scholarly journals Broader incubation temperature tolerances for microbial drinking water testing with enzyme substrate tests

2013 ◽  
Vol 12 (1) ◽  
pp. 113-121 ◽  
Author(s):  
Robert L. Matthews ◽  
Rosalind Tung
Keyword(s):  
Drinking Water ◽  
Incubation Temperature ◽  
Significant Loss ◽  
Testing Procedures ◽  
E Coli ◽  
Water Testing ◽  
Enzyme Substrate ◽  
Laboratory Facilities ◽  
Microbiological Testing ◽  
Incubation Temperatures

Microbiological testing is an integral part of measures to ensure safe drinking water. However, testing can be restricted in low-resource settings by the requirement for specialized laboratory facilities and testing procedures. Precisely controlled incubation temperature is one example. The effect of varied incubation temperatures on the performance of two enzyme substrate tests for the detection of Escherichia coli and total coliforms has been examined. The aim was to determine whether these tests would provide consistent and comparable enumeration over a broader temperature range than currently specified. Recovery of chlorine-injured and wild type E. coli was examined over a range of non-standard incubation temperatures in comparison to 37 °C ± 1. Colilert® and Aquatest, a new E. coli-specific detection medium, served as the two representative enzyme substrate media. Recovery of chlorine-injured E. coli in Colilert was not impaired within the range 33–39 °C; the equivalent range in Aquatest medium was 31–43 °C. Both these tests recovered E. coli without significant loss of performance over a wider range of temperatures than currently specified.

Effect of Incubation Temperature on Aerobic Plate Counts of Beef and Sheep Carcasses

2008 ◽  
Vol 71 (2) ◽  
pp. 373-375 ◽  
Author(s):  
JACINTA SIMMONS ◽  
MARK L. TAMPLIN ◽  
IAN JENSON ◽  
JOHN SUMNER
Keyword(s):  
Incubation Temperature ◽  
Refrigerated Storage ◽  
Beef Carcasses ◽  
Microbiological Testing ◽  
Plate Counts ◽  
Incubation Temperatures

Australian regulations for microbiological testing of carcasses specify a number of incubation temperatures and media for meat processed at both domestic and export establishments. Accordingly, the effect of incubation temperature and media on aerobic plate counts of samples from beef and sheep carcasses was investigated. For both species, aerobic plate counts on Petrifilm incubated at 35°C were significantly lower than those counts on Petrifilm and pour plates incubated at 25 and 30°C, reflecting the inability of many psychrotrophs to grow at 35°C. When samples were taken from carcasses that had been stored in abattoir chillers for periods between 16 h and 5 days, difference between counts at 35°C versus those incubated at 25 and 30°C became greater as the period of refrigerated storage increased. For export beef carcasses, the effect of this difference is minimal, since the vast majority of counts incubated at 35°C are done on carcasses that have been chilled for less than 24 h and will not have a large proportion of psychrotrophs.

A Pilot Study into the Use of Springs for Drinking Water in Western and Central Newfoundland, Canada

2009 ◽  
Vol 4 (3) ◽  
Author(s):  
Keith Nicol
Keyword(s):  
Drinking Water ◽  
Pilot Study ◽  
Water Supply ◽  
Tap Water ◽  
Provincial Government ◽  
E Coli ◽  
Water Testing ◽  
Community Water ◽  
Frequency Of Use ◽  
Over Time

Dissatisfaction with tap water has gradually grown over time and in many places in Canada bottled water and various tap water filtering systems have become increasingly popular. In Newfoundland, road side springs are another popular alternative drinking water supply, yet the Provincial Government does not test or treat this water. This study examines 18 communities in Western Newfoundland to determine why people don't drink tap water, the frequency of use of road side springs, and the bacteriological safety of a sampling of road side springs. The results indicate that the main reason for not drinking tap water was that it was perceived to be unsafe. But springs were used by 23 % of those surveyed and these springs were found to contain E. coli and/or coliforms 43 % of the time. By comparison, tap water testing by Newfoundland Environmental Health Officers found that between 5-6% of the community water supplies in Western and Central Newfoundland recorded the presence of coliform and/or E. Coli in 2007.

scholarly journals Use of the ISO 9308-1 procedure for the detection of E. coli in water utilizing two incubation temperatures and two confirmation procedures and comparison with defined substrate technology

2008 ◽  
Vol 6 (3) ◽  
pp. 389-397 ◽  
Author(s):  
C. R. Fricker ◽  
S. Bullock ◽  
K. Murrin ◽  
S. I. Niemela
Keyword(s):  
Drinking Water ◽  
Klebsiella Oxytoca ◽  
Isolation Procedure ◽  
Test Method ◽  
Primary Isolation ◽  
E Coli ◽  
Large Numbers ◽  
The Difference ◽  
Incubation Temperatures ◽  
Drinking Water Samples

