Microbial profile and biofilm formation of Pseudomonas aeruginosa from clinical samples at a tertiary care hospital in Nepal

In hospitals, where the most vulnerable patients go for care, a silent battle often plays out between medical teams and microscopic invaders. Among these invaders, a bacterium called Pseudomonas aeruginosa is a frequent and formidable opponent. It is a tough, adaptable organism found naturally in soil and water, but in a hospital setting, it can take hold in patients whose immune systems are weakened or whose bodies have been breached by surgery, tubes, or burns. This bacterium is dangerous not just because it causes infection, but because it has learned to hide and to resist the medicines doctors use to kill it. One of its most effective survival tricks is the ability to build a protective shield around itself, a slimy layer known as a biofilm. This shield acts like a fortress, making it much harder for antibiotics to penetrate and do their work. When the bacteria also develop the ability to produce special enzymes that break down drugs, the treatment options shrink rapidly, leaving doctors with fewer ways to save their patients.

Researchers at the B. P. Koirala Institute of Health Sciences in Dharan, Nepal, set out to understand exactly how strong this threat has become in their local hospital. Over the course of a year, they examined thousands of samples taken from patients, looking specifically for this bacterium. They wanted to know how often it appeared, where it was found, and most importantly, how well it could resist modern antibiotics. They also tested whether the bacteria were building those protective biofilms and if they were producing the specific enzymes that neutralize powerful drugs. The goal was to map the current landscape of this infection to help guide better treatment and prevent its spread.

The study began by processing a vast number of clinical samples, including fluids from the lungs, urine, pus from wounds, and swabs from surgical sites. Out of nearly 36,000 samples tested, about 3,600 came back positive for bacterial growth. Among these, the researchers found 178 cases of Pseudomonas aeruginosa. This meant the bacterium was present in roughly 5 percent of all positive cultures. The bacteria were found more often in patients who were already staying in the hospital than in those visiting as outpatients. The samples that yielded the most bacteria were pus from abscesses and swabs from wounds, followed by urine and sputum. The patients carrying these bacteria ranged widely in age, but the majority were adults between the ages of 14 and 60.

Once the bacteria were identified, the team tested how they reacted to a variety of antibiotics. They exposed the bacteria to common drugs and watched to see if the medicines could stop their growth. The results showed a mixed picture. The bacteria were still quite sensitive to a group of powerful drugs called carbapenems, with about three-quarters of the samples responding well to imipenem and meropenem. They were also fairly sensitive to other drugs like ciprofloxacin and tobramycin. However, the bacteria showed much stronger resistance to other common treatments. More than half of the samples did not respond to piperacillin-tazobactam, and resistance was also high for ceftazidime and cefepime. This pattern suggests that while some strong weapons still work, many standard antibiotics are losing their effectiveness against this specific germ in this region.

The researchers then looked deeper to see if the bacteria were using specific chemical tools to fight back. They tested for three types of enzymes that bacteria produce to destroy antibiotics. About a quarter of the bacteria were found to produce enzymes that break down a broad class of drugs called extended-spectrum cephalosporins. Nearly 30 percent of the samples produced enzymes capable of destroying carbapenems, the last line of defense for many serious infections. Within that group, about 18 percent were producing a specific type of enzyme called a metallo-beta-lactamase, which is particularly effective at neutralizing the strongest available drugs. These findings indicate that a significant portion of the bacteria in the hospital are equipped with sophisticated chemical defenses that render many treatments useless.

Perhaps the most striking finding of the study was the prevalence of biofilms. The researchers used two different methods to check if the bacteria were building these protective layers. They found that more than 80 percent of the bacteria samples were capable of forming biofilms. When they compared the bacteria that built these shields to those that did not, a clear pattern emerged. The bacteria that formed biofilms were significantly more likely to be resistant to several key antibiotics, including gentamicin, amikacin, ciprofloxacin, and meropenem. This suggests that the act of building a biofilm is closely linked to the bacteria's ability to survive drug treatment. The bacteria that formed these communities were harder to kill, regardless of the specific antibiotic used.

The study concludes that Pseudomonas aeruginosa in this hospital is a growing challenge. The combination of high rates of drug resistance and the widespread ability to form protective biofilms makes treating infections increasingly difficult. The researchers note that while their findings are specific to one hospital, they highlight a critical need for better management of antibiotic use and stricter infection control measures. By understanding which drugs still work and recognizing the role of biofilms in resistance, medical teams can make more informed choices. The authors emphasize that continuous monitoring is essential to track these changes and ensure that patients receive the most effective care possible. Without such vigilance, the window for successful treatment may close further as these resilient bacteria continue to adapt.