Pathogen or coloniser? A diagnostic framework to optimise antimicrobial use and preserve antibiotic effectiveness
Yogesh A. Gupta, Geeta GuptaABSTRACT
Background:
Antimicrobial resistance is a major global health threat, and a substantial proportion of antibiotic exposure in hospitals appears to be directed at microbial colonisation rather than true infection. Therefore, distinguishing pathogens from colonisers at the point of care is central to antimicrobial and diagnostic stewardship.
Objective:
To synthesise current evidence on differentiating pathogenic infections from asymptomatic colonisation in common clinical scenarios and to provide practical, bedside-oriented frameworks that support safer, more targeted antimicrobial use.
Methods:
We conducted a structured narrative review of randomised and quasi-randomised trials, systematic reviews, large observational studies and major guideline documents published between January 1990 and December 2024, focussing on six syndromes where misclassification of colonisation as infection is frequent: asymptomatic bacteriuria (ASB), ventilator-associated tracheobronchitis versus ventilator-associated pneumonia, coagulase-negative staphylococci and other skin commensals in blood cultures, chronic wound colonisation, candiduria and mucosal
Results:
Across the six syndromes, consistent data suggest that withholding systemic antibiotics for clearly defined colonisation is generally safe in immunocompetent, clinically stable patients and is associated with substantial reductions in antibiotic use and adverse drug events without convincing evidence of increased mortality or progression to invasive infection in most studied settings. At the same time, the literature highlights specific high-risk groups, such as neutropenic hosts, patients with recent surgery or instrumentation and haemodynamically unstable intensive care unit patients, in whom a lower threshold for treatment or closer monitoring remains appropriate. Evidence regarding ventilator-associated tracheobronchitis, advanced diagnostic modalities for ventilator-associated pneumonia and biomarker-guided strategies such as procalcitonin remains heterogeneous and should be interpreted in the context of ongoing clinical controversies.
Conclusions:
Accurate discrimination between colonisation and infection should be regarded as a core clinical competency by prescribers. Applying syndrome-specific criteria, integrating biomarkers judiciously and embedding diagnostic stewardship into institutional practice can reduce unnecessary antimicrobial exposure while maintaining patient safety. Summary tables and practical algorithms may facilitate bedside implementation and education.