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Biomedical subjects

S M Harmon

Publications and source records attributed to S M Harmon.

At least 19 recordsLinked to original sources
PubMed2005

Mercury body burdens in Gambusia holbrooki and Erimyzon sucetta in a wetland mesocosm amended with sulfate.

This study used an experimental model of a constructed wetland to evaluate the risk of mercury methylation when the soil is amended with sulfate. The model was planted with Schoenoplectus californicus and designed to reduce copper, mercury, and metal-related toxicity in a wastestream. The sediments of the model were varied during construction to provide a control and two levels of sulfate treatment, thus allowing characterization of sulfate's effect on mercury methylation and bioaccumulation in periphyton and two species of fish--eastern mosquitofish (Gambusia holbrooki) and lake chubsucker (Erimyzon sucetta). After one year in the experimental model, mean dry-weight normalized total mercury concentrations in mosquitofish from the non-sulfate treated controls (374+/-77 ng/g) and the reference location (233+/-17 ng/g) were significantly lower than those from the low and high sulfate treatments (520+/-73 and 613+/-80 ng/g, respectively). For lake chubsucker, mean total mercury concentration in fish from the high sulfate treatment (276+/-63 ng/g) was significantly elevated over that observed in the control (109+/-47 ng/g), the low sulfate treatment (122+/-42 ng/g), and the reference population (41+/-2 ng/g). Mercury in periphyton was mostly inorganic as methylmercury ranged from 6.6 ng/g (dry weight) in the control to 9.8 ng/g in the high sulfate treatment, while total mercury concentrations ranged from 1147 ng/g in the control to a high of 1297 ng/g in the low sulfate treatment. Fish methylmercury bioaccumulation factors from sediment ranged from 52 to 390 and from 495 to 3059 for water. These results suggest that sulfate treatments add a factor of risk due to elevated production of methylmercury in sediment and porewater which biomagnified into small fish, and may potentially increase through the food web.

Analysis of Variance↗
PubMed2004

Methylmercury formation in a wetland mesocosm amended with sulfate.

This study used an experimental model to evaluate methylmercury accumulation when the soil of a constructed wetland is amended with sulfate. The model was planted with Schoenoplectus californicus and designed to reduce wastestream metals and metal-related toxicity. The soil was varied during construction to provide a control and two sulfate treatments which were equally efficient at overall mercury and copper removal. After an initial stabilization period, methylmercury concentrations in porewater were up to three times higher in the sulfate-treated porewater (0.5-1.6 ng/L) than in the control (<0.02-0.5 ng/L). Mean percent methylmercury was 9.0% in the control with 18.5 and 16.6% in the low- and high-sulfate treatments, respectively. Methylmercury concentrations measured in mesocosm surface water did not reflect the differences between the control and the sulfate treatments that were noted in porewater. The mean bulk sediment methylmercury concentration in the top 6 cm of the low-sulfate treatment (2.33 ng/g) was significantly higher than other treatment means which ranged from 0.96 to 1.57 ng/g. Total mercury in sediment ranged from 20.8 to 33.4 ng/g, with no differences between treatments. Results suggest that the non-sulfate-amended control was equally effective in removing metals while keeping mercury methylation low.

Biodegradation, Environmental↗
PubMed2003

A comparison of the daphnids Ceriodaphnia dubia and Daphnia ambigua for their utilization in routine toxicity testing in the Southeastern United States.

U.S. regulatory agencies commonly require effluent toxicity testing with Ceriodaphnia dubia--a practice that has led to the criticism that this species and test protocol often does not reflect local taxa or site-specific conditions. Using an indigenous test species may produce a more realistic model of local effects and may minimize test endpoint variance due to regional differences in water quality. This study addressed the substitution of C. dubia with Daphnia ambigua for toxicity testing in the southeastern United States. This investigation determined that D. ambigua could be laboratory cultured with only minimal changes to established regulatory protocol and that the life-cycle characteristics of this species were conducive to traditional acute and chronic aquatic toxicity test methods used with other daphnids. Acute toxicity tests showed that D. ambigua was less sensitive to some toxicants (sodium chloride, copper sulfate, and sodium lauryl sulfate) but more sensitive to others (chlorpyrifos). Chronic tests with copper sulfate and sodium chloride resulted in lower EC50S for D. ambigua reproduction with both compounds. When exposed to low-alkalinity, low-pH stream waters typical of many southeastern United States watersheds, C. dubia demonstrated a significant reproductive depression in two of three streams tested, whereas D. ambigua experienced no chronic effect. These results suggest that D. ambigua may serve as a suitable surrogate for C. dubia as an toxicity indicator species in these types of receiving streams.

