Background: Clinical antibiotic susceptibility testing (AST) interpretations based on minimum inhibitory concentrations (MIC) breakpoints are important for both clinical decision making and some reportable condition criteria. Standardization of MIC breakpoints across clinical laboratories is lacking; AST instruments are often validated for outdated Clinical and Laboratory Standards Institute (CLSI) MIC breakpoint guidelines. In this study, we analyzed the agreement between the reported clinical laboratory AST interpretations and the guideline CLSI interpretation. Methods: Clinical laboratory AST data collected from the Multisite Gram-Negative Surveillance Initiative (MuGSI) carbapenem-resistant Enterobacterales (CRE) surveillance program in Tennessee between 2019 and 2021 were utilized. MIC values from the clinical instrument were used to calculate CLSI standard interpretations following the 2019–2021 CLSI M100 guidelines. Agreement between the clinical laboratory and CLSI interpretations of the reported MIC values were measured using a weighted Cohen κ calculated in SAS version 9.4 software. Total matches were isolates with identical CLSI and clinical laboratory interpretations. Results: In total, 14 antibiotics were assessed. Of those, 9 antibiotics had at least moderate agreement (κ > 0.41) between interpretations. Agreement between the clinical laboratory and the CLSI interpretations were near perfect (κ > 0.81) for 3 antibiotics. Agreement between the clinical laboratory and the CLSI interpretations were poor for cefazolin (0.06) and ertapenem (0.14). Cefotaxime (−0.07) was the only antibiotic that suggested no agreement. Conclusions: Of the antibiotics included in the analysis, 36% had less than moderate agreement between clinical laboratory and CLSI AST interpretations. Given the increases in antimicrobial resistance globally and the emphasis placed on antibiotic stewardship, standardization across clinical AST panels should be prioritized. Inconsistencies have the potential to contribute to inappropriate antibiotic use in addition to under- or overidentification of reportable conditions, including CRE.

Disclosures: None

Background: The NHSN Antibiotic Resistance (AR) Option can serve as a useful tool for tracking antibiotic-resistant infections and can aid in the development of inpatient antibiograms. We recently described the frequency of antibiotic suppression in NHSN AR Option data. In this analysis, we describe the effects of suppression on practical uses of the NHSN AR Option, specifically selected agent antibiogram development, and detection of reportable conditions. Methods: Antibiotic susceptibility data were collected from the NHSN AR Option and commercial automated antimicrobial susceptibility testing instruments (cASTI) from 3 hospital networks. Data were obtained from January 1, 2017, to December 31, 2018. The clinical susceptibility data for third-generation cephalosporins and carbapenems against carbapenem-resistant Enterobacterales (CRE), Pseudomonas aeruginosa, and Acinetobacter baumannii were included. Susceptibility results were defined as suppressed when susceptibility results were observed from the laboratory instrument but not from NHSN data. For the overall percentage susceptibility estimation, isolates with <30 susceptibility results were excluded. Percentage susceptibility of NHSN results were compared to their counterparts from cASTI. Results: Of the 852 matched isolates in the primary analysis, 804 had at least 1 suppressed result. Of the 804 isolates, 16.9% were P. aeruginosa, 67.3% by E. coli, and 11.1% by Klebsiella spp. The following pathogen–drug combinations had no difference observed in the percentage susceptible between the 2 systems: ceftazidime tested against P. aeruginosa, ceftriaxone tested against Klebsiella spp, ertapenem tested against Klebsiella spp, imipenem tested against E. coli and P. aeruginosa, and meropenem tested against P. aeruginosa. Significant differences were observed for the following drugs tested against E. coli: ceftazidime (11.1%), cefotaxime (8.6%), and ceftriaxone (8.3%). In the NHSN AR Option, the following isolates showed suppressed results related to their phenotypic case definition: 17 (3%) CRE isolates, 7 (28%) carbapenem-resistant Acinetobacter baumannii (CRAB) isolates, 511 (93.2%) extended spectrum β-lactamase (ESBL) isolates, and 94 (66.7%) carbapenem-resistant Pseudomonas aeruginosa (CRPA) isolates. Conclusions: For select isolates, notably E. coli, we observed a large difference in the percentage of susceptible isolates reported into the NHSN AR Option compared to the cASTI data. This difference significantly limits the ability of the AR Option to create valid antibiograms for select pathogen–drug combinations. Moreover, significant numbers of CRAB, ESBL, and CRPA isolates would not be identified from NHSN AR Option because of suppression. This finding warrants the need for antimicrobial stewardship teams to regularly assess the impact of selective reporting in identifying pathogens of public health importance.

