Attractant and disruptant semiochemicals for Dendroctonus jeffreyi (Coleoptera: Curculionidae: Scolytinae).

Jeffrey pine, Pinus jeffreyi Greville and Balfour, is a dominant yellow pine and important overstory component of forests growing on diverse sites from southwestern Oregon to Baja California to western Nevada. The Jeffrey pine beetle, Dendroctonus jeffreyi Hopkins (Coleoptera: Curculionidae: Scolytinae), is monophagous on Jeffrey pine and its primary insect pest. Despite the importance of P. jeffreyi, difficult terrain, environmental concerns, and lack of roads can constrain pest management activities. Semiochemicals are often easier to apply and more environmentally acceptable than other options, but they are lacking in this system. Attractants have been identified, but field bioassays have been limited because of infrequent or short duration outbreaks and a lack of beetles during nonoutbreak periods. Disruptant semiochemicals have not been assessed for D. jeffreyi during outbreak conditions; however, commercially available semiochemicals have been implicated as disruptants for this bark beetle. The objective of this study was to identify the most effective commercially available attractant and disruptant semiochemicals for D. jeffreyi. Our highest observed catch occurred with the blend of 5% 1-heptanol and 95% n-heptane. When this was used to challenge potential disruptant semiochemicals, the combination of S-(-)-verbenone and the green leaf volatile blend (cis-3-Hexenol and 1-Hexanol) reduced trap catch by ≍80%. However, frontalin was most effective, reducing the number of D. jeffreyi caught by >96%. Within each year of the study, the percentage female of D. jeffreyi caught with our attractant decreased from start to end of the experimental period. On average, our first collection in a year (mid-June to early July) was 59% female, whereas our last (mid-August) was 34%. Frontalin was equally or more effective against females (the pioneering sex) than males, providing optimism that semiochemical disruption may be possible for protecting Jeffrey pines from D. jeffreyi.

Prescriber adherence to pharmacokinetic monitoring service recommendations for aminoglycoside dosing and the risk of acute kidney injury.

OBJECTIVE: The importance of adherence to aminoglycoside dosing recommendations by a pharmacokinetic monitoring service for preventing acute kidney injury (AKI) is unknown. We aimed to examine the association between AKI and discordance in aminoglycoside dosing between physician orders and recommendations by a pharmacokinetic monitoring service. MATERIALS: We utilized 2000 - 2003 data from a large quaternary care academic medical center, including: hand-written pharmacokinetic monitoring service recommendations; computerized physician order entry inpatient medication orders; and electronic inpatient laboratory orders and results. METHODS: We conducted a case-control study, nested within users of intravenous aminoglycosides. Outcomes of interest were cases of AKI, as determined by changes in serum creatinine. Exposures of interest were discordances between pharmacokinetic monitoring service recommendations and physician orders in the past 2 days with regard to total daily aminoglycoside dose. RESULTS: Most patients received once-daily or less frequent aminoglycoside dosing. In 1,414 evaluable aminoglycoside courses, 220 patients developed AKI, for a cumulative incidence of 15.6%. We identified 690 controls, matched these to 220 cases, and found adjusted odds ratios of 0.72 (95% CI: 0.37 - 1.39) for overdose discordance and of 0.83 (0.51 - 1.34) for underdose discordance, suggesting that discordance in dosing is not associated with AKI. CONCLUSION: Non-adherence to dosing recommendations for aminoglycosides was not associated with risk of AKI in a setting primarily of once-daily aminoglycoside administration.

Pharmacogenetic modulation of combined hormone replacement therapy by progesterone-metabolism genotypes in postmenopausal breast cancer risk.

