Factors influencing the persistence of enteropathogenic bacteria in wetland habitats and implications for water quality.

AIMS: To better understand the persistence dynamics of enteropathogenic bacteria in freshwater wetland habitats, we constructed lab-scale mesocosms planted with two different wetland plant species using a subsurface flow wetland design. Mesocosms were treated with either a high-quality or a poor-quality water source to examine the effects of water quality exposure and plant species on Escherichia coli, Salmonella spp. and Enterococcus spp. in the rhizoplane, rhizosphere and water of wetland habitats. METHODS AND RESULTS: Quantities of study micro-organisms were detected using real-time PCR in wetland mesocosms. A combination of molecular and culture-based methods was also used to enumerate these organisms from surface water and plant material at high, medium and poor water quality sites in the field. We found that all three enteropathogenic micro-organisms were influenced by microhabitat type and plant species. Organisms differed with respect to their predominant microhabitat and the extent of persistence associated with wetland plant species in the mesocosm study. Of the monitored pathogens, only E. coli was influenced by both water quality treatment and plant species. Salmonella spp. quantities in the rhizoplane consistently increased in all treatments over the course of the mesocosm experiment. CONCLUSIONS: Plant species selection appears to be an overlooked aspect of constructed wetland design with respect to the removal of enteropathogenic micro-organisms. Escherichia coli and Enterococcus concentrations in wetland outflow were significantly different between the two plant species tested, with Enterococcus concentrations being significantly higher in mesocosms planted with Phalaris arundinaceae and E. coli concentrations being higher in mesocosms planted with Veronica anagallis-aquatica. Furthermore, there is evidence that the rhizoplane is a significant reservoir for Salmonella spp. within wetland habitats. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first time that Salmonella spp. has been shown to proliferate under natural conditions within the rhizoplane. This will contribute to our understanding of wetland removal mechanisms for enteropathogenic bacteria. This study identifies the rhizoplane as a potentially important reservoir for human pathogenic micro-organisms and warrants additional study to establish whether this finding is applicable in non-wetland habitats.

Salmonella serotype diversity and seasonality in urban and rural streams.

AIMS: To investigate the prevalence, seasonality and genetic diversity of Salmonella enterica serotypes, particularly those of human and veterinary health significance, in urban and rural streams. METHODS AND RESULTS: Using a swab collection technique and multiple culture media for isolation, Salmonella were detected in 78.4% of water samples (November 2003 to July 2005) taken from urban and rural/agricultural streams in the Grand River watershed (Ontario, Canada). Among 235 isolates, there were 38 serotypes, with the predominant serotypes and phagetypes (PT) being Salmonella Typhimurium PT 104 and Salmonella Heidelberg PT 19. These are also the most common Salmonella serotypes found in humans and farm animals locally and across Canada, a trend not commonly reported. The urban stream had more frequent Salmonella occurrence, greater serotype diversity and greater genetic variability (based on pulsed field gel electrophoresis) of specific strains compared with the rural/agricultural streams. Distinct seasonality in serotypes of health significance was observed only in the rural/agricultural streams, which is likely a reflection of seasonal source inputs in these watersheds. Despite the lower occurrence of these strains in stream water in the colder months, laboratory studies did not support reduced survival of Salm. Typhimurium and Salm. Heidelberg at lower temperatures, although survival differences were observed with other serotypes. CONCLUSIONS: A diverse range of Salmonella serotypes and PT were obtained from both urban and rural/agricultural streams, with the predominant strains being those most frequently associated with human and veterinary disease in Canada. SIGNIFICANCE AND IMPACT OF THE STUDY: The ubiquitous nature of Salmonella in water and the predominance of serotypes/PT of human or veterinary health significance suggest that the aquatic environment is a reservoir for this bacterium and could be involved in the transport and dissemination of this pathogen between hosts.

A comparison of DNA repair and survival of Escherichia coli O157:H7 following exposure to both low- and medium-pressure UV irradiation.

