scholarly journals An expanding bacterial colony forms a depletion zone with growing droplets

Soft Matter ◽  
2021 ◽  
Author(s):  
Hui Ma ◽  
Jordan Bell ◽  
Weijie Chen ◽  
Sridhar Mani ◽  
Jay X. Tang
Keyword(s):  
Agar Plate ◽  
Depletion Zone ◽  
Bacterial Colony

Bacterial droplets formed in a depletion zone following its spread over a large agar plate.

scholarly journals A Statistical Model for Assessing Sample Size for Bacterial Colony Selection: A Case Study of Escherichia Coli and Avian Cellulitis

2000 ◽  
Vol 12 (2) ◽  
pp. 118-125 ◽  
Author(s):  
Randall S. Singer ◽  
Wesley O. Johnson ◽  
Joan S. Jeffrey ◽  
Richard P. Chin ◽  
Tim E. Carpenter ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Statistical Model ◽  
Clinical Sample ◽  
Agar Plate ◽  
Sample Sizes ◽  
Simple Task ◽  
Single Strain ◽  
Bacterial Colony ◽  
E Coli

A general problem for microbiologists is determining the number of phenotypically similar colonies growing on an agar plate that must be analyzed in order to be confident of identifying all of the different strains present in the sample. If a specified number of colonies is picked from a plate on which the number of unique strains of bacteria is unknown, assigning a probability of correctly identifying all of the strains present on the plate is not a simple task. With Escherichia coli of avian cellulitis origin as a case study, a statistical model was designed that would delineate sample sizes for efficient and consistent identification of all the strains of phenotypically similar bacteria in a clinical sample. This model enables the microbiologist to calculate the probability that all of the strains contained within the sample are correctly identified and to generate probability-based sample sizes for colony identification. The probability of cellulitis lesions containing a single strain of E. coli was 95.4%. If one E. coli strain is observed out of three colonies randomly selected from a future agar plate, the probability is 98.8% that only one strain is on the plate. These results are specific for this cellulitis E. coli scenario. For systems in which the number of bacterial strains per sample is variable, this model provides a quantitative means by which sample sizes can be determined.

scholarly journals Microbial and proximate composition of fresh and salted Hilsa, Tenualosa ilisha

2015 ◽  
Vol 42 (2) ◽  
pp. 227-236
Author(s):  
Tahara Rohomania ◽  
Mihir Lal Saha ◽  
Anwar Hossain ◽  
Shankar Chandra Mandal ◽  
Mohammad Shamsur Rahman
Keyword(s):  
Proximate Composition ◽  
Culture Media ◽  
Agar Plate ◽  
Bacterial Count ◽  
Ventral Part ◽  
Fish Sample ◽  
Bacterial Colony ◽  
Fresh Fish ◽  
Salted Fish ◽  
Fish Samples

Bacterial and nutritional quality of fresh and salted hilsa collected from four markets of Dhaka city were investigated. Five different culture media viz. nutrient agar, EMB agar for coliform, SS agar for Salmonella-Shigella, MSA agar for Staphylococcus and TCBS for Vibrio were used. The highest heterotrophic bacterial count 1.22 ± 0.12 × 106 cfu/g was recorded in the fresh fish sample of Karwan Bazar. Maximum coliform count, 1.20 ± 0.10 × 106 cfu/g was detected in the fresh fish sample of the same market. No bacterial colony was found on SS agar and TCBS agar plate in salted fish. Proximate composition of raw hilsa of dorsal and ventral part was 56.49 ± 0.13% and 55.45 ± 0.06% moisture, 23.62 ± 0.28% and 22.99 ± 0.36% protein, 18.01 ± 0.39% and 18.96 ± 0.43% fat and 1.71 ± 0.04% and 2.26 ± 0.09% ash, respectively. In salted T. ilisha, the proximate composition of dorsal and ventral part was 45.13 ± 0.54% and 40.20±0.20% moisture, 20.79 ± 0.17% and 21.48 ± 0.15% protein, 16.89 ± 0.47% and 19.54 ± 0.26% lipid and 16.65 ± 0.41% and 18.35 ± 0.08% ash. The fresh fish samples were associated with high bacterial loads than that of salted fish. The protein, lipid, moisture contents decreased and ash content increased after salting condition.Bangladesh J. Zool. 42(2): 227-236, 2014

scholarly journals Development of a Colony Lift Immunoassay To Facilitate Rapid Detection and Quantification of Escherichia coli O157:H7 from Agar Plates and Filter Monitor Membranes