Combined hormone replacement therapy (CHRT) containing estrogens and progestins is associated with breast cancer risk. The authors evaluated interactions between CHRT use and progestin metabolism genotypes at CYP3A4 and the progesterone receptor (PGR) and their effects on breast cancer risk using the population-based Women's Insights and Shared Experiences (WISE) Study (1999-2002) of postmenopausal Caucasian women (522 breast cancer cases, 708 controls). The authors observed an elevated risk of ductal tumors in women with 3 or more years of CHRT use and PGR 331A alleles compared with those who had neither factor (odds ratio = 3.35, 95% confidence interval (CI): 1.13, 9.99; two-sided p(interaction) = 0.035). They also observed an elevated risk of progesterone receptor-positive tumors in women who had had 3 or more years of CHRT use and PGR 331A alleles compared with those who had neither factor (odds ratio = 3.82, 95% CI: 1.26, 11.55; p = 0.028). Finally, they observed an increased risk of estrogen receptor-negative tumors in women without CHRT exposure and CYP3A4*1B alleles compared with those who had neither factor (odds ratio = 6.46, 95% CI: 2.02, 20.66; p = 0.024), although the biologic interpretation of this result requires further study. When stratified by recency of use, PGR effects were observed only in current CHRT users, while CYP3A4 effects were observed only in former CHRT users. Breast cancer risk in women who have used CHRT may be influenced by genetic factors involved in progestin metabolism.

Defining optic nerve tortuosity.

BACKGROUND AND PURPOSE: Optic nerve tortuosity is one of several nonmalignant abnormalities documented on MR imaging in patients with neurofibromatosis type 1 and may be related to the development of optic pathway gliomas. This study seeks an operational definition for optic nerve tortuosity. MATERIALS AND METHODS: A focus group of 3 pediatric neuroradiologists reviewed 20 MR images of the brain and orbits of patients suspected to have optic nerve tortuosity in the absence of optic pathway glioma and found 6 radiographic factors that occurred frequently. Subsequently, 28 MR images were assessed for the presence of optic nerve tortuosity, using a global assessment question that reflects a neuroradiologist's confidence in the presence of optic nerve tortuosity, and for the presence of the 6 radiographic factors, to identify a combination of these factors that best predicted a diagnosis of optic nerve tortuosity. RESULTS: We found perfect inter-rater agreement between 3 readers on the presence/absence of tortuosity in 75% of cases. Lack of congruity of the optic nerves, in more than 1 coronal section and dilation of the subarachnoid space surrounding the optic nerves, when found together are sensitive (89%) and specific (93%) for a diagnosis of tortuosity on the global scale. The absence of these 2 factors, along with absence of deviation of the optic nerve within the axial plane, provides a reliable test to exclude tortuosity. CONCLUSION: Lack of congruity of the optic nerves in more than 1 coronal section and dilation of the subarachnoid space surrounding the optic nerves together provide an operational radiographic definition of optic nerve tortuosity.

Reproductive factors and subtypes of breast cancer defined by hormone receptor and histology.

Reproductive factors are associated with reduced risk of breast cancer, but less is known about whether there is differential protection against subtypes of breast cancer. Assuming reproductive factors act through hormonal mechanisms they should protect predominantly against cancers expressing oestrogen (ER) and progesterone (PR) receptors. We examined the effect of reproductive factors on subgroups of tumours defined by hormone receptor status as well as histology using data from the NIHCD Women's Contraceptive and Reproductive Experiences (CARE) Study, a multicenter case-control study of breast cancer. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) as measures of relative risk using multivariate unconditional logistic regression methods. Multiparity and early age at first birth were associated with reduced relative risk of ER + PR + tumours (P for trend=0.0001 and 0.01, respectively), but not of ER - PR - tumours (P for trend=0.27 and 0.85), whereas duration of breastfeeding was associated with lower relative risk of both receptor-positive (P for trend=0.0002) and receptor-negative tumours (P=0.0004). Our results were consistent across subgroups of women based on age and ethnicity. We found few significant differences by histologic subtype, although the strongest protective effect of multiparity was seen for mixed ductolobular tumours. Our results indicate that parity and age at first birth are associated with reduced risk of receptor-positive tumours only, while lactation is associated with reduced risk of both receptor-positive and -negative tumours. This suggests that parity and lactation act through different mechanisms. This study also suggests that reproductive factors have similar protective effects on breast tumours of lobular and ductal origin.

Risk of venous thromboembolism from oral contraceptives containing gestodene and desogestrel versus levonorgestrel: a meta-analysis and formal sensitivity analysis.

