Implementation of contact precautions for multidrug-resistant organisms in the post-COVID-19 pandemic era: An updated national Emerging Infections Network (EIN) survey.

OBJECTIVE: To understand how healthcare facilities employ contact precautions for patients with multidrug-resistant organisms (MDROs) in the post-coronavirus disease 2019 (COVID-19) era and explore changes since 2014. DESIGN: Cross-sectional survey. PARTICIPANTS: Emerging Infections Network (EIN) physicians involved in infection prevention or hospital epidemiology. METHODS: In September 2022, we sent via email an 8-question survey on contact precautions and adjunctive measures to reduce MDRO transmission in inpatient facilities. We also asked about changes since the COVID-19 pandemic. We used descriptive statistics to summarize data and compared results to a similar survey administered in 2014. RESULTS: Of 708 EIN members, 283 (40%) responded to the survey and 201 reported working in infection prevention. A majority of facilities (66% and 69%) routinely use contact precautions for methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) respectively, compared to 93% and 92% in 2014. Nearly all (>90%) use contact precautions for Candida auris, carbapenem-resistant Enterobacterales (CRE), and carbapenem-resistant Acinetobacter baumannii. More variability was reported for carbapenem-resistant Pseudomonas aeruginosa and extended-spectrum ß-lactamase-producing gram-negative organisms. Compared to 2014, fewer hospitals perform active surveillance for MRSA and VRE. Overall, 90% of facilities used chlorhexidine gluconate bathing in all or select inpatients, and 53% used ultraviolet light or hydrogen peroxide vapor disinfection at discharge. Many respondents (44%) reported changes to contact precautions since COVID-19 that remain in place. CONCLUSIONS: Heterogeneity exists in the use of transmission-based precautions and adjunctive infection prevention measures aimed at reducing MDRO transmission. This variation reflects a need for updated and specific guidance, as well as further research on the use of contact precautions in healthcare facilities.

Nosocomial infections by diverse carbapenemase-producing Aeromonas hydrophila associated with combination of plumbing issues and heat waves.

BACKGROUND: Aquatic opportunistic pathogen Aeromonas hydrophila, known to persist in low-nutrient chlorinated waters, can cause life-threatening infections. Two intensive care units experienced a cluster of Aeromonas infections following outdoor temperature spikes coinciding with recurrent plumbing issues, with fatalities due to severe underlying comorbidities co-occurring with extensively-drug resistant (XDR) Aeromonas. METHODS: We investigated this cluster using whole genome sequencing to assess genetic relatedness of isolates and identify antimicrobial resistance determinants. Three A. hydrophila were isolated from patients staying in or adjacent to rooms with plumbing issues during or immediately after periods of elevated outdoor temperatures. Sinks and faucets were swabbed for culture. RESULTS: All A. hydrophila clinical isolates exhibited carbapenem resistance but were not genetically related. Diverse resistance determinants corresponding to extensively-drug resistant were found, including co-occurring KPC-3 and VIM-2, OXA-232, and chromosomal CphA-like carbapenemase genes, contributing to major treatment challenges. All 3 patients were treated with multiple antibiotic regimens to overcome various carbapenemase classes and expired due to underlying comorbidities. Environmental culture yielded no Aeromonas. CONCLUSIONS: While the investigation revealed no singular source of contamination, it supports a possible link between plumbing issues, elevated outdoor temperatures and incidence of nosocomial Aeromonas infections. The diversity of carbapenemase genes detected in these wastewater-derived Aeromonas warrants heightened infection prevention precautions during periods of plumbing problems especially with heat waves.

Extensively Drug-Resistant Shigella flexneri 2a, California, USA, 2022.

In Los Angeles, California, USA, persistent, refractory shigellosis was diagnosed in an immunocompetent man who has sex with men. Whole-genome sequencing augmented phenotypic antimicrobial susceptibility testing to comprehensively profile bacterial drug resistance and appropriately guide therapy and clear the infection.

Case Report: Symptomatic Herpes Simplex Virus Type 2 and Monkeypox Coinfection in an Adult Male.

A 39-year-old man presented with a history of fatigue, malaise, and rash with varied morphology on his perianal region. Polymerase chain reaction testing of the lesions confirmed coinfection with monkeypox and herpes simplex virus type 2. We emphasize the difficulty in distinguishing between monkeypox virus and herpes simplex virus type 2 based on history and examination alone.