1998 ◽  
Vol 5 (4) ◽  
pp. 567-573 ◽  
Author(s):  
David T. Ingram ◽  
Chinta M. Lamichhane ◽  
David M. Rollins ◽  
Lewis E. Carr ◽  
Edward T. Mallinson ◽  
...  
Keyword(s):  
Rapid Detection ◽  
Control Point ◽  
Agar Plate ◽  
Traditional Culture ◽  
Enzyme Linked Immunosorbent Assay ◽  
Culture Methods ◽  
Bacterial Colony ◽  
E Coli ◽  
Critical Control Point ◽  
Wide Range

ABSTRACT E. coli O157:H7 is a food-borne adulterant that can cause hemorrhagic ulcerative colitis and hemolytic uremic syndrome. Faced with an increasing risk of foods contaminated with E. coli O157:H7, food safety officials are seeking improved methods to detect and isolate E. coli O157:H7 in hazard analysis and critical control point systems in meat- and poultry-processing plants. A colony lift immunoassay was developed to facilitate the positive identification and quantification of E. coli O157:H7 by incorporating a simple colony lift enzyme-linked immunosorbent assay with filter monitors and traditional culture methods. Polyvinylidene difluoride (PVDF) membranes (Millipore, Bedford, Mass.) were prewet with methanol and were used to make replicates of every bacterial colony on agar plates or filter monitor membranes that were then reincubated for 15 to 18 h at 36 ± 1°C, during which the colonies not only remained viable but were reestablished. The membranes were dried, blocked with blocking buffer (Kirkegaard and Perry Laboratories [KPL], Gaithersburg, Md.), and exposed for 7 min to an affinity-purified horseradish peroxidase-labeled goat anti-E. coli O157 antibody (KPL). The membranes were washed, exposed to a 3,3′,5,5′-tetramethylbenzidine membrane substrate (TMB; KPL) or aminoethyl carbazole (AEC; Sigma Chemical Co., St. Louis, Mo.), rinsed in deionized water, and air dried. Colonies of E. coli O157:H7 were identified by either a blue (via TMB) or a red (via AEC) color reaction. The colored spots on the PVDF lift membrane were then matched to their respective parent colonies on the agar plates or filter monitor membranes. The colony lift immunoassay was tested with a wide range of genera in the family Enterobacteriaceae as well as different serotypes within the E. coli genus. The colony lift immunoassay provided a simple, rapid, and accurate method for confirming the presence of E. coli O157:H7 colonies isolated on filter monitors or spread plates by traditional culture methods. An advantage of using the colony lift immunoassay is the ability to test every colony serologically on an agar plate or filter monitor membrane simultaneously for the presence of the E. coli O157 antigen. This colony lift immunoassay has recently been successfully incorporated into a rapid-detection, isolation, and quantification system for E. coli O157:H7, developed in our laboratories for retail meat sampling.

scholarly journals Hand Washing Rituals in Trauma Theatre: Clean or Dirty?

2006 ◽  
Vol 88 (1) ◽  
pp. 13-15 ◽  
Author(s):  
L Hajipour ◽  
L Longstaff ◽  
V Cleeve ◽  
N Brewster ◽  
D Bint ◽  
...  
Keyword(s):  
Randomised Trial ◽  
Agar Plate ◽  
Hand Washing ◽  
Degree Of Contamination ◽  
Suitable Alternative ◽  
Bacterial Colony ◽  
Alcohol Group ◽  
First Case ◽  
Colony Forming Units ◽  
Duration Of Surgery

