Whole Metagenome Sequencing (mWGS)

Whole Metagenome Sequencing (mWGS) is a shotgun sequencing approach that reads all the DNA present in a clinical sample, without needing to grow a microbe in a laboratory culture. Rather than targeting a single pathogen or gene, it captures the entire genetic content of the microbial community at once, identifying bacteria, fungi, viruses, and parasites simultaneously.

Traditional diagnostic microbiology relies on culturing microorganisms, a process that may miss organisms that are difficult to grow, requires days to weeks, and cannot reveal the full community structure of the microbiome. mWGS overcomes these limitations because it does not require prior knowledge of what pathogen to look for, it is particularly powerful for diagnosing infections that have failed standard testing.

The test has two complementary applications:

Infectious disease diagnosis: In cases of culture-negative sepsis, unexplained meningitis or encephalitis, pneumonia in immunocompromised patients, or complex wound infections, mWGS can identify the causative organism and simultaneously screen for antibiotic resistance genes using curated database. This supports targeted antimicrobial therapy and helps clinicians move away from broad-spectrum antibiotic use.

Microbiome profiling: The composition of the gut, oral, skin, and respiratory microbiome is increasingly recognised as a major determinant of health and disease. Dysbiosis has been linked to inflammatory bowel disease, metabolic syndrome, recurrent infections, atopic disease, and even neurological conditions. mWGS provides species-level and strain-level resolution of the microbiome alongside functional information about metabolic pathways encoded by the microbial community. This goes beyond 16S rRNA amplicon sequencing, which has limited resolution and cannot detect fungi, viruses, or parasites.

1. Identifying causative pathogens in culture-negative infections, such as sepsis, central nervous system infections (meningitis, encephalitis), pneumonia, and complex infections.
2. Oral, skin, and respiratory microbiome characterisation for research or clinical investigation of chronic or recurrent local infections.
3. Simultaneous antibiotic resistance gene screening to guide targeted antimicrobial therapy and stewardship decisions.
4. Polymicrobial or mixed infection workup where multiple organisms are suspected and standard culture is likely to be incomplete.

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Culture-negative infections represent a substantial and diagnostically challenging subgroup of infectious diseases. Approximately 30–50% of sepsis cases yield negative blood cultures despite clinical evidence of infection, attributable to prior antibiotic exposure, slow-growing or fastidious organisms, intracellular pathogens, and fungi or viruses undetectable by routine bacterial culture. Metagenomic next-generation sequencing (mNGS) has emerged as a validated approach to address this diagnostic gap, with clinical studies demonstrating pathogen identification in 50–70% of culture-negative cases.

For CNS infections, mWGS of cerebrospinal fluid has been shown to identify pathogens in a significant proportion of encephalitis cases that remain undiagnosed by standard panels, including rare viruses, parasites, and bacteria not covered by conventional multiplex PCR.

The human gut microbiome comprises ~38 trillion microbial cells and encodes >150 times more genes than the human genome. Disruption of gut microbiome composition (dysbiosis) is causally associated with Clostridioides difficile infection (CDI), inflammatory bowel disease (IBD), obesity, type 2 diabetes, non-alcoholic fatty liver disease, and emerging evidence links it to colorectal cancer, neuropsychiatric conditions (the gut-brain axis), and immunotherapy response in oncology.

Antimicrobial resistance (AMR) is a global health emergency: the WHO estimates that drug-resistant infections caused 1.27 million deaths in 2019, and projections suggest 10 million annual deaths by 2050 if trends continue. mWGS enables direct detection of resistance genes from clinical specimens without requiring organism isolation, providing actionable resistance profiles even when culture fails.