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The objective of this study is to update evidence-based best practice guidelines for nursing in weight loss surgery (WLS). We performed a systematic search of English-language literature on WLS and perioperative nursing, postoperative, anesthesia, and discharge published between April 2004 and May 2007 in MEDLINE, CINHAL and the Cochrane Library. Key words were used to narrow the search for a selective review of abstracts, retrieval of full articles, and grading of evidence according to systems used in established evidence-based models. From these, we developed evidence-based best practice recommendations from the most recent literature on nursing in WLS. We identified >54 papers; the most relevant were reviewed in detail. Regular updates of evidence-based recommendations for best practices in WLS nursing are required to address advances in surgery and anesthesiology, as well as changes in the demographics and levels of obesity in WLS patients. Key factors in patient safety include staff education, comprehensive admission assessment, patient education, careful preoperative surveillance and postoperative care, and long-term discharge follow-up.

Habituation is one of the oldest forms of learning, broadly expressed across sensory systems and taxa. Here, we demonstrate that olfactory habituation induced at different timescales (comprising different odor exposure and intertrial interval durations) is mediated by different neural mechanisms. First, the persistence of habituation memory is greater when mice are habituated on longer timescales. Second, the specificity of the memory (degree of cross-habituation to similar stimuli) also depends on induction timescale. Third, we demonstrate a pharmacological double dissociation between the glutamatergic mechanisms underlying short- and long-timescale odor habituation. LY341495, a class II/III metabotropic glutamate receptor antagonist, blocked habituation only when the induction timescale was short. Conversely, MK-801, an N-methyl-D-aspartate (NMDA) receptor antagonist, prevented habituation only when the timescale was long. Finally, whereas short-timescale odor habituation is mediated within the anterior piriform cortex, infusion of MK-801 into the olfactory bulbs prevented odor habituation only at longer timescales. Thus, we demonstrate two neural mechanisms underlying simple olfactory learning, distinguished by their persistence and specificity, mediated by different olfactory structures and pharmacological effectors, and differentially utilized based solely on the timescale of odor presentation.

Some controversy still exists as to how binary odorant mixtures are behaviorally perceived, despite many studies aimed at understanding this phenomenon. Binary mixture perception by rodents is a first step in elucidating how more complex odor blends may be perceived. Research thus far has examined how the degree of component similarity, olfactory receptor overlap, relative concentration of components, and even olfactory enrichment affect the behavioral perception of binary mixtures. These studies have aimed to categorize binary mixtures into 1 of 3 rigid categories, but often the results conflict as to which category a particular mixture belongs. In the present article, the authors used a habituation/discrimination paradigm to determine whether rats' perception of one component of a binary mixture of either perceptually similar or dissimilar components changed when the concentration of both components was varied together. The authors found that perception of a binary mixture changed with changing component concentration, such that one binary mixture could be categorized differently depending on component intensity., ((PsycINFO Database Record (c) 2007 APA, all rights reserved).)

Fish in the family Mormyridae produce weak electric organ discharges that are used in orientation and communication. The peripheral and central anatomy of the electrosensory system has been well studied in the species Gnathonemus petersii, but comparative studies in other species are scarce. Here we report on one genus of mormyrid that displays a remarkable change in the electrosensory lateral line lobe (ELL), the hypertrophied rhombencephalic structure that receives primary electroreceptor input. Although all other mormyrids studied have three distinct zones on each side of the ELL, fish of the genus Stomatorhinus exhibit only two. Therefore, the two-zone ELL is a unique derived characteristic shared by Stomatorhinus. We examined the cutaneous electroreceptors that project to the ELL in Stomatorhinus. All three types of electroreceptors previously described for G. petersii were present, but there was a significant change in one type, the mormyromast. Both mormyromast sensory cell types (A- and B-cells) are present, but the B-cell is not innervated in Stomatorhinus. We conclude that, although all cutaneous sensory cells are present, the missing B-cell afferents account for the loss of the dorsolateral zone of the ELL, and therefore the loss of an entire sensory map. Because mormyromasts are involved in electrolocation behavior, this anatomical difference is probably related to differences in electrolocation abilities. Stomatorhinus could prove to be an excellent system for linking evolutionary changes in behavior with modifications in their neural substrates.

