Largest Inhibition Zone Diameter Research Articles

Antimicrobial Activity and Hardness of as Cast and as Homogenized Cu-Ti Alloys

Cu-Ti alloy, pure copper, and stainless steel AISI 304 were tested in this study for their microstructure, effect of alloying element to hardness, and antibacterial activity. The antibacterial properties were tested against E. coli suspensions. The titanium in Cu-Ti alloy was varied 1-4 wt. %, and the microstructure was modified by homogenization treatment. The antibacterial susceptibility test was done by inhibition zone measurement and bacterial suspension inoculation methods. Result showed the addition of titanium increased hardness from pure copper (44.93 HV) to 79.68-207.6 HV. No inhibition zone was observed for the stainless steel samples, while the largest inhibition zone diameter was gained by pure copper (12.4 mm). The killing bacteria activity test concluded that the compositions of the alloys were not directly linked to the antibacterial activity.

미성숙 솔방울 열수추출물의 항균성

Red pine (Pinus densiflora) is widely used traditional medicine, pharmacological and nutritional values from which the phytochemical compounds are derived. The present study was aimed to examine the antibacterial effects in the absence and presence of a immature red pine cone extract against 13 microorganisms. The components in the aqueous extract from immature red pine cone were identified by GC-MS. About 1.4% of total polyphenolic compound was measured in aqueous extract collected from immature red pine cone. Also, the high concentration of <TEX>${\beta}$</TEX>-phellenandrene, <TEX>${\alpha}$</TEX>-pinene, limonene, bornyl acetate and aldehyde was detected in total ion chromatograms. Of total 13 microorganisms, 4 microorganisms including Pseudomonas aeruginosa, Vibrio cholera, Listeria monocytogenes, Klebsiella pneumonia were effectively killed by aqueous extract of immature red pine cone. The highest anti-bacterial effect was detected in P. aeruginosa, followed by V. cholera, L. monocytogenes and K. pneumonia. In case of P. aeruginosa, the largest diameter of inhibition zone was maintained to 1/2 solution treated cells and slightly decreased at 1/4 and 1/8 solution treated cells. Also, in test used V. cholera and L. monocytogenes, the inhibition zone was strongly formed in only 1 and 1/2 solution treated cells, while K. pneumonia showed the very small diameter of inhibition zone in all concentrations. Therefore, these results suggested that the aqueous extracts of immature red pine cone should be considered as a new and potentially important anti-bacterial substrate to effectively prevent the microbial infection and penetration.

Antibacterial activity of different natural honeys from Transylvania, Romania

Honey is used in food industry and medicine due to its nutritive, therapeutic and dietetic qualities. The microbiological characteristics of 10 unpasteurized honey samples of known origin, collected from Transylvania beekeepers (Romania) were determined. The antibacterial activity of these types of honey against Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Salmonella enteritidis, Salmonella anatum, Salmonella choleraesuis, Bacillus cereus, Bacillus subtilis subsp. spizizenii and Listeria monocytogenes strains was studied. The most sensitive to the antibacterial activity were the two staphylococus strains (the largest diameter of inhibition zone was 18 mm) and B. subtilis strains (13.5 mm). The strains of B. cereus, E. coli, L. monocytogenes and Salmonella spp. were found to present resistance to some of the honey samples. Manna, sunflower and polyfloral honeys presented high antibacterial activity while acacia and linden honeys had a lower activityin terms of the number of sensible strains. Statistical analysis shows that the type of strains and the type of honey have influence on the diameter of inhibition.

Screening and Identification of the antagonistic strain DL-59 of B. velezensis against A. brassicae and biocontrol efficiency

The aim of this study was to screen the antagonistic spore-forming bacteria of Alternaria brassicae and to assess their control effect. The test microorganism was A. brassicae in this experiment. One spore-forming strain named DL-59 with a rather stronger antagonistic activity than ever reported was obtained by using an improved agar plate diffusion method. Morphological, physiological and biochemical tests combined with 16S rDNA sequence analysis were carried out to identify DL-59. Its control effect was studied in the basin culture and the plot trials. Two hundred strains were isolated form soil and 20 antagonistic bacteria strains were obtained through preliminary screen. After the secondary screening, a strain named DL-59 with a rather stronger antagonistic activity was obtained and identified as B. velezensis with the largest diameter of inhibition zone of 23 mm. The control efficacy was 79.07%. The plot trials showed that DL-59 had a visible preventive effect on cabbage black spot disease. This can be applied for biological control of plant disease. The strain can produce spores, which is important for the storage of its preparation.

