Why do antibiotic-resistant infections affect countries differently, and what can researchers learn by comparing these patterns?

Hidenobu Matsuzaki, a PhD researcher at the London School of Hygiene & Tropical Medicine (LSHTM), recently visited the Conservatoire national des arts et métiers (Cnam) in Paris to explore how international collaboration could help answer these questions.

Hidenobu, a medical doctor studying on the Nagasaki University–LSHTM Joint PhD Programme and a Research Degree Student Representative at the LSHTM AMR Centre, investigates antibiotic-resistant bloodstream infections in the UK and Japan.

During his visit, he met researchers at Cnam's Modélisation, épidémiologie et surveillance des risques sanitaires (MESuRS) laboratory, where mathematical modelling is used to study infectious diseases, including antimicrobial resistance (AMR).

The visit provided an opportunity to exchange ideas, compare research approaches and explore potential collaborations.

One bacterium, different national patterns

Antimicrobial resistance (AMR) occurs when microorganisms, such as bacteria, no longer respond to medicines used to treat them (1).

One example is methicillin-resistant Staphylococcus aureus (MRSA), a type of bacteria resistant to certain antibiotics that can cause serious infections, including bloodstream infections (2).

However, MRSA does not affect every country in the same way. European surveillance data from 2019 showed that France had a higher proportion of methicillin-resistant S. aureus among samples from serious infections than the UK (3). Although both countries had seen substantial declines in resistance, their patterns differed.

Understanding why requires looking beyond the figures.

What could explain these differences?

Antibiotic use can favour resistant bacteria, while transmission allows them to spread (4,5). Differences in prescribing practices, infection prevention measures, healthcare contact and the types of bacteria circulating in a population may all influence national patterns.

Both countries offer useful lessons. In England and Wales, a national hand-hygiene campaign was associated with declining MRSA bloodstream infection rates. In France, a long-running programme involving 38 hospitals around Paris also reported reductions in MRSA, alongside measures including surveillance, infection prevention precautions, staff training and improved hand hygiene.

While these studies highlight the importance of prevention, they do not establish how much each measure contributed to the differences between countries.

Population characteristics also matter. Research involving LSHTM colleagues has shown that antibiotic resistance patterns vary by age and sex. As populations age, the number of resistant infections could change even if the overall proportion of resistant infections remains stable.

Shared questions, different perspectives

During my visit, I met Dr Quentin Leclerc, whose PhD was supervised by my own supervisor, Professor Gwen Knight. Quentin had also previously served as a Research Degree Student Representative at the LSHTM AMR Centre. Meeting someone with this shared connection made the international research network feel more personal.

Our teams are now exploring opportunities to collaborate. At Cnam, Chloé Aupépin's PhD research investigates the future burden of AMR in France, while my research focuses on resistant bloodstream infections in the UK and Japan.

Together, these projects provide an opportunity to explore how population changes, antibiotic use and different modelling approaches influence predictions of future antibiotic resistance.

However, comparing countries is not always straightforward. Surveillance systems collect data from different populations and healthcare settings, while testing practices and the types of information recorded can also vary.

These differences can affect both the resistance patterns we observe and our predictions for the future. Working with researchers who understand each country's healthcare system and data is therefore essential for making meaningful comparisons.

Learning across borders

For me, the visit reinforced the importance of international collaboration in research. Comparing our approaches and assumptions can help identify gaps or weaknesses that might otherwise go unnoticed when studying a single country.

Our aim is to develop predictions that reflect the circumstances of individual countries and help us better understand potential prevention strategies.

A single visit to Paris cannot answer every question about AMR, but it can help us ask better questions and find new ways to address them together.

References

1.Murray CJL, Ikuta KS, Sharara F, Swetschinski L, Robles Aguilar G, Gray A, et al. Global burden of bacterial antimicrobial resistance in 2019: a systematic analysis. The Lancet. 2022 Feb;399(10325):629–55. doi:10.1016/S0140-6736(21)02724-0

2.Naghavi M, Vollset SE, Ikuta KS, Swetschinski LR, Gray AP, Wool EE, et al. Global burden of bacterial antimicrobial resistance 1990–2021: a systematic analysis with forecasts to 2050. The Lancet. 2024 Sep;404(10459):1199–226. doi:10.1016/S0140-6736(24)01867-1

3.Cassini A, Högberg LD, Plachouras D, Quattrocchi A, Hoxha A, Simonsen GS, et al. Attributable deaths and disability-adjusted life-years caused by infections with antibiotic-resistant bacteria in the EU and the European Economic Area in 2015: a population-level modelling analysis. Lancet Infect Dis. 2019 Jan;19(1):56–66. doi:10.1016/S1473-3099(18)30605-4 PubMed PMID: 30409683; PubMed Central PMCID: PMC6300481.

4.C Reygaert W, Department of Biomedical Sciences, Oakland University William Beaumont School of Medicine, Rochester, MI, USA. An overview of the antimicrobial resistance mechanisms of bacteria. AIMS Microbiol. 2018;4(3):482–501. doi:10.3934/microbiol.2018.3.482

5.Souque C, González Ojeda I, Baym M. From Petri Dishes to Patients to Populations: Scales and Evolutionary Mechanisms Driving Antibiotic Resistance. Annu Rev Microbiol. 2024;78:361–82. doi:10.1146/annurev-micro-041522-102707

6.Evaluation of the national Cleanyourhands campaign to reduce Staphylococcus aureus bacteraemia and Clostridium difficile infection in hospitals in England and Wales by improved hand hygiene: four year, prospective, ecological, interrupted time series stu… | The BMJ [Internet]. [cited 2026 Oct 24]. Available from: https://www.bmj.com/content/344/bmj.e3005

7.Jarlier V, Trystram D, Brun-Buisson C, Fournier S, Carbonne A, Marty L, et al. Curbing Methicillin-Resistant Staphylococcus aureus in 38 French Hospitals Through a 15-Year Institutional Control Program. Arch Intern Med. 2010 Mar 22;170(6):552–9. doi:10.1001/archinternmed.2010.32  

8.Waterlow NR, Cooper BS, Robotham JV, Knight GM. Antimicrobial resistance prevalence in bloodstream infection in 29 European countries by age and sex: An observational study. PLOS Med. 2024 Mar 14;21(3):e1004301. doi:10.1371/journal.pmed.1004301