Whole-Genome Sequencing Reveals Diversity of Carbapenem-Resistant Pseudomonas aeruginosa Collected through CDC's Emerging Infections Program, United States, 2016-2018.

The CDC's Emerging Infections Program (EIP) conducted population- and laboratory-based surveillance of US carbapenem-resistant Pseudomonas aeruginosa (CRPA) from 2016 through 2018. To characterize the pathotype, 1,019 isolates collected through this project underwent antimicrobial susceptibility testing and whole-genome sequencing. Sequenced genomes were classified using the seven-gene multilocus sequence typing (MLST) scheme and a core genome (cg)MLST scheme was used to determine phylogeny. Both chromosomal and horizontally transmitted mechanisms of carbapenem resistance were assessed. There were 336 sequence types (STs) among the 1,019 sequenced genomes, and the genomes varied by an average of 84.7% of the cgMLST alleles used. Mutations associated with dysfunction of the porin OprD were found in 888 (87.1%) of the genomes and were correlated with carbapenem resistance, and a machine learning model incorporating hundreds of genetic variations among the chromosomal mechanisms of resistance was able to classify resistant genomes. While only 7 (0.1%) isolates harbored carbapenemase genes, 66 (6.5%) had acquired non-carbapenemase ß-lactamase genes, and these were more likely to have OprD dysfunction and be resistant to all carbapenems tested. The genetic diversity demonstrates that the pathotype includes a variety of strains, and clones previously identified as high-risk make up only a minority of CRPA strains in the United States. The increased carbapenem resistance in isolates with acquired non-carbapenemase ß-lactamase genes suggests that horizontally transmitted mechanisms aside from carbapenemases themselves may be important drivers of the spread of carbapenem resistance in P. aeruginosa.

Characteristics of Adults Aged 18-49 Years Without Underlying Conditions Hospitalized With Laboratory-Confirmed Coronavirus Disease 2019 in the United States: COVID-NET-March-August 2020.

Among 513 adults aged 18-49 years without underlying medical conditions hospitalized with coronavirus disease 2019 (COVID-19) during March 2020-August 2020, 22% were admitted to an intensive care unit, 10% required mechanical ventilation, and 3 patients died (0.6%). These data demonstrate that healthy younger adults can develop severe COVID-19.

Changes in Prevalence of Health Care-Associated Infections in U.S. Hospitals.

BACKGROUND: A point-prevalence survey that was conducted in the United States in 2011 showed that 4% of hospitalized patients had a health care-associated infection. We repeated the survey in 2015 to assess changes in the prevalence of health care-associated infections during a period of national attention to the prevention of such infections. METHODS: At Emerging Infections Program sites in 10 states, we recruited up to 25 hospitals in each site area, prioritizing hospitals that had participated in the 2011 survey. Each hospital selected 1 day on which a random sample of patients was identified for assessment. Trained staff reviewed medical records using the 2011 definitions of health care-associated infections. We compared the percentages of patients with health care-associated infections and performed multivariable log-binomial regression modeling to evaluate the association of survey year with the risk of health care-associated infections. RESULTS: In 2015, a total of 12,299 patients in 199 hospitals were surveyed, as compared with 11,282 patients in 183 hospitals in 2011. Fewer patients had health care-associated infections in 2015 (394 patients [3.2%; 95% confidence interval {CI}, 2.9 to 3.5]) than in 2011 (452 [4.0%; 95% CI, 3.7 to 4.4]) (P<0.001), largely owing to reductions in the prevalence of surgical-site and urinary tract infections. Pneumonia, gastrointestinal infections (most of which were due to Clostridium difficile [now Clostridioides difficile]), and surgical-site infections were the most common health care-associated infections. Patients' risk of having a health care-associated infection was 16% lower in 2015 than in 2011 (risk ratio, 0.84; 95% CI, 0.74 to 0.95; P=0.005), after adjustment for age, presence of devices, days from admission to survey, and status of being in a large hospital. CONCLUSIONS: The prevalence of health care-associated infections was lower in 2015 than in 2011. To continue to make progress in the prevention of such infections, prevention strategies against C. difficile infection and pneumonia should be augmented. (Funded by the Centers for Disease Control and Prevention.).

