A new study revealed that the numbers of children in the United States being exposed to serious, highly drug-resistant infections are on the rise.

The study, published in the Journal of the Pediatric Infectious Diseases Society, showed that rates of antibiotic resistance among samples of Pseudomonas aeruginosa, which were collected from pediatric patients nationwide, have increased over the last decade.

"Highly drug-resistant P. aeruginosa infections leave health care providers with limited--or sometimes no--antibiotic choices available, and these antibiotics are less safe and more toxic in children," explained study author Sumanth Gandra, MD, MPH, of the Center for Disease Dynamics, Economics & Policy, in a statement.

P. aeruginosa is a type of bacteria known as the common cause of healthcare-associated infections associated with significant morbidity and mortality.

For the study, the researchers analyzed data from a network of clinical microbiology laboratories serving about 300 hospitals across the country. The researchers focused their analysis on data obtained by testing P. aeruginosa isolates for susceptibility to several different types of antibiotics. The samples used in the study were taken from patients between the ages of 1 and 17 who were in outpatient, inpatient, intensive care unit, and long-term care settings from 1999 to 2012.

The researchers found that the proportions of isolates resistant to at least three classes of antibiotics have increased from 15.4 percent in 1999 to 26.0 percent in 2012. Furthermore, the proportions of bacterial strain resistant a class of antibiotics called carbapenems, which is considered to be the final line of defense against highly resistant infections, rose from 9.4 percent in 1999 to 20.0 percent in 2012. Pediatric patients aged 13 to 17 years old, living in Midwest and confined in intensive care units have the highest rate of drug resistant infections.

According to the Centers for Disease Control and Prevention, an estimated 51,000 health care-associated P. aeruginosa infections occur in adults and children in the U.S. each year, with over 6,000 of those infections resistant to multiple classes of antibiotics. About 400 die each year as a direct result of the infection.