Animals↗
PubMed1991

Large vessel occlusion with vasculitis in systemic lupus erythematosus.

Patients with SLE may have acute large vessel occlusion due to vasculitis and/or circulating antiphospholipid antibodies, as illustrated by the case we have reported. Unfortunately, delayed medical attention led to gangrene of the foot and amputation. Early recognition and appropriate treatment may significantly decrease morbidity and mortality. Medical treatment may include corticosteroids, thrombolysis, anticoagulation, or immunosuppression.

Adult↗
PubMed1989

Clostridium perfringens food poisoning: use of serotyping in an outbreak setting.

An outbreak of Clostridium perfringens food poisoning occurred among attendees of a firehouse luncheon. The predominant symptoms of diarrhea (100%) and abdominal pain (81%) among case-patients, the mean incubation period (13.4 h), and the mean duration of illness (21.2 h) were all characteristic of C. perfringens enteritis. Roast beef, although not epidemiologically implicated, was the most likely vehicle of transmission. Fecal specimens from case-patients contained a median C. perfringens spore count of greater than 10(6) and yielded isolates that were heat sensitive and predominantly nonhemolytic, produced C. perfringens enterotoxin A, and, in the majority of specimens (four of five), were identical in serotype. Food samples were negative. This outbreak demonstrates that following enumeration of C. perfringens from a suitable number of fecal specimens from case-patients, serotyping of the isolates may be helpful in implicating C. perfringens as the cause of foodborne illness. This is especially true when implicated food items test negative or are no longer available for testing.

Adolescent↗
PubMed1986

Detection of Clostridium perfringens enterotoxin in stool specimens and culture supernatants by enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent assay was developed to detect and quantitate Clostridium perfringens enterotoxin A in culture supernatants and in stool specimens from cases of diarrhea in which high numbers of enterotoxin-producing Clostridium perfringens were isolated. To analyze for enterotoxin A, polyvinyl chloride microtiter plates were coated with dilute immune whole rabbit serum. Enterotoxin A standards and samples were allowed to react with sensitized wells. The presence of the immobilized antigen in the wells was detected by the binding of immune rabbit immunoglobulin conjugated with peroxidase. Nanograms of enterotoxin were detectable. Four enterotoxin-positive and seven enterotoxin-negative cultures grown in Duncan-Strong medium gave expected results. Eighteen of 23 diarrheal stool specimens obtained after a food-poisoning outbreak at a state hospital were found to contain microgram quantities of enterotoxin per gram of stool, whereas five control diarrheal specimens contained less than 0.6 ng enterotoxin per gram of stool. These results indicate that the enzyme-linked immunosorbent assay technique is useful for differentiating enterotoxigenic strains and for diagnosing diarrhea caused by enterotoxigenic Clostridium perfringens.

Antibodies, Bacterial↗
PubMed1985

Two successive outbreaks of Clostridium perfringens at a state correctional institution.

An outbreak of acute gastrointestinal illness of short duration involving 100 inmates at a correctional institution followed a similar outbreak among the same population by eight days. Clostridium perfringens was the specific etiology in both outbreaks; the vehicle was roast beef in the first outbreak, ham in the second. Direct observation of food handling practices revealed that the meats were not cooled quickly enough following cooking; not reheated adequately prior to serving, and; held at improper temperatures prior to serving.

Animals↗
PubMed1982

New method for differentiating members of the Bacillus cereus group: collaborative study.

A collaborative study was conducted of a new method for differentiating members of the Bacillus cereus group. Using the new method, each of 14 collaborators identified 8 Bacillus cultures, which represented 3 biotypes of the B. cereus group. Each culture was tested for motility, hemolytic activity on trypticase-soy-sheep blood agar, and rhizoid growth on nutrient agar; carbol-fuchsin stain was used to determine the presence of protein toxin crystals. Cultures were identified as B. cereus (biotype 1), B. cereus var. mycoides (biotype 2), or B. thuringiensis (biotype 3). All collaborators correctly identified the unknown cultures and classified them correctly as to biotype. There were no statistically significant differences in the identification rates among the different laboratories. Additional tests by one participant on 5 strains of Bacillus anthracis showed that the new method is also adequate for differentiating B. anthracis from typically reacting strains of B. cereus. The method has been adopted interim official first action.

