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Biomedical subjects

Matthew H Samore

Publications and source records attributed to Matthew H Samore.

At least 19 recordsLinked to original sources
PubMed2026

Hidden Burden of a Measles Outbreak Revealed by Genomic and Transmission Models.

Declining childhood vaccination rates have fueled a resurgence of measles in the United States. Surveillance systems may not accurately measure the true extent of outbreaks. As of May 2026, the largest ongoing measles outbreak in the United States originated along the Utah-Arizona border in a community with high vaccine exemption rates and limited engagement with healthcare systems, leading to incomplete testing and reporting. To quantify the true outbreak size, we used two independent approaches with complementary data sources: a phylodynamic analysis and an agent-based model. Both methods found significant underreporting, estimating the true outbreak size to be 3.1- to 4.8-fold larger than reported, with confirmed cases representing only 20.96%-32.5% total infections. These findings suggest that substantial underreporting of measles occurs, especially in tight knit communities. The use of complementary analytical approaches to evaluate completeness of reporting can reveal the extent of measles transmission and aid control efforts.

Journal Article↗
PubMed2006

Use of a personal digital assistant for managing antibiotic prescribing for outpatient respiratory tract infections in rural communities.

OBJECTIVE: To assess the acceptability and usage of a standalone personal digital assistant (PDA)-based clinical decision-support system (CDSS) for the diagnosis and management of acute respiratory tract infections (RTIs) in the outpatient setting. DESIGN: Observational study performed as part of a larger randomized trial in six rural communities in Utah and Idaho from January 2002 to March 2004. Ninety-nine primary care providers received a PDA-based CDSS for use at the point-of-care, and were asked to use the tool with at least 200 patients with suspected RTIs. MEASUREMENTS: Clinical data were collected electronically from the devices at periodic intervals. Providers also completed an exit questionnaire at the end of the study period. RESULTS: Providers logged 14,393 cases using the CDSS, the majority of which (n=7624; 53%) were from family practitioners. Overall adherence with CDSS recommendations for the five most common diagnoses (pharyngitis, otitis media, sinusitis, bronchitis, and upper respiratory tract infection) was 82%. When antibiotics were prescribed (53% of cases), adherence with the CDSS-recommended antibiotic was high (76%). By logistic regression analysis, the odds of adherence with CDSS recommendations increased significantly with each ten cases completed (P=0.001). Questionnaire respondents believed the CDSS was easy to use, and most (44/65; 68%) did not believe it increased their encounter time with patients, regardless of prior experience with PDAs. CONCLUSION: A standalone PDA-based CDSS for acute RTIs used at the point-of-care can encourage better outpatient antimicrobial prescribing practices and easily gather a rich set of clinical data.

Ambulatory Care↗
PubMed2006

Recurrent catheter-related bloodstream infections: Risk factors and outcome.

OBJECTIVE: To identify risk factors for recurrent catheter related bloodstream infections (CR-BSIs). The study was undertaken at the University of Utah Hospital and involved patients who had a CR-BSI followed by catheter removal and reinsertion between January 1998 and February 2002. DESIGN: A retrospective chart review for the cohort study of catheters initially infected, which were then followed to study risk factors for a subsequent infection. Both central line and peripherally inserted central line catheters were included in the study. A recurrent CR-BSI was defined as positive blood cultures after three negative cultures, coupled with positive catheter tip culture or no other evident new source of infection. RESULTS: Twenty-five (34%) of 73 patients had a recurrent CR-BSI. The first CR-BSI occurred a mean of 20.4 days after catheter insertion whereas recurrence developed a mean of 12.1 days after reinsertion (p = 0.392). Coagulase-negative staphylococci (60%) were the most common cause of recurrent infection. The recurrence was more common among the patients who were given blood product transfusion (hazard ratio (HR) 2.3; confidence interval (CI) 1.02-5.67, p = 0.049). In 20 (27%) patients, catheters were changed over a guidewire. The guidewire catheter exchange was not found to be associated with an increased risk of recurrent infection (p = 0.582). CONCLUSION: Catheter replacement to a new site, instead of rewiring, was not shown to decrease the risk for recurrent infection. The transfusion of blood products was associated with an increased risk for recurrent infection.

