Mean Diameter Of Inhibition Zone Research Articles

Antimicrobial activity of aqueous and methanol extract of naturally growing and cultivated Aloe turkanensis

The aim of the study was to determine the antibacterial properties of aqueous and methanol extracts of naturally occurring and cultivated Aloe turkanensis. The plant is widely used as a traditional herb by communities in Turkana County, Kenya. However its efficacy has not been established. Aqueous and methanol extract of a naturally occurring whole Aloe turkanensis and cultivated one was obtained. The extracts were tested for in-vitro activity against 4 standard bacterial cultures and a fungal clinical isolate. Benzyl penicillin, Gentamycin and Amphotericin B were used as positive controls. Efficacy data analysis showed that methanol extracts of naturally growing plant inhibited the growth of B. cereus (100 mg/ml), S. aureus (100 mg/ml), and P. aeroginosa (200 mg/ml) with mean diameters of inhibition zones for S. aureus and B. cereus being 18.5±0.7 mm and 16.5±0.7 mm, respectively. Aqueous extract of the plant inhibited the growth of B. cereus and S. aureus at a Minimum Inhibitory Concentration of 200 mg/ml and 50 mg/ml respectively with mean diameter of inhibition zones for S. aureus and B. cereus being 19.75±1.0 mm and 11.5±0.0 mm respectively. Methanol extracts of cultivated A. turkanensis inhibited the growth B. cereus (100 mg/ml), S. aureus (50 mg/ml), E. coli (400 mg/ml) and P. aeroginosa (200 mg/ml) with mean diameters of inhibition zones for S. aureus and B. cereus being 18.5±0.7 mm and 11.5±0.0 mm respectively. There was a significant difference in antibacterial activity between the two plant ecotypes (p<0.05).

An in vitro comparison of the antibacterial efficacy of triphala with different concentrations of sodium hypochlorite.

The antimicrobial efficacy of root canal irrigant plays an important role in increasing the success of root canal treatment (RCT). The aim of the present experimental study was to compare the antimicrobial activity of Triphala (a plant-derived solution) with 0.5, 1, 2.5 and 5% concentrations of sodium hypochlorite (NaOCl), against Enterococcus faecalis (E. faecalis). Two hundred plates of cultured E. faecalis, were divided into 5 experimental groups (n=38) and two positive and negative control groups. The antimicrobial activity of the test solutions was determined by measuring the zone of inhibition in the culture media. The mean diameter of inhibited zones between the study groups was compared using the Kruskal-Wallis test and the Mann-Whitney U test was used for the two-by-two comparison of the groups with the level of significance set at 0.05. The Kruskal-Wallis test showed significant differences between the study groups (P<0.05). According to the Mann-Whitney U test the mean diameter of inhibition zones in Triphala group was significantly higher compared to 0.5 and 1% NaOCl (P<0.05). In this study, Triphala exhibited better antimicrobial activity against E. faecalis compared to 0.5 and 1% NaOCl (P<0.05).

An in vitro study on the anti-microbial effi cacy of ten herbal extracts on primary plaque colonizers

