Does Antibiotic Resistance Evolve in Hospitals?

Area of Science:

• Microbiology
• Epidemiology
• Statistical Modeling

Background:

• Nosocomial bacterial outbreaks are common, leading to the assumption that antibiotic resistance primarily evolves within hospital settings due to high antibiotic use.
• Understanding the specific drivers of antibiotic resistance evolution in hospitals is crucial for effective infection control and antibiotic stewardship.

Purpose of the Study:

• To investigate whether antibiotic resistance phenotypes of bacteria evolve significantly within a community hospital environment over time.
• To develop and validate a statistical method for detecting trends in antibiotic resistance evolution in hospitals.

Main Methods:

• Analysis of bacterial resistance phenotypes from patient isolates over a 2.5-year period at a community hospital.
• Development of a hospital transmission model and a statistical hypothesis test, the Nosocomial Evolution of Resistance Detector (NERD), to assess resistance trends.
• Application of the NERD method to 16 different antibiotics, performing 16 hypothesis tests.

Main Results:

• Graphical model analysis indicated no association between resistance and patient information, except for time of arrival, suggesting focus on time-course data.
• The NERD method found no significant hospital-specific effect on resistance evolution for 13 out of 16 antibiotics studied.
• Significant trends were observed for cefepime, ceftazidime, and gentamicin, with ceftazidime showing a significant decrease in resistance after adjusting for multiple hypotheses.

Conclusions:

• The hospital environment is not the sole determinant of antibiotic resistance evolution; it is part of a larger picture.
• The NERD tool can help hospital staff monitor antibiotic resistance trends, detect clonal outbreaks, and evaluate interventions.
• Specific antibiotics like cefepime, ceftazidime, and gentamicin warrant closer monitoring and careful management within hospital practices due to observed resistance trends.