DNA repair and survival of pathogenic E. coli O157:H7 was investigated following exposure to ultraviolet (UV) radiation from both low-pressure (LP) and medium-pressure (MP) lamps. This study included irradiation at UV doses used in drinking water treatment and lower doses indicative of potential treatment problems. Immediately following UV exposure, an average log inactivation of 4.5 or greater was observed following all tested doses of LP (5, 8, 20 and 40 mJ/cm(2)) or MP UV (5 and 8 mJ/cm(2)) indicating the sensitivity of E. coli O157:H7 to UV irradiation. Following conditions conducive to repair, maximum photo repair occurred rapidly within 30 minutes after low doses (5 and 8 mJ/cm(2)) of LP UV. The rate of repair was much higher than reported previously in non-pathogenic E. coli (which occurred within 2 hours). In contrast to LP UV, limited photo repair of E. coli O157:H7 was observed following MP UV exposure at reduced doses (5 and 8 mJ/cm(2)). At these lower doses, low levels of light independent repair were observed following LP UV, but not following exposure of MP UV irradiation. This study indicates that MP UV may enhance UV disinfection of E. coli O157:H7 by reducing the ability to repair following non-ideal treatment conditions. Following doses used in drinking water treatment (20 and 40 mJ/cm(2)), low levels of photo repair following LP UV were evident.

Escherichia coli control in a surface flow treatment wetland.

A field experiment showed that numbers of Escherichia coli declined significantly when floating Lemna spp. plants were removed to create open water areas in a typical newly constructed surface flow treatment wetland in southern Ontario. It is suggested that E. coli declined immediately after Lemna removal because the Lemna was shading the water column from penetration by natural UV radiation, it was providing favourable attachment sites for the E. coli, and it was not allowing effective free exchange of oxygen from surface winds to the water column to maintain high enough dissolved oxygen supplies for predator zooplankton populations. Operators of wetland systems must have the specialized skills required to recognize the cause and the appropriate maintenance requirements to maintain efficient operation of such unconventional systems should E. coli numbers increase during the course of operation.

Effects of temperature and biodegradable organic matter on control of biofilms by free chlorine in a model drinking water distribution system.

This study used annular reactors (AR) to investigate, under controlled laboratory conditions, the effects of temperature and biodegradable organic matter (BOM) on the free chlorine residual needed to control biofilm accumulation, as measured by heterotrophic plate count (HPC) bacteria. Biofilm was grown on PVC coupons, initially in the absence of chlorine, at 6, 12, and 18 degrees C, in the presence and absence of a BOM supplement (250 microg C/L) added as acetate. During the early stages of chlorine addition, when no measurable free chlorine residual was present, a reduction in biofilm HPC numbers was observed. Subsequently, once sufficient chlorine was added to establish a residual, the biofilm HPC numbers expressed as log CFU/cm2 fell exponentially with the increase in free chlorine residual. Temperature appeared to have an important effect on both the chlorine demand of the system and the free chlorine residual required to control the biofilm HPC numbers to the detection limit (3.2 Log CFU/cm2). For the water supplemented with BOM, a strong linear correlation was found between the temperature and the free chlorine residual required to control the biofilm. At 6 degrees C, the presence of a BOM supplement appeared to substantially increase the level of free chlorine residual required to control the biofilm. The results of these laboratory experiments provide qualitative indications of effects that could be expected in full-scale systems, rather than to make quantitative predictions.

Removal of geosmin and 2-methylisoborneol by biological filtration.