The olfactory bulb directly projects to several diverse telencephalic structures, but, to date, few studies have investigated the physiological characteristics of most of these areas. As an initial step towards understanding the odor processing functions of these secondary olfactory structures, we recorded evoked field potentials in response to lateral olfactory tract stimulation in vivo in urethane-anesthetized Sprague-Dawley rats in the following brain structures: anterior olfactory nucleus, ventral and dorsal tenia tecta, olfactory tubercle, anterior and posterior piriform cortex, the anterior cortical nucleus of the amygdala, and lateral entorhinal cortex. Using paired-pulse stimulation with interpulse intervals of 25-1000 ms, we observed facilitation of the response to the second pulse in every structure examined, although the degree of facilitation varied among the target structures. Additionally, pulse train stimulation at three different frequencies (40, 10 and 2 Hz) produced facilitation of evoked field potentials that also varied among target structures. We discuss the potential utility of such short-term facilitation in olfactory processing.

Purpose: To use evidence-based techniques to compare elective open surgical repair of abdominal aortic aneurysms with endovascular repair by means of stent placement., Materials and Methods: A focused clinical question formed the basis of a literature search. Evidence-based criteria were used to appraise and assign a "level of evidence" to retrieved articles. The following data were determined from the best studies: systemic, local, and/or vascular complications; graft failure rates; blood loss; mortality; length of intensive care and/or hospital stay; mid- and long-term outcomes; cost of endovascular repair versus that of surgery; and eligibility for endovascular repair. Absolute risk reductions and/or increases and numbers needed to treat or harm were calculated., Results: The best current evidence came from 22 studies, which showed that there is slight, if any, difference between mortality rates of endovascular repair and surgery. Hospital and/or intensive care stay is shorter, blood loss less, and systemic complications fewer (numbers needed to treat, two to 12) with endovascular repair. Some authors reported a significant increase in local and/or vascular complications with endovascular repair (numbers needed to harm, two to six). Graft failure is significantly more common with endovascular repair (numbers needed to harm, four), and substantive adjunctive interventions are needed. Endovascular repair is more expensive than surgery., Conclusion: Elective endovascular repair has short-term benefits compared with surgery. There is slight, if any, difference in mortality. Endovascular repair costs more than surgery. At follow-up, surgical grafts performed better.

We attempted to determine if women younger than 45 years of age who have isolated papillary thyroid cancer and whose tumors are smaller than 4 cm (T2N0M0) are at low risk for mortality and morbidity following thyroid lobectomy. To this end, we analyzed information on both women and men obtained from our review of the literature, and we integrated it with data compiled in the Delaware Cancer Registry. We performed a secondary analysis to determine if the risk of death and recurrence can be predicted on the basis of age, tumor size, sex, histology, and the type of operation. We found that among patients who had undergone either thyroid lobectomy or total thyroidectomy, mortality rates were 1.3% for those younger than 45 years of age and 15.6% for those 45 years and older (p < 0.0001). With respect to tumor size, patients whose masses were smaller than 4 cm had significantly lower mortality (3.0%) and recurrence (11.1%) rates than did those whose tumors were 4 cm or larger (16.8 and 33.3%, respectively; p < 0.0001). Other significant risk factors for death were male sex and the presence of follicular thyroid cancer (as opposed to papillary thyroid cancer). The risk of permanent hypocalcemia was significant among patients who had undergone total thyroidectomy, but not among those who had been treated with lobectomy. The subgroup of patients who had the lowest risk of mortality and morbidity was made up of women younger than 45 years years who had a papillary thyroid tumor smaller than 4 cm that was limited to one lobe and who had undergone lobectomy. On the other hand, we found that lobectomy might carry a higher risk of recurrence (from a micrometastasis in the cervical lymph node) than does total thyroidectomy. Experienced surgeons whose rates of hypocalcemia and recurrent laryngeal nerve paralysis following total thyroidectomy are low offer their patients the unambiguous advantage of superior follow-up with thyroglobulin and radioactive iodine.

