Bacteria colony-forming units

Summation of mesophilic bacteria, fungi, and thermophilic bacteria. CPU = colony-forming units. 

CFXI Viable micro-organisms (bacteria, yeasts mould) capable of growth under the prescribed conditions (medium, atmosphere, time and temperature) develop into visible colonies (colony forming units) which are counted. The term colony forming unit (CPU) is used because a colony may result from a single micro-organism or from a clump / cluster of micro-organisms. 

In a parallel test with water instead of disinfectant the colony forming units (cfu) of surviving bacteria are determined and the reduction in viable counts is calculated. 

The most common criticism of whole-cell MALDI is that the method requires a relatively large number of cells, usually obtained directly from culture media. In principle, an analysis of even a few unknown bacteria (a colony-forming unit) is possible after a culture step. More important is the number of bacteria needed in a sample or on the sample probe for successful analysis. Detection of a very small number of bacteria could eliminate the need for a preliminary culture step. This would be a considerable asset for environmental analysis (unless to many bacteria were detected) and for the detection of a bioterrorism-related release of bacteria. 

Faeces from colonised cows may contain from 102 to 107 colony-forming units (CFU) of Salmonella cells per gram of faeces. Particularly calves and heifers colonised with E. coli 0157 H7 may shed the bacteria at levels ranging from 102 to 105 CFU g 1 (Himathongham el al., 1999). Furthermore, calves younger than four months are the main domestic animals that excrete pathogenic protozoa like Giardia and Cryptosporidia. 

The oral cavity and the lower gastrointestinal tract are densely colonized by bacteria with counts exceeding 109 colony-forming units (CFU)/ml, whereas the density in the stomach and proximal small bowel is normally below 105 CFU/ml (fig. 1). Bacterial density increases through... 

Li and Bashir, 2002) with interdigitated electrodes for DEP capture of bacteria and the interdigitated measurement electrodes to monitor growth. Panel (B) is showing a conductance plot generated based on bacterial growth of arbitrary numbers of colony forming units (cfu)/ml. 

When the CO2 treatment was finished, residual viable micro-organisms were counted according to plate standard procedures (for solid media and conditions see Table 9.10-1). The cultures were suspended in PBS buffer and diluted to reach about 107 colony-forming units, CFU/ml, for bacteria and 105 CFU/ml for yeast. 

Total count for aerobic bacteria averages 150 x 10,000. It is presumed that these units are colony-forming units per milliliter(cfu/ml). 

Description for any type of bacteria found freely in cooling water rather than bound up in biofilm and most commonly tested by means of dip-slides. A poorly maintained cooling system may contain 1 x 106 or more colony forming units (cfu) per milliliter of water. 

Early studies of marine bacteria via culture-based methods indicated a low abundance in seawater (Sverdrup et ah, 1942 ZoBeU, 1941), and that their assemblages were not diverse (Waksman, 1934). Rehable enumeration techniques developed in the late 1970s indicated that typical bacterial abundances in marine surface waters exceeded colony-forming unit (cfu) estimates by over two orders of magnitude (Hobbieeia/., 1977), with abundances of typically 10 cells in surface waters. 

Microbial populations in landfill leachate-contaminated aquifers are dominated by bacteria (eubacteria and archaea), as shown by analysis of the phospho lipid fatty acids (PLFAs) (Ludvigsen et al, 1999). The total number of bacteria reported in landfill leachate plumes are in the range of 4 X 10" -1.5 X 10 cells g dry weight (dw) and the number of colony-forming units, hving cells, are in the range of 60-10 CFU g dw (Christensen et al, 2001). However, the large variation caused by different analytical methods and the fact that different types of aquifers were studied mask the difference in the number of... 

The whole-water sample and the sample obtained from the treated membrane were analyzed identically to determine the growth and enumeration of the fecal coliform. Based on their probable contamination, at least 2 aliquots of 0.1 to 100 mL of the prepared samples were filtered through a 0.45- Lim membrane to filter out all bacteria. The membranes were placed in petri dishes containing TTC + tergitol agar (Diagnostic Pasteur ref 64454). The dishes were incubated, and then the bacteria were enumerated and expressed as colony forming units (CFU)/100 mL. 

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