Antibiotics for Staph Strep Infections

Staphylococcus and streptococcus are spherical bacteria that can cause mild to severe infections, especially in immunocompromised individuals. While staph skin infections are common, this bacterium can also invade the bloodstream, urinary tract, lungs and heart. Strep throat, scarlet fever, pneumonia and meningitis are the most common strep infections. Antibiotics are the mainstay of treatment for both staph and strep infections.

Doctor writing a prescription Credit: LWA/Dann Tardif/Blend Images/Getty Images


Beta-lactam antibiotics, such as penicillin, ampicillin, methicillin, amoxicillin and amoxicillin-clavulanate, are the most common antibiotics used to treat staph and strep infections. These antibiotics act by disrupting the components of the bacterial cell wall, thereby causing cell leakage and cell death. Certain strains of staph and strep, however, produce an enzyme called beta-lactamase that can break down the beta-lactam antibiotics. Such strains are resistant to these antibiotics.

Beta-lactams can be administered orally or intravenously, depending on the condition of the patient and the common side effects include nausea, vomiting, stomach pain and headache. According to, however, some patients are allergic to penicillin and may experience rash, itchy skin, hives, and facial swelling due to penicillin therapy. It is important to seek immediate medical help if such reactions occur.


First generation cephalosporins such as cephaloridine, cephapirin, and cefazolin, and fourth generation cephalosporin such as cefepime, are highly effective against staph and strep. According to the University of Texas Medical Branch, however, strains of staph and strep that are resistant to beta-lactam antibiotics are resistant to cephalosporins as well. The toxicity and adverse reactions of cephalosporins are similar to those of beta-lactams.


Vancomycin is a glycopeptide antibiotic that interferes with the synthesis of the bacterial cell wall and genetic material. It is commonly used to treat infections caused by multi-drug resistant staph or strep species such as methicillin resistant Staphylococcus aureus, or MRSA. Vancomycin is available in tablet and injection form but is generally administered intravenously because it is poorly absorbed by the digestive tract. An upset stomach is the most common side effect. Per the the April 2003 edition of the "New England Journal of Medicine," the first vancomycin resistant strain of staph was identified in the U.S. in 1997 and the resistance has been steadily raising since then. This is a major cause of concern to the medical community.

Trimethoprim/ Sulfamethoxazole

Trimethoprim/ sulfamethoxazole, also known as co-trimoxazole, consists of two antibiotics — trimethoprim and sulfamethoxazole — that are effective against a variety of bacteria including staph and strep. The John Hopkins Point of Care Information Technology Center states that nearly all the strains of MRSA are susceptible to co-trimoxazole. Some patients, however, may be allergic to the sulfamethoxazole component of the drug. Only trimethoprim may be used to treat such patients.


Erythromycin, azithromycin and clarithromycin are the most common macrolide antibiotics that are used to treat infections caused by Staphylococcus aureus, Streptococcus pyogenes and Streptococcus pneumoniae. These drugs act by interfering with the protein synthesis mechanism of the bacteria. Azithromycin and clindamycin are well tolerated in the body, although large doses of erythromycin can cause gastrointestinal disturbances and transient toxicity.

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