INTRODUCTION The aim of this study was to investigate the degree of contamination of a surgeon's hand following use of chlorhexidine gluconate or alcohol gel as disinfectants. MATERIALS AND METHODS In this prospective, randomised trial, orthopaedic surgeons were allocated to one of two different hand-washing protocols using a randomisation table. The hand-washing protocol dictated that all surgeons should wash for 5 min with chlorhexidine for their first case. Thereafter, the surgeon was randomised to wash for 3 min with either alcohol gel or chlorhexidine. At the end of each procedure, the gloves of each surgeon were carefully removed and the fingertips from each hand were placed on an agar plate. The number of bacterial colonies present after 24 h and 48 h of incubation were recorded for each agar plate by a microbiologist blinded to the washing protocol used. RESULTS Overall, 41 procedures and 82 episodes of hand washings were included in the study. Two episodes were discarded due to contamination at the time of glove removal. Four hands (8%) were contaminated in the chlorhexidine group compared to 19 (34%) in the alcohol group. Fisher's exact test confirmed a significantly higher risk of contamination using alcohol gel compared to chlorhexidine (P = 0.002). In addition, the average bacterial colony count was substantially higher in the alcohol group (20 colony forming units) compared to the chlorhexidine group (5 colony forming units). There was no relationship between the duration of surgery and the degree of contamination (P = 1.12). CONCLUSIONS Alcohol gel disinfectant is not a suitable alternative to chlorhexidine when hand washing before surgery. This study has identified a higher risk of bacterial contamination of surgeons' hands washed with alcohol. This may lead to higher levels of postoperative infection in the event of glove perforation.

scholarly journals Visualizing Bacterial Colony Morphologies Using Time-Lapse Imaging Chamber MOCHA

2017 ◽  
Vol 200 (2) ◽  
Author(s):  
Maria Peñil Cobo ◽  
Silvia Libro ◽  
Nils Marechal ◽  
David D'Entremont ◽  
David Peñil Cobo ◽  
...  
Keyword(s):  
Microbial Growth ◽  
Environmental Control ◽  
Agar Plate ◽  
Time Lapse ◽  
Interspecies Interactions ◽  
Pellicle Formation ◽  
Bacterial Colony ◽  
Microbial Life ◽  
Double Decker ◽  
Microscopic Inspection

ABSTRACTCapturing microbial growth on a macroscopic scale is of great importance to further our understanding of microbial life. However, methods for imaging microbial life on a scale of millimeters to centimeters are often limited by designs that have poor environmental control, resulting in dehydration of the agar plate within just a few days. Here, we created MOCHA (microbialchamber), a simple but effective chamber that allows users to study microbial growth for extended periods (weeks) in a stable environment. Agar hydration is maintained with a double-decker design, in which two glass petri dishes are connected by a wick, allowing the lower plate to keep the upper plate hydrated. This flexible chamber allows the observation of a variety of microbiological phenomena, such as the growth and development of single bacterial and fungal colonies, interspecies interactions, swarming motility, and pellicle formation.IMPORTANCEDetailed study of microbial life on the colony scale of millimeters to centimeters has been lagging considerably behind microscopic inspection of microbes. One major reason for this is the lack of inexpensive instrumentation that can reproducibly capture images in a controlled environment. In this study, we present the design and use of a unique chamber that was used to produce several time-lapse movies that aimed to capture the diversity of microbial colony phenotypes over long periods.

A PCR Assay Based on a Sequence-Characterized Amplified Region Marker for Detection of Emetic Bacillus cereus

2004 ◽  
Vol 67 (8) ◽  
pp. 1694-1701 ◽  
Author(s):  
SHIGERU NAKANO ◽  
HIDEKI MAESHIMA ◽  
ATSUSHI MATSUMURA ◽  
KATSUTOSHI OHNO ◽  
SHIGEKO UEDA ◽  
...  
Keyword(s):  
Bacillus Cereus ◽  
Enrichment Culture ◽  
Random Amplified Polymorphic Dna ◽  
Agar Plate ◽  
Brain Heart Infusion ◽  
Pcr Assay ◽  
Bacterial Colony ◽  
Sequence Characterized Amplified Region ◽  
Rapd Fragment ◽  
Bacillus Strains