A ground beef patty processor detected Escherichia coli O157:H7 in five production lots during routine testing with polymerase chain reaction (PCR) technology. This finding stimulated research to determine the incidence and potential entry points of the pathogen during processing. One of these lots (53,960 kg) was divided into 71 pallets (760 kg each) of food service ground beef patties. Ten cartons (19 kg each) were removed from each pallet, for a total of 710 cartons. Four patties were taken from each carton and subdivided to provide comparable samples for E. coli O157:H7 analyses by three different laboratories. Two laboratories employed different immunoassay tests, and one used PCR to screen samples. One sample set was analyzed for aerobic plate, coliform, and E coli Biotype I counts to determine if any relationship existed between these microbial groups and the incidence of E. coli O157:H7. For 73 samples, presumptive positive results for E. coli O157:H7 were obtained by one or more methods. For 48 of these 73 samples, positive results for the pathogen were culture confirmed. The largest number (29) of culture-confirmed positive E. coli O157:H7 results were detected by PCR. Most positive results were obtained during a short segment of processing. All culture-confirmed E. coli O157:H7 strains were further characterized by two genetic subtyping techniques, resulting in two to four different patterns, depending on the subtyping procedure employed. For any sample tested, the aerobic plate count was < 3.0 log CFU/g, and coliform and E. coli Biotype I counts were < or = 1.00 log CFU/g. The results of this study suggest that most positive samples were associated with a contaminated batch of raw material introduced just before the 1725- to 1844-h processing segment. These results also indicate that more aggressive sampling plans and genetic screening technologies such as PCR may be used to better detect low levels of E. coli O157:H7 in ground beef products.

Purpose: To examine use of chronic therapies by females and males of all ages., Methods: Participants were 1,295,948 members of a large US pharmacy benefit manager. The use of chronic medications by males and females during 1999 was examined overall and within 16 commonly-used chronic drug groups. Dependent variables were use of a drug group, number of drug groups used, number of prescriptions filled and sum of costs, both within each drug group and overall. Combination therapy was defined as using at least two of the 16 chronic therapy groups during 1999., Results: Females were more likely than males to use chronic medications during the study year (36.5 vs. 22.4%, p < 0.001). Generally, the likelihood of using a chronic medication increased with age for both sexes. Commonly-used chronic medications accounted for 54 and 50% of prescriptions for females and males respectively, and for 53% of total drug costs for both sexes. There were few meaningful sex differences in the likelihood of using particular drug groups. Of those who took chronic drugs 14% used combination chronic therapy., Conclusions: This study provides demographic information regarding treatment of chronic conditions that can be used to aid policy decisions and to provide an impetus for future research.

The inhibition of Listeria monocytogenes by sodium lactate and sodium diacetate was evaluated for wieners containing pork, turkey, and beef and for cooked bratwurst containing beef and pork. Both products were supplied by commercial manufacturers. Treated products were surface-inoculated with 10(5) CFU of L. monocytogenes per package and vacuum-packed in gas-impermeable pouches. Wieners were stored for 60 days at 4.5 degrees C, and bratwurst were stored for 84 days at 3 and 7degrees C. A surface treatment that consisted of dipping wieners into solutions containing < or = 6% lactate and < or = 3% diacetate for 5 s did not delay pathogen growth compared with that for untreated wieners. In additional trials, the antilisterial activity of lactate and diacetate in wiener and bratwurst formulations was evaluated. Lactate levels ranged from 1.32 to 3.4%, and diacetate was evaluated at 0.1 and 0.25%. The growth of L. monocytogenes was delayed for 4 and 12 weeks at 7 and 3 degrees C, respectively, on uncured, unsmoked bratwurst formulated with 3.4% lactate/0.1% diacetate, compared with 1 and 2 weeks, respectively, for the formulation containing 2% lactate. L. monocytogenes grew by > or = 1 log unit after 4 weeks' storage at 3 or 7 degrees C on cured, smoked bratwurst without lactate or diacetate, but growth was inhibited for 12 weeks on cured, smoked bratwurst formulated with 3.4% lactate and 0.1% diacetate. Sodium lactate levels of > or = 3% and combinations of > or = 1% lactate plus > or = 0.1% diacetate prevented listerial growth on wieners stored for 60 days at 4.5 degrees C. These results indicate that dipping wieners in lactate-diacetate solutions is not an efficient way to apply these antimicrobial agents to wieners. However, the inclusion of combinations of sodium lactate and sodium diacetate in wiener or bratwurst formulations inhibits the growth of L monocytogenes at < or = 7 degrees C, and an additional margin of safety was observed for products that are cured and smoked.

