Relative Influence of Antibiotic Therapy Attributes on Physician Choice in Treating Acute Uncomplicated Pyelonephritis

Background. Reducing excess duration of antibiotic therapy is a strategy for limiting the spread of antibiotic resistance, but altering physician practice to accomplish this requires knowledge of the factors that influence physician antibiotic choice. The authors aimed to quantify physician willingness to trade between 4 attributes of antibiotic therapies: different therapy durations, failure rates, dosing frequencies, and days of diarrhea as a side effect when treating acute uncomplicated pyelonephritis. Methods. The authors distributed conjoint analysis questionnaires to physicians enrolling patients in a randomized trial comparing 2 antibiotics in pyelonephritis treatment. For each question, respondents were required to select 1 of 2 antibiotics based on the values of the 4 attributes. Proportional hazards regression was used to model predictors of physician choice. Results. Eighty-seven of 88 physicians completed the questionnaire. Duration of therapy, days of diarrhea, and failure rate were significant predictors of choice (P < 0.05), but dosing frequency (once daily v. twice daily) was not. Increasing days of diarrhea greatly reduced the probability of an antibiotic being chosen. If failure and side effects were equivalent, physicians were more likely to prescribe a 5- v. 10-day duration of therapy (odds ratio = 4.18, P < 0.01). Conclusion. Antibiotic choice is most influenced by physicians' desires to limit treatment failure and side effects, although physicians were willing to accept increases in treatment failure to obtain reduced days of diarrhea as a side effect. Because shorter-course therapy is frequently associated with fewer side effects, efforts to encourage physicians to choose shorter treatment durations should include mention of reduced treatment-associated side effects.

Antibiotic Policies and Utilization in Oregon Hospice Programs

Antibiotics are frequently used in hospice care, despite limited data on safety and effectiveness in this patient population. We surveyed Oregon hospice programs on antibiotic policies and prescribing practices. Among 39 responding hospice programs, the median reported proportion of current census using antibiotics was 10% (interquartile range = 3.5%-20.0%). Approximately 31% of responding hospice programs had policies for antibiotic initiation, 17% of hospice programs had policies for antibiotic discontinuation, and 95% of hospice programs had policies for managing drug interactions. Diarrhea, nausea/vomiting, and yeast infections were the most frequently reported antibiotic-associated adverse events, occurring “sometimes” or “often” among 62%, 47%, and 62% of respondents, respectively. In conclusion, less than a third of participating hospice programs reported having a policy for antibiotic initiation and even less frequently a policy for discontinuation. More data are needed on the risks and benefits of antibiotic use in hospice care to inform these policies and optimize outcomes in this vulnerable patient population.

Aspirin use among adults in the U.S.: results of a national survey

INTRODUCTION

The use of aspirin in patients without cardiovascular disease remains controversial. Patients' understanding of the risks and benefits of aspirin likely contribute to the decision of whether or not to use aspirin regularly. The purpose of this study is to assess patients' knowledge of aspirin and identify factors contributing to regular use.

METHODS

A survey of U.S. adults aged 45-75 years was performed to ascertain aspirin use and factors that may be associated with use. Multivariate logistic regression was used to identify predictors of current use of aspirin among those with a primary prevention indication. The survey was completed in 2012 with data analysis performed in 2013.

RESULTS

Among 2,509 respondents, 52% reported current aspirin use. Among 2,039 respondents without a history of cardiovascular disease, current use of aspirin was 47%. Regular use of aspirin for primary prevention was associated with the presence of major cardiovascular disease risk factors (OR=3.0, 95% CI=2.4, 3.7), high self-assessed knowledge of aspirin (OR=9.1, 95% CI=5.2, 15.7), and having discussed aspirin therapy with a provider (OR=25.9, 95% CI=19.7, 34.1). Several markers of healthy lifestyle choices were also associated with regular use. After multivariate analysis, the strongest independent predictor of regular aspirin use was having discussed aspirin therapy with a provider (OR=23.79, 95% CI=17.8, 31.5).

CONCLUSIONS

Approximately half of the nationwide survey of U.S. adults reported regular aspirin use. Among those with a primary prevention indication, having discussed aspirin with a provider was the strongest predictor of regular use.

Optimizing research methods used for the evaluation of antimicrobial stewardship programs

Antimicrobial stewardship programs (ASPs) are an increasingly common intervention for optimizing antimicrobial therapy in healthcare settings. These programs aim to improve patient care and limit the emergence and spread of multidrug-resistant organisms by supporting prudent antimicrobial use. However, pressure from the current reimbursement climate necessitates that ASPs operate as cost-cutting programs rather than focus on patient outcomes. This has forced the research that is evaluating ASP interventions to concentrate heavily on economic outcomes. As the science of antimicrobial stewardship advances, it is essential that well-conducted evaluations, focused on patient and microbial outcomes, serve as the evidence base that directs optimal ASP intervention design and implementation. In this review, we provide guidance and recommendations for the design of studies to evaluate the impact of ASP interventions on patient and microbial outcomes.

Evaluation of collaborative therapy review to improve care of heart failure patients

OBJECTIVES

As more demands are placed on primary care providers, new innovative models are required to optimize heart failure (HF) care. The purpose of this study was to evaluate a collaborative therapy review (CTR) program that was implemented to improve guideline-based therapy among HF outpatients.

STUDY DESIGN AND METHODS

We screened patient lists of 18 PCPs at the Portland Veterans Affairs Medical Center to identify patients with an ICD-9 code for HF. The charts of patients with ejection fractions (EFs) < 40% were then abstracted in more detail. The CTR team reviewed each patient and provided specific guideline-based recommendations. The team then gave specific recommendations to providers through the electronic medical record system. We categorized recommendations relating to drug or device therapies, or need for laboratory testing, and calculated provider acceptance rates by recommendation type.

RESULTS

Of the 641 patients reviewed, 156 patients had detailed chart reviews. We found opportunities for improvement in care in 70 (45%) patients who received 100 recommendations. Among the 100 recommendations, 62 (55%) were for guideline-based drugs, 12 (17%) were for consideration of device therapy, and 26 (24%) were to update lab tests or echocardiograms. Eighty percent of the recommendations were acted on within 90 days.

CONCLUSIONS

The CTR program was able to facilitate guideline-based management for HF patients by identifying treatment gaps and making specific guideline-based recommendations to PCPs. While further evaluations are needed, this approach may serve as an efficient method of leveraging the expertise of specialty-trained clinicians to optimize patient care.

Antimicrobial use for symptom management in patients receiving hospice and palliative care: a systematic review

BACKGROUND

Patients receiving hospice or palliative care often receive antimicrobial therapy; however the effectiveness of antimicrobial therapy for symptom management in these patients is unknown.

OBJECTIVE

The study's objective was to systematically review and summarize existing data on the prevalence and effectiveness of antimicrobial therapy to improve symptom burden among hospice or palliative care patients.

DESIGN

Systematic review of articles on microbial use in hospice and palliative care patients published from January 1, 2001 through June 30, 2011.

