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Shortly after installation of the service and performance heat exchanger (SPCU HX) in 2001, samples collected from the coolant fluid indicated the presence of nickel accompanied by a subsequent decrease in phosphate concentration along with a high microbial load. When the SPCU HX was replaced and evaluated post-flight, it was expected that the heat exchanger would have significant biofilm and corrosion present given the composition of the coolant fluid; however, there was no evidence of either. Early results from two experiments imply that the heat exchanger materials themselves are inhibiting biofilm formation. This paper discusses the results of one set of experiments and puts forward the inhibition of quorum sensing as a possible mechanism for the lack of biofilm formation.

A flex hose assembly containing aqueous coolant from the International Space Station (ISS) Internal Active Thermal Control System (IATCS) consisting of a 2 foot section of Teflon hose and quick disconnects (QDs) and a Special Performance Checkout Unit (SPCU) heat exchanger containing separate channels of IATCS coolant and iodinated water used to cool spacesuits and Extravehicular Mobility Units (EMUs) were returned for destructive analyses on Shuttle return to flight mission STS-114. The original aqueous IATCS coolant used in Node 1, the Laboratory Module, and the Airlock consisted of water, borate (pH buffer), phosphate (corrosion control), and silver sulfate (microbiological control) at a pH of 9.5 ± 0.5.

Long-term space flight missions will require high quality water to lessen the risk of crew infections and system deterioration. In water systems on earth, biofilms contribute to loss of water quality, causing corrosion, increased flow resistance and reduced heat transfer. Some bacteria grow more rapidly and become less susceptible to antimicrobial agents under conditions of microgravity, and humans may have weakened immunity with prolonged space flight. This study aimed to determine the effects of spaceflight and microgravity on biofilm formation by Burkholderia cepacia in water and microbial control by iodine. The results showed that B. cepacia formed biofilms when incubated in microgravity and in ground controls. Compared to rich medium or water, biofilms developed at similar densities in iodinated water.

Drinking water aboard spacecraft and on earth must be monitored to ensure that harmful bacteria are absent. NASA needs rapid methods for this purpose, to avoid possible launch delays and limit potential water-related health risks aboard spacecraft on orbit. Determination of bacterial viability after exposure to disinfection has significant health importance since oxidatively injured pathogenic bacteria have been shown to retain their virulence. This problem is compounded by the observation that injured bacteria are recovered at significantly lower frequencies using standard agar plate assays, leading to an underestimation of infection risks. Escherichia coli O157:H7 was exposed to 0.5 ppm free chlorine, retained on membrane filters and tested for physiological activity using a variety of assays.

Water is a critical commodity for spacecraft crews, requiring extreme conservation and reclamation strategies. In addition to suppression of the immune system in spaceflight, enhancement of bacterial growth and antimicrobial resistance in weightlessness raise serious concerns regarding microbial contamination of water systems. Rapid methods are needed for monitoring water, both pre-flight and on orbit. We are developing techniques to enumerate specific, metabolically active bacteria that may threaten crew health or lead to water system deterioration. Our methods are directed at the detection of individual bacteria, rather than populations of bacteria, and we aim to determine the identity of the organism as well as its physiological state con-currently. Our objectives are to determine, in a single test, the total number of bacteria present in a water sample, if a specific strain of bacteria is present within the total population and if these bacteria are viable or dead.

NASA-Marshall Space Flight Center (MSFC) has an interest in an automated in-line monitor that can detect the presence of microbial contamination in recovered water. Ideally, this system should also be able to identify and enumerate the microbial contaminant. The Viable Microbial Monitor (VM2) is based on conductance microbiology which depends on the well documented ability of microorganisms to change the electrochemical properties of their growth medium during incubation. The VM2 is intended for the rapid detection of bacterial or fungal contamination in water and other samples. From October 1992 to July 1993, NASA-MSFC sponsored a Microbial In-line Monitor (MIM) study to evaluate the VM2 for its ability to detect ten microorganism species (9 bacteria and 1 yeast) recovered from Water Recovery Tests (WRT) conducted at MSFC. These WRT isolates may represent the microbes that have potential to contaminate a water recovery system.