Objective: To report the top 15 prescription drug categories used by males and females of all ages and to compare this information with national prevalence data., Methods: Data used were pharmacy claim and eligibility information over the period January 1, 1999, through December 31, 1999, for 1,294,295 members of a large pharmacy benefit manager. Participant ages ranged from 1 to more than 100 years. Each participant was assigned to 1 of 9 age categories. Use of a drug category was defined as filling at least 1 prescription for a medication in that category during the study year. The percentage of males and females that used each drug group was established, and the 15 drug groups used most frequently were reported for each age category., Results: Most gender differences in medication use appear after or around the puberty years. Women are more likely to use several classes of medications, including antidepressants and antianxiety and pain medications. Except for diuretics, men use cardiovascular medications at an earlier age than do women. The use of medications for chronic conditions increases with older age categories for both genders. The use of female hormones represents only a small proportion of the difference in medication use between genders., Conclusions: Analysis of data from the epidemiologic literature suggests that the gender differences in medication use shown in this study generally are to be expected.

If raw meat and poultry are the primary point of entry for Salmonella species into human populations, a correlation might be expected between the serotype distribution of Salmonella species isolated from animals at the time of slaughter and that of isolates found in humans. For 1990-1996, sufficient national data were available to permit such a comparison. A mathematical model was developed to predict serotype distributions of Salmonella isolates among humans on the basis of animal data. There was a significant mismatch between the serotype distributions among humans predicted by the model and those actually observed. This mismatch raises questions about the validity of the "standard" assumptions about Salmonella transmission on which the model was based-namely, that raw animal products are the primary source for human salmonellosis, that the risk of transmission to humans is equal for all food product categories, and that all Salmonella serotypes have an equal ability to cause human illness.

The advent of transvaginal sonography has improved the ability of radiologists to visualise both ovaries and has facilitated the preoperative characterisation of many of these lesions. We describe the beneficial role of transvaginal sonography in the accurate preoperative characterisation of dermoid cysts of the ovary in two patients and describe the characteristic features of ovarian dermoid cysts.