MEASUREMENTS

We extracted data on patients' underlying chronic condition and health care setting, study design, prevalence of antimicrobial use, whether symptom response following antimicrobial use was measured, and the method for measuring symptom response.

RESULTS

Eleven studies met our inclusion criteria in which prevalence of antimicrobial use ranged from 4% to 84%. Eight studies measured symptom response following antimicrobial therapy. Methods of symptom assessment were highly variable and ranged from clinical assessment from patients' charts to the Edmonton Symptom Assessment Scale. Symptom improvement varied by indication, and patients with urinary tract infections (two studies) appeared to experience the greatest improvement following antimicrobial therapy (range 67% to 92%).

CONCLUSION

Limited data are available on the use of antimicrobial therapy for symptom management among patients receiving palliative or hospice care. Future studies should systematically measure symptom response and control for important confounders to provide useful data to guide antimicrobial use in this population.

A nationwide analysis of antibiotic use in hospice care in the final week of life

CONTEXT

Antibiotic prescription in hospice patients is complicated by the focus on palliative rather than curative care and concerns regarding increasing antibiotic resistance.

OBJECTIVES

To estimate the antibiotic use in a national sample of hospice patients and identify facility and patient characteristics associated with antibiotic use in this population.

METHODS

This was an analysis of data from the 2007 National Home and Hospice Care Survey, a nationally representative sample of U.S. hospice agencies. We included data from 3884 patients who died in hospice care. The primary outcome measure was prevalence of antibiotic use in the last seven days of life. Diagnoses, including potential infectious indications for antibiotic use, were defined using International Classification of Diseases, Ninth Revision (ICD-9) codes. Chi-squared tests and t-tests were used to quantify associations of patient and facility characteristics with antibiotic use.

RESULTS

During the last seven days of life, 27% (95% CI: 24%-30%) of patients received at least one antibiotic and 1.3% (95% CI: 0.7%-2.0%) received three or more antibiotics. Among patients who received at least one antibiotic, 15% (95% CI: 10%-20%) had a documented infectious diagnosis compared with 9% (95% CI: 7%-11%), who had an infectious diagnosis but received no antibiotics.

CONCLUSION

In this nationally representative sample, 27% of hospice patients received an antibiotic during the last seven days of life, most without a documented infectious diagnosis. Further research is needed to elucidate the role of antibiotics in this patient population to maintain palliative care goals while reducing unnecessary antibiotic use.

Quality of hospice care for individuals with dementia

BACKGROUND

Patients with dementia constitute an increasing proportion of hospice enrollees, yet little is known about the quality of hospice care for this population. The aim of this study was to quantify differences in quality of care measures between hospice patients with and without dementia.

DESIGN

Cross-sectional analysis of data.

SETTING

2007 National Home and Hospice Care Survey.

PARTICIPANTS

Four thousand seven hundred eleven discharges from hospice care.

MEASUREMENTS

A primary diagnosis of dementia at discharge was defined according to International Classification of Diseases, Ninth Revision, codes (290.0-290.4x, 294.0, 294.1, 294.8, 331.0-331.2, 331.7, and 331.8). Quality-of-care measures included enrollment in hospice in the last 3 days of life, receiving tube feeding, depression, receiving antibiotics, lack of advanced directive or do not resuscitate order, Stage II or greater pressure ulcers, emergency care, lack of continuity of residence, and a report of pain at last assessment.

RESULTS

Four hundred fifty (9.5%) individuals were discharged with a primary diagnosis of dementia. In multivariable analysis, individuals with dementia were more likely to receive tube feeding (odds ratio (OR) = 2.6, 95% confidence interval (CI) = 1.4-4.5) and to have greater continuity of residence (OR = 1.8, 95% CI = 1.1-3.0) than other individuals in hospice and less likely to have a report of pain at last assessment (OR = 0.6, 95% CI = 0.3-0.9).

CONCLUSIONS

The majority of quality-of-care measures examined did not differ between individuals in hospice with and without dementia. Use of tube feeding in hospice care and methods of pain assessment and treatment in individuals with dementia should be considered as potential quality-of-care measures.

Risk of acquiring extended-spectrum β-lactamase-producing Klebsiella species and Escherichia coli from prior room occupants in the intensive care unit

OBJECTIVE. To quantify the association between admission to an intensive care unit (ICU) room most recently occupied by a patient positive for extended-spectrum β-lactamase (EBSL)-producing gram-negative bacteria and acquisition of infection or colonization with that pathogen. DESIGN. Retrospective cohort study. SETTING AND PATIENTS. The study included patients admitted to medical and surgical ICUs of an academic medical center between September 1, 2001, and June 30, 2009. METHODS. Perianal surveillance cultures were obtained at admission to the ICU, weekly, and at discharge from the ICU. Patients were included if they had culture results that were negative for ESBL-producing gram-negative bacteria at ICU admission and had an ICU length of stay longer than 48 hours. Pulsed-field gel electrophoresis (PFGE) was performed on ESBL-positive isolates from patients who acquired the same bacterial species (eg, Klebsiella species or Escherichia coli) as the previous room occupant. RESULTS. Among 9,371 eligible admissions (7,651 unique patients), 267 (3%) involved patients who acquired an ESBL-producing pathogen in the ICU; of these patients, 32 (12%) were hospitalized in a room in which the prior occupant had been positive for ESBL. Logistic regression results suggested that the prior occupant's ESBL status was not significantly associated with acquisition of an ESBL-producing pathogen (adjusted odds ratio, 1.39 [95% confidence interval, 0.94-2.08]) after adjusting for colonization pressure and antibiotic exposure in the ICU. PFGE results suggested that 6 (18%) of 32 patients acquired a bacterial strain that was the same as or closely related to the strain obtained from the prior occupant. CONCLUSIONs. These data suggest that environmental contamination may not play a substantial role in the transmission of ESBL-producing pathogens among ICU patients. Intensifying environmental decontamination may be less effective than other interventions in preventing transmission of ESBL-producing pathogens.

Use of electronic health record data to identify skin and soft tissue infections in primary care settings: a validation study

Background

Epidemiologic studies of skin and soft tissue infections (SSTIs) depend upon accurate case identification. Our objective was to evaluate the positive predictive value (PPV) of electronic medical record data for identification of SSTIs in a primary care setting.

Methods

A validation study was conducted among primary care outpatients in an academic healthcare system. Encounters during four non-consecutive months in 2010 were included if any of the following were present in the electronic health record: International Classification of Diseases, Ninth Revision (ICD-9) code for an SSTI, Current Procedural Terminology (CPT) code for incision and drainage, or a positive wound culture. Detailed chart review was performed to establish presence and type of SSTI. PPVs and 95% confidence intervals (CI) were calculated among all encounters, initial encounters, and cellulitis/abscess cases.