Controversy exists regarding whether oral contraceptives (OCs) containing desogestrel and gestodene are associated with an increased risk of venous thromboembolism (VTE) versus OCs containing levonorgestrel. We were interested in synthesizing the available data, exploring explanations for mixed results, and characterizing the degree of uncontrolled confounding that could have produced a spurious association. We performed a meta-analysis and formal sensitivity analysis of studies that examined the relative risk of VTE for desogestrel and gestodene versus levonorgestrel. Twelve studies, all observational, were included. The summary relative risk (95% CI) was 1.7 (1.3-2.1; heterogeneity p = 0.09). If real, the incremental risk of VTE would be about 11 per 100,000 women per year. An association was present when accounting for duration of use and when restricted to the first year of use in new users. However, in the sensitivity analysis, the association abated in many, but not all, scenarios in which an unmeasured confounding factor increased the risk of VTE three to fivefold and in nearly all examined scenarios in which the factor increased the risk 10-fold. The summary relative risk of 1.7 does not appear to be caused by depletion of susceptibles, but is sensitive to a modest degree of unmeasured confounding. Whether such confounding occurred is unknown. However, given this sensitivity, this issue probably cannot be settled unequivocally with observational data. In the absence of a definitive answer, this apparent increased risk, together with its uncertainty and small magnitude and its important consequences, should be considered when selecting an OC for a given woman.

Ethnicity influences morphine pharmacokinetics and pharmacodynamics.

OBJECTIVE: Our objective was to evaluate ethnic differences in response to morphine and to determine whether any detectable differences were pharmacokinetically based. METHODS: This cohort study was carried out in a teaching hospital. Sixty-six young, healthy male subjects from 3 ethnic groups (Caucasians, native Indians, and Latinos; n = 22 in each group) consented to participate. All subjects received an intravenous morphine bolus of 0.08 mg/kg followed by 0.002 mg/kg. min infused for 30 minutes. Respiratory response was evaluated with the carbon dioxide rebreathing method before and at 25, 95, 180, and 360 minutes after morphine administration. Vital signs and opioid side effects were recorded, and serial blood samples were analyzed for morphine, morphine-3-glucuronide, and morphine-6-glucuronide (M6G). RESULTS: All 3 groups had suppression of the ventilatory response to hypercapnia, but the degree of blunting of the ventilatory response differed among groups. Compared with Caucasians, native Indians had an additional 18% reduction in ventilatory response after morphine administration (95% confidence interval, -35% to -2%). The incidence of side effects was similar in all groups (P =.18). Caucasians had higher plasma levels of M6G than did native Indians or Latinos. M6G areas under 6-hour concentration-versus-time curve were as follows: Caucasians, 12,065 +/- 4354; native Indians, 8464 +/- 4809; and Latinos, 9156 +/- 3764 ng. min/mL (P =.03). CONCLUSIONS: Ethnicity influences the response to morphine. Native Indians are more susceptible to morphine depression of the ventilatory response than Caucasians, despite the higher serum M6G levels in Caucasians.

Effect of adherence to newly initiated antiretroviral therapy on plasma viral load.

OBJECTIVE: To determine whether differences in adherence to newly initiated antiretroviral therapy exist between subjects who do and do not achieve undetectable plasma viral loads. DESIGN: Observational cohort study monitoring adherence and virological and immunological parameters over the initial 4 months of therapy with nelfinavir. Adherence was measured using the microelectronic monitoring system (MEMS; APREX Corporation, Menlo Park, California, USA). SETTING: General Clinical Research Center at a tertiary care center. PARTICIPANTS: Forty-one protease inhibitor-naive subjects with viral loads > 10 000 copies/ml newly starting a regimen including nelfinavir, referred from HIV clinics in Philadelphia. MAIN OUTCOME MEASURES: The primary outcome was undetectable viral load (< 50 copies/ml) after 4 months. Secondary measures included changes in viral load and CD4 cell counts. We hypothesized that adherence would be greater in subjects who achieved undetectable viral loads. RESULTS: Adherence was greater in undetectable subjects, who took a median of 93% of prescribed doses [interquartile range (IQR) 84-96%], whereas detectable subjects took a median of 70% (IQR 46-93%). Adherence correlated with viral load decrease (Spearman's rho = 0.38, P < 0.01) and CD4 cell count increase (Spearman's rho = 0.25, P = 0.06). Despite differences between the groups over 4 months of therapy, there were no adherence differences over the first month [undetectables, 95% (IQR 88-98%) versus detectables, 94% (IQR 87-98%), P > 0.50]. CONCLUSIONS: Adherence is important in determining whether or not individuals achieve suppression with a newly initiated antiretroviral regimen. Adherence begins to wane after the first month of therapy. Therefore, closer assessment of adherence particularly after this first month is important.