Bacillus cereus↗
PubMed1980

Enumeration and confirmation of Bacillus cereus in foods: collaborative study.

A collaborative study was conducted in 15 laboratories to evaluate 2 different techniques for enumerating Bacillus cereus in foods. A direct plating technique using mannitol-egg yolk-poly-myxin agar and a most probable number (MPN) technique using trypticase-soy-polymyxin broth were compared for the enumeration of high and low populations of B. cereus in mashed potatoes. The collaborative results showed that the overall mean recovery obtained with the low population level was essentially the same by both techniques. However, the overall mean recovery was significantly higher by the direct plating technique at the high population level. A statistical evaluation of the data also showed that the direct plating technique had better repeatability and reproducibility than did the MPN technique at both the high and low population levels. These results suggest that the MPN technique is suitable for examining foods containing low populations of B. cereus, but that the direct plating technique is preferable for foods that contain a high population of this organism. The confirmatory technique used in the proposed method is reliable for presumptive identification of isolates as B. cereus. The method has been adopted as official first action.

Bacillus cereus↗
PubMed1979

ICMSF methods studies. XII. Comparative study for the enumeration of Clostridium perfringens in feces.

As the second phase of an international comparative study for the enumeration of Clostridium perfringens, four methods were compared for "total" and spore counts of C. perfringens in fecal specimens: the SFP (Shahidi-Ferguson perfringens) agar (A), TSC (tryptose-sulfite-cycloserine) agar (B), SC (sulfite-cycloserine) agar (C), and neomycin blood agar (D) methods. In both the total and spore count procedures, the confirmed C. perfringens counts in method D were lower than in methods A, B, and C. Little differences among methods were found in the percentages of presumptive colonies confirmed as C. perfringens. The nonspecific counts in methods A and D were generally greater than in B and C, but nonspecific microorganisms did not interfere in the enumeration of C. perfringens spores by any of the four methods. In overall performance, methods B and C were superior to A and D. The mean C. perfringens spore count was only 0.17 log lower than the mean total count. Spore counts alone are, therefore, adequate in investigations of C. perfringens outbreaks.

Bacteriological Techniques↗
PubMed1979

Comparison of Stomacher and Waring Blendor for homogenizing foods to be examined for Clostridium perfringens.

The Colworth Stomacher Model 400 homogenizer was compared with the Waring Blendor for preparing food homogenates to be examined for Clostridium perfringens. Forty-eight samples representing 6 different food types were inoculated with C. perfringens and examined by the AOAC official first action method for enumeration of C. perfringens in foods. Identical paired specimens of each food type were blended with the 2 devices, and plate counts were made as specified in the official first action method. The effects of frozen storage on plate counts were determined by examining 24 food samples that had been stored for 3 days at -68 degrees C and homogenized both devices. Results of a statistical analysis of the experimental data indicated no significant difference overall (P greater than 0.05) in the plate counts of homogenates prepared with the Waring Blendor or the Stomacher 400, either before or after frozen storage of the food samples. However, the overall plate count average of the 48 samples was slightly higher with the Waring Blendor than with the Stomacher 400 homogenizer.

Bacteriological Techniques↗
PubMed1978

Method for maintaining viability of Clostridium perfringens in foods during shipment and storage: collaborative study.

A collaborative study was conducted in 12 laboratories to determine the effectiveness of a new method for maintaining vegetative cells of Clostridium perfringens in viable condition during storage and transport of food specimens to the laboratory. The collaborative results showed that treatment of brown gravy and roast beef samples with an equal amount by weight of sterile buffered glycerol-sodium chloride solution to give a final 10% glycerol concentration and storage with Dry Ice for 10 days at -56 degrees C resulted in plate counts of C. perfringens which were 2-4 log cycles higher with 2 different strains than counts with untreated specimens stored by the usual method at -20 degrees C. Plate counts obtained with the treated specimens stored with Dry Ice were less than 1 log cycle lower than counts made with identical specimens before freezing for storage and shipment to the collaborators. The results with treated specimens were also more uniform among the different laboratories. Because the new method for storage and shipment of food samples was so effective for maintaining viability of the organism, the official first action method for C. perfringens (46.B01) was changed to incorporate these procedures as part of the method.

Bacteriological Techniques↗
PubMed1977

Recovery of clostridia on catalase-treated plating media.

