Ans: d (Cephalexin) Ref: Harrison, 16th ed, p. 830; Tripathi, 6th ed, p. 733Enterococci are resistant to all cephalosporins; therefore this class of antibiotics should not be used for treatment of enterococcal infections. Usual treatment for enterococci is combination of penicillin or ampicillin with an aminoglycoside. If patient is penicillin allergic, vancomycin can be used instead.Treatment options for anti biotic-resistant enterococcal infectionsResistance PatternBeta-Lactamase productionRecommended TherapyGentamicin plus ampicillin/sulbactam, amoxicillin/clavulanate, imipenem, or vancomycinBeta-Lactam resistance, but no beta-lactamase productionGentamicin plus vancomycinHigh-level gentamicin resistanceStreptomycin-sensitive isolate: Streptomycin plus ampicillin or vancomycinStreptomycin-resistant isolate; No proven therapy(continuous-infusion ampicillin, prolonged treatment)Vancomycin resistanceAmpicillin plus gentamicinVancomycin and beta-lactam resistanceNo uniformly bactericidal drugs; linezolid (all enterococci) or quinupristin/dalfopristin ( only)Linezolid is a member of the oxazolidinediones, a new class of synthetic antimicrobials.It is active against gram-positive organisms including staphylococci, streptococci, enterococci, gram-positive anaerobic cocci, and gram-positive rods such as corynebacteria and Listeria monocytogenes.It is primarily a bacteriostatic agent except for streptococci, for which it is bactericidal. The principal toxicity of linezolid is hematologic-reversible and generally mild.Thrombocytopenia is the most common manifestationNeutropenia may also occur, most commonly in patients with a predisposition to or underlying bone mairow suppression.Linezolid is 100% bioavailable after oral administrationLinezolid is approved for vancomycin-resistant E.faeciuminfections; nosocomial pneumonia; community- acquired pneumonia; and skin infections, complicated or uncomplicated. It should be reserved for treatment of infections caused by multidrug-resistant gram-positive bacteria.TEICOPLANINTeicoplanin is a glycopeptide antibiotic that is very similar to vancomycin in mechanism of action and antibacterial spectrum. It can be given intramuscularly as well as intravenously.Teicoplanin has a long half-life (45-70 hours), permitting once-daily dosing.It is indicated in enterococcal endocarditis, MRSA and penicillin resistant streptococcal infections, osteomyelitis, as alternative to vancomycin.