The quality of drinking water is sometimes diminished by the presence of certain compounds that can impart particular tastes or odours. One of the most common and problematic types of taste and odour is the earthy/musty odour produced by geosmin (trans-1, 10-dimethyl-trans-9-decalol) and MIB (2-methylisoborneol). Taste and odour treatment processes including powdered activated carbon, and oxidation using chlorine, chloramines, potassium permanganate, and sometimes even ozone are largely ineffective for reducing these compounds to below their odour threshold concentration levels. Ozonation followed by biological filtration, however, has the potential to provide effective treatment. Ozone provides partial removal of geosmin and MIB but also creates other compounds more amenable to biodegradation and potentially undesirable biological instability. Subsequent biofiltration can remove residual geosmin and MIB in addition to removing these other biodegradable compounds. Bench scale experiments were conducted using two parallel filter columns containing fresh and exhausted granular activated carbon (GAC) media and sand. Source water consisted of dechlorinated tap water to which geosmin and MIB were added, as well as, a cocktail of easily biodegradable organic matter (i.e. typical ozonation by-products) in order to simulate water that had been subjected to ozonation prior to filtration. Using fresh GAC, total removals of geosmin ranged from 76 to 100% and total MIB removals ranged from 47% to 100%. The exhausted GAC initially removed less geosmin and MIB but removals increased over time. Overall the results of these experiments are encouraging for the use of biofiltration following ozonation as a means of geosmin and MIB removal. These results provide important information with respect to the role biofilters play during their startup phase in the reduction of these particular compounds. In addition, the results demonstrate the potential biofilters have in responding to transient geosmin and MIB episodes.

Inactivation and potential repair of Cryptosporidium parvum following low- and medium-pressure ultraviolet irradiation.

This study investigated the level of inactivation and the potential for Cryptosporidium parvum to repair following low doses (1 and 3mJ/cm(2)) of ultraviolet (UV) irradiation from both low- and medium-pressure UV lamps. Cryptosporidium parvum oocysts suspended in phosphate buffered saline were exposed to UV using a bench-scale collimated beam apparatus. Oocyst suspensions were incubated at 5 degrees C or 25 degrees C under light and dark conditions up to 120 h (5 days) following exposure to UV irradiation, to examine photoreactivation and dark repair potential, respectively. Cryptosporidium parvum infectivity was determined throughout the incubation period using an HCT-8 cell culture and an antibody staining procedure for detection. No detectable evidence of repair was observed after incubation under light or dark conditions following either LP or MP UV lamp irradiation.

Potential repair of Escherichia coli DNA following exposure to UV radiation from both medium- and low-pressure UV sources used in drinking water treatment.

The increased use of UV radiation as a drinking water treatment technology has instigated studies of the repair potential of microorganisms following treatment. This study challenged the repair potential of an optimally grown nonpathogenic laboratory strain of Escherichia coli after UV radiation from low- and medium-pressure lamps. Samples were irradiated with doses of 5, 8, and 10 mJ/cm(2) from a low-pressure lamp and 3, 5, 8, and 10 mJ/cm(2) from a medium-pressure UV lamp housed in a bench-scale collimated beam apparatus. Following irradiation, samples were incubated at 37 degrees C under photoreactivating light or in the dark. Sample aliquots were analyzed for up to 4 h following incubation using a standard plate count. Results of this study showed that E. coli underwent photorepair following exposure to the low-pressure UV source, but no repair was detectable following exposure to the medium-pressure UV source at the initial doses examined. Minimal repair was eventually observed upon medium-pressure UV lamp exposure when doses were lowered to 3 mJ/cm(2). This study clearly indicates differences in repair potential under laboratory conditions between irradiation from low-pressure and medium-pressure UV sources of the type used in water treatment.

The effect of user-defined variables on dosimetry consistency in Gamma Knife planning.

We report a dosimetric variation caused by a user-defined variable for the Leksell Gamma Knife planning system. Treatment plans of 31 randomly selected patients were studied retrospectively to determine the dosimetric effects in the dose prescription and computation as a result of dose matrix positioning in the Leksell Gamma Plan (LGP, Version 4.12). Phantom studies with ion chamber measurements were carried out to validate the accuracy of the computation results. An average overdose of 2% was found due to the variations in the user-defined dose matrix position for the studied cases. In the extreme, the overdose value was as high as 5% with an over-treatment time exceeding 2 min. The phantom measurements were found to agree with the LGP calculation within 0.5%. An adaptive method was developed and demonstrated in this study to eliminate such dosimetry variations.

