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Aims@#Dental caries is a chronic infectious disease caused by Streptococcus mutans due to its ability to form biofilm. This study aims to assess the antimicrobial efficacy of Melastoma malabathricum leaf extract against S. mutans on the surface of tooth samples as a potential therapy for dental caries.@*Methodology and results@#Extraction of M. malabathricum leaves was done using acetone as the solvent and antibacterial activity of the extracts was determined by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Antibiofilm activity of M. malabathricum extract against S. mutans was determined by comparing the colony count, biofilm formation assay and morphology observation by scanning electron microscope (SEM). The MIC value of extracts was 6.25 mg/mL and MBC value was >25 mg/mL. A decrease in colony count was noted when tooth samples were incubated with M. malabathricum extract for 8 h compared to 4 h incubation. At pH 5, the formation of the colony was the least, medium at pH 8 and maximum at pH 7. A decrease in biofilm formation was observed when tooth samples were incubated with the extract for 8 h. SEM observations showed treatment with the extract caused S. mutans cell membrane to leak leading to cell morphology changes.@*Conclusion, significance and impact of study@#Acetone extract of M. malabathricum leaves showed excellent antibacterial activity against S. mutans. It has bactericidal activity with the ability to inhibit biofilm in dose-dependent manner against S. mutans. The morphological analyses suggested that the extract disrupted the cell membrane of the bacteria.
ABSTRACT
Aim@#To determine the efficacy and mode of action of hot and cold water extracts of Orthosiphon stamineus leaves against two strains of human herpes virus 1 (HHV-1) i.e. KOS-1 and acyclovir (ACV)-resistant UKM-1 (UKM-1) strains. @*Methodology and results@#Hot and cold water extracts of O. stamineus were not cytotoxic to vero cells as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) (MTT) assay with 50% cytotoxicity concentration (CC50) values of 3.4 and 3.3 mg/mL respectively. Antiviral activity was determined by plaque reduction assay in post-treatment, pre-treatment and virucidal assays followed by time-addition and time removal assay to relate with the stages during the viral infection cycle. Both extracts displayed antiviral activity against HHV-1 KOS-1 and HHV-1 UKM-1 strains with 50% effective concentration (EC50) values between 0.12-0.15 mg/mL in reducing plaque formation. The calculated selectivity indices (SI) were 23 and 28 for hot and cold water extract respectively, indicating that they have good potential as antiviral agent. The extracts were virucidal towards both HHV-1 KOS-1 and HHV-1 UKM-1 strains which may directly affects the virus structure. This is supported with the fact that exposure of the extracts inhibit viral attachment and penetration to the vero cells. In time-of addition assay, both extracts were effective during the early stage of virus infection cycle for HHV-1 KOS-1 strain which is in parallel with the results from the attachment and penetration studies. For HHV-1 UKM-1 strain, contact to the extracts at any time during post-infection inhibits virus replication and also progeny release. @*Conclusion, significance and impact of study@#Cold and hot water extracts of O. stamineus have good potential as antiviral agent against HHV-1 strain KOS-1 and more importantly against UKM-1 strain which is ACV-resistant. The extracts displayed virucidal effect and inhibition of early virus replication cycle involving viral attachment and penetration to cells.
ABSTRACT
Aims@#Phytochemical analysis showed Orthosiphon stamineus (OS) possessed bioactive compounds with antiviral properties against Herpes Simplex Virus Type 1 (HSV-1). However, there isn’t any study reported so far on OS virucidal properties towards HSV-1. Thus, this study aims to investigate virucidal mechanism of OS aqueous extract that possibly acts as a potent entry inhibitor against HSV-1 infection. @*Methodology and results@#Virucidal attachment and penetration assays were done via plaque assay to investigate the virucidal anti-HSV-1 mechanism of OS. The aqueous extract of OS leaves (OSA) was found to reduce HSV-1 plaques in virucidal assays. Inhibitory effect by OSA was observed as early as 30 min after exposing OSA to HSV-1 in a concentration-dependent manner suggesting a direct anti-HSV-1 property of OSA. Further investigation of the stages in which OSA inhibits HSV-1 shows virions treated with OSA failed to attach onto the host cell which implicated a role of OSA in blocking HSV-1 attachment to its host. OSA was also found to reduce HSV-1 plaques in penetration assay. Further evaluation using transmission electron microscopy (TEM) on OSA treated virion showed defective HSV-1 virion without envelope and the remaining capsid was altered. @*Conclusion, significance and impact of study@#These findings concluded that Orthosiphon stamineus leaves extract have virucidal activity by disintegrating HSV-1 virion structure and interfering with the attachment and penetration of the virus into the host cell. Thus, through the new mechanism against HSV-1, OS has the potential to be further developed as an anti-HSV-1 agent.
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Aims@#The aim of the study was to isolate and characterise bacteriophages specific to Pseudomonas aeruginosa carrying virulence genes. @*Methodology and results@#Four clinical strains of P. aeruginosa CL1, CL2, CL3 and CL4 were obtained from Queen Elizabeth Hospital, Kota Kinabalu, Sabah. The bacterial strains were screened for virulence genes exoS, toxA and oprI and biofilm production. Six P. aeruginosa specific bacteriophages, namely PAtk1, PAtk2, PAtk3, PAtk4, PAtk5 and PAtk6, were isolated from Tasik Kejuruteraan, Universiti Kebangsaan Malaysia. These bacteriophages were screened for lytic spectrum against P. aeruginosa and two species of Enterobacteriaceae (Escherechia coli and Salmonella Typhi). PCR results showed that all strains possessed exoS, toxA and oprI genes except CL2 that lacked exoS. Nevertheless, it was CL2 that produced the highest biofilm density. Further, based on Transmission Electron Microscopy, PAtk15 and PAtk6 were classified into the family Myoviridae and Siphoviridae, respectively. Among all six isolated phages, only PAtk4 and PAtk6 showed the broadest lytic spectrum in which lytic activity was observed against all clinical P. aeruginosa strains. @*Conclusion, significance and impact of study@#In this study we reported the isolation of six bacteriophages from Myoviridae and Siphoviridae that are specific to P. aeruginosa possessing exoS, toxA and oprI genes. Bacteriophages Patk4 and PAtk6 were able to infect all four strains of P. aeruginosa, making these phages potential agents in combating infections by the bacterium.
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Aims: This study was aimed to evaluate in vitro antiviral activity of topical formulations incorporated with a styrylpyrone derivative (SPD) against Herpes Simplex Virus type 1 (HSV-1). Methodology and results: Two types of SPD-incorporated formulations (ointment and gel) were tested for their antiviral activity against HSV-1 clinical strain using plaque reduction assay on Vero cells. The antiviral activity was determined based on the percentage of plaque reduction occurred between treatment and control (non-treated infected cells). In this study, 10% SPD-gel (SPD = 0.004 mg) and 20% SPD-ointment (SPD = 0.003 mg) showed plaque reduction percentage of 87% and 79% respectively. Further evaluation on the ointment base, gel base (formulation without SPD) demonstrated less than 10% of antiviral activity while pure SPD at 0.0025 mg showed 81% of plaque reduction. These results indicated that the antiviral activity observed in both SPD-incorporated ointment and gel was mainly due to SPD regardless of formulation components. Furthermore, the antiviral activities observed in both SPD-incorporated products were also in agreement with the antiviral activity observed in pure SPD. Conclusion, significance and impact study: SPD-incorporated products retained the antiviral activity and can further be tested in animal model.