Funding: None

Disclosures: None

Background: On March 5, 2020, the Tennessee Department of Health (TDH) announced the first case of COVID-19 in the state. Since then, hospitals have been overwhelmed by the spike in respiratory infections. Several studies have attempted to describe the impact of the pandemic on antibiotic prescriptions. The NHSN Antimicrobial Use Option offers a platform for hospitals to report their antibiotic usage. The TDH has established access to hospital antibiotic usage data statewide through an existing NHSN user group. We compared the change in the volume of inpatient antibiotic prescriptions before and during the pandemic. Methods: An ecological study was conducted from January 2019 to December 2021. Aggregated facility-level data from the NHSN Antimicrobial Use Option were used to describe antibacterial use among Tennessee hospitals. Data from facilities that had reported at least 1 month of data during the study period were included in this study. The antimicrobial use rate was calculated by dividing the antimicrobial days of therapy (DOT) by the number of 1,000 days present. Overall antimicrobial use rates as well as specific antimicrobial use rates for azithromycin, ceftriaxone, and piperacillin–tazobactam were compared across years. Results: In total, 55 hospitals reported at least 1 month of data into the NHSN Antimicrobial Use Option during the study period. These hospitals had a median bed size of 140 (range, 12–689). Conclusions: We observed a modest increase in overall antibiotic use during the COVID-19 pandemic in Tennessee facilities. This trend appeared to be primarily attributed to agents used for community-acquired respiratory infections, such as azithromycin and ceftriaxone, earlier in the pandemic. However, both of these agents have fallen to prepandemic use levels during 2021. The fact that overall use increased in 2021 suggests that other agents not analyzed may have contributed to this effect. Further analysis may help determine which agents are responsible for this increase in 2021.

Funding: None

Disclosures: None

Background: Carbapenem-resistant Acinetobacter baumannii (CRAB) is an important cause of healthcare-associated infections with limited treatment options and high mortality. To describe risk factors for mortality, we evaluated characteristics associated with 30-day mortality in patients with CRAB identified through the Emerging Infections Program (EIP). Methods: From January 2012 through December 2017, 8 EIP sites (CO, GA, MD, MN, NM, NY, OR, TN) participated in active, laboratory-, and population-based surveillance for CRAB. An incident case was defined as patient’s first isolation in a 30-day period of A. baumannii complex from sterile sites or urine with resistance to ≥1 carbapenem (excluding ertapenem). Medical records were abstracted. Patients were matched to state vital records to assess mortality within 30 days of incident culture collection. We developed 2 multivariable logistic regression models (1 for sterile site cases and 1 for urine cases) to evaluate characteristics associated with 30-day mortality. Results: We identified 744 patients contributing 863 cases, of which 185 of 863 cases (21.4%) died within 30 days of culture, including 113 of 257 cases (44.0%) isolated from a sterile site and 72 of 606 cases (11.9%) isolated from urine. Among 628 hospitalized cases, death occurred in 159 cases (25.3%). Among hospitalized fatal cases, death occurred after hospital discharge in 27 of 57 urine cases (47.4%) and 21 of 102 cases from sterile sites (20.6%). Among sterile site cases, female sex, intensive care unit (ICU) stay after culture, location in a healthcare facility, including a long-term care facility (LTCF), 3 days before culture, and diagnosis of septic shock were associated with increased odds of death in the model (Fig. 1). In urine cases, age 40–54 or ≥75 years, ICU stay after culture, presence of an indwelling device other than a urinary catheter or central line (eg, endotracheal tube), location in a LTCF 3 days before culture, diagnosis of septic shock, and Charlson comorbidity score ≥3 were associated with increased odds of mortality (Fig. 2). Conclusion: Overall 30-day mortality was high among patients with CRAB, including patients with CRAB isolated from urine. A substantial fraction of mortality occurred after discharge, especially among patients with urine cases. Although there were some differences in characteristics associated with mortality in patients with CRAB isolated from sterile sites versus urine, LTCF exposure and severe illness were associated with mortality in both patient groups. CRAB was associated with major mortality in these patients with evidence of healthcare experience and complex illness. More work is needed to determine whether prevention of CRAB infections would improve outcomes.

