Antimicrobial Efficacy of Salvadora persica Extracts on a Monospecies Biofilm on Orthodontic Brackets In Vitro.

PURPOSE: The oral cavity is a rich ecosystem with a plethora of microorganisms, and different components of fixed orthodontic appliances may contribute to a shift in the balance of oral ecology. The purpose of this study was to investigate the antimicrobial potential of hexane and ethanol extracts of Salvadora persica on a monospecies biofilm model established on orthodontic brackets in vitro. MATERIALS AND METHODS: Streptococcus mutans biofilm was formed on mini diamond orthodontic brackets following three days of anaerobic incubation at 37˚C. The bacterial cell viability of this biofilm was measured after their exposure to saline, hexane extract of S. persica, ethanol extract of S. persica and 0.2% chlorhexidine using 3-(4, 5-dimethylthiazol- 2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2H-tetrazolium (MTS) assay. On half of the brackets, the colony forming units (CFU) were counted. Both experiments were performed in triplicate. RESULTS: The absorbance values obtained from the MTS reduction assay after exposure to the different test agents showed a decline in the bacterial cell viability of the S. mutans biofilm as follows: chlorhexidine (+)0.05). The CFU counts of S. mutans obtained from chlorhexidine exposure were lower than from hexane and ethanol extracts. CONCLUSION: S. persica extracts were found to have antimicrobial effects on S. mutans biofilm established in vitro on orthodontic brackets suggestive of its potential use as an oral antimicrobial agent for orthodontic patients.

Assessment of the Antimicrobial Activity of Few Saudi Arabian Snake Venoms.

BACKGROUND: Venoms of two cobras, four vipers, a standard antibiotic and an antimycotic, were evaluated comparatively, as antimicrobials. METHODS: Six venom concentrations and three of the standard antibiotic and the antimycotic were run in micro-dilution and diffusion plates against the microorganisms. RESULTS: Echis pyramidum, Echis coloratus and Cerastes cerastes gasperettii highest venom concentrations gave significant growth inhibition zones (GIZ) with respect to a negative control, except Bitis arietans, whose concentrations were significant. The cobra Walterinnesia aegyptia had significant venom concentrations more than Naja haje arabica. The Staphylococcus aureus Methicillin Resistant (MRSA) bacterium was the most susceptible, with a highly (P < 0.001) significant GIZ mean difference followed by the Gram positive Staphylococcus aureus, (P < 0.001), Escherichia coli (P < 0.001), Enterococcus faecalis (P < 0.001) and Pseudomonas aeruginosa which, had the least significance (P < 0.05). The fungus Candida albicans was resistant to both viper and cobra venoms (P > 0.05). The antibiotic Vancomycin was more effective than snake venoms though, they were more efficient in inhibiting growth of the resistant Pseudomonas aeruginosa. This antibiotic was also inactive against the fungus, whilst its specific antifungal Fungizone was highly efficient with no antibacterial activity. CONCLUSIONS: These findings showed that snake venoms had antibacterial activity comparable to antibiotics, with a directly proportional relationship of venom concentration and GIZ, though, they were more efficient in combatting resistant types of bacteria. Both venoms and the standard antibiotic, showed no antifungal benefits.

Antimicrobial activity of aqueous and organic extracts of a Saudi medicinal plant: Rumex nervosus.

OBJECTIVE: The antimicrobial effect of aerial part of Rumex nervosus obtained from the Southern region of Saudi Arabia was evaluated on bacterial strains Staphylococcus aureus, methicillin resistant S. aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas Aeruginosa, and fungal strain Candida albicans. MATERIALS AND METHODS: The solvents used for the extraction were aqueous, hexane, and methanol. The in vitro antimicrobial activity was performed by agar diffusion and disk diffusion methods and the confirmation of this activity was done by the enumeration of colony forming units (CFU). RESULTS: The aqueous extract showed the growth inhibitory effect on Gram-positive bacteria while the Gram-negative P. aeruginosa was the most sensitive microorganism as determined by the agar diffusion technique. Surprisingly, the extract showed little antibacterial activity on other Gram-negative bacteria (E. coli) by this technique. Ethanolic extract was also found to be inhibitory to the growth of microorganisms. Hexane extract was relatively low in antimicrobial activity on Gram-negative E. coli and P. aeruginosa, while both the organic extracts were inhibitory to the growth of the fungus, C. albicans. Hexane gave no conclusive results with agar or disk diffusion methods, but showed the microbial growth inhibition in CFU enumeration. The antibacterial activity of active extracts was compared with vancomycin while antifungal activity of was compared with amphotericin B. CONCLUSION: The results obtained in the present study suggest that R. nervosus showed a marked antimicrobial activity with the test organisms.

Cytotoxicity of carbon nanotube variants: a comparative in vitro exposure study with A549 epithelial and J774 macrophage cells.

