Harrison's Internal Medicine Chapter 127. Treatment and Prophylaxis of Bacterial Infections
Treatment and Prophylaxis of Bacterial Infections: Introduction
The development of vaccines and drugs that prevent and cure bacterial infections was one of the twentieth century's major contributions to human longevity and quality of life. Antibacterial agents are among the most commonly prescribed drugs of any kind worldwide. Used appropriately, these drugs are lifesaving.
Duration of Therapy and Treatment Failure
Until recently, there was little incentive to establish the most appropriate duration of treatment; patients were instructed to take a 7- or 10-day course of treatment for most common infections. A number of recent investigations have evaluated shorter durations of therapy, especially in patients with communityacquired pneumonia. Table 127-10 lists common bacterial