Introduction: To assess and compare the anti-microbial efficacy of ten herbal extracts against primary plaque colonizers. Materials and Methods: The branches of 10 plants with ethno-pharmacological background were collected and healthy leaves separated to prepare the fine powder. The extraction procedure was carried out by cold infusion method using ethanol. The working concentration of the extract (100 mg/ml) was prepared by mixing dried leaf extract with dimethyl sulfoxide (DMSO). 0.2% chlorhexidine and DMSO were used as positive and negative controls, respectively. Agar well diffusion method was used for anti-microbial efficacy testing. The statistical analysis was done using SPSS 16. The mean diameter of inhibition zone between the categories was compared using one-way analysis of variance and Tukey’s post-hoc test. Results: The highest mean diameter of inhibition zone against Streptococcus mutans was produced by Acacia nilotica followed by Psidium guajava, Eucalyptus hybrid and Murraya koenigii L.S extracts in the descending order. The highest mean inhibition zone against Streptococcus sanguinis was produced by chlorhexidine followed by A. nilotica, Eucalyptus, P. guajava, and M. koenigii L.S extracts in the descending order. The highest mean inhibition zone against Streptococcus salivarius was produced by P. guajava, followed by chlorhexidine, A. nilotica, Eucalyptus, M. koenigii L.S and Hibiscus sabdariffa L extracts in the descending order. Conclusion: P. guajava, Eucalyptus, A. nilotica, M. koenigii L.S and H. sabdariffa L have the potential to inhibit primary plaque colonizers, and they could be used as anti-plaque agents. Key words: Acacia nilotica, Eucalyptus hybrid, Murraya koenigii L. sprengel, Psidium guajava, Streptococcus mutans, Streptococcus salivarius, Streptococcus sanguis.

Antimicrobial efficacy of aqueous and ethanolic extracts of Triphala on primary plaque colonizers: An in-vitro study

Objective: To assess the antimicrobial efficacy of the aqueous and ethanolic extracts of Triphala at various concentrations against primary plaque colonizers. Materials and methods: Preparation of the herbal extracts for this in vitro study was done using cold infusion method. Ethanol and Millipore water were used as solvents for extraction. The stock solution was prepared by adding 1000 mg of dried extract in one ml of dimethyl sulfoxide (DMSO). The stock solution was further diluted to obtain 6.25%, 12.5%, 25% and 50% concentrations of the extract. The antimicrobial efficacy testing of Triphala extracts against these bacteria was done by agar well diffusion method. 0.2% chlorhexidine was used as positive control while DMSO acted as negative control. One way Analysis of Variance and independent sample t-test were used for comparing mean diameter of inhibition zones. Results: All the concentrations of ethanolic and aqueous extracts of Triphala inhibited the growth of S. mutans, S. sanguis and S. salivarius. In general, the efficacy increased with increasing concentration with maximum inhibition at 50% concentration. There was no statistically significant difference in the mean diameter of inhibition zone between the ethanolic and aqueous extracts of triphala against S. mutans. Conclusion: Both aqueous and ethanolic extracts of Triphala have the potential to be used antiplaque agents. Key words: Antimicrobial efficacy, Triphala, Minimum Inhibitory Concentration (MIC), Dental caries, S. mutans, periodontal diseases.

Antimicrobial efficacy of the combinations of Acacia nilotica, Murraya koenigii L. sprengel, Eucalyptus hybrid and Psidium guajava on primary plaque colonizers.

Background:There is an urgent need for innovative strategies to combat the two most common dental diseases of mankind namely dental caries and periodontitis.Objective:The aim was to assess the antimicrobial efficacy of the double combinations of Acacia nilotica (AN), Murraya koenigii L. Sprengel (MKL), Eucalyptus hybrid and Psidium guajava on primary plaque colonizers.Materials and Methods:The plant extracts of AN, MKL. Sprengel, Eucalyptus hybrid and P. guajava were prepared using Soxhlet apparatus. The stock solutions of individual plant extracts (100 mg/ml) were prepared. Equal quantities of stock solutions were mixed to obtain six double combinations of herbal extracts. The antimicrobial efficacy testing was done against three primary plaque colonizers using agar well-diffusion method. 0.2% chlorhexidine and dimethyl sulfoxide were used as positive and as negative controls. The mean inhibition zone between the categories was compared using one-way Analysis of Variance and Tukey's post hoc test.Results:The combination of AN and P. guajava produced the highest mean diameter of inhibition zone (21.08 mm ± 2.11) against Streptococcus mutans. The chlorhexidine produced the least inhibition zone against S. mutans (14.50 ± 2.07). The combination of AN and P. guajava produced the maximum antimicrobial efficacy against Streptococcus sanguis (19.67 ± 1.03) and Streptococcus salivarius (20.33 ± 1.86).Conclusion:All the combinations of plant extracts have the potential to be used as antiplaque and anticaries agents. The combinations of herbal extracts offer enhanced antimicrobial efficacy due to the synergistic effects besides slowing the development of resistance.

