Clinical and economic burden of invasive pneumococcal disease and noninvasive all-cause pneumonia in hospitalized US adults: A multicenter analysis from 2015 to 2020

OBJECTIVES

To evaluate the clinical and economic outcomes in adults hospitalized with invasive pneumococcal disease (IPD) and noninvasive all-cause pneumonia (ACP) overall and by antimicrobial resistance (AMR) status.

METHODS

Hospitalized adults from the BD Insights Research Database with an ICD10 code for IPD, noninvasive ACP or a positive Streptococcus pneumoniae culture/urine antigen test were included. Descriptive statistics and multivariable analyses were used to evaluate outcomes (in-hospital mortality, length of stay [LOS], cost per admission, and hospital margin [costs - payments]).

RESULTS

The study included 88,182 adult patients at 90 US hospitals (October 2015-February 2020). Most (98.6%) had noninvasive ACP and 40.2% were <65 years old. Of 1450 culture-positive patients, 37.7% had an isolate resistant to ≥1 antibiotic class. Observed mortality, median LOS, cost per admission, and hospital margins were 8.3%, 6 days, $9791, and $11, respectively. Risk factors for mortality included ≥50 years of age, higher risk of pneumococcal disease (based on chronic or immunocompromising conditions), and intensive care unit admission. Patients with IPD had similar mortality rates and hospital margins compared with noninvasive ACP, but greater costs per admission and LOS.

CONCLUSION

IPD and noninvasive ACP are associated with substantial clinical and economic burden across all adult age groups. Expanded pneumococcal vaccination programs may help reduce disease burden and decrease hospital costs.

Treated, hospital-onset Clostridiodes difficile infection: An evaluation of predictors and feasibility of benchmarking comparing 2 risk-adjusted models among 265 hospitals

OBJECTIVES

To evaluate the incidence of a candidate definition of healthcare facility-onset, treated Clostridioides difficile (CD) infection (cHT-CDI) and to identify variables and best model fit of a risk-adjusted cHT-CDI metric using extractable electronic heath data.

METHODS

We analyzed 9,134,276 admissions from 265 hospitals during 2015-2020. The cHT-CDI events were defined based on the first positive laboratory final identification of CD after day 3 of hospitalization, accompanied by use of a CD drug. The generalized linear model method via negative binomial regression was used to identify predictors. Standardized infection ratios (SIRs) were calculated based on 2 risk-adjusted models: a simple model using descriptive variables and a complex model using descriptive variables and CD testing practices. The performance of each model was compared against cHT-CDI unadjusted rates.

RESULTS

The median rate of cHT-CDI events per 100 admissions was 0.134 (interquartile range, 0.023-0.243). Hospital variables associated with cHT-CDI included the following: higher community-onset CDI (CO-CDI) prevalence; highest-quartile length of stay; bed size; percentage of male patients; teaching hospitals; increased CD testing intensity; and CD testing prevalence. The complex model demonstrated better model performance and identified the most influential predictors: hospital-onset testing intensity and prevalence, CO-CDI rate, and community-onset testing intensity (negative correlation). Moreover, 78% of the hospitals ranked in the highest quartile based on raw rate shifted to lower percentiles when we applied the SIR from the complex model.

CONCLUSIONS

Hospital descriptors, aggregate patient characteristics, CO-CDI burden, and clinical testing practices significantly influence incidence of cHT-CDI. Benchmarking a cHT-CDI metric is feasible and should include facility and clinical variables.

Real-world in vitro activity of newer antibiotics against Enterobacterales and Pseudomonas aeruginosa, including carbapenem-non-susceptible and multidrug-resistant isolates: a multicenter analysis

IMPORTANCE

Newer antibiotics against Gram-negative pathogens provide important treatment options, especially for antibiotic-resistant bacteria, but little is known about their use during routine clinical care. To use these agents appropriately, clinicians need to have access to timely susceptibility data. We evaluated 27,531 facility-reported susceptibility results from the BD Insights Research Database to gain a better understanding of real-world testing practices and susceptibility rates for six newer antibiotics. Escherichia coli was the most frequently tested potential pathogen, and ceftazidime-avibactam and ceftolozane-tazobactam had the greatest numbers of susceptibility results. For cefiderocol, eravacycline, imipenem-relabactam, and meropenem-vaborbactam, susceptibility data were available for fewer than 2% of isolates. Susceptibility comparisons should be considered with caution. Ceftazidime-avibactam had the highest susceptibility rates for Enterobacterales while cefiderocol had the highest susceptibility rates for Pseudomonas aeruginosa. New antibiotics have the potential to improve the management of Gram-negative infections, but their use may be hampered by the absence of susceptibility data.

Characteristics, costs, and outcomes associated with central-line-associated bloodstream infection and hospital-onset bacteremia and fungemia in US hospitals

OBJECTIVES

To compare characteristics and outcomes associated with central-line-associated bloodstream infections (CLABSIs) and electronic health record-determined hospital-onset bacteremia and fungemia (HOB) cases in hospitalized US adults.

METHODS

We conducted a retrospective observational study of patients in 41 acute-care hospitals. CLABSI cases were defined as those reported to the National Healthcare Safety Network (NHSN). HOB was defined as a positive blood culture with an eligible bloodstream organism collected during the hospital-onset period (ie, on or after day 4). We evaluated patient characteristics, other positive cultures (urine, respiratory, or skin and soft-tissue), and microorganisms in a cross-sectional analysis cohort. We explored adjusted patient outcomes [length of stay (LOS), hospital cost, and mortality] in a 1:5 case-matched cohort.

RESULTS

The cross-sectional analysis included 403 patients with NHSN-reportable CLABSIs and 1,574 with non-CLABSI HOB. A positive non-bloodstream culture with the same microorganism as in the bloodstream was reported in 9.2% of CLABSI patients and 32.0% of non-CLABSI HOB patients, most commonly urine or respiratory cultures. Coagulase-negative staphylococci and Enterobacteriaceae were the most common microorganisms in CLABSI and non-CLABSI HOB cases, respectively. In case-matched analyses, CLABSIs and non-CLABSI HOB, separately or combined, were associated with significantly longer LOS [difference, 12.1-17.4 days depending on intensive care unit (ICU) status], higher costs (by $25,207-$55,001 per admission), and a >3.5-fold increased risk of mortality in patients with an ICU encounter.

CONCLUSIONS

CLABSI and non-CLABSI HOB cases are associated with significant increases in morbidity, mortality, and cost. Our data may help inform prevention and management of bloodstream infections.

Prevalence of Hospital-Onset Bacteremia Pre- and Post-Implementation of a Needleless Blood Sampling Device From Existing Peripheral Catheters

Repeated access of peripheral intravenous (IV) devices theoretically increases the risk of bacterial exposure. PIVO™ (VelanoVascular) is a needleless, single-use device that enables blood sampling from an existing peripheral IV. The goal of this retrospective observational exploratory study was to evaluate the influence of PIVO use on rates of hospital-onset bacteremia and fungemia (HOB) by comparing HOB rates in the year before and after PIVO introduction in hospitals implementing PIVO and over similar time periods in "control" hospitals with no PIVO. Two hospitals implementing PIVO (Hospital 1, a large community hospital; Hospital 2, a tertiary oncology center), and 71 control hospitals were included. During the 1-year period before and after PIVO introduction, HOB rates decreased in hospitals 1 and 2 by 31.9% and 41.8%, respectively. Control hospitals that did not use PIVO had a 12.4% decrease in HOB rates. Multivariable logistic regression analyses found that PIVO was associated with a lower risk (Hospital 1 odds ratio [OR]: 0.63; 95% CI, 0.42-0.94) or no change (Hospital 2 OR: 1.05; 95% CI, 0.72-1.52) in HOB rates. Control hospitals also showed no change in HOB rates between the 2 time periods. These data do not support concerns about increased risk of bacteremia with PIVO.

Hospital-onset bacteremia: clinical and regulatory ramifications

Tweetable abstract Read the commentary by @Kalvin_Yu_MD and Anuprita Patkar, PhD on the higher risk mortality, LOS and cost of hospital-onset bacteremia (HOB), and the implications of a regulatory HOB quality metric for patient care, clinical workflows and hospital administration #PatientSafety #QualityMetric.

Association of SARS-CoV-2 status and antibiotic-resistant bacteria with inadequate empiric therapy in hospitalized patients: a US multicenter cohort evaluation (July 2019 - October 2021)

BACKGROUND

Antibiotic usage and antibiotic resistance (ABR) patterns changed during the COVID-19 pandemic. Inadequate empiric antibiotic therapy (IET) is a significant public health problem and contributes to ABR. We evaluated factors associated with IET before and during the COVID-19 pandemic to determine the impact of the pandemic on antibiotic management.

METHODS

This multicenter, retrospective cohort analysis included hospitalized US adults who had a positive bacterial culture (specified gram-positive or gram-negative bacteria) from July 2019 to October 2021 in the BD Insights Research Database. IET was defined as antibacterial therapy within 48 h that was not active against the bacteria. ABR results were based on susceptibility testing and reports from local facilities. Multivariate analysis was used to identify risk factors associated with IET in patients with any positive bacterial culture and ABR-positive cultures, including multidrug-resistant (MDR) bacteria.

RESULTS

Of 278,344 eligible patients in 269 hospitals, 56,733 (20.4%) received IET; rates were higher in patients with ABR-positive (n = 93,252) or MDR-positive (n = 39,000) cultures (34.9% and 45.0%, respectively). Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2)-positive patients had significantly higher rates of IET (25.9%) compared with SARS-CoV-2-negative (20.3%) or not tested (19.7%) patients overall and in the ABR and MDR subgroups. Patients with ABR- or MDR-positive cultures had more days of therapy and longer lengths of stay. In multivariate analyses, ABR, MDR, SARS-CoV-2-positive status, respiratory source, and prior admissions were identified as key IET risk factors.

CONCLUSIONS

IET remained a persistent problem during the COVID-19 pandemic and occurred at higher rates in patients with ABR/MDR bacteria or a co-SARS-CoV-2 infection.