Utility of radiation in the prevention of heterotopic ossification following repair of traumatic acetabular fracture.

PURPOSE: Heterotopic ossification (HO) is a common problem following surgical repair of traumatic acetabular fracture (TAF), potentially causing severe pain and decreased range of motion. This report analyzes the role of radiation therapy for prevention of HO in TAF. METHODS AND MATERIALS: The charts of all patients who received RT to the hip following TAF repair between July 1988 and January 1998 were reviewed. Sixty-six patients were identified. RT was given in 5 fractions of 2 Gy in 45 patients, 1 fraction of 8 Gy in 17 patients, and other doses in 4 patients. Treatment fields encompassed periacetabular tissues at highest risk for HO. Time to RT was < or = 24 hours for 46 patients. RESULTS: Radiographic follow-up at least 6 months following RT was available in 47/66 (71%) patients to permit Brooker classification, revealing 6 cases (13%) of Grade III HO, compared to historical incidence in this population of 50%. No Grade IV HO was found. Mean follow-up was 18 months. Four of the Grade III patients had received 10 Gy/5 fractions, and 2 received 8 Gy/1 fraction. Postoperative wound infection occurred in 6 patients, and osteonecrosis of the femoral head was found in 13. CONCLUSIONS: RT following surgical repair of TAF provides effective prophylaxis against formation of clinically significant HO. We recommend a single fraction of 7-8 Gy within 24 hours of surgery to prevent HO formation and minimize patient discomfort.

Superior sulcus (Pancoast) tumor: experience with 105 patients.

BACKGROUND: The evolution of therapy in 105 patients with superior sulcus (Pancoast) tumor over the past 42 years was reviewed. METHODS: There were 82 men and 23 women aged 30 to 75 years. Tumor cell types were: squamous, 41 (39%); adenocarcinoma, 23 (21.9%); anaplastic, 14 (13.3%); undetermined, 12 (11.4%); mixed, 9 (8.7%); and large cell 6 (5.7%). Therapy was based on extent of disease and lymph node involvement. There were 5 treatment groups: I, preoperative radiation and operation (n = 28); II, operation and postoperative radiation (n = 16); III, radiation (n = 37); IV, preoperative chemotherapy, radiation, and operation (n = 11); and V, operation (n = 12). RESULTS: The median survival for group I was 21.6 months; group II, 6.9 months; group III, 6 months; and group V, 36.7 months. Median survival for group IV has not yet been reached (estimated at 72% at 5 years). On univariate analysis, mediastinal lymph node involvement, Horner syndrome, TNM classification, and method of therapy affected survival. On multivariate regression analysis, only N2 and N3 disease and method of therapy were significant (p < 0.05). CONCLUSIONS: The optimal treatment for superior sulcus tumor was preoperative radiation and operation. However, triple modality therapy, although promising, requires longer follow-up.

Fractionated half-body irradiation for pain palliation in widely metastatic cancers: comparison with single dose.

