Colorado nursing home antibiogram

Guidance for use

The Colorado Nursing Home Antibiogram is a tool for antibiotic stewardship and is not intended for clinical use. It should be used in the context of other factors important to improving antibiotic use. Antibiotic stewards should consider principles of antibiotic stewardship, including the appropriate use of broad-spectrum antibiotics, de-escalation of empiric antibiotic coverage to targeted therapy, and use of evidence-based dose, duration, and route of administration. Health care providers should choose antibiotics based on activity, proven effectiveness, potential for antibiotic resistance or adverse events, and clinical judgment. If you need assistance reviewing the antibiogram tables, reach out to cdphe_hai_ar@state.co.us.

Background

An antibiogram is a summary of the antibiotic susceptibility of bacteria cultured from clinical specimens, usually specific to a health care facility. Health care providers use antibiograms to guide choice of antibiotic therapy before a patient’s microbiology test results are available. Antimicrobial stewardship programs use antibiograms to identify opportunities for improving antibiotic use, such as the inappropriate use of broad-spectrum antibiotics or antibiotics associated with rising rates of resistance. CDPHE previously published nursing home antibiograms in 2016 and 2017.

The Colorado Nursing Home Antibiogram is a report of pooled data submitted by eligible nursing homes. The objectives of this antibiogram are to:

• Provide a publicly available tool for antibiotic stewardship,
• Increase public knowledge of antibiotic resistance,
• Inform allocation of resources to improve antibiotic use, and
• Inform population-level antimicrobial stewardship strategy.

Methods

CDPHE reviewed 2023 antibiotic resistance data submitted to a single microbiology laboratory by Colorado nursing homes. The antibiogram includes data from 196 unique nursing homes. Most were located in the Denver region (53%); however, facilities were also located in the Southeast (30%) and Northeast regions (17%). None of the facilities were located in the Western Slope region of Colorado. 

Only organisms with 30 or more isolates were included in the antibiogram (CLSI. M39-ED5 2022). Polymicrobial isolates were excluded. Isolates were de-duplicated by selecting for the first isolate of each organism per resident, per year. Most isolates (95%) were sourced from urine cultures. Other culture sources included wound, blood, stool, and throat. 

We produced statewide antibiograms for gram-positive and gram-negative bacteria. Gram-positive bacteria included Enterococcus spp (both E. faecalis and E. faecium) and Staphylococcus aureus. Gram-negative bacteria included Enterobacter cloacae complex, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Proteus mirabilis, and Pseudomonas aeruginosa. To calculate the percent susceptible (%S) for each antibiotic-bacteria combination, we divided the pooled number of susceptible isolates by the number of isolates tested. Intrinsic resistance was indicated as “R” per CLSI guidelines (CLSI M100 2025). Combinations that were not recommended by CLSI or with isolates fewer than the minimum of 30 were grayed out.

Limitations

The Colorado Nursing Home Antibiogram has several limitations. Most (95%) of isolates were urine cultures, and findings may not be applicable to other sources of infection. Polymicrobial isolates were excluded, limiting the number of isolates available for analysis. Facilities in the Western Slope region do not submit data to this laboratory. Data suppression using selective or cascade reporting may inflate the calculated resistance to secondary antibiotic treatment options. Not all nursing homes in Colorado submit data to this laboratory.