Funding: None

Disclosures: None

Background: Automated testing instruments (ATIs) are commonly used by clinical microbiology laboratories to perform antimicrobial susceptibility testing (AST), whereas public health laboratories may use established reference methods such as broth microdilution (BMD). We investigated discrepancies in carbapenem minimum inhibitory concentrations (MICs) among Enterobacteriaceae tested by clinical laboratory ATIs and by reference BMD at the CDC. Methods: During 2016–2018, we conducted laboratory- and population-based surveillance for carbapenem-resistant Enterobacteriaceae (CRE) through the CDC Emerging Infections Program (EIP) sites (10 sites by 2018). We defined an incident case as the first isolation of Enterobacter spp (E. cloacae complex or E. aerogenes), Escherichia coli, Klebsiella pneumoniae, K. oxytoca, or K. variicola resistant to doripenem, ertapenem, imipenem, or meropenem from normally sterile sites or urine identified from a resident of the EIP catchment area in a 30-day period. Cases had isolates that were determined to be carbapenem-resistant by clinical laboratory ATI MICs (MicroScan, BD Phoenix, or VITEK 2) or by other methods, using current Clinical and Laboratory Standards Institute (CLSI) criteria. A convenience sample of these isolates was tested by reference BMD at the CDC according to CLSI guidelines. Results: Overall, 1,787 isolates from 112 clinical laboratories were tested by BMD at the CDC. Of these, clinical laboratory ATI MIC results were available for 1,638 (91.7%); 855 (52.2%) from 71 clinical laboratories did not confirm as CRE at the CDC. Nonconfirming isolates were tested on either a MicroScan (235 of 462; 50.9%), BD Phoenix (249 of 411; 60.6%), or VITEK 2 (371 of 765; 48.5%). Lack of confirmation was most common among E. coli (62.2% of E. coli isolates tested) and Enterobacter spp (61.4% of Enterobacter isolates tested) (Fig. 1A), and among isolates testing resistant to ertapenem by the clinical laboratory ATI (52.1%, Fig. 1B). Of the 1,388 isolates resistant to ertapenem in the clinical laboratory, 1,006 (72.5%) were resistant only to ertapenem. Of the 855 nonconfirming isolates, 638 (74.6%) were resistant only to ertapenem based on clinical laboratory ATI MICs. Conclusions: Nonconfirming isolates were widespread across laboratories and ATIs. Lack of confirmation was most common among E. coli and Enterobacter spp. Among nonconfirming isolates, most were resistant only to ertapenem. These findings may suggest that ATIs overcall resistance to ertapenem or that isolate transport and storage conditions affect ertapenem resistance. Further investigation into this lack of confirmation is needed, and CRE case identification in public health surveillance may need to account for this phenomenon.