Disinfected and non-disinfected samples have been used to determine the accuracy of the ISO procedure (ISO 9308-1) for detection of E. coli in drinking water. Samples were analysed using the ISO procedure at both 36 and 44°C and using the defined substrate technology method Colilert-18®/Quanti-Tray® (Colilert-18). Utilizing the confirmation procedure described in ISO 9308-1, large numbers of false positive E. coli results were obtained using the ISO primary isolation procedure at 36°C. However, when glucuronidase production was used as the confirmation procedure, the ‘confirmed’ count of E. coli was lowest with ISO 9308-1 performed at 36°C. When TTC medium was incubated at 36°C confirmation using production of indole at 44°C resulted in 29% more ‘E. coli’ being recovered than when confirmation was performed using production of glucuronidase. When 44°C was used as the primary isolation temperature the difference between the number of ‘confirmed’ E. coli identified using the two confirmation procedures was less than 1% and was not significant. Identification of isolates which ‘confirmed’ when using production of indole at 44°C as the test method but °which failed to produce β-D-glucuronidase, showed that the majority of these isolates were Klebsiella oxytoca.

Comparison and Recovery of Escherichia coli and Thermotolerant Coliforms in Water with a Chromogenic Medium Incubated at 41 and 44.5°C

1999 ◽  
Vol 65 (8) ◽  
pp. 3746-3749 ◽  
Author(s):  
Jose L. Alonso ◽  
Adela Soriano ◽  
Oscar Carbajo ◽  
Inmaculada Amoros ◽  
Hemda Garelick
Keyword(s):  
Escherichia Coli ◽  
Membrane Filtration ◽  
Incubation Temperature ◽  
Lauryl Sulfate ◽  
Marine Waters ◽  
Sodium Pyruvate ◽  
Chromogenic Medium ◽  
E Coli ◽  
Thermotolerant Coliforms ◽  
Incubation Temperatures

ABSTRACT This study compared the performance of a commercial chromogenic medium, CHROMagarECC (CECC), and CECC supplemented with sodium pyruvate (CECCP) with the membrane filtration lauryl sulfate-based medium (mLSA) for enumeration of Escherichia coli and non-E. coli thermotolerant coliforms (KEC). To establish that we could recover the maximum KEC and E. coli population, we compared two incubation temperature regimens, 41 and 44.5°C. Statistical analysis by the Fisher test of data did not demonstrate any statistically significant differences (P = 0.05) in the enumeration of E. coli for the different media (CECC and CECCP) and incubation temperatures. Variance analysis of data performed on KEC counts showed significant differences (P = 0.01) between KEC counts at 41 and 44.5°C on both CECC and CECCP. Analysis of variance demonstrated statistically significant differences (P = 0.05) in the enumeration of total thermotolerant coliforms (TTCs) on CECC and CECCP compared with mLSA. Target colonies were confirmed to be E. coli at a rate of 91.5% and KEC of likely fecal origin at a rate of 77.4% when using CECCP incubated at 41°C. The results of this study showed that CECCP agar incubated at 41°C is efficient for the simultaneous enumeration of E. coli and KEC from river and marine waters.

scholarly journals Postexposure factors influencing the duration of postantibiotic effect: significance of temperature, pH, cations, and oxygen tension.

1997 ◽  
Vol 41 (8) ◽  
pp. 1693-1696 ◽  
Author(s):  
K Fuursted
Keyword(s):  
Sodium Chloride ◽  
Oxygen Tension ◽  
Incubation Temperature ◽  
Penicillin G ◽  
Postantibiotic Effect ◽  
High Concentration ◽  
E Coli ◽  
Generation Times ◽  
Mueller Hinton ◽  
Incubation Temperatures

The purpose of the present study was to assess and compare the impacts of various postexposure conditions on postantibiotic effect (PAE). PAEs were induced in Staphylococcus aureus and Escherichia coli by exposing the organisms to different antibiotics (penicillin G, ampicillin, erythromycin, ciprofloxacin, and gentamicin) at 5 or 10 times the MIC in plain Mueller-Hinton broth for 1 h at 35 degrees C. Regrowth was determined by measuring the viable counts after drug removal by a 10(-3) or 10(-4) dilution procedure under various postexposure conditions (incubation temperatures at 20, 25, 30, or 35 degrees C; growth under shaken, unshaken, anaerobic conditions; pH 6.0, 7.4, or 9.0; and with sodium chloride concentrations at 0, 1, 3, or 6%). PAE increased in response to a decrease in incubation temperature from 35 to 20 degrees C, and a significant correlation between bacterial generation times and duration of PAEs (r2, 0.82 to 0.97) was demonstrated. The duration of PAE was also modified by the pH in the regrowth medium. PAE increased considerably for S. aureus at pH 6.0 and 9.0 compared to that at pH 7.4 after induction with penicillin G, and with gentamicin the PAE against S. aureus recovering at pH 6.0 also increased considerably. A high concentration of sodium chloride in the regrowth medium produced the most extensive changes in PAE except for that against E. coli induced by ampicillin. PAE increased significantly in response to increased salinity. No recovery even after overnight incubation was detected for S. aureus after preexposure to penicillin, ciprofloxacin, or gentamicin. Only minor changes in the duration of PAE were observed in relation to recovery oxygen tension. It is concluded that many postexposure factors have a profound effect on the duration of PAE.

