Little evidence for reversibility of trimethoprim resistance after a drastic reduction in trimethoprim use.

OBJECTIVES: The worldwide rapid increase in antibiotic-resistant bacteria has made efforts to prolong the lifespan of existing antibiotics very important. Antibiotic resistance often confers a fitness cost in the bacterium. Resistance may thus be reversible if antibiotic use is discontinued or reduced. To examine this concept, we performed a 24 month voluntary restriction on the use of trimethoprim-containing drugs in Kronoberg County, Sweden. METHODS: The intervention was performed on a 14 year baseline of monthly data on trimethoprim resistance and consumption. A three-parameter mathematical model was used to analyse the intervention effect. The prerequisites for reversion of resistance (i.e. fitness cost, associated resistance and clonal composition) were studied on subsets of consecutively collected Escherichia coli from urinary tract infections. RESULTS: The use of trimethoprim-containing drugs decreased by 85% during the intervention. A marginal but statistically significant effect on the increase in trimethoprim resistance was registered. There was no change in the clonal composition of E. coli and there was no measurable fitness cost associated with trimethoprim resistance in clinical isolates. The frequency of associated antibiotic resistances in trimethoprim-resistant isolates was high. CONCLUSIONS: A lack of detectable fitness cost of trimethoprim resistance in vitro together with a strong co-selection of other antibiotics could explain the rather disappointing effect of the intervention. The result emphasizes the low possibility of reverting antibiotic resistance once established and the urgent need for the development of new antibacterial agents.

Modeling the stylized facts in finance through simple nonlinear adaptive systems.

Recent work on adaptive systems for modeling financial markets is discussed. Financial markets are viewed as evolutionary systems between different, competing trading strategies. Agents are boundedly rational in the sense that they tend to follow strategies that have performed well, according to realized profits or accumulated wealth, in the recent past. Simple technical trading rules may survive evolutionary competition in a heterogeneous world where prices and beliefs co-evolve over time. Evolutionary models can explain important stylized facts, such as fat tails, clustered volatility, and long memory, of real financial series.

Prescribing, prescription costs and adherence to formulary committee recommendations: long-term differences between physicians in public and private care.

BACKGROUND: In southern Sweden, many general practitioners (GPs) participate in an extensive postgraduate drug education programme, and many health centres are also fed back crude local drug statistics from pharmacists in the area. Private physicians and hospital physicians have not participated in these programmes. OBJECTIVE: The drug prescribing habits and costs of GPs, hospital physicians and private physicians were compared. METHODS: Each March, from 1990 to 1997, all prescriptions dispensed at the eight pharmacies in Växjö, a city and municipality in southern Sweden, were registered, specifying drug(s) prescribed, price, patient's age, sex and area of residence, and prescriber's place of work and category. RESULTS: Overall, the costs of prescribed drugs increased with time, even in 1997 when the prescribing volume was reduced due to changes in the reimbursement system. The cost increase was caused by increased prescribing of newer, more expensive drug alternatives. However, within each of the eleven major drug groups, the drugs prescribed by GPs were less expensive than those prescribed by hospital physicians and, particularly, private physicians. Moreover, even though GPs prescribed more and a wider range of drugs, they also had a higher degree of adherence to the recommendations by the formulary committee. CONCLUSION: GPs prescribed less expensive drugs and had a higher degree of adherence to the recommendations by the formulary committee than other categories of physicians. One reason for these differences may be that the GPs participated in regional and local educational activities aimed at the rationalisation of drug prescribing.

Prescriptions of antibiotics for children. Prescribing habits of district, hospital, and private physicians.

OBJECTIVE: To study how different categories of physicians prescribe antibiotics for children with respiratory tract infections. DESIGN: Prescriptions of antibiotics for children less than 15 years of age were registered at the pharmacies in the municipality of Växjö during the month of March from 1990 to 1993. SUBJECTS: Three categories of physicians were studied: district, hospital, and private. They made 3047 prescriptions for one of the following groups of antibiotics: penicillin V, ampicillin derivatives, erythromycin or other macrolides, and peroral cephalosporins. MAIN OUTCOME MEASURES: The choice and cost of drug for each physician category. The proportion of prescriptions made by district physicians in relation to distance from town centre and doctor density in local health centre. RESULTS: The district physicians used penicillin V more frequently (70% of prescriptions) than the other categories of physicians (50% and 19%), but ampicillin derivatives and cephalosporins less frequently. District physicians had a lower cost per prescription in general (SEK 92) than hospital physicians (SEK 110) and private physicians (SEK 175). The proportion of prescriptions issued by district physicians increased with increasing distance from the town centre and with higher doctor density in the local health centre. CONCLUSION: District physicians use more penicillin V, and have a lower cost per prescription, than other physicians. This might be due to differing infectious disease panoramas, but can also reflect differences in practice and attitudes.