Results

Of the 731 encounters included, 514 (70.3%) were initial encounters and 448 (61.3%) were cellulitis/abscess cases. When the presence of an ICD-9 code, CPT code, or positive culture was used to identify SSTIs, 617 encounters were true positives, yielding a PPV of 84.4% [95% CI: 81.8–87.0%]. The PPV for using ICD-9 codes alone to identify SSTIs was 90.7% [95 % CI: 88.5–92.9%]. For encounters with cellulitis/abscess codes, the PPV was 91.5% [95% CI: 88.9–94.1%].

Conclusions

ICD-9 codes may be used to retrospectively identify SSTIs with a high PPV. Broadening SSTI case identification with microbiology data and CPT codes attenuates the PPV. Further work is needed to estimate the sensitivity of this method.

Comparison of antibiograms developed for inpatients and primary care outpatients

To support antimicrobial stewardship, some healthcare systems have begun creating outpatient antibiograms. We developed inpatient and primary care outpatient antibiograms for a regional health maintenance organization (HMO) and academic healthcare system (AHS). Antimicrobial susceptibilities from 16,428 Enterococcus, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa cultures from 2010 were summarized and compared. Methicillin susceptibility among S. aureus was similar in inpatients and primary care outpatients (HMO: 61.2% versus 61.9%, P = 0.951; AHS: 62.9% versus 63.3%, P > 0.999). E. coli susceptibility to trimethoprim/sulfamethoxazole was also similar (HMO: 81.8% versus 83.6%, P = 0.328; AHS: 77.2% versus 80.9%, P = 0.192), but ciprofloxacin susceptibility differed (HMO: 88.9% versus 94.6%, P < 0.001; AHS: 81.2% versus 90.6%, P < 0.001). In the HMO, ciprofloxacin-susceptible P. aeruginosa were more frequent in primary care outpatients than in inpatients (91.4% versus 79.0%, P = 0.007). Comparison of cumulative susceptibilities across settings yielded no consistent patterns; therefore, outpatient primary care antibiograms may more accurately inform prudent empiric antibiotic prescribing.

Sex- and age-specific trends in antibiotic resistance patterns of Escherichia coli urinary isolates from outpatients

Background

Urinary tract infections (UTIs) are one of the most common infections treated in ambulatory care settings, however the epidemiology differs by age and sex. The incidence of UTI is far greater in females than males, and infection in pediatric patients is more often due to anatomical abnormalities. The purpose of this research was to describe age- and sex-specific trends in antibiotic susceptibility to common urinary anti-infectives among urinary isolates of Escherichia coli from ambulatory primary care patients in a regional health maintenance organization.

Methods

Clinical microbiology data were collected for all urine cultures from patients with visits to primary care clinics in a regional health maintenance organization between 2005 and 2010. The first positive culture for E. coli tested for antibiotic susceptibilities per patient per year was included in the analysis dataset. The frequency of susceptibility to ampicillin, amoxicillin-clavulanate, ciprofloxacin, nitrofurantoin, and trimethoprim/sulfamethoxazole (TMP/SMX) was calculated for male and female patients. The Cochrane-Mantel-Haenzel test was used to test for differences in age-stratified susceptibility to each antibiotic between males and females.

Results

A total of 43,493 E. coli isolates from 34,539 unique patients were identified for study inclusion. After stratifying by age, E. coli susceptibility to ampicillin, amoxicillin-clavulanate, ciprofloxacin, and nitrofurantoin differed significantly between males and females. However, the magnitude of the differences was less than 10% for all strata except amoxicillin-clavulanate susceptibility in E. coli isolated from males age 18–64 compared to females of the same age.

Conclusions

We did not observe clinically meaningful differences in antibiotic susceptibility to common urinary anti-infectives among E. coli isolated from males versus females. These data suggest that male sex alone should not be used as an indication for empiric use of second-line broad-spectrum antibiotic agents for the treatment of UTIs.

Risk factors associated with linezolid-nonsusceptible enterococcal infections

Linezolid is one of few treatment options available for vancomycin-resistant enterococci. The present study investigated risk factors for linezolid-nonsusceptible enterococci using a case-control study of 15 cases and 60 control patients. Previous hospitalization, admission to a medical service, comorbidity, and linezolid and sulfonamide therapy were identified as risk factors.

Generic substitution of lamotrigine among medicaid patients with diverse indications: a cohort-crossover study

BACKGROUND

Controversy exists about the safety of substituting generic antiepileptic drugs (AEDs). Lamotrigine, the prototypical newer AED, is often used for psychiatric and neurological conditions other than epilepsy. The safety of generic substitution of lamotrigine in diverse populations of AED users is unclear.

OBJECTIVE

The objective of this study was to evaluate potential associations between generic substitution of lamotrigine and adverse consequences in a population of diverse users of this drug.

STUDY DESIGN

This study was a retrospective cohort-crossover design using state Medicaid claims data from July 2006 through June 2009.

METHODS

Subjects were included in the cohort if they converted from brand to generic lamotrigine and had 2 years of lamotrigine use prior to conversion. The frequency of emergency department (ED) visits, hospitalizations and condition-specific ED visits or hospitalizations were recorded in the 60 days immediately following the conversion to generic lamotrigine, then compared with the incidence of the same events during a randomly selected time period indexed to one of the patient's past refills of branded lamotrigine. Multivariate conditional logistic regression was used to quantify the association between generic conversion and health services utilization while controlling for changes in lamotrigine dose and concurrent drug use.

RESULTS

Of the 616 unique subjects included in this analysis, epilepsy was the most common diagnosis (41%), followed by bipolar disorder (32%), pain (30%) and migraine (18%). Conversion to generic lamotrigine was not associated with a statistically significant increase in the odds of an ED visit (adjusted odds ratio [AOR] = 1.35; 95% confidence interval [CI] 0.92, 1.97), hospitalization (AOR = 1.21; 95% CI 0.60, 2.50) or condition-specific encounter (AOR 1.75; 95 CI 0.87, 3.51).

CONCLUSIONS

A statistically significant increase in ED visits, hospitalizations or condition-specific encounters was not observed following the switch from brand to generic lamotrigine, although a type II error cannot be ruled out.

Risk factors for development of intestinal colonization with imipenem-resistant Pseudomonas aeruginosa in the intensive care unit setting

Risk factors for development of intestinal colonization by imipenem-resistant Pseudomonas aeruginosa (IRPA) may differ between those who acquire the organism via patient-to-patient transmission versus by antibiotic selective pressure. The aim of this study was to quantify potential risk factors for the development of IRPA not due to patient-to-patient transmission.

Comparative effectiveness of nafcillin or cefazolin versus vancomycin in methicillin-susceptible Staphylococcus aureus bacteremia

Background

The high prevalence of methicillin-resistant S. aureus (MRSA) has led clinicians to select antibiotics that have coverage against MRSA, usually vancomycin, for empiric therapy for suspected staphylococcal infections. Clinicians often continue vancomycin started empirically even when methicillin-susceptible S. aureus (MSSA) strains are identified by culture. However, vancomycin has been associated with poor outcomes such as nephrotoxicity, persistent bacteremia and treatment failure. The objective of this study was to compare the effectiveness of vancomycin versus the beta-lactam antibiotics nafcillin and cefazolin among patients with MSSA bacteremia. The outcome of interest for this study was 30-day in-hospital mortality.

