Which technology yields antimicrobial susceptibilities in about 7 hours?

• A. PCR
• B. MALDI-TOF MS
• C. Nanoparticle probe technology
• D. Multiplex FISH

Answer: (D)

Rapid antimicrobial susceptibility testing aims to deliver usable results quickly by combining identification with resistance information in a single workflow. Multiplex FISH achieves this by using several fluorescent probes that bind specifically to rRNA sequences from multiple organisms, so you can identify several pathogens at once. When this approach is paired with probes for common resistance determinants and performed directly on clinical material after a short antibiotic exposure, you get a readout that reflects both who is present and how they respond to the drug in a timeframe on the order of hours rather than days. That combination—multiplexed identification plus rapid detection of resistance in a single assay—yields susceptibility information in roughly seven hours, which is faster than traditional culture-based testing and more practical for guiding early therapy. Other methods like PCR focus on resistance genes, which may not fully predict actual susceptibility; MALDI-TOF MS is excellent for identifying organisms but typically requires longer or separate steps for reliable phenotypic susceptibility data; nanoparticle probe approaches are less standardized for routine AST.