Trends in Streptococcus pneumoniae Antimicrobial Resistance in US Children: A Multicenter Evaluation

Background

Antimicrobial resistance (AMR) poses a significant challenge for treating pneumococcal disease. This study assessed AMR trends in Streptococcus pneumoniae from US children.

Methods

We evaluated antibiotic resistance, defined as facility antimicrobial susceptibility reports of intermediate/resistant, in 30-day non-duplicate S. pneumoniae isolates from children (&lt;18 years) with invasive (blood or cerebrospinal fluid/neurological) or non-invasive (respiratory or ear/nose/throat) isolates at 219 US hospital inpatient/outpatient settings in the BD Insights Research Database (January 2011-February 2020). We used descriptive statistics to characterize the percentage of AMR isolates and generalized estimated equations to assess variations in resistance over time.

Results

Of 7,605 S. pneumoniae isolates analyzed, 6,641 (87.3%) were from non-invasive sources. Resistance rates were higher in non-invasive versus invasive isolates. Isolates showed high observed rates of resistance to ≥1 drug class (56.8%), ≥2 drug classes (30.7%), macrolides (39.9%), and penicillin (39.6%) and significant annual increases in resistance to ≥1 drug class (+0.9%), ≥2 drug classes (+1.8%), and macrolides (+5.0%).

Conclusions

Among US children over the last decade, S. pneumoniae isolates showed persistently high rates of resistance to antibiotics and significant increases in ≥1 drug class, ≥2 drug classes, and macrolide resistance rates. Efforts to address AMR in S. pneumoniae may require vaccines targeting resistant serotypes and antimicrobial stewardship efforts.

A multicenter evaluation of antibacterial use in hospitalized patients through the SARS-Cov-2 pandemic waves

BACKGROUND

Excessive use of antibiotics has been reported during the SARS-CoV-2 pandemic. We evaluated trends in antibiotic use and culture positive Gram-negative (GN)/Gram-positive (GP) pathogens in US hospitalized patients before and during the SARS-CoV-2 pandemic.

METHODS

This multicenter, retrospective study included patients from 271 US facilities with > 1-day inpatient admission with discharge or death between July 1, 2019, and October 30, 2021, in the BD Insights Research Database. We evaluated microbiological testing data, antibacterial use, defined as antibacterial use ≥ 24 h in admitted patients, and duration of antibacterial therapy.

RESULTS

Of 5,518,744 patients included in the analysis, 3,729,295 (67.6%) patients were hospitalized during the pandemic with 2,087,774 (56.0%) tested for SARS-CoV-2 and 189,115 (9.1%) testing positive for SARS-CoV-2. During the pre-pandemic period, 36.2% were prescribed antibacterial therapy and 9.3% tested positive for select GN/GP pathogens. During the SARS-CoV-2 pandemic, antibacterial therapy (57.8%) and positive GN/GP culture (11.9%) were highest in SARS-CoV-2-positive patients followed by SARS-CoV-2-negative patients (antibacterial therapy, 40.1%; GN/GP, pathogens 11.0%), and SARS-CoV-2 not tested (antibacterial therapy 30.4%; GN/GP pathogens 7.2%). Multivariate results showed significant decreases in antibacterial therapy and positive GN/GP cultures for both SARS-CoV-2-positive and negative patients during the pandemic, but no significant overall changes from the pre-pandemic period to the pandemic period.

CONCLUSIONS

There was a decline in both antibacterial use and positive GN/GP pathogens in patients testing positive for SARS-CoV-2. However, overall antibiotic use was similar prior to and during the pandemic. These data may inform future efforts to optimize antimicrobial stewardship and prescribing.

Older patient age and prior antimicrobial use strongly predict antimicrobial resistance in Escherichia coli isolates recovered from urinary tract infections among female outpatients

BACKGROUND

Increasing prevalence of antimicrobial resistance (AMR), including multidrug resistance (MDR), among Escherichia coli (E. coli) makes treatment of uncomplicated urinary tract infection (uUTI) difficult. We assessed risk factors for fluoroquinolone (FQ)-not-susceptible (NS) and MDR E. coli among US female outpatients.

METHODS

This retrospective cohort study utilized data from female outpatients aged ≥ 12 years with E. coli positive urine culture and oral antimicrobial prescription ± 1 day from index. We assessed patient-level factors within 90 and 91-360 days prior to index as predictors of FQ NS (intermediate/resistant) and MDR (NS to ≥ 1 drug across ≥ 3 classes) E. coli: age, prior oral antimicrobial dispensing, prior AMR phenotypes, prior urine culture, and prior hospitalization.

RESULTS

Among 1,858 outpatients with urine-isolated E. coli, 369 (19.9%) had FQ NS and 59 (3.2%) had MDR isolates. After multivariable adjustment, independent risk factors (p < 0.03) for FQ NS E. coli were older age, prior FQ NS isolates, prior dispensing of FQ, and dispensing of any oral antibiotic. Independent risk factors (p < 0.02) for MDR were prior extended-spectrum β-lactamase-producing isolates (ESBL+), prior FQ dispensing, and prior oral antibiotic dispensing.

CONCLUSIONS

In women with uUTI due to E. coli, prior dispensing of FQ or any oral antibiotic within 90 days predicted FQ NS and MDR urine E. coli. Prior urine culture with FQ NS isolates and older age were predictive of FQ NS E. coli. Prior ESBL+ was predictive of MDR E. coli. These data could help identify patients at risk for AMR E. coli and inform empiric prescribing.

Epidemiology and outcomes of culture-positive bloodstream pathogens prior to and during the SARS-CoV-2 pandemic: a multicenter evaluation

Background

Bloodstream infections (BSIs) are an important cause of morbidity and mortality in hospitalized patients. We evaluate incidence of community- and hospital-onset BSI rates and outcomes before and during the SARS-CoV-2 pandemic.

Methods

We conducted a retrospective cohort study evaluating patients who were hospitalized for ≥ 1 day with discharge or death between June 1, 2019, and September 4, 2021, across 271 US health care facilities. Community- and hospital-onset BSI and related outcomes before and during the SARS-CoV-2 pandemic, including intensive care admission rates, and overall and ICU-specific length of stay (LOS) was evaluated. Bivariate correlations were calculated between the pre-pandemic and pandemic periods overall and by SARS-CoV-2 testing status.

Results

Of 5,239,692 patient admissions, there were 20,113 community-onset BSIs before the pandemic (11.2/1000 admissions) and 39,740 (11.5/1000 admissions) during the pandemic (P ≤ 0.0062). Corresponding rates of hospital-onset BSI were 2,771 (1.6/1000 admissions) and 6,864 (2.0/1000 admissions; P < 0.0062). Compared to the pre-pandemic period, rates of community-onset BSI were higher in patients who tested negative for SARS-CoV-2 (15.8/1000 admissions), compared with 9.6/1000 BSI admissions among SARS-CoV-2-positive patients. Compared with patients in the pre-pandemic period, SARS-CoV-2-positive patients with community-onset BSI experienced greater ICU admission rates (36.6% vs 32.8%; P < 0.01), greater ventilator use (10.7% vs 4.7%; P < 0.001), and longer LOS (12.2 d vs 9.1 d; P < 0.001). Rates of hospital-onset BSI were higher in the pandemic vs the pre-pandemic period (2.0 vs 1.5/1000; P < 0.001), with rates as high a 7.3/1000 admissions among SARS-CoV-2-positive patients. Compared to the pre-pandemic period, SARS-CoV-2-positive patients with hospital-onset BSI had higher rates of ICU admission (72.9% vs 55.4%; P < 0.001), LOS (34.8 d vs 25.5 d; P < 0.001), and ventilator use (52.9% vs 21.5%; P < 0.001). Enterococcus species, Staphylococcus aureus, Klebsiella pneumoniae, and Candida albicans were more frequently detected in the pandemic period.

Conclusions and relevance

This nationally representative study found an increased risk of both community-onset and hospital-onset BSI during the SARS-CoV-2 pandemic period, with the largest increased risk in hospital-onset BSI among SARS-CoV-2-positive patients. SARS-CoV-2 positivity was associated with worse outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07810-8.

A multicenter comparison of prevalence and predictors of antimicrobial resistance in hospitalized patients before and during the SARS-CoV-2 pandemic

Background

Antibacterial therapy is frequently used in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) without evidence of bacterial infection, prompting concerns about increased antimicrobial resistance (AMR). We evaluated trends in AMR before and during the SARS-CoV-2 pandemic.

Methods

This multicenter, retrospective cohort analysis included hospitalized adults aged ≥18 years with >1-day inpatient admission and a record of discharge or death from 271 US facilities in the BD Insights Research Database. We evaluated rates of AMR events, defined as positive cultures for select Gram-negative and Gram-positive pathogens from any source with nonsusceptibility reported by commercial panels before (7/1/19-2/29/20) and during (3/1/20-10/30/21) the SARS-CoV-2 pandemic.

Results

Of 5,518,666 admissions evaluated, AMR rates per 1000 admissions were 35.4 for the pre-pandemic period and 34.7 for the pandemic period (P ≤ 0.0001). In the pandemic period, AMR rates per 1000 admissions were 49.2 for SARS-CoV-2-positive admissions, 41.1 for SARS-CoV-2-negative admissions, and 25.7 for patients untested (P ≤ 0.0001). AMR rates per 1000 admissions among community-onset (CO) infections during the pandemic were lower versus pre-pandemic levels (26.1 vs 27.6; P < 0.0001), while AMR rates for hospital-onset (HO) infections were higher (8.6 vs 7.7; P < 0.0001), driven largely by SARS-Cov-2-positive admissions (21.8). AMR rates were associated with overall antimicrobial use, rates of positive cultures, and higher use of inadequate empiric therapy.

Conclusions

Although overall AMR rates did not substantially increase from pre-pandemic levels, patients tested for SARS-CoV-2 infection had a significantly higher rate of AMR and HO infections. Antimicrobial and diagnostic stewardship is key to identifying this high-risk AMR population.

A Multicenter Evaluation of Trends in Antimicrobial Resistance among Streptococcus pneumoniae Isolates from Adults in the United States

Background

Management of pneumococcal disease is complicated by high rates of antimicrobial resistance (AMR). This study assessed AMR trends for Streptococcus pneumoniae isolates from adults with pneumococcal disease.

