Superbugs on the Move: How Global Travel Spreads Antibiotic Resistance
"A case study highlights the critical role of international travel in the transmission of New Delhi metallo-β-lactamase (NDM-1), a dangerous antibiotic resistance mechanism."
Antibiotic resistance is one of the most pressing threats to public health today. Common infections are becoming increasingly difficult, and sometimes impossible, to treat as bacteria evolve to resist the drugs designed to kill them. Among these resistant bacteria, Enterobacteriaceae, particularly Escherichia coli (E. coli) and Klebsiella pneumoniae, are significant concerns. These bacteria are responsible for many hospital- and community-acquired infections.
Carbapenems, a class of antibiotics, are often the last line of defense against these multidrug-resistant bacteria. However, bacteria have developed carbapenemases, enzymes that inactivate these drugs, leading to a critical reduction in effective treatment options. The New Delhi metallo-β-lactamase (NDM-1) is one such enzyme that has emerged as a major threat, conferring resistance to a wide range of beta-lactam antibiotics, including carbapenems.
A recent case in Canada illustrates just how easily these resistant bacteria can spread across the globe. A patient who had been hospitalized in India returned to Canada and was found to be carrying an E. coli isolate with NDM-1. This case highlights the crucial role of international travel in the dissemination of antibiotic resistance, turning local infections into global threats.
Tracking the Global AMR Burden
The CDC collects antimicrobial-resistance data through multiple tracking systems and external sources, including electronic health data, to assess the burden of resistant germs. Its Antimicrobial Resistance & Patient Safety Portal displays data from the National Healthcare Safety Network, the Antimicrobial Resistance Laboratory Network, and other sources. WHO's 2025 global surveillance report provides adjusted 2023 AMR estimates for 93 infection type–pathogen–antibiotic combinations and tracks trends for 16 combinations from 2018 to 2023.
Limits of Conventional Detection
Culture-based approaches remain important for detecting antimicrobial resistance, but current clinical methods have limitations in sensitivity and turnaround time. They may also fail to detect all potential resistance genes. Traditional screening technologies such as disk diffusion and broth dilution are widely used, yet their reproducibility and speed can be limited.
The Emergence of NDM-1
NDM-1, or New Delhi metallo-beta-lactamase 1, was identified as a genetic element encoding multiple-resistance genes in Enterobacteriaceae. The enzyme was associated with resistance to nearly all antimicrobial treatments, while molecular studies showed that NDM-1-positive strains possessed potent resistance to carbapenems. Later research continued to examine how natural evolution and carbapenem overuse could affect NDM's ability to hydrolyze these drugs.
The Case: From India to Canada – A Chain of Resistance
In 2010, a 32-year-old man was admitted to a hospital in Mysore, India, with hyperglycemia and a urinary tract infection (UTI). Despite initial treatment with ciprofloxacin, his condition did not improve. He was then transferred to a hospital in Alberta, Canada, where he was diagnosed with prostatitis and pyelonephritis.
- Initial Infection: The patient contracted a UTI in India, which did not respond to initial antibiotic treatment.
- Transfer to Canada: The patient was transferred to a Canadian hospital for further treatment.
- Diagnosis of NDM-1 E. coli: An E. coli isolate from the patient was found to carry the NDM-1 gene, indicating carbapenem resistance.
- Treatment: The patient was successfully treated with ertapenem and fosfomycin, but the incident highlighted the risk of spreading resistant bacteria.
Plasmids and Resistant Strains
Recent research on Escherichia coli identified IncF plasmids and the bla CTX-M-27 locus as showing evidence of co-evolution. The study reported “Bridge” co-integrate structures flanked by IS26 in IncF plasmids. Other recent investigations have detected NDM carbapenemases in 30.7% of resistant Klebsiella pneumoniae strains from a tertiary hospital in Thrace, while VIM carbapenemases were detected in 7.68%.
Treatment Failure After Exposure
A report of a traveler returning to Canada described a urinary tract infection that did not improve after five days of ciprofloxacin, although the patient's diabetes mellitus was stabilized. Separately, investigators isolated the same bacterial clone in two patients in different countries without obvious contact. They concluded that medical care in the Indian subcontinent was a probable acquisition route and suggested that E. coli ST101 with NDM-1 might be widespread throughout the region.
Protecting Yourself and Preventing the Spread
The spread of antibiotic-resistant bacteria is a global issue that requires a multifaceted approach, including responsible antibiotic use, improved sanitation and hygiene practices, and international surveillance. Travelers can take several steps to protect themselves and prevent the spread of resistance. When traveling, especially in areas with high rates of antibiotic resistance, it’s crucial to practice good hygiene, including frequent handwashing, and to be cautious about food and water consumption. Avoid unnecessary antibiotic use and always follow the advice of healthcare professionals. By staying informed and taking proactive measures, we can all play a part in slowing the spread of antibiotic resistance and protecting public health.
New Options Against NDM
NDM-1 and its variants hydrolyze a broad range of beta-lactam antibiotics, including carbapenems, which have been described as a last treatment choice for some infections. At IDWeek 2025, discussion focused on the sharp rise of NDM-producing Enterobacterales, new oral antimicrobial options, and ongoing debates in infectious-disease practice. A 2026 review reported that one in six laboratory-confirmed bacterial infections shows resistance to at least one antibiotic treatment, while examining innovative strategies against AMR.
Unequal AMR Capacity
Antimicrobial resistance is driven in part by antibiotic misuse and overuse across human and animal sectors, contributing to multidrug-resistant pathogens and pressure on healthcare systems. Global policy responses in 2021–22 varied substantially by national income level, revealing disparities in AMR governance capacity. Lower scores in lower-income regions were associated with systemic challenges including less public-health spending and reduced access to clean water and sanitation.