorative materials, a glass hybrid restorative, and an alkasite with a nanohybrid resin composite as a positive control. The secondary objectives were to compare the surface roughness (SR) of the materials and determine the correlation between the bacterial adhesion and the SR. Materials and methods: The samples consisted of 33 polished discs of each material: Group A: Tetric^® N-Ceram (nanohybrid resin composite), Group B: Equia Forte™ HT Fil (glass hybrid restorative) and Group C: Cention N^® (alkasite). Streptococcus mutans cultures were inoculated and after 24-hours of incubation, bacterial adhesion was measured by measuring optical density (OD) and number of colony forming units (CFUs). After 96-hours incubation, the bacterial cell count was determined using scanning electron microscopy (SEM). SR was assessed using surface profilometer. Results: Alkasite had significantly lower OD and CFUs (p < 0.001 and p = 0.015 respectively). According to the SEM analysis, the glass hybrid restorative had lower mean bacterial cell count with no significant difference between the groups. The nanohybrid composite had the smoothest surface that was significantly lower than the alkasite and glass hybrid restorative (p = 0.002). None of the groups demonstrated a correlation between bacterial adhesion and SR. Conclusion: Alkasite impedes bacterial adhesion better than the glass hybrid restorative and nanohybrid composite, while smoother surfaces are achieved with the nanohybrid composite.

Objectives: White spot lesions are the most common iatrogenic effect observed during orthodontic treatment. This study aimed to compare the surface characteristics and antibacterial action of uncoated and coated orthodontic brackets. Materials and methods: Sixty commercially available stainless steel brackets were coated with TiO₂ nanotubes and methacryloyloxyethylphosphorylcholine. The sample was divided into Group 1: uncoated orthodontic brackets, Group 2: Stainless steel brackets with TiO₂ nanotubes coating, Group 3: Stainless steel brackets with methacryloyloxyethylphosphorylcholine coating, and Group 4: Stainless steel brackets with TiO₂ nanotubes combined with methacryloyloxyethylphosphorylcholine coating. Surface characterization was assessed using atomic force microscopy and scanning electron microscopy. Streptococcus mutans was selected to test the antibacterial ability of the orthodontic brackets, total bacterial adhesion and bacterial viability were assessed. The brackets were subjected to scanning electron microscopy to detect the presence of biofilm. Results: The surface roughness was the greatest in Group 1 and least in Group 2 followed by Group 4 and Group 3 coated brackets. The optical density values were highest in Group 1 and lowest in Group 4. Comparison of colony counts revealed high counts in Group 1 and low counts in Group 4. A positive correlation between surface roughness and colony counts was obtained, however, was not statistically significant. Conclusions: The coated orthodontic brackets exhibited less surface roughness than the uncoated orthodontic brackets. Group 4 coated orthodontic brackets showed the best antibacterial properties. Clinical relevance: Coated orthodontic brackets prevent adhesion of streptococcus mutans and reduces plaque accumulation around the brackets thereby preventing formation of white spot lesions during orthodontic treatment.

Purpose: Nisin is a lantibiotic effective against Gram-positive microorganisms such as Streptococcus mutans. The study aimed to determine the effect of the addition of nisin to high-viscosity glass-ionomer cement (HVGIC) on its antibacterial activity, setting time, surface microhardness, and compressive strength. Methods: 1 and 3% w/w nisin were added to HVGIC before mixing. Unmodified HVGIC was the control. Agar disc diffusion, direct contact test, and scanning electron microscopy (SEM) analysis were used to evaluate antibacterial activity against S. mutans. Setting time, surface microhardness, and compressive strength were measured using Gilmore needle apparatus, digital microhardness tester, and universal testing machine, respectively. Statistical analysis included Student’s t test, one-way ANOVA with Tamhane’s post hoc test, and repeated-measures ANOVA. Results: As evidenced by the agar disc diffusion (p < 0.001), direct contact tests (p = 0.025), and SEM analysis of the S. mutans cell count and cell surface area (p = 0.049 and 0.003), 3% nisin had the strongest antibacterial activity. There was a dose-dependent increase in setting time (p = 0.005) and surface microhardness (p = 0.006), with no significant difference in compressive strength compared to control. Conclusion: The addition of 3% nisin to HVGIC enhances the antibacterial action against S. mutans and surface microhardness without adversely affecting setting time and compressive strength.

Background: With an increasing trend of pathogenic bacteria developing resistance to the existing drugs, there is a need for newer therapeutic measures. Nigella sativa seeds and oil have been used for decades as Ayurveda, Unani Tibb and other forms of traditional medicine for various disorders. Thymoquinone is one of the active components of the N. sativa seeds. Objective: The present study determines the antibacterial effect of crude methanolic extract N. sativa seeds and thymoquinone against bacteria causing wound infection. Methods: Samples obtained from cases of wound infection received at a Microbiology laboratory attached to a tertiary care hospital over a period of six months were included in the study. The antibacterial effect of crude methanolic extract of N. sativa seeds was determined by the Punch Well method. The minimum inhibitory concentration (MIC) of thymoquinone against bacteria isolated from cases of wound infection was determined by the Micro Broth Dilution technique. Results: A total of 60 isolates were collected from 60 samples of wound infection. By the Punch Well method, Staphylococcus aureus showed varying zones of inhibition whereas all gram-negative bacilli and Enterococcus faecalis did not show any zone of inhibition. Thymoquinone showed good antibacterial activity against S. aureus with MIC values ranging from 2-8μg/ml for most of the isolates. Uniformly, MIC of thymoquinone against all gram-negative bacilli and E. faecalis was >128μg/ml, p<0.001. It was found that methicillin-resistant S. aureus (MRSA) isolates showed higher MIC than methicillin sensitive S. aureus (MSSA) isolates p<0.05. Conclusions: Antibacterial activity of thymoquinone was very good against S. aureus but showed limited activity against Enterobacteriaceae members and E. faecalis isolated from patients with wound infection. Thymoquinone may be considered a potential antibacterial agent against wound infection caused by S. aureus.