Ingestion of Yersinia pseudotuberculosis into human fibroblasts in vitro.

The ingestion into human fibroblasts of different strains (avirulent and virulent) of Yersinia pseudotuberculosis was investigated. The kinetics of ingestion was studied with the addition of 10(7) bacteria to human lung fibroblast cultures. The number of ingested bacteria after 0.5-3 h was measured with viable count technique. All strains were ingested except for one avirulent strain. The other strains were ingested at roughly the same rate. The bacterial uptake seemed to be mediated by a phagocytic-like procedure and the intracellular bacteria resided in vacuoles. The bacteria survived and also multiplied in the cells (for at least 7 days).

Long-range air transmission of bacteria.

Bacterial spores from a sandstorm area north of the Black Sea were transmitted to Sweden by air, giving increased concentrations of viable bacterial spores at two air sampling stations in Sweden.

Three-year investigation of the natural airborne bacterial flora at four localities in sweden.

The concentration of airborne bacteria was recorded during a period of 3 years at four localities: (i) in an agricultural district with an average of 99 (range, 2 to 3,400) bacteria per m3; (ii) in a coastal area with an average of 63 (range, 0 to 560) bacteria per m3; (iii) in a city park with an average of 763 (range, 100 to 2,500) bacteria per m3; and (iv) in a city street with an average of 850 (range, 100 to 4,000) bacteria per m3. At all four localities the bacterial concentrations varied within broad limits, but an annual periodicity with high average counts found during summer and autumn could be seen. The influence of certain meteorological factors on the number of airborne bacteria is also reported. Rain or high relative humidity caused a decrease in the bacterial counts, while high temperature or high wind velocities increased the counts. The particle size distribution for the four localities showed that about 50% of the particles carrying bacteria were larger than 8 micrometer.

Increased extracellular production of a cholinesterase-solubilising factor by Cytophaga NCMB 1314 during magnesium starvation.

A Cytophaga sp. with the property of liberating a cholinesterase which is found in body muscle of plaice was studied. The liberation was caused by a factor of which more than 90% was found outside the bacterial cell and might possibly be associated within the slime material surrounding the bacteria. Magnesium limitation during growth of Cytophaga sp. in batch cultures resulted in an about 10-fold increase in extracellular factor activity. The increase could be immediately stopped by addition of magnesium ions or chloramphenicol to the medium. The effect of the latter might indicate that the increase in factor activity is dependent on protein synthesis under magnesium-limiting conditions.

Surface-decontaminating action of glutaraldehyde in the gas-aerosol phase.

The surface disinfectant effect of glutaraldehyde in the gas-aerosol phase was investigated at different relative humidities and temperatures. At a gas-aerosol concentration of 15 to 20 mg/m3 and a relative humidity of about 80%, glutaraldehyde had a good disinfectant effect against both vegetative bacteria (decimal reduction time, less than 5 min) and bacterial spores (decimal reduction time, less than 45 min). In spite of its low volatility, glutaraldehyde was more effective than formaldehyde when the two substances were compared on an "added amount" basis.

Ingestion and survival of Y. pseudotuberculosis in HeLa cells.

HeLa cells were infected with Yersinia pseudotuberculosis for 0.5-3 h. Intracellular bacteria could then be demonstrated by three different techniques: viable count, fluorescent-antibody staining and electron microscopy. Most of the bacteria seemed to be viable, since there was a good positive correlation (0.94) between viable and fluorescent bacteria. The bacterial uptake seemed to be mediated by a phagocytic-like procedure. The intracellular bacteria seemed to reside in vacuoles some of which increased in size as a function of time. The kinetics of infection was studied after addition of 10(7) or 10(9) bacteria per cell culture (2 X 10(6) cells). After a lag period of about 30 min there was a linear increase of intracellular bacteria, and this uptake proceeded for 1-2 h until most of the bacteria were ingested or an upper limit of ingested bacteria was reached. The upper limit was calculated to be a mean of 60 per infected cell in the cell culture. More than 90% of the cells could be infected and a reasonable number of the bacteria survive in the cells for at least 3 days, as demonstrated by the viable-count technique. The bacteria-cell system may be used to study, for example, the effect of antibiotics or antibodies on intracellular bacteria and pathogenicity of intracellular diseases.

Variations in the metal content of some commercial media and their effect on microbial growth.

The cation content in commercial media obtained from two manufacturers showed considerable variation. Even different batches of the same make were found to be inconsistent in the content of metal ions. With cultures of Cytophaga sp. and Yersinia pseudotuberculosis in base media, growth stimulation was dependent on additions of certain commercial media. It could be demonstrated that this stimulation was derived solely from increased Mg(2+) concentration in the media.