While production of engineered carbon nanotubes (CNTs) has escalated in recent years, knowledge of risk associated with exposure to these materials remains unclear. We report on the cytotoxicity of four CNT variants in human lung epithelial cells (A549) and murine macrophages (J774). Morphology, metal content, aggregation/agglomeration state, pore volume, surface area and modifications were determined for the pristine and oxidized single-walled (SW) and multi-walled (MW) CNTs. Cytotoxicity was evaluated by cellular ATP content, BrdU incorporation, lactate dehydrogenase (LDH) release, and CellTiter-Blue (CTB) reduction assays. All CNTs were more cytotoxic than respirable TiO2 and SiO2 reference particles. Oxidation of CNTs removed most metallic impurities but introduced surface polar functionalities. Although slopes of fold changes for cytotoxicity endpoints were steeper with J774 compared to A549 cells, CNT cytotoxicity ranking in both cell types was assay-dependent. Based on CTB reduction and BrdU incorporation, the cytotoxicity of the polar oxidized CNTs was higher compared to the pristine CNTs. In contrast, pristine CNTs were more cytotoxic than oxidized CNTs when assessed for cellular ATP and LDH. Correlation analyses between CNTs' physico-chemical properties and average relative potency revealed the impact of metal content and surface area on the potency values estimated using ATP and LDH assays, while surface polarity affected the potency values estimated from CTB and BrdU assays. We show that in order to reliably estimate the risk posed by these materials, in vitro toxicity assessment of CNTs should be conducted with well characterized materials, in multiple cellular models using several cytotoxicity assays that report on distinct cellular processes.

Antimicrobial susceptibility patterns of multidrug-resistant Pseudomonas aeruginosa and Acinetobacter baumannii against carbapenems, colistin, and tigecycline.

OBJECTIVE: To examine susceptibility of Pseudomonas aeruginosa (P. aeruginosa) and Acinetobacter baumannii (A. baumannii ) against carbapenems along with colistin and tigecycline as alternative therapeutic options. METHODS: A total of 117 strains of multidrug-resistant (MDR) non-fermenting Gram negative bacteria isolated from non-duplicate samples were collected consecutively. We included one sample from each patient (84 isolates of A. baumannii and 33 isolates of P. aeruginosa isolated from patients seen at King Khalid University Hospital, Riyadh, Saudi Arabia, from June to December 2010). Isolates were identified by the MicroScan WalkAway 96 Plus system. The minimum inhibitory concentrations (MICs) were determined by E-test following the Clinical and Laboratory Standards Institute breakpoint recommendations. RESULTS: Most A. baumannii strains were resistant to imipenem (90.5%), meropenem (90.5%), and doripenem (77.4%). Whereas, a higher percentage of P. aeruginosa was resistant to imipenem (90.9%), and meropenem (81.8%), only 39.4% were resistant to doripenem. Colistin had excellent activity against both A. baumannii (100%) and P. aeruginosa (93.9%), while 89.3% of A. baumannii strains were susceptible to tigecycline. CONCLUSION: Among the carbapenems, doripenem was found to be the most potent antimicrobial agent against P. aeruginosa, whereas colistin proved to be an effective alternative antimicrobial agent for treatment of A. baumannii or P. aeruginosa. Tigecycline remains the best therapeutic option for MDR A. baumannii.

Inhibition of growth of Leishmania donovani promastigotes by newly synthesized 1,3,4-thiadiazole analogs.

Leishmania donovani, the causative agent of visceral leishmaniasis, is transmitted by sand flies and replicates intracellularly in their mammalian host cells. The emergence of drug-resistant strains has hampered efforts to control the spread of the disease worldwide. Forty-four 1,3,4-thiadiazole derivatives and related compounds were tested in vitro for possible anti-leishmanial activity against the promastigotes of L. donovani. Micromolar concentrations of these agents were used to study the inhibition of multiplication of L. donovani promastigotes. Seven compounds were identified with potential antigrowth agents of the parasite. Compound 4a was the most active at 50 µM followed by compound 3a. These compounds could prove useful as a future alternative for the control of visceral leishmaniasis.

Effect of pyrazoloquinoline derivatives on the growth of Leishmania donovani promastigotes.

A screening study was conducted to examine the effect of a series of synthesized pyrazoloquinoline derivatives on the growth of Leishmania donovani promastigotes. Sixteen compounds were tested, ten of which showed an inhibitory effect on the growth of promastigotes. Compound 1 demonstrated potent antileishmanial activity, followed by compounds 3 and 7. Some compounds showed less significant activities, while others exhibited little or no activity. Some of these compounds may be potential candidates for future treatment of leishmaniasis.

Benign tumors from the human nervous system express high levels of survivin and are resistant to spontaneous and radiation-induced apoptosis.

