Accumulation Of Microorganisms Research Articles

Enhancement factor for oxygen absorption into fermentation broth

AbstractValues of the enhancement factor for oxygen absorption into fermentation broth, i.e., the ratio of the liquid phase mass transfer coefficients for oxygen absorption for both cases with and without respiration of microorganisms were predicted theoretically on the assumption of various cell concentration distributions. Calculations indicate that in the usual case the enhancement factor is only slightly or negligibly larger than unity, even when accumulation of microorganisms at or near the gas‐liquid interface is assumed. Results of experiments with sparged‐stirred fermentors on oxygen absorption into fermentation broths containing resting and growing cells of Candida tropicalis confirmed the theoretical prediction. Except for extreme cases, the effect of respiration of microorganisms on kLa, values can practically be ignored.

The alveolar macrophage and its role in toxicology.

As a pulmonary cell and as a member of a multisystemic family of mononuclear phagocytes, the alveolar macrophage contributes not only to the maintenance of pulmonary homeostasis but also constitutes a vital link in the general systemic defensive chain. In this review, the role of the macrophage as the ultimate scavenger of the respiratory tree is explored in the context of the variety of environmental and other agents that may disturb this function and thereby injure the host. Analysis of these factors suggests that under conditions of increased inhalant load the macrophagic response is, in most instances, completely adequate to keep the air sacs free from injurious particles and microorganisms. Disturbances of the clearance mechanism induced by toxic injury or overloading of the macrophage may, by permitting the accumulation of harmful chemicals and microorganisms in the lung, contribute to the development of several chronic pulmonary diseases that are associated with our urban-industrial society.

Microbiological evaluation of the vacuum probe surface sampler.

The development of the vacuum probe, a new device for surface sampling, was recently reported. The original technique was slightly modified and a microbiological evaluation was conducted. The probe proved to be an effective sampling device, removing 98% and recovering 88% of surface contaminants resulting from the accumulation of airborne microorganisms. The probe was decidedly less effective in removing and recovering handling contamination than fallout contamination. There was also evidence that certain microorganisms could not survive prolonged exposure to airflow in the probe. However, the vacuum probe procedure recovered twice as many microorganisms as did the swab-rinse technique when compared directly.

Microbiological Evaluation of the Vacuum Probe Surface Sampler

The development of the vacuum probe, a new device for surface sampling, was recently reported. The original technique was slightly modified and a microbiological evaluation was conducted. The probe proved to be an effective sampling device, removing 98% and recovering 88% of surface contaminants resulting from the accumulation of airborne microorganisms. The probe was decidedly less effective in removing and recovering handling contamination than fallout contamination. There was also evidence that certain microorganisms could not survive prolonged exposure to airflow in the probe. However, the vacuum probe procedure recovered twice as many microorganisms as did the swab-rinse technique when compared directly.

Comparative levels and types of microbial contamination detected in industrial clean rooms.

The primary objective of this study was to determine quantitatively and qualitatively the predominant types of microbial contamination occurring in conventional and laminar flow clean rooms. One horizontal laminar flow, three conventional industrial clean rooms, and three open factory areas were selected for microbiological tests. The results showed that as the environment and personnel of a clean room were controlled in a more positive manner with respect to the reduction of particulate contamination, the levels of airborne and surface microbial contaminants were reduced accordingly. The chief sources of microbial contamination were associated with the density and activity of clean room personnel. In addition, the majority of microorganisms isolated from the intramural air by air samplers were those indigenous to humans. Studies on the fallout and accumulation of airborne microorganisms on stainless-steel surfaces showed that, although there were no significant differences in the levels of microbial contamination among the conventional clean rooms, the type of microorganism detected on stainless-steel surfaces was consistently and significantly different. In addition, the "plateau phenomenon" occurred in all environments studied. It was concluded that the stainless-steel strip method for detecting microbial accumulation on surfaces is efficient and sensitive in ultra-clean environments and is the most reliable and practical method for monitoring microbial contamination in future class 100 clean rooms to be used for the assembly of spacecraft which will be sterilized.

Comparative Levels and Types of Microbial Contamination Detected in Industrial Clean Rooms

The primary objective of this study was to determine quantitatively and qualitatively the predominant types of microbial contamination occurring in conventional and laminar flow clean rooms. One horizontal laminar flow, three conventional industrial clean rooms, and three open factory areas were selected for microbiological tests. The results showed that as the environment and personnel of a clean room were controlled in a more positive manner with respect to the reduction of particulate contamination, the levels of airborne and surface microbial contaminants were reduced accordingly. The chief sources of microbial contamination were associated with the density and activity of clean room personnel. In addition, the majority of microorganisms isolated from the intramural air by air samplers were those indigenous to humans. Studies on the fallout and accumulation of airborne microorganisms on stainless-steel surfaces showed that, although there were no significant differences in the levels of microbial contamination among the conventional clean rooms, the type of microorganism detected on stainless-steel surfaces was consistently and significantly different. In addition, the "plateau phenomenon" occurred in all environments studied. It was concluded that the stainless-steel strip method for detecting microbial accumulation on surfaces is efficient and sensitive in ultra-clean environments and is the most reliable and practical method for monitoring microbial contamination in future class 100 clean rooms to be used for the assembly of spacecraft which will be sterilized.

Patterns of accumulation resulting from taxes and changes in motility of micro-organisms.

An analysis is made of the development of patterns of accumulation of micro-organisms, as governed by tactic responses, changes in motility, and the effects of diffusion. When a soluble crystal is placed in a suspension of micro-organisms, the first manifestation is the development of a clear zone surrounding the crystal. This effect is a physical one, produced by a transfer of momentum from the solute molecules to the organisms. As the solute spreads and its boundary moves more slowly, the organisms are distributed in patterns which depend upon the occurrence of tactic responses and the influence of the solute upon motility. A congregation in the zone occupied by the solute can correspond either to a positive chemotaxis or to an inhibition of motility by the solute. Conversely, a withdrawal from the solute can signal either a negative chemotaxis or an enhancement of motility by the solute. The proper interpretation of the patterns described in Figs. 10 and 11 requires a microscopic study of individual organisms, in which the effect of the reagent upon motility is noted.