Inflammatory bowel disease is not associated with an increased risk of lymphoma.

BACKGROUND & AIMS: Previous studies of the risk of lymphoma in inflammatory bowel disease patients have provided conflicting results. This study examines the risk of Hodgkin's and non-Hodgkin's lymphoma among patients with inflammatory bowel disease. METHODS: The authors performed a retrospective cohort study using the General Practice Research Database. Inflammatory bowel disease patients were matched to randomly selected controls on age, sex, and primary care practice. Lymphoma rates were also compared with published age- and sex-specific rates. RESULTS: The study included 6605 patients with Crohn's disease, 10,391 with ulcerative colitis, and 60,506 controls followed for an average of 3.7, 3.9, and 4.4 years, respectively. The incidence of lymphoma was not increased in patients with inflammatory bowel disease (relative risk = 1.20; 95% CI, 0.67-2.06). In subgroup analyses, an increased risk was not observed among patients with Crohn's disease (relative risk = 1.39; 95% CI, 0.50-3.40) or ulcerative colitis (relative risk = 1.11; 95% CI, 0.51-2.19). Compared with inflammatory bowel disease patients not treated with azathioprine or 6-MP, the relative risk of lymphoma among the 1465 inflammatory bowel disease patients treated with these medications (average, 106 mg/day for 2.0 years) was 1.27 (95% CI 0.03-8.20). CONCLUSIONS: Patients with inflammatory bowel disease do not have an increased risk of lymphoma as compared with the general population. Although we cannot completely rule out a modest increased risk of lymphoma with azathioprine or 6-MP therapy, an increased risk was not observed in this cohort.

Effect of transdermal testosterone treatment on serum lipid and apolipoprotein levels in men more than 65 years of age.

PURPOSE: Because the effects of androgen replacement on lipoprotein levels are uncertain, we sought to determine the effect of transdermal testosterone treatment on serum lipid and apolipoprotein levels in elderly men. SUBJECTS AND METHODS: One hundred and eight healthy men more than 65 years of age who had serum testosterone concentrations >1 SD below the mean for young men were randomly assigned to receive either testosterone (54 men; 6 mg/day) or placebo (54 men) transdermally in a double-blind fashion for 36 months. Serum concentrations of lipids and apolipoproteins were measured, and cardiovascular events recorded. RESULTS: Serum total cholesterol concentrations decreased in both the testosterone-treated men and placebo-treated men, but the 3-year mean (+/- SD) decreases in the two groups (testosterone treated, -17 +/- 29 mg/dL; placebo treated, -12 +/- 38 mg/dL) were not significantly different from each other (P = 0.4). Similarly, serum low-density lipoprotein (LDL) cholesterol levels decreased in both treatment groups, but the decreases in the two groups (testosterone treated, -16 +/- 24 mg/dL; placebo treated, -16 +/- 33 mg/dL) were similar (P = 1.0). Levels of high-density lipoprotein (HDL) cholesterol, triglycerides, and apolipoproteins A-I and B did not change. Lipoprotein(a) levels increased in both groups by similar amounts (testosterone treated, 3 +/- 9 mg/dL; placebo treated, 4 +/- 6 mg/dL; P = 1.0). The number of cardiovascular events was small and did not differ significantly between the testosterone-treated men (9 events) and the placebo-treated men (5 events) during the 3-year study (relative risk = 1.8; 95% confidence interval: 0.7 to 5.0). CONCLUSIONS: As compared with placebo, transdermal testosterone treatment of healthy elderly men for 3 years did not affect any of the lipid or apolipoprotein parameters that we measured. The effect of testosterone treatment on cardiovascular events was unclear, because the number of events was small.

Epidemiological investigation of fluoroquinolone resistance in infections due to extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae.

The incidence of infections due to extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae (ESBL-EK) has increased markedly in recent years. Treatment is difficult because of frequent multidrug resistance. Although fluoroquinolones offer effective therapy for ESBL-EK infections, their usefulness is threatened by increasing fluoroquinolone resistance. To identify risk factors for fluoroquinolone resistance in ESBL-EK infections, a case-control study of all patients with ESBL-EK infections from 1 June 1997 through 30 September 1998 was conducted. Of 77 ESBL-EK infections, 43 (55.8%) were resistant to fluoroquinolones. Independent risk factors for fluoroquinolone resistance were fluoroquinolone use (odds ratio [OR], 11.20; 95% confidence interval [CI], 1.99-63.19), aminoglycoside use (OR, 5.83; 95% CI, 1.12-30.43), and long-term care facility residence (OR, 3.39; 95% CI, 1.06-10.83). The genotypes of fluoroquinolone-resistant ESBL-EK isolates were closely related. Efforts should be directed at modification of these risk factors to preserve the utility of fluoroquinolones in the treatment of ESBL-EK infections.