Synergy of antibacterial and antioxidant activities from crude extracts and peptides of selected plant mixture.

BackgroundA plant mixture containing indigenous Australian plants was examined for synergistic antimicrobial activity using selected test microorganisms. This study aims to investigate antibacterial activities, antioxidant potential and the content of phenolic compounds in aqueous, ethanolic and peptide extracts of plant mixture.MethodsWell diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays were used to test antibacterial activity against four pathogenic bacteria namely Staphylococcus aureus, Escherichia coli, Bacillus cereus, and Pseudomonas aeruginosa. DPPH (2, 2-diphenyl-1- picrylhydrazyl) and superoxide dismutase (SOD) assays were used to evaluate antioxidant activity. HPLC and gel filtration were used for purification of the peptides. Scanning electron microscope was applied to investigate the mode of attachment of the peptides on target microbial membranes.ResultsAqueous extraction of the mixture showed no inhibition zones against all the test bacteria. Mean diameter of inhibition zones for ethanol extraction of this mixture attained 8.33 mm, 7.33 mm, and 6.33 mm against S. aureus at corresponding concentrations of 500, 250 and 125 mg/ml while E .coli showed inhibition zones of 9.33 mm, 8.00 mm and 6.66 mm at the same concentrations. B. cereus exhibited inhibition zones of 11.33 mm, 10.33 mm and 10.00 mm at concentrations of 500, 250 and 125 mg/ml respectively. The peptide extract demonstrated antibacterial activity against S. aureus, E. coli and B. cereus. The MIC and MBC values for ethanol extracts were determined at 125 mg/ml concentration against S. aureus and E. coli and B. cereus value was 31.5 mg/ml. MIC and MBC values showed that the peptide extract was significantly effective at low concentration of the Australian plant mixture (APM). Phenolic compounds were detected in hot aqueous and ethanolic extracts of the plant mixture. Hot aqueous, ethanol and peptides extracts also exhibited antioxidant activities.ConclusionsIt was concluded that APM possessed good antibacterial and antioxidant activities following extraction with different solvents. The results suggest that APM provide a new source with antibacterial agents and antioxidant activity for nutraceutical or medical applications.

Antimicrobial Activity of Xerophytic Plant ( Cotula cinerea Delile ) Extracts against Some Pathogenic Bacteria and Fungi

In the present investigation, an Algerian commonly available plant namely Cotula cinerea, found throughout sandy desert grounds, was screening for antimicrobial activity against five different human pathogenic microbes namely, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli and Candida albicans. The antimicrobial activity was evaluated using the agar disc diffusion method. Aerial parts of C. cinerea were subjected to extraction using four solvents of different polarity (70% ethanol, n-butanol, ethyl acetate and petroleum ether). Petroleum ether and n-butanol extracts had the most effective antimicrobial activity with Gram-negative K. pneumoniae demonstrating the highest susceptibility. Linear regression analysis was performed to find correlations between extract concentrations and inhibition activity. Results showed a significant increase in mean diameter of inhibition zone with increasing extract concentrations of all solvents except n-butanol. Two-way ANOVA test was used to compare the effect of C. cinerea extracts on the antimicrobial properties. All plant extracts have shown significant differences in their actions as antimicrobial agents. Indeed, the n-butanol extract at a low concentration of 0.25 mg mL -1 indicated a potent antimicrobial

