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PubMed1989

Chemical sterilization of bacterially contaminated bone without destruction of osteogenic potential.

A method to sterilize bone that has been contaminated or to assure sterility of allografts would be quite useful in the practice of orthopedics. The literature documents the osteogenic potential of demineralized bone matrix, prepared by treatment with hydrochloric acid and ethanol. We became interested in whether these potent antibacterial agents could render contaminated bone sterile and thus usable. Thus, we tested immersion in 70% ethanol or 0.6 N hydrochloric acid as sterilization methods for contaminated bone specimens. Bone fragments were (heavily) surface contaminated for 30-60 s by immersion in a suspension of either Escherichia coli, Staphylococcus aureus, or Bacillus subtilis and then placed in either the ethanol or hydrochloric acid solutions for 15 min, 30 min, 1 h, 2 h, 4 h, or 8 h. Subsequently, they were incubated in broth culture for 14 days. Using 70% ethanol, 80-90% of contaminated bone specimens were sterile in 4 h and all were sterile in 8 h. Using 0.6 N hydrochloric acid, only 10% of bone specimens contaminated with Staphylococcus aureus, 60% with Escherichia coli, and 90% with Bacillus subtilis were sterile in 8 h. Consequently, 70% ethanol could possibly by used as an antiseptic or sterilizing agent for contaminated bone, although we feel that such bone should also be demineralized. Ethanol should not be used for routine treatment of mineralized cortical bone as it has been shown to diminish the already poor osteogenic potential of cortical bone.

Administration, Topical↗

PubMed1978

Autotransfusion of contaminated intraperitoneal blood: an experimental study.

Contamination of blood by bowel contents has been generally assumed as an absolute contraindication to autotransfusion. Since abdominal trauma is frequently accompanied by bowel injury and massive blood loss, a potential major use for autotransfusion has thus been precluded. To test this presumption, autologous blood grossly contaminated with feces was incubated in the peritoneal cavity and then autotransfused in dogs. The animals were hemorrhaged 20, 30, or 40% of their estimated blood volume, producing mild to severe hypovolemic shock. Reinfusion of contaminated blood had little effect on survival with 20 or 30% hemorrhage, but contamination markedly decreased survival with 40% hemorrhage:90% survived without contamination while only 30% survived with contamination. The use of antibiotics in a similar group of dogs subjected to 40% hemorrhage essentially eliminated the risk of autotransfusion: 90% of these dogs survived autotransfusion of contaminated blood.

Animals↗

PubMed1999

Microbiological and radioactive contamination from radioaerosol ventilation scanning: is there a problem?

Radioaerosol lung imaging may result in (a) microbiological contamination of nebulizer circuits (a potential hazard to patients if the circuit is re-used), and (b) radioaerosol contamination of the atmosphere (a hazard to staff, particularly if inhaled, ingested or both). Altogether, 138 circuits were assessed for bacteriological contamination, 93 of which had been used for ventilation perfusion studies and 45 for lung permeability studies in human immunodeficiency virus (HIV) positive patients. The circuits used for ventilation/perfusion (V/Q) studies were re-used over a period of 1-5 days. The mouthpiece and Y-piece were changed between patients. The circuits used for permeability studies were changed in toto for each patient. Organisms belonging to normal respiratory flora were isolated from the Y-piece, mouthpiece or both in 9 of 138 cases. An additional case (from one of the HIV-positive patients) demonstrated a growth of methicillin-resistant Staphylococcus. We also demonstrated bacteriological growth, most likely of patient origin, in circuit tubing in 11 cases at the end of the first day's use and 9 cases by day 5. None of the circuits used for HIV-positive cases were culture-positive. Airborne radioactive contamination was assessed during radioaerosol inhalation with and without an air extractor device (Nederman) during 40 ventilation studies. The 20 studies with air extraction showed a large decrease in room air contamination. Nebulizer circuits can, and occasionally do, become contaminated with patients' organisms; this represents a potential infection control hazard and therefore re-use is contraindicated. The use of an air extractor will significantly reduce airborne radioaerosol contamination.

Aerosols↗

PubMed1998

Risk of blood contamination of health care workers in spine surgery. A study of 324 cases.