PURPOSE: To explore fractionated half-body irradiation (HBI) for pain palliation and determine if it is more efficient and effective than single dose HBI. METHODS AND MATERIALS: During the last 13 years, 75 out of 115 HBIs (64%) at the University of Maryland Medical Center were given for palliation of various widely metastatic cancers (28% prostate, 25% breast, 12% lung). The HBI fields were 28% upper, 25% mid, and 47% lower; three patients had both upper and lower HBI. An initial performance status (PS) 3&4 with a life expectancy < 3 months was found in 50% of patients. The HBI techniques used on consecutive patients were: single dose (SD) in 54% with escalating doses of 4-10 Gy; split-course (SC) in 12% with two 4 Gy single doses separated by 2 weeks; and daily fractionated (DF) in 34% with five fractions of 3 Gy each. There were 68 of 75 HBI (91%) given for pain control purposes. RESULTS: The percent total (complete) pain relief was SD-73(32), SC-50(13), and DF-96(49). Time to maximum and (complete) relief was: SD 5 days each and DF HBI 7(11) days. Pain-free survival (PFS) was short but so was overall survival (OS). PFS was SD-5, SC-4.5, and DF-19 weeks. The percent of the remaining patient's life spent pain free without retreatment (NPR) was SD-38, SC-34, and DF-68. Differences in pain relief, PFS, OS, and NPR were significant and carried over primary tumor types; prostate, breast, and surprisingly GI were very responsive (90, 84, and 83%, respectively). On multivariate analysis only the PS and degree of relief were independent variables. Despite lack of premedication in DF-HBI, toxic reactions were identical to SD-HBI with premedication. No Grade 4 toxicities occurred. Grade 3 toxicities were 4%. Retreatment was 3% in SD and 13% in fractionated HBI; these differences were not significant. CONCLUSION: HBI is still the most effective and efficient way to palliate pain from widely disseminated cancer. Fractionating HBI eliminates need for the premedication and close patient monitoring required for SD-HBI. It also allows for an increase in total dose which can produce better responses in pain relief, duration of relief, PFS, OS, and quality of life.

Mediastinal lung cancer: answers and questions.

A literature review was done to define the relative roles of radiation and surgery in the treatment of mediastinal stage III, non-small-cell lung cancer with no distant metastasis. No two reports are comparable. Little information is available on the clinical, preoperative stage as it relates to surgical findings and to survival. Rationale for adjuvant radiation is lacking from the reports. There is no survival advantage of surgery, even with postoperative radiation, over radiation alone for clinical stage III disease. Patients whose cancer seems early stage but is found to be pathologic stage III at time of surgery may benefit from the combination therapy, although this is controversial. Treatment failure is usually systemic, so there is a strong argument for adjuvant chemotherapy as well. Uniform multimodality reporting of results is necessary so that the appropriate roles of surgery, radiation, and chemotherapy can be identified for this group of patients.

Silver resistance in Pseudomonas stutzeri.

Silver resistance was studied in a silver-resistant Pseudomonas stutzeri AG259 strain and compared to a silver-sensitive P. stutzeri JM303 strain. Silver resistance was not due to silver complexation to intracellular polyphosphate or the presence of low molecular weight metal-binding protein(s). Both the silver-resistant and silver-sensitive P. stutzeri strains produced H2S, with the silver-resistant AG259 strain producing lower amounts of H2S than the silver-sensitive JM303 strain. However, intracellular acid-labile sulfide levels were generally higher in the silver-resistant P. stutzeri AG259 strain. Silver resistance may be due to formation of silver-sulfide complexes in the silver-resistant P. stutzeri AG259 strain.

Intensive combination chemotherapy, concurrent chest irradiation, and warfarin for the treatment of limited-disease small-cell lung cancer: a Cancer and Leukemia Group B pilot study.

