by Antibiotics have revolutionized healthcare by allowing doctors to effectively treat bacterial infections. However, overuse and misuse of antibiotics has led to the rise of antibiotic-resistant bacteria. To continue effectively treating patients with bacterial infections, it is crucial that doctors select the most suitable antibiotics. This is where antimicrobial susceptibility testing comes in.
What is Antimicrobial Susceptibility Testing?
A small sample of the bacteria causing infection is collected from the patient and tested in the laboratory against various antibiotics. The testing reveals whether or not the bacterium is susceptible or resistant to each antibiotic tested. This helps doctors select the most appropriate antibiotic to prescribe.
Importance of Antimicrobial Susceptibility Testing
Antimicrobial susceptibility testing plays a vital role in several ways:
– Guides Antibiotic Selection: The test results directly inform doctors which antibiotic is most likely to effectively treat the patient’s bacterial infection. This optimizes treatment effectiveness.
– Reduces Overuse of Broad-Spectrum Antibiotics: By identifying the specific antibiotic a bacterium is sensitive to, it reduces over-prescription of broad-spectrum antibiotics. This helps slow the development of further antibiotic resistance.
– Detects Emerging Resistance: Continuous antimicrobial susceptibility monitoring helps detect emerging antibiotic resistance in bacteria. This alerts healthcare professionals and public health organizations to resistance trends in communities and facilitates timely interventions.
– Infection Control: Identifying antibiotic-resistant bacteria helps implement proper infection control measures like isolation or decolonization therapy for infected or colonized patients. This prevents spread of resistant bacteria to other patients.
Common Antimicrobial Susceptibility Testing Methods
Several standard laboratory methods are used to conduct Antimicrobial Susceptibility Testing
Disk Diffusion Method: Considered the reference standard method. Impregnated antibiotic discs are placed onto an agar plate seeded with the bacterium. Inhibition zones around each disc indicate susceptibility.
Automated Systems: Fully automated systems like VITEK and MicroScan use biochemical or colorimetric methods to rapidly test multiple antibiotics simultaneously and generate digital results.
Minimum Inhibitory Concentration (MIC): Determines the lowest concentration of an antibiotic needed to inhibit visible growth of a bacterium. Provides a more quantitative assessment of susceptibility.
broth microdilution and Etest are common MIC methods using results read visually or digitally. Other molecular-based techniques like nucleic acid amplification-based assays can also rapidly identify resistance genes directly from clinical samples.
Turnaround Time is Crucial
While traditional culture and testing takes 1-3 days for initial results, timely reporting of susceptibility profiles is important for optimal patient management and antibiotic stewardship. Newer techniques have reduced turnaround times:
– Rapid Methods: Assays using molecular principles like PCR, mass spectrometry, etc. can identify common resistance genes directly from positive blood cultures within hours, shortening time to effective therapy.
– Direct-from-Specimen Testing: Testing directly from specimens like urine or wounds instead of isolated colonies bypasses initial culture steps and provides preliminary results within 24 hours to guide early therapy.
– Automated Instruments: Continuous-run, walk-away technology of automated instruments processes hundreds of tests in a single day, generating digital results within hours instead of days.
– Artificial Intelligence: Machine learning algorithms applied to microscopic images of growth or molecular data can rapidly phenotype bacteria and infer resistance, potentially reducing turnaround times significantly.
Quality Assurance is Paramount
To ensure meaningful and reliable results, antimicrobial susceptibility testing must adhere to strict quality standards managed by laboratory accrediting organizations:
– Standardized Methodologies: Consistent use of validated reference methods like disk diffusion or MIC, with regular controls and documented competency.
– Inter-Laboratory Quality Assurance: Participation in external proficiency testing programs assesses reproducibility between laboratories.
– Equipment Calibration: Routine instrument calibration, cleaning and maintenance as per manufacturers’ guidelines.
– Interpretive Criteria: Application of current, evidence-based clinical and laboratory breakpoints to categorize isolates as sensitive, intermediate or resistant.
– Data Management: Digital storage and retrieval of testing metadata and antimicrobial resistance profiles for future reference.
In Conclusion, appropriate use of antimicrobial susceptibility testing backed by robust quality systems is indispensable for optimal treatment of infections and prudent antibiotic use. It continues to be a cornerstone of antimicrobial stewardship efforts globally.
Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