Prevalence and Factors Associated With Antigen Test Positivity Following SARS-CoV-2 Infection Among Health Care Workers in Los Angeles.

Surges of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections among health care workers (HCWs) have led to critical staffing shortages. From January 4 to February 4, 2022, we implemented a return-to-work antigen testing program for HCWs, and 870 HCWs participated. Antigen test positivity was 60.5% for those ≤5 days from symptom onset or positive polymerase chain reaction (PCR), and 47.4% were positive at day 7. Antigen positivity was associated with receiving a booster vaccination and being ≤6 days from symptom onset or PCR test, but not age or a symptomatic infection. Rapid antigen testing can be a useful tool to guide return-to-work and isolation precautions for HCWs following infection.

The Path of More Resistance: a Comparison of National Healthcare Safety Network and Clinical Laboratory Standards Institute Criteria in Developing Cumulative Antimicrobial Susceptibility Test Reports and Institutional Antibiograms.

In the absence of antimicrobial susceptibility data, the institutional antibiogram is a valuable tool to guide clinicians in the empirical treatment of infections. However, there is a misunderstanding about how best to prepare cumulative antimicrobial susceptibility testing reports (CASTRs) to guide empirical therapy (e.g., routine antibiogram) versus monitoring antimicrobial resistance, with the former following guidance from the Clinical and Laboratory Standards Institute (CLSI) and the latter from the Centers for Disease Control and Prevention's National Healthcare Safety Network (NHSN). These criteria vary markedly in their exclusion or inclusion of isolates cultured repeatedly from the same patient. We compared rates of nonsusceptibility (NS) using annual data from a large teaching health care system subset to isolates eligible by either NHSN criteria or CLSI criteria. For a panel of the three most prevalent Gram-negative pathogens in combination with clinically relevant antimicrobial agents (or priority pathogen-agent combinations [PPACs]), we found that the inclusion of duplicate isolates by NHSN criteria yielded higher NS rates than when CLSI criteria (for which duplicate isolates are not included) were applied. Patients with duplicate isolates may not be representative of antimicrobial resistance within a population. For this reason, users of CASTR data should carefully consider that the criteria used to generate these reports can impact resulting NS rates and, therefore, maintain the distinction between CASTRs created for different purposes.

Vaccine-Associated Measles in a Hematopoietic Cell Transplant Recipient: Case Report and Comprehensive Review of the Literature.

Measles is a worldwide viral disease that can cause fatal complications in immunocompromised hosts such as hematopoietic cell transplant (HCT) recipients. The live attenuated measles, mumps, and rubella (MMR) vaccine is generally contraindicated post-HCT due to the risk for vaccine-associated measles. This, combined with decreasing vaccination rates due to vaccine hesitancy and the coronavirus disease 2019 pandemic, raises significant concerns for a measles resurgence that could portend devastating consequences for immunocompromised hosts. Multiple guidelines have included criteria to determine which HCT recipients can safely receive the MMR vaccine. Here, we report a case of vaccine-associated measles in a HCT recipient who met guideline-recommended criteria for MMR vaccination. The objective of this article is to query these criteria, highlight the importance of MMR vaccination, and comprehensively review the literature.

Evaluation of antibiotic escalation in response to nurse-driven inpatient sepsis screen.

Objective: To determine the frequency and predictors of antibiotic escalation in response to the inpatient sepsis screen at our institution. Design: Retrospective cohort study. Setting: Two affiliated academic medical centers in Los Angeles, California. Patients: Hospitalized patients aged 18 years and older who had their first positive sepsis screen between January 1, 2019, and December 31, 2019, on acute-care wards. Methods: We described the rate and etiology of antibiotic escalation, and we conducted multivariable regression analyses of predictors of antibiotic escalation. Results: Of the 576 cases with a positive sepsis screen, antibiotic escalation occurred in 131 cases (22.7%). New infection was the most documented etiology of escalation, with 76 cases (13.2%), followed by known pre-existing infection, with 26 cases (4.5%). Antibiotics were continued past 3 days in 17 cases (3.0%) in which new or existing infection was not apparent. Abnormal temperature (adjusted odds ratio [aOR], 3.00; 95% confidence interval [CI], 1.91-4.70) and abnormal lactate (aOR, 2.04; 95% CI, 1.28-3.27) were significant predictors of antibiotic escalation. The patient already being on antibiotics (aOR, 0.54; 95% CI, 0.34-0.89) and the positive screen occurred during a nursing shift change (aOR, 0.36; 95% CI, 0.22-0.57) were negative predictors. Pneumonia was the most documented new infection, but only 19 (50%) of 38 pneumonia cases met full clinical diagnostic criteria. Conclusions: Inpatient sepsis screening led to a new infectious diagnosis in 13.2% of all positive sepsis screens, and the risk of prolonged antibiotic exposure without a clear infectious source was low. Pneumonia diagnostics and lactate testing are potential targets for future stewardship efforts.

