Dental amalgam fillings and the amount of organic mercury in human saliva.

We studied differences in the amounts of organic and inorganic mercury in saliva samples between amalgam and nonamalgam human study groups. The amount of organic and inorganic mercury in whole saliva was measured in 187 adult study subjects. The mercury contents were determined by cold-vapor atomic absorption spectrometry. The amount of organic and inorganic mercury in paraffin-stimulated saliva was significantly higher (p<0.001) in subjects with dental amalgam fillings (n = 88) compared to the nonamalgam study groups (n = 43 and n = 56): log(e) (organic mercury) was linearly related to log(e) (inorganic mercury, r(2) = 0.52). Spearman correlation coefficients of inorganic and organic mercury concentrations with the number of amalgam-filled tooth surfaces were 0.46 and 0.27, respectively. Our results are compatible with the hypothesis that amalgam fillings may be a continuous source of organic mercury, which is more toxic than inorganic mercury, and almost completely absorbed by the human intestine.

A between-species comparison of antimicrobial resistance in enterobacteria in fecal flora.

Enterobacteria in fecal flora are often reported to be highly resistant. Escherichia coli is the main species; resistance data on other species are rare. To assess the effect of the host's environment, antimicrobial resistance was determined in fecal species of the family Enterobacteriaceae from three populations: healthy people (HP)(n = 125) with no exposure to antimicrobials for 3 months preceding sampling, university hospital patients (UP) (n = 159) from wards where the antibiotic use was 112 defined daily doses (DDD)/bed/month, and geriatric long-term patients (LTP) (n = 74) who used 1.8 DDD/bed/month. The mean length of hospital stay was 5 days for the UP and 22 months for the LTP. The isolates were identified to at least genus level, and MICs of 16 antimicrobials were determined. From the university hospital, resistance data on clinical Enterobacteriaceae isolates were also collected. Resistance data for on average two different isolates per sample (range, 1 to 5) were analyzed: 471 E. coli isolates and 261 other Enterobacteriaceae spp. Resistance was mainly found among E. coli; even in HP, 18% of E. coli isolates were resistant to two or more antimicrobial groups, with MIC patterns indicative of transferable resistance. Other fecal enterobacteria were generally susceptible, with little typically transferable multiresistance. Clinical Klebsiella and Enterobacter isolates were significantly more resistant than fecal isolates. The resistance patterns at both hospitals mirrored the patterns of antibiotic use, but LTP E. coli isolates were significantly more resistant than those from UP. Conditions permitting an efficient spread may have been more important in sustaining high resistance levels in the LTP. E. coli was the main carrier of antimicrobial resistance in fecal flora; resistance in other species was rare in the absence of antimicrobial selection.

Resistance to mercury and antimicrobial agents in Streptococcus mutans isolates from human subjects in relation to exposure to dental amalgam fillings.

Resistance to cefuroxime, penicillin, tetracycline, and mercury is reported for 839 Streptococcus mutans isolates from 209 human study subjects. The MICs of these drugs did not differ for isolates from one dental amalgam group and two nonamalgam subsets: a group with no known exposure to amalgam and a group whose members had their amalgam fillings removed.

Screening for antimicrobial resistance in normal bacterial flora of the skin using the replica plating method.

The replica plating method was evaluated for detection of the antimicrobial resistance of normal bacterial flora of the skin and was compared with the results of a ten-colony method. If > or = 10% of the colonies from the master plate grew on a plate containing an antibiotic, the sensitivity of replica plating was comparable to that of a ten-colony method for samples containing resistant bacteria. However, this method classified significantly more samples as resistant to all eight antibiotics tested if the detection breakpoint was lowered to > or = 1% of the original colonies. Replica plating is an effective and practical tool for screening skin flora for resistance, also in samples with a low proportion of resistant strains.

Prescription of antimicrobial agents to elderly people in relation to the type of infection.