Adult↗
PubMed2006

Genotypic and phenotypic analysis of Clostridium difficile correlated with previous antibiotic exposure.

To analyze Clostridium difficile susceptibility results and genotypes in relation to antibiotic exposures that precipitated C. difficile-associated diarrhea (CDAD), we examined 83 nosocomial C. difficile isolates recovered at a tertiary care center in Boston, Massachusetts. MICs were determined by E-test methodology using modified Brucella agar. Isolates were genotyped by pulsed-field gel electrophoresis and restriction enzyme analysis. Antibiotic susceptibilities were: ciprofloxacin (0%), clindamycin (59%), trovafloxacin (63%), ceftriaxone (73%), piperacillin/tazobactam (100%), metronidazole (100%), and vancomycin (100%). The two most common strain groups, isolated from a total of 33 patients, were much more likely to be resistant to clindamycin, erythromycin, and trovafloxacin than other strain groups [79% (26 of 33) versus 2% (1 of 50), respectively]. Clindamycin exposure was strongly associated with CDAD caused by isolates that exhibited multiple resistance to clindamycin, erythromycin, and trovafloxacin (prevalence odds ratio, 4.2; 95% confidence interval, 1.1-16.8), whereas other antimicrobials did not yield significant associations. Resistance of specific C. difficile strains to clindamycin and other antimicrobial agents may contribute to their hospital dissemination and explain, in part, the propensity of clindamycin to trigger nosocomial outbreaks.

Adult↗
PubMed2006

Experience with a clinical decision support system in community pharmacies to recommend narrow-spectrum antimicrobials, nonantimicrobial prescriptions, and OTC products to decrease broad-spectrum antimicrobial use.

BACKGROUND: Overuse of antibiotics increases the incidence of bacterial resistance and contributes avoidable costs to the health care system. OBJECTIVE: To determine the feasibility of a protocol-driven community pharmacy intervention that was designed to decrease broad-spectrum antimicrobial (BSA) use in patients with upper respiratory tract infections. METHODS: The intervention involved pharmacists who conducted guided interviews regarding patient symptoms in a cohort of patients with BSA prescription visiting 2 rural community pharmacies during peak respiratory illness season. A clinical decision support system was provided to aid in pharmacist diagnosis and assist in determining if the BSA therapy was appropriate. Upon patient consent, pharmacists attempted to contact primary care providers (PCPs) to confirm the diagnosis and recommend appropriate alternative therapy. RESULTS: There were 192 subjects with prescriptions for BSAs and symptoms of respiratory tract infection. Only 3% of the patients who were approached declined to discuss their symptoms and treatment with the pharmacist. A mean of 3 minutes was required to collect symptom and treatment information from the patients. However, when patients were asked if the pharmacist could contact their PCP to recommend alternative therapy, only 7% (n=4) of patients agreed to the intervention. The PCPs who were contacted by pharmacists were receptive to altering the BSA to first-line antimicrobial therapy such as amoxicillin or doxycycline. CONCLUSION: Despite a description of the importance of the intervention, more than 90% of patients prescribed a BSA declined to permit the community pharmacist to contact the prescriber to discuss first-line therapeutic alternatives. This experience in a pilot study to explore the feasibility of pharmacist intervention at the point of dispensing of a BSA made clear that a successful community pharmacy intervention to reduce BSA use would require an alternative method, perhaps via a collaborative practice protocol that does not require patient consent to make the drug substitution to first-line antibiotic therapy.

Anti-Bacterial Agents↗
PubMed2006

Influenza, Winter Olympiad, 2002.

Prospective surveillance for influenza was performed during the 2002 Salt Lake City Winter Olympics. Oseltamivir was administered to patients with influenza like illness and confirmed influenza, while their close contacts were given oseltamivir prophylactically. Influenza A/B was diagnosed in 36 of 188 patients, including 13 athletes. Prompt management limited the spread of this outbreak.

Acetamides↗
PubMed2005

Hypersensitivity cases associated with drug-eluting coronary stents: a review of available cases from the Research on Adverse Drug Events and Reports (RADAR) project.