A PCR assay for the detection of Bacillus cereus strains able to produce an emetic toxin (cereulide) was developed in this study based on a sequence-characterized amplified region (SCAR) derived from a random amplified polymorphic DNA (RAPD) fragment. One of the RAPD fragments generated was selected, cloned, and sequenced. A set of PCR primers was newly designed from the SCAR obtained (the sequence of the cloned RAPD fragment) and used in this assay. To determine the specificity of the assay, 30 different B. cereus strains, 8 other Bacillus strains (of six species), and 16 other non-Bacillus strains (from 16 genera) were tested. Results were positive for every emetic B. cereus strain and for only one nonemetic B. cereus strain. For all other bacterial strains, results were negative. Bacterial DNA for PCR was prepared by a simple procedure using Chelex 100 resin from the bacterial colony on the agar plate or from culture after growth in brain heart infusion medium. This PCR assay enabled us to detect the bacteria of emetic B. cereus grown on agar plates but not the bacteria of nonemetic B. cereus. To test this PCR assay for the monitoring of the emetic bacteria, 10 to 70 CFU of B. cereus DSM 4312 (emetic) per g of food was inoculated into several foods as an indicator, followed by a 7-h enrichment culture step. Because this PCR assay based on the SCAR derived from the RAPD fragment was able to detect bacterial cells, this assay should be useful for rapid and specific detection of emetic B. cereus.

scholarly journals Screening of Endophytic Bacteria as Biocontrol Agents Against Bacteria Leaf Blight (Xanthomonas oryzae)

2020 ◽  
Vol 27 (3) ◽  
pp. 215
Author(s):  
Rashidah Abd Halim ◽  
Nor'Aishah Hasan ◽  
Kogeethavani Ramachandran
Keyword(s):  
Endophytic Bacteria ◽  
Agar Plate ◽  
Inhibition Zone ◽  
Inhibitory Effect ◽  
Antagonistic Activity ◽  
Leaf Blight ◽  
Bacterial Leaf Blight ◽  
Bacterial Colony ◽  
Sustainable Environment ◽  
Different Sources

Bacterial leaf blight (BLB) is one of major threats in rice production as it can cause 100% yield loss. Concern on the environment and human health has led an attempt to replace existing methods of chemical control and avoid extensive use of bactericides by using endophytic bacteria. The present study was conducted to screen and characterize bacteria isolated from different sources that has potential as antagonistic bacteria against Xanthomonas oryzaepv. oryzae (Xoo), the causal agent of bacterial leaf blight of paddy. Two hundred and thirty-three endophytic bacteria were successfully isolated from roots and leaves from paddy field. Only 17 endophytic bacterial isolates showed positive antagonistic activity indicated by inhibition zone around bacterial colony against Xoo on nutrient agar plate with 2 endophytic isolates (BCA 3 and BCA 12) showed highest inhibitory effect with 35±0.00 mm in diameter. Molecular identification by 16S rRNA amplification successfully identified the antagonistic endophytic bacteria as Pseudomonas fluorescensand Geobacillus thermoparaffinivorans. Findings in this study revealed the biocontrol abilities of isolated endophytes as an excellent option to be used by agriculture sectors to have sustainable environment.

scholarly journals Development of an Automated, High-Throughput Bactericidal Assay That Measures Cellular Respiration as a Survival Readout for Neisseria meningitidis

2011 ◽  
Vol 18 (8) ◽  
pp. 1252-1260 ◽  
Author(s):  
Puiying A. Mak ◽  
George F. Santos ◽  
Kelly-Anne Masterman ◽  
Jeff Janes ◽  
Bill Wacknov ◽  
...  
Keyword(s):  
Data Analysis ◽  
Neisseria Meningitidis ◽  
High Throughput ◽  
Agar Plate ◽  
Cellular Respiration ◽  
Strongly Correlated ◽  
Kinetic Assay ◽  
Bacterial Colony ◽  
Content Type ◽  
Bactericidal Assay

ABSTRACTComplement-mediated bactericidal activity has long been regarded as the serological correlate of protective immunity againstNeisseria meningitidis. This was affirmed in 2005 at a WHO-sponsored meningococcal serology standardization workshop. The assay currently employed by most laboratories involves determining surviving bacterial colony counts on agar as a readout which is labor-intensive, time-consuming, and not amendable to rapid data analysis for clinical trials. Consequently, there is an acute need to develop a sensitive, high-throughput bactericidal assay to enable a rapid and robust assessment of the effectiveness of vaccine candidates. To this end, we have developed an automated, kinetic assay based on the fluorescent respiration product of resazurin which reduces assay volume, shortens assay time, and facilitates automation of data analysis. We demonstrate proof of concept for applicability of this high-throughput system with multiple meningococcal strains and utilizing different lots of human complement. The assay is robust and highly reproducible. Titers obtained by the fluorescence readout method are strongly correlated with the data obtained using the conventional, agar plate-based assay. These results demonstrate that the detection of bacteria that have survived the bactericidal reaction by measuring metabolic activity using a fluorescent dye as an alternative readout is a promising approach for the development of a high-throughput bactericidal assay.

