Recent research has found cases of the drug-resistant bacterial infection known as methicillin-resistant Staphylococcus aureus (MRSA) outside of hospitals have increased by 90% in the US since 1999.

Researchers at Princeton University, New Jersey found two new strains of MRSA in patients different from the strains normally found in hospitals, according to Reuters.

The study conducted on lab tests after collecting data from 300 microbiology laboratories in the US found that during 1999 and 2006, the percentage of S. aureus infections resistant to methicillin has increased annually in outpatients admitted to US hospitals.

The increase is mainly due to community-acquired MRSA strains, which have increased more than 33% annually, according to the report.