OBJECTIVES: We undertook the review of all available cases of hypersensitivity reactions after placement of a drug-eluting stent (DES) and classified potential causes. BACKGROUND: Six months after the approval of the first DES, the Food and Drug Administration (FDA) reported 50 hypersensitivity reactions after stent placement but later concluded these were due to concomitantly prescribed medications such as clopidogrel. Nevertheless, the FDA continued to receive reports of hypersensitivity. METHODS: Reports available from April 2003 through December 2004 for hypersensitivity-like reactions associated with the sirolimus-eluting stent (CYPHER, Cordis Corp., Miami Lakes, Florida) and paclitaxel-eluting stent (TAXUS, Boston Scientific Corp., Natick, Massachusetts) were reviewed. Sources of reports included the FDA's adverse-device-event database, the published literature, and investigators from the Research on Adverse Drug/Device events And Reports (RADAR) project. Causality was assessed using standardized World Health Organization criteria. RESULTS: Of 5,783 reports identified for the DES in the FDA database, 262 unique events included hypersensitivity symptoms. Of these reports, 2 were certainly and 39 unlikely caused by clopidogrel and 1 was certainly, 9 probably, and 13 unlikely caused by the DES. From all sources, we identified 17 distinct cases that were probably or certainly caused by the stent, of which 9 had symptoms that lasted longer than four weeks. Four autopsies confirmed intrastent eosinophilic inflammation, thrombosis, and lack of intimal healing. CONCLUSIONS: The FDA reports and autopsy findings suggest that DES may be a cause of systemic and intrastent hypersensitivity reactions that, in some cases, have been associated with late thrombosis and death.

Coronary Vessels↗
PubMed2005

Mechanisms by which antibiotics promote dissemination of resistant pneumococci in human populations.

Mechanisms by which antimicrobials contribute to dissemination of pneumococcal resistance are incompletely characterized. A serial cross-sectional study of nasopharyngeal pneumococcal carriage in healthy, home-living children <or=6 years of age was conducted in four rural communities-two in Utah (1998-2003) and two in Idaho (2002-2003). Prevalence odds ratios for carriage of resistant pneumococci (OR(res)) and of susceptible pneumococci (OR(sus)) were estimated. Dynamic transmission models were developed to facilitate a mechanistic interpretation of OR(res) and OR(sus) and to compare the population impact of distinct antimicrobial classes. A total of 5,667 cultures were obtained; 25% of the cultures were positive, and 29% of isolates exhibited reduced susceptibility to penicillin. The adjusted OR(res) for recent individual and sibling cephalosporin use was 2.2 (95% confidence interval: 1.4, 3.4) and 1.8 (95% confidence interval: 1.0, 3.3), respectively. Neither individual nor sibling penicillin use was associated with increased OR(res). Rather, recent use of penicillins was associated with decreased carriage of susceptible pneumococci (OR(sus) = 0.2, 95% confidence interval: 0.1, 0.3). In simulations, both types of effects promoted dissemination of resistant pneumococci at the population level. Findings show that oral cephalosporins enhance the risk of acquiring resistant pneumococci. Penicillins accelerate clearance of susceptible strains. The effect of penicillins in increasing resistance is shared equally by treated and untreated members of the population.

Anti-Bacterial Agents↗
PubMed2005

Clinical decision support and appropriateness of antimicrobial prescribing: a randomized trial.

