Microbial incidence in upper respiratory tracts of workers in the paper industry.

The incidence of microbes in the nasal cavities of workers in three paper and board mills was investigated. A total of 234 persons exposed to microbial aerosols and splashes from paper machine wires and debarker drums formed the exposed group. The control group consisted of 294 workers from the dry working areas: the winding and packing sections. Chi-square analysis was used to test the differences in the frequency of microbial incidence and various symptoms between the exposed and control groups. The nasal cavities of many workers, particularly workers in the debarkers, proved to be contaminated by Klebsiella pneumoniae, other coliforms, yeasts, and molds; usually only one microbe was involved, but sometimes two or several species were found. Nasal bacteria and yeasts were largely derived from the mill and debarker air; the microbes in the air came mainly from process waters. Lack of association of nasopharyngeal symptoms with either exposure to aerosols or nasal microbial contamination was interpreted as an indication of host defenses that were adequate to protect workers from harmful microbial colonization in paper mill environments.

Factors regulating the density of bacteria in process waters of a paper mill.

Variations in the numbers of total colonies of Klebsiella pneumoniae, Acinetobacter spp. and pseudomonads were investigated in process waters of a paper mill in southern Finland. Variations were related to independent parameters, namely temperature, pH, redox potential and production of offset paper, by using multiple regression analysis. Temperature was the most significant regressor variable and was negatively correlated with bacterial counts. It accounted for up to about 80% of the variance in bacterial counts in various parts of the process. The significance of temperature was due to its fluctuations in a critical range, above and below the maxima for bacterial growth. The pH level was also significant for total colony count and for K. pneumoniae. Redox potential and the production of offset paper were of significance for Acinetobacter spp. Washing the paper machine with water and lye decreased the numbers of bacteria in process waters.

Survival in lake water of Klebsiella pneumoniae discharged by a paper mill.

We investigated survival of Klebsiella pneumoniae in freshwater, by determining bacterial densities at eight temperatures between 0 and 20 degrees C at various distances from the discharge area in a lake receiving bacteria mainly from a paper mill. An mFC-inositol-carbenicillin-agar medium was used for Klebsiella enumeration by the membrane filter method. About 90% of the bacteria forming typical colonies on this medium were identified as Klebsiella species. About 10% of the bacteria were false positive, and, an equal percentage were false negative. Semilogarithmic plots of bacterial densities as a function of distance were found to be linear, with slopes depending on water temperature. The average velocity of the flow was estimated from the travel-of-bacterial-density minima caused by production stops. Regression equations were calculated for the dependence of death rate on temperature alone and on both temperature and discharge. The temperature coefficient (Q10) of the death rate was estimated to be 2.1 +/- 0.4. The decimal reduction time (T90) of K. pneumoniae at 0 degrees C was calculated to be about 24 days, and that at 20 degrees C was slightly over 5 days. The regression model was verified by independent observations. Factors affecting the reliability of the estimates were evaluated.

Effects of Environmental Factors on Microbial Populations in Brackish Waters off the Southern Coast of Finland.

The roles played by environmental factors in seasonal changes in microbial populations were investigated in the Tvärminne area, off the southern coast of Finland. Surface-layer samples were collected at 1- or 2-week intervals in 1976-78, and 14 microbiological and 10 environmental parameters were determined. Stepwise multiple regression analysis was used to explain seasonal variation in the microbiological parameters. Separate analyses were made of the data from the open-water and ice-cover periods. In analyses of data from both periods, the environmental factors included accounted for a significant proportion of the variation in the parameters for community respiration (90%) and bacterial spores (80%), and a smaller proportion (60 to 65%) of the variation in total counts of bacteria and plate counts of psychrophiles and yeasts. Lower values (40 to 55%) were obtained for the variation in the other microbiological parameters. The environmental factors with maximal contributions were organic matter, water temperature, chlorophyll a, and salinity, but rainfall and winds also explained part of the variation in some microbiological parameters. In the winter analysis the results differed from those obtained for the other seasons, the variation being governed by parameters indicating freshwater outflows, namely, humic matter, salinity, water temperature (positive regression coefficient), and rainfall (negative regression coefficient).

Factor analysis of the impact of the environment on microbial communities in the tvärminne area, southern coast of Finland.

Data already examined by regression analysis were subjected to factor analysis to scrutinize the effects of environmental factors on microbial populations in the brackish waters of the Tvärminne archipelago on the southern coast of Finland. Water samples were collected from 1.0-m depth at one point in Tvärminne Storfjärd, 71 times over about 2 years. Twenty-six parameters were determined on each sample, 10 of environmental and 16 of microbiological type. The correlations between the parameters were factorized using the principal axis solution, and eight factors chosen for further consideration were rotated by the varimax method. The major part of the variance (about 90% of the total communality) of the microbiological parameters was covered by five factors, interpreted as phytoplankton blooms, the periods before and after the blooms, freshwater outflows, and water temperature. Wind variables were components in the factors interpreted as freshwater outflows. Rainfall played a minor part in the total variance of the microbial community, but it washed yeasts and proteolytic bacteria from the land into the study area. The eight factors selected covered about 60 to 98% of the variance of the microbiological parameters. The highest values (above 90%) were obtained for direct counts of bacteria, for plate counts of mesophilic and polymyxin-resistant bacteria, and for the two community respiration parameters; the lowest values (60 to 75%) were obtained for H(2)S-producing and proteolytic bacteria.