Funding: None

Disclosures: None

Background: Carbapenem-resistant Enterobacteriaceae (CRE) are a major public health problem. Ceftazidime-avibactam (CZA) is a treatment option for CRE approved in 2015; however, it does not have activity against isolates with metallo-β-lactamases (MBLs). Emerging resistance to CZA is a cause for concern. Our objective was to describe the microbiologic and epidemiologic characteristics of CZA-resistant (CZA-R) CRE. Methods: From 2015 to 2017, 9 states participated in laboratory- and population-based surveillance for carbapenem-resistant Escherichia coli, Klebsiella pneumoniae, K. oxytoca, K. aerogenes, and Enterobacter cloacae complex isolates from a normally sterile site or urine. A convenience sample of isolates from this surveillance were sent to the CDC for antimicrobial susceptibility testing (AST) using reference broth microdilution (BMD) including an MBL screen, species confirmation with MALDI-TOF, and real-time PCR to detect blaKPC, blaNDM, and blaOXA-48–like genes. Additional AST by BMD was performed on CZA-R isolates using meropenem-vaborbactam (MEV), imipenem-relebactam (IMR), plazomicin (PLZ), and eravacycline (ERV). Epidemiologic data were obtained from a medical record review. Community-associated cases were defined as having no healthcare exposures in the year prior to culture, no devices in place 2 days prior to culture, and culture collected before calendar day 3 after hospital admission. Data were analyzed in 3 groups: CRE that were CZA-susceptible (CZA-S), CZA-R that were due to blaNDM, and CZA-R without blaNDM. Results: Among 606 confirmed CRE tested with CZA, 33 (5.4%) were CZA-R. Of the CZA-R isolates, 16 (48.5%) harbored a blaNDM gene, of which 2 coharbored blaNDM and blaOXA-48-like genes; 9 (27.3%) harbored only a blaKPC gene. Of the 17 CZA-R isolates without blaNDM, all were MBL screen negative. CZA-R due to blaNDM were more frequently community-associated (43.8%) than CZA-S or CZA-R without blaNDM (11.0% and 5.9%, respectively); a higher percentage of CZA-R cases due to blaNDM also had recent international travel (25%) compared to the other groups (1.8% and 5.9%, respectively). CZA-R without blaNDM were more susceptible to MEV (76%), IMR (71%), PLZ (88%), and ERV (65%) compared to CZA-R due to blaNDM (19%, 6%, 56%, and 44%, respectively). Conclusions: The emergence of CZA-R isolates without blaNDM are concerning; however, these isolates are more susceptible to newer antimicrobials than those with blaNDM. In addition to high rates of resistance to newer antimicrobials, isolates with blaNDM are more frequently community-associated than other CRE. This underscores the need for more aggressive measures to stop the spread of CRE.

Funding: None

Disclosures: None

Background: The National Healthcare Safety Network’s (NHSN) Antibiotic Resistance (AR) Option offers hospitals a way to report antibiotic resistance data from their facility’s laboratory information system and create facility-specific antibiograms. Suppression of select antibiotic susceptibility results may be used by antibiotic stewardship teams to prevent unnecessary use of broad-spectrum therapies by not making those susceptibilities available to providers. To be of use, antibiograms should offer a complete picture of antibiotic resistance. We wanted to understand the impact of data suppression. Methods: A retrospective cross-sectional study was conducted including data from 2017 and 2018. The clinical susceptibility data for cefotaxime, ceftriaxone, ceftazidime, ertapenem, imipenem, and meropenem against carbapenem-resistant Enterobacteriaceae (CRE), Pseudomonas aeruginosa (CRPA), Acinetobacter baumannii (CRAB), and extended-spectrum β-lactamase–producing Enterobacteriaceae (ESBL) were collected from commercial antimicrobial susceptibility testing instruments (cASTI) in 3 Tennessee healthcare networks that also report to the NHSN AR Option. These data were linked to the NHSN data using 4 keys: date of birth, isolate collection date, pathogen, and specimen source. An isolate was defined as suppressed when susceptibility results were observed from the cASTI but not in NHSN. The proportions of suppressed results were calculated and stratified by genus, facility, and antibiotic. Results: Overall, 1,009 isolates were matched between the NHSN AR data and the laboratory test results. Of these, 4.1% were CRAB, 23.3% were CRPA, and 72.6% were Enterobacteriaceae. In total, 4,948 susceptibility results were available from cASTIs. Suppressed results in NHSN data were observed in 918 isolates (91.0%) and accounted for 2,797 results (56.6%). Of the 817 isolates tested against imipenem, 18.7% were found to be suppressed. Moreover, 100%, 57.9%, and 8.6% of imipenem tests against CRAB, CRPA, and Enterobacteriaceae, respectively, were suppressed. Of the suppressed results, 38.3%, 3.6%, and 58.1% were susceptible, intermediate, and resistant respectively. Of the 363 isolates tested against meropenem, 48.2% were found to be suppressed. In addition, 12.2%, 53.0%, and 52.2% of meropenem tests against CRAB, CRPA, and Enterobacteriaceae, respectively, were suppressed. Of the suppressed results, 47.4%, 11.4%, and 41.1% were susceptible, intermediate, and resistant, respectively. Conclusions: A large proportion of isolates had at least 1 analyzed antibiotic suppressed within the NHSN AR Option. It will be important to develop and implement strategies to ensure that nonsuppressed data are available to be reported to the NHSN AR module.