Carbapenem-Resistant Pseudomonas aeruginosa at US Emerging Infections Program Sites, 2015.

Pseudomonas aeruginosa is intrinsically resistant to many antimicrobial drugs, making carbapenems crucial in clinical management. During July-October 2015 in the United States, we piloted laboratory-based surveillance for carbapenem-resistant P. aeruginosa (CRPA) at sentinel facilities in Georgia, New Mexico, Oregon, and Tennessee, and population-based surveillance in Monroe County, NY. An incident case was the first P. aeruginosa isolate resistant to antipseudomonal carbapenems from a patient in a 30-day period from any source except the nares, rectum or perirectal area, or feces. We found 294 incident cases among 274 patients. Cases were most commonly identified from respiratory sites (120/294; 40.8%) and urine (111/294; 37.8%); most (223/280; 79.6%) occurred in patients with healthcare facility inpatient stays in the prior year. Genes encoding carbapenemases were identified in 3 (2.3%) of 129 isolates tested. The burden of CRPA was high at facilities under surveillance, but carbapenemase-producing CRPA were rare.

Carbapenem-Nonsusceptible Acinetobacter baumannii, 8 US Metropolitan Areas, 2012-2015.

In healthcare settings, Acinetobacter spp. bacteria commonly demonstrate antimicrobial resistance, making them a major treatment challenge. Nearly half of Acinetobacter organisms from clinical cultures in the United States are nonsusceptible to carbapenem antimicrobial drugs. During 2012-2015, we conducted laboratory- and population-based surveillance in selected metropolitan areas in Colorado, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon, and Tennessee to determine the incidence of carbapenem-nonsusceptible A. baumannii cultured from urine or normally sterile sites and to describe the demographic and clinical characteristics of patients and cases. We identified 621 cases in 537 patients; crude annual incidence was 1.2 cases/100,000 persons. Among 598 cases for which complete data were available, 528 (88.3%) occurred among patients with exposure to a healthcare facility during the preceding year; 506 (84.6%) patients had an indwelling device. Although incidence was lower than for other healthcare-associated pathogens, cases were associated with substantial illness and death.

Impact of Prompt Influenza Antiviral Treatment on Extended Care Needs After Influenza Hospitalization Among Community-Dwelling Older Adults.

BACKGROUND: Patients hospitalized with influenza may require extended care on discharge. We aimed to explore predictors for extended care needs and the potential mitigating effect of antiviral treatment among community-dwelling adults aged ≥ 65 years hospitalized with influenza. METHODS: We used laboratory-confirmed influenza hospitalizations from 3 influenza seasons. Extended care was defined as new placement in a skilled nursing home/long-term/rehabilitation facility on hospital discharge. We focused on those treated with antiviral agents to explore the effect of early treatment on extended care and hospital length of stay using logistic regression and competing risk survival analysis, accounting for time from illness onset to hospitalization. Treatment was categorized as early (≤ 4 days) or late (>4 days) in reference to date of illness onset. RESULTS: Among 6593 community-dwelling adults aged ≥ 65 years hospitalized for influenza, 18% required extended care at discharge. The need for care increased with age and neurologic disorders, intensive care unit admission, and pneumonia were predictors of care needs. Early treatment reduced the odds of extended care after hospital discharge for those hospitalized ≤ 2 or >2 days from illness onset (adjusted odds ratio, 0.38 [95% confidence interval {CI}, .17-.85] and 0.75 [.56-.97], respectively). Early treatment was also independently associated with reduction in length of stay for those hospitalized ≤ 2 days from illness onset (adjusted hazard ratio, 1.81; 95% CI, 1.43-2.30) or >2 days (1.30; 1.20-1.40). CONCLUSIONS: Prompt antiviral treatment decreases the impact of influenza on older adults through shorten hospitalization and reduced extended care needs.