English

The 80% ethanol extracts from 20 Chinese herbal medicines collected in Yunnan Province, China, were screened for antibacterial activity against Staphylococcus aureus (SA), methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli (EC) and Pseudomonas aeruginosa (PA), including antifugal activity against Candida albicans (CA) by the agar hole diffusion test. The extracts were prepared through macerating at room temperature and hot refluxing procedures. 19 of the 20 extracts showed effects with different potency and their inhibition zone diameters (IZD) ranged from 9 to 27 mm. The extracts from Psychotria henryi Levl and Marsdenia tinctoria R. Br. (maceration and reflux extraction) were the most active against both SA and MRSA, with mean IZDs = 19.7 to 22.0 mm. The anti-SA and MRSA active extracts were further determined for minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) by serial dilution with a standard broth microdilution method. 12 extracts showed effects on both SA and MRSA strains with MICs/MBCs ranges among 32 to ≥ 1024 / 64 to ≥ 1024 mg/L, respectively. P. henryi, M. tinctoria and Sapium baccatum Roxb also showed inhibition against EC, PA and CA strains, and displayed a broad spectrum of antimicrobial activities. Key words: Chinese herbal, methicillin-resistant Staphylococcus aureus (MRSA), minimum inhibitory concentrations (MIC).

English

BACKGROUND: medicinal plants are rich in a numerous variety of secondary metabolites of antimicrobial properties. Psidium guajava is one of the parts in folk medicine that has been used for the management of various disease conditions and is believed to be active. As a consequence of the intense fight against infections, bacteria have evolved through numerous defenses against antimicrobial agents. OBJECTIVE: to determine the inhibitory effect of P guajava Linn. stem bark extracts on multidrug resistant methicillin-resistant Staphylococcus aureus’isolates. MATERIALS AND METHODS: Stock cultures of 51 Staphylococcus aureus’isolated from healthy individuals maintained on nutrient agar slants at 4°C were used for this study. The disc diffusion method was used to determine the resistance of the Staphylococcus aureus isolates to methicillin (oxacillin) and to other conventional antibiotic susceptibility discs using standard concentration. The plant materials were extracted and phytochemicals quantified using standard techniques. The agar well diffusion procedure was used for the assessment of the sensitivity of the extracts. RESULTS: nine isolates were resistant to at least 4 of the antibiotics used. The mean inhibition zone diameter (IZD) of the extracts ranged from 10-16 mm with ethanolic extracts exhibiting higher activities. Five isolates showed complete resistance to Psidium guajava extracts. Inhibitory activities of both water and ethanolic extracts were distributed across 4 isolates with organism E14 showing maximum susceptibility profile. The phytochemicals estimated in mg/g dry body weight included: total phenol (111.86±0.47), tannin (141.92±0.51), flavonoids (3.37±0.04), vitamin C (1.67±0.03), saponin (285.76±0.81), and alkaloid (111.065±0.38). The extracts of Psidium guajava stem bark though showed high phytochemical contents have relatively low inhibitory activity on the multidrug resistant (MDR) community acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) isolates. CONCLUSION: the results of this study demand the introduction of antimicrobials with novel modes of action.

Study of antibacterial activity of selected Iranian plant extracts on Helicobacter pylori

Helicobacter pylori is a major contributor to chronic gastritis, peptic, duodenal ulcers, and is associated with distal adenocarcinoma. Increasing resistance of H. pylori to common antibiotics is becoming an issue and finding new treatments are crucial. Aqueous and ethanolic extracts of Glycyrrhiza glabra, Filipendula ulmaria, Argentina anserine, Crataegus douglasii, Rubus fruticosus were tested, by agar diffusion and agar dilution method, against H. pylori clinical isolates. Among the aqueous extracts studied, G. glabra extract had the highest antibacterial effect on H. pylori (mean diameter of inhibition zone 14.7 mm) followed by Filipendula ulmaria, Rubus fruticosus, Argentina anserine, and Crataegus douglasii. Among the ethanolic extracts, Glycyrrhiza glabra extract was the most effective one (mean diameter of inhibition zone 9.9 mm), followed by Filipendula ulmaria, Argentina anserine, Rubus fruticosus, and Crataegus douglasii. Given the high levels of antibacterial activities of aqueous and ethanolic extracts of Glycyrrhiza glabra and Filipendula ulmaria, the next step is to identify the antimicrobial constituents of these plants.