PURPOSE: In prior Cancer and Leukemia Group B (CALGB) studies, combined chemotherapy and thoracic irradiation was superior to chemotherapy alone in limited-disease (LD) small-cell lung cancer (SCLC). A combined modality pilot study was performed to test the feasibility of adding warfarin to aggressive chemoradiotherapy for LD SCLC. PATIENTS AND METHODS: Combination chemotherapy with doxorubicin 45 mg/m2 intravenously (IV) on day 1, cyclophosphamide 800 mg/m2 IV on day 1, and etoposide (ACE) 80 mg/m2 on days 1 to 3 was given every 21 days for the first three courses. The fourth and fifth courses substituted cisplatin 33 mg/m2 IV on days 1 to 3 for the doxorubicin, with concurrent chest irradiation to a total of 4,000 cGy given in 20 fractions during a 4-week period followed by a boost of 1,000 cGy in five fractions during a 1-week period. Prophylactic cranial irradiation, 3,000 cGy was given concurrently in 10 fractions during a 2-week period. Courses 6 to 8 again used ACE chemotherapy, but courses 4 to 8 were given on a 28-day schedule with dose adjustment for hematologic or renal toxicity. Warfarin was given throughout the treatment period titrated to achieve a prothrombin time (PT) of 1.5 to 2 times the control. Patients with histologically proven limited-stage SCLC, good performance status, and normal renal, hematologic, and hepatic functions were eligible. RESULTS: Sixty-one of 66 patients entered onto the study were eligible and assessable. Fifty-four (89%) (95%) confidence interval [CI], 78% to 95%) experienced an objective response, 35 (57%) achieved a complete response (CR) (95% CI, 44% to 70%), and 17 (28%) achieved a partial response (95% CI, 16% to 39%). Median durations were CR, 26.3 months; failure-free survival, 11.8 months; and survival, 18 months. Forty-one percent of the patients were alive at 2 years, 33% were alive at 3 years, and 25% were alive at 4 or more years. Median follow-up for survivors is 5 years (range, 3.5 to 5.9 years). Severe or life-threatening myelosuppression occurred in 90%, infection occurred in 34%, fever without documented infection occurred in 26%, and pulmonary toxicity occurred in 6%. Another 6% of patients experienced severe or life-threatening hemorrhages. There were four treatment-related fatalities. The pulmonary toxicities have been associated with the resumption of ACE chemotherapy after chest irradiation. CONCLUSIONS: These highly encouraging response and survival results compare favorably with any prior CALGB group study. Although they are somewhat more toxic, they are comparable to the best published results. A randomized study that examines the role of warfarin is underway.

Germanium and silver resistance, accumulation, and toxicity in microorganisms.

Germanium is an inert metal with no known biological function in prokaryotic or eukaryotic organisms. Its toxicity is low compared to that of silver. Germanium is accumulated in certain bacterial strains by either energy-independent passive binding or an energy-dependent mechanism. Little is known about the molecular aspects of silver resistance, toxicity, and accumulation in bacterial strains. This is surprising because silver has been used as an antimicrobial agent in the medical field for centuries. It is likely that silver ions are excluded (resulting in decreased silver accumulation) from certain bacterial strains or immobilized intracellularly to prevent toxic effects from being exerted. These mechanisms of silver resistance have not been fully elucidated. This review examines the toxicity and accumulation of germanium and silver in selected microbial species. In addition, resistance mechanisms to these biologically nonessential metals is discussed, with more emphasis placed on silver-resistant bacteria due to the knowledge available.

Radiation therapy for chest recurrences following induction chemotherapy in small cell lung cancer.

Once small cell lung cancer fails induction chemotherapy, second line drugs are usually ineffective, accounting for mostly partial responses in the order of 0-20% and a median survival of 6-10 weeks. A review of patients with relapsed small cell lung cancer was carried out at the University of Maryland. Of 51 such patients, 44 received thoracic irradiation at the time of relapse. Excluding 8 patients who received insufficient treatment, the series consists of 36 patients (27 with limited and 9 with extensive disease) and represents the largest experience with relapsed small cell lung cancer subjected to radiation alone. Total radiation doses were 60 Gy in 11, 45-55 Gy in 14, and 38-42 Gy in the remaining 11 patients. No second line chemotherapy was given simultaneously with radiation at time of relapse and it was only given subsequently during the course of the disease to four patients. Responses to radiation were seen in 28 (77%) with 9 (25%) complete and 19 (52%) partial. The median survival was 16-40 weeks varying with disease extent, response, and total dose. Subsequent failures occurred in chest (34%) and distant sites (66%). A dose-response curve was attempted; the higher doses achieved as much as 75% local control. A poor response to induction chemotherapy did not predict a poor radiation response at time of relapse. Nearly 2/3 of patients who had not responded to induction chemotherapy responded to radiation at the time of relapse. The post-recurrence survival after radiation therapy was as long as or longer than the recurrence-free interval after induction chemotherapy, and this clearly demonstrates the value of radiation in achieving excellent palliation and good quality of life in these patients. Thoracic irradiation is recommended as a therapeutic alternative for locally recurrent small cell lung cancer after induction chemotherapy.

