Evaluation of Different Phenotypic Methods for Detection of Biofilm Formation among the Clinical Isolates
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Biofilm-producing staphylococci have been identified from various clinical samples such as pus, blood, urine and skin surfaces, in addition to device associated illnesses. In the study included 100 clinical isolates of Staphylococci spp. Biofilm detection was performed on clinical staphylococci spp. isolates using two different phenotypic methods, including Tissue Culture plate (TCP) and Congo red agar (CRA).By the TCP method revealed that, 55 (55%) Staphylococcus isolates were biofilm producers, while 45 (45%) were non- or weak biofilm producers. Among 55(55%) biofilm producers, 31 (56.36%) were strong biofilm producers, while 24 (43.63%) were moderate biofilm producers. By the CRA method, among 100 staphylococcal isolates, 10(10%) were produced biofilm while 90 (90%) were non/weak biofilm producers. Among the 10 biofilm producers, strong biofilm was produced by 3(30%) and moderate biofilm was produced by 7 (70%). TCP is considered a highly significant test, p = 0.001. As for CRA, it detected a very low number of biofilm producers compared to total positive biofilm producers. According to the p = 0.381, CRA method is considered the non-significant test.The two phenotypic methods were evaluated and it was found that CRA method was less sensitive in detecting biofilm formation. TCP can be recommended as a general screening method for detection of biofilm producing bacteria.Keywords:
Congo red
To evaluate which dye is effective in a plate assay for detecting extracellular cellulase activity produced by fungi, four chromogenic dyes including remazol brilliant blue, phenol red, congo red, and tryphan blue, were compared using chromagenic media. For the comparison, 19 fungal species belonging to three phyla, ascomycota, basidiomycota, and zygomycota were inoculated onto yeast nitrogen-based media containing different carbon substrates such as cellulose (carboxylmethyl and avicel types) and cellobiose labeled with each of the four dyes. Overall, the formation of clear zone on agar media resulting from the degradation of the substrates by the enzymes secreted from the test fungi was most apparent with media containing congo red. The detection frequency of cellulase activity was also most high on congo red-supplemented media. The results of this study showed that congo red is better dye than other three dyes in a plate assay for fungal enzyme detection.
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The following protocol is for making LB agar plates for the purpose of bacterial selection (500mL of LB agar makes about 25 LB agar plates). For the full abstract and additional resources, please visit https://www.addgene.org/plasmid_protocols/bacterial_plates/
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One in 58 strains of bacteria isolated from the compost showed clear colonies after a few days of growth on the plates containing medium made of only agar and water.Water suspension contained only agar (2 and 8g·L -1 ) with two controls (normal saline,LB medium) was inoculated with the bacterium BR5-1 to see whether there was an increasement of the alive bacteria concentration after 48 h of the growth.The results showed that there was a significant rising of the alive bacteria concentration in the agar suspension (6.5×10 3 and 6.0×10 3 cfu ? mL -1 ) compared to that in the normal saline control (6.1×10 2 cfu·mL -1 ),and it was far lower than that in LB (Luria-Bertani) control (1.1×10 8 cfu·mL -1 ).In conclusion,the bacterium strain BR5-1 could degrade agar.
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SUMMARYThe sensitivity of five solid media for detection of Bacillus larvae spores in honey samples; J agar, MYPGP agar, brain heart infusion (BHIT) agar, Colombia agar and horse blood agar was compared in air or under 5% C02. MYPGP agar is superior to all other media tested for detection of low spore levels of B. larvae in honey. Incubation under 5% C02 enhances growth considerably, especially for MYPGP agar and J agar. The plating efficacy described here, where an average of 23% of inoculated spores germinated on MYPGP agar, is higher than reported elsewhere for B. larvae. Thus, contamination levels as low as 200 B. larvae spores/g of honey can be detected with more than 95% probability on MYPGP agar incubated under 5% C02 if 12 or more plates are inoculated.
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In the series of 212 coagulase-negative staphylococci strains isolated from blood cultures, in which the slime production was tested by means of two methods--a method using agar with Congo red and a Christensen method--S. epidermidis, S. haemolyticus and S. hominis were identified most frequently (in 69.3%, 18.4% and 6.6%, respectively). The slime production was detected by both methods in 28 strains (13%) of four species, most often in S. epidermidis (in 17%). By comparing the Congo red agar method with the Christensen method the sensitivity and specificity of the former was determined (85% and 99%, respectively). Thus the Congo red agar method for the detection of slime production by staphylococci seems to be a reliable tool.
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Coagulase
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A simple and rapid semiquantitative technique for the determination of fungal cellulytic activities in solid (agar slant) media has been developed. This method is a combination of Congo-red staining widely used for qualitative cellulase detection and common cellulase activity tests. Previous investigation on the adsorptive effect of cellulose content of media showed that the real enzyme activity values can be measured with minimum loss by means of agar discs cut from the most active zones of slants visualized by Congo-red staining. Different cellulase activity tests (FPase, CMCase and beta-glucosidase by PNPG-method) of seven cellulolytic fungal strains were investigated by this technique. Data give information on the different enzyme profiles of the species. The method can be regarded as very simple and suitable for simultaneous rapid comparison of cellulase components of greater series of fungal strains from agar slant cultures. It can also be used in the case of fungi unable to grow in liquid cultures.
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