Methods

From January 2011 to February 2020, we evaluated 30-day nonduplicate S. pneumoniae isolates from 290 US hospitals (BD Insights Research Database) from adults (≥18 years) in inpatient and outpatient settings. Isolates were required to have ≥1 AMR result for invasive (blood, cerebrospinal fluid/neurologic) or noninvasive (respiratory or ear/nose/throat) pneumococcal disease samples. Determination of AMR was based on facility reports of intermediate or resistant. Descriptive statistics and generalized estimated equations were used to assess variations over time.

Results

Over the study period, 34 039 S. pneumoniae isolates were analyzed (20 749 [61%] from noninvasive sources and 13 290 [39%] from invasive sources). Almost half (46.6%) of the isolates were resistant to ≥1 drug, and noninvasive isolates had higher rates of AMR than invasive isolates. Total S. pneumoniae isolates had high rates of resistance to macrolides (37.7%), penicillin (22.1%), and tetracyclines (16.1%). Multivariate modeling identified a significant increasing trend in resistance to macrolides (+1.8%/year; P < .001). Significant decreasing trends were observed for penicillin (−1.6%/year; P < .001), extended-spectrum cephalosporins (ESCs; −0.35%/year; P < .001), and ≥3 drugs (−0.5%/year; P < .001).

Conclusions

Despite decreasing trends for penicillin, ESCs, and resistance to ≥3 drugs, AMR rates are persistently high in S. pneumoniae isolates among US adults. Increasing macrolide resistance suggests that efforts to address AMR in S. pneumoniae may require antimicrobial stewardship efforts and higher-valent pneumococcal conjugate vaccines.

A multicenter analysis of inpatient antibiotic use during the 2015-2019 influenza seasons in the United States: Untapped opportunities for antimicrobial stewardship

Outpatient antibiotic use increases during winter months, but information on temporal changes in inpatient antibiotic use in US hospitals is limited. The use of certain inpatient antibiotics, including extended-spectrum cephalosporins, macrolides, and tetracyclines, was strongly associated with influenza activity during the 2015-2019 viral respiratory seasons.

A Multicenter Comparison of Carbapenem-Nonsusceptible Enterobacterales and Pseudomonas aeruginosa Rates in the US (2016 to 2020): Facility-Reported Rates versus Rates Based on Updated Clinical Laboratory and Standards Institute Breakpoints

Adoption of revised antimicrobial susceptibility breakpoints is often slow, potentially leading to underreporting of antimicrobial resistance. We compared facility-reported rates of carbapenem nonsusceptibility (NS; intermediate or resistant) with NS rates based on current Clinical and Laboratory Standards Institute (CLSI) breakpoints for Enterobacterales or Pseudomonas aeruginosa isolates in ambulatory and inpatient adults in the BD Insights Research Database (US) from 2016 to 2020. Overall, 77.4% (937,926/1,211,845) and 90.6% (2,157,785/2,381,824) of nonduplicate Enterobacterales isolates with facility-reported susceptibility results had MIC data for ertapenem (ETP) and imipenem/meropenem/doripenem (IPM/MEM/DOR), respectively; 86.9% (255,844/294,426) of P. aeruginosa isolates had MIC data for IPM/MEM/DOR. Facility-reported susceptibility and susceptibility based on CLSI criteria resulted in comparable carbapenem susceptibility rates (99.3% versus 99.1% for ETP-susceptible Enterobacterales, 98.9% versus 98.4% for IPM/MEM/DOR-susceptible Enterobacterales, and 84.9% versus 83.3% for IPM/MEM/DOR-susceptible P. aeruginosa). However, compared with CLSI criteria, facilities underreported Enterobacterales- and IPM/MEM/DOR-NS isolates by 18.8% and 26.5%, respectively, and P. aeruginosa IPM/MEM/DOR-NS isolates by 9.8%. Underreporting was observed for both intermediate and resistant isolates. Our data suggest that delayed adoption of revised breakpoints has a small but potentially important impact on reported rates of antimicrobial resistance. Facilities should be aware of local epidemiology, evaluate potential underreporting of resistance, and assess the related clinical impact. IMPORTANCE Clinicians often base antimicrobial therapeutic decisions on laboratory determinations of pathogen susceptibility to an antibiotic based on MIC breakpoints. MIC breakpoints evolve over time based on new information; between 2010 and 2012 the CLSI lowered carbapenem breakpoints for Enterobacterales and Pseudomonas aeruginosa, and these were subsequently adopted by the US Food and Drug Administration. Carbapenems are important therapeutic options for these difficult-to-treat pathogens, so understanding resistance rates is critically important. However, laboratories can be slow to adopt updated breakpoints. We used MIC data to evaluate whether reports received by hospitals for carbapenem susceptibility were consistent with updated CLSI breakpoints. Although overall susceptibility rates were similar between hospital reports and susceptibility based on updated CLSI criteria, the percentages of carbapenem-resistant isolates were significantly underreported by hospital reports. Delayed adoption of MIC breakpoints may impact epidemiological understanding of resistance and contribute to the spread of resistant pathogens.

Regional Differences in Antibiotic-resistant Enterobacterales Urine Isolates in the United States: 2018-2020

Antimicrobial resistance (AMR) can complicate effective management of urinary tract infections. We conducted a retrospective study of AMR in Enterobacterales urine isolates from ambulatory and hospitalized adult patients from 2018-2020 (BD Insights Research Database) to evaluate regional differences in isolates with an extended-spectrum beta-lactamase-producing phenotype and those not susceptible to beta-lactams, fluoroquinolone (FQ), nitrofurantoin (NFT), trimethoprim/sulfamethoxazole (TMP/SMX), or multiple antibiotic classes (≥ 2 or ≥ 3). Our analyses included 349,741 Enterobacterales urine isolates from 321 inpatient facilities and 980,354 isolates from 338 ambulatory care facilities. In multivariable analyses, the highest rate of resistance was to beta-lactams (60.8% and 55.8% for inpatient and ambulatory settings, respectively), followed by FQ (27.5%), NFT (27.0%), and TMP/SMX (25.4%) for inpatients and by TMP/SMX (22.4%), FQ (21.6%), and NFT (21.6%) for ambulatory patients. Isolates with an extended-spectrum beta-lactamase-producing phenotype (13.2% and 8.6% for inpatient and ambulatory settings, respectively) and multidrug resistance (inpatient and ambulatory rates of 23.4% and 17.7% for ≥ 2 drugs; 9.9% and 6.4% for ≥ 3 drugs) were also prevalent. Statistically significant differences by geographic region (P ≤ 0.005) were observed for AMR classes in both inpatient and ambulatory settings, but the rates remained above the thresholds recommended for empiric urinary tract infection therapy across most regions.

A multicenter analysis of trends in resistance in urinary Enterobacterales isolates from ambulatory patients in the United States: 2011-2020

Background

Urinary tract infections (UTIs), which are usually caused by bacteria in the Enterobacterales family, are a common reason for outpatient visits. Appropriate empiric therapy for UTIs requires an understanding of antibiotic resistance in the community. In this nationwide study, we examined trends in antibiotic resistance in urinary Enterobacterales isolates from ambulatory patients in the United States (US).

Methods

We analyzed the antimicrobial susceptibility profiles (extended-spectrum beta-lactamase [ESBL]-producing phenotype and not susceptible [NS] to beta-lactams, trimethoprim/sulfamethoxazole [TMP/SMX], fluoroquinolones [FQ], or nitrofurantoin [NFT]) of 30-day non-duplicate Enterobacterales isolates from urine cultures tested at ambulatory centers in the BD Insights Research Database (2011–2020). The outcome of interest was the percentage of resistant isolates by pathogen and year. Multi-variable generalized estimating equation models were used to assess trends in resistance over time and by additional covariates.

Results

A total of 338 US facilities provided data for > 2.2 million urinary Enterobacterales isolates during the 10-year study. Almost three-quarters (72.8%) of Enterobacterales isolates were Escherichia coli. Overall unadjusted resistance rates in Enterobacterales isolates were 57.5%, 23.1%, 20.6%, and 20.2% for beta-lactams, TMP/SMX, FQ, and NFT, respectively, and 6.9% had an ESBL-producing phenotype. Resistance to two or more antibiotic classes occurred in 16.4% of isolates and 5.5% were resistant to three or more classes. Among isolates with an ESBL-producing phenotype, 70.1%, 59.9%, and 33.5% were NS to FQ, TMP/SMX, and NFT, respectively. In multivariable models, ESBL-producing and NFT NS Enterobacterales isolates increased significantly (both P < 0.001), while other categories of resistance decreased. High rates (≥ 50%) of beta-lactam and NFT resistance were observed in Klebsiella isolates and in non-E. coli, non-Klebsiella Enterobacterales isolates.

Conclusions

Antimicrobial resistance was common in urinary Enterobacterales isolates. Isolates with an ESBL-producing phenotype increased by about 30% between 2011 and 2020, and significant increases were also observed in NFT NS Enterobacterales isolates. Resistance rates for all four antibiotic classes were higher than thresholds recommended for use as empiric therapy. Non-E. coli Enterobacterales isolates showed high levels of resistance to commonly used empiric antibiotics, including NFT. These data may help inform empiric therapy choices for outpatients with UTIs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07167-y.

Global burden of bacterial antimicrobial resistance in 2019: a systematic analysis

BACKGROUND

Antimicrobial resistance (AMR) poses a major threat to human health around the world. Previous publications have estimated the effect of AMR on incidence, deaths, hospital length of stay, and health-care costs for specific pathogen-drug combinations in select locations. To our knowledge, this study presents the most comprehensive estimates of AMR burden to date.

