Aerobic Plate Counts of 100-ml Samples in Plastic Bags1

1987 ◽  
Vol 50 (4) ◽  
pp. 296-299
Author(s):  
SOPHIA G. CAMPBELL ◽  
PAUL A. HARTMAN
Keyword(s):  
Membrane Filtration ◽  
Most Probable Number ◽  
Plate Method ◽  
Probable Number ◽  
Direct Plating ◽  
Viable Bacteria ◽  
Plate Counts ◽  
Agar Media

Counts from samples that contained low numbers of bacteria were determined by mixing the samples with double-strength agar media in 42-oz (1.2-L) Whirl-Pak bags. The bag-plate method was compared with other direct-plating methods and the most-probable-number and membrane-filtration procedures. Results obtained by using the bag method were as reliable as methods commonly used for analysis of samples that contain low numbers of viable bacteria.

The Occurrence of Legionella Bacteria in Cooling Towers in South Africa

1991 ◽  
Vol 24 (2) ◽  
pp. 149-152 ◽  
Author(s):  
N. A. Grabow ◽  
E. J. Pienaar ◽  
R. Kfir
Keyword(s):  
South Africa ◽  
Most Probable Number ◽  
Cooling Towers ◽  
Probable Number ◽  
Service Water ◽  
Standard Plate ◽  
Viable Bacteria ◽  
Plate Counts ◽  
High Level ◽  
Biocide Treatment

A total of 510 service water samples from cooling towers throughout South Africa were analysed for the presence of Legionella bacteria. Legionella was detected using an immuno-labelling technique based on the most probable number principle. Only cultural (viable) bacteria were counted. Legionellae were found in most of the samples tested. However, in only 4% of the samples a high level of legionellae was recorded. No correlation was found between the numbers of legionellae and those of standard plate counts. Biocide treatment was shown to be effective in the removal of the bacteria from cooling towers after a 3-month treatment period.

Effect of Stress and Resuscitation on Recovery of Indicator Bacteria from Foods Using Hydrophobic Grid-Membrane Filtration

1982 ◽  
Vol 45 (14) ◽  
pp. 1326-1331 ◽  
Author(s):  
M. H. BRODSKY ◽  
P. BOLESZCZUK ◽  
P. ENTIS
Keyword(s):  
Membrane Filtration ◽  
Membrane Filter ◽  
Indicator Bacteria ◽  
Poultry Meat ◽  
Most Probable Number ◽  
Indicator Organism ◽  
Plate Method ◽  
Probable Number ◽  
E Coli ◽  
Raw Poultry

The effects of stress and resuscitation on selective enumeration of coliforms, Escherichia coli and enterococci in mechanically deboned raw poultry meat and in dried foods were studied using a hydrophobic grid membrane filter (HGMF) technique. The effects of four different stresses, sublethal heating, freezing, acid pH and drying, were examined on 25 to 30 samples per indicator organism for each type of stress. Counts obtained with resuscitation were compared statistically to direct selective counts for each series of samples. Also, both the direct and resuscitative HGMF results were compared to a 5-tube most probable number method for coliforms and E. coli and to a spread plate method for the enterococci. The use of appropriate resuscitation procedures not only produced a significant increase in counts over the direct HGMF procedure, but also yielded HGMF results that were statistically equivalent to those obtained by conventional methods.

A Most Probable Number Method for the Enumeration of Legionella Bacteria in Water

1991 ◽  
Vol 24 (2) ◽  
pp. 143-147 ◽  
Author(s):  
N. A. Grabow ◽  
R. Kfir ◽  
W. O. K. Grabow
Keyword(s):  
Water Samples ◽  
Membrane Filtration ◽  
Quantitative Method ◽  
Fluorescent Antibody ◽  
Most Probable Number ◽  
Probable Number ◽  
Comparative Tests ◽  
Antibody Staining ◽  
Direct Fluorescent Antibody ◽  
Yeast Extract Agar

A new quantitative method for the enumeration of Legionella bacteria in water is described. Appropriate tenfold serial dilutions of water samples concentrated by membrane filtration are plated in triplicate on buffered charcoal yeast extract agar. After incubation for 3 days representative smears from individual plates are tested for the presence of Legionella by direct fluorescent antibody staining. The number of positive plates in each dilution is used to calculate the Legionella count by means of conventional most probable number statistics. In comparative tests on a variety of water samples this method yielded significantly higher counts than previously used procedures.