STUDY DESIGN: The relative risk of blood contamination during spine surgery was studied using data collected from 324 procedures. OBJECTIVES: To analyze demographic factors that predict blood-borne pathogens in the population of spine surgery patients, study the rates and patterns of blood contamination in health care workers (i.e., skin-penetrating incidents and nonpenetrating surface skin contamination from patients' blood) and compare those risks with those in other surgical departments, and analyze the effectiveness of barrier systems worn by the surgical team. SUMMARY OF BACKGROUND DATA: The Centers for Disease Control and Prevention has reported 49 health care workers infected by the human immunodeficiency virus through occupational exposure. Several studies have noted the risk of blood contamination in various surgical departments, but the relative risk during spine surgery has not been determined. METHODS: This year-long survey included 9795 cases, or 60,789 health care worker--patient contacts, of which spine disorders comprised 324 cases (2234 health care workers and patients). Data collection forms were designed and inservice training conducted with operating room staffs. Information regarding type of case, staff position (surgeon, assistant, scrub nurse, circulator), protective clothing worn, length of operating room time, blood loss, incidence of blood spills, was recorded, among other data. RESULTS: Prevalence of human immunodeficiency virus in patients in the overall series was 0.19% versus 0.93% in spine patients. The rate of HCW contamination in the overall series was 7.76%, of which 0.92% resulted from skin-penetrating incidents. Contamination in spine surgery occurred in 31.86% of cases, of which 1.23% were the result of skin-penetrating incidents. CONCLUSIONS: Health care workers in spine surgery have a statistically significant overall higher risk of blood contamination than do those in other surgical departments. The increased risk occurred with blood contacting intact skin. There was no higher risk for skin penetrating injury. Analysis of data suggests that health care workers always should wear double gloves, forearm-reinforced gowns, and eye protection.

Blood-Borne Pathogens↗

PubMed2005

Bacterial contamination of human organ-cultured corneas.

PURPOSE: This study was designed to define the risk of contamination of human corneas preserved by the organ-culture method. METHODS: We examined the microbial contaminations in 3,100 corneoscleral rims cultivated in our eye bank. Microbiologic tests were performed in the preservation medium 5 days after the beginning of cornea cultures and in the last day of culture (21.5 +/- 8.1 days), when the corneas were transferred to the deswelling medium. In 1,029 corneas a microbiologic test also was performed 1 day after the beginning of deswelling procedure. RESULTS: We found 206 microbial contaminations (6.65% of total) after 5 days and 17 (0.55%) at the end of the preservation period. The total number of contaminated samples during the cornea culture was 223 corresponding to 7.2% of the samples (95% confidence interval, 6.3-8.1). The 1,029 tests performed during the deswelling step disclosed 26 contaminated cornea cultures despite apparent sterility of the medium (2.5%; 95% confidence interval, 1.5-3.5). CONCLUSIONS: The observation of microbial contaminations in a time close to the transplant (i.e., at the end of the preservation period and in the deswelling step) showed that a fast microbial tests during the deswelling procedure may prevent the grafting of a contaminated cornea. The appearance of bacteria in the deswelling medium despite a negative culture medium suggests that bacteria penetrate the corneal tissues during the culture to be subsequently extruded when the internal fluids move outward.

Bacteria↗

PubMed1985

Contamination and bacterial retention capacity of beef carcasses at the abattoir.

The contamination of beef carcasses was studied together with the capacity of meat surfaces to retain bacteria along the processing line in the slaughter hall. The results showed that the contamination varied along the processing line, but that this pattern was essentially dependent on the contamination at the dressing station. It decreased or remained unchanged during the first 12 min and then increased, even without additional contamination. The contamination varied according to carcasses and micro-organisms studied and was not greatly affected by spray cleaning. The number of bacteria retained changed at a rate similar to that of the contaminants. The attachment was instantaneous. The results are discussed and compared with the various hypotheses about contamination and bacterial attachment processes.

Animals↗

PubMed1996

Microbiological contamination of ovine carcasses associated with the presence of wool and faecal material.

