Oxacillin-Resistant Staphylococcus aureus (ORSA) is a strain of the common Staphylococcus aureus bacteria that has developed the ability to withstand certain antibiotics. This resistance includes oxacillin, a penicillin-like antibiotic, and also extends to other beta-lactam antibiotics like methicillin, cephalosporins, and carbapenems. ORSA infections are more challenging to treat than those caused by antibiotic-susceptible Staphylococcus aureus strains.
Understanding Resistance
Antibiotic resistance in ORSA means the bacteria has changed, rendering certain medications ineffective. Unlike typical Staphylococcus aureus strains susceptible to oxacillin, ORSA has acquired specific genetic material allowing it to evade the antibiotic’s action. The primary mechanism involves the acquisition of a gene called mecA, located on a mobile genetic element known as the Staphylococcal Cassette Chromosome mec (SCCmec).
The mecA gene encodes for an altered penicillin-binding protein, PBP2a. This modified protein has a reduced affinity for beta-lactam antibiotics, including oxacillin. Even when these antibiotics are present, PBP2a can continue to build the bacterial cell wall, allowing the bacteria to survive and multiply.
How It Spreads
ORSA primarily spreads through direct person-to-person contact, particularly skin-to-skin contact. It can also be transmitted indirectly by touching contaminated surfaces or objects, such as towels, razors, or shared athletic equipment. The bacteria can survive on surfaces for varying periods, contributing to its spread.
Healthcare settings, including hospitals, nursing homes, and dialysis centers, are common sites for ORSA transmission due to the close proximity of vulnerable individuals and frequent contact with medical equipment. Transmission also occurs in community settings, such as gyms, schools, locker rooms, and crowded living spaces. Poor hygiene practices and shared personal items can facilitate its spread.
Recognizing Infections
ORSA infections most frequently manifest as skin and soft tissue infections. These often appear as red, swollen, painful areas on the skin that might feel warm to the touch. Common presentations include boils, which are pus-filled lumps, or abscesses, which are collections of pus under the skin.
Other signs can include pus-filled blisters, known as impetigo, or cellulitis, a spreading skin infection characterized by redness and tenderness. If these skin symptoms are present, particularly if they are worsening rapidly, accompanied by fever, or if the affected area becomes increasingly painful, seeking medical attention is advisable. ORSA can also cause more serious infections, such as pneumonia, bloodstream infections, or bone and joint infections, which may present with more generalized symptoms.
Managing and Preventing Infections
Diagnosis of ORSA infections involves collecting a sample, such as pus from a skin lesion or blood, for bacterial culture. This sample is sent to a laboratory to grow the bacteria and perform sensitivity testing to determine which antibiotics are effective against the specific strain.
Treatment for ORSA infections differs from susceptible Staphylococcus aureus infections because standard antibiotics like oxacillin are ineffective. Healthcare providers often use alternative antibiotics, such as vancomycin for severe infections, or other options like clindamycin, doxycycline, or trimethoprim-sulfamethoxazole for milder cases, depending on the infection’s severity and local resistance patterns. It is important to complete the entire course of prescribed antibiotics, even if symptoms improve, to ensure the infection is fully eradicated and to minimize the risk of developing further resistance. Proper wound care, including draining abscesses when indicated, also plays a significant role in managing these infections.
Preventing ORSA infections involves several practical measures. Consistent hand hygiene, including frequent and thorough handwashing with soap and water or using an alcohol-based hand sanitizer, is a primary defense. Avoiding the sharing of personal items like towels, razors, and athletic gear can also reduce transmission. Regularly cleaning and disinfecting frequently touched surfaces in shared environments, such as gym equipment or doorknobs, further helps to limit the spread of the bacteria.
Any cuts, scrapes, or wounds should be kept clean and covered with a clean, dry bandage to prevent bacteria from entering or spreading. If suspicious skin lesions appear, especially those that are red, swollen, painful, or draining pus, prompt medical evaluation is recommended.