In 2014, doctors at University Hospital in Newark, New Jersey, had a seemingly benign case: a 76-year-old cancer survivor with a fever and complaints of pain in his side.

The man was suffering from a urinary tract infection (UTI), one of the most common types of infections.

The medical staff soon learned it was caused by E. coli bacteria, the most common cause of urinary tract infections.

But, researchers discovered nearly two years later, the man’s infection, or at least the E. coli bacteria responsible for it, was anything but common.

The specific bacterium contained two genes that made it immune to commonly used antibiotics, including a 50-year-old medication that’s been largely avoided since the 1970s, but is now back in rotation due to antibiotic resistance.

The case study, released Tuesday in the journal mBio, highlights the difficulties facing medical professionals and infectious disease experts in attempting to stay ahead of rapidly evolving bacteria.

This strain of E. coli, and many other bacteria like it, is responsible for 2 million infections in the United States every year. At least 23,000 of those are fatal, according to the Centers for Disease Control and Prevention (CDC).

Read more: Get the facts on E. coli infections »

An unusual patient

Researchers say the man was more prone to UTIs after a bout with prostate cancer and subsequent radiation therapy.

He also recently underwent a procedure that involves sliding a tiny camera-led scope into his urethra, which resulted in a perforated bladder. Hospital staff surgically inserted rubber tubes to drain his kidneys.

After lab testing, doctors found pus in the man’s urine, a sure sign of infection. Lab tests confirmed three different bacteria in his urine.

A sample from his tubes showed five different bacteria, including E. coli and methicillin-resistant Staphylococcus aureus, more commonly known as MRSA.

After six days of antibiotics, the man recovered and was sent home.

The sample eventually landed before Barry N. Kreiswirth, Ph.D., the founding director of the Public Health Research Institute (PHRI) at New Jersey Medical School in Newark.

Besides the man’s complicated medical history, further lab testing discovered some specific anomalies in the bacteria that caused his recurring UTIs.

The strain of E. coli carried the genes mcr-1 and blaNDM-5, and was resistant to several classes of common antibiotics that are widely used in both human and animal medicine.

Its plasmids — or parts of the cell that help it independently replicate — “were highly similar” to those reported in infections in China, according to researchers.

To make matters worse, researchers say the E. coli was a variant of ST405, a problematic strain of bacteria known for its disease causing potential.

Kreiswirth, who would become the case study’s senior author, says ST405 is frequently associated with UTIs that spread further in the community.

“The good news is that this did not cause a major outbreak of drug-resistant infection,” Kreiswirth said in a statement. “The bad news is that since this occurred two years ago, there are clearly other strains out there we haven't detected yet.”

Read more: Weakening antibiotics could result in 6,300 more infection-related deaths every year »

The rise of ‘nightmare bacteria’

The type of ST405 E. coli present in the New Jersey man held two other worrisome attributes.

It was resistant to carbapenem and colistin, two important antibiotics in the fight against resistant bugs.

Colistin was discovered, developed, and put on the market more than 50 years ago. Doctors decided not to use it starting in the 1970s because they found it did more harm than good. Now that bacteria are evolving around safer antibiotics, colistin is back in rotation.

The E. coli resistance to these different drugs occurred on different plasmids, meaning they could transfer their resistance to other bugs.

Recent scientific discoveries have shown that bacteria only need as little as a shared space to transfer these drug-resistant genes to one another, whether it be the stomach of a pig or the urinary tract and bladder of a 76-year-old man.

Despite the rapid pace of medical advancements, antibiotic resistance remains a major concern for medical professionals, healthcare administrators, and infectious disease specialists.

As bacteria learn to outsmart antibiotics in different ways, experts continually warn that current antibiotics be used judiciously and only when medically necessary.

As antibiotic development is rarely a profitable venture for a pharmaceutical company, the discovery and development of new antibiotics hasn’t kept pace with how quickly bacteria can develop resistance to these kinds of bugs.

One such bug, carbapenem-resistant Enterobacteriaceae (CRE), has been nicknamed the “nightmare bacteria.”

It’s a term Dr. Thomas Frieden, the head of the CDC, uses when describing CRE, which kills half of the people infected with it.

In May, a strain of CRE was found in the urine of a Pennsylvania woman. It was the first case of colistin-resistant bacteria reported in the United States, sounding an alarm for those who track these kinds of bacteria.

José R. Mediavilla, a research teaching specialist at PHRI and lead study author, said most mcr-1 cases appear to be happening in E. coli and should be watched carefully and reported thoroughly.

“These strains are probably already in the community and could spread further, essentially building toward a situation where you're going to have difficult if not impossible to treat urinary infections,” he said in a statement.

Read more: FDA requires specific reports on antibiotics in farm animals »