The microbiological contamination of ovine hind legs at sites which were visibly clean (control carcasses), sites immediately adjacent to and below visually contaminated sites, and sites contaminated with visible faecal material or wool were determined by excision sampling immediately after pelting and immediately after a pre-evisceration wash. The mean aerobic plate count (APC) and Escherichia coli count (EC) at clean sites immediately after pelting ranged from log10 cm-2 3.98 to 4.44 and log10 cm-2 0.96 to 1.51, respectively. These levels of contamination were significantly lower than those on sites contaminated with faecal material (log10 cm-2 6.00 and 3.00, respectively) or wool (log10 cm-2 5.44 and 2.45, respectively). The presence of faecal material or wool on the carcass was not associated with increased bacterial numbers on visually clean areas of the carcass. This indicates that the presence of faecal material or wool alone cannot be used as an indicator of the hygienic status of the carcass as a whole, particularly in the role of on-line monitoring parameters for HACCP systems. Pre-evisceration washing of carcasses had very little effect on the uncontaminated areas of the carcasses, but reduced the mean APC and EC at the site of visible contaminants. There was little evidence of redistribution of bacteria to immediately adjacent but visually clean sites. However, the residual levels of both APCs and ECs directly at sites of faecal contamination after washing were still significantly higher than at visually clean sites. Application of HACCP principles to ovine slaughter and dressing suggests that visible faecal material should be removed by trimming, whereas pre-evisceration washes can have a practical and microbiologically validated role in the removal of wool. There was generally a good correlation between APCs and ECs at the uncontaminated sites prior to pre-evisceration washing, suggesting that in some situations APCs can act as a useful indicator of both general carcass hygiene and the presence of faecal indicators.

Abattoirs↗

PubMed2006

Prevention of Salmonella cross-contamination in an oilmeal manufacturing plant.

AIMS: The mechanisms of Salmonella contamination in an oilmeal plant were investigated and the basic data were collected in order to achieve control of Salmonella in oilmeal. METHODS AND RESULTS: Salmonella was detected in all contamination vectors and environmental factors investigated, namely: operators, processing floor, dust in the air and rodents. In particular, high concentrations of Salmonella were detected on the processing floor of the manufacturing area, which has high oil content. Steam was the most effective disinfection method used for the processing floor, as the effects of heat sterilization and disinfection may work in tandem. In addition, restricting the movement of operators of the production chain remarkably reduced Salmonella contamination, even in areas of otherwise high contamination. CONCLUSIONS: Within the oilmeal plant, high Salmonella contamination rates for the processing floor represent the greatest risk of contamination of oilmeal via operators, dust in the air and rodents. Therefore, control of the processing floor is the most important means for reducing the oilmeal contamination rate. SIGNIFICANCE AND IMPACT OF THE STUDY: Specific Salmonella control methods for oilmeal plants have been established.

Animal Feed↗

PubMed2005

Clinical outcome of cadaveric renal allografts contaminated before transplantation.

This analysis was performed to define the incidence of pretransplant microbial contamination of donor kidneys, and to assess the resultant morbidity including infections requiring therapy, and graft loss. Case records of all 638 renal allograft recipients patients transplanted in our centre during the period June 1990 to October 2000 were studied. All the recipients were given a single dose of intravenous antibiotics at the time of induction of anaesthesia. A total of 775 microbiology reports on perfusion fluid, kidney swabs and ureteric tissue were retrieved. Fifty-eight of 638 (9.1%) patients were transplanted with a graft that showed preoperative contamination. 18 of these 58 patients (31%) subsequently required antibiotic treatment. Thirty of 32 patients who received kidney contaminated with skin flora had a benign course (i.e. no unexplained, no positive blood cultures or graft infection). By contrast, seven of nine recipients with grafts whose perfusion fluid yielded lactose fermenting coliforms (LFCs) required antibiotics and three of nine of them suffered graft loss as a result. Two of these patients had bacteraemia caused by LFC, and one died. Three of five patients with positive cultures due to yeast required treatment with antifungals. None of the four patients who had graft contaminated by Staphylococcus aureus became infected. One-year 49/58 (85%) of these patients survived with functioning graft. Overall 1-year patient survival was 53/55 (92%). These data suggest that contamination of renal allografts by LFCs or yeasts need to be treated preemptively before the onset of clinical manifestations. By contrast, contamination with skin contaminants does not pose a risk to the graft.

Anti-Bacterial Agents↗

PubMed2005

Risk perception of heavy metal soil contamination by high-exposed and low-exposed inhabitants: the role of knowledge and emotional concerns.

