Survival and detection of bacteria in an aquatic environment.

A genetically engineered plasmid, pPSA131, was used as a DNA probe to detect homologous DNA in Escherichia coli HB101(pPSA131) after it was mixed with aquatic microorganisms from Lake Mead, Nevada, water samples. An isolate from the pLAFR1 chromosomal library of Pseudomonas syringae Cit 7 was used to detect parent P. syringae Cit 7 that had been mixed with Lake Mead water. E. coli(pPSA131) was kept in variously treated samples of lake water or buffer, and its survival was measured by viable cell counting on modified Luria-Bertani (LB) agar. Full-strength LB agar proved better than 0.1 x LB agar at recovering E. coli(pPSA131) after survival in low-nutrient environments. Survival of E. coli(pPSA131) remained high in filtered (0.22-micron pore size) lake water and salts buffer on both selective and nonselective agars but was lower in untreated lake water or lake water filtered with a 0.8-micron-pore-size membrane. Total recoverable colonies grown on LB agar were higher when lake water was filter treated (0.8-micron pore size) than when lake water was untreated. Microorganisms recovered from lake water alone grew rapidly on nonselective media, probably because of the "bottle effect." After being mixed with Lake Mead water, E. coli(pPSA131) and P. syringae were detected by colony blotting with non-radioactively labeled DNA probes. E. coli(pPSA131) were recovered at three times during 48 h from variously treated samples of lake water and from a mixture with Lake Mead water organisms. Colonies were supported on either nonselective or selective agar for comparison.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of needle purging in reducing transfer of microorganisms from local anesthetic cartridge diaphragms.

The literature is reviewed to demonstrate the significant amount of contamination on the external surface of the anesthetic cartridge diaphragm. Current methods of cartridge diaphragm decontamination to prevent injection of pathogens are discussed. A series of bacteriologic tests were conducted to determine the probability of transfer of pathogens from the diaphragm surface through the needle lumen of three different sizes to the deposition site. Results of needle purging suggest that a significant reduction in the transfer of microorganisms is possible using this technique.