Pneumonia among adults hospitalized with laboratory-confirmed seasonal influenza virus infection-United States, 2005-2008.

BACKGROUND: Influenza and pneumonia combined are the leading causes of death due to infectious diseases in the United States. We describe factors associated with pneumonia among adults hospitalized with influenza. METHODS: Through the Emerging Infections Program, we identified adults ≥ 18 years, who were hospitalized with laboratory-confirmed influenza during October 2005 through April 2008, and had a chest radiograph (CXR) performed. Pneumonia was defined as the presence of a CXR infiltrate and either an ICD-9-CM code or discharge summary diagnosis of pneumonia. RESULTS: Among 4,765 adults hospitalized with influenza, 1392 (29 %) had pneumonia. In multivariable analysis, factors associated with pneumonia included: age ≥ 75 years, adjusted odds ratio (AOR) 1.27 (95 % confidence interval 1.10-1.46), white race AOR 1.24 (1.03-1.49), nursing home residence AOR 1.37 (1.14-1.66), chronic lung disease AOR 1.37 (1.18-1.59), immunosuppression AOR 1.45 (1.19-1.78), and asthma AOR 0.76 (0.62-0.92). Patients with pneumonia were significantly more likely to require intensive care unit (ICU) admission (27 % vs. 10 %), mechanical ventilation (18 % vs. 5 %), and to die (9 % vs. 2 %). CONCLUSIONS: Pneumonia was present in nearly one-third of adults hospitalized with influenza and was associated with ICU admission and death. Among patients hospitalized with influenza, older patients and those with certain underlying conditions are more likely to have pneumonia. Pneumonia is common among adults hospitalized with influenza and should be evaluated and treated promptly.

Complications among adults hospitalized with influenza: a comparison of seasonal influenza and the 2009 H1N1 pandemic.

BACKGROUND: Persons with influenza can develop complications that result in hospitalization and death. These are most commonly respiratory related, but cardiovascular or neurologic complications or exacerbations of underlying chronic medical conditions may also occur. Patterns of complications observed during pandemics may differ from typical influenza seasons, and characterizing variations in influenza-related complications can provide a better understanding of the impact of pandemics and guide appropriate clinical management and planning for the future. METHODS: Using a population-based surveillance system, we compared clinical complications using International Classification of Diseases, Ninth Revision (ICD-9) discharge diagnosis codes in adults hospitalized with seasonal influenza (n = 5270) or 2009 pandemic influenza A(H1N1) (H1N1pdm09; n = 4962). RESULTS: Adults hospitalized with H1N1pdm09 were younger (median age, 47 years) than those with seasonal influenza (median age, 68 years; P < .01), and differed in the frequency of certain underlying medical conditions. Whereas there was similar risk for many influenza-associated complications, after controlling for age and type of underlying medical condition, adults hospitalized with H1N1pdm09 were more likely to have lower respiratory tract complications, shock/sepsis, and organ failure than those with seasonal influenza. They were also more likely to be admitted to the intensive care unit, require mechanical ventilation, or die. Young adults, in particular, had 2-4 times the risk of severe outcomes from H1N1pdm09 than persons of the same ages with seasonal influenza. CONCLUSIONS: Although H1N1pdm09 was thought of as a relatively mild pandemic, these data highlight the impact of the 2009 pandemic on the risk of severe influenza, especially among younger adults, and the impact this virus may continue to have.

Comparing clinical characteristics between hospitalized adults with laboratory-confirmed influenza A and B virus infection.

We challenge the notion that influenza B is milder than influenza A by finding similar clinical characteristics between hospitalized adult influenza-cases. Among patients treated with oseltamivir, length of stay and mortality did not differ by type of virus infection.