Soil contaminated with heavy metals is a salient example of environmental risk. Consumption of vegetables cultivated in contaminated soil or direct ingestion of soil by small children can damage health. In contrast to other kinds of pollution or risks such as air pollution or exposure to ozone, the individual risk concerning soil contamination is highly dependent on the way one is exposed to the local source of risk. Thus, we wanted to know if risk perception varies according to the level of exposure. A quasi-experimental, questionnaire-based study was conducted in a community in northwest Switzerland, where the soil is widely contaminated. The level of contamination varies with the distance from the source of the contamination, a metal processing plant. We investigated the perception of risk of heavy-metal-contaminated soil by inhabitants with high-exposure levels (N= 27) and those with low-exposure levels (N= 30). Both groups judged the risk for oneself similarly whereas the low-exposure group, when compared to the high-exposure group, judged perceived risk for other affected people living in their community to be higher. Besides this exposure effect, risk perception was mainly determined by emotional concerns. Participants with higher scores in self-estimated knowledge tended to provide low-risk judgments, were less interested in further information, showed low emotional concern, and thus displayed high risk acceptance. In contrast, actual knowledge showed no correlation with any of theses variables. Judgments on the need for decontamination are determined by risk perception, less application of dissonance-reducing heuristics and commitment to sustainability. The desire for additional information is not affected by missing knowledge but is affected by emotional concerns.

Emotions↗

PubMed2006

PCR-DGGE method to assess the diversity of BTEX mono-oxygenase genes at contaminated sites.

tmoA and related genes encode the alpha-subunit of the hydroxylase component of the major group (subgroup 1 of subfamily 2) of bacterial multicomponent mono-oxygenase enzyme complexes involved in aerobic benzene, toluene, ethylbenzene and xylene (BTEX) degradation. A PCR-denaturing gradient gel electrophoresis (DGGE) method was developed to assess the diversity of tmoA-like gene sequences in environmental samples using a newly designed moderately degenerate primer set suitable for that purpose. In 35 BTEX-degrading bacterial strains isolated from a hydrocarbon polluted aquifer, tmoA-like genes were only detected in two o-xylene degraders and were identical to the touA gene of Pseudomonas stutzeri OX1. The diversity of tmoA-like genes was examined in DNA extracts from contaminated and non-contaminated subsurface samples at a site containing a BTEX-contaminated groundwater plume. Differences in DGGE patterns were observed between strongly contaminated, less contaminated and non-contaminated samples and between different depths, suggesting that the diversity of tmoA-like genes was determined by environmental conditions including the contamination level. Phylogenetic analysis of the protein sequences deduced from the amplified amplicons showed that the diversity of TmoA-analogues in the environment is larger than suggested from described TmoA-analogues from cultured isolates, which was translated in the DGGE patterns. Although different positions on the DGGE gel can correspond to closely related TmoA-proteins, relationships could be noticed between the position of tmoA-like amplicons in the DGGE profile and the phylogenetic position of the deduced protein sequence.

Bacteria↗

PubMed2000

Shear bond strengths of one-bottle adhesives to oil-contaminated enamel.

PURPOSE: To evaluate resin bond strength to enamel contaminated with handpiece oil. MATERIALS AND METHODS: Bovine teeth were randomly assigned to six groups of 20 teeth each for treatment with one of six different bonding systems (five one-bottle and one multibottle). For each system, 10 enamel specimens were contaminated with handpiece oil before acid-etching and 10 were contaminated after acid-etching. The enamel was etched for 15 seconds using 35% phosphoric acid. Following adhesive application, composite resin was bonded using a gelatin capsule technique. Shear bond strengths from the two contaminated groups were compared to bond strengths to uncontaminated enamel obtained from a previous study that was performed by the same group of investigators, using the same facility, materials, and methods. RESULTS: Two-way analysis of variance (ANOVA) showed that the factor "surface contamination" did not have a significant effect on bond strength (p > .542). The type of adhesive and the interaction of adhesive and surface contamination were significant (p < .0001 and p < .003, respectively). When oil was applied before etching, mean bond strengths ranged from 18.0 +/- 4.8 MPa for OptiBond SOLO (Kerr Corp., Orange, California) to 25.3 +/- 5.6 MPa for Tenure Quik with Fluoride (Den-Mat Corp., Santa Maria, California). With oil applied after etching, bond strengths ranged from 18.4 +/- 8.0 MPa for Tenure Quik with Fluoride to 27.4 +/- 5.4 MPa for Single Bond (3M Dental Products, St. Paul, Minnesota). For the same adhesive, comparing uncontaminated and "oil-before-etch" contaminated groups, the only statistically significant difference in bond strengths was for OptiBond SOLO: 21.8 +/- 4.0 MPa (uncontaminated) versus 18.0 +/- 4.8 MPa (oil before etch). Comparing uncontaminated and "oil-after-etch" groups, the only statistically significant difference was for Tenure: 24.5 +/- 5.7 MPa (uncontaminated) and 18.4 +/- 8.0 MPa (oil after etch).