Methods

This retrospective cohort study included all adult in-patients admitted to a tertiary-care facility between January 1, 2003 and June 30, 2007 who had a positive blood culture for MSSA and received nafcillin, cefazolin or vancomycin. Cox proportional hazard models were used to assess independent mortality hazards comparing nafcillin or cefazolin versus vancomycin. Similar methods were used to estimate the survival benefits of switching from vancomycin to nafcillin or cefazolin versus leaving patients on vancomycin. Each model included statistical adjustment using propensity scores which contained variables associated with an increased propensity to receive vancomycin.

Results

267 patients were included; 14% (38/267) received nafcillin or cefazolin, 51% (135/267) received both vancomycin and either nafcillin or cefazolin, and 35% (94/267) received vancomycin. Thirty (11%) died within 30 days. Those receiving nafcillin or cefazolin had 79% lower mortality hazards compared with those who received vancomycin alone (adjusted hazard ratio (HR): 0.21; 95% confidence interval (CI): 0.09, 0.47). Among the 122 patients who initially received vancomycin empirically, those who were switched to nafcillin or cefazolin (66/122) had 69% lower mortality hazards (adjusted HR: 0.31; 95% CI: 0.10, 0.95) compared to those who remained on vancomycin.

Conclusions

Receipt of nafcillin or cefazolin was protective against mortality compared to vancomycin even when therapy was altered after culture results identified MSSA. Convenience of vancomycin dosing may not outweigh the potential benefits of nafcillin or cefazolin in the treatment of MSSA bacteremia.

Systematic review of measurement and adjustment for colonization pressure in studies of methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, and clostridium difficile acquisition

OBJECTIVE

Colonization pressure is an important infection control metric. The aim of this study was to describe the definition and measurement of and adjustment for colonization pressure in nosocomial-acquisition risk factor studies of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and Clostridium difficile.

METHODS

We performed a computerized search of studies of nosocomial MRSA, VRE, and C. difficile acquisition published before July 1, 2009, through MEDLINE. Studies were included if a study outcome was MRSA, VRE, or C. difficile acquisition; the authors identified risk factors associated with MRSA, VRE, or C. difficile acquisition; and the study measured colonization pressure.

RESULTS

The initial MEDLINE search yielded 505 articles. Sixty-six of these were identified as studies of nosocomial MRSA, VRE, or C. difficile acquisition; of these, 18 (27%) measured colonization pressure and were included in the final review. The definition of colonization pressure varied considerably between studies: the proportion of MRSA- or VRE-positive patients (5 studies), the proportion of MRSA- or VRE-positive patient-days (6 studies), or the total or mean number of MRSA-, VRE-, or C. difficile-positive patients or patient-days (7 studies) in the unit over periods of varying length. In 10 of 13 studies, colonization pressure was independently associated with MRSA, VRE, or C. difficile acquisition.

CONCLUSION

There is a need for a simple and consistent method to quantify colonization pressure in both research and routine clinical care to accurately assess the effect of colonization pressure on cross-transmission of antibiotic-resistant bacteria.

Prevalence of antimicrobial-resistant bacteria isolated from older versus younger hospitalized adults: results of a two-centre study

OBJECTIVES

To compare the proportion of antimicrobial-resistant strains among bacterial isolates from younger and older hospital patients and to quantify changes in the proportion of antimicrobial-resistant strains in both groups over time.

PATIENTS AND METHODS

A retrospective analysis of microbiology data from two centres in Maryland and Chicago was performed. Adult hospital inpatients with positive clinical cultures for specific antimicrobial-resistant bacterial pathogens between 1999 and 2005 (55 427 isolates) were included. The proportions of isolates not susceptible to specific antimicrobial agents were compared between patients > or =65 and <65 years. Additional analyses examined temporal trends in the frequency of resistance and the frequency of resistance among the oldest patients (> or =80 years), in bacteria isolated from blood cultures and in bacteria obtained from intensive care unit patients.

RESULTS

Heterogeneity was observed in the frequency of resistance among different bacteria between older and younger patients, between the two centres and over the study period. Staphylococcus aureus isolates were more likely to be resistant to methicillin when obtained from older patients at Chicago (50.9% versus 40.9%; P < 0.001). In contrast, younger patients yielded a greater proportion of enterococci resistant to vancomycin at Maryland (19.4% versus 16.5%; P = 0.009). Results were variable when resistance to fluoroquinolones, cephalosporins and imipenem were compared for Pseudomonas aeruginosa, Escherichia coli and Klebsiella spp.

CONCLUSIONS

Overall, advanced patient age was not uniformly associated with a greater likelihood of antimicrobial resistance among all bacterial pathogens. Moreover, the frequency of resistance in older and younger patients varied considerably at the two sites over the study period. Variability in the frequency of resistance precludes simplistic conclusions regarding the relationship between age and resistance.

Summer Peaks in the Incidences of Gram-Negative Bacterial Infection Among Hospitalized Patients

OBJECTIVE

Recognition of seasonal trends in hospital infections may improve diagnosis, use of empirical therapy, and infection prevention interventions. There are very few data available regarding the seasonal variability of these infections. We quantified the seasonal variation in the incidences of hospital infection caused by common bacterial pathogens and estimated the association between temperature changes and infection rates.

METHODS

A cohort of all adult patients admitted to the University of Maryland Medical Center during the period from 1998 through 2005 was analyzed. Time-series analyses were used to estimate the association of the number of infections per month caused by Pseudomonas aeruginosa, Acinetobacter baumannii, Enterobacter cloacae, Escherichia coli, Staphylococcus aureus, and enterococci with season and temperature, while controlling for long-term trends.

RESULTS

There were 218,594 admissions to the index hospital, and analysis of 26,624 unique clinical cultures that grew the organisms of interest identified increases in the mean monthly rates of infection caused by P. aeruginosa (28% of isolates recovered; P ! .01), E. cloacae (46%; P ! .01), E. coli (12%; P ! .01), and A. baumannii (21%; Pp.06). For each 10 degrees F increase, we observed a 17% increase in the monthly rates of infection caused by P. aeruginosa (Pp.01) and A. baumanii (Pp.05).

CONCLUSION

Significantly higher rates of gram-negative infection were observed during the summer months, compared with other seasons. For some pathogens, higher temperatures were associated with higher infection rates, independent of seasonality. These findings have important implications for infection prevention, such as enhanced surveillance during the warmer months, and for choice of empirical antimicrobial therapy among hospitalized adults. Future, quasi-experimental investigations of gram-negative infection prevention initiatives should control for seasonal variation.

Controlling for severity of illness in outcome studies involving infectious diseases: impact of measurement at different time points

BACKGROUND

Severity of illness is an important confounder in outcome studies involving infectious diseases. However, it is unclear whether the time at which severity of illness is measured is important.