Exposure to soy-based formula in infancy and endocrinological and reproductive outcomes in young adulthood.

CONTEXT: A large body of evidence documents the role of phytoestrogens in influencing hormone-dependent states. Infants fed soy formula receive high levels of phytoestrogens, in the form of soy isoflavones, during a stage of development at which permanent effects are theoretically possible. However, a paucity of data exists on the long-term effects of infant soy formulas. OBJECTIVE: To examine the association between infant exposure to soy formula and health in young adulthood, with an emphasis on reproductive health. DESIGN, SETTING, AND PARTICIPANTS: Retrospective cohort study conducted from March to August 1999 among adults aged 20 to 34 years who, as infants, participated during 1965-1978 in controlled feeding studies conducted at the University of Iowa, Iowa City (248 were fed soy formula and 563 were fed cow milk formula during infancy). MAIN OUTCOME MEASURES: Self-reported pubertal maturation, menstrual and reproductive history, height and usual weight, and current health, compared based on type of formula exposure during infancy. RESULTS: No statistically significant differences were observed between groups in either women or men for more than 30 outcomes. However, women who had been fed soy formula reported slightly longer duration of menstrual bleeding (adjusted mean difference, 0.37 days; 95% confidence interval [CI], 0.06-0.68), with no difference in severity of menstrual flow. They also reported greater discomfort with menstruation (unadjusted relative risk for extreme discomfort vs no or mild pain, 1.77; 95% CI, 1.04-3.00). CONCLUSIONS: Exposure to soy formula does not appear to lead to different general health or reproductive outcomes than exposure to cow milk formula. Although the few positive findings should be explored in future studies, our findings are reassuring about the safety of infant soy formula.

Prevalence and determinants of erectile dysfunction in hemodialysis patients.

BACKGROUND: The prevalence of erectile dysfunction (ED) among patients with end-stage renal disease (ESRD) is not known. METHODS: A cross-sectional study was conducted to determine the prevalence of ED among a community-based hemodialysis (HD) population using a two-stage cluster random sampling design. The presence and severity of ED were assessed among 302 ESRD patients using the self-administered International Index of Erectile Function-5 (IIEF-5). Logistic regression was used to examine and test associations between ED and other medical conditions. RESULTS: The prevalence of any level of ED was 82% (95% CI, 76 to 87%) for all HD subjects. The prevalence of severe ED was 45% (CI, 36 to 55%). Subjects younger than 50 years had a prevalence of ED of 63% (CI, 53 to 71%), while in subjects 50 years or older, it was 90% (CI, 84 to 94%). A multivariable analysis demonstrated increasing age (50 to 59, OR = 2.04, 95% CI, 1.3 to 3.1; 60 to 69, OR = 5.5, 95% CI, 1.9 to 15.6) and diabetes (OR = 2.0, 95% CI, 1.2 to 3.3) to be independently associated with the presence of any level of ED. However, neither the subjects' age nor history of diabetes predicted the severity of ED among subjects with ED. The use of angiotensin-converting enzyme inhibitors (ACEIs) was inversely associated with ED (OR = 0.41, 95% CI, 0.17 to 0.98). Poor functional status (Karnofsky score or the Index of Physical Impairment) was not associated with ED. CONCLUSIONS: ED is extremely prevalent among HD patients. Increasing age, diabetes, and nonuse of ACEIs were associated with higher prevalence of ED. The high prevalence of ED was seen even among patients with good functional status.

The risk of malignancy associated with psoriasis.

