Overprescribing of antibiotics was found to be the chief cause of the development of drug-resistant superbugs, fast growing bacteria that are posing an urgent threat in the United States, Fox News reported Monday.

A strain of antibiotic-resistant gonorrhea, a diarrhea-causing superbug and a microbial class known for being fast-growers, has been classified as urgent public-health threat in the United States.

The Centers for Disease Control and Prevention (CDC) said that a new report shows at least 2 million people develop serious bacterial infections that are antibiotic-resistant in the U.S., adding that at least 23,000 of the said figure die from the infections each year.

"For organism after organism, we're seeing this steady increase in resistance rates," Director of the CDC, Dr Thomas Frieden said in a telephone interview. "We don't have new drugs about to come out of the pipeline. If and when we get new drugs, unless we do a better job of protecting them, we'll lose those, also."

According to several studies, overprescribing of antibiotics is the leading cause of the antibiotic resistance of several strains of superbugs providing these pathogens the opportunity to outwit drugs used in treating them. Only a few new antibiotics have been developed to counter these superbugs in the past few decades, and only a handful of companies are currently working to create new antibiotics to replace the old ones.

Aside from the antibiotic-resistant gonorrhea strain, another urgent threat according to the new report released on Monday are C. difficile and a fatal class of enterobacteria or gut-residing microorganisms known as Carbapenem-Resistant Enterobacteriaceae (CRE).

The Daily Herald reported that the said study aims to provide as much information as possible about these drug-resistant superbugs so that their spread could be hampered and in order for scientists to preserve remaining drugs that still work against them.

The report stated that the United States is not the only one suffering from the threat of antibiotic resistance. The chief medical officer for England said last month that antibiotic resistance poses a "catastrophic health threat" following a report last year from the World Health Organization that identified a "superbug" strain of gonorrhea was found spreading to several European countries.

The new CDC report ranked the threat of drug-resistant superbugs into three categories: urgent, severe, and concerning. The ranking was based on several factors such as the superbugs health and economic implications, the total number of cases documented, the ease of their transmission, and the availability of effective antibiotics used to counter them.

Frieden said last March that among the top three threats deemed "urgent," CRE is considered as a "nightmare bacteria" due to the fact that even the strongest antibiotics cannot kill it.

The report also stated that CRE accounts for 9,300 healthcare-linked infections with the two most common types of CRE called carbapenem-resistant Klebsiella spp. and carbapenem-resistant E. coli account for 600 deaths yearly.

"For CRE, we're seeing increases from 1 state to 38 states in the last decade," Frieden said.

Meanwhile, C. difficile, the most common hospital-based infection or nosocomial infection in the U.S. landed the urgent threat rank because it has begun to resist antibiotics and due to the fact that it preys on antibiotic overuse.

C. difficile, which causes life-threatening diarrhea, spreads from person to person through contaminated equipment used by healthcare workers and visitors. It's infectious mechanism relies on the widespread use of antibiotics that kill protective bacteria or normal flora in the gut allowing C. difficile to thrive and flourish.