Patients hospitalized with laboratory-confirmed influenza during the 2010-2011 influenza season: exploring disease severity by virus type and subtype.

BACKGROUND: The 2010-2011 influenza season was dominated by influenza A(H3N2) virus, but influenza A(H1N1) pdm09 (pH1N1) and B viruses cocirculated. This provided an opportunity to explore within-season predictors of severity among hospitalized patients, avoiding biases associated with season-to-season differences in strain virulence, population immunity, and healthcare seeking. METHODS: Population-based, laboratory-confirmed influenza hospitalization surveillance data were used to examine the association between virus type/subtype and outcomes in children and adults. Multivariable analysis explored virus type/subtype, prompt antiviral treatment, medical conditions, and age as predictors for severity (intensive care unit admission or death). RESULTS: In children, pH1N1 (adjusted odds ratio [aOR], 2.19; 95% confidence interval [CI], 1.11-4.3), chronic metabolic disease (aOR, 5.23; 95% CI, 1.74-15.69), and neuromuscular disorder (aOR, 4.84; 95% CI, 2.02-11.58) were independently associated with severity. In adults, independent predictors were pH1N1 (aOR, 2.21; 95% CI, 1.66-2.94), chronic lung disease (aOR, 1.46, 95% CI, 1.12-1.89), and neuromuscular disorder (aOR, 1.68; 95% CI, 1.11-2.52).Antiviral treatment reduced the odds of severity among adults (aOR, 0.47; 95% CI, .33-.68). CONCLUSIONS: During the 2010-2011 season, pH1N1 caused more severe disease than H3N2 or B in hospitalized patients. Underlying medical conditions increased severity despite virus strain. Antiviral treatment reduced severity among adults. Our findings underscore the importance of influenza prevention.

Effect of the 2009 influenza A(H1N1) pandemic on invasive pneumococcal pneumonia.

BACKGROUND: Because pneumococcal pneumonia was prevalent during previous influenza pandemics, we evaluated invasive pneumococcal pneumonia (IPP) rates during the 2009 influenza A(H1N1) pandemic. METHODS: We identified laboratory-confirmed, influenza-associated hospitalizations and IPP cases (pneumococcus isolated from normally sterile sites with discharge diagnoses of pneumonia) using active, population-based surveillance in the United States. We compared IPP rates during peak pandemic months (April 2009-March 2010) to mean IPP rates in nonpandemic years (April 2004-March 2009) and, using Poisson models, to 2006-2008 influenza seasons. RESULTS: Higher IPP rates occurred during the peak pandemic month compared to nonpandemic periods in 5-24 (IPP rate per 10 million: 48 vs 9 (95% confidence interval [CI], 5-13), 25-49 (74 vs 53 [CI, 41-65]), 50-64 (188 vs 114 [CI, 85-143]), and ≥65-year-olds (229 vs 187 [CI, 159-216]). In the models with seasonal influenza rates included, observed IPP rates during the pandemic peak were within the predicted 95% CIs, suggesting this increase was not greater than observed with seasonal influenza. CONCLUSIONS: The recent influenza pandemic likely resulted in an out-of-season IPP peak among persons ≥5 years. The IPP peak's magnitude was similar to that seen during seasonal influenza epidemics.

Effectiveness of nonadjuvanted monovalent influenza A(H1N1)pdm09 vaccines for preventing reverse transcription polymerase chain reaction-confirmed pandemic influenza hospitalizations: case-control study of children and adults at 10 US influenza surveillance network sites.

During 2009-2010, we examined 217 patients hospitalized with laboratory-confirmed pandemic influenza in 9 Influenza Hospitalization Surveillance Network sites and 413 age- and community-matched controls and found that a single dose of monovalent nonadjuvanted influenza A(H1N1)pdm09 vaccine was 50% (95% confidence interval, 13%-71%) effective in preventing hospitalization associated with A(H1N1)pdm09 virus infection.