Clinical and Epidemiologic Evaluation of Inconclusive COVID-19 PCR Results Using a Quantitative Algorithm.

OBJECTIVES: The inconclusive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) polymerase chain reaction (PCR) result causes confusion and delay for infection prevention precautions and patient management. We aimed to develop a quantitative algorithm to assess and interpret these inconclusive results. METHODS: We created a score-based algorithm by combining laboratory, clinical, and epidemiologic data to evaluate 69 cases with inconclusive coronavirus disease 2019 (COVID-19) PCR results from the Centers for Disease Control and Prevention (CDC) assay (18 cases) and the TaqPath assay (51 cases). RESULTS: We determined 5 (28%) of 18 (CDC assay) and 20 (39%) of 51 (TaqPath assay) cases to be false positive. Lowering the cycle threshold cutoff from 40 to 37 in the TaqPath assay resulted in a dramatic reduction of the false-positive rate to 14%. We also showed testing of asymptomatic individuals is associated with a significantly higher probability of having a false-positive result. CONCLUSIONS: A substantial percentage of inconclusive SARS-CoV-2 PCR results can be false positive, especially among asymptomatic patients. The quantitative algorithm we created was shown to be effective and could provide a useful tool for clinicians and hospital epidemiologists to interpret inconclusive COVID-19 PCR results and provide clinical guidance when additional PCR or antibody test results are available.

Rapid implementation of ultraviolet germicidal irradiation and reuse processes for N95 respirators at a health system during the coronavirus disease 2019 (COVID-19) pandemic.

An N95 respirator ultraviolet germicidal irradiation and reuse program was rapidly implemented at an academic health system in the United States during the coronavirus disease 2019 pandemic. This process continues to be a safe and effective way to slow the consumption rate of N95 respirators.

Low prevalence (0.13%) of COVID-19 infection in asymptomatic pre-operative/pre-procedure patients at a large, academic medical center informs approaches to perioperative care.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic has resulted in reduced performance of elective surgeries and procedures at medical centers across the United States. Awareness of the prevalence of asymptomatic disease is critical for guiding safe approaches to operative/procedural services. As COVID-19 polymerase chain reaction (PCR) testing has been limited largely to symptomatic patients, health care workers, or to those in communal care centers, data regarding asymptomatic viral disease carriage are limited. METHODS: In this retrospective observational case series evaluating UCLA Health patients enrolled in pre-operative/pre-procedure protocol COVID-19 reverse transcriptase (RT)-PCR testing between April 7, 2020 and May 21, 2020, we determine the prevalence of COVID-19 infection in asymptomatic patients scheduled for surgeries and procedures. RESULTS: Primary outcomes include the prevalence of COVID-19 infection in this asymptomatic population. Secondary data analysis includes overall population testing results and population demographics. Eighteen of 4,751 (0.38%) patients scheduled for upcoming surgeries and high-risk procedures had abnormal (positive/inconclusive) COVID-19 RT-PCR testing results. Six of 18 patients were confirmed asymptomatic and had positive test results. Four of 18 were confirmed asymptomtic and had inconclusive results. Eight of 18 had positive results in the setting of recent symptoms or known COVID-19 infection. The prevalence of asymptomatic COVID-19 infection was 0.13%. More than 90% of patients had residential addresses within a 67-mile geographic radius of our medical center, the median age was 58, and there was equal male/female distribution. CONCLUSION: These data demonstrating low levels (0.13% prevalence) of COVID-19 infection in an asymptomatic population of patients undergoing scheduled surgeries/procedures in a large urban area have helped to inform perioperative protocols during the COVID-19 pandemic. Testing protocols like ours may prove valuable for other health systems in their approaches to safe procedural practices during COVID-19.

Stopping the routine use of contact precautions for management of MRSA and VRE at three academic medical centers: An interrupted time series analysis.

