Emergence of Staphylococcus haemolyticus bloodstream infections in a neonatal intensive care unit: six-year evolution of infection prevention and control strategies

In the fragile world of a neonatal intensive care unit, where tiny, premature infants fight to survive, the environment itself can become a battlefield. These babies, often born weeks or even months early, rely on tubes and wires to breathe and receive nutrition because their own bodies are not yet ready. While these life-saving devices are essential, they also create pathways for invisible invaders to enter the bloodstream. Among the most common of these invaders are bacteria that normally live harmlessly on human skin but can turn deadly when they find their way inside a vulnerable body. One such bacterium, Staphylococcus haemolyticus, has recently become a major concern in hospitals across France. Unlike some bacteria that are easily killed by standard medicines, this particular strain has developed the ability to resist many different drugs, making it a stubborn and dangerous opponent for the medical teams trying to protect the smallest patients.

For six years, a team of researchers at a major hospital in Rennes, France, watched closely as this bacterium changed the landscape of their neonatal unit. They tracked every infection, studied the genetic makeup of the bacteria, and recorded every step the hospital took to stop the spread. What they found was a story of adaptation on both sides. A specific, highly resistant version of the bacteria, known as a lineage called ST29, arrived and took hold, becoming the most common cause of serious blood infections in the unit. In response, the hospital staff did not give up; instead, they built a complex, multi-layered defense system involving doctors, nurses, and even families. Yet, despite their best efforts and a significant improvement in basic hygiene practices, the bacteria did not disappear. The study reveals that once a tough, drug-resistant organism establishes itself in a high-risk environment, simply adding more rules is not enough to erase it.

The story begins in the neonatal intensive care unit at Rennes University Hospital, a place dedicated to caring for the most fragile newborns. Between 2020 and 2025, the medical team cared for 1,238 babies. Many of these infants were born very small, with nearly forty percent weighing less than 1,500 grams at birth. In such a setting, infections are a constant threat. The researchers focused on blood infections, which occur when bacteria enter the bloodstream, causing a systemic illness that can be fatal. They looked at thousands of blood samples taken from these babies to see which bacteria were causing the trouble. Over the six-year period, they identified 42 distinct episodes where Staphylococcus haemolyticus was the culprit. This bacterium, which is normally just a passenger on the skin, had become the leading cause of these dangerous infections, slowly replacing other, less dangerous types of bacteria that had previously been more common.

What made this situation particularly alarming was the nature of the bacteria itself. The researchers used advanced genetic sequencing to look at the DNA of the bacteria found in the babies. They discovered that almost all the infections were caused by a single family of bacteria, a genetic group known as ST29. This specific group was not just present; it was dominant. It appeared in the blood of the babies, but it was also found on the skin of the hospital staff and on the surfaces of the incubators and equipment. This strain was also multidrug-resistant, meaning it had learned to survive attacks from many different antibiotics. By 2022, nearly every new isolate of this bacterium showed resistance to a combination of powerful drugs, including cefoxitin, rifampicin, and trimethoprim. Before 2022, the bacteria were somewhat less resistant, but the shift was sharp and clear, marking the arrival of a much tougher enemy.

Faced with this rising threat, the hospital team launched a massive effort to regain control. They did not rely on a single solution but instead built a broad strategy that touched every part of the unit's daily life. They recorded every action they took, from training sessions and protocol changes to audits and equipment upgrades. In total, they implemented 184 different prevention measures. The team realized that they needed to target everyone, not just the doctors. Nurses were the most frequent focus of these new measures, followed by physicians and medical students, but the strategy also reached out to healthcare assistants, patient care technicians, and even the families of the babies. The goal was to create a culture where preventing infection was a shared responsibility.

One of the most visible changes was in hand hygiene. The researchers tracked how much alcohol-based hand rub was being used, a standard way to measure how often staff are cleaning their hands. In 2022, the unit was meeting only about one-third of the recommended usage targets. By 2025, after years of focused training, reminders, and audits, that number had soared to nearly 96 percent. This was a massive improvement in behavior. The hospital also tightened rules around how they managed the tubes and wires inside the babies, how they cleaned the incubators, and how they organized their staffing. They created a structured, multidisciplinary approach where different groups of workers had specific roles in keeping the environment safe.

Despite these heroic efforts and the dramatic rise in hygiene compliance, the bacteria did not vanish. The researchers used statistical tools to watch the rate of infections month by month. They saw that while the overall number of cases remained relatively low, there were still sudden spikes where the infection rate jumped far above the normal level. Even with the new, rigorous strategies in place, the team could not completely stop the bacteria from causing outbreaks. The data showed that the multidrug-resistant ST29 lineage had become deeply established in the unit. It was no longer just an occasional visitor; it was a resident that had found a way to persist.

The study suggests that the reason for this persistence lies in a combination of factors. The bacteria itself is incredibly adaptable. It can form sticky layers called biofilms on medical devices, which protect it from cleaning agents and antibiotics. It lives on the skin of the staff, providing a constant source of new infections. The environment of the neonatal unit, with its many tubes and wires, offers the bacteria endless opportunities to enter a baby's body. Furthermore, the very nature of caring for premature infants makes it difficult to remove these devices, which are often the entry point for the infection. The researchers found that even with a highly organized and well-funded prevention strategy, the biological resilience of the bacteria and the inherent risks of neonatal care created a situation where the infection could not be fully eradicated.

The findings from Rennes offer a sobering but necessary lesson for hospitals everywhere. It shows that when a drug-resistant bacterium takes root in a high-risk setting, it is not enough to simply add more rules or hope that better hygiene will solve the problem instantly. The battle is long and complex. The hospital in Rennes succeeded in building a strong, multidisciplinary defense that improved safety and reduced the frequency of some spikes, but the underlying threat remained. The study concludes that controlling such an established enemy requires a strategy that is not only sustained over many years but also constantly adapted to the changing behavior of the bacteria and the realities of the hospital environment. It is a reminder that in the fight against superbugs, victory is not always about total elimination, but about managing the risk with relentless, coordinated effort.