Antibacterial activity of Ampicillin trihydrate formulated in Aluminium-Magnesium Silicate, against &amp;lt;i&amp;gt;Salmonella gallinarum&amp;lt;/i&amp;gt;

To test if stabilizing Ampicillin trihydrate (AT) with Aluminium-Magnesium Silicate (AMS) can enhance its antibacterial activities, different concentrations of AT solution and of a formulation of AT in the AMS, were made and used for sensitivity test on Salmonella gallinarum cultures. Also, S. gallinarum-infected chicks were treated with; 10 mg/Kg (AT), 10 mg/Kg (AT in AMS), 7.5 mg/Kg (AT), 7.5 mg/Kg (AT in AMS). Mean diameter of inhibition zone, 28.39 ± 2.07 mm produced by AT did not vary significantly (P > 0.05) from 26.36 ± 2.05 mm produced by AT in AMS. However, mean Salmonella gallinarum culture forming units per ml of bile, 17.6 ± 11 × 105of the untreated chicks and 3.4 ± 0.81 × 105(80.58% reduction), 2.4 ± 0.67 × 105(85.70% reduction), 5.4 ± 1.93 × 105(69.20% reduction ) and 0.38 ± 0.13 × 105(97.80% reduction ) of the respective treated groups, showed AMS significantly (P S. gallinarum infection, in vivo.

Screening and Isolation of Associated Bioactive Microorganisms from Fasciospongia cavernosa from of Visakhapatnam Coast, Bay of Bengal

Nature, especially the marine environment, provides the most effective drugs used in human therapy. Among the metazoans, the marine sponges produce the most potent and highly selective bioactive secondary metabolites. These animals (or their associated symbiotic microorganisms) synthesize secondary metabolites whose activity and selectivity has developed during their long evolutionary history. During the course of exploitation of these resources two marine sponges, Fasciospongia cavernosa doc var.brown (dark brown) Fasciospongia cavernosa doc var.yellow (yellow) collected from the visakhapatnam coast of Bay of Bengal were investigated in order to assess the potential of these microorganisms for the production of antimicrobial compounds. The aqueous and organic extracts of both the sponges showed broad spectrum antibiotic activity. In this study a total of 178 microorganisms were isolated from different parts of two sponges and most of them from middle part of the sponge. The isolates were investigated in order to assess the potential of these microorganisms for the production of antimicrobial compounds. Testing for antimicrobial activities were performed against Gram‐positive (Staphylococcus aureus, Bacillus subtilis, Bacillus cereus) Gram‐negative bacteria (Pseudomonas aeruginosa, Escherichia coli, Proteus vulgaris), fungi (Candida albicans, Aspergillus niger) and 10 pathogenic organisms. Resulting mean diameter of inhibition zones revealed isolates B4 &amp; B6 were the most potent of all the isolates. The present study has revealed the presence of high numbers of diverse culturable microorganisms associated with the marine sponges from Visakhapatnam Coast of Bay of Bengal as well as their potential to produce bioactive metabolites.

Improving the Antibacterial Property of Porcine Small Intestinal Submucosa by Nano-Silver Supplementation