METHODS

We performed a retrospective study of 328 episodes of gram-negative bacteremia in adult patients to assess the impact of the time of measurement of severity of illness on the association between empirical antimicrobial therapy received and in-hospital mortality. Using a modified Acute Physiology Score (APS), severity of illness was measured at 2 time points: (1) hospital admission and (2) 24 hours before the first culture-positive blood sample was collected. Multivariate logistic regression was used to estimate the impact of adjusting for the APS on the relationship between empirical therapy received (ie, the exposure) and in-hospital mortality (ie, the outcome).

RESULTS

The mean APS (+/- standard deviation) of patients with bacteremia increased during their hospital stay (from 19.2 +/- 11.6 at admission to 24.2 +/- 13.6 at the second time point; P < .01). When examining the association between empirical antimicrobial therapy received and in-hospital mortality, and controlling for the APS, there was a trend toward a decreased impact of appropriate therapy received on in-hospital mortality. The unadjusted odds ratio (OR) for the association between appropriate therapy received and in-hospital mortality was 0.83 (95% confidence interval [CI], 0.51-1.34). After controlling for the APS at admission, this association was attenuated (OR, 0.94 [95% CI, 0.57-1.55]), and when a change in the APS was also included in the multivariate logistic regression model, the association was further attenuated (OR, 0.99 [95% CI, 0.58-1.69]).

CONCLUSIONS

The magnitude of the association between appropriate antimicrobial therapy received and in-hospital mortality among patients with gram-negative bacteremia was sensitive to the timing of adjustment for severity of illness.

Clinical utility of infection control documentation of prior methicillin-resistant Staphylococcus aureus colonization or infection for optimization of empirical antibiotic therapy

This 5-year study of 25,378 hospitalizations measured the utility of infection control documentation of prior methicillin-resistant Staphylococcus aureus (MRSA) colonization or infection for the optimization of empirical antibiotic therapy. Documented prior MRSA colonization or infection was predictive of subsequent MRSA infections (odds ratio, 4.05). Physicians appear to use this documentation when prescribing empirical therapy for suspected bacteremia.

Levofloxacin in the treatment of complicated urinary tract infections and acute pyelonephritis

Levofloxacin is a widely used fluoroquinolone approved for the treatment of complicated urinary tract infections and acute pyelonephritis. A comprehensive review of the medical literature identified five publications evaluating levofloxacin for the treatment of either complicated urinary tract infections or acute pyelonephritis. All trials, although variable in their inclusion criteria and levofloxacin dosing strategies, reported microbiologic, clinical, and safety-related outcomes. High microbiologic eradication rates, ranging from 79.8% to 95.3%, were observed in all studies. Escherichia coli was the most commonly isolated uropathogen. Data on levofloxacin resistance, both at baseline and after therapy, were limited. Clinical success was observed to range from 82.6% to 93% when measured after the completion of therapy. These clinical and microbiologic results were comparable to the fluoroquinolone comparators in all trials. Insufficient data are available to evaluate the outcomes in any meaningful patient subgroups, including catheterized patients, and those with other specific complicating factors. Levofloxacin was well tolerated in these studies, with headache, gastrointenstinal effects, and dizziness being the most commonly reported adverse events. The published data support the use of levofloxacin in complicated urinary tract infections and acute pyelonephritis. Further trials are necessary to evaluate levofloxacin within specific patient sub-populations.

Impact of empiric antimicrobial therapy on outcomes in patients with Escherichia coli and Klebsiella pneumoniae bacteremia: a cohort study

BACKGROUND

It is unclear whether appropriate empiric antimicrobial therapy improves outcomes in patients with bacteremia due to Escherichia coli or Klebsiella. The objective of this study is to assess the impact of appropriate empiric antimicrobial therapy on in-hospital mortality and post-infection length of stay in patients with Escherichia coli or Klebsiella bacteremia while adjusting for important confounding variables.

METHODS

We performed a retrospective cohort study of adult patients with a positive blood culture for E. coli or Klebsiella between January 1, 2001 and June 8, 2005 and compared in-hospital mortality and post-infection length of stay between subjects who received appropriate and inappropriate empiric antimicrobial therapy. Empiric therapy was defined as the receipt of an antimicrobial agent between 8 hours before and 24 hours after the index blood culture was drawn and was considered appropriate if it included antimicrobials to which the specific isolate displayed in vitro susceptibility. Data were collected electronically and through chart review. Survival analysis was used to statistically assess the association between empiric antimicrobial therapy and outcome (mortality or length of stay). Multivariable Cox proportional hazards models were used to calculate hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

Among 416 episodes of bacteremia, 305 (73.3%) patients received appropriate empiric antimicrobial therapy. Seventy-one (17%) patients died before discharge from the hospital. The receipt of appropriate antimicrobial agents was more common in hospital survivors than in those who died (p = 0.04). After controlling for confounding variables, there was no association between the receipt of appropriate empiric antimicrobial therapy and in-hospital mortality (HR, 1.03; 95% CI, 0.60 to 1.78). The median post-infection length of stay was 7 days. The receipt of appropriate antimicrobial agents was not associated with shortened post-infection length of stay, even after controlling for confounding (HR, 1.11; 95% CI 0.86 to 1.44).

CONCLUSION

Appropriate empiric antimicrobial therapy for E. coli and Klebsiella bacteremia is not associated with lower in-hospital mortality or shortened post-infection length of stay. This suggests that the choice of empiric antimicrobial agents may not improve outcomes and also provides data to support a randomized trial to test the hypothesis that use (and overuse) of broad-spectrum antibiotics prior to the availability of culture results is not warranted.

Economics of infection control surveillance technology: cost-effective or just cost?

BACKGROUND

Previous studies have suggested that informatics tools, such as automated alert and decision support systems, may increase the efficiency and quality of infection control surveillance. However, little is known about the cost-effectiveness of these tools.

METHODS

We focus on 2 types of economic analyses that have utility in assessing infection control interventions (cost-effectiveness analysis and business-case analysis) and review the available literature on the economics of computerized infection control surveillance systems.

RESULTS

Previous studies on the effectiveness of computerized infection control surveillance have been limited to assessments of whether these tools increase the sensitivity and specificity of surveillance over traditional methods. Furthermore, we identified only 2 studies that assessed the costs associated with computerized infection control surveillance. Thus, it remains unknown whether computerized infection control surveillance systems are cost-effective and whether use of these systems improves patient outcomes.

CONCLUSION

The existing data are insufficient to allow for a summary conclusion on the cost-effectiveness of infection control surveillance technology. All future studies of computerized infection control surveillance systems should aim to collect outcomes and economic data to inform decision making and assist hospitals with completing business-cases analyses.

Risk factors for colonization with extended-spectrum beta-lactamase-producing bacteria and intensive care unit admission

Coexisting conditions and previous antimicrobial drug exposure predict colonization.

