Periodic summary of local bacterial susceptibilities to antibiotics
Explanation
An antibiogram is a cumulative report of antimicrobial susceptibility test results for bacterial isolates collected in a specific laboratory over a defined period. It provides a periodic summary of antimicrobial susceptibilities of local bacterial isolates, typically updated annually【585648806022965†L12-L14】. The report lists the percentage of isolates of various bacteria that are susceptible to each antibiotic【585648806022965†L20-L21】, allowing clinicians to identify patterns of resistance. Antibiograms summarise the cumulative proportions of pathogenic organisms that are susceptible to particular antimicrobials【585648806022965†L33-L34】 and thus function as a tool for guiding empirical therapy, monitoring changes in resistance and informing stewardship programs. Data used to compile an antibiogram come from standardized culture and sensitivity testing performed in a clinical microbiology laboratory. Isolates are grouped by species and by patient care area, and duplicate isolates from the same patient are excluded to avoid bias. Laboratory information systems tally the number of isolates tested against each antimicrobial and calculate the percentage that fall within the susceptible category using interpretive criteria from standards such as the Clinical and Laboratory Standards Institute. Because resistance patterns vary by location and over time, hospitals and public health agencies create unit‑specific or region‑wide antibiograms to reflect local epidemiology. Clinicians use these summaries to choose empiric therapy before individual susceptibility results are available and to track emerging resistance trends.
Examples and notable uses
A hospital antibiogram might show that 90 percent of Escherichia coli isolates are susceptible to ceftriaxone and 70 percent to ciprofloxacin; this information helps physicians select appropriate empiric treatment for urinary tract infections. Intensive care unit‑specific antibiograms often reveal higher levels of resistance in organisms such as Pseudomonas aeruginosa, prompting the use of broader‑spectrum agents. Public health departments compile community antibiograms to track regional resistance trends in pathogens like Streptococcus pneumoniae or Neisseria gonorrhoeae. Some laboratories generate fungal or Mycobacterium‑specific antibiograms using susceptibility data from these organisms. Modern stewardship programs integrate antibiogram data into electronic prescribing systems to provide decision support at the point of care. Clinicians interpreting an antibiogram must understand that results represent aggregated data and may not predict susceptibility in every patient; culture and sensitivity testing remains essential for definitive therapy.
An antibiogram provides a snapshot of local antimicrobial susceptibility patterns and supports evidence‑based prescribing. Regular updates and careful interpretation are necessary to ensure that empirical therapy reflects current resistance trends and to guide stewardship efforts.
Related Terms: Susceptibility testing, Minimum inhibitory concentration, Clinical and Laboratory Standards Institute, Empiric therapy, Antimicrobial stewardship