A protocol for the safe administration of debrisoquine in biochemical epidemiologic research protocols for hospitalized patients.

The genetically determined ability to metabolize the antihypertensive drug debrisoquine has been proposed as a genetic risk factor for primary carcinomas of the lung. To test this hypothesis, the metabolism of the drug was evaluated in a case control study. The subjects were characterized by their ability to metabolize debrisoquine after receiving a test dose of the drug followed by the collection of an 8-hour urine sample. They were classified by laboratory analysis into one of the following three groups: extensive, intermediate, and poor metabolizers. Poor metabolizers comprise 10% of the population and are unable to hydroxylate the drug. This group was expected to be at highest risk for deleterious effects from this medication. A protocol was created that included patient education and blood pressure monitoring to administer this medication safely to a group of patients with cancer who were already compromised. Although poor metabolizers showed a small decrease in systolic and diastolic blood pressure, no significant hypotensive episodes or clinical sequelae were observed in any of the groups. These data suggest that debrisoquine can be administered safely in a controlled clinical setting and will be useful for the characterization of lung cancer patients in biochemical epidemiology studies.

Bacterial interactions with silver.

This review examines interactions between bacteria and the biologically non-essential metal, silver. Aspects of silver toxicity, tolerance and accumulation (possible binding and uptake as opposed to energy-dependent transport) in bacteria are discussed. In addition, plasmid biology is examined briefly since little information is available on the exact mechanism(s) of plasmid-endoced silver resistance in bacteria.

The role of post-operative radiation in the prevention of heterotopic ossification in patients with post-traumatic acetabular fracture.

Heterotopic ossification (HO) with subsequent pain and limitation of motion of the lower extremity is a common and significant problem for patients who suffer traumatic acetabular fracture (TAF). The incidence of heterotopic ossification is markedly increased for patients requiring surgical repair depending on the degree of trauma and the type of surgical repair necessary. Radiation therapy (RT) has proven to be the most effective surgical adjunct for the prevention of heterotopic ossification in patients undergoing total hip replacement (THR), but has not been reported in patients with traumatic fracture and repair. This report details an experience with patients treated at a Shock Trauma Center with extensile repair and immediate (within 48 hr) post-operative radiation therapy given as 5 daily fractions of 2 Gy in 5 to 7 days to a total dose of 10 Gy using megavoltage radiation therapy. A total of 30 consecutive patients (RT group) have been treated at our institution since June 1985. The last 20 patients treated with surgery only (non-RT group) prior to initiation of this study were used as a control group. Heterotopic ossification was seen to some degree in 50% of all radiation therapy patients, but was severe in only three of 30 (10%) of cases [three (10%) had Brooker III HO and no patients had ankylosis (Brooker IV HO)]. In contrast, some degree of heterotopic ossification was seen in 90% of the non-radiation therapy patients, and was severe in 10 of 20 (50%) of patients [seven (35%) had Brooker III HO whereas three (15%) had ankylosis (Brooker IV)]. This difference is significant for both total incidence and incidence of severe cases (p less than 0.01). This reduction in heterotopic ossification incidence approaches the magnitude reported for high-risk patients with total hip replacement. Even though the incidence of severe heterotopic ossification after radiation therapy for total hip replacement is approximately 5% and for traumatic acetabular fracture patients it is double (10%), the actual incidence of heterotopic ossification without radiation therapy is different in the two conditions. For total hip replacement, the incidence is about 30% and for traumatic acetabular fracture it is 50%. Radiation therapy has again proven itself to be an excellent surgical adjunct to prevent heterotopic ossification, this time in traumatic acetabular fracture patients.