Anticariogenic potentials of clove, tobacco and bitter kola

Objective To investigate three tropical plant materials – clove seeds [Syzygium aromaticum (S. aromaticum)], bitter kola fruits [Garcinia kola (G. kola)] and tobacco leaves ( Nicotiana species) as potential targeted killers of Streptococcus mutans (S. mutans), a cavity-causing bacterium (gram-positive, facultative anaerobe) that resides in a multispecies microbial community (dental plaque) for the treatment of dental caries (tooth decay). Methods Thirty one (31) teeth samples were collected from patients with obvious signs of tooth decay (swollen gum, weak or fallen tooth, etc.) using sterile swab sticks. These samples were collected from two major dental clinics in Nsukka, Enugu State, Nigeria and investigated by spread inoculation onto sterile blood agar and Mueller Hinton agar (MHA) respectively and incubated at 37 °C for 24 h. The discrete colonies obtained were further re-inoculated onto sterile Mitis salivarius agar (MSA) plates and incubated as above. The isolates were characterized by gram staining and catalase test. Tobacco leaves, clove seeds and bitter kola fruits were ground into powder, extracted with three different solvents ( n-hexane, hot water and ethanol), filtered, dried and stored in clean containers, corked and kept until used. The plant extracts were investigated for phytochemistry, minimum inhibitory concentration (MIC), minimum cidal concentration (MCC) and compared with some conventional antibiotics commonly used against tooth decay. Antibiotic sensitivity test was also carried out. The results were statistically analyzed. Results The extracts showed varied phytochemical composition but most abundantly the flavonoids. Our result also shows that females (16) have more tooth decay than males (15) and that 16 samples were very bloody while 15 were slightly bloody. The microbial characterization showed that 18 samples were catalase-positive indicating the presence of S. mutans while 13 were catalase-negative suspected to be Staphylococcus spp. The Gram reaction confirmed 13 Gram-negative and 18 Gram-positive organisms. The n-hexane extract had the best antimicrobial activity followed by the ethanol and lastly hot water. MIC showed that n-hexane clove extract had the largest inhibition zone diameter, followed by bitter kola extract and lastly tobacco extract. The antibiotic sensitivity test credited ciprofloxacin the best because it exhibited broad spectrum of action. Conclusions Since the n-hexane extract of clove seeds demonstrated preferential growth-inhibitory activity against the causal cariogenic pathogens ( S. mutans) in dental caries, we therefore, report here that clove extract be henceforth considered as a potential ingredient in toothpaste preparation.

Eine einfache methode zur unterscheidung methicillin-resistenter von nur penicillinase-positiven sowie -negativen staphylokokken im agardiffusionstest

Abstracts Coagulase-positive staphylococci (41 methicillin-resistant strains, 28 penicillinase-positive and 12 penicillinase-negative strains) were tested against most types of penicillines commercially available on the Austrian market using both broth-dilution test (incubated during 48 hours at 35°C) and agardiffusion tests (incubated during 24 hours at 30, 35 and 37°C) employing Mueller-Hinton-broth and -agar, respectively, in order to find out the most convenient way of detecting methicillin-resistant strains. Consecutively, the conclusions drawn from these experiments were verified for tests on Isosensitest-agar (Oxoid). It was demonstrated that methicillin-resistant strains could be detected easily with discs of methi-cillin and oxacillin at 30°C ( Download : Download full-size image ). At 35°C this was nearly as easily possible for methicillin but oxacillin discs had to be used at amounts of 1 μg instead of 5 μg. Excepting penicillin G-discs with all the other penicillines differing numbers of methicillin-resistant strains would have been missed at 37°C ( Download : Download full-size image ). Only with discs containing 6 μg penicillin G methicillin-resistant strains were unequivocally identifiable in the agardiffusion test at all 3 incubation-temperatures ( Download : Download full-size image ), the largest inhibition zone diameter being 12 mm. Penicillinase-positive but methicillin-sensitive strains always produced larger inhibition zones up to 30 mm. From these strains again penicillinase-negative strains were equally well distinguishable by much larger inhibition zones. So, the conclusion was drawn that on Mueller-Hinton agar one disc loaded with 6 μg of penicillin G allows proper distinction not only of methicillin-resistant and -sensitive but also of penicillinase-positive and -negative strains of staphylococci. On Isosensitest-agar this is true for an incubation-temperature of 35 but not 37°C ( Download : Download full-size image ).