Abstract: Microbial contamination in food and water may post a threat to public health. Ice is defined as a food by the U.S. Food and Drug Administration (FDA). According to the International Packaged Ice Association (IPIA), approximately 2 billion bags of ice are sold from retail, wholesale, and vending producers each year in the U.S. Out of 700 commercial ice-making companies, 200 of the aforementioned are not presented by the IPIA and do not comply to specific packaged ice processing standards. Non-IPIA complied samples were collected from gas stations, liquor stores, or convenient stores in Los Angeles, Orange, San Diego/Imperial, and San Bernardino/Riverside counties. The microbiological quality of non-IPIA complied ice samples were compared with the IPIA-complied packaged ice samples using microbiological, molecular, and sequencing analyses. Among 132 non-IPIA complied packaged ice samples analyzed, 13 samples contained unsatisfactory level of heterotrophs, (≥ 500 Most Probable Number [MPN]/ml), 12 samples contained unsatisfactory level of coliforms (≥1 MPN/100 ml), 41 samples had staphylococci, and 67 samples had yeast/mold. None of the 24 IPIA-complied samples had unacceptable microbial levels. None of the samples analyzed showed the presence of the pathogens, Salmonella. Next generation sequencing (NGS) results revealed that there are more diverse microbial populations in non-IPIA than IPIA samples, including opportunistic pathogens. Our results revealed the microbiological quality of non-IPIA and IPIA complied ice samples in southern California. These findings may lead to a better enforcement of processing standard on packaged ice.
To establish and ascertain the nature of the bacteriocins purified from each isolate, their sensitivity to different enzymes was investigated. Corresponding to each LAB isolate, 5 ml volumes of the partially purified bacteriocins were taken in test tubes and separately treated with amylase, lipase, papain, pepsin, catalase and trypsin (100 TU) 1 mg/mL at pH = 7. The samples were incubated separately with each enzyme for 24 hours at 37 °C to determine the effect of the enzyme on the bacteriocins after which the samples were heated for 3-5 minutes at 50-60 °C to denature the enzymes. After enzyme treatment, the bacteriocins were assayed for antimicrobial activity through the agar-well diffusion assay to determine if the bacteriocins retained their activity and hence their susceptibility to a particular enzymes which inferred their nature. Control samples separately containing the enzymes only and some control samples with the bacteriocins only, were exposed to the same conditions for the same duration as the test samples and assayed for antimicrobial activity.
Abstract: Introduction: Skin and soft tissue infections (SSTI's) are commonly caused by both gram positive and gram negative bacteria. The aim of the study was to investigate the presence of methicillin resistant Staphylococcus aureus (MRSA), Extended Spectrum Beta Lactamase (ESBL), Amp C and Metallo β-lactamase producing gram negative bacilli from clinical isolates obtained from patients attending G.S Medical College and Hospital, Pilkhuwa, Uttar Pradesh, India. Materials and Methods: A total of 263 clinical isolates obtained from skin and soft tissue infections were processed from September 2016 to May 2017 in this study. The isolates were identified by conventional microbiological methods and Antimicrobial susceptibility testing was done on Mueller Hinton Agar plate by
Kirby Bauer's disc diffusion method. All the organisms suspected to be methic illin resistant Staphylococcus aureus (MRSA) among gram positive cocci and those gram negative bacilli producing ESBL were detected by phenotypic confirmatory disc diffusion test...............
The different precipitated fractions of the bacteriocins (redissolved/reconstituted) that corresponded to the selected LAB isolates were then investigated for antimicrobial activity test indicator bacteria to allow for bioassay follow up on the bacteriocin containing fractions. This was done through the agar-well diffusion assay as highlighted in subsection 3.2.2. The zones of growth inhibition elicited by the different precipitated fractions were recorded in comparison with those of the crude bacteriocin for each LAB isolate investigated. The fractions with comparable or higher antimicrobial activity were considered to be containing the bacteriocins in a partially purified form and were subjected to further characterisation. Based on their antimicrobial activity, the selected fractions of bacteriocins also pointed out on the concentrations of saturated ammonium sulphate suitable for the subsequent precipitation of the respective bacteriocins.
Agar diffusion test - Wikipedia
Corresponding to each LAB isolate under investigation, the sensitivity of the partially purified bacteriocins to pH was investigated. Volumes of 5 ml of the partially purified bacteriocin were taken in test tubes and their pH values separately adjusted to pH 2, 4, 6, 8, 10, 11 using diluted 1 M NaOH and 1 M HCl solution such that each tube was adjusted to a specific pH under study. After incubating the samples for 2-4 hours at room temperature, the bacteriocins were assayed for antimicrobial activity through the agar-well diffusion assay against indicator bacteria. This was done to determine if the bacteriocins retained their activity after specific pH treatment and hence their pH range of activity.
Diffusion in gel microbiological essay;
Part 2 coversnematodes and rotifers.
Here are links (which I hope remain current) to Internet resourceswhich will assist in microbial identification.
Mastigophora - Flagellates
Ciliophora - Ciliates
Sarcodina (Sarcodia) - Amoebae
You can find good images of testate amoebae by googling Edward Mitchell+ testate amoebae
Fungi Images & Info
Digital Atlas of Actinomycetes [now referred to as Actinobacteria]
Lots of cool organisms by Wim
able to measure the rate of diffusion, a water-agar gel was used.
Enzymes can also be denatured by changes in pH, detergents or radiation. You could take some pineapple and subject it to different heat treatments and see its effects on the gelatine. You have to make up a device and method for testing gelatine that allows replicable and meaningful testing. I recall using the Bloom Strength test at - it was the mass in grams required to press a 12.5 mm diameter plunger 4 mm into the gel. If you did it at home you could even eat the results.
I recently had a diffusion in gel microbiological essay conversation with an organization’s board member who said, “I’m so frustratedMartinus Willum Beijerinck (NL), in 1889, is generally credited with the first thin-layer chromatography (TLC). He diffused a drop of hydrochloric and sulfuric acid mix through a gelatin thin-layer and found that the hydrochloric acid traveled faster than the sulfuric acid, separating into concentric rings. He also pioneered the use of visualization reagents. The hydrochloric acid was visualized with silver nitrate, and the sulfuric acid with barium chloride. Ref
Routine method (agar diffusion test ..
The mostactive protozoa contributing to this nutrient loop are flagellates andnaked amoebae, however ciliates and testate amoebae cycle nutrients toa lesser degree in an aerobic soil.