To determine the microbiological quality of water for potable and other purposes, there is a need for rapid methods to enumerate viable bacteria. This is of particular importance for the proposed water recovery systems planned for the United States Space Station, in which wastewaters including hygiene water and urine will be reclaimed for potable use. Existing microbiological culture methods are limited by the time taken to obtain results and because it is not possible to detect the total microbial populations by these methods. We have been investigating direct microscopic methods which detect individual bacterial cells. Fluorogenic compounds are used which are taken up by active cells, permitting a direct assessment of physiological activity. The methods are being adapted for use with membrane filtration which permits concentration of small numbers of cells from large volumes of water. Procedures for direct examination of cells growing on surfaces as biofilms have also been devised.

Early detection of microbial contaminants in reclaimed water was investigated using conductivity measurements of cultured samples. Culture data were obtained by using conductivity electronics and a personal computer equipped with an analog-digital converter and multiplexer. The software was programmed to monitor 54 cultures. The cultures were incubated for up to 48 hours at 35°C. The real-time conductivity data obtained from these cultured samples produces curves comprised of multiple data points over time. Using laboratory cultures for conductivity measurements, growth was detected within 12-24 hours with inocula in the range of less than 100 to 105 colony forming units per ml (CFU/ml). Detection times ranged from 20-35 hours for reclaimed water samples, and bacteria in untreated waste-waters were detected in 2-15 hours.

To compare the disinfection susceptibility of mucoid and non-mucoid P. aeruginosa in relation to EPS production, cultures were grown to stationary phase in defined media with a high or low C/N ratio using glucose as carbon source. Cultures diluted with phosphate buffered water pH 7.2 were pretreated by vortexing, centrifuging, or blending with 10 mM EDTA in PBW before disinfection with iodine, chlorine or monochloramine. It is suggested that differences observed between disinfectants may be due to their reactivities with cell constituents or modes of action. EPS may play a significant role in bacterial resistance to iodine and other halogens, although susceptibility varies markedly in relation to nutrient status and sample treatment before disinfection.

A number of microbiological issues are of critical importance to crew health and system performance in spacecraft water systems. This presentation will review an array of these concerns which include factors that influence water treatment and disinfection in spaceflight such as biofilm formation and the physiological responses of bacteria in clean water systems. Factors associated with spaceflight like aerosol formation under conditions of microgravity will also be discussed within the context of airborne infections such as Legionellosis. Finally, a spectrum of analytical approaches will be reviewed to provide an evaluation of methodological alternatives that have been suggested or used to detect microorganisms of interest in water systems. These range from classical approaches employing colony formation on specific microbiological growth media to direct (i.e. microscopic) and indirect (e.g. electrochemical) methods as well as the use of molecular approaches and gene probes.

Experiments were done to examine the sensitivity of various waterborne bacteria from iodinated systems to iodine, and their subsequent recovery and growth, because this halogen is used as a disinfectant in potable water systems on US manned space vehicles. A Pseudomonas aeruginosa isolated from a commercial iodine product was least sensitive when grown in reagent-grade water or phosphate buffered water (PBW) and most sensitive when cultivated on mineral salts medium supplemented with low levels of glucose and glutamate or Brain Heart Infusion (BHI) broth. However, a P. cepacia strain was most sensitive when grown on BHI broth. Isolates from an iodinated potable water system were less sensitive to iodine than Ps-4 while a clinical isolate exhibited intermediate sensitivity. Bacteria including Ps-4 generally recovered and grew in PBW at greater rates than uniodinated controls.

This study was done to quantify the sensitivity of bacteria to iodine under controlled laboratory conditions. When exposed to 1 mg/; I2 for 1 min, bacteria isolated from the Shuttle were more resistant than a P. aeruginosa isolated from a povidine-iodine solution. Cultures grown in rich media were more sensitive than those grown in low nutrient solutions. The P. aeruginosa and a P. cepacia isolated from the Shuttle were resuspended in PBW after exposure to iodine. Iodinated cells recovered better than uniodinated controls. Pseudomonads in biofilms developed on coupons of stainless steel were more resistant to iodine than cells suspended in buffered water. Although resistant bacteria may colonize spacecraft water systems, multiple treatment barriers should provide adequate control of these contaminants.