We hypothesize that introduction of nano-silver particles to porcine-derived small intestinal submucosa (NS-PSIS) would lead to significant enhancement in antibacterial property in repairing contaminated abdominal defect. Porcine-derived small intestinal submucosa (PSIS) is an acellular and xenogenic biological material intensively used in repairing and regenerating wounded and dysfunctional tissues. Surgical site infection (SSI) remains so far a serious problem and major challenge, particularly in contaminated tissue-deficient repairing. Self-assembly was used to fabricate NS-PSIS. The antibacterial property was evaluated in vitro and in vivo by means of repairing full-thickness contaminated abdominal defect in rats. The native PSIS and polypropylene-oxidized regenerated cellulose were served as controls. In addition, changes in biomechanical resistance, morphology and immunohistochemistry for inflammatory reaction and neovasculation in the repaired abdominal wall were analyzed. Biosafety was investigated by pyrogen test, skin irritation test and silver measurement in vivo. NS-PSIS exhibited strong antibacterial activity against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa on agar diffusion, with mean diameters of inhibition zone ranging from 11.9 to 23.5 mm. There were significantly lower SSI incidence and a tendency of better abdominal wall resistance in the NS-PSIS group as compared with the PSIS or polypropylene-oxidized regenerated cellulose group after repairing contaminated abdominal defect in rats. Nano-silver modified PSIS did not change the native PSIS property in the tissue recolonization, remodeling and neovascularization. NS-PSIS was not pyrogenic or skin irritated, without silver residual in vivo after repairing contaminated abdominal defect. Nano-silver particles to PSIS lead to significant enhancements in antibacterial property in vitro and in vivo without decreasing its biomechanical resistance and biocompatibility. This study provides proof of concept for the use of nano-silver modified naturally derived PSIS as an ideal scaffold for SSI prevention in the contaminated tissue-deficient repair.

A Comparison of the Antifungal Activity of Herbal Toothpastes against Other Brands of Toothpastes on Clinical Isolates of Candida albicans and Candida dubliniensis

Objectives: To evaluate the anti-Candida activity on Candida albicans and Candida dubliniensis species of 2 herbal and 7 other brands of toothpastes commonly used in Kuwait. Materials and Methods: Antifungal activity was determined by agar diffusion test on 65 isolates of C. albicans and 21 isolates of C. dubliniensis for each toothpaste. A uniform quantity of toothpaste was filled into wells punched into Sabouraud dextrose agar medium plates inoculated with the test isolates, incubated at 37°C; inhibition zone diameters were read after 24 h. Results: The mean inhibition zone diameters ranged between 12 and 23 mm for C. albicans and between 12 and 27 mm for C. dubliniensis. A herbal toothpaste brand manufactured in the Middle Eastern region (United Arab Emirates) consisting of many herbal ingredients compared to other brands was found to be the most active (p < 0.001) against both Candida species tested, which also demonstrated higher inhibitory activity against C. dubliniensis isolates compared to C. albicans.Conclusions: The herbal toothpaste brand presented significant anticandidal activity over conventional toothpastes and may be useful in reducing the pathogenic potential of Candida species.

Anti fungal activity of shallot, Allium ascalonicum Linn. (Liliaceae), in vitro

The aim of the present study was to investigate anti fungal activities of the fresh extract of Allium ascalonicum Linn. (Liliaceae) against clinically important yeast, dermatophytes and some saprophytic fungi in vitro. The anti fungal effects of fresh crude juice of shallot were determined against 11 isolates of Candida albicans, three species of dermatophytes (Microsporum gypseum, Trichophytonmentagrophytes and Epidermophyton floccosum) and Syncephalastrum,Aspergillus niger, Penicillium sp., Paecilomyces sp., Scopulariopsis sp.,Cladosporium sp., Alternaria sp., Drechslera sp. by agar well diffusion method.Minimal inhibitory concentration (MIC) of the fresh extract of A. ascalonicum was 0.25% for most tested fungi; however extract show remarkable activity against saprophytic fungi followed by Candida species and dermatophytes. It is concluded that fresh extract of A. ascalonicum has more anti-saprophytes effect at 0.25% with a mean diameter of inhibition zone 21.83 mm. Key words: Candida albicans, saprophytic fungi, dermatophyte, Allium ascalonicum, anti fungal.