Increase in rates of hospitalization due to laboratory-confirmed influenza among children and adults during the 2009-10 influenza pandemic.

BACKGROUND: The Emerging Infections Programs (EIP) network has conducted population-based surveillance for hospitalizations due to laboratory-confirmed influenza among children since 2003, with the network expanding in 2005 to include adults. METHODS: From 15 April 2009 through 30 April 2010, the EIP conducted surveillance among 22.1 million people residing in 10 states. Incidence rates per 100 000 population were calculated using US Census Bureau data. Mean historic rates were calculated on the basis of previously published and unpublished EIP data. RESULTS: During the 2009 pandemic of influenza A virus subtype H1N1 infection, rates of hospitalizations due to laboratory-confirmed influenza were 202, 88, 49, 31, 27, 36, 28, and 27 episodes per 100 000 among persons aged <6 months, 6-23 months, 2-4 years, 5-17 years, 18-49 years, 50-64 years, 65-74 years, and ≥75 years, respectively. Comparative mean rates from previous influenza seasons during which EIP conducted surveillance were 153, 53, 20, 6, 4, 8, 20, and 56 episodes per 100 000 among persons aged <6 months, 6-23 months, 2-4 years, 5-17 years, 18-49 years, 50-64 years, 65-74 years, and ≥75 years, respectively. CONCLUSIONS: During the pandemic, rates of hospitalization due to laboratory-confirmed influenza among individuals aged 5-17 years and 18-49 years increased 5-fold and 6-fold, respectively, compared with mean rates from previous influenza seasons. Hospitalization rates for other pediatric and adult age groups increased, compared with mean rates from previous influenza seasons, whereas the rate among individuals aged ≥75 years decreased.

Reduced influenza antiviral treatment among children and adults hospitalized with laboratory-confirmed influenza infection in the year after the 2009 pandemic.

Influenza antiviral treatment is recommended for all persons hospitalized with influenza virus infection. During the 2010-2011 influenza season, antiviral treatment of children and adults hospitalized with laboratory-confirmed influenza declined significantly compared with treatment during the 2009 pandemic (children, 56% vs 77%; adults, 77% vs 82%; both P < .01).

Description of antiviral treatment among adults hospitalized with influenza before and during the 2009 pandemic: United States, 2005-2009.

BACKGROUND: The 2009 influenza pandemic led to guidelines emphasizing antiviral treatment for all persons hospitalized with influenza, including pregnant women. We compared antiviral use among adults hospitalized with influenza before and during the pandemic. METHODS: The Emerging Infections Program conducts active population-based surveillance for persons hospitalized with community-acquired, laboratory-confirmed influenza in 10 states. We analyzed data collected via medical record review of patients aged ≥18 years admitted during prepandemic (1 October 2005 through 14 April 2009) and pandemic (15 April 2009 through 31 December 2009) time frames. RESULTS: Of 5943 adults hospitalized with influenza in prepandemic seasons, 3235 (54%) received antiviral treatment, compared with 4055 (82%) of 4966 during the pandemic. Forty-one (22%) of 187 pregnant women received antiviral treatment in prepandemic seasons, compared with 369 (86%) of 430 during the pandemic. Pregnancy was a negative predictor of antiviral treatment before the pandemic (adjusted odds ratio [aOR], 0.24; 95% confidence interval [CI], .16-.35) but was independently associated with treatment during the pandemic (aOR, 1.97; 95% CI, 1.32-2.96). Antiviral treatment among adults hospitalized >2 days after illness onset increased from 43% before the pandemic to 79% during the pandemic (P < .001). CONCLUSIONS: Antiviral treatment of hospitalized adults increased during the pandemic, especially among pregnant women. This suggests that many clinicians followed published guidance to treat hospitalized adults with antiviral agents. However, compliance with antiviral recommendations could be improved.

Risk factors for 2009 pandemic influenza A (H1N1)-related hospitalization and death among racial/ethnic groups in New Mexico.