METHODS

We estimated deaths and disability-adjusted life-years (DALYs) attributable to and associated with bacterial AMR for 23 pathogens and 88 pathogen-drug combinations in 204 countries and territories in 2019. We obtained data from systematic literature reviews, hospital systems, surveillance systems, and other sources, covering 471 million individual records or isolates and 7585 study-location-years. We used predictive statistical modelling to produce estimates of AMR burden for all locations, including for locations with no data. Our approach can be divided into five broad components: number of deaths where infection played a role, proportion of infectious deaths attributable to a given infectious syndrome, proportion of infectious syndrome deaths attributable to a given pathogen, the percentage of a given pathogen resistant to an antibiotic of interest, and the excess risk of death or duration of an infection associated with this resistance. Using these components, we estimated disease burden based on two counterfactuals: deaths attributable to AMR (based on an alternative scenario in which all drug-resistant infections were replaced by drug-susceptible infections), and deaths associated with AMR (based on an alternative scenario in which all drug-resistant infections were replaced by no infection). We generated 95% uncertainty intervals (UIs) for final estimates as the 25th and 975th ordered values across 1000 posterior draws, and models were cross-validated for out-of-sample predictive validity. We present final estimates aggregated to the global and regional level.

FINDINGS

On the basis of our predictive statistical models, there were an estimated 4·95 million (3·62-6·57) deaths associated with bacterial AMR in 2019, including 1·27 million (95% UI 0·911-1·71) deaths attributable to bacterial AMR. At the regional level, we estimated the all-age death rate attributable to resistance to be highest in western sub-Saharan Africa, at 27·3 deaths per 100 000 (20·9-35·3), and lowest in Australasia, at 6·5 deaths (4·3-9·4) per 100 000. Lower respiratory infections accounted for more than 1·5 million deaths associated with resistance in 2019, making it the most burdensome infectious syndrome. The six leading pathogens for deaths associated with resistance (Escherichia coli, followed by Staphylococcus aureus, Klebsiella pneumoniae, Streptococcus pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa) were responsible for 929 000 (660 000-1 270 000) deaths attributable to AMR and 3·57 million (2·62-4·78) deaths associated with AMR in 2019. One pathogen-drug combination, meticillin-resistant S aureus, caused more than 100 000 deaths attributable to AMR in 2019, while six more each caused 50 000-100 000 deaths: multidrug-resistant excluding extensively drug-resistant tuberculosis, third-generation cephalosporin-resistant E coli, carbapenem-resistant A baumannii, fluoroquinolone-resistant E coli, carbapenem-resistant K pneumoniae, and third-generation cephalosporin-resistant K pneumoniae.

INTERPRETATION

To our knowledge, this study provides the first comprehensive assessment of the global burden of AMR, as well as an evaluation of the availability of data. AMR is a leading cause of death around the world, with the highest burdens in low-resource settings. Understanding the burden of AMR and the leading pathogen-drug combinations contributing to it is crucial to making informed and location-specific policy decisions, particularly about infection prevention and control programmes, access to essential antibiotics, and research and development of new vaccines and antibiotics. There are serious data gaps in many low-income settings, emphasising the need to expand microbiology laboratory capacity and data collection systems to improve our understanding of this important human health threat.

FUNDING

Bill & Melinda Gates Foundation, Wellcome Trust, and Department of Health and Social Care using UK aid funding managed by the Fleming Fund.

Antibiotic Resistance Patterns and Association with the Influenza Season in the United States: A Multicenter Evaluation Reveals Surprising Associations Between Influenza Season and Resistance in Gram-negative Pathogens

Background

Viral infections are often treated with empiric antibiotics due to suspected bacterial coinfections, leading to antibiotic overuse. We aimed to describe antibiotic resistance (ABR) trends and their association with the influenza season in ambulatory and inpatient settings in the United States.

Methods

We used the BD Insights Research Database to evaluate antibiotic susceptibility profiles in 30-day nonduplicate bacterial isolates collected from patients >17 years old at 257 US healthcare institutions from 2011 to 2019. We investigated ABR in Gram-positive (Staphylococcus aureus and Streptococcus pneumoniae) and Gram-negative (Enterobacterales [ENT], Pseudomonas aeruginosa [PSA], and Acinetobacter baumannii spp [ACB]) bacteria expressed as the proportion of isolates not susceptible ([NS], intermediate or resistant) and resistance per 100 admissions (inpatients only). Antibiotics included carbapenems (Carb), fluoroquinolones (FQ), macrolides, penicillin, extended-spectrum cephalosporins (ESC), and methicillin. Generalized estimating equations models were used to evaluate monthly trends in ABR outcomes and associations with community influenza rates.

Results

We identified 8 250 860 nonduplicate pathogens, including 154 841 Gram-negative Carb-NS, 1 502 796 Gram-negative FQ-NS, 498 012 methicillin-resistant S aureus (MRSA), and 44 131 NS S pneumoniae. All S pneumoniae rates per 100 admissions (macrolide-, penicillin-, and ESC-NS) were associated with influenza rates. Respiratory, but not nonrespiratory, MRSA was also associated with influenza. For Gram-negative pathogens, influenza rates were associated with the percentage of FQ-NS ENT, FQ-NS PSA, and Carb-NS ACB.

Conclusions

Our study showed expected increases in rates of ABR Gram-positive and identified small but surprising increases in ABR Gram-negative pathogens associated with influenza activity. These insights may help inform antimicrobial stewardship initiatives.

The impact of infections on reimbursement in 92 US hospitals, 2015-2018

BACKGROUND

The diagnosis-related group (DRG) is a payment system introduced to standardize healthcare costs. However, reimbursement for treatment of infections does not always cover costs.

METHODS

We used 2015-2018 data from 92 US hospitals in the Becton Dickinson Insights Research Database to compare the financial burden of hospital admissions within non-infection DRGs for patients with a bacterial infection (INF+) versus those without an infection (INF-). Included patients were adults with a hospital length of stay (LOS) ≥3 days and evidence of infection. Multi-variable adjusted analyses via generalized linear mixed models were used to evaluate the impact of an infection on outcomes.

RESULTS

We analyzed data from 133,423 INF+ admissions and 170,531 INF- admissions. Infections were associated with an approximately two-fold increase in model-estimated LOS (9.2 vs 4.8 d; P < .001) and intensive care unit LOS (5.1 vs 2.8 d; P < .001). The average additional hospital cost for INF+ versus INF- admissions was $10,326 per admission (P < .001) and the average loss after reimbursement was $1,067 (P = .006). Only private insurance payers had a positive margin.

CONCLUSIONS

Current reimbursement options for infections result in significant hospital financial burden. Reimbursement models should be reconsidered to enable adoption of costlier diagnostics and antimicrobials.

Relationships between creatinine increase and mortality rates in patients given vancomycin in 76 hospitals: The increasing role of infectious disease pharmacists

PURPOSE

Vancomycin is a commonly used antimicrobial with the potential for renal toxicity. We evaluated vancomycin duration, changes in renal function after vancomycin initiation ("post-vancomycin" renal function changes), and associated mortality risk among hospitalized patients.

METHODS

We analyzed data from 76 hospitals and excluded patients with a baseline serum creatinine concentration (SCr) of >3.35 mg/dL. We estimated mortality risk relative to vancomycin duration and the magnitude of post-vancomycin SCr change, controlling for demographics, baseline SCr, underlying diseases, clinical acuity, and comorbidities.

RESULTS

Among 128,993 adult inpatients treated with vancomycin, 49.0% did not experience SCr elevation. Among the remaining patients, 26.0%, 11.4%, 8.8% and 4.8% experienced increases in post-vancomycin SCr of 1% to 20%, 21% to 40%, 41% to 100%, and greater than 100%, respectively. Compared to mortality risk among patients with a vancomycin therapy duration between 4 and 5 days (the lowest-mortality group), longer vancomycin therapy duration was not independently associated with higher mortality risk after adjusting for confounders. In contrast, there was a graded relationship between post-vancomycin SCr elevation and mortality. Multivariable adjusted mortality odds ratios ranged from 1.60 to 13.66, corresponding to SCr increases of 10% and greater than 200%, respectively.

CONCLUSION

Half of patients given vancomycin did not experience SCr elevation and had the lowest mortality, suggesting that vancomycin can be used safely if renal function is stabilized. In the large study cohort, vancomycin duration itself was not an independent predictor of mortality. Post-vancomycin SCr elevation appeared to be a driver of in-hospital mortality. Even a 10% SCr increase from baseline prior to vancomycin infusion was associated with increased mortality risk. This finding stresses the importance of closely monitoring renal function and may support the value of pharmacokinetic dosing.

Effect of Inadequate Empiric Antibacterial Therapy on Hospital Outcomes in SARS-CoV-2-Positive and -Negative US Patients With a Positive Bacterial Culture: A Multicenter Evaluation From March to November 2020

Background

Increased utilization of antimicrobial therapy has been observed during the coronavirus disease 2019 pandemic. We evaluated hospital outcomes based on the adequacy of antibacterial therapy for bacterial pathogens in US patients.

Methods

This multicenter retrospective study included patients with ≥24 hours of inpatient admission, ≥24 hours of antibiotic therapy, and discharge/death from March to November 2020 at 201 US hospitals in the BD Insights Research Database. Included patients had a test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and a positive bacterial culture (gram-positive or gram-negative). We used generalized linear mixed models to evaluate the impact of inadequate empiric therapy (IET), defined as therapy not active against the identified bacteria or no antimicrobial therapy in the 48 hours following culture, on in-hospital mortality and hospital and intensive care unit length of stay (LOS).

Results

Of 438 888 SARS-CoV-2-tested patients, 39 203 (8.9%) had positive bacterial cultures. Among patients with positive cultures, 9.4% were SARS-CoV-2 positive, 74.4% had a gram-negative pathogen, 25.6% had a gram-positive pathogen, and 44.1% received IET for the bacterial infection. The odds of mortality were 21% higher for IET (odds ratio [OR], 1.21; 95% CI, 1.10–1.33; P < .001) compared with adequate empiric therapy. IET was also associated with increased hospital LOS (LOS, 16.1 days; 95% CI, 15.5–16.7 days; vs LOS, 14.5 days; 95% CI, 13.9–15.1 days; P < .001). Both mortality and hospital LOS findings remained consistent for SARS-CoV-2-positive and -negative patients.

Conclusions

Bacterial pathogens continue to play an important role in hospital outcomes during the pandemic. Adequate and timely therapeutic management may help ensure better outcomes.