BACKGROUND: Contact precautions (CP) are a widely adopted strategy to prevent cross-transmission of organisms, commonly methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). Some hospitals have discontinued CP for patients with MRSA or VRE; however, the impact on hospital-acquired infection rates (HAI) has not been assessed systematically. METHODS: Retrospective multicenter interrupted time series between 2002 and 2017 at three academic hospitals. Participating hospitals discontinued CP for patients with contained body fluids who were colonized or infected with MRSA or VRE. The primary intervention was stopping the use of CP. Secondary interventions were horizontal infection prevention strategies. The primary outcomes were rates of central line-associated bloodstream infections, catheter-associated urinary tract infections, mediastinal surgical site infection, and ventilator-associated pneumonia due to MRSA, VRE, or any organism using Centers for Disease Control and Prevention National Healthcare Safety Network surveillance definitions. RESULTS: Central line-associated bloodstream infections, catheter-associated urinary tract infections, mediastinal surgical site infection, and ventilator-associated pneumonia rates trended down at each institution. There were no statistically significant increases in these infections associated with discontinuing CP. Individual horizontal infection prevention strategies variably impacted HAI outcomes. CONCLUSIONS: Stopping the routine use of CP for patients with contained body fluids who are colonized or infected with MRSA or VRE did not result in increased HAIs. Bundled horizontal infection prevention strategies resulted in sustained HAI reductions.

Association of a Care Bundle for Early Sepsis Management With Mortality Among Patients With Hospital-Onset or Community-Onset Sepsis.

Importance: The Early Management Bundle for Severe Sepsis/Septic Shock (SEP-1) is a quality metric based on a care bundle for early sepsis management. Published evidence on the association of SEP-1 with mortality is mixed and largely excludes cases of hospital-onset sepsis. Objective: To assess the association of the SEP-1 bundle with mortality and organ dysfunction in cohorts with hospital-onset or community-onset sepsis. Design, Setting, and Participants: This retrospective cohort study used data from 4 University of California hospitals from October 1, 2014, to October 1, 2017. Adult inpatients with a diagnosis consistent with sepsis or disseminated infection and laboratory or vital signs meeting the Sepsis-3 (Third International Consensus Definitions for Sepsis and Septic Shock) criteria were divided into community-onset sepsis and hospital-onset sepsis cohorts based on whether time 0 of sepsis occurred after arrival in the emergency department or an inpatient area. Data were analyzed from April to October 2019. Additional analyses were performed from December 2019 to January 2020. Exposures: Administration of SEP-1 and 4 individual bundle components (serum lactate level testing, blood culture, broad-spectrum intravenous antibiotic treatment, and intravenous fluid treatment). Main Outcomes and Measures: The primary outcome was in-hospital mortality. The secondary outcome was days requiring vasopressor support, measured as vasopressor days. Results: Among the 6404 patient encounters identified (3535 men [55.2%]; mean [SD] age, 64.0 [18.2] years), 2296 patients (35.9%) had hospital-onset sepsis. Among 4108 patients (64.1%) with community-onset sepsis, serum lactate level testing within 3 hours of time 0 was associated with reduced mortality (absolute difference, -7.61%; 95% CI, -14.70% to -0.54%). Blood culture (absolute difference, -1.10 days; 95% CI, -1.85 to -0.34 days) and broad-spectrum intravenous antibiotic treatment (absolute difference, -0.62 days; 95% CI, -1.02 to -0.22 days) were associated with fewer vasopressor days. Among patients with hospital-onset sepsis, broad-spectrum intravenous antibiotic treatment was the only bundle component significantly associated with any improved outcome (mortality difference, -5.20%; 95% CI, -9.84% to -0.56%). Care that was adherent to the complete SEP-1 bundle was associated with increased vasopressor days in patients with community-onset sepsis (absolute difference, 0.31 days; 95% CI, 0.11-0.51 days) but was not significantly associated with reduced mortality in either cohort (absolute difference, -0.07%; 95% CI, -3.02% to 2.88% in community-onset; absolute difference, -0.42%; 95% CI, -6.77% to 5.93% in hospital-onset). Conclusions and Relevance: SEP-1-adherent care was not associated with improved outcomes of sepsis. Although multiple components of SEP-1 were associated with reduced mortality or decreased days of vasopressor therapy for patients who presented with sepsis in the emergency department, only broad-spectrum intravenous antibiotic treatment was associated with reduced mortality when time 0 occurred in an inpatient unit. Current sepsis quality metrics may need refinement.