OBJECTIVES: We assessed risk factors for 2009 pandemic influenza A (H1N1)-related hospitalization, mechanical ventilation, and death among New Mexico residents. METHODS: We calculated population rate ratios using Poisson regression to analyze risk factors for H1N1-related hospitalization. We performed a cross-sectional analysis of hospitalizations during September 14, 2009 through January 13, 2010, using logistic regression to assess risk factors for mechanical ventilation and death among those hospitalized. RESULTS: During the study period, 926 laboratory-confirmed H1N1-related hospitalizations were identified. H1N1-related hospitalization was significantly higher among American Indians (risk ratio [RR] = 2.6; 95% confidence interval [CI] = 2.2, 3.2), Blacks (RR = 1.7; 95% CI = 1.2, 2.4), and Hispanics (RR = 1.8; 95% CI = 1.5, 2.0) than it was among non-Hispanic Whites, and also was higher among persons of younger age and lower household income. Mechanical ventilation was significantly associated with age 25 years and older, obesity, and lack of or delayed antiviral treatment. Death was significantly associated with male gender, cancer during the previous 12 months, and liver disorder. CONCLUSIONS: This analysis supports recent national efforts to include American Indian/Alaska Native race as a group at high risk for complications of influenza with respect to vaccination and antiviral treatment recommendations.

Adult hospitalizations for laboratory-positive influenza during the 2005-2006 through 2007-2008 seasons in the United States.

BACKGROUND: Rates of influenza-associated hospitalizations in the United States have been estimated using modeling techniques with data from pneumonia and influenza hospitalization discharge diagnoses, but they have not been directly estimated from laboratory-positive cases. METHODS: We calculated overall, age-specific, and site-specific rates of laboratory-positive, influenza-associated hospitalization among adults and compared demographic and clinical characteristics and outcomes of hospitalized cases by season with use of data collected by the Emerging Infections Program Network during the 2005-2006 through 2007-2008 influenza seasons. RESULTS: Overall rates of adult influenza-associated hospitalization per 100,000 persons were 9.9 during the 2005-2006 season, 4.8 during the 2006-2007 season, and 18.7 during the 2007-2008 season. Rates of hospitalization varied by Emerging Infections Program site and increased with increasing age. Higher overall and age-specific rates of hospitalization were observed during influenza A (H3) predominant seasons and during periods of increased circulation of influenza B. More than 80% of hospitalized persons each season had > or =1 underlying medical condition, including chronic cardiovascular and metabolic diseases. CONCLUSIONS: Rates varied by season, age, geographic location, and type/subtype of circulating influenza viruses. Influenza-associated hospitalization surveillance is essential for assessing the relative severity of influenza seasons over time and the burden of influenza-associated complications.

Comprehensive assessment of sociodemographic and behavioral risk factors for Mycoplasma genitalium infection in women.

BACKGROUND: Neisseria gonorrhoeae and Chlamydia trachomatis are characterized by different risk factors, thus control strategies for each also differ. In contrast, risk factors for Mycoplasma genitalium have not been well characterized. METHODS: Between 2000 and 2006, 1090 women ages 14 to 45 attending the Public Health-Seattle & King County Sexually Transmitted Diseases Clinic in Seattle, WA, underwent clinical examination and computer-assisted survey interview. M. genitalium was detected by transcription mediated amplification from self-obtained vaginal swab specimens. C. trachomatis and N. gonorrhoeae were detected by culture from cervical swab specimens. RESULTS: Prevalent M. genitalium infection was detected in 84 women (7.7%), C. trachomatis in 63 (5.8%), and N. gonorrhoeae in 26 (2.4%). Age <20 and nonwhite race were associated with increased risk for all 3 organisms. In addition, risk for M. genitalium was higher for women with a black partner (adjusted odds ratio [AOR]: 3.4; 95% confidence interval = 1.83-6.29), those never married (AOR: 2.6; 1.08-6.25), using Depo-Provera (AOR: 2.3; 1.19-4.46), and smoking (AOR: 1.7; 1.03-2.83). Drug use, history of STI in the past year, ≤high school education, meeting and having intercourse the same day, anal sex, douching, and hormonal contraception were associated with N. gonorrhoeae or C. trachomatis, but not with M. genitalium. Number of partners was not associated with any of the 3 organisms. CONCLUSIONS: The limited number of risk factors for prevalent infection common to all 3 pathogens suggests that M. genitalium may circulate in different sexual networks than N. gonorrhoeae or C. trachomatis. The predominance of sociodemographic risk factors for M. genitalium, rather than high-risk sexual behaviors, suggests broad-based testing may be the most effective control strategy.