Extended-spectrum β-lactamase (ESBL)–producing bacteria are emerging pathogens. To analyze risk factors for colonization with ESBL-producing bacteria at intensive care unit (ICU) admission, we conducted a prospective study of a 3.5-year cohort of patients admitted to medical and surgical ICUs at the University of Maryland Medical Center. Over the study period, admission cultures were obtained from 5,209 patients. Of these, 117 were colonized with ESBL-producing Escherichia coli and Klebsiella spp., and 29 (25%) had a subsequent ESBL-positive clinical culture. Multivariable analysis showed the following to be statistically associated with ESBL colonization at admission: piperacillin-tazobactam (odds ratio [OR] 2.05, 95% confidence interval [CI] 1.36–3.10), vancomycin (OR 2.11, 95% CI 1.34–3.31), age >60 years (OR 1.79, 95% CI 1.24–2.60), and chronic disease score (OR 1.15; 95% CI 1.04–1.27). Coexisting conditions and previous antimicrobial drug exposure are thus predictive of colonization, and a large percentage of these patients have subsequent positive clinical cultures for ESBL-producing bacteria.

Predictors of 30-day mortality among patients with Pseudomonas aeruginosa bloodstream infections: impact of delayed appropriate antibiotic selection

Although a growing number of studies have found a relationship between delayed appropriate antibiotic therapy and mortality, few have attempted to quantify the temporal association between delayed appropriate antibiotic therapy and mortality. This study was designed to measure the elapsed time associated with an increased risk of 30-day mortality among patients with Pseudomonas aeruginosa bacteremia. The retrospective cohort study was conducted among immunocompetent, adult patients with P. aeruginosa bacteremia onset at least 2 days after hospital admission between 1 January 2001 and 30 September 2006. Classification and regression tree analysis (CART) was used to identify the delay in appropriate antibiotic therapy that was associated with an increased risk of 30-day mortality. During the study period, 100 patients met the inclusion criteria. The CART-derived breakpoint between early and delayed treatment was 52 h. The delayed treatment group experienced a >2-fold significant increase in 30-day mortality compared to the early treatment group (44 and 19%, respectively, P = 0.008). Delayed appropriate therapy of >52 h (odds ratio [OR] = 4.1; 95% confidence interval [CI] 1.2 to 13.9, P = 0.03) was independently associated with 30-day mortality in the multivariate analysis. Antibiotic resistance > or =3 classes (adjusted OR [AOR] = 4.6; 95% CI = 1.9 to 11.2, P = 0.001) and chronic obstructive pulmonary disease (AOR = 5.4; 95% CI = 1.5 to 19.7, P = 0.01) were independently associated with delayed appropriate therapy of >52 h. The data strongly suggest that delaying appropriate therapy for approximately 2 days significantly increases the risk of 30-day mortality in patients with P. aeruginosa bloodstream infections.

A systematic review of the methods used to assess the association between appropriate antibiotic therapy and mortality in bacteremic patients

Studies of the association between inappropriate antibiotic therapy and mortality among bacteremic patients have generated conflicting findings. We systematically reviewed these studies to identify methodological heterogeneity that may explain the lack of agreement. We identified 51 articles that met the inclusion criteria, and we extracted the following data: study design, definition and measurement of variables, and statistical methods. Only 8 studies (16%) defined inappropriate antibiotic therapy as that which was inactive in vitro against the isolated organism(s) and not consistent with current clinical practice recommendations and distinguished between empiric and definitive treatment. Thirty-four studies (67%) measured the severity of illness, but only 6 (12%) specified the time at which it was measured. The methodological recommendations suggested in this article are intended to improve the validity and generalizability of future research. In brief, future studies should define "inappropriate" therapy on the basis of in vitro susceptibility data, should separately evaluate empiric and definitive therapy, and should control for the baseline severity of illness.

Value of performing active surveillance cultures on intensive care unit discharge for detection of methicillin-resistant Staphylococcus aureus

OBJECTIVE

To quantify the value of performing active surveillance cultures for detection of methicillin-resistant Staphylococcus aureus (MRSA) on intensive care unit (ICU) discharge.

DESIGN

Prospective cohort study.

SETTING

Medical ICU (MICU) and surgical ICU (SICU) of a tertiary care hospital.

PARTICIPANTS

We analyzed data on adult patients who were admitted to the MICU or SICU between January 17, 2001, and December 31, 2004. All participants had a length of ICU stay of at least 48 hours and had surveillance cultures of anterior nares specimens performed on ICU admission and discharge. Patients who had MRSA-positive clinical cultures in the ICU were excluded.

RESULTS

Of 2,918 eligible patients, 178 (6%) were colonized with MRSA on ICU admission, and 65 (2%) acquired MRSA in the ICU and were identified by results of discharge surveillance cultures. Patients with MRSA colonization confirmed by results of discharge cultures spent 853 days in non-ICU wards after ICU discharge, which represented 27% of the total number of MRSA colonization-days during hospitalization in non-ICU wards for patients discharged from the ICU.

CONCLUSIONS

Surveillance cultures of nares specimens collected at ICU discharge identified a large percentage of MRSA-colonized patients who would not have been identified on the basis of results of clinical cultures or admission surveillance cultures alone. Furthermore, these patients were responsible for a large percentage of the total number of MRSA colonization-days during hospitalization in non-ICU wards for patients discharged from the ICU.

Impact of empiric antibiotic therapy on outcomes in patients with Pseudomonas aeruginosa bacteremia

The impact of appropriate empirical antimicrobial therapy for Pseudomonas aeruginosa bacteremia on patient outcomes has not been clearly established. We assessed the effect of appropriate empirical therapy on in-hospital mortality and length of stay (LOS) among patients with P. aeruginosa bacteremia. This was a retrospective cohort study of inpatients with a positive blood culture for P. aeruginosa between January 2001 and June 2005. Empirical therapy was defined as appropriate if the patient received an antibiotic the organism was susceptible to between 8 h before culture collection and the time the susceptibility results were available. The severity of the illness was measured 24 h before culture collection. The data were analyzed using logistic regression (in-hospital mortality) and linear regression (LOS). Overall, there were 167 episodes of P. aeruginosa bacteremia, 123 (86%) of which received appropriate empirical antibiotics. Sixty-one patients died (36.5%). The median time from culture collection to susceptibility results was 3.4 days. After we adjusted for age, severity of illness, and time at risk, we found that the appropriate empirical therapy was not significantly associated with mortality (odds ratio = 0.96; 95% confidence interval = 0.31 to 2.93). There was a 7% reduction in the mean LOS for patients who had received appropriate therapy at the time susceptibility results were available compared to those who did not (P = 0.74). These data suggest that the use of appropriate empirical therapy, i.e., before susceptibility results are known may not be as critical to patient outcomes as other studies have suggested.