CONTEXT: The impact of clinical decision support systems (CDSS) on antimicrobial prescribing in ambulatory settings has not previously been evaluated. OBJECTIVE: To measure the added value of CDSS when coupled with a community intervention to reduce inappropriate prescribing of antimicrobial drugs for acute respiratory tract infections. DESIGN, PARTICIPANTS AND SETTING: Cluster randomized trial that included 407,460 inhabitants and 334 primary care clinicians in 12 rural communities in Utah and Idaho (6 with 1 shared characteristic and 6 with another), and a third group of 6 communities that served as nonstudy controls. The preintervention period was January to December 2001 and the postintervention period was January 2002 to September 2003. Acute respiratory tract infection diagnoses were classified into groups based on indication for antimicrobial use. Multilevel regression methods were applied to account for the clustered design. INTERVENTION: Six communities received a community intervention alone and 6 communities received community intervention plus CDSS that were targeted toward primary care clinicians. The CDSS comprised decision support tools on paper and a handheld computer to guide diagnosis and management of acute respiratory tract infection. MAIN OUTCOME MEASURE: Community-wide antimicrobial usage was assessed using retail pharmacy data. Diagnosis-specific antimicrobial use was compared by chart review. RESULTS: Within CDSS communities, 71% of primary care clinicians participated in the use of CDSS. The prescribing rate decreased from 84.1 to 75.3 per 100 person-years in the CDSS arm vs 84.3 to 85.2 in community intervention alone, and remained stable in the other communities (P = .03). A total of 13,081 acute respiratory tract infection visits were abstracted. The relative decrease in antimicrobial prescribing for visits in the antibiotics "never-indicated" category during the post-intervention period was 32% in CDSS communities and 5% in community intervention-alone communities (P = .03). Use of macrolides decreased significantly in CDSS communities but not in community intervention-alone communities. CONCLUSION: CDSS implemented in rural primary care settings reduced overall antimicrobial use and improved appropriateness of antimicrobial selection for acute respiratory tract infections. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT00235703.

Acute Disease↗
PubMed2005

Temporal trends of invasive disease due to Streptococcus pneumoniae among children in the intermountain west: emergence of nonvaccine serogroups.

BACKGROUND: Use of the heptavalent pneumococcal conjugate vaccine (PCV-7 [Prevnar]) has been associated with decreased a incidence of invasive pneumococcal disease (IPD) among children in the United States. METHODS: Cases of IPD in children < 18 years of age insured by or receiving health care from Intermountain Health Care during 1996-2003 were identified. Isolates of S. pneumoniae from children with IPD treated at Primary Children's Medical Center (PCMC; Salt Lake City, UT) during 1997-2003 were serogrouped. Temporal trends of IPD, serogroup distribution of pneumococci, and antibiotic resistance among pneumococci were analyzed. RESULTS: A total of 1535 cases of IPD were identified. The rate of IPD decreased 27% after the introduction of PCV7. Among children with IPD who were cared for at PCMC, disease in 73% was caused by PCV7 serogroups in 1997-2000, compared with 50% in 2001-2003 (P < .001), and the percentage of isolates resistant to penicillin decreased from 34% in 1997-2000 to 22% in 2001-2003 (P = .04). The percentage of IPD cases that were empyema increased from 16% to 30% (P = .015), and the percentage of severe cases of IPD increased from 57% to 71% (P = .026). Children with IPD due to non-PCV7 serogroups were older, were more likely to have parapneumonic empyema, and had longer hospital stays. CONCLUSIONS: The incidence of IPD in the IMW decreased by 27% after the introduction of the PCV7 vaccine. During the postvaccine period (2001-2003), there were significant decreases in the proportion of cases of IPD caused by PCV7 and antibiotic-resistant serogroups. These benefits were accompanied by a significant increase in the proportion of IPD cases due to non-PCV7 serogroups, with increases in the incidence of empyema and severe IPD.

Adolescent↗
PubMed2005

Risk factors for adverse drug events: a 10-year analysis.

BACKGROUND: Many adverse drug events (ADEs) are the result of known pharmacologic properties, and some result from medication errors. However, some are the result of patient-specific risk factors. OBJECTIVE: To identify inpatient risk factors for ADEs. METHODS: Conditional logistic regression was used to analyze all pharmacist-verified ADEs by therapeutic class of drugs and severity during a 10-year study period. All inpatients > or = 18 years of age from a 520-bed tertiary teaching hospital were included. Each case patient was matched with up to 16 control patients. Odds ratios for patient factors associated with ADEs were calculated from different therapeutic classes of drugs. RESULTS: Odds ratios for numerous risk factors were identified for 4376 ADEs and were found to vary depending on therapeutic classification. The risk factors for the different classifications were grouped by (1) patient characteristics--female (OR 1.5-1.7), age (0.7-0.9), weight (1.2-1.4), creatinine clearance (0.8-4.7), and number of comorbidities (1.1-12.6); (2) drug administration--dosage (1.2-3.7), administration route (1.4-149.9), and number of concomitant drugs (1.2-2.4); and (3) patient type--service (1.2-4.9), nursing division (1.5-3.8), and diagnosis-related group (1.5-5.7). CONCLUSIONS: Some risk factors are consistent for all ADEs and across multiple therapeutic classes of drugs, while others are class specific. High-risk agents should be closely monitored based on patient characteristics (gender, age, weight, creatinine clearance, number of comorbidities) and drug administration (dosage, administration route, number of concomitant drugs).

