Staphylococci--commonly called staph--cause a variety of human infections, including boils, skin infections (cellulitis), food poisoning, pneumonia, bone and blood stream infections and toxic shock syndrome. One species of staphylococci called Staphylococcus aureus, or S. aureus, causes most human infections. Antibiotics cure staph infections by killing the bacteria. The choice of antibiotic and the dosage depend on the site of the infection and the bacteria’s susceptibility to the drug.
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Nafcillin, Oxacillin and Dicloxacillin
The Centers for Disease Control and Prevention (CDC) reports the overwhelming majority of S. aureus bacteria are resistant to penicillin, which means the drug is not able to kill these bacteria. However, some strains are susceptible to killing by modified, penicillin-like antibiotics including nafcillin, oxacillin and dicloxacillin. Your doctor will determine the appropriate dose and duration of treatment based on the type of staph infection you have.
Cephalexin and Cefazolin
For people with penicillin allergy, the cephalosporin drugs, cephalexin and cefazolin, are alternatives to the penicillin-like antibiotics for S. aureus infections. Cefazolin is typically reserved for severe infections; it must be administered intravenously.
Tetracycline, Doxycycline and Minocycline
Tetracycline antibiotics, including doxycycline, minocycline and tetracycline, are prescribed for the treatment of skin and soft-tissue infections caused by S. aureus. Your doctor will probably take a sample of the bacteria from the infection site for a test called a bacterial culture and sensitivity. This test determines whether the causative bacteria are susceptible to elimination by the prescribed antibiotic.
Methicillin-resistant Staphylococcus aureus (MRSA) describes S. aureus strains that have developed resistance to all penicillins, including the modified penicillins. MRSA bacteria are typically also resistant to cephalosporin antibiotics. Their resistance to so many antibiotics makes MRSA challenging to cure. In a 2009 article published in the CDC journal “Emerging Infectious Diseases,” Eili Klein and his colleagues reported the percentage of community-acquired S. aureus infections that are caused by MRSA strains ranges from 52.4 percent to 58.5 percent.
Vancomycin is usually the treatment of choice for severe MRSA infections such pneumonia and bloodstream infections (sepsis). Hospitalization is commonly necessary with severe MRSA infections. Intravenous administration of vancomycin is the norm in these cases. Some MRSA strains have also developed vancomycin resistance; these strains are called VRSA--vancomycin-resistant Staphylococcus aureus. The modified penicillins, cephalosporins and vancomycin are ineffective against these highly resistant bacteria.
Clindamycin and Trimethoprim/Sulfamethoxazole
Clindamycin and trimethoprim/sulfamethoxazole are commonly used to treat MRSA skin and soft-tissue infections, including boils, skin abscesses, impetigo and cellulitis (infection of the soft tissue under the skin). Oral treatment is the norm; your doctor will determine the appropriate length of treatment based on the type of infection you have.
Linezolid and Daptomycin
Linezolid and daptomycin are effective for serious MRSA infections such as pneumonia, bone infections, sepsis and severe skin infections. Doctors typically use linezolid and daptomycin only when other antibiotic choices for MRSA are unlikely to be effective. These drugs are also effective against VRSA.