scholarly journals An expanding bacterial colony forms a depletion zone with growing droplets

2020 ◽  
Author(s):  
H. Ma ◽  
J. Bell ◽  
J.X. Tang
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Bacterial Growth ◽  
Fluid Dynamic ◽  
Bacterial Species ◽  
Cell Interaction ◽  
Water Evaporation ◽  
Depletion Zone ◽  
Biofilm Growth ◽  
Bacterial Colony ◽  
Pattern Dynamics

AbstractMany species of bacteria have developed means to spread on solid surfaces. This study focuses on the expansion of Pseudomonas aeruginosa on an agar gel surface. We report the occurrence and spread of a depletion zone, where the layer of bacteria on the agar becoming thinner. The depletion zone occurs within an expanded colony under conditions of minimal water evaporation. It is colocalized with a higher concentration of rhamnolipids, the biosurfactants that are produced by the bacteria and accumulate in the older region of the colony. With continued growth in bacterial population, dense droplets occur and coalesce in the depletion zone, displaying remarkable fluid dynamic behavior. Whereas expansion of a central depletion zone requires activities of live bacteria, new zones can be seeded by adding rhamnolipids. These depletion zones due to the added surfactants expand quickly, even on plates covered by bacteria that have been killed by ultraviolet light. We propose a model to account for the observed properties, taking into consideration bacterial growth and secretion, osmotic swelling, fluid volume expansion, cell-cell interaction, and interfacial fluid dynamics involving Marangoni flow.SignificanceBacterial growth and pattern formation have strong bearing on their biological functions, such as their spread and accumulation, biofilm growth & its effects on infection and antibiotic resistance. The bacterial species of this study, Pseudomonas aeruginosa, is a human pathogen responsible for frequent infections in wounds, airways, and urinary tract, particularly when involving the use of catheters. The findings of this study and the mechanisms we propose offer new insights on the important behaviors of bacterial collective motility, pattern dynamics, and biofilm growth.

The Order in Which Antibiotics are Administered Affects the Fitness Costs of Adherent-Invasive E. coli (AIEC) Strains

2019 ◽  
Author(s):  
Jordan B Gregg
Keyword(s):  
Crohn’S Disease ◽  
Crohn's Disease ◽  
Combination Therapy ◽  
Agar Plate ◽  
Sequential Therapy ◽  
Negative Control ◽  
Clinical Settings ◽  
Fitness Costs ◽  
Inflammatory Gene Expression ◽  
E Coli

AIEC-LF82 is a strain of bacteria that is surmised to have a role in causing IBD and Crohn’s disease by activating pro-inflammatory gene expression in organisms. Using antibiotics via combination therapy has been a technique used in clinical settings in an attempt to treat the strains, however, the attempts have not been that effective nor efficient in terms of completely halting the growth and colonization of AIEC to treat IBD and Crohn's disease patients. Research has shown that regarding hindering or preventing the colonization bacterial colonies, sequential therapy tends to be more effective and time-efficient than combination therapy, with fewer adverse effects. To test if this is also the case with the AIEC-LF82 strain of bacteria, I first tested AIEC’s response to combination therapy using the Penicillin-Streptomycin, Kanamycin-Chloramphenicol, antimicrobial peptide (AMP), Kanamycin, SPE phase and LB agar plates, all of which were experimental plates other than the LB agar plate that acted as the negative control. I then tested AIEC-LF82’s response to sequential therapy using the LB+ Kan + Spe, LB + AMP + Spe, LB+ Kan/Cam + Spe, LB + P/S + Spe, LB + P/S + Kan and LB + P/S + AMP and one LB agar plate acting as the negative control. The only differences between sets a and b were the order in which antibiotics were administered in the six aforementioned treatment sets. Ultimately, I found that set b of sequential therapy, strong-weak antibiotic treatments, was the most effective treatment but that set a regarding sequential therapy was actually the least effective of all of the treatments. In conclusion, using strong-weak sequential antibiotic therapy treatments appears to be a potentially promising option to treat patients suffering from Crohn's disease and IBD.

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