Prevalence, and Antimicrobial Resistance Profile of Escherichia coli O157:H7 Isolated from Human, Animal, and Environmental Samples in Ethiopia: A Systematic Review and Meta-Analysis

Imagine a microscopic traveler that lives quietly in the gut of cattle and other grazing animals. This traveler is a specific type of bacteria called Escherichia coli O157:H7. While most bacteria in our gut are harmless or even helpful, this particular strain carries a dangerous payload: potent toxins that can cause severe illness in humans. When people consume food or water contaminated with the bacteria, or come into close contact with infected animals, they can develop painful stomach cramps, bloody diarrhea, and in the worst cases, life-threatening kidney failure. The bacteria does not respect the boundaries between species; it moves freely from the soil and water to the livestock, and from there to the food we eat and the people who handle it. In a country like Ethiopia, where livestock farming is central to daily life and the distance between humans and animals is often very small, this invisible traveler finds many opportunities to spread.

For years, scientists in Ethiopia have been hunting for this bacteria in different places—checking the stool of sick people, swabbing the hides of cattle, and testing the water in rivers and wells. But these investigations were scattered, like pieces of a puzzle left in separate boxes. Some studies looked only at farms, others only at hospitals, and each used slightly different methods to find the germ. No one had ever gathered all these pieces together to see the full picture of how common the bacteria is across the entire country, or to understand how well the medicines used to treat it still work. Without this big picture, it is difficult to know how serious the threat really is or how to stop it from moving between animals and people.

To solve this, a team of researchers from universities and health institutions across Ethiopia decided to bring all the available evidence together. They did not go out to collect new samples themselves. Instead, they acted as investigators of existing research, searching through thousands of scientific reports published over a decade. They looked for any study conducted in Ethiopia between 2015 and 2025 that tested for this specific bacteria in humans, animals, or the environment. After carefully checking the quality of each report and ensuring the data was reliable, they selected fifty-two studies that met their strict standards. These studies covered a vast number of samples, representing a wide cross-section of the country, from the bustling markets of the capital to rural farming communities in the highlands and the lowlands.

The researchers then combined the data from all these studies to calculate a single, national estimate. They found that the bacteria is indeed present in Ethiopia, but it is not everywhere. On average, about 4.65 percent of the samples they looked at contained the bacteria. This means that if you were to test a hundred random samples from the mix of people, animals, and environments across the country, you would likely find the bacteria in roughly five of them. However, the story changes depending on where you look. The bacteria was most frequently found in human samples, appearing in nearly 8 percent of the tests. It was slightly less common in animals, showing up in about 5 percent of samples, and least common in environmental samples like water or soil, where it was found in roughly 3 percent. This pattern suggests that while the bacteria circulates in the environment and in livestock, it has found a way to reach people, likely through the food and water they consume.

The researchers also turned their attention to a second, equally critical question: if someone gets infected, can we still treat them with antibiotics? They analyzed data on how the bacteria responded to twenty-one different types of medicines. The results painted a worrying picture of resistance, which is when bacteria evolve to survive drugs that used to kill them. The bacteria showed a very high ability to resist certain older, common antibiotics. For instance, it was found to be resistant to erythromycin in nearly 90 percent of the cases where that drug was tested, and to ampicillin in about 83 percent of cases. This high level of resistance suggests that these medicines are no longer reliable for treating infections caused by this specific strain.

Yet, the story was not entirely bleak. The bacteria remained surprisingly vulnerable to some other drugs. Resistance to ciprofloxacin, a widely used antibiotic, was found in only about 8 percent of the cases. Similarly, resistance to ceftriaxone, another important medicine, was relatively low at around 14 percent. This indicates that while the bacteria has learned to defeat some of our most common weapons, other effective tools still exist. However, the researchers noted that the data varied significantly from one study to another, depending on the region and the methods used, which makes it hard to predict exactly what will happen in any single village or city.

The study also looked at whether the situation was getting worse over time. They checked if the bacteria was becoming more resistant to drugs as the years passed, but the data did not show a clear upward or downward trend. The resistance levels seemed to stay relatively steady, fluctuating without a distinct direction. This stability suggests that the problem is entrenched; the bacteria has already adapted to the current environment, and without changes in how we use medicines and manage our farms, it is unlikely to change on its own.

The researchers concluded that this bacteria remains a significant public health challenge in Ethiopia, moving silently between people, animals, and the environment. The fact that it is found in all three areas confirms that it cannot be stopped by treating sick people alone. The high rates of resistance to common drugs mean that if an infection occurs, doctors may find it difficult to cure. The solution, the authors argue, requires a coordinated approach that treats human health, animal farming, and environmental sanitation as a single, connected system. By improving hygiene in food production, managing water sources better, and using antibiotics more carefully, the spread of this dangerous traveler could be slowed, protecting both the livestock that feed the nation and the people who rely on them.