Analysis of Variance↗

PubMed1994

Molecular diagnostics for polychlorinated biphenyl degradation in contaminated soils.

Molecular diagnostic methods using DNA hybridization with specific gene probes are being developed for the monitoring of microbial populations capable of polychlorinated biphenyl (PCB) degradation in contaminated soils. Evaluation of composite samples from contaminated electrical substation soil by gas chromatography (GC) indicated that the PCBs present in the soil (approximately 200 ppm) resulted from contamination with Aroclor 1248. The PCBs have been weathered or degraded so that the lower molecular weight PCB congeners are no longer present. Microbiological and molecular site characterizations are in progress to determine the abundance of PCB degradative organisms and catabolic genes present. Cloned DNA fragments for the bphC gene (2,3-dihydroxybiphenyl dioxygenase) from the biphenyl/chlorobiphenyl degradative pathways of different organisms were used as gene probes to identify indigenous microorganisms with bphC gene sequences. In colony hybridization experiments, positive signals with the pDA251 gene probe were detected in cultures from both contaminated and uncontaminated soils. The degradative abilities of indigenous microorganisms and an added PCB-degradative bacterial strain were also monitored with [14C]4-chlorobiphenyl mineralization assays and gas chromatography of PCB residues extracted from the soils. Enrichment of the contaminated soil with biphenyl and chlorobiphenyls did not stimulate the indigenous microorganisms to degrade the soil PCB. Nevertheless, enrichment of the contaminated soil with biphenyl and chlorobiphenyl and addition of the PCB-degrading strain Alcaligenes eutrophus GG4202 did result in additional degradation of the soil PCB. The results obtained from these experiments should assist in developing and monitoring a remediation plan for these PCB-contaminated soils.

Biodegradation, Environmental↗

PubMed1996

Electron contamination in clinical high energy photon beams.

The electron contamination in photon beams has been investigated by means of contaminating lepton depth doses and dose profiles in different geometries with two 20 MV beams. Different components of this contamination have been investigated separately by systematically adding contamination to a "clean" reference field. At 20 MV, the air generated electrons were found to be almost negligible compared to the electrons originating from the accelerator head when measurements were performed in standard fields at SSDs between 80 and 120 cm. The total electron part of the depth dose curve was then almost the same, i.e., independent of SSD, when the collimator opening was held fixed. However, when different accessories such as a shaping block and different attenuating plates were located in the beam path below the collimators, a large SSD dependence of the electron contamination was noticed. A comparison was also made between two machines, one equipped with a multileaf collimator, with similar beam qualities at 20 MV. These measurements indicate that the interior view of the treatment head seen by the detector (mainly the flattening filter, monitor chamber, or other electron generating material) influences the magnitude of the electron contamination. When the collimator opening is decreased the electron contamination will also decrease as parts of the electron source will be shielded by the collimator blocks.

Air↗

PubMed1990

Type of closure prevents microbial contamination of cosmetics during consumer use.

The dispensing closure used for containers plays an important role in protecting cosmetics from in-use microbial contamination. This hypothesis was tested by aseptically packing unpreserved shampoo and skin lotion into containers with three different closure types which provided various degrees of protection against consumer and environmental microbial insults. Shampoo was packed in containers with slit-cap (n = 25), flip-cap (n = 25), or screw-cap (n = 28) closures. Skin lotion was packed in containers with pump-top (n = 21), flip-cap (n = 18), or screw-cap (n = 21) closures. The products were then used by volunteers under actual in-use conditions for 3 (shampoo) or 2 (skin lotion) weeks. After use, the products were evaluated for microbial contamination by using standard methods for enumeration and identification. The standard screw-cap closure provided only minimal protection against microbial contamination of both the shampoo (29% contamination incidence) and the skin lotion (71%). The slit-cap closure on the shampoo container and the flip-cap closure on the skin lotion container provided slightly enhanced degrees of protection (21 and 39% contamination incidence, respectively). The greatest amount of protection (i.e., lowest contamination incidence) was provided by the flip-cap closure for the shampoo container (0%) and the pump-top closure for the skin lotion container (10%). As a result, closure type plays an important role in protecting poorly preserved products from in-use microbial contamination.

Bacteria↗

PubMed2001

Mycobacterium diversity and pyrene mineralization in petroleum-contaminated soils.