Reduction of Microorganisms on Citrus Fruit Surfaces during Packinghouse Processing

1998 ◽  
Vol 61 (7) ◽  
pp. 903-906 ◽  
Author(s):  
STEVEN PAO ◽  
G. ELDON BROWN
Keyword(s):  
Test Organism ◽  
Citrus Fruit ◽  
Microbial Populations ◽  
Most Probable Number ◽  
Probable Number ◽  
E Coli ◽  
Plate Counts ◽  
High Level ◽  
Inoculation Study ◽  
Fruit Surface

Citrus fruit surface microbial populations were evaluated following various packingline processes of seven Florida commercial packinghouses. At each packinghouse, six fruits (oranges or tangerines) were collected at each of four sampling points. The sampling was conducted in duplicate; thus, 336 fruit were evaluated during this survey. Average aerobic plate counts and yeast and mold counts on fruit surfaces before washing were about 4.0 log CFU/cm2 and 3.3 log CFU/cm2, respectively, and were reduced to 2.1 log CFU/cm2 and 1.3 log CFU/cm2, respectively, by packinghouse processing. Waxing alone reduced the average fruit surface aerobic plate counts and coliform counts from 3.7 log CFU/cm2 and 35.2 most probable number (MPN)/cm2, respectively, to 2.6 log CFU/cm2 and 1.4 MPN/cm2. No Escherichia coli was recovered from fruit at the end of packinghouse processing, and no salmonellae were found on fruit during the entire processing. In an inoculation study to test the effect of packinghouse processes, test organism E. coli was applied to fruit to achieve a high level (4.8 log CFU/cm2) of contamination. The average E. coli count was reduced about 2.4 log cycles by washing and rinsing with potable water (40 psi, 25 °C) for about 30 s. The combination of washing and waxing significantly reduced the inoculated level of E. coli from 4.8 to 1.4 log CFU/cm2.

Comparative study of membrane filtration and enrichment media for the isolation and enumeration of Pseudomonas aeruginosa from sewage, surface water, and swimming pools

1985 ◽  
Vol 31 (8) ◽  
pp. 686-692 ◽  
Author(s):  
A. H. Havelaar ◽  
M. During ◽  
E. H. M. Delfgou-Van Asch
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Membrane Filtration ◽  
Culture Media ◽  
Polluted Water ◽  
Most Probable Number ◽  
Cellulose Ester ◽  
Swimming Pools ◽  
Probable Number ◽  
Membrane Filters ◽  
Swimming Water

The recovery of Pseudomonas aeruginosa on several selective culture media was tested using raw sewage and secondary sewage effluent samples as well as spiked chlorinated imitation swimming water and samples from whirlpools. mPA-medium B gave good recovery of both vital and chlorine-injured P. aeruginosa and selectivity was greater than 90% when analysing whirlpool samples. It is therefore the medium recommended for examination of chlorinated swimming pools. When analysing sewage polluted water with the mPA-B medium, reduced selectivity was noted from low verification rates and from overgrowth by competitive flora. A modified medium (mPA-D; addition of cetrimide, omission of sulphapyridine and actidione) was more selective and sufficiently recovered noninjured cells. Chlorine-injured cells were completely inhibited, however. C-390 (9-chloro-9-(4-diethylaminophenyl)-10-phenylacridan) was confirmed to be highly selective for P. aeruginosa when used in spread plates at a concentration of 30 μg/mL; P. aeruginosa was slightly inhibited. However, the medium could not be used with conventional membrane filtration techniques, because cellulose ester filters interfered with the selective action of C-390. Selectivity could be improved by using Gelman Tuffryn (polysulphone) filters and increasing the C-390 concentration to 120 μg/mL. At this concentration, however, the medium was strongly inhibitory to P. aeruginosa; resuscitation only partially improved recovery. Two other membrane filtration media were tested. Both cetrimide – nalidixic acid agar and Drake's medium No. 19 were inhibitory to chlorine-injured cells. Several types of membrane filters were tested and there was little difference between them. In the most-probable-number technique, recovery of P. aeruginosa was shown to be excellent when using asparagine broth. Malachite green broth was strongly inhibitory to chlorine-injured P. aeruginosa.