Adherence to the SEP-1 Sepsis Bundle in Hospital-Onset v. Community-Onset Sepsis: a Multicenter Retrospective Cohort Study.

BACKGROUND: Sepsis is the leading cause of in-hospital death. The SEP-1 sepsis bundle is a protocol for early sepsis care that requires providers to diagnose and treat sepsis quickly. Limited evidence suggests that adherence to the sepsis bundle is lower in cases of hospital-onset sepsis. OBJECTIVE: To compare sepsis bundle adherence in hospital-onset vs. community-onset sepsis. DESIGN: Retrospective cohort study using multivariable analysis of clinical data. PARTICIPANTS: A total of 4658 inpatients age 18 or older were identified by diagnosis codes consistent with sepsis or disseminated infection. SETTING: Four university hospitals in California between 2014 and 2016. MAIN OUTCOMES AND MEASURES: The primary outcome was adherence to key components of the sepsis bundle defined by the Centers for Medicare and Medicaid Services in their core measure, SEP-1. Covariates included clinical characteristics related to the patient, infection, and pathogen. KEY RESULTS: Compared with community-onset, cases of hospital-onset sepsis were less likely to receive SEP-1 adherent care (relative risk 0.33, 95% confidence interval 0.29-0.38, p < 0.001). With the exception of vasopressors (RR 1.11, p = 0.002), each component of SEP-1 evaluated-blood cultures (RR 0.76, p < 0.001), serum lactate (RR 0.51, p < 0001), broad-spectrum antibiotics (RR 0.62, p < 0.001), intravenous fluids (0.47, p < 0.001), and follow-up lactate (RR 0.71, p < 0.001)-was less likely to be performed within the recommended time frame in hospital-onset sepsis. Within the hospital, cases of hospital-onset sepsis arising on the ward were less likely to receive SEP-1-adherent care than were cases arising in the intensive care unit (RR 0.68, p = 0.004). CONCLUSIONS: Inpatients with hospital-onset sepsis receive different management than individuals with community-onset sepsis. It remains to be determined whether system-level factors, provider-level factors, or factors related to measurement explain the observed variation in care or whether variation in care affects outcomes.

Risk factors for development of aminoglycoside resistance among gram-negative rods.

PURPOSE: Development of scoring systems to predict the risk of aminoglycoside resistance and to guide therapy is described. METHODS: Infections due to aminoglycoside-resistant gram-negative rods (AR-GNRs) are increasingly common and associated with adverse outcomes; selection of effective initial antibiotic therapy is necessary to reduce adverse consequences and shorten length of stay. To determine risk factors for AR-GNR recovery from culture, cases of GNR infection among patients admitted to 2 institutions in a major academic hospital system during the period 2011-2016 were retrospectively analyzed. Gentamicin and tobramycin resistance (GTR-GNR) and amikacin resistance (AmR-GNR) patterns were analyzed separately. A total of 26,154 GNR isolates from 12,516 patients were analyzed, 6,699 of which were GTR, and 2,467 of which were AmR. RESULTS: In multivariate analysis, risk factors for GTR-GNR were presence of weight loss, admission from another medical or long-term care facility, a hemoglobin level of <11 g/dL, receipt of any carbapenem in the prior 30 days, and receipt of any fluoroquinolone in the prior 30 days (C statistic, 0.63). Risk factors for AmR-GNR were diagnosis of cystic fibrosis, male gender, admission from another medical or long-term care facility, ventilation at any point prior to culture during the index hospitalization, receipt of any carbapenem in the prior 30 days, and receipt of any anti-MRSA agent in the prior 30 days (C statistic, 0.74). Multinomial and ordinal models demonstrated that the risk factors for the 2 resistance patterns differed significantly. CONCLUSION: A scoring system derived from the developed risk prediction models can be applied by providers to guide empirical antimicrobial therapy for treatment of GNR infections.

Cardiovascular implantable electronic device infections due to enterococcal species: Clinical features, management, and outcomes.

