Tri-layer microbiology for LMIC Hospitals: linking syndromic panels with reflex culture and targeted sequencing for real world care - a narrative review

Rapid, syndromic molecular panels and high throughput sequencing have transformed the diagnostic landscape for sepsis, respiratory, gastrointestinal, and central nervous system infections, but their value in routine practice depends on how they are integrated with conventional microbiology and antimicrobial stewardship. This review synthesises recent high-quality evidence to propose a pragmatic three-tier hybrid framework. Tier 1 comprises syndrome specific rapid panels that provide organism and selected resistance markers within hours, primarily to accelerate early escalation or de-escalation rather than to replace culture. Tier 2 positions reflex culture and targeted adjunct tests as the non-negotiable specificity anchor, confirming molecular hits, distinguishing infection from colonisation or contamination, generating phenotypic susceptibility data and supplying isolates for infection prevention and public health surveillance. Tier 3 reserves targeted or metagenomic sequencing for a small, clinically critical subset of high suspicion, panel negative and culture negative cases, where additional breadth can realistically change management. Across sepsis/BSI, pneumonia, gastrointestinal infection and CNS disease, available data indicate that clinical benefit is driven less by any individual technology and more by disciplined implementation: clear indications, explicit reflex rules, close linkage to antimicrobial stewardship and systematic audit of key performance indicators such as time-to-targeted therapy, spectrum of antimicrobial use and cost per additional actionable diagnosis. The proposed tiered, syndrome wise algorithms provide a transferable conceptual scaffold that can be adapted to local resources, allowing laboratories in both high and low resource settings to introduce advanced diagnostics without abandoning culture-based anchors or stewardship accountability.