OBJECTIVE: to describe how frequently antimicrobial agents are prescribed for elderly people and to examine the prescribing practice of treating physicians. DESIGN: for each of the 1196 subjects examined, a review of the medical records was carried out for the year preceding the examination and data on antimicrobial prescriptions, including types of infections, were recorded. The sales statistics of antimicrobial agents in this population were compared with the nation-wide ones, collected by the National Agency for Medicines. SETTING: a health centre in Lieto, a rural district in southwestern Finland; 1990-91. SUBJECTS: 1196 subjects, aged 64-97 years, 488 men and 708 women. MAIN OUTCOME MEASURES: frequencies of prescriptions of specified antimicrobial agents, including types of infection in relation to gender and form of care over a 1-year period. RESULTS: more women (36%) than men (28%) had received antimicrobial agents. The proportion who had received such agents increased with increasing age, the trend being more marked in men. The mean number of prescriptions per user per year was slightly lower in men than women (0.6 and 0.7 respectively). In both sexes, 54% of the users of antimicrobial agents had received only one prescription. Cephalosporins and penicillins were the most commonly prescribed agents. Among those who had received three or more antimicrobial prescriptions, cephalosporins had been used most frequently. Elderly people living in long-term institutional care were treated with antimicrobial agents more frequently than those living outside institutions. Of all antimicrobial prescriptions given to women, 60% were prescribed for urinary tract infections, 21% for respiratory infections and 8% for skin infections. The figures for men were 18, 45 and 10%. CONCLUSIONS: multiple use of antimicrobial agents is common in old age, especially in those in institutions. More attention should be to the provision of appropriate antimicrobial treatment.

Problem of antimicrobial resistance of fecal aerobic gram-negative bacilli in the elderly.

In this study, we assessed the magnitude of risk (odds ratio [OR]) of patients being colonized with fecal aerobic gram-negative bacilli in two geriatric hospitals compared with the community, and we associated the use of antimicrobial agents with bacterial resistance. One fecal sample was collected from each of 341 patients, aged 60 years or older, during the hospital stay or when visiting the outpatient service. Samples were collected in 1988 and 1993 to 1994. The aerobic gram-negative bacilli from all samples were examined for resistance to seven antimicrobials by a replica plating method. The long-term-hospitalized patients had a significantly higher risk of being colonized with bacilli resistant to ampicillin (OR, 14.3; 95% confidence interval [95% CI], 6.0 to 34.1), cefuroxime (OR, 7.5; 95% CI, 2.7 to 20.8), trimethoprim (ORs, 22.3; 95% CI, 8.6 to 57.8), and tetracycline (OR, 5.2; 95% CI, 2.4 to 10.9) than the outpatients. The respective ORs among the short-term-hospitalized patients compared with the outpatients were 4.0 (95% CI, 1.9 to 8.4), 7.5 (95% CI, 2.7 to 20.8), 5.5 (95% CI, 2 to 14), and 2.0 (95% CI, 1 to 4). In 1993 to 1994 compared with 1988, in both hospitals there was a significantly increased risk of colonization by bacilli resistant to ampicillin (OR, 3.1; 95% CI, 1.9 to 5.1), cefuroxime (OR, 3.8; 95% CI, 2.1 to 6.7), and tetracycline (OR, 1.6; 95% CI, 1.0 to 2.5). However, the total use of antimicrobial agents increased only among the patients of the short-term-care hospital.

Antimicrobial resistance of fecal aerobic gram-negative bacilli in different age groups in a community.

We measured the occurrence of antimicrobial resistance in fecal aerobic gram-negative bacilli by age in community subjects. For none of the eight antimicrobial agents studied were there any statistically significant differences in the carriage rates of resistance in different age groups. Bacterial resistance was common in all age groups, including the children, and occurred for all antimicrobial agents tested.

Increase of antimicrobial resistance of faecal aerobic gram-negative bacteria in a geriatric hospital.