BACKGROUND: Enterococcal cardiovascular implantable electronic device (CIED) infections are not well characterized. METHODS: Data from the Multicenter Electrophysiologic Device Infection Cohort, a prospective study of CIED infections, were used for descriptive analysis of adults with enterococcal CIED infections. RESULTS: Of 433 patients, 21 (4.8%) had enterococcal CIED infection. Median age was 71 years. Twelve patients (57%) had permanent pacemakers, five (24%) implantable cardioverter defibrillators, and four (19%) biventricular devices. Median time from last procedure to infection was 570 days. CIED-related bloodstream infections occurred in three patients (14%) and 18 (86%) had infective endocarditis (IE), 14 (78%) of which were definite by the modified Duke criteria. IE cases were classified as follows: valvular IE, four; lead IE, eight; both valve and lead IE, six. Vegetations were demonstrated by transesophageal echocardiography in 17 patients (81%). Blood cultures were positive in 19/19 patients with confirmed results. The most common antimicrobial regimen was penicillin plus an aminoglycoside (33%). Antibiotics were given for a median of 43 days. Only 14 patients (67%) underwent device removal. There was one death during the index hospitalization with four additional deaths within 6 months (overall mortality 24%). There were no relapses. CONCLUSIONS: Enterococci caused 4.8% of CIED infections in our cohort. Based on the late onset after device placement or manipulation, most infections were likely hematogenous in origin. IE was the most common infection syndrome. Only 67% of patients underwent device removal. At 6 months follow-up, no CIED infection relapses had occurred, but overall mortality was 24%.

Risk Factors for Development of Carbapenem Resistance Among Gram-Negative Rods.

BACKGROUND: Infections due to carbapenem-resistant Gram-negative rods (CR-GNR) are increasing in frequency and result in high morbidity and mortality. Appropriate initial antibiotic therapy is necessary to reduce adverse consequences and shorten length of stay. METHODS: To determine risk factors for recovery on culture of CR-GNR, cases were retrospectively analyzed at a major academic hospital system from 2011 to 2016. Ertapenem resistance (ER-GNR) and antipseudomonal (nonertapenem) carbapenem resistance (ACR-GNR) patterns were analyzed separately. A total of 30951 GNR isolates from 12370 patients were analyzed, 563 of which were ER and 1307 of which were ACR. RESULTS: In multivariate analysis, risk factors for ER-GNR were renal disease, admission from another health care facility, ventilation at any point before culture during the index hospitalization, receipt of any carbapenem in the prior 30 days, and receipt of any anti-methicillin-resistant Staphylococcus aureus (anti-MRSA) agent in the prior 30 days (c-statistic, 0.74). Risk factors for ACR-GNR were male sex, admission from another health care facility, ventilation at any point before culture during the index hospitalization, receipt of any carbapenem in the prior 30 days, and receipt of any anti-MRSA agent in the prior 30 days (c-statistic, 0.76). CONCLUSIONS: A straightforward scoring system derived from these models can be applied by providers to guide empiric antimicrobial therapy; it outperformed use of a standard hospital antibiogram in predicting infections with ER-GNR and ACR-GNR.

Risk Factors for Colistin Resistance among Gram-Negative Rods and Klebsiella pneumoniae Isolates.

Infections due to colistin-resistant (Colr) Gram-negative rods (GNRs) and colistin-resistant Klebsiella pneumoniae isolates in particular result in high associated mortality and poor treatment options. To determine the risk factors for recovery on culture of Colr GNRs and ColrK. pneumoniae, analyses were chosen to aid decisions at two separate time points: the first when only Gram stain results are available without any bacterial species information (corresponding to the Colr GNR model) and the second when organism identification is performed but prior to reporting of antimicrobial susceptibility testing results (corresponding to the ColrK. pneumoniae model). Cases were retrospectively analyzed at a major academic hospital system from 2011 to 2016. After excluding bacteria that were intrinsically resistant to colistin, a total of 28,512 GNR isolates (4,557 K. pneumoniae isolates) were analyzed, 128 of which were Colr (i.e., MIC > 2 µg/ml), including 68 of which that were ColrK. pneumoniae In multivariate analysis, risk factors for Colr GNRs were neurologic disease, residence in a skilled nursing facility prior to admission, receipt of carbapenems in the last 90 days, prior infection with a carbapenem-resistant organism, and receipt of ventilatory support (c-statistic = 0.81). Risk factors for ColrK. pneumoniae specifically were neurologic disease, residence in a skilled nursing facility prior to admission, receipt of carbapenems in the last 90 days, receipt of an anti-methicillin-resistant Staphylococcus aureus antimicrobial in the last 90 days, and prior infection with a carbapenem-resistant organism (c-statistic = 0.89). A scoring system derived from these models can be applied by providers to guide empirical antimicrobial therapy in patients with infections with suspected Colr GNR and ColrK. pneumoniae isolates.