Clinical prediction tool to identify patients with Pseudomonas aeruginosa respiratory tract infections at greatest risk for multidrug resistance

Despite the increasing prevalence of multiple-drug-resistant (MDR) Pseudomonas aeruginosa, the factors predictive of MDR have not been extensively explored. We sought to examine factors predictive of MDR among patients with P. aeruginosa respiratory tract infections and to develop a tool to estimate the probability of MDR among such high-risk patients. This was a single-site, case-control study of patients with P. aeruginosa respiratory tract infections. Multiple-drug resistance was defined as resistance to four or more antipseudomonal antimicrobial classes. Clinical data on demographics, antibiotic history, and microbiology were collected. Classification and regression tree analysis (CART) was used to identify the duration of antibiotic exposure associated with MDR P. aeruginosa. Log-binomial regression was used to model the probability of MDR P. aeruginosa. Among 351 P. aeruginosa-infected patients, the proportion of MDR P. aeruginosa was 35%. A significant relationship between prior antibiotic exposure and MDR P. aeruginosa was found for all of the antipseudomonal antibiotics studied, but the duration of prior exposure associated with MDR varied between antibiotic classes; the shortest prior exposure duration was observed for carbapenems and fluoroquinolones, and the longest duration was noted for cefepime and piperacillin-tazobactam. Within the final model, the predicted MDR P. aeruginosa likelihood was most dependent upon length of hospital stay, prior culture sample collection, and number of CART-derived prior antibiotic exposures. A history of a prolonged hospital stay and exposure to antipseudomonal antibiotics predicts multidrug resistance among patients with P. aeruginosa respiratory tract infections at our institution. Identifying these risk factors enabled us to develop a prediction tool to assess the risk of resistance and thus guide empirical antibiotic therapy.

What Infection Control Interventions Should Be Undertaken to Control Multidrug-Resistant Gram-Negative Bacteria?

Multidrug-resistant gram-negative bacteria are an emerging problem. The present article addresses 2 relevant questions: (1) should active surveillance be performed to identify patients colonized with multidrug-resistant gram-negative bacteria, and (2) should contact isolation precautions be taken with patients colonized or infected with multidrug-resistant gram-negative bacteria? Data and variables that are needed to scientifically answer these questions are reviewed, as are existing data on Pseudomonas aeruginosa, Enterobacteriaceae (Escherichia coli and Klebsiella species in particular), and Acinetobacter baumannii.

Comorbidity risk-adjustment measures were developed and validated for studies of antibiotic-resistant infections

OBJECTIVES

Comorbidities are often included in risk-factor models for nosocomial antibiotic-resistant bacterial infections, and aggregate comorbidity measures are valuable because they allow one variable to represent many. This study aimed to develop new aggregate comorbidity measures based upon the Chronic Disease Score (CDS) for assessing the comorbidity-attributable risk of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) nosocomial infections.

STUDY DESIGN AND SETTING

For each outcome, two retrospective cohort studies of hospitalized patients were conducted. Outcomes were a first MRSA or VRE positive clinical culture obtained 48 hours or more postadmission. Each cohort was divided into development (July 1998-2001) and validation (August 2001-2003) samples. New comorbidity measures were created for MRSA (CDS-MRSA), VRE (CDS-VRE), or any nosocomial infection outcome (CDS-ID) using logistic regression and subsequently validated. Model discrimination was measured using the c-statistic.

RESULTS

Discrimination of the CDS-MRSA (c=0.60), CDS-VRE (c=0.65), and CDS-ID (MRSA: c=0.57; VRE: c=0.64) was greater than that of the original CDS (MRSA: c=0.52; VRE: c=0.57).

CONCLUSION

The CDS-MRSA, CDS-VRE, and CDS-ID are new infectious disease specific comorbidity risk-adjustment measures that will be useful for the quality of future epidemiologic studies of MRSA, VRE, and other infectious diseases.

Impact of a computerized clinical decision support system on reducing inappropriate antimicrobial use: a randomized controlled trial

OBJECTIVE

Many hospitals utilize antimicrobial management teams (AMTs) to improve patient care. However, most function with minimal computer support. We evaluated the effectiveness and cost-effectiveness of a computerized clinical decision support system for the management of antimicrobial utilization.

DESIGN

A randomized controlled trial in adult inpatients between May 10 and August 3, 2004. Antimicrobial utilization was managed by an existing AMT using the system in the intervention arm and without the system in the control arm. The system was developed to alert the AMT of potentially inadequate antimicrobial therapy.

MEASUREMENTS

Outcomes assessed were hospital antimicrobial expenditures, mortality, length of hospitalization, and time spent managing antimicrobial utilization.

RESULTS

The AMT intervened on 359 (16%) of 2,237 patients in the intervention arm and 180 (8%) of 2,270 in the control arm, while spending approximately one hour less each day on the intervention arm. Hospital antimicrobial expenditures were $285,812 in the intervention arm and $370,006 in the control arm, for a savings of $84,194 (23%), or $37.64 per patient. No significant difference was observed in mortality (3.26% vs. 2.95%, p = 0.55) or length of hospitalization (3.84 vs. 3.99 days, p = 0.38).

CONCLUSION

Use of the system facilitated the management of antimicrobial utilization by allowing the AMT to intervene on more patients receiving inadequate antimicrobial therapy and to achieve substantial time and cost savings for the hospital. This is the first study that demonstrates in a patient-randomized controlled trial that computerized clinical decision support systems can improve existing antimicrobial management programs.

Population antibiotic susceptibility for Streptococcus pneumoniae and treatment outcomes in common respiratory tract infections

PURPOSE

Antibiotic-resistant Streptococcus pneumoniae potentially threatens the successful treatment of common respiratory tract infections (RTIs); however, the relationship between antibiotic resistance and treatment outcomes remains unclear. We aimed to test the hypothesis that higher in vitro penicillin and erythromycin nonsusceptibility levels among clinical isolates of S. pneumoniae are associated with higher risk of treatment failure in suppurative acute otitis media (AOM), acute sinusitis, and acute exacerbation of chronic bronchitis (AECB).

METHODS

We conducted a population-level analysis using treatment outcomes data from a national, managed-care claims database, and antibiotic susceptibility data from a national repository of antimicrobial susceptibility results between 1997 and 2000. Treatment outcomes in patients with suppurative AOM, acute sinusitis, or AECB receiving selected macrolides or beta-lactams were assessed. Associations between RTI-specific treatment outcomes and antibiotic nonsusceptibility were determined using Spearman correlation coefficients with condition-specific paired outcome and susceptibility data for each region and each year.

RESULTS

There were 649 552 available RTI outcomes and 7252 susceptibility tests performed on S. pneumoniae isolates. There were no statistically significant trends across time for resolution proportions following treatment by either beta-lactams or macrolides among any of the RTIs. Correlation analyses found no statistically significant association between S. pneumoniae susceptibility and RTI treatment outcomes apart from a significant positive association between of erythromycin nonsusceptibility in ear isolates and macrolide treatment resolution for suppurative AOM.

CONCLUSION

On the population level, in vitro S. pneumoniae nonsusceptibility to macrolide or beta-lactam antibiotics was not associated with treatment failure in conditions of probable S. pneumoniae etiology.

