Gram-Positive Bacterial Infections

Quinupristin-Dalfopristin: A New Antibiotic for Severe Gram-Positive Infections - Article

ABSTRACT: The steady increase in resistant organisms is related to the widespread use of antibiotics in community and hospital settings. New therapeutic options are needed, including treatments for infections caused by antibiotic-resistant gram-positive organisms. Quinupristin-dalfopristin, the first formulation of a distinct class of antibiotics known as the streptogramins, has activity against a range of gram-positive bacteria that are usually resistant to other agents, including vancomycin-resistant Enterococcus faecium. The pharmacodynamic (postantibiotic effect) and pharmacokinetic characteristics of quinupristin-dalfopristin allow dosing at eight- to 12-hour intervals. The safety profile of the formulation is generally favorable, with no demonstrable ototoxicity, nephrotoxicity, bone marrow suppression, or cardiovascular adverse effects. Reversible arthralgias, myalgias, and peripheral venous irritation are the formulation's major side effects. A potential for drug interactions exists because quinupristin-dalfopristin significantly inhibits the cytochrome P450-3A4 enzyme system. Quinupristin-dalfopristin has been shown to be effective in the management of documented severe infections caused by vancomycin-resistant E. faecium, nosocomial pneumonia, and infections related to the use of intravascular catheters.

Management of Bacterial Endocarditis - Article

ABSTRACT: Most cases of bacterial endocarditis involve infection with viridans streptococci, enterococci, coagulase-positive staphylococci or coagulase-negative staphylococci. The choice of antibiotic therapy for bacterial endocarditis is determined by the identity and antibiotic susceptibility of the infecting organism, the type of cardiac valve involved (native or prosthetic) and characteristics of the patient, such as drug allergies. Antibiotic therapies discussed in this report are based on recommendations of the American Heart Association. Treatment with aqueous penicillin or ceftriaxone is effective for most infections caused by streptococci. A combination of penicillin or ampicillin with gentamicin is appropriate for endocarditis caused by enterococci that are not highly resistant to penicillin. Vancomycin should be substituted for penicillin when high-level resistance is present. Resistance of enterococci to multiple antibiotics including vancomycin is becoming an increasing problem. Native valve infection by methicillin-susceptible staphylococci is treated with nafcillin, oxacillin or cefazolin. The addition of gentamicin for the first three to five days may accelerate clearing of bacteremia. Infection of a prosthetic valve by a staphylococcal organism should be treated with three antibiotics: oral rifampin and gentamicin and either nafcillin, oxacillin, cefazolin or vancomycin, depending on susceptibility to methicillin. Vancomycin is substituted for penicillin in patients with a history of immediate-type hypersensitivity to penicillin.

Common Infections in Older Adults - Article

ABSTRACT: Infectious diseases account for one third of all deaths in people 65 years and older. Early detection is more difficult in the elderly because the typical signs and symptoms, such as fever and leukocytosis, are frequently absent. A change in mental status or decline in function may be the only presenting problem in an older patient with an infection. An estimated 90 percent of deaths resulting from pneumonia occur in people 65 years and older. Mortality resulting from influenza also occurs primarily in the elderly. Urinary tract infections are the most common cause of bacteremia in older adults. Asymptomatic bacteriuria occurs frequently in the elderly; however, antibiotic treatment does not appear to be efficacious. The recent rise of antibiotic-resistant bacteria (e.g., methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococcus) is a particular problem in the elderly because they are exposed to infections at higher rates in hospital and institutional settings. Treatment of colonization and active infection is problematic; strict adherence to hygiene practices is necessary to prevent the spread of resistant organisms.

Linezolid: Its Role in the Treatment of Gram-Positive, Drug-Resistant Bacterial Infections - Article

ABSTRACT: While the choices available for the management of gram-positive, drug-resistant bacterial infections are becoming limited, antimicrobial resistance is becoming increasingly problematic because of the widespread overuse of antibiotics. Linezolid is a synthetic antibiotic belonging to a new class of antimicrobials called the oxazolidinones. Linezolid disrupts bacterial growth by inhibiting the initiation process of protein synthesis—a mechanism of action that is unique to this class of drugs. It is well absorbed with high bioavailability that allows conversion to oral therapy as soon as the patient is clinically stable. It has been approved for certain gram-positive infections including certain drug-resistant enterococcus, staphylococcus, and pneumococcus strains. It is generally well tolerated, with myelosuppression being the most serious adverse effect. As a nonselective inhibitor of monoamine oxidase, caution is recommended when used with adrenergic or serotonergic agents (e.g., tyramine, dopamine, pseudoephedrine, and selective serotonin reuptake inhibitors). Judicious use of this medication should help physicians treat patients with multidrug-resistant infections.

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