Adolescent↗
PubMed2005

The Research on Adverse Drug Events and Reports (RADAR) project.

CONTEXT: In 1998, a multidisciplinary team of investigators initiated RADAR (Research on Adverse Drug events And Reports), a clinically based postmarketing surveillance program that systematically investigates and disseminates information describing serious and previously unrecognized adverse drug and device reactions (ADRs). OBJECTIVE: To describe the structure, operations, and preliminary findings from the RADAR project and related dissemination efforts by pharmaceutical suppliers and the US Food and Drug Administration (FDA). DESIGN: After identifying a serious and unexpected clinical event suitable for further investigation, RADAR collaborators postulated clinical hypotheses and derived case series and incidence estimates from physician queries, published and unpublished clinical trials, published case reports, FDA databases, and manufacturer sales figures. RESULTS: RADAR investigators identified 16 types of serious ADRs among 1699 patients, of whom 169 (10%) died as a result of the reaction. Initial cases were identified by 7 RADAR investigators, 4 collaborating physicians, 2 attorneys, and by reviewing 3 published reports. Additional sources included queries of occupational health programs and medical directors of interventional cardiology laboratories (3 types of ADRs), published manuscripts and clinical trials (11 types of ADRs), review of medical records at a RADAR site (2 types of ADRs), unpublished clinical trial reports (3 types of ADRs), and reports from attorneys, family members, or patients (4 types of ADRs). Incidence estimates, ranging from 0.4% to 33%, were derived from 5 clinical trial reports, 2 physician queries, and 2 observational databases. Laboratory support for hypotheses included identification of 3 neutralizing antibodies and 3 histopathological findings. ADR reports were disseminated as 8 revised package inserts, 7 "dear doctor" letters, and 9 peer-reviewed articles. CONCLUSION: A new, clinically based, hypothesis-driven approach to postmarketing surveillance may supplement existing regulatory surveillance systems and improve patient safety.

Adverse Drug Reaction Reporting Systems↗
PubMed2005

Detection and prevention of medication errors using real-time bedside nurse charting.

OBJECTIVE: Charting systems with decision support have been developed to assist with medication charting, but many of the features of these programs are not properly used in their clinical application. An analysis of medication error reports at LDS Hospital revealed the occurrence of errors that should have been detected and prevented by decision support features if real-time entry at the bedside had taken place. The aim of this study was to increase the real-time bedside charting behavior of nurses. DESIGN: A quasiexperimental before and after design was used. The study took place in two 40-bed surgical units, one of which served as the study unit, the other as control unit. The study unit received educational intervention about error avoidance through real-time bedside charting, and 12 weeks of monitoring and performance feedback. The real-time and bedside charting rates for the study and control units were measured before and after the intervention. RESULTS: Before the intervention on the study unit, the real-time charting rate was 59% and the bedside rate was 40%. At the conclusion of a 12-week intervention period, the real-time rate increased to 73% and the bedside rate increased to 63%. Postintervention real-time rates were 75% after eight weeks and remained at 75% after one year. Equivalent control unit real-time rates varied from 53% to 57%, and bedside rates varied from 34% to 44% during the same intervals. CONCLUSION: Targeted educational intervention and monitored feedback yielded measurable improvements in the effective use of the computerized medication charting system and must be an ongoing process.

Computer Systems↗
PubMed2005

A multifaceted intervention to improve antimicrobial prescribing for upper respiratory tract infections in a small rural community.