Identifying Groups at High Risk for Carriage of Antibiotic-Resistant Bacteria

BACKGROUND

No simple, cost-effective methods exist to identify patients at high risk for methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci colonization outside intensive care settings. Without such methods, colonized patients are entering hospitals undetected and transmitting these bacteria to other patients. We aimed to develop a highly sensitive, simple-to-administer prediction rule to identify subpopulations of patients at high risk for colonization on hospital admission.

METHODS

We conducted a prospective cohort study of adult patients admitted to the general medical and surgical wards of a tertiary-care facility. Data were collected using electronic medical records and an investigator-administered questionnaire. Cultures of anterior nares and the perirectal area were also collected within 48 hours of admission.

RESULTS

Among 699 patients who enrolled in this study, 697 underwent nasal cultures; 555, perirectal cultures; and 553, both. Patient self-report of a hospital admission in the previous year was the most sensitive variable in identifying patients colonized with methicillin-resistant Staphylococcus aureus or with either organism (sensitivity, 76% and 90%, respectively). A prediction rule requiring patients to self-report having received antibiotics and a hospital admission in the previous year would have identified 100% of patients colonized with vancomycin-resistant enterococci. In the high-risk groups defined by the prediction rule, the prevalence of colonization by methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, or either organism were 8.1%, 10.2%, and 15.0%, respectively.

CONCLUSION

Patients with a self-reported previous admission within 1 year may represent a high-risk group for colonization by methicillin-resistant Staphylococcus aureus or vancomycin-resistant enterococci at hospital admission and should be considered for targeted active surveillance culturing.

Methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci co-colonization

High prevalence of co-colonization increases risk for colonization or infection by vancomycin-resistant Staphylococcus aureus.

We assessed the prevalence, risk factors, and clinical outcomes of patients co-colonized with vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) upon admission to the medical and surgical intensive care units (ICUs) of a tertiary-care facility between January 1, 2002, and December 31, 2003. Co-colonization was defined as a VRE-positive perirectal surveillance culture with an MRSA-positive anterior nares surveillance culture collected concurrently. Among 2,440 patients, 65 (2.7%) were co-colonized. Independent risk factors included age (odds ratio [OR] 1.03, 95% confidence interval [CI] 1.01–1.05), admission to the medical ICU (OR 4.38, 95% CI 2.46–7.81), male sex (OR 1.93, 95% CI 1.14–3.30), and receiving antimicrobial drugs on a previous admission within 1 year (OR 3.06, 95% CI 1.85–5.07). None of the co-colonized patients would have been identified with clinical cultures alone. We report a high prevalence of VRE/MRSA co-colonization upon admission to ICUs at a tertiary-care hospital.

The use and interpretation of quasi-experimental studies in medical informatics

Quasi-experimental study designs, often described as nonrandomized, pre-post intervention studies, are common in the medical informatics literature. Yet little has been written about the benefits and limitations of the quasi-experimental approach as applied to informatics studies. This paper outlines a relative hierarchy and nomenclature of quasi-experimental study designs that is applicable to medical informatics intervention studies. In addition, the authors performed a systematic review of two medical informatics journals, the Journal of the American Medical Informatics Association (JAMIA) and the International Journal of Medical Informatics (IJMI), to determine the number of quasi-experimental studies published and how the studies are classified on the above-mentioned relative hierarchy. They hope that future medical informatics studies will implement higher level quasi-experimental study designs that yield more convincing evidence for causal links between medical informatics interventions and outcomes.

Utility of the Chronic Disease Score and Charlson Comorbidity Index as comorbidity measures for use in epidemiologic studies of antibiotic-resistant organisms

Comorbidity is a known risk factor for antibiotic-resistant bacterial infections. Although aggregate comorbidity measures are useful in epidemiologic research, none of the existing measures was developed for use with this outcome. This study compared the utility of two comorbidity measures, the Charlson Comorbidity Index and the Chronic Disease Score, in assessing the comorbidity-attributable risk of nosocomial infections with methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant enterococci (VRE). Two case-control studies were conducted at the University of Maryland Medical System in Baltimore, Maryland. Cases were inpatients with a first positive clinical culture of MRSA or VRE at least 48 hours postadmission (July 1, 1998-July 1, 2001). Three inpatient controls were randomly selected per case. The MRSA study included 2,164 patients, and the VRE study included 1,948. The scores' discrimination and calibration were measured by using the c statistic and Hosmer-Lemeshow chi-square test. The Charlson Comorbidity Index (c = 0.653) and Chronic Disease Score (c = 0.608) were similar discriminators of MRSA and VRE (c = 0.670 and c = 0.647, respectively). Calibration of the scores was poor for both outcomes (p < 0.05). A revised comorbidity measure specific to resistant infections would likely provide a better assessment of the comorbidity-attributable risk of antibiotic-resistant infections.

Prediction rules to identify patients with methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci upon hospital admission

BACKGROUND

In 2003, the Society of Healthcare Epidemiology of America (SHEA) recommended surveillance cultures upon hospital admission for patients at high risk for carriage of vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). The aim of this study was to assess the validity of factors from past medical history in defining patients at high risk for subsequent positive cultures with VRE or MRSA upon hospital admission.

METHODS

Subjects were adult inpatients admitted to nonintensive care wards of the index hospital during 2001-2002. Cases had MRSA or VRE positive clinical cultures within 48 hours of hospital admission. Patients with previous history of MRSA or VRE were excluded.

RESULTS

Nineteen thousand three hundred ninety-nine patients were included, with 273 cases of VRE or MRSA. Previous admission within 1 year of current admission had a sensitivity of 56.8% and a specificity of 88.4% for predicting a case of MRSA or VRE. Individually, the sensitivity and specificity for admission within the past year were 50.5% and 88.4%, respectively, for MRSA and 76.9% and 88.4%, respectively, for VRE.

CONCLUSIONS

Patients with a previous hospital admission represent a high-risk population for positive culture for VRE and MRSA and may be a group of which active surveillance is indicated.

Observations on a consecutive series of patients who have had Trilucent breast implants removed as recommended by the MDA Hazard Notice (May 2000)

A prospective study of 25 female cosmetic-surgery patients who had a total of 50 Trilucent breast implants forms the basis of this paper. All but one patient elected to have new implants, of which all but three patients had silicone implants (the others selected glucose saline implants). The Trilucent implants were more difficult to remove than expected because of a 'Velcro-like' attachment to the internal surface of their capsules. As a result, several implants were ruptured on removal (though none were ruptured on initial exposure). The sites of rupture suggest a structural weakness, possibly related to the microchip panel or folds in the implant shell. Varying degrees of encrustation of the implants and internal capsules were found, which did not appear to be related to the duration of implantation. Histological studies of the capsule changes generally showed lipids and giant cell infiltrations. It would seem that, contrary to expectations, leaking of the filler occurs early and is associated with varying degrees of cellular reactions. The adherence problem appears to be related to the amount and distribution of the leaked material. Only three patients in this series had problems with their Trilucent implants that required additional surgery. One of these remains a significant and unsolved problem.