Streptococci vancomycin

Patients with PVE caused by penicillin-susceptible strains of viridans streptococci require treatment for 6 weeks with penicillin G or ceftriaxone with or without gentamicin during the initial 2 weeks of therapy. However, if the organism demonstrates less susceptibility to penicillin (MIC greater than 0.12 mcg/mL), a combination therapy with penicillin G or ceftriaxone plus gentamicin should be given for the entire 6 weeks. Vancomycin remains the primary alternative if the patient is allergic to (l-lactams (e.g., penicillins, cephalosporins, etc.). 

Vancomycin and teicoplanin display excellent activity against staphylococci and streptococci, but because of the wide availability of equally effective and less toxic drugs, they are second-line drugs in the treatment of most infections. As antistaphylococcal agents they are less effective than 3-lactam cephalosporin antibiotics, such as nafciUin and cefazoUn. They have attained much wider use in recent years as a consequence of the emergence of methicUlin-resistant S. aureus (MRSA) infections, in particular the growing importance of Staphylococcus epidermidis infections associated with the use of intravascular catheters and in patients with peritonitis who are on continuous ambulatory peritoneal dialysis. 

Viridans streptococci Penicillin Cephalosporin (first- or third-generation),2 vancomycin... 

Subacute Viridans streptococci, enterococci Penicillin + gentamicin Vancomycin + gentamicin... 

Answer B (Amoxicillin). The multiple extractions can lead to bacteremia while the mitral valve stenosis and cardiac insufficiency place him at risk for developing endocarditis. The present American Heart Association guidelines indicate amoxicillin (3 gm 1 hour prior to procedure and 1.5 gm 6 hours after original dose.) Vancomycin would only be appropriate if the patient was allergic to penicillins. Tetracycline and cotrimoxazole are bacteriostatic and not effective against the viridans group of Streptococci, the usual causative organism. Imipenem is also inappropriate since its spectrum is too broad. 

Vancomycin, daptomycin or linezolid (to cover staphylococci including methicillin-resistant Staphylococcus aureus (MRSA), streptococci and enterococci) plus metronidazole (to cover anaerobes) plus gentamicin, ciprofloxacin, ceftazidime or aztreonam (to cover Gram-negative organisms including Pseudomonas). 

Some streptococci have developed a different mechanism of acquired resistance to penicillin drugs. These bacteria have altered transpeptidases (also known as penicillin-binding proteins) that no longer bind penicillin, and thus peptidoglycan synthesis is not disrupted. This mechanism of resistance is found in Streptococcus pneumoniae. Estimates of penicillin-resistant S. pneumoniae in the United States range from 25% to 66%, including strains recovered from ocular and periocular infections. Many isolates of penicillin-resistant S.pneumoniae also are resistant to the cephalosporins, macrolides, and the older fluoroquinolones. Use of alternative antibiotics such as vancomycin is necessary for infections caused by penicillin-resistant isolates. 

Like the other drugs discussed in this section, vancomycin acts by inhibiting biosynthesis of the bacterial cell wall, specifically the mucopeptide portion of the peptidoglycan. It is highly active against the gram-positive cocci, staphylococci and streptococci, and C difficile. 

All enterococci causing endocarditis must be tested for antimicrobial susceptibility in order to select optimal therapy (see text). This table is for endocarditis due to gentamicin- or vancomycin-susceptible enterococci, viridans streptococci with a minimum inhibitory concentration of >0.5 mcg/mL, nutritionally variant viridans streptococci, or prosthetic valve endocarditis caused by viridans streptococci or Streptococcus bovis. Antibiotic dosages are for patients with normal renal function. 

Infection. Vancomycin (18)is a relatively small glycoprotein derived from Nocar-dia orientalis, which is well known for its activity against Gram-positive bacteria including Streptococci, Corynebacteria Clos-tridia. Listeria, and Bacillus. 

Vancomycin is the drug of choice against serious infections caused by methicihin-resistant strains of Staphylococcus aureus and coagulase-negative staphylococci [172]. It may also be used for treatment of infections by gram-positive organisms in penicillin-intolerant patients. Vancomycin has been extensively used to treat endocarditis caused by streptococci, enterococci and staphylococci. The empiric treatment of intravenous catheter sepsis and hemodialysis vascular access infection by vancomycin has led to a linear increase in its use in the last decade [173]. Oral vancomycin is efficacious in the treatment of Corynebacterium difficile-mediated diarrhea. Of major concern is the recent emergence of vancomycin-resistant enterococcus strains [174,175]. 

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