BACKGROUND: Antibiotic prescribing for upper respiratory tract infections (URTIs) is widespread, is often inappropriate, and may contribute to antibiotic resistance among community-acquired pathogens, such as Streptococcus pneumoniae. METHODS: A multifaceted intervention involving health care professionals and patients was introduced to a small rural Utah community and included the repetitive use of printed diagnostic and treatment algorithms by professionals. Data on the quantity and class of antibiotic prescribing, which were collected from multiple sources, were measured for the intervention period (from January through June) in 2001 and compared with data for the baseline period during the same months in 2000. RESULTS: Medicaid claims data revealed that the percentage of patients in the community who received antibiotics for URTIs during the intervention period was 15.6% less than that for the baseline period, whereas the percentage in the rest of rural Utah was relatively stable, with a 1.5% decrease (P=.006). The greatest impact of the intervention was on prescribing for acute bronchitis (decreases of 56.1% and 1.7% in the community and rural Utah, respectively; P=.024) and on prescribing of macrolides (decreases of 13.4% and 0.2% in the community and rural Utah, respectively; P<.001). Community pharmacy data likewise revealed a 17.5% decrease in the rate of antibiotic prescribing during the intervention period (P<.001), with the largest decrease observed for macrolide prescribing (50.9%; P<.001). Chart review data, in contrast, revealed no significant decrease in the percentage of patients with URTI who were prescribed an antibiotic (3.8%; P=.49), although there was a significant decrease of 11.2% in macrolide use (P=.045). CONCLUSIONS: A multifaceted intervention involving the repetitive use of printed algorithms resulted in modest improvements in antibiotic prescribing for outpatient URTIs, although one data source did not corroborate this. However, macrolide prescribing decreased sharply, irrespective of the source of data.

Adolescent↗
PubMed2005

Impact of severity of illness bias and control group misclassification bias in case-control studies of antimicrobial-resistant organisms.

BACKGROUND: Case-control studies often analyze risk factors for antibiotic resistance. Recently published articles have illustrated that randomly selected control-patients may be preferable to those with the susceptible phenotype of the organism. A possible methodologic problem with randomly selected control-patients is potential bias due to control group misclassification. This occurs if some control-patients did not have clinical cultures performed and thus might have been unidentified case-patients. If this bias exists, these studies might be expected to report lower odds ratios (ORs) because control-patients would be more like case-patients. OBJECTIVE: To analyze potential biases that might arise due to control group misclassification and potentially larger selection biases that may be introduced if control-patients are required to have at least one clinical culture. PATIENTS: One hundred twenty case-patients, 770 control-patients in group 1, and 510 control-patients in group 2. METHODS: Two case-control studies. Case-patients had clinical cultures positive for imipenem-resistant Pseudomonas aeruginosa. The first group of control-patients were random. The second group of control-patients were identical to those in group 1 except being required to have at least one clinical culture. RESULTS: Univariate analyses showed higher ORs for case-patients versus control-patients in group 1 (imipenem [OR, 12.5], piperacillin-tazobactam [OR, 3.7], and vancomycin [OR, 4.7]) as compared with case-patients versus control-patients in group 2 (imipenem [OR, 8.0], piperacillin-tazobactam [OR, 2.5], and vancomycin [OR, 3.0]). CONCLUSION: Requiring control-patients to have at least one clinical culture introduces a selection bias likely because it eliminates patients with less severe illness.

Anti-Bacterial Agents↗
PubMed2005

Use of strain typing data to estimate bacterial transmission rates in healthcare settings.

OBJECTIVE: To create an affordable and accurate method for continuously monitoring bacterial transmission rates in healthcare settings. DESIGN: We present a discrete simulation model that relies on the relationship between in-hospital transmission rates and strain diversity. We also present a proof of concept application of this model to a prospective molecular epidemiology data set to estimate transmission rates for Pseudomonas aeruginosa and Staphylococcus aureus. SETTING: Inpatient units of an academic referral center. PATIENTS: All inpatients with nosocomial infections. INTERVENTION: Mathematical model to estimate transmission rates. RESULTS: Maximum likelihood estimates for transmission rates of these two species on different hospital units ranged from 0 to 0.36 transmission event per colonized patient per day. CONCLUSIONS: This approach is feasible, although estimates of transmission rates based solely on strain typed clinical cultures may be too imprecise for routine use in infection control. A modest level of surveillance sampling substantially improves the estimation accuracy.

Bacterial Infections↗