The isolation rate for Salmonella enterica serotype Enteritidis (SE) in humans in the United States of America (USA) increased from 1,207 sporadic isolates identified in 1976 (0.6 isolates/100,000 population) to 10,201 identified in 1995 (4.0/100,000 population). The proportion of reported Salmonella isolates which were SE increased from 5% to 25% during the same time period. In 1990, 1994, and 1995, SE was the most commonly reported reported Salmonella serotype in the USA. Much of this increase has been associated with the consumption of contaminated shell eggs. An examination of the results of a United States Department of Agriculture (USDA) survey of spent hens at slaughter and unpasteurised liquid egg at breaker plants (liquid egg processors) in 1991 and 1995 reveals an increase in the prevalence of SE isolates overall and in most regions of the USA. SE phage type 4 (pt 4), the predominant SE phage type in other parts of the world, has emerged in the egg industry in the western USA concurrent with a sharp increase in the number of sporadic human SE pt 4 isolates in California and Utah. Research on the molecular structure and virulence of SE pt 4 isolates from the USA as compared with isolates from other parts of the world (human and poultry) should be a priority. A comparison of DNA from pt 4 isolates from the USA and Europe may provide information about the potential threat to public health and poultry in the USA from this phage type. Some regional success in the reduction of human illness as a result of SE control efforts is apparent. The Pennsylvania Egg Quality Assurance Program has shown progress in reducing SE infection in participating flocks. At a national level, however, neither the incidence of human illness due to SE nor the prevalence of SE in flocks and unpasteurised liquid eggs have decreased significantly, despite the implementation of the USDA 'trace back' regulation from 1990 to 1995, and intensified efforts to educate food handlers and to enforce safe food handling practices. More effort is needed to control SE at every stage of the egg continuum, from production through to consumption. A risk-reduction approach, with barriers to the introduction and multiplication of the pathogen throughout the farm-to-table continuum, is the most practical method for reducing human illness from SE in shell eggs at present. An effective long-term solution will require interdisciplinary efforts involving government, industry, consumers, and academics. Interventions should be developed and evaluated in compliance with the potential for reducing the risk to human health and cost-effectiveness.

Objectives: This study sought to determine whether a multistate fast food hamburger-associated outbreak of Escherichia coli O157:H7 infection involved Las Vegas residents as well and, if so, why public health officials had not detected it., Methods: A matched case-control study was conducted among persons with bloody diarrhea and their healthy meal companions. Hamburger production, distribution, and cooking methods were reviewed. Unused hamburger patties were cultured, and E. coli O157:H7 isolates were characterized. Local laboratory stool culture practices were reviewed., Results: Fifty-eight cases of bloody diarrhea were identified. Illness was associated with eating regular hamburgers (matched odds ratio [OR] = 9.0, 95% confidence interval [CI] = 1.02,433.4), but 25% of ill persons reported eating only jumbo hamburgers. Regular and jumbo hamburger patties yielded E. coli O157:H7 indistinguishable from the lone clinical isolate. No local laboratory cultured routinely for E. coli O157:H7 until after the outbreak., Conclusions: A large outbreak of E. coli O157:H7 infections escaped timely notice in Las Vegas because local laboratories did not culture for this pathogen. Health officials should encourage laboratories to screen at least all bloody stools on sorbitol-MacConkey medium.

Purpose: To introduce the symptom interpretation model (SIM) and facilitate understanding symptoms from an intrapersonal perspective. Determining an individual's interpretation of symptoms is critical to understanding the resulting decisions., Organizing Construct: SIM is based on an illness representation model, knowledge structures theory, and propositions about reasoning. Individuals name and assign meaning to environmental stimuli. Based on this interpretation, behaviors are selected for symptom management., Methods: Theory derivation was used to develop SIM for understanding comparisons of known and new symptoms in a behavioral outcomes context., Conclusions: Symptom familiarity reinforces patterns about symptom management. SIM enriches understanding of symptom experiences. Comprehensive assessment, including the intraindividual perspective, is essential to successful symptom management.

Objectives: This study evaluated the production of dry fermented salami associated with an outbreak of Escherichia coli O157.H7 infection in Washington State and California., Methods: Facility inspections, review of plant monitoring data, food handler interviews, and microbiological testing of salami products were conducted., Results: Production methods complied with federal requirements and industry-developed good manufacturing practices. No evidence suggested that postprocessing contamination occurred. Calculations suggested that the infectious dose was smaller than 50 E. coli O157:H7 bacteria., Conclusions: Dry fermented salami can serve as a vehicle of transmission for O157:H7 strains. Our investigation and prior laboratory studies suggest that E. coli O157:H7 can survive currently accepted processing methods.