A multicenter analysis of the clinical microbiology and antimicrobial usage in hospitalized patients in the US with or without COVID-19

BACKGROUND

Past respiratory viral epidemics suggest that bacterial infections impact clinical outcomes. There is minimal information on potential co-pathogens in patients with coronavirus disease-2019 (COVID-19) in the US. We analyzed pathogens, antimicrobial use, and healthcare utilization in hospitalized US patients with and without severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2).

METHODS

This multicenter retrospective study included patients with > 1 day of inpatient admission and discharge/death between March 1 and May 31, 2020 at 241 US acute care hospitals in the BD Insights Research Database. We assessed microbiological testing data, antimicrobial utilization in admitted patients with ≥24 h of antimicrobial therapy, and length of stay (LOS).

RESULTS

A total of 141,621 patients were tested for SARS-CoV-2 (17,003 [12.0%] positive) and 449,339 patients were not tested. Most (> 90%) patients tested for SARS-CoV-2 had additional microbiologic testing performed compared with 41.9% of SARS-CoV-2-untested patients. Non-SARS-CoV-2 pathogen rates were 20.9% for SARS-CoV-2-positive patients compared with 21.3 and 27.9% for SARS-CoV-2-negative and -untested patients, respectively. Gram-negative bacteria were the most common pathogens (45.5, 44.1, and 43.5% for SARS-CoV-2-positive, -negative, and -untested patients). SARS-CoV-2-positive patients had higher rates of hospital-onset (versus admission-onset) non-SARS-CoV-2 pathogens compared with SARS-CoV-2-negative or -untested patients (42.4, 22.2, and 19.5%, respectively), more antimicrobial usage (68.0, 45.2, and 25.1% of patients), and longer hospital LOS (mean [standard deviation (SD)] of 8.6 [11.4], 5.1 [8.9], and 4.2 [8.0] days) and intensive care unit (ICU) LOS (mean [SD] of 7.8 [8.5], 3.6 [6.2], and 3.6 [5.9] days). For all groups, the presence of a non-SARS-CoV-2 pathogen was associated with increased hospital LOS (mean [SD] days for patients with versus without a non-SARS-CoV-2 pathogen: 13.7 [15.7] vs 7.3 [9.6] days for SARS-CoV-2-positive patients, 8.2 [11.5] vs 4.3 [7.9] days for SARS-CoV-2-negative patients, and 7.1 [11.0] vs 3.9 [7.4] days for SARS-CoV-2-untested patients).

CONCLUSIONS

Despite similar rates of non-SARS-CoV-2 pathogens in SARS-CoV-2-positive, -negative, and -untested patients, SARS-CoV-2 was associated with higher rates of hospital-onset infections, greater antimicrobial usage, and extended hospital and ICU LOS. This finding highlights the heavy burden of the COVID-19 pandemic on healthcare systems and suggests possible opportunities for diagnostic and antimicrobial stewardship.

A Multicenter Evaluation of the US Prevalence and Regional Variation in Macrolide-Resistant S. pneumoniae in Ambulatory and Hospitalized Adult Patients in the United States

Macrolide resistance was found in 39.5% of 3626 nonduplicate Streptococcus pneumoniae isolates from adult ambulatory and inpatient settings at 329 US hospitals (2018–2019). Macrolide resistance was significantly higher for respiratory vs blood isolates and ambulatory vs inpatient settings. Despite geographic variation, S. pneumoniae macrolide resistance was >25% in most regions.

Predicting hospital readmission in patients with mental or substance use disorders: A machine learning approach

OBJECTIVE

Mental or substance use disorders (M/SUD) are major contributors of disease burden with high risk for hospital readmissions. We sought to develop and evaluate a readmission model using a machine learning (ML) approach.

METHODS

We analyzed patients with continuous enrollment for three years and at least one episode of M/SUD as the primary reason for hospital admission. The outcome was readmission within 30-days from discharge. Model performance was evaluated using the Area under the Receiver Operating Characteristic (AUROC). We compared the AUROCs of an extreme gradient boosted tree (XGBoost) model to generalized linear model with elastic net regularization (GLMNet).

RESULTS

We analyzed 65,426 unique patients and 97,688 admissions. Patients with mental disorders accounted for 66 % (13.2 % readmission rate) and substance use disorders, 34 % (22.3 % readmission rate). Among all those who had readmissions, 70.7 %, 17.0 %, and 12.4 % had 1, 2, or 3+ readmissions, respectively. Previous hospitalizations, hospital utilization, discharge disposition, diagnosis category, and comorbidity were among the highest important features in the XGBoost model. The XGBoost model AUROC was 0.737 (95 % CI: 0.732 to 0.742) versus the GLMNet 0.697 (95 % CI: 0.690 to 0.703). The AUROC of the final XGBoost model on the testing set was 0.738 (95 % CI: 0.730 to 0.748), higher than published readmission models for mental health patients.

CONCLUSIONS

The XGBoost model has a better performance than GLMNet and previously published models in predicting readmissions in mental health patients. Our model may be further tested to aid targeted demographic initiatives to reduce M/SUDs readmissions and benchmarking.

Benchmarking Inpatient Antimicrobial Use: A Comparison of Risk-Adjusted Observed-to-Expected Ratios

Background

Increasing antibiotic resistance has made benchmarking appropriate inpatient antibiotic use a worldwide priority supported by expert societies and regulatory bodies; however, standard risk adjustment for fair interfacility comparison has been elusive. We describe a risk-adjusted antibiotic exposure ratio that may help facilitate assessment of antimicrobial use.

Methods

This was a retrospective cohort study of 2.7 million admissions evaluating a wide array of potential explanatory variables for correlation with expected antibiotic consumption in a 2-step approach using recursive partitioning and Poisson regression. Observed-to-expected ratios of risk-adjusted antibiotic use were calculated. Three models of varying complexity were compared: (1) a complex ratio consisting of all available antibiotic use risk factors in a hierarchical model; (2) a simplified antimicrobial stewardship program (ASP) ratio using common facility and encounter factors in a single-level model; and (3) a facility ratio using only broad hospital characteristics.

Results

Diagnosis-related groups, infection present on admission, patient class, and unit type were the major predictors of expected antibiotic use. Aside from a history of gram-positive resistance in the prior 12 months for anti-methicillin-resistant Staphylococcus aureus drugs, additional clinical and comorbid history information did not improve the model. The simplified ASP ratio demonstrated higher Pearson correlation (R2 = 0.97-0.99) to the complex ratio than the facility ratio (R2 = 0.57-0.85) and provided clinical explanations when discordant.

Conclusions

The simplified ASP ratio is derived from a parsimonious model that incorporates disease burden through patient-level risk adjustment and better informs stewardship assessment. This may allow for improved comparison of antibiotic use between healthcare facilities.

Testing for Coccidioidomycosis among Community-Acquired Pneumonia Patients, Southern California, USA1

We conducted a cohort study to identify characteristics associated with testing for, and testing positive for, coccidioidomycosis among patients with community-acquired pneumonia in southern California, USA. Limited and delayed testing probably leads to underdiagnosis among non-Hispanic black, Filipino, or Hispanic patients and among high-risk groups, including persons in whom antimicrobial drug therapy has failed.

Antibiotic Stewardship in Small Hospitals: Barriers and Potential Solutions

Antibiotic stewardship programs (ASPs) improve antibiotic prescribing. Seventy-three percent of US hospitals have <200 beds. Small hospitals (<200 beds) have similar rates of antibiotic prescribing compared to large hospitals, but the majority of small hospitals lack ASPs that satisfy the Centers for Disease Control and Prevention's core elements. All hospitals, regardless of size, are now required to have ASPs by The Joint Commission, and the Centers for Medicare and Medicaid Services has proposed a similar requirement. Very few studies have described the successful implementation of ASPs in small hospitals. We describe barriers commonly encountered in small hospitals when constructing an antibiotic stewardship team, obtaining appropriate metrics of antibiotic prescribing, implementing antibiotic stewardship interventions, obtaining financial resources, and utilizing the microbiology laboratory. We propose potential solutions that tailor stewardship activities to the needs of the facility and the resources typically available.

Associations Between Neurocognitive Impairment and Biomarkers of Poor Physiologic Reserve in a Clinic-Based Sample of Older Adults Living with HIV

Data from a cross-sectional study of a clinic-based sample of older people living with HIV (PLWH; n = 100) were used to examine associations between biomarkers of physical health and neurocognitive impairment (NCI). In this sample, anemia, chronic kidney disease (CKD) stages 4-5, and hypocalcemia were associated with impairment in executive functioning or processing speed. Furthermore, participants with anemia were more likely to have CD4+ T cell counts <200 cells/mm³ (χ² [1] = 19.57, p < .001); hypocalcemia (χ² [1] = 17.55, p < .001); and CKD 4-5 (χ² [2] = 10.12, p = .006). Black and Hispanic participants were more likely to be anemic compared to other races and ethnicities (χ² [3] = 12.76, p = .005). Common medical conditions (e.g., anemia, hypocalcemia, CKD) should be investigated as potential contributors to NCI in older PLWH. Additionally, laboratory testing in racial/ethnic minority PLWH may help inform NCI screening.

Safety of Seasonal Influenza Vaccination in Hospitalized Surgical Patients: A Cohort Study

BACKGROUND

Despite recommendations to vaccinate surgical inpatients against influenza, vaccination rates remain low in this population, due in part to concerns about potential negative effects on postsurgical care.

OBJECTIVE

To evaluate whether influenza vaccination in the perioperative period increases health care utilization and evaluations for postsurgical infection after discharge.

DESIGN

Retrospective cohort study.

SETTING

Members of Kaiser Permanente Southern California.

PARTICIPANTS

Patients aged 6 months or older who had inpatient surgery with admission and discharge between 1 September and 31 March from 2010 to 2013.

MEASUREMENTS

All influenza vaccinations administered between 1 August and 30 April in the 2010-2011, 2011-2012, and 2012-2013 influenza seasons. Outcomes included rates of outpatient visits, readmission, emergency department (ED) visits, fever (temperature ≥38.0 °C), and clinical laboratory evaluations for infection (urine culture, complete blood count, blood culture, and wound culture) in the 7 days after discharge.