OBJECTIVE: To measure the incidence of cancer in patients with psoriasis, stratified by the severity of their disease. DESIGN: A cohort study. SETTING: Administrative claims records obtained from Medicaid programs in 3 US states. PARTICIPANTS: All individuals in the claims database who qualified for 1 of the 5 following groups: severe psoriasis as defined by treatment with systemic medication, less severe psoriasis, severe eczema, history of organ transplantation, and hypertension. MAIN OUTCOME MEASURE: A diagnosis of cancer. RESULTS: Individuals with severe psoriasis were more likely to develop a malignancy than those with hypertension (risk ratio, 1.78; 95% confidence interval [CI], 1.32-2.40). The risk of malignancy in the severe psoriasis group approaches that in patients with organ transplants (risk ratio, 2.12; 95% CI, 1.80-2.50). Most of these cancers were nonmelanoma skin cancers and lymphoproliferative malignancies. Those with less severe psoriasis were only slightly more likely to develop a new malignancy than those with hypertension (risk ratio, 1.13; 95% CI, 1.03-1.25). CONCLUSIONS: Patients with psoriasis are at an increased risk of developing a malignancy compared with patients with hypertension. The increased risk is greatest for those with severe disease (ie, patients with psoriasis treated with systemic agents) and minimal (if an increased risk at all) for those with less severe disease compared with those in the hypertension group. The increased risk is mainly for lymphoproliferative cancers and nonmelanoma skin cancers.

Effectiveness of platelet releasate for the treatment of diabetic neuropathic foot ulcers.

OBJECTIVE: The goal of this study was to specifically estimate the effectiveness of platelet releasate, a widely available treatment administered by a proprietary group of wound care centers (WCCs) for the treatment of diabetic neuropathic foot ulceration. RESEARCH DESIGN AND METHODS: Treatment effectiveness was estimated in a retrospective cohort study controlling for treatment selection bias using logistic regression-derived propensity scores. RESULTS: Platelet releasate was more effective than standard care. The relative risk for a wound to heal after treatment with platelet releasate compared with standard care at a WCC varied from 1.14 (95% CI 1.03-1.27) to 1.59 (1.49-1.70). The effect was greatest in those with the most severe wounds, i.e., large wounds that affect deeper anatomical structures. CONCLUSIONS: Within the limitations of the ability of propensity score analysis to control for selection bias, platelet releasate is more effective than standard therapy. This effect is more pronounced in more severe wounds. Unfortunately, severe wounds have not been evaluated in randomized clinical trials of new interventions. We encourage the inclusion of these patients in future trials.

Risk of acute first myocardial infarction and use of nicotine patches in a general population.

OBJECTIVES: To determine if nicotine patches, both as prescribed and used over-the-counter, increase the risk of first myocardial infarction (MI). BACKGROUND: Although nicotine patches improve smoking cessation rates, case reports have raised the hypothesis that they may increase the risk of MI. METHODS: A population-based case-control study among 68 hospitals in an eight-county region surrounding Philadelphia was performed to determine if nicotine patches increase the risk of first MI. Cases were smokers (current or within the prior year) admitted to all hospitals in the region with a first MI. Controls were smokers (current or within the prior year) without prior MI selected from the same region using random-digit dialing. Data were collected by telephone interviews and chart reviews. The study had 80% power to detect an odds ratio (OR) of 2.5. RESULTS: A total of 653 cases and 2,990 controls were interviewed. There was no association between nicotine patches and MI (OR 0.46; 95% CI: 0.09, 1.47), and the confidence interval (CI) excluded an effect from nicotine patches equal to that from cigarette smoking itself (OR < 2.5). Among those who abstained from smoking, the OR for use of nicotine patches was 0.25 (95% CI: 0.01, 1.67); among those who smoked concomitantly, the OR for patch use was 0.83 (95% CI: 0.09, 3.81). Adjustment for confounding did not alter the study's findings (OR adjusted for confounders that could mask a harmful effect of patches: 0.70; 95% CI: 0.20, 2.46). CONCLUSIONS: Nicotine patches, as used in actual practice, do not appear to be associated with an increased risk of MI.

When data conflict with practice: rethinking the use of prophylactic antibiotics before dental treatment.

Concern is growing about the overuse of antibiotics and the subsequent rise in antibiotic-resistant bacteria. Antibiotics are commonly used to prevent heart valve infections in susceptible patients undergoing dental or other surgical procedures. Although this practice has been standard for nearly 50 years, little evidence exists that it works. This Issue Brief summarizes a population-based study that challenges the link between dental procedures and heart valve infections, and illustrates the difficulty in incorporating new evidence into existing guidelines and longstanding practices.