The current Food Safety and Inspection Service method for detection and recovery of Escherichia coli O157:H7, (including modified EC broth with novobiocin (mEC+n) and a direct blot ELISA). was used to analyze beef and environmental samples during an investigation of a food-borne disease outbreak attributed to consumption of undercooked hamburger patties. Double-modified trypticase soy broth (dmTSB) and a commercially available dipstick immunoassay were also used to improve detection/recovery of E. coli O157:H7. A total of 1,115 beef and environmental samples was screened with the direct blot ELISA and the dipstick immunoassay; 178 presumptive-positive samples (by either or both of the screening methods) were subjected to recovery/isolation procedures. Toxigenic E. coli O157:H7 was recovered from 45 samples: 40 hamburger-patty samples produced on the epidemiologically identified date, 3 hamburger-patty samples produced on another date, and 2 beef briskets. The organism was not recovered from environmental samples. Limited quantitative analyses indicated that contaminated hamburger patties contained fewer than 4.3 CFU of E. coli O157:H7 per g. Atypical, toxigenic ornithine decarboxylase-negative E. coli O157:H7 and nontoxigenic sorbitol-positive E. coli O157:H29 were also recovered. Both enrichment broths gave strong positive reactions with the two immunoassay screening methods, but E. coli O157:H7 was recovered more often from mEC+n broth than from dmTSB. Both screening methods gave positive results for 44 of the 45 beef samples found to contain E. coli O157:H7. False-positive results were frequently observed with both screening methods.

A study was conducted to compare the susceptibility of legionellae and coliforms to disinfection by chlorine. The chlorine residuals used were similar to concentrations that might be found in the distribution systems of large public potable water supplies. The effects of various chlorine concentrations, temperatures, and pH levels were considered. A number of different Legionella strains, both environmental and clinical, were tested. The results indicate that legionellae are much more resistant to chlorine than are coliform bacteria. At 21 degrees C, pH 7.6, and 0.1 mg of free chlorine residual per liter, a 99% kill of L. pneumophila was achieved within 40 min, compared with less than 1 min for Escherichia coli. The observed resistance is enhanced as conditions for disinfection become less optimal. The required contact time for the removal of L. pneumophilia was twice as long at 4 degrees C than it was at 21 degrees C. These data suggest that legionellae can survive low levels of chlorine for relatively long periods of time.

Previous studies have shown that bacteria maintained in a low-nutrient "natural" environment such as swimming pool water are much more resistant to disinfection by various chemical agents than strains maintained on rich media. In the present study a comparison was made of the chlorine (Cl2) susceptibility of hot-water tank isolates of Legionella pneumophila maintained in tap water and strains passaged on either nonselective buffered charcoal-yeast extract or selective differential glycine-vancomycin-polymyxin agar medium. Our earlier work has shown that environmental and clinical isolates of L. pneumophila maintained on agar medium are much more resistant to Cl2 than coliforms are. Under the present experimental conditions (21 degrees C, pH 7.6 to 8.0, and 0.25 mg of free residual Cl2 per liter, we found the tap water-maintained L. pneumophila strains to be even more resistant than the agar-passaged isolates. Under these conditions, 99% kill of tap water-maintained strains of L. pneumophila was usually achieved within 60 to 90 min compared with 10 min for agar-passaged strains. Samples from plumbing fixtures in a hospital yielded legionellae which were "super"-chlorine resistant when assayed under natural conditions. After one agar passage their resistance dropped to levels of comparable strains which had not been previously exposed to additional chlorination. These studies more closely approximate natural conditions than our previous work and show that tap water-maintained L. pneumophila is even more resistant to Cl2 than its already resistant agar medium-passaged counterpart.

Earlier field and laboratory studies have shown that Legionella species survive and multiply in the pH range 5.5 to 9.2. Additionally, the technical feasibility of operating cooling towers at elevated alkalinities and pH has previously been documented by published guidelines. The guidelines indicate that these conditions facilitate corrosion control and favor chlorine persistence which enhances the effectiveness of continuous chlorination in biofouling control. This information suggests that control of Legionella species in cooling towers can be accomplished by operating the towers under alkaline conditions. To test this possibility, we collected water samples over a period of months from a hospital cooling tower. The samples were analyzed for a variety of chemical parameters. Subsamples were pasteurized and inoculated with non-agar-passaged Legionella pneumophila which had been maintained in tap water. Correlation of subsequent Legionella growth with corresponding pH and alkalinity values revealed statistically significant inverse associations. These data support the hypothesis that operating cooling towers outside of the optimal conditions for Legionella growth (e.g., at elevated alkalinities and a pH greater than 9) may be a useful approach to controlling growth in this habitat.