Cryptococcus neoformans serotype A and Cryptococcus gattii serotype B isolates differ in their susceptibilities to fluconazole and voriconazole

This study presents antifungal susceptibility data for environmental isolates of Cryptococcus neoformans serotype A ( n = 32) and Cryptococcus gattii serotype B ( n = 18) to fluconazole and voriconazole employing disc diffusion and Etest methods. The disc diffusion test was performed on Mueller–Hinton agar as recommended by the Clinical and Laboratory Standards Institute (CLSI). For comparison, the disc diffusion test and Etest were also performed on RPMI-1640 agar supplemented with 2% glucose. The plates were incubated at 35 °C and read after 48 h. Comparison of geometric mean inhibition zone diameters revealed that C. gattii isolates were significantly less susceptible than C. neoformans isolates to fluconazole ( P = 0.001) and voriconazole ( P < 0.0001). Similar results were obtained on RPMI agar by disc diffusion test and Etest, showing significantly reduced susceptibility for C. gattii isolate s. Notwithstanding differences in the susceptibilities of the two species to fluconazole and voriconazole, they appeared susceptible according to the CLSI breakpoints recommended for some Candida spp. To what extent these differences in the susceptibilities of C. neoformans and C. gattii impact on the therapeutic management of cryptococcosis is unclear, although some studies have reported less favourable response in cases caused by the latter species.

Screening of Antibiotic-Producing Actinomycetes from Marine, Brackish and Terrestrial Sediments of Samal Island, Philippines

This study screened actinomycetes isolated from marine, brackish and terrestrial sediments of San Isidro, Babak District, Island Garden City of Samal, Davao del Norte for antimicrobial activity. A total of 54 actinomycetes isolates were obtained from the various sediment samples collected and were then tested for antagonistic activity against Escherichia coli , Staphylococcus aureus , Candida utilis and Aspergillus niger . Results indicated that 14 out of 54 isolates were active against at least one of the test microorganisms, 13 were active against at least one test bacteria, and four was active against at least one test fungi. It was noted that the terrestrial site was the richest source of antibiotic-producing actinomycetes where approximately 52% of the isolates were antibacterial and 13% were antifungal. No marine isolate was found active against the test microorganisms while one brackish isolate was found to be inhibitory. Selected bioactive isolates were chosen to be further screened against other strains of the test microorganisms during the secondary screening. Resulting mean diameter of inhibition zones revealed isolate ti5 as the most potent of all the isolates with a minimum inhibitory microbial concentration of 20% (MIC). Cultural and morphological characterization classified it under the genus Micromonospora . It can be recommended therefore that marine, brackish and terrestrial sediments of San Isidro, Babak District, Island Garden City of Samal be further investigated for antibiotic-producing actinomycetes. The number of actinomycetes isolated with persistent antimicrobial activity isolated suggests that Samal Island sediments may be a potential source of novel antibiotics. Keywords: antimicrobial, actinomycetes, Samal Island, minimum inhibitory concentration DOI = 10.3860/jrsce.v4i3.631 Journal of Research in Science, Computing, and Engineering 4 :3 (2007), pp. 29-38

Comparison of Microdilution and Disc Diffusion Methods in Assessing the in vitro Activity of Fluconazole and Melaleuca alternifolia (Tea Tree) Oil Against Vaginal Candida Isolates

The in vitro activity of fluconazole and Melaleuca alternifolia (tea tree) oil was evaluated against 99 vaginal Candida strains by the broth microdilution and disc diffusion methods. The microdilution method was performed in accordance with NCCLS-M27A guidelines. An investigational method was used for the disc diffusion test. Fluconazole and tea tree oil minimum inhibitory concentrations (MICs) obtained at 48 h tended to increase 1- to 2-fold or remain the same compared to 24 h readings for most of the isolates tested. C. krusei and C. norvegensis had significantly higher MICs and smaller inhibition zones for fluconazole compared to other species. Tea tree oil MICs were found to be similar, in general, for all Candida spp. tested. The geometric mean MIC of tea tree oil for all isolates was 2.2% (range, 0.25-4%) at 24 h and 3.0% (range, 1-8%) at 48 h. Tea tree oil mean inhibition zone diameter was 24 mm (range,14-42 mm) at 24 h and 15.8 mm (range,10-35 mm) at 48 h. in vitro activity of tea tree oil against fluconazole-resistant Candida strains was of particular interest. The isolates had similar tea tree oil MICs and inhibition zone diameters regardless of their fluconazole susceptibility profile. Tea tree oil MIC ranges (inhibition zone diameter ranges) were 2-4% (12-21 mm) and 2% (35 mm) at 48 h for C. krusei and C. norvegensis, respectively. These results suggest that tea tree oil MICs of the fluconazole-resistant isolates are comparable to those of fluconazole-susceptible isolates. This in vitro finding is promising for potential use of topical tea tree oil formulations in the treatment of candidiasis due to fluconazole-resistant strains.