RESULTS

Of the 42 777 surgeries included in adjusted analyses, vaccine was administered during hospitalization in 6420. No differences were detected between the vaccinated and unvaccinated groups in risk for inpatient visits (rate ratio [RR], 1.12 [95% CI, 0.96 to 1.32]), ED visits (RR, 1.07 [CI, 0.96 to 1.20]), postdischarge fever (RR, 1.00 [CI, 0.76 to 1.31]), or clinical evaluations for infection (RR, 1.06 [CI, 0.99 to 1.13]). A marginal increase in risk for outpatient visits (RR, 1.05 [CI, 1.00 to 1.10]; P = 0.032) was found.

LIMITATION

The study did not distinguish between planned and unplanned readmissions or outpatient visits.

CONCLUSION

No strong evidence of increased risk for adverse outcomes was found in comparisons of patients who received influenza vaccine during a surgical hospitalization and those who did not. The data support the recommendation to vaccinate surgical inpatients against influenza.

PRIMARY FUNDING SOURCE

Centers for Disease Control and Prevention.

An unblinded, randomised phase II study of platinum-based chemotherapy with vitamin B12 and folic acid supplementation in the treatment of lung cancer with plasma homocysteine blood levels as a biomarker of severe neutropenic toxicity

Background

Vitamin B₁₂ and folic acid (referred to as vitamin supplementation) improves the toxicity profile of pemetrexed containing regimens. Low baseline vitamin B₁₂ and folate levels are reflected in a raised total homocysteine level (HC). Studies have suggested that pretreatment HC levels predict neutropenia toxicity. We have tested supplementation with vitamin B₁₂ and folate in non-pemetrexed platinum-based regimens to decrease treatment-related toxicity and looked for a correlation between toxicity and change in homocysteine levels.

Patient and method

Eighty-three patients with advanced lung cancer and malignant mesothelioma were randomly assigned to receive platinum-based chemotherapy with (arm A) or without (arm B) vitamin B₁₂ and folic acid supplementation. The primary end point was grade 3/4 neutropenia and death within 30 days of treatment. Secondary end points included quality of life, overall survival (OS) and the relationship between baseline and post supplementation HC levels and toxicity.

Results

In the intention-to-treat population, no significant difference was seen between the two groups with respect to chemotherapy-induced grade 3/4 neutropenia and death within 30 days of chemotherapy (36% vs 37%; p=0.966, emesis (2% vs 6%; p=0.9) or OS (12.3 months vs 7 months; p=0.41). There was no significant difference in survival rates by baseline HC level (p=0.9). Decrease in HC with vitamin supplementation was less frequent than expected. High baseline HC levels decreased with vitamin supplementation in only 9/36 (25%) patients (successful supplementation). Post hoc analysis showed that patients in arm A who were successfully supplemented (9/36=25%) had less neutropenic toxicity (0% vs 69%; p=0.02) compared to unsupplemented patients.

Conclusions

The addition of vitamin B₁₂ and folic acid to platinum-containing regimens did not overall improve the toxicity, quality of life or OS. Rates of grade 3/4 neutropenia at 36/37% was as predicted. Further studies to increase the rate of successful supplementation and to further test the biomarker potential of post supplementation HC levels in predicting chemotherapy-induced neutropenia in platinum-based chemotherapy are warranted.

Trial registration number:

EudracCT 2005-002736-10 ISRCTN8734355.

Incidence of polymerase chain reaction-diagnosed Clostridium difficile in a large high-risk cohort, 2011-2012

OBJECTIVE

To describe incidence rates (IRs) of polymerase chain reaction (PCR)-diagnosed Clostridium difficile infection (CDI) in a large high-risk cohort.

PATIENTS AND METHODS

Members of Kaiser Permanente Southern California 1 year or older who were admitted to any of 14 Kaiser Permanente hospitals from January 1, 2011, through December 31, 2012, were included in the study. The CDI cases were identified by PCR in the inpatient and outpatient settings. The CDI IRs per 10,000 inpatient-days are estimated by year, surveillance category, age, sex, race/ethnicity, and Charlson comorbidity index. Recurrence rates are presented by age, sex, and race/ethnicity. Death and colectomy in the 30 days after CDI diagnosis, white blood cell count, and serum creatinine level are assessed.

RESULTS

Among 268,655 patients, 4286 (1.6%) had CDI. Among these patients, 671 (15.7%) had recurrent infections. The IR was highest among community-onset, health care facility-associated infections (11.1 per 10,000 inpatient-days). The CDI IRs differed by age, sex, and race/ethnicity. Overall, 528 patients (12.3%) died within 30 days of a positive CDI test result. The CDI IRs increased 34% with implementation of PCR testing.

CONCLUSION

Increasingly, PCR is being used because of its higher diagnostic sensitivity. Reassessing the epidemic using PCR updates our understanding of CDI risk. Our capacity to identify patients presenting in the outpatient setting after discharge provides a more accurate picture of health care-associated CDI rates, particularly because the community appears to assume an increasing role in CDI onset and possibly transmission. The CDI burden differs by race, comorbidity, sex, and previous health care use. The detected increase in CDI incidence after transitioning to PCR diagnosis was modest compared with previous studies.

Late presentation of simple virilising 21-hydroxylase deficiency in a Chinese woman with Turner's syndrome

Classical congenital adrenal hyperplasia due to 21-hydroxylase deficiency is a well-known disorder of sexual development (previously known as ambiguous genitalia) in genotypic female neonates. We report on a 66-year-old Chinese, brought up as male, with a simple virilising form of congenital adrenal hyperplasia associated with Turner's syndrome (karyotype 45,X/47,XXX/46,XX). His late presentation was recognised due to his exceptionally short stature and persistent sexual ambiguity. His condition was only brought to medical attention as he developed a huge abdominal mass, which later turned out to be a benign ovarian mucinous cyst. It is therefore important to look out for co-existing congenital adrenal hyperplasia in patients with Turner's syndrome and virilisation, after the presence of Y chromosome material has been excluded.

Rainwater harvesting in schools in Taiwan: system characteristics and water quality

In order to understand the current status of rainwater harvesting (RWH) practices in Taiwan's schools, a study was carried out to examine the RWH system performance, water usage, and water quality in these sites. A total of 29 schools in various regions were selected for this investigation, including 7 in the northern, 7 in the central, 8 in the southern, and 7 in the eastern regions of Taiwan. Water quality indicators tested were: pH, temperature, conductivity, oxidation-reduction potential, suspended solid, total organic carbon, fecal coliform, and total coliform. From this study, it was found that RWH systems in these sites generally had two different designs: one that collected rainwater only, and one that collected both rainwater and grey water. From statistical analysis, it was found that water quality indicators such as suspended solids, total organic carbon, and fecal coliform were significantly affected by the water source and site location. Fecal coliforms in most of the sites we studied were high and not qualified for toilet flushing. The average water retention time of 2.4 months was long and considered to be the main reason to cause high fecal coliform counts. Finally, the benefit analysis was conducted to evaluate economic feasibility of rainwater harvesting for these schools. It turned out that 20% of them were able to gain economic benefits from using rainwater.

Cell Cycle Stage Analysis of Rabbit Foetal Fibroblasts and Cumulus Cells

Synchronization of the cell cycle stages in G0/G1 phase is one of the key factors determining the success of nuclear transplantation. Serum deprivation, contact inhibition and chemical inhibitors are widely used methods for this purpose. In this study, cell cycle stages of foetal fibroblasts and cumulus cells were determined using flow cytometry [fluorescence-activated cell scan (FACS)]. Foetal fibroblasts (in vitro cultured for 72-120 h) and fresh cumulus cells were analysed in Experiment 1. Fifty to 55% proliferating fibroblasts remained in G0/G1 phase compared with 78% in confluent culture (p <0.05). In contrast to foetal fibroblasts, fresh cumulus cells maintained 90% of the population in the G0/G1 stage. When serum was retrieved from the proliferating fibroblasts from day 1 to day 5 (Experiment 2), proportions of G0/G1 cells increased from the initial ratio of 53 to 87% at day 4 of starvation, which was significantly higher than the non-starved proliferating cells (p <0.05). In Experiment 3, fibroblasts were treated with aphidicolin (0.1 microg/ml, 6 h), demicolcine (0.5 microg/ml, 10 h), or a combination of these two chemicals to synchronize the cell cycle stages. Surprisingly, no differences or significantly lower in the proportions of G0/G1)phase cells were detected (25-50%) compared with the uncontrolled growing cells (53%). These results suggested that fresh cumulus cells rest their cell cycle in G0/G1 stage. Serum deprivation became effective in the first 24 h and reached the highest proportions during days 4-5 after deprivation. Chemical synchronization of the cell cycle stage of rabbit foetal fibroblasts to G0/G1 phase appeared less effective compared to serum deprivation.

Correlations of extractable heavy metals with organic matters in contaminated river sediments

In southern Taiwan, almost all the main rivers have been contaminated by anthropogenic heavy metals and organic matters. The main pollution sources include agricultural, industrial, and domestic activities. River sediments potentially have large capacities to accumulate heavy metals and organic matters when the river water flows through it. The sediments sampled from high contaminated river (the Yenshui River) and moderately contaminated rivers (the Tsengwen, Chishui, Potzu, and Peikang Rivers) were used to realize correlations between each kind of aqua regia extractable heavy metals (Co, Cr, Cu, Zn, Ni, Pb, Mn, and Fe) and organic matters in vertical sediment cores. Organic matters and aqua regia extractable heavy metal concentrations, analyzed by strong acid-digested extraction, were determined in vertical profile segments from downstream sediments of the five rivers. Sum of six aqua regia extractable heavy metals (Co, Cr, Cu, Zn, Ni, and Pb) were below 3,000 mg/kg in sediments of the Yenshui River, and below 500 mg/kg in the other four rivers' sediments. Strongly positive correlations (r = 0.83-0.95) between each kind of aqua regia extractable heavy metals and organic matters (concentration range between 0.6 to 3.8%) were observed in sediments of the Yenshui River. The slopes of the linear regressive lines approximated the average metal complexation ratios with organic matters in the sediments. In sediments of the other four rivers, smaller positive correlation coefficients between aqua regia extractable heavy metals and organic matters (below 2.6%) were observed. The complexation ratios derived from the four moderately polluted river sediments were smaller than those derived from the highly contaminated river sediments, indicating that the importance of organic matters in the accumulation of heavy metals in river sediments.