Survivin, an inhibitor of apoptosis, is over-expressed in foetal tissues and human cancers, but it is almost undetectable in normal tissues. Here we have assessed the level of the survivin protein in some benign tumors of the nervous system: meningioma, schwannoma, low-grade ependymoma, pilocytic astrocytoma and pituitary adenoma. Using immuno-blot analysis we present evidence that these low-grade tumors are positive for survivin expression. In agreement, flow cytometrical analysis showed that both spontaneous and radiation-induced apoptosis levels are very low in these neoplasms. Using host cell reactivation assay we have also shown that these tumor cells are proficient in the repair of gamma-ray-induced DNA damage. However, they are deficient in the removal of ultraviolet (UV) light-induced DNA photolesions, especially the shwannoma- and the pituitary adenoma-derived cells. These results suggest that survivin overexpression may be an early event in the stepwise tumoregenesis and hence could be responsible for the onset as well as the growth advantage during tumoregenic progression of malignant as well as benign neoplasms.

Evaluation of some pyrazoloquinolines as inhibitors of herpes simplex virus type 1 replication.

Three structurally related aminopyrazoloquinoline derivatives were evaluated for their antiviral activity against Herpes Simplex virus type 1. These compounds were examined for their in vitro antiviral activity by two different bioassays, namely; crystal violet staining and tetrazolium dye (MTS) measurement. The antiviral role of these compounds was confirmed by enumerating the infectious particles with plaque assay. The acute toxicity values of the biologically active compounds were determined prior to their screening as antiviral agents.

Defective repair of UV-induced DNA damage in cultured primary skin fibroblasts from Saudi thyroid cancer patients.

This study was conducted to examine the sensitivity of primary skin fibroblasts from Saudi thyroid cancer (TC) patients to ultraviolet (UV) irradiation. Cell survival was studied by a colony forming assay and DNA repair defects with a host cell reactivation (HCR) assay using UV-irradiated Herpes Simplex Virus (HSV). In addition, p53 gene expression was examined in the same TC cells exhibiting enhanced radiosensitivity. Skin fibroblasts from TC patients (n=4) showed significantly enhanced sensitivity to UV radiation. The average UV dose to reduce survival to 37% of the initial survival (D(37)) value (in Jm(-2)) for fibroblasts from TC patients was 4.6 (3.7-5.6) compared to 7.3 (6.3-8.3) for healthy individuals (n=3). UV-sensitive xeroderma pigmentosum (XP) cells, which were used as positive control, were found to be extremely sensitive with a D(37) value of 0.6 Jm(-2). In a host cell reactivation assay, UV-irradiated HSV was tested for its plaque-forming ability (PFA), by plating infected fibroblasts from TC patients (used as host cells) on African Green Monkey (Vero) kidney cells to form plaques. A significant reduction in the PFA of the UV-irradiated virus (about three fold) on TC cells compared to fibroblasts from the healthy subjects was seen, suggesting a DNA-repair deficiency in the primary fibroblasts of the TC patients. Furthermore, no significant accumulation in radiation-induced p53 expression was observed in cells from the TC patients. Our results, based on a relatively small group of subjects, indicate that Saudi TC patients primary fibroblasts (non-cancerous in nature) may be carriers of cancer-susceptible gene(s) arising from defective DNA repair/processing. These results warrant a larger study to investigate the role of UV-induced bulky DNA damage in thyroid cancer susceptibility.

Synthesis of aldehydo-sugar derivatives of pyrazoloquinoline as inhibitors of herpes simplex virus type 1 replication.

Synthesis of a novel series of structurally related pyrazoloquinoline nucleosides is described. All the newly synthesized compounds were examined for their in vitro antiviral activity against herpes simplex type-1 as shown by two different bioassays, namely; crystal violet staining or the MTS tetrazolium dye measurement. The acute toxicity (LD50) values of the biologically active compounds were determined.

RNase L mediates transient control of the interferon response through modulation of the double-stranded RNA-dependent protein kinase PKR.

The transient control of diverse biological responses that occurs in response to varied forms of stress is often a highly regulated process. During the interferon (IFN) response, translational repression due to phosphorylation of eukaryotic initiation factor 2alpha, eIF2alpha, by the double-stranded RNA-dependent protein kinase, PKR, constitutes a means of inhibiting viral replication. Here we show that the transient nature of the IFN response against acute viral infections is regulated, at least in part, by RNase L. During the IFN antiviral response in RNase L-null cells, PKR mRNA stability was enhanced, PKR induction was increased, and the phosphorylated form of eIF2alpha appeared with extended kinetics compared with similarly treated wild type cells. An enhanced IFN response in RNase L-null cells was also demonstrated by monitoring inhibition of viral protein synthesis. Furthermore, ectopic expression of RNase L from a plasmid vector prevented the IFN induction of PKR. These results suggest a role for RNase L in the transient control of the IFN response and possibly of other cytokine and stress responses.