Biofilm formation is a well-known problem in management of metalworking fluid systems. Due to persistence of microorganisms within biofilms, the reappearance of various species of bacteria, including nontuberculous mycobacteria is often observed after the use of biocides and/or cleaning of delivery systems and replacement of cooling fluid. The aim of this study was to determine the usefulness of the tetrazolium salt assay (MTT assay) for assessing the viability of bacteria in biofilms formed in vitro in fresh and used cutting oils, as well as their susceptibility to antimicrobial biocides. Biofilms were established in the microtiter plate format. The results showed that quantification of formazan, a product of the tetrazolium salt reduction by electron transport system could be used for determination of the propensity of bacteria to form biofilms in these complex media. The use of the assay allows also determination of antimicrobial activity of biocides against biofilms in fresh and used metalworking fluids. Biofilms produced by Gram-negative isolates recovered from field metalworking fluids as well as the wild bacterial communities differed in metabolic activity depending on the type of fresh coolants. The MTT assay has high-throughput potential and can be efficiently used for determination of biofilm-forming capacity of microorganisms from individual machines in metalworking industry. The use of the assay may also guide the selection of the most appropriate biocide to fight these microorganisms.

The present study had three goals: (i) to evaluate the relative quantities of aerosolized Bacillus atrophaeus spores deposited on the vertical, horizontal top, and horizontal bottom surfaces in a chamber; (ii) to assess the relative recoveries of the aerosolized spores from glass and stainless steel surfaces with a polyester swab and a macrofoam sponge wipe; and (iii) to estimate the relative recovery efficiencies of aerosolized B. atrophaeus spores and Pantoea agglomerans using a foam spatula at several different bacterial loads by aerosol distribution on glass surfaces. The majority of spores were collected from the bottom horizontal surface regardless of which swab type and extraction protocol were used. Swabbing with a macrofoam sponge wipe was more efficient in recovering spores from surfaces contaminated with high bioaerosol concentrations than swabbing with a polyester swab. B. atrophaeus spores and P. agglomerans culturable cells were detected on glass surfaces using foam spatulas when the theoretical surface bacterial loads were 2.88 ؋ 10 4 CFU and 8.09 ؋ 10 6 CFU per 100-cm 2 area, respectively. The median recovery efficiency from the surfaces using foam spatulas was equal to 9.9% for B. atrophaeus spores when the recovery was calculated relative to the theoretical surface spore load. Using a foam spatula permits reliable sampling of spores on the bioaerosol-exposed surfaces in a wide measuring range. The culturable P. agglomerans cells were recovered with a median efficiency of 0.001%, but staining the swab extracts with fluorescent dyes allowed us to observe that the viable cell numbers were higher by 1.83 log units than culturable organisms. However, additional work is needed to improve the analysis of the foam extracts in order to decrease the limit of detection of Bacillus spores and Gram-negative bacteria on contaminated surfaces.Surface sampling is performed on a frequent basis in all situations where clean environment monitoring is needed, e.g., in health care facilities and in the pharmaceutical industry and food industry. An anthrax bioterrorist event in the fall of 2001 has emphasized the importance of efficient sampling methods for detection of pathogenic microorganisms on surfaces within intentionally contaminated locations (22). Unfortunately, our knowledge on the most effective sampling methodology as well as the level of confidence we may have in the results obtained by wiping, swabbing, and other sample collection strategies is still limited (1). Moreover, in most of the studies performed so far, bacteria and/or spores were collected from test samples or coupons of various materials, inoculated with a suspension of microorganisms that had been placed and spread over the surface, and then dried (14, 15). This may not mimic the true situation of surface contamination by a pathogen that has been intentionally released. Edmonds et al. (12) recently reported lower swabbing efficiencies of different types of swab materials used for sampling glass, polycarbonate, and vinyl surfaces contaminat...

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I n the titration of sulphate ions with lead(I1) perchlorate solution using a lead-sensitive electrode for end-point determination, the addition of 75% V / V of methanol permits titration of M samples. Under these conditions, a 200-fold excess of nitrate does not interfere, but chloride a t this concentration introduces a small systematic error of 4%. Significant errors are caused by the presence of calcium, which co-precipitates as calcium sulphate with lead sulphate. In titrations carried out rapidly, the negative error increases with the amount of calcium and the true equilibrium may be obtained after a relatively long time. Increasing the ionic strength of the solution by addition of sodium perchlorate eliminates the interference by calcium, but for concentrations of sulphate below M it is advantageous to remove calcium by using a cation-exchange resin in the hydrogen form.The method has been applied successfully to the determination of sulphate in water.Methods for the determination of sulphates in waters, in the range from 4 x M,

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