Four plating media commonly used for culturing clostridia were tested for their ability to support growth of several Clostridium species after storage of the plates for 1 to 10 days at 4 and 25 degrees C with and without subsequent addition of catalase. Liver-veal (LV) agar and brain heart infusion (BHI) agar rapidly became incapable of supporting growth after storage without added catalase, whereas Shahidi Ferguson perfringens agar base and Brewer anaerobic agar were less affected. Plate counts of vegetative cells of nine of the less fastidious Clostridium species on untreated LV and BHI agars, stored for 3 days at 4 degrees C, were 60 to 90% lower than counts on catalase-treated media. Counts on Shahidi Ferguson perfringens agar base were only 1 to 24% lower on untreated medium with the same species. Addition of 500 U of purified beef liver catalase to the surface of the 3-day-old agars before inoculation resulted in substantial restoration of the ability of the media to support colony formation from vegetative cells except with the most strictly anaerobic species (nonproteolytic C. botulinum types B, E, and F, and C. novyii types A and B). A similar response was obtained with spores of the less fastidious species on catalase-treated media. Our results suggest that inhibition of most Clostridium species on LV and BHI agars may be due to accumulation of peroxide during preparation, storage, and incubation of the media, and also suggest that the presence of glucose in these media is a major factor contributing to their inability to support growth. It is believed that the addition of exogenous catalase prevents the accumulation of peroxide(s), thus allowing colony formation from vegetative cells of the clostridia under what would otherwise be unsuitable cultural conditions.

Catalase↗
PubMed1977

ICMSF methods studies. VIII. Comparative study for the enumeration of Clostridium perfringens in foods.

Four methods were compared in an international comparative study for the enumeration of Clostridium perfringens: the SFP (Shahidi-Ferguson perfringens) agar (A), TSC (tryptose-sulfite-cycloserin) agar (B), SC (sulfite-cycloserine) agar (C), and neomycin blood agar (D) methods. The confirmed C. perfringens counts were slightly lower for D than for A-C. The percentages of presumptive colonies confirmed as C. perfringens were essentially the same in each method. The relative numbers of nonspecific colonies were the lowest in C, followed by B, D, and A. The methods were also compared for simplicity and for aspects associated with the recognition and selection of presumptive colonies.

Agar↗
PubMed1976

An outbreak of Bacillus cereus food poisoning resulting from contaminated vegetable sprouts.

In an outbreak of gastrointestinal illness caused by consumption of home-grown raw vegetable sprouts contaminated by Bacillus cereus, victims developed symptoms after an incubation period of 6-15 hours. Four persons initially experienced nausea and vomiting, and this was followed in 3 cases by abdominal cramps and diarrhea. Bacteriologic investigation indicated that B. cereus on unsprouted seeds proliferated during germination in a commercially sold seed sprouting kit and reached levels in excess of 10(7) per gram. B. cereus isolated from the incriminated sprouts exhibited enterotoxigenic activity when tested by the ligated rabbit ileal loop technique, the dermal reaction in guinea pigs, and the rabbit skin capillary permeability test. The diversity of symptoms and incubation periods attributed to B. cereus requires analysis for this often overlooked organism whenever food-borne gastroenteritis is suspected.

Adolescent↗
PubMed1976

Beneficial effect of catalase treatment on growth of Clostridium perfringens.

Several common plating media were tested for their ability to support growth of Clostridium perfringens after storage of the plates for 1 to 10 days at 4 and 25 degrees C with and without subsequent addition of catalase. Liver-veal (LV) agar and brain heart infusion (BHI) agar quickly become incapable of supporting growth after storage without added catalase, whereas Shahidi Ferguson perfringens (SFP) agar and Brewer anaerobic (BA) agar were less affected. Plate counts of C. perfringens on untreated LV and BHI agars stored 3 days at 25 degrees C showed a reduction of 98.2%, whereas counts on SFP and BA agars were reduced by 13.6% and 46.2%, respectively. Addition of 1,500 U of beef liver catalase to the surface of the 3-day-old agars before incubation resulted in substantial restoration of their growth-promoting ability. Counts of colonies on LV, GHI, SFP, and BA agars with added catalase were usually 20 to 90% higher than untreated controls. Similar results were obtained using purified catalase, fungal catalase, and horseradish peroxidase. These results suggest that inhibition may be due to peroxide formed during storage and incubation and that additon of catalase provides near optimum conditions for growth of C. perfringens on these media.

Agar↗