Chemical binding of heavy metals in anoxic river sediments

Acid volatile sulfides (AVS) in sediments are available for binding with divalent cationic metals through the formation of insoluble metal-sulfide complexes, thereby controlling the metal bioavailability and subsequent toxicity to benthic biocommunities. However, when the molar concentrations of simultaneously extracted metals (SEM) were greater than AVS, the unexpectedly low or nondetectable levels of metal in pore water could also be found. Thus, except AVS, additional binding phases in sediments were supposed to provide the binding sites for SEM. The aims of this study are to realize the spatial distribution of AVS, SEM, and other binding phases of heavy metals in anoxic sediments of the Ell-Ren river and to elucidate what may be the main additional binding phases except AVS in the anoxic river sediments. By comparing the spatial distributions of SEM/ AVS ratio with various binding phases in extremely anoxic sediments (redox potential was between -115 and -208 mV), both organic matter and carbonates could be considered to be the main additional binding phases of SEM other than AVS. In addition, AVS appeared to have the priority to bind with SEM. By comparing the binding phases of heavy metals before and after AVS extraction, it could be found that Fe-oxides could also be considered to be the main additional binding phase associated with Zn in slightly anoxic sediments (redox potential was between -50 and -130mV), while organic matter with Cu being the next.

CO(2) laser treatment in 244 patients with respiratory papillomas

OBJECTIVE

Respiratory papillomas (RP) tend to recur and the difficulty in eradicating the disease makes their treatment frustrating. Meticulous CO(2) laser excisions every 2 months has been the most effective treatment to date. This article analyzes the results of this plan in 244 patients with RP in the nose, nasopharynx, pharynx, hypopharynx, larynx, trachea, lung parenchyma, and skin.

METHODS

Two hundred forty-four patients with recurrent RP were treated by the senior author with CO(2) laser excisions and, in some cases, podophyllum and alpha interferon. Demographics, initial distribution of papillomas, number of operations performed on each patient, and current results were evaluated.

RESULTS

Careful laser excisions of RPs every 2 months achieved "remission" of disease (no visible RP on indirect or often direct laryngoscopy 2 mo after last removal) in 37% of patients, "clearance" of the disease process (no RP clinically apparent for 3 y after last removal) in 6%, and "cure" (no clinical recurrence for 5 y after last removal) in 17%. Juvenile-onset RP tends to follow a more aggressive course than adult-onset RP. Four patients (1.6%) developed malignant transformation of their papillomas. Except for ones in lung parenchyma, RP in areas other than the true vocal cords tend to be cleared faster because aggressive removal does not cause hoarseness. Lung parenchyma RPs are eventually fatal because of pulmonary failure from abscesses and cysts resulting from a lack of effective treatment.

CONCLUSION

Frequent and meticulously performed CO(2) laser excisions can achieve significant voice and airway improvement, and some clinical "cures." However, effective antiviral medicines and/or immunologic agents are needed to achieve true cures with elimination of all human papilloma virus 6 and 11 viruses.

Correlation analyses on binding behavior of heavy metals with sediment matrices

This article presents the amounts of heavy metals bound to the sediment matrices (carbonates, Fe-oxides, Mn-oxides, and organic matter), the correlations between any two heavy-metal binding fractions, and the correlations between sediment matrices and their heavy-metal binding fractions. Data consisted of 313 sets obtained from five main rivers (located in southern Taiwan) were analyzed by statistical methods. Among six heavy metals analyzed (Zn, Cu. Pb, Ni, Cr, and Co), the statistical results show that Zn is primarily bound to organic matter, and Cr is primarily bound to Fe-oxides. Principal component analysis (PCA) and correlation analysis (CA) result in significant correlations between carbonates bound Ni and carbonates bound Cr, Fe-oxides bound Ni and Fe-oxides bound Cr, and Mn-oxides bound Cu and Mn-oxides bound Cr. From linear regression results, the levels of the six heavy metals bound to either organic matter or Fe-oxides is moderately dependent on the contents of organic matter or Fe-oxides, especially true for Cr and Pb. According to slope values of linear regression, Cu and Cr have the highest specific binding amounts (SBA) to organic matter and Fe-oxides, respectively. A significant correlation between organic matter and organically bound heavy metals implied that organic matter contained in the sediments of the Potzu river and the Yenshui river can be adequately used as a normalizing agent. However, the six heavy metals bound to either carbonates or Mn-oxides do not correlate with carbonates or Mn-oxides. The obtained results also imply that competitions of various sediment phases in association with heavy metals occur, and organic matter and Fe-oxides are more accessible to heavy metals than other sediment phases.

Conservative management of infections in cochlear implant recipients

OBJECTIVE

The goal of this study was to evaluate a conservative management strategy of postoperative infection after cochlear implantation.

METHODS

A retrospective review of the medical records of 108 cochlear implant patients operated on at the University of California, San Francisco between 1991 and 2000 and 133 cochlear implant patients from the University of Iowa between 1997 and 2000 showed 4 patients with evidence of postoperative infections. The clinical presentation, intervention, laboratory results, and outcome are analyzed in each case.

RESULTS

Minimal surgical intervention with limited incision and drainage with prolonged postoperative antibiotics was effective in treating postoperative cochlear implant infections without the need for device removal. Implant function remained unaffected after surgery.

CONCLUSION

Postoperative cochlear implant infections can be effectively controlled with limited surgical and prolonged medical management. Chronic implant infections may be explained by a primary immunodeficiency. With appropriate treatment leading to infection control, a conservative management strategy is advocated before consideration of device explantation.

LDL receptor-related protein mediates cell-surface clustering and hepatic sequestration of chylomicron remnants in LDLR-deficient mice

It has been proposed that in the liver, chylomicron remnants (lipoproteins carrying dietary lipid) may be sequestered before being internalized by hepatocytes. To study this, chylomicron remnants labeled with a fluorescent dye were perfused into isolated livers of LDL receptor-deficient (LDLR-deficient) mice (Ldlr(-/-)) and examined by confocal microscopy. In contrast to livers from normal mice, there was clustering of the chylomicron remnants on the cell surface in the space of DISSE: These remnant clusters colocalized with clusters of LDLR-related protein (LRP) and could be eliminated by low concentrations of receptor-associated protein, an inhibitor of LRP. When competed with ligands of heparan sulfate proteoglycans (HSPGs), the remnant clusters still appeared but were fewer in number, although syndecans (membrane HSPGs) colocalized with the remnant clusters. This suggests that the clustering of remnants is not dependent on syndecans but that the syndecans may modify the binding of remnants. These results establish that sequestration is a novel process, the clustering of remnants in the space of DISSE: The clustering involves remnants binding to the LRP, and this may be stabilized by binding with syndecans, eventually followed by endocytosis.

Postprandial lipoproteins and atherosclerosis

During the postprandial state, dietary lipid is transported from the intestine to peripheral tissues by plasma lipoproteins called chylomicrons. In the capillary beds of peripheral tissues, chylomicron triglycerides are lipolyzed by the enzyme, lipoprotein lipase, allowing the delivery of free fatty acids to the cells. As a result, this produces a new particle of smaller size and enriched with cholesteryl ester referred to as chylomicron remnants. These particles are rapidly removed from the blood primarily by the liver. The liver has a complex chylomicron remnant removal system which is comprised of a combination of different mechanisms that include the low-density-lipoprotein receptor (LDLR) and the LDLR-related-protein (LRP). Furthermore, it has been suggested that there is a sequestration component whereby chylomicron remnants bind to heparan sulfate proteoglycans (HSPG) and/or hepatic lipase; this is then followed by transport to one or both of the above receptors for hepatic uptake. Over the years, a major concern has arisen about the association of chylomicron remnants and coronary heart disease (CHD) in man. Slow removal of chylomicron remnants, as reflected by a prolonged postprandial state, is now commonly observed in patients with CHD and those that have abnormal lipid disorders such as hypertriglyceridemia, familial hypercholesterolemia, familial combined hyperlipidemia and non-insulin-dependent-diabetes-mellitus. The present review will focus on (a) the details of the metabolic pathway (exogenous pathway) that describes the two-step processing of postprandial lipoproteins, (b) the role of the liver, the receptors, and the importance of efficient removal of chylomicron remnants from the blood circulation, and (c) the potential atherogenic effects of chylomicron remnants on the arterial wall.

Multivariate correlations of geochemical binding phases of heavy metals in contaminated river sediment

Distributions of geochemical binding phases of seven heavy metals (Cr, Cu, Co, Zn, Ni, Pb, and Cd) in sediment cores taken from six heavily polluted sites of the Ell-Ren River in Southern Taiwan were studied. Sequential extraction procedures (SEP) were used to determine the variations of heavy metal binding phases (exchangeable, bound to carbonates, bound to manganese-oxides, bound to iron-oxides, and bound to organic matter) in different sediment depths. Multivariate analyses were used to explore the correlations among these geochemical binding phases of heavy metals. Results showed that the total amounts of various binding phases of heavy metals significantly varied with sediment depth, but their binding behaviors in various phases did not significantly change with depth. The organic matter content in the sediments increased with increasing Fe-oxide content. In addition, the binding affinities of carbonates with Zn, Pb, and Ni were higher than the affinities of carbonates with the other heavy metals. The binding affinity of Fe-oxides with Cr was higher than the affinities of Fe-oxides with the other heavy metals. Both correlation matrixes and principal component analyses demonstrated that distributions of Cu, Zn, Ni, and Cd had significant correlations with each other in both different depth horizons and various geochemical binding phases. The results indicate that these heavy metals might be discharged from the same pollution sources in the past, and also showed stable geochemical binding behaviors with the high silt sediment. However, Co had a poor correlation with the other six heavy metals in various binding phases, except with organic matter. Binding behaviors of Pb in the phases of bound to carbonates and exchangeable were different from the other six heavy metals. Cu was inversly correlated with the other six heavy metals in its binding behavior with reducible phases (Fe-/Mn-oxides).