Effect of temperature on activity of predators of Salmonella typhimurium and Escherichia coli in estuarine water

1980 ◽  
Vol 31 (6) ◽  
pp. 851 ◽  
Author(s):  
Cambridge J Mc ◽  
TA McMeekin
Keyword(s):  
Escherichia Coli ◽  
Incubation Temperature ◽  
Effect Of Temperature ◽  
Estuarine Water ◽  
Survival Curves ◽  
Temperature Optimum ◽  
E Coli ◽  
Similar Survival ◽  
Incubation Temperatures ◽  
Micro Organisms

The survival of S. typhimurium was compared with that of E. coli in estuarine water samples at various incubation temperatures. Both organisms exhibited similar survival curves, and their presence resulted in the growth of comparable numbers of predacious micro-organisms at all temperatures. Bacterial decline was found to be dependent on the presence of both bacterial and protozoan predators, the latter having a temperature optimum of 15-20�C and the former becoming more important as the incubation temperature increased.

Cell-Specific Chemical Delivery Using a Selective Nitroreductase–Nitroaryl Pair

2018 ◽  
Author(s):  
Todd D. Gruber ◽  
Chithra Krishnamurthy ◽  
Jonathan B. Grimm ◽  
Michael R. Tadross ◽  
Laura M. Wysocki ◽  
...  
Keyword(s):  
Small Molecules ◽  
Mammalian Cells ◽  
Target Cells ◽  
Specific Chemical ◽  
E Coli ◽  
Enzyme Substrate ◽  
Cell Specificity ◽  
General Chemical ◽  
Increased Activity ◽  
Enzyme Variant

<p>The utility of<b> </b>small molecules to probe or perturb biological systems is limited by the lack of cell-specificity. ‘Masking’ the activity of small molecules using a general chemical modification and ‘unmasking’ it only within target cells could overcome this limitation. To this end, we have developed a selective enzyme–substrate pair consisting of engineered variants of <i>E. coli</i> nitroreductase (NTR) and a 2‑nitro-<i>N</i>-methylimidazolyl (NM) masking group. To discover and optimize this NTR–NM system, we synthesized a series of fluorogenic substrates containing different nitroaromatic masking groups, confirmed their stability in cells, and identified the best substrate for NTR. We then engineered the enzyme for improved activity in mammalian cells, ultimately yielding an enzyme variant (enhanced NTR, or eNTR) that possesses up to 100-fold increased activity over wild-type NTR. These improved NTR enzymes combined with the optimal NM masking group enable rapid, selective unmasking of dyes, indicators, and drugs to genetically defined populations of cells.</p>

H2S papers as presumptive tests for Salmonella contamination in tropical drinking water

1996 ◽  
Vol 34 (7-8) ◽  
pp. 187-194 ◽  
Author(s):  
Tanya Gawthorne ◽  
Robyn A. Gibbs ◽  
Kuruvilla Mathew ◽  
Goen E. Ho
Keyword(s):  
Drinking Water ◽  
Hydrogen Sulphide ◽  
Incubation Temperature ◽  
Indicator Bacteria ◽  
Coliform Bacteria ◽  
Salmonella Spp ◽  
Faecal Contamination ◽  
Tropical Waters ◽  
Remote Areas ◽  
Traditional Indicator

Coliform bacteria may not be adequate as sole indicators of recent faecal contamination in tropical waters. Salmonella spp. in particular have been found in tropical waters in the absence of traditional indicator bacteria. Remote areas without access to a laboratory have no opportunity for salmonellae analysis as portable tests are currently not available. H2S papers indicate the presence of hydrogen sulphide producing bacteria, a characteristic shared by the majority of Salmonella spp.. The potential of H2S papers to act as a presumptive test for salmonellae in the absence of coliform bacteria was assessed. Salmonella spp. grew in the H2S medium, with an optimum incubation temperature of 37°C and a recommended length of incubation for a negative result of 48 hours. The presence of high numbers of the type of noncoliform bacteria commonly found in drinking water did not affect the performance of the H2S strips. H2S papers are recommended for use in conjunction with a coliform test as a presumptive test for the presence of Salmonella spp. in drinking water.

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