Funding: None

Disclosures: None

Background: Extended-spectrum β-lactamase–producing (ESBL) Escherichia coli infection incidence is increasing in the United States. This increase may be due to the rapid expansion of ST131, which is now the predominant ESBL strain globally, often multidrug resistant, and has been shown to establish longer-term human colonization than other E. coli strains. We assessed potential risk factors that distinguish ST131 from other ESBL E. coli. Methods: From October 1 through December 31, 2017, 5 CDC Emerging Infections Program (EIP) sites pilot tested active, laboratory-based surveillance in selected counties in Colorado, Georgia, New Mexico, New York, and Tennessee. An E. coli case was defined as the first isolation from a normally sterile body site or urine in a surveillance area resident in a 30-day period resistant to 1 extended-spectrum cephalosporin antibiotic and susceptible or intermediate to all carbapenem antibiotics tested. Epidemiologic data were collected from case patients’ medical records. A convenience sample of 117 E. coli isolates from case patients was collected. All isolates underwent whole-genome sequencing to determine sequence type and the presence of ESBL genes. We compared ST131 E. coli epidemiology to other ESBL E. coli. Results: Among 117 E. coli isolates, 97 (83%) were ESBL producers. Of the 97 ESBL E. coli, 52 (54%) were ST131 (range, for 4 EIP sites submitting >10 isolates: 25%–88%; P < .001). Other common STs were ST38 (12%) and ST10 (5%). ST131 infections were more likely to be healthcare-associated than non-ST131 (56% vs 36%; P = .05) (Table 1). Among specific prior healthcare exposures, only residence in long-term care facilities (LTCFs) in the year before culture was more common among ST131 case patients (29% vs 11%; P = .03). Notably, 85% of ESBL E. coli collected from LTCF residents were ST131. ST131 E. coli were more common among patients with underlying medical conditions (81% vs 60%; P = .02). No statistically significant difference by sex, race, age, culture source, location of culture collection, and frequency of antibiotic use in the prior 30 days was observed. Conclusions:The prevalence of ST131 E. coli varies regionally. The association between ST131 and LTCFs suggests that these may be particularly important settings for ST131 acquisition. Improving infection control measures that limit ESBL transmission in these settings and preventing dissemination in facilities receiving patients from LTCFs may be necessary to contain ST131 spread.

