identifier: traitmech:000046 label: opportunistic pathogen definition: A host-association lifestyle in which a normally commensal or environmental microorganism causes disease only when host defenses are compromised or it reaches a normally sterile site. definition_source: DOI:10.1016/j.tim.2012.04.005 trait_category: ECOLOGY term_kind: CLASS mapping_status: REVIEWED parent_traits: - METPO:1004000 synonyms: - synonym_text: opportunistic infection synonym_type: RELATED_SYNONYM source: DOI:10.1016/j.tim.2012.04.005 evidence: - reference: DOI:10.1016/j.tim.2012.04.005 notes: Brown, Cornforth & Mideo, "Evolution of virulence in opportunistic pathogens", support context-dependent virulence maintained by advantages outside the host. - reference: DOI:10.1038/s41579-021-00550-7 notes: Drew et al. support facultative shifts toward parasitism/pathogenicity along the parasite-mutualist continuum, the basis of opportunistic disease. canonical_examples: - taxon_id: NCBITaxon:470 taxon_label: Acinetobacter baumannii note: "Archetypal opportunistic nosocomial pathogen (multidrug-resistant; infects immunocompromised hosts)." reference: PMID:22546906 causal_graphs: - graph_id: opportunistic_pathogen_context_dependent_virulence title: Opportunistic pathogenesis under compromised host defense description: Evidence-backed causal sketch linking compromised host defenses to context-dependent virulence in normally commensal/environmental microbes. nodes: - node_id: opportunistic_pathogen_trait label: opportunistic pathogen node_type: TRAIT grounding: traitmech:000046 description: Disease causation only under compromised host defenses or sterile-site translocation. - node_id: compromised_host_defense label: compromised host defense node_type: ENVIRONMENTAL_FACTOR description: Immunosuppression, barrier breach, or sterile-site translocation. - node_id: opportunistic_infection label: opportunistic infection node_type: BIOLOGICAL_PROCESS description: Disease arising from a normally commensal or environmental microbe in a permissive host context. - node_id: barrier_breach label: epithelial barrier breach / sterile site access node_type: ENVIRONMENTAL_FACTOR description: Disruption of epithelial barriers exposing normally sterile tissue to microbes. - node_id: antibiotic_exposure label: antibiotic exposure node_type: CHEMICAL description: Prior or concurrent antimicrobial treatment. - node_id: microbiota_dysbiosis label: microbiota dysbiosis node_type: STATE description: Disrupted microbial community composition permitting opportunist expansion. - node_id: opportunist_colonization label: opportunist colonization / overgrowth node_type: BIOLOGICAL_PROCESS description: Increased colonization or overgrowth by opportunistic microbes. - node_id: host_colonization label: host colonization without disease node_type: BIOLOGICAL_PROCESS description: Microbial colonization of a host site that may or may not progress to infection. - node_id: nutritional_immunity label: nutritional immunity / iron limitation node_type: ENVIRONMENTAL_FACTOR description: Host-imposed restriction of nutrient metals such as iron. - node_id: high_affinity_iron_acquisition label: high-affinity iron acquisition node_type: BIOLOGICAL_PROCESS description: Induction of high-affinity iron transport and siderophore production under iron limitation. edges: - subject: compromised_host_defense predicate: causes object: opportunistic_infection description: Breached or weakened host defenses enable a normally innocuous microbe to cause disease. evidence: - reference: DOI:10.1016/j.tim.2012.04.005 notes: Brown et al. support context-dependent virulence in opportunistic pathogens. predicate_id: biolink:causes - subject: opportunistic_infection predicate: enables object: opportunistic_pathogen_trait description: Context-dependent infection realizes the opportunistic-pathogen lifestyle. evidence: - reference: DOI:10.1038/s41579-021-00550-7 notes: Drew et al. support facultative shifts toward pathogenicity along the parasite-mutualist continuum. predicate_id: RO:0002327 - subject: barrier_breach predicate: enables object: opportunistic_infection description: Barrier breach exposes sterile tissue, enabling infection by normally innocuous microbes. evidence: - reference: DOI:10.1038/s41579-024-01035-z notes: 'Uberoi et al.: barrier breach exposes sterile tissue to microbes (generalizable ecological/clinical edge).' predicate_id: RO:0002327 - subject: antibiotic_exposure predicate: promotes object: microbiota_dysbiosis description: Antimicrobial exposure disrupts the resident microbiota, producing dysbiosis. evidence: - reference: DOI:10.1007/s40588-023-00190-w notes: 'Jacobsen: antibiotic exposure is a common risk factor driving overgrowth of opportunists; curated as exposure to dysbiosis.' predicate_id: RO:0002213 - subject: microbiota_dysbiosis predicate: increases object: opportunist_colonization description: Dysbiosis increases colonization/overgrowth by opportunistic microbes. evidence: - reference: DOI:10.1007/s40588-023-00190-w notes: 'Jacobsen: defects/dysbiosis permit expansion of normally controlled opportunists (high-level ecological edge).' predicate_id: RO:0002213 - subject: opportunist_colonization predicate: enables object: opportunistic_infection description: Expanded opportunist colonization provides the population reservoir from which infection can arise. evidence: - reference: DOI:10.1007/s40588-023-00190-w notes: 'Jacobsen: colonization is a risk factor preceding opportunistic disease.' predicate_id: RO:0002327 - subject: host_colonization predicate: progresses to under host susceptibility object: opportunistic_infection description: Most colonization is benign; only some progresses to infection under permissive host conditions, capturing context-dependence. evidence: - reference: DOI:10.1038/s41579-024-01035-z notes: 'Uberoi: nearly all wounds are colonized but only some progress to infection; opportunism is context-dependent, not equivalent to colonization.' - subject: nutritional_immunity predicate: promotes object: high_affinity_iron_acquisition description: Host iron limitation induces high-affinity iron transport and siderophore production, a general opportunist adaptation in-host. evidence: - reference: DOI:10.1111/1751-7915.14241 notes: 'Sanchez-Jimenez: under iron limitation, high-affinity iron transport systems are promoted (general iron-acquisition biology).' predicate_id: RO:0002213 - subject: high_affinity_iron_acquisition predicate: contributes to object: opportunistic_infection description: Iron acquisition under host-imposed restriction supports opportunist fitness during infection. evidence: - reference: DOI:10.1111/1751-7915.14241 notes: 'Sanchez-Jimenez: iron homeostasis is an exploitable in-host fitness/virulence determinant of opportunists.' predicate_id: RO:0002326 curation_history: - timestamp: '2026-06-02T00:00:00Z' curator: claude action: PROPOSED_FROM_RESEARCH changes: Proposed candidate ECOLOGY trait (opportunistic pathogen); sub-variant of the existing pathogenic_to_host class (METPO:1004000). llm_assisted: true - timestamp: '2026-06-09T14:00:00Z' curator: claude action: CURATED_CAUSAL_GRAPH changes: Added evidence-backed causal graph (opportunistic / context-dependent virulence) with RO/biolink predicate groundings; promoted PROPOSED to REVIEWED. llm_assisted: true - timestamp: '2026-06-23T00:00:00Z' curator: claude action: ENRICH_CAUSAL_GRAPH changes: Added 7 evidence-backed generic edges (7 new nodes) from the deep-research report. llm_assisted: true - timestamp: '2026-06-24T17:21:09Z' curator: claude action: GROUND_CAUSAL_PREDICATES changes: Grounded 6 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002213×3, RO:0002327×2, RO:0002326×1). llm_assisted: true