Concept
Antimicrobial Resistance
3 studiesEvidence last moved Sep 20, 2026
Antimicrobial resistance is the capacity of a pathogen to survive a drug that once controlled it. The studies here share a theme: the resistance is usually older, or more widespread, than the surveillance designed to detect it assumes.
Resistance policy depends on knowing when resistance arose and which organisms carry it, and both are inferred from tests that look for what is expected. Genome dating and systematic culture each show what the standard approach misses.
Studies
3
Findings
4
4 supporting · 0 challenging · 0 qualifying citations
Open tensions
1
Latest change
Concept page published
Antimicrobial Resistance
Currently
What we know
- The timeline separates when resistance arose from when it spread.
- The consistent ordering is what makes the diagnostic implication concrete.
- A more than fourfold rise in two years, in samples often dismissed as colonisation.
- More than half were culture-negative, so organism-specific conclusions rest on a minority of cases.
Largest unresolved question
Whether resistant isolates represent disease or colonisation is unresolved and design-dependent. Candiduria frequently reflects colonisation rather than invasive infection, so a rising resistance rate in urine is not directly a rising rate of resistant disease, while the keratitis series reports clinical outcomes but on the 45% of eyes that grew an organism.
Common misconceptions
A rapid rifampicin test is sufficient to detect emerging drug-resistant tuberculosis.
In this collection isoniazid resistance preceded rifampicin resistance 46 times to 2. A rifampicin-only test therefore misses the first step, detecting resistance only after a second mutation has been acquired.
Drug-resistant tuberculosis in high-HIV settings emerged because of HIV.
Genome dating placed the founding resistance mutations at 1957 and extensive resistance around 1995, before the local HIV expansion. HIV shapes transmission today, but the mutations pre-dated it.
Related
Claim ledger
What the evidence shows
Drawn from 3 studies in this library. Mix labels say which citation roles are present; they are not a strength score. Supports means evidence for a finding; Challenges means evidence against a stated position; Qualifies marks scope.
The timeline separates when resistance arose from when it spread.
Resistance mutations pre-dated the epidemic they are associated with. Dating a 50-member extensively drug-resistant tuberculosis clone placed katG S315T and a gidB deletion at 1957 (HPD 1937-1971), multidrug resistance around 1984 and extensive resistance around 1995 — before the local HIV expansion.
The consistent ordering is what makes the diagnostic implication concrete.
Resistance arises repeatedly rather than spreading from one origin. Multidrug resistance arose 56 separate times and extensive resistance 9 times in this collection, with isoniazid resistance preceding rifampicin resistance by 46 to 2.
A more than fourfold rise in two years, in samples often dismissed as colonisation.
Resistance rose sharply in an organism and site that receive little surveillance. Among 519 Candida isolates, 69.9% came from urine and overall fluconazole resistance was 16.5%; candiduria resistance rose from 6.8% in 2010-11 to 29.5% across 2012-13, with ERG11 A395T/W reaching 87.5-100% after 2014.
More than half were culture-negative, so organism-specific conclusions rest on a minority of cases.
Organism identity tracks exposure route and predicts severity. In 283 cases of bacterial keratitis, 45.2% were culture-positive, contact-lens cases were linked to Pseudomonas aeruginosa and non-lens cases to staphylococci (p = 0.017), 57.2% were hospitalised for a mean 8.0 days, and culture-positive eyes were older and more severe at presentation.
Debates
Tensions and limits
Some items are genuine disagreements on the same question. Others mark different assays, populations, or outcomes.
Whether resistant isolates represent disease or colonisation is unresolved and design-dependent. Candiduria frequently reflects colonisation rather than invasive infection, so a rising resistance rate in urine is not directly a rising rate of resistant disease, while the keratitis series reports clinical outcomes but on the 45% of eyes that grew an organism.
Whether resistant isolates represent disease or colonisation is unresolved and design-dependent. Candiduria frequently reflects colonisation rather than invasive infection, so a rising resistance rate in urine is not directly a rising rate of resistant disease, while the keratitis series reports clinical outcomes but on the 45% of eyes that grew an organism.