Inner ear malformations and hearing loss in linear nevus sebaceous syndrome

OBJECTIVE

Linear nevus sebaceous syndrome (LNSS) is a rare disorder comprising of nevus sebaceous, seizures, and mental retardation. While extensive literature describe the dermatologic, neurologic, as well as ophthalmologic manifestations of this LNSS, otologic problems have not been previously described. The objective of this report is to describe the otologic manifestation of a patient with LNSS.

METHODS

A child with LNSS was referred to the Otologic clinic for evaluation of hearing loss. Pertinent findings on history, physical findings, audiometric testing, and imaging studies are discussed.

RESULTS

Audiometric testing showed bilateral conductive hearing loss. Computerized tomography of the temporal bone demonstrated widened internal auditory canals and dysplastic lateral semicircular canals.

CONCLUSION

LNSS can be associated with hearing impairment and inner ear malformations. The evaluation of a child with LNSS should include otologic and audiologic testing.

Rapid initial removal of chylomicron remnants by the mouse liver does not require hepatically localized apolipoprotein E

Apolipoprotein E (apoE) is a ligand for the low density lipoprotein receptor (LDLR) and the low density lipoprotein receptor-related protein (LRP). The aim of the present study was to clarify the role of hepatically localized apoE in the rapid initial removal of chylomicron remnants by using the isolated perfused liver. Radiolabeled chylomicron remnants were perfused in a single nonrecirculating pass into the livers of C57BL/6J (wild-type) mice, apoE-knockout mice, and apoE/LDLR-knockout mice for a period of 20 min. Aliquots of the perfusate leaving the liver were collected at regular intervals and the rate of removal of radioactivity was determined. At a trace concentration of chylomicron remnants (0.05 microgram of protein per ml), wild-type mouse livers removed at a steady state of 50-55% of total chylomicron remnants perfused per pass; livers from apoE-knockout mice had the same capacity as wild-type mouse livers. When the concentration of remnants was increased to 12 microgram of protein per ml, a level at which it has been shown that LDL receptor and LRP are near saturation, the capacity of the wild-type mouse livers to remove chylomicron remnants was decreased to 10-25% per pass, confirming that the removal mechanisms were nearing saturation. However, instead of finding a greater reduction in the removal rates or impairment in chylomicron remnant removal, livers from apoE-knockout mice were just as efficient as those from wild-type mice in removing remnants. Livers of mice that lacked both apoE and the LDLR also had a similar rate of removal at relatively low remnant concentrations (0.05-0.5 microgram/ml), but had reduced capacity in removing remnants at a relatively high concentration (4-12 microgram/ml) of chylomicron remnants ( approximately 20% per pass). The rate of removal at these concentrations, however, was similar to that attributed to the LRP in previous studies. Chylomicron remnants, whose apolipoproteins were disrupted by trypsinization, were removed at a normal rate by wild-type mouse livers but there was almost no removal by apoE-knockout mouse livers. At higher concentrations, however, the removal of apolipoprotein-disrupted chylomicron remnants was decreased. Our present findings do not support the hypothesis that hepatically localized apoE is a critical factor in the rapid initial removal of chylomicron remnants by either of the major pathways but do suggest that hepatically localized apoE can be added to lipoproteins to accelerate their uptake, although this process may have a limited capacity to compensate for apoE deficiency on lipoproteins.

Chylomicron-remnant-induced foam cell formation and cytotoxicity: a possible mechanism of cell death in atherosclerosis

The effects of chylomicron remnants on cytoplasmic lipid loading and cell viability were assessed in cultures of human monocyte-derived macrophages and rabbit arterial smooth muscle cells. At a cholesterol concentration of 150 microg/ml, chylomicron remnants induced substantial cytoplasmic lipid loading of macrophages, but not of smooth muscle cells, within 6 h of exposure. Chylomicron remnants were found to be cytotoxic to macrophages and smooth muscle cells, although the latter were generally more resistant. Chylomicron remnants contained no detectable oxysterols (>1 ng) and contained less non-esterified ('free') fatty acids than non-lipolysed nascent chylomicrons. Chylomicron-remnant-induced cytotoxicity appeared to be time- and dose-dependent. Macrophage and smooth muscle cell viability were inversely related to the production of superoxide free radicals and were significantly improved in the combined presence of superoxide dismutase and catalase. Collectively, our data suggest that, in macrophages, cell viability is compromised as a consequence of superoxide free radical production following uptake of chylomicron remnants. We would suggest that, in arterial smooth muscle cells, chylomicron-remnant-induced cell death also occurs as a consequence of superoxide free radical production. Our observations in the present study suggest that macrophage foam cells in atherosclerotic plaques might be derived from the cellular uptake of chylomicron remnants. Furthermore, arterial accumulation of chylomicron remnants might contribute to plaque destabilization as a consequence of cell death following superoxide free radical production by macrophages and smooth muscle cells.

Evaluation of the components of the chylomicron remnant removal mechanism by use of the isolated perfused mouse liver

The isolated perfused mouse liver was utilized to evaluate the relative contribution of various molecules believed to participate in the removal of chylomicron remnants by the liver. Sixty percent of asialofetuin was removed from the perfusate per pass; bovine serum albumin was not removed. Normal mouse livers removed chylomicron remnants more efficiently (40-50%/pass) than nascent chylomicrons (10-20%/pass). The fractional removal rate of remnants decreased as their concentration in the perfusate increased demonstrating saturability. Remnant removal by livers of low density lipoprotein receptor-deficient (LDLRD) mice paralleled that of normal mice at low remnant concentrations (0.05, 0.2 microg protein/ml); as concentration increased (4-16 microg protein/ml), removal by LDLRD livers was reduced. About 50% of the capacity to remove remnants was due to the LDL receptor. The role of the LDLR-related protein (LRP) was estimated using the receptor-associated protein (RAP). Four microg/ml of RAP inhibited only LRP; it reduced the removal of remnants by 30-40% in normal livers. When RAP was included in the perfusate of LDLRD livers, remnant removal persisted but was diminished, particularly late in the perfusion; the capacity was approximately 30% of controls. The present study has established that there is more than one mechanism operating for the removal of chylomicron remnants by the liver, provides estimates of the concentration of each to the removal of remnants, and indicates a method for further studies. It is concluded that in normal livers, the LDL receptor has the greatest capacity for removing chylomicron remnants. The LRP contributes to the process as well and a third component, perhaps "sequestration," accounts for up to 30% of the capacity for the initial removal of chylomicron remnants.

Accumulation of chylomicron remnants in homozygous subjects with familial hypercholesterolaemia

BACKGROUND

Post-prandial lipoprotein kinetics were investigated in subjects who lack functioning low-density lipoprotein (LDL) receptors [homozygous familial hypercholesterolaemia (FH)].

METHODS

An oral fat load was given, and chylomicron plasma kinetics was determined by monitoring the clearance of triglyceride, retinyl palmitate and apolipoprotein B48, calculated as the area under the curve, for 7.5 h. In addition, the binding and uptake of chylomicron remnants by fibroblasts of FH and control subjects were assessed in vitro.

RESULTS

Based on the plasma kinetics of chylomicron triglyceride, retinyl palmitate and apolipoprotein B48 after a lipid meal, chylomicron clearance was found to be substantially delayed compared with normolipidaemic control subjects. Consistent with involvement of the LDL receptor in chylomicron clearance, binding and uptake of chylomicron remnants by fibroblasts of FH subjects was found to be substantially less than in cells from control subjects.

CONCLUSION

This study shows that, in addition to LDL, chylomicron metabolism is severely impaired in FH and that the LDL receptor is significantly involved in the clearance of post-prandial lipoproteins. Moreover, this study raises the possibility that in FH, and in other disorders in which LDL receptor expression is reduced, atherogenesis might be a post-prandial disease.

Cerebellopontine angle tumor outcomes in patients with hazardous occupations

Cerebellopontine angle (CPA) tumor surgery can produce a spectrum of sensory and motor deficits that can alter a patient's lifestyle and occupation. An important consideration is whether patients can return to full occupational status especially when hazardous duties are involved. Outcome data in CPA tumor surgery usually report that most patients are able to return to preoperative function; however, whether these patients can return to hazardous duties is not specified. A retrospective study of 380 consecutive, operated CPA tumor patients was performed and 37 were identified who engaged in hazardous occupations including active military service, working at dangerous heights, piloting jet aircraft, aircraft navigating, and factory work with high-impact machinery. Overall, patients were able to resume full-time work in their previous occupations and 86% of patients reported that they were able to resume hazardous duties. CPA tumor surgery is compatible with continued full occupational duties after surgery, even for patients employed in hazardous situations.

Binding and uptake of chylomicron remnants by cultured arterial smooth muscle cells from normal and Watanabe-heritable-hyperlipidemic rabbits

Chylomicron remnants (RM's) may be involved in atherogenesis because they can be delivered to the subendothelial space of arterial vessels and serve as substrate for arterial cells. A number of proteins may bind RM's, however, the quantitative significance of these is not established. The aim of this study was to identify the primary RM binding site of arterial smooth muscle cells (SMC's). At 4 degrees C, SMC's displayed saturable high affinity binding of RM's. In receptor competition studies, LDL inhibited binding of RM's by almost 60% suggesting involvement of the apolipoprotein B100/E receptor. Unlabeled RM's were more effective with an EC50 significantly less than for unlabeled LDL. Furthermore, at 37 degrees C RM uptake was three times greater than LDL, consistent with greater affinity of the apolipoprotein B100/E receptor for lipoproteins containing apolipoprotein E. In SMC's from homozygote Watanabe heritable hyperlipidemic (WHHL) rabbits, the binding and degradation of chylomicron remnants was severely impaired. SMC's from cross-bred WHHL rabbits exhibited levels of binding and degradation intermediate between homozygote WHHL rabbits and controls. We confirmed that the apolipoprotein B100/E receptor is the primary mechanism by which arterial smooth muscle cells bind and degrade RM's using a polyclonal antibody which specifically recognises the receptor. In the presence of the antibody, RM binding and degradation were inhibited by 90%.