The relationship between three potential pathogens and pollution indicator organisms in Nova Scotian coastal waters

1983 ◽  
Vol 29 (10) ◽  
pp. 1261-1269 ◽  
Author(s):  
W. J. Robertson ◽  
R. S. Tobin
Keyword(s):  
Membrane Filtration ◽  
Indicator Bacteria ◽  
Fecal Coliforms ◽  
Most Probable Number ◽  
Indicator Organisms ◽  
Fecal Indicator ◽  
Filtration Method ◽  
Probable Number ◽  
Pollution Indicator ◽  
Nova Scotian

Fifteen stations, in two estuaries, along the Northumberland Strait of Nova Scotia were examined between June and September 1981 for a relationship between the concentrations of commonly monitored fecal indicator bacteria and the potential pathogens Candida albicans, Pseudomonas aeruginosa, and Vibrio parahaemolyticus. Increased densities of these three organisms were usually associated with high densities of indicator bacteria. Whereas C. albicans and P. aeruginosa occur in human fecal wastes, V. parahaemolyticus is indigenous to the marine environment and positively responds to elevated nutrient levels in sewage. There is also some evidence that these bacteria survive as long or longer in marine waters than the common indicator bacteria. While membrane-filtration techniques for the enumeration of C. albicans and P. aeruginosa proved satisfactory, a V. parahaemolyticus membrane-filtration method lacked specificity and was supplemented by a most-probable-number method. In marine recreational and shellfish waters, these three organisms could complement fecal coliforms and fecal streptococci as indicators of human fecal contamination.

A Bacteriological Survey of Raw Ground Beef1

1977 ◽  
Vol 40 (11) ◽  
pp. 790-794 ◽  
Author(s):  
JAMES F. FOSTER ◽  
JAMES L. FOWLER ◽  
WARREN C. LADIGES
Keyword(s):  
Escherichia Coli ◽  
Microbiological Quality ◽  
Retail Store ◽  
Most Probable Number ◽  
Probable Number ◽  
E Coli ◽  
Fecal Streptococci ◽  
Plate Counts ◽  
Aerobic And Anaerobic

The microbiological quality of 150 units of raw ground beef obtained from a local retail store was determined. The range of aerobic plate counts was from 6.9 × 104 to 8.3 × 107/g. By using the most probable number method 96.7% of the 150 units were positive for coliforms, 94.7% for Escherichia coli and 61.3% for Staphylococcus aureus. By the plate methods, 99.3% of the units were positive for fecal streptococci and 56% were positive for Clostridium perfringens. No salmonellae were isolated. Aerobic and anaerobic organisms were isolated and identified. E. coli was the most frequently isolated aerobe followed by organisms in the Klebsiella-Enterobacter group. Among the anaerobic isolates, C. perfringens was the organism most frequently encountered.

Selective enumeration of aromatic and aliphatic hydrocarbon degrading bacteria by a most-probable-number procedure

1996 ◽  
Vol 42 (3) ◽  
pp. 252-258 ◽  
Author(s):  
Brian A. Wrenn ◽  
Albert D. Venosa
Keyword(s):  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Oxidation Products ◽  
Most Probable Number ◽  
Probable Number ◽  
Microtiter Plates ◽  
Degrading Bacteria ◽  
Polycyclic Aromatic ◽  
Pure Cultures ◽  
Plate Counts