What factors are of importance for infants' use of health and medical care during the first 18 months?

OBJECTIVE: To study factors of importance for infants' use of health and medical care. DESIGN: We studied the medical records of the mother during pregnancy (at the health centre, at the antenatal clinics, and at the department of obstetrics and gynaecology) and of her infant during the first 18 months of life (at the health centre, at the child health clinic, and at the departments of paediatrics and oto-rhino-laryngology). We also interviewed the mother when her infant was 18 months old. SETTING: Teleborg health centre, Växjö, southern Sweden. SUBJECTS: 206 infants and their mothers. MAIN OUTCOME MEASURES: Medical visits, to doctor or district nurse, during the infants' first 18 months of life, and factors of potential importance for those visits. RESULTS: A stepwise linear multiple regression analysis showed that the following factors were of importance for the infant's use of health and medical care: number of mother's visits to the health and medical services during pregnancy, mother being a primipara, and mother being a blue-collar worker. The model (12.98 + 0.52* (no. of mother's visits) + 2.19 (if primipara) + 1.48 (if blue-collar worker)) was able to explain 8.6% of the number of infant's visits. CONCLUSION: The studied factors explained only a minor part of the infants' use of health and medical care.

To prescribe--or not to prescribe--antibiotics. District physicians' habits vary greatly, and are difficult to change.

OBJECTIVE: To study how different doctors at a primary health care centre prescribe antibiotics for respiratory tract infections, and, if possible, to identify reasons for differences in prescribing habits. DESIGN: All medical visits to the health centre because of respiratory tract infections during January and February were studied in four consecutive years (1990-1993). The principles for prescribing antibiotics were discussed continuously to obtain more uniform routines. SETTING: The health centre of Teleborg serves a suburban district with about 10,000 inhabitants, and rural surroundings with another 2,000 inhabitants. SUBJECTS: All 2150 visits because of respiratory tract infections (except acute otitis media) made during the studied eight months. All physicians employed at the health centre (five physicians were employed for the whole study period). MAIN OUTCOME MEASURES: Percentage of visits resulting in prescription of antibiotics, and diagnoses given. RESULTS: Antibiotics were prescribed for 76% of the patients by the most generous doctor, but only for 21% by the most restrictive one. The use of diagnoses suggesting bacterial infection varied in a similar way. Otherwise, the patients of the various doctors looked very much the same, and the return visits for the same complaint during the study months were about 5% for all doctors. In spite of the on-going policy discussions, the doctors kept their positions as generous or restrictive prescribers throughout the study period. CONCLUSION: Doctors have an individual and very constant pattern of prescribing antibiotics, and it seems that the diagnoses are often given to justify the treatment, rather than the other way round.

Infectious diseases and day-care centre environment.

During the period from September 1986 to May 1987 all 25 day-care centre departments in the residential district of Teleborg in Växjö were studied to discover the frequency of absence due to infection. Mean absence/department was 6.6% (SD 2.2), with a range from 3.9% to 10.2%. During the period from September 1989 to May 1990 a follow-up study used the same methods to investigate 7 departments, which in the first study had shown the highest and lowest rates of absence due to infection. In addition, the carbon dioxide content in indoor air was measured in all departments in the district. The new measurements showed that the average absence due to infection in the 7 departments had fallen from 7.5% (SD 2.9) to 5.6% (SD 1.4). It was not possible to reproduce the division seen in the first study into departments with high and low absence rates. The variations in infectious morbidity observed could not be explained by differences between the departments as regards physical environment or working routines. By contrast, a considerable difference as regards carbon dioxide content in indoor air was seen between the 3 departments housed in converted dwellings and the 4 departments in purpose-built day-care centres; the mean values were 822 ppm and 458 ppm, respectively (Mann-Whitney U-test; p = 0.028).

Maternal cigarette smoking, breast-feeding, and respiratory tract infections in infancy. A matched-pairs study.

The importance of mothers' smoking habits for the occurrence of respiratory tract infections (RTIs) in their children during their infant years was studied. A group of 28 infants of mothers who smoked was compared with 28 infants of non-smokers. The pairs were matched with respect to mother's age, marital status, occupation, and parity. During their first year of life, the smokers' children were treated with antibiotics because of RTIs more often than the non-smokers' children (p = 0.046). The number of RTIs in the two groups were 38 and 19, respectively. However, infants of mothers who smoked were breast-fed for a shorter period than those of non-smokers (p = 0.028), the mean values being 4.5 and 6.7 months.