Tiina Leistevuo

A between-Species Comparison of Antimicrobial Resistance in Enterobacteria in Fecal Flora

ABSTRACT 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 hosts 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 clinicalEnterobacteriaceae 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 otherEnterobacteriaceae spp. Resistance was mainly found amongE. 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 andEnterobacter 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.

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.

Resistance to Mercury and Antimicrobial Agents in Streptococcus mutans Isolates from Human Subjects in Relation to Exposure to Dental Amalgam Fillings

ABSTRACT 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.

Mercury in Saliva and the Risk of Exceeding Limits for Sewage in Relation to Exposure to Amalgam Fillings

Abstract The concentration of total mercury in stimulated saliva was studied in humans with dental amalgam fillings and in 2 nonamalgam groups. The probability of exceeding the limits of mercury permitted in wastewater increased proportionally as the number of amalgam-filled surfaces increased. The mercury limit for sewage is 0.05 mg/l (= 250 nmol/l) effluent, according to the Council of European Communities directive 84/156/EEC. In neither of the nonamalgam groups was this limit exceeded, but 20.5% in the amalgam group exceeded the limit (p < .001). The risk of exceeding the limit increased 2-fold for every 10 additional amalgam-filled surfaces (odds ratio = 2.0; 95% confidence interval = 1.3, 3.3). These results demonstrate that humans, especially in populated areas, can be a significant source of mercury pollutants. As a consequence of mercury release, bacteria may acquire mercury resistance, as well as resistance to other antimicrobial agents, thus resulting in failure of antibiotic treatment.

Prescription rates and diagnostic patterns are stable: a comparison of high-, medium- and low-prescribing primary care physicians treating community-acquired respiratory tract infections.

The objective was to study prescription practices of primary care physicians in prescribing antibiotics for community-acquired respiratory tract infections. Design was time series analysis and cross-sectional survey. The setting was 30 community primary health care centres. A case report form was completed for 3478 patient consultations treated by 198 office-based primary care physicians. Main outcome measures were: classification of diagnoses of respiratory tract infections made by each physician; number of antibiotic prescriptions related to these diagnoses; each physicians mean weekly number of antibiotic prescriptions during 6 months before and after the survey. Patients’ risk (odds ratio: OR) to receive an antibiotic prescription from the high and medium prescribers was 5.81 (95% confidence interval [CI] 4.85–6.96) and 2.41 (95% CI 2.04–2.86), compared to low prescribers. High and medium prescribers made more diagnoses of otitis media (OR 2.07, 95% CI 1.70–2.53 and 1.85, 95% CI 1.51–2.26, respectively) and fewer diagnoses of unspecified upper respiratory tract infection (OR 0.32, 95% CI 0.26–0.38 and 0.57, 95% CI 0.48–0.68, respectively) than low prescribers. The rank of the prescription rate of high, medium and low prescriber groups remained the same for all diagnoses except pneumonia. In addition, the annual rank between high, medium and low prescriber groups remained stable; high group prescribed more antibiotics during the year than medium group, which prescribed more than low prescriber group.