A most-probable-number (MPN) procedure was developed to separately enumerate aliphatic and aromatic hydrocarbon degrading bacteria, because most of the currently available methods are unable to distinguish between these two groups. Separate 96-well microtiter plates are used to estimate the sizes of these two populations. The alkane-degrader MPN method uses hexadecane as the selective growth substrate and positive wells are detected by reduction of iodonitrotetrazolium violet, which is added after incubation for 2 weeks at 20 °C. Polycyclic aromatic hydrocarbon degraders are grown on a mixture of phenanthrene, anthracene, fluorene, and dibenzothiophene in a second plate. Positive wells turn yellow to greenish-brown from accumulation of the partial oxidation products of the aromatic substrates and they can be scored after a 3-week incubation period. These MPN procedures are accurate and selective. For pure cultures, heterotrophic plate counts on a nonselective medium and the appropriate MPN procedure provide similar estimates of the population density. Bacteria that cannot grow on the selective substrates do not produce false positive responses even when the inoculum density is very high. Thus, this method, which is simple enough for use in the field, provides reliable estimates for the density and composition of hydrocarbon-degrading microbial populations.Key words: most probable number, polycyclic aromatic hydrocarbon, alkane, hydrocarbon, bacteria.

Levels and Enterotoxigenicity of Clostridium perfringens in Pozole, Tamales, and Birria

2005 ◽  
Vol 68 (2) ◽  
pp. 331-335 ◽  
Author(s):  
V. NAVARRO-HIDALGO ◽  
E. CABRERA-DÍAZ ◽  
H. ZEPEDA ◽  
L. MOTA DE LA GARZA ◽  
A. CASTILLO ◽  
...  
Keyword(s):  
Clostridium Perfringens ◽  
Cell Elongation ◽  
Cytotoxic Effect ◽  
Cell Lysis ◽  
Vero Cells ◽  
Plate Count ◽  
Most Probable Number ◽  
Probable Number ◽  
Quantitative Survey ◽  
Plate Counts

A quantitative survey of Clostridium perfringens in typical foods served at local restaurants was conducted for 18 months in Guadalajara, Mexico. A total of 151 samples, including goat's birria (50), pozole (50), and beef tamales (51), were collected from small restaurants in Guadalajara. Samples were tested for C. perfringens by the most probable number (MPN) method and for mesophilic aerobic plate counts (MAPCs) and coliform, yeast, and mold counts by plate count methods. Isolates confirmed as C. perfringens were further sporulated and tested for cytotoxic or cytotonic effect against Vero cells as an indication of enterotoxin production. C. perfringens was detected in 78 (52%) of all samples at concentrations that ranged from 2.3 to 5.4 log MPN/g. Average MAPCs were 1.3 to 2.7 log CFU/g, depending on the type of dish. Coliform counts ranged from less than 1.0 to 1.5 CFU/g, and yeast and mold counts were less than 1.0 log CFU/g in all cases. A total of 118 isolates of C. perfringens were tested for enterotoxic effect on Vero cells; 82 (70%) showed activity against Vero cells. Of them, 31 isolates induced cell lysis, indicating cytotoxic effect; 41 induced cell elongation, indicating cytotonic effect; and 10 produced both cytotoxic and cytotonic effect. Dilution of the bacterial filtrates that were still producing an effect on Vero cells ranged from 1:80 to 1:5,120. These results underscore the importance of determining enterotoxigenicity when testing for C. perfringens in foods.

Colony-Forming Unit Enumeration by a Plate-MPN Method

1983 ◽  
Vol 46 (10) ◽  
pp. 836-841 ◽  
Author(s):  
S-T. TAN ◽  
R. B. MAXCY ◽  
W. W. STROUP
Keyword(s):  
Standard Technique ◽  
Most Probable Number ◽  
Plate Method ◽  
Probable Number ◽  
Microbial Counts ◽  
Colony Forming Unit ◽  
Pure Cultures ◽  
Petri Plate ◽  
Mpn Test ◽  
Surface Plate

Concepts of the standard surface plate method and the most probable number method (MPN) were combined to provide a new enumeration technique (plate-MPN). Three discrete 0.01-ml samples of an appropriate decimal dilution were inoculated onto each quadrant of a pre-dried petri plate. The discrete spots from the inoculum were then observed for growth after incubation. Results were interpreted analogous to a 3-tube MPN test using presently available tables. Application of the test to pure cultures and mixed flora provided no evidence to indicate the plate-MPN technique to be any less accurate than the standard technique for microbial counts. The plate-MPN technique was less precise than the standard technique. However, the plate-MPN technique has many advantages over traditional methods.

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