Antimicrobial resistance of faecal aerobic Gram-negative bacteria to eight different antimicrobials was determined by a velvet replica-plating method in 1988 and 1933. Faecal samples were taken from 131 geriatric inpatients in the Turku City Hospital with a hospitalization of more than 7 days. From 1987 to 1992 the use of first and second generation cephalosporins and ciprofloxacin increased from 3.32 defined daily doses (DDD) per bed to 24.25 DDD/bed and from 0.63 DDD/Bed to 28.11 DDD/bed, respectively. A statistically significant increase was observed in the frequency of samples resistant (with >= 1% of resistant colonies) to cefuroxime (p = 0.0004) and ceftazidime (p = 0.037) in patients who received antimicrobial therapy and to ampicillin (p = 0.046) in patients who had not received antimicrobial therapy. In addition, despite the decreased use of sulphonamides and trimethoprim (from 17.11 DDD/bed to 5.54 DDD/bed) no significant changes in the frequency of resistant faecal samples were observed. Use of ciprofloxacin has been found to cure resistance plasmids from bacteria in vitro. However, despite the increased use of ciprofloxacin, no decrease in faecal bacteria resistant to any of the other antimicrobials (i.e. trimethoprim) studied was observed.

Colonization of resistant faecal aerobic gram-negative bacilli among geriatric patients in hospital and the community.

Among the elderly most infections are caused by organisms of faecal origin. The study of the resistance of such Gram-negative bacilli should therefore be a priority. In this study, we determine the occurrence of resistance to five antimicrobials commonly used in geriatric outpatient care, and compare it with long-term and short-term hospitalized geriatric patients treated and not treated with antimicrobials.

Screening for antimicrobial resistance in fecal samples by the replica plating method.

Replica plating can be used for the detection of antibiotic resistance in normal flora. We have evaluated this application of the replica plating method by comparing it with a five-colony method. The replica plating method uses a single plate for each antibiotic, with a concentration just above that for borderline resistance. By the five-colony method, five colonies per sample were picked, chosen to represent all different colony morphologies present, and MICs were determined by a standard agar dilution method. The gram-negative, aerobic floras of 131 fecal samples were screened for resistance to ampicillin, cefuroxime, nalidixic acid, trimethoprim, sulfamethoxazole, and tetracycline by both methods. The rate of resistance detection by the two methods did not differ statistically for any of the antibiotics tested. The breakpoint concentrations used for the replica plates in the study gave results similar to those produced by the agar dilution method and the breakpoint values of the National Committee for Clinical Laboratory Standards and can thus be recommended. As the only currently used resistance detection method, replica plating facilitates an exact determination of the percentage of resistant colonies/total number of colonies (between 1 and 100%) in a sample. This revealed an uneven distribution, with only 23% of the samples having resistance frequencies in the range of 10 to 85%; usually, the resistant flora either was a small minority or was very dominant in samples with resistance. This phenomenon was present for all of the antibiotics.

Antimicrobial and mercury resistance in aerobic gram-negative bacilli in fecal flora among persons with and without dental amalgam fillings.

Antimicrobial resistance is more widespread than can be accounted for as being a consequence of the selection pressure caused by the use of antibiotics alone. In this study, we tested the hypothesis that a high mercury content in feces might select for mercury-resistant bacteria and thus for antimicrobial resistance linked to mercury resistance. Three subject groups with different exposures to dental amalgam fillings were compared. None of the subjects had taken antimicrobial agents during the three preceding months or longer. The group exposed to dental amalgam (n = 92) had 13 times more mercury in feces than the group that had never been exposed to amalgam (n = 43) and the group whose amalgam fillings had been removed (n = 56). No significant differences in either mercury resistance or antibiotic resistance in the fecal aerobic gram-negative flora of these subject groups were seen. The following antimicrobial resistance frequencies were detected with a replica plating method: > or = 1% resistance was seen in 40% of the subjects for ampicillin, 14% of the subjects for cefuroxime, 6% of the subjects for nalidixic acid, 14% of the subjects for trimethoprim, 19% of the subjects for sulfamethoxazole, and 25% of the subjects for tetracycline. The amount of mercury in feces derived from amalgam was not selective for any resistance factors in aerobic gram-negative bacteria, but antimicrobial resistance was widespread even among healthy subjects with no recent exposure to antibiotics.