Funding: None

Disclosures: None

Background: Carbapenem-resistant Acinetobacter baumannii (CRAB) is a serious threat to patient safety due to limited treatment options and propensity to spread in healthcare settings. Using Emerging Infections Program (EIP) data, we describe changes in CRAB incidence and epidemiology. Methods: During January 2012 to December 2018, 9 sites (Colorado, Connecticut, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon, and Tennessee) participated in active laboratory- and population-based surveillance. An incident case was defined as the first isolation of A. baumannii complex, in a 30-day period, resistant to ≥1 carbapenem (excluding ertapenem) from a normally sterile site or urine of a surveillance area resident. Cases were considered hospital-onset (HO) if the culture was collected >3 days after hospital admission; all others were community-onset (CO). Cases were classified as device-associated (DA) if the patient had 1 or more medical devices (ie, urinary catheter, central venous catheter (CVC), endotracheal/nasotracheal tube, tracheostomy, or another indwelling device) present in the 2 days prior to culture collection. Temporal trends were estimated using generalized linear models adjusted for age, race, sex, and EIP site. Results: Overall, 984 incident CRAB cases were identified, representing 849 patients. Among these patients, 291 (34%) were women, 510 (61%) were nonwhite, and the median age was 62 years (mean, 59; range, 0–102). Among the cases, 226 (23%) were HO; 758 (77%) were CO; and 793 (81%) were DA. Overall incidence rates in 2012 and 2018 were 1.58 (95% CI, 1.29–1.90) and 0.60 (95% CI, 0.40–0.67) per 100,000 population, respectively. There was a 15% annual decrease in incidence (adjusted rate ratio [aRR] 0.85; 95% CI: 0.82-0.88, P < .0001). Decreases were observed among sterile site (aRR 0.88; 95% CI, 0.84–0.93) and urine cases (aRR 0.83; 95% CI, 0.80–0.87). Annual decreases occurred for HO cases (aRR, 0.78; 95% CI, 0.73–0.85) and CO cases (aRR, 0.86; 95% CI, 0.83–0.9). The DA cases decreased 16% annually overall (aRR, 0.84; 95% CI, 0.81–0.88). Decreases among cases in patients with CVC (aRR, 0.85; 95% CI, 0.80–0.90) and urinary catheters (aRR, 0.84; 95% CI, 0.80–0.88) were smaller than what was seen in patients with other indwelling devices (aRR, 0.81; 95% CI, 0.77–0.86). Discussion: Overall, from 2012 to 2018, the incidence of CRAB decreased >60%. Decreases were observed in all case groups, regardless of source, infection onset location, or types of devices. Smaller annual decreases in rates of CO-CRAB than HO-CRAB suggest that there may be opportunities to accelerate prevention outside the hospital to further reduce the incidence of these difficult-to-treat infections.

Funding: None

Disclosures: None

Background: Extended-spectrum β-lactamase–producing Enterobacteriaceae (ESBL-Ent) have emerged as a significant antimicrobial-resistance threat in the community in recent years. To better characterize ESBL-Ent in the community, we examined associations between community-associated ESBL-Ent incidence rates and area-based socioeconomic status (SES) characteristics. Methods: Cases were identified through active, laboratory- and population-based surveillance for ESBL-Ent in 3 Emerging Infections Program (EIP) sites (New Mexico, New York, and Tennessee) from October through December 2017. We defined a case as first isolation of Escherichia coli, Klebsiella pneumoniae, or K. oxytoca from a normally sterile body specimen or urine in a surveillance-site resident, with resistance to ≥1 extended-spectrum cephalosporin and nonresistance to all carbapenems tested. Epidemiologic data were abstracted from medical records. Cases were considered community associated if no significant prior healthcare exposures (ie, inpatient healthcare facility stay, surgery, chronic dialysis, indwelling devices, or external catheters) were documented. Case residential addresses were geocoded and linked to US Census Bureau data to obtain census-tract level SES measures. Census tracts were dichotomized by the percentage living in rural areas (0–49% or ≥50%); census tracts were stratified into quartiles for all other characteristics. Incidence rate ratios (IRR) for each measure, controlling for EIP site, were calculated using Poisson regression. Results: Among 742 ESBL-Ent cases with medical records available, 355 (47.1%) were community associated; of these, 327 case addresses (92.1%) were successfully geocoded. The combined annualized 2017 incidence rate for community-associated ESBL-Ent was 83.2 cases per 100,000 persons. The highest incidence of community-associated ESBL-Ent was seen in census tracts with the lowest median income (IRR, 1.4; 95% CI, 1.0–2.0) and with the highest percentages of persons without health insurance (IRR, 1.3; 95% CI, 1.0–1.7), with <12th-grade education (IRR, 1.5; 95% CI, 1.1–2.1), living in urban areas (IRR, 1.5; 95% CI, 1.0–2.2), foreign-born (IRR, 1.4; 95% CI, 1.0–2.0), or speaking limited English (IRR, 1.5; 95% CI, 1.1–2.0). There were no significant differences across quartiles for population density, income inequality, the percentage of the population living below poverty, or the percentage of households with crowding (>1 occupant or room). Conclusions: Social determinants of health, such as coverage for healthcare, appear to be important contributors to community-associated ESBL-Ent transmission. Higher rates in areas with more foreign-born persons and persons with limited English proficiency suggest a role for recent travel in importation and spread in specific communities. These findings provide additional information about the epidemiology of ESBL-Ent in the community and have potential implications for control efforts.

Funding: None

Disclosures: None