Susceptibility studies of multiply resistant Haemophilus influenzae isolated from pediatric patients and contacts.

From February 1981 to December 1983, 225 strains were isolated from pediatric patients infected with Haemophilus influenzae. Forty-one strains were found to be resistant to ampicillin, chloramphenicol, and other antibiotics. They were isolated from 20 patients with invasive diseases (meningitis, 16; bacteremia, 4) and 21 with noninvasive diseases (otitis media, 19; conjunctivitis, 2). During this period, 44 patients with invasive diseases were seen (meningitis, 28; bacteremia, 16). Strains resistant to both ampicillin and chloramphenicol occurred in 45.4% of cerebrospinal fluid and blood isolates and in 51% of cerebrospinal fluid isolates only. In this group, individual resistance to ampicillin was 50%; chloramphenicol, 52.2%; tetracycline, 54.5%; and sulfamethoxazole-trimethoprim, 63.6%. No epidemiological relationship could be found among the patients. The presence of asymptomatic carriers was investigated in two nurseries and in eight family groups. From a total of 125 individuals studied, 80 were found to be colonized by H. influenzae, and 36 carried multiply resistant strains. From patients and carriers, 77 strains were found to be resistant to ampicillin, chloramphenicol, and other drugs; 39 belonged to type b (cerebrospinal fluid, 16; blood, 4; ear, 7; and nasopharynx, 12), and 38 were non-type b. The most frequent pattern of resistance was ampicillin-chloramphenicol-tetracycline-sulfamethoxazole-trimethoprim (94.8%), followed by ampicillin-chloramphenicol-tetracycline (3.9%). The disk diffusion method correctly predicted multiple resistance. The mean inhibition zone diameters were: ampicillin, 12.8 mm; chloramphenicol, 15.2 mm; tetracycline, 9.9 mm; and sulfamethoxazole-trimethoprim, 10.8 mm. These resistant strains were susceptible to cefotaxime, moxalactam, cefoperazone, cefuroxime, rifampin, and gentamicin. Our data suggest that in Spain the resistance of H. influenzae to ampicillin and chloramphenicol is endemic and that other effective therapeutic modalities are needed.

Inability of the standardized disk agar-diffusion test to measure susceptibility of the fluorescent group of pseudomonads to gentamicin.

Four hundred thirteen clinical isolates of fluorescent pseudomonads consisting of 286 Pseudomonas aeruginosa and 127 organisms of the Pseudomonas fluorescent group were tested for susceptibilities to gentamicin by the broth-dilution method and by the standardized disk agar-diffusion test, using Mueller-Hinton agar from three sources. Different regression lines and significantly different mean inhibition zone diameters were found for the three Mueller-Hinton agars. Single zone-diameter breakpoints of either 13 or 16 mm for the standardized disk agar-diffusion test produced unacceptable rates of false-sensitive and false-resistant interpretations. When error rates were limited by using zone-diameter breakpoints determined by the method of error rate-bound analysis, the percentage of indeterminate interpretations became so large as to make the standardized disk agar-diffusion test impractical. It is concluded that the standardized disk agar-diffusion test should not be used for testing susceptibility of the fluorescent pseudomonads to gentamicin, and presumably other aminoglycosides.