Studies were conducted to investigate the survival and multiplication of Legionella spp. in public drinking water supplies. An attempt was made, over a period of several years, to isolate legionellae from a municipal system. Sampling sites included the river water supply, treatment plant, finished water reservoir system, mains, and distribution taps. Despite the use of several isolation techniques, Legionella spp. could not be detected in any of the samples other than those collected from the river. It was hypothesized that this was due to the maintenance of a chlorine residual throughout the system. To investigate the potential for Legionella growth, additional water samples, collected from throughout the system, were dechlorinated, pasteurized, and inoculated with Legionella pneumophila. Subsequent growth indicated that many of these samples, especially those collected from areas affected by an accumulation of algal materials, exhibited a much greater ability to support Legionella multiplication than did river water prior to treatment. Chemical analyses were also performed on these samples. Correlation of chemical data and experimental growth results indicated that the chemical environment significantly affects the ability of the water to support multiplication, with turbidity, organic carbon, and certain metals being of particular importance. These studies indicate that the potential exists for Legionella growth within municipal systems and support the hypothesis that public water supplies may contaminate the plumbing systems of hospitals and other large buildings. The results also suggest that useful methods to control this contamination include adequate treatment plant filtration, maintenance of a chlorine residual throughout the treatment and distribution network, and effective covering of open reservoirs.

A water culture containing naturally occurring Legionella pneumophila and associated microbiota was maintained in the laboratory by serially transferring the culture in tap water which had been sterilized by membrane filtration. Successful maintenance of the water culture depended upon transferring the culture when the growth of L. pneumophila was in the late-exponential to early-stationary phase. The water culture was used as a source of naturally occurring bacteria to determine some of the parameters which affect the multiplication of L. pneumophila in tap water. Naturally occurring L. pneumophila multiplied at a temperature between 25 and 37 degrees C, at pH levels of 5.5 to 9.2, and at concentrations of dissolved oxygen of 6.0 to 6.7 mg/liter. Multiplication did not occur in tap water which contained less than 2.2 mg of dissolved oxygen per liter. An association was observed between the multiplication of L. pneumophila and the non-Legionellaceae bacteria which were also present in the water culture. The method of preserving naturally occurring L. pneumophila and associated microbiota may facilitate studies on the symbiosis of L. pneumophila with other microorganisms.

An investigation of the chemical environment and growth of Legionella pneumophila in plumbing systems was conducted to gain a better understanding of its ecology in this habitat. Water samples were collected from hospital and institutional hot-water tanks known to have supported L. pneumophila and were analyzed for 23 chemical parameters. The chemical environment of these tanks was found to vary extensively, with the concentrations of certain metals reaching relatively high levels due to corrosion. The effect of various chemical conditions on L. pneumophila growth was then examined by observing its multiplication in the chemically analyzed hot-water tank samples after sterilization and reinoculation with L. pneumophila. L. pneumophila and associated microbiota used in these experiments were obtained from a hot-water tank. These stains were maintained in tap water and had never been passaged on agar. The results of the growth studies indicate that although elevated concentrations of a number of metals are toxic, lower levels of certain metals such as iron, zinc, and potassium enhance growth of naturally occurring L. pneumophila. Parallel observations on accompanying non-Legionellaceae bacteria failed to show the same relationship. These findings suggest that metal plumbing components and associated corrosion products are important factors in the survival and growth of L. pneumophila in plumbing systems and may also be important in related habitats such as cooling towers and air-conditioning systems.