Psychometric limitations of the RBANS effort index in forensic inpatient populations.

Although the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) is a widely studied and utilized screening measure with an Effort Index (EI), there is a minimal amount of data available regarding the utility of the EI for forensic inpatients. Specific concerns include the possibility that the published cutoffs would result in high false positive rates. The present study investigated this issue by comparing the validity of the RBANS EI with that of the Dot Counting Test (DCT) and Test of Memory Malingering (TOMM) in a forensic psychiatric setting (N = 117). Analyses indicated a positive association between RBANS EI categorizations (invalid or genuine responding) and the classifications made by the DCT and the TOMM. However, the false positive rate for the RBANS EI was found to be excessively high (17.95%), while the positive predictive value was below chance (44.74%). Additional psychometric properties for the RBANS EI in this population are reported in the article, including findings from a Receiver Operating Characteristic (ROC) analysis. Overall, the results suggest that caution is warranted, when utilizing the RBANS EI as a validity measure within a forensic inpatient psychiatric setting and more appropriate cutoffs are needed for this population.

Risk Factors for Community-Associated Clostridium difficile Infection in Adults: A Case-Control Study.

BACKGROUND: An increasing proportion of Clostridium difficile infections (CDI) in the United States are community-associated (CA). We conducted a case-control study to identify CA-CDI risk factors. METHODS: We enrolled participants from 10 US sites during October 2014-March 2015. Case patients were defined as persons age ≥18 years with a positive C. difficile specimen collected as an outpatient or within 3 days of hospitalization who had no admission to a health care facility in the prior 12 weeks and no prior CDI diagnosis. Each case patient was matched to one control (persons without CDI). Participants were interviewed about relevant exposures; multivariate conditional logistic regression was performed. RESULTS: Of 226 pairs, 70.4% were female and 52.2% were ≥60 years old. More case patients than controls had prior outpatient health care (82.1% vs 57.9%; P < .0001) and antibiotic (62.2% vs 10.3%; P < .0001) exposures. In multivariate analysis, antibiotic exposure-that is, cephalosporin (adjusted matched odds ratio [AmOR], 19.02; 95% CI, 1.13-321.39), clindamycin (AmOR, 35.31; 95% CI, 4.01-311.14), fluoroquinolone (AmOR, 30.71; 95% CI, 2.77-340.05) and beta-lactam and/or beta-lactamase inhibitor combination (AmOR, 9.87; 95% CI, 2.76-340.05),-emergency department visit (AmOR, 17.37; 95% CI, 1.99-151.22), white race (AmOR 7.67; 95% CI, 2.34-25.20), cardiac disease (AmOR, 4.87; 95% CI, 1.20-19.80), chronic kidney disease (AmOR, 12.12; 95% CI, 1.24-118.89), and inflammatory bowel disease (AmOR, 5.13; 95% CI, 1.27-20.79) were associated with CA-CDI. CONCLUSIONS: Antibiotics remain an important risk factor for CA-CDI, underscoring the importance of appropriate outpatient prescribing. Emergency departments might be an environmental source of CDI; further investigation of their contribution to CDI transmission is needed.