Community State Type (CST)
Definition
A classification of vaginal microbiome profiles into distinct clusters. Most CSTs are dominated by a single Lactobacillus species; one CST (often called CST IV) is Lactobacillus-sparse and associated with diverse anaerobes, which can reduce the distinctiveness of the vaginal microbial signature.
- Abbreviation
- CST
- Field
- Microbiome-based body fluid identification
- Basis
- Vaginal microbiome clustering by dominant bacterial genus
- Notable subtype
- CST IV, Lactobacillus-sparse, diverse anaerobes
- Forensic effect
- CST IV weakens the distinctiveness of the vaginal signature
Common questions
Why does CST classification matter for forensic body fluid identification?+
Vaginal fluid identification methods that rely on a Lactobacillus-dominated signature work reliably for most donors, but a donor whose community falls into CST IV lacks that dominant Lactobacillus signal, so the same assay can give a weaker or ambiguous result depending purely on which CST the donor happens to have.
Is CST IV rare or unusual among individuals?+
No, it is a well-documented, naturally occurring community type found in a meaningful proportion of women across populations, not a pathological or abnormal state, though its prevalence varies by ethnicity and geography in published microbiome studies.
Related terms
- 16S rRNA Gene
- The gene encoding the 16S ribosomal RNA subunit present in all bacteria and archaea. Conserved regions allow universal amplification; hypervariable regions (V1-V9)...
- Amplicon Sequencing
- A sequencing approach where a specific locus (here the 16S hypervariable region) is amplified from all members of a microbial community and...
- Microbiome
- The total community of microorganisms (bacteria, archaea, fungi, viruses) inhabiting a body site, along with their collective genetic material. Each body site...
- OTU / ASV
- Operational Taxonomic Unit (OTU) and Amplicon Sequence Variant (ASV) are the units of microbial diversity in 16S data. OTUs cluster reads at...
- Shotgun Metagenomics
- Sequencing all DNA in a sample rather than just the 16S amplicon. Provides taxonomic resolution beyond 16S and can characterise viruses and...