Degradative strains of fast-growing Mycobacterium spp. are commonly isolated from polycyclic aromatic hydrocarbon (PAH)-contaminated soils. Little is known, however, about the ecology and diversity of indigenous populations of these fast-growing mycobacteria in contaminated environments. In the present study 16S rRNA genes were PCR amplified using Mycobacterium-specific primers and separated by temperature gradient gel electrophoresis (TGGE), and prominent bands were sequenced to compare the indigenous Mycobacterium community structures in four pairs of soil samples taken from heavily contaminated and less contaminated areas at four different sites. Overall, TGGE profiles obtained from heavily contaminated soils were less diverse than those from less contaminated soils. This decrease in diversity may be due to toxicity, since significantly fewer Mycobacterium phylotypes were detected in soils determined to be toxic by the Microtox assay than in nontoxic soils. Sequencing and phylogenetic analysis of prominent TGGE bands indicated that novel strains dominated the soil Mycobacterium community. Mineralization studies using [(14)C]pyrene added to four petroleum-contaminated soils, with and without the addition of the known pyrene degrader Mycobacterium sp. strain RJGII-135, indicated that inoculation increased the level of degradation in three of the four soils. Mineralization results obtained from a sterilized soil inoculated with strain RJGII-135 suggested that competition with indigenous microorganisms may be a significant factor affecting biodegradation of PAHs. Pyrene-amended soils, with and without inoculation with strain RJGII-135, experienced both increases and decreases in the population sizes of the inoculated strain and indigenous Mycobacterium populations during incubation.

Biodegradation, Environmental↗

PubMed2001

Selection of specific endophytic bacterial genotypes by plants in response to soil contamination.

Plant-bacterial combinations can increase contaminant degradation in the rhizosphere, but the role played by indigenous root-associated bacteria during plant growth in contaminated soils is unclear. The purpose of this study was to determine if plants had the ability to selectively enhance the prevalence of endophytes containing pollutant catabolic genes in unrelated environments contaminated with different pollutants. At petroleum hydrocarbon contaminated sites, two genes encoding hydrocarbon degradation, alkane monooxygenase (alkB) and naphthalene dioxygenase (ndoB), were two and four times more prevalent in bacteria extracted from the root interior (endophytic) than from the bulk soil and sediment, respectively. In field sites contaminated with nitroaromatics, two genes encoding nitrotoluene degradation, 2-nitrotoluene reductase (ntdAa) and nitrotoluene monooxygenase (ntnM), were 7 to 14 times more prevalent in endophytic bacteria. The addition of petroleum to sediment doubled the prevalence of ndoB-positive endophytes in Scirpus pungens, indicating that the numbers of endophytes containing catabolic genotypes were dependent on the presence and concentration of contaminants. Similarly, the numbers of alkB- or ndoB-positive endophytes in Festuca arundinacea were correlated with the concentration of creosote in the soil but not with the numbers of alkB- or ndoB-positive bacteria in the bulk soil. Our results indicate that the enrichment of catabolic genotypes in the root interior is both plant and contaminant dependent.

Bacteria↗

PubMed2005

Dynamics of an oligotrophic bacterial aquifer community during contact with a groundwater plume contaminated with benzene, toluene, ethylbenzene, and xylenes: an in situ mesocosm study.

An in situ mesocosm system was designed to monitor the in situ dynamics of the microbial community in polluted aquifers. The mesocosm system consists of a permeable membrane pocket filled with aquifer material and placed within a polypropylene holder, which is inserted below groundwater level in a monitoring well. After a specific time period, the microcosm is recovered from the well and its bacterial community is analyzed. Using this system, we examined the effect of benzene, toluene, ethylbenzene, and xylene (BTEX) contamination on the response of an aquifer bacterial community by denaturing gradient gel electrophoresis analysis of PCR-amplified 16S rRNA genes and PCR detection of BTEX degradation genes. Mesocosms were filled with nonsterile or sterile aquifer material derived from an uncontaminated area and positioned in a well located in either the uncontaminated area or a nearby contaminated area. In the contaminated area, the bacterial community in the microcosms rapidly evolved into a stable community identical to that in the adjacent aquifer but different from that in the uncontaminated area. At the contaminated location, bacteria with tmoA- and xylM/xylE1-like BTEX catabolic genotypes colonized the aquifer, while at the uncontaminated location only tmoA-like genotypes were detected. The communities in the mesocosms and in the aquifer adjacent to the wells in the contaminated area consisted mainly of Proteobacteria. At the uncontaminated location, Actinobacteria and Proteobacteria were found. Our results indicate that communities with long-term stability in their structures follow the contamination plume and rapidly colonize downstream areas upon contamination.

Actinobacteria↗