Study Role Design N Population Outcome Is fluconazole-resistant Candida hiding in urine? Supports Other12-year laboratory surveillance of Candida tropicalis isolates from candiduria vs invasive infection, plus ERG11 sequencing of fluconazole-resistant strains N=519 · 519 unique C. tropicalis isolates from 485 patients (2010–2021); 363 urine (69.9%) and 156 invasive (30.1%) Clinical C. tropicalis isolates from urine and invasive samples at a Beijing hospital laboratory Fluconazole/voriconazole resistance rates over time and ERG11 mutations (especially Y132F / A395T/W) What predicts bad outcomes in bacterial keratitis? Supports CohortRetrospective consecutive suspected bacterial keratitis presenting to Queen’s Medical Centre, Nottingham, 2015–2019 (Nottingham Infectious Keratitis Study). N=283 · 283 patients / 283 eyes; mean age 54.4±21.0; 50.9% male; 45.2% culture-positive. Patients with suspected bacterial keratitis at a UK tertiary eye centre. Risk factors, culture results, hospitalisation/surgery, visual outcome (CDVA <0.6 logMAR), and delayed healing (>30 days).
PaperFren reads this as a limit on how far one study travels — different assays, populations, or outcomes — not a forced fight between papers.
Timeline
How understanding moved
Study years are when the paper was published. Evidence edits are dated changes to this page's claims. Explanations are when PaperFren added a Discovery — not a claim that the science happened that day.
2026
Concept page published
Antimicrobial Resistance
Change log
What changed
Dated edits to this page's evidence: studies added or removed from a claim, claims added or withdrawn, and new explanations tagged here. Rewordings are not listed.
- Concept page published
Papers
3 studies in this library bear on Antimicrobial Resistance, ordered by citations.
- How old is KwaZulu-Natal’s XDR tuberculosis outbreak strain?
WGS of 337 KZN isolates plus 3 historical genomes dated LAM4 XDR’s isoniazid/streptomycin mutations to ~1957 and found INH resistance evolved before rifampicin 46 times vs 2 the other way.
- What predicts bad outcomes in bacterial keratitis?
In 283 UK eyes with suspected bacterial keratitis, almost all had a risk factor (OSD 47%, contact lenses 35%, immunosuppression 18%); age >50, infiltrate >3 mm, and poor presenting vision predicted worse vision and slow healing.
- Is fluconazole-resistant Candida hiding in urine?
Among 519 C. tropicalis isolates, 16.5% were fluconazole-resistant (91.9% also voriconazole-resistant); candiduria resistance jumped to 29.5% after 2012, earlier than invasive strains.
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Questions
What is still open
Whether resistant isolates represent disease or colonisation is unresolved and design-dependent. Candiduria frequently reflects colonisation rather than invasive infection, so a rising resistance rate in urine is not directly a rising rate of resistant disease, while the keratitis series reports clinical outcomes but on the 45% of eyes that grew an organism.
Ask PaperFren about Antimicrobial Resistance
Study this conceptflashcards and short-answer questions
Why does the order in which resistance mutations appear matter for diagnostics?
Because tests detect specific mutations, so testing for the second one in a sequence means detecting resistance one step late. Isoniazid resistance preceded rifampicin resistance 46 times to 2 in this collection, which means a rifampicin-based rapid test systematically misses the founding step. Knowing the order converts a genomic observation into a change in test design.
What does 56 independent emergences of multidrug resistance imply for control strategy?
That containing transmission of a resistant clone is not sufficient, because resistance is being generated repeatedly under drug pressure. Multidrug resistance arose 56 separate times and extensive resistance 9 times in one provincial collection. A strategy aimed only at interrupting spread leaves the process that creates new resistant lineages untouched.
How should a rising resistance rate in urine isolates be interpreted?
Cautiously, because candiduria often reflects colonisation rather than invasive infection. The rise from 6.8% to 29.5% resistance, with ERG11 mutations reaching 87.5-100% after 2014, is a genuine change in the organisms present and a useful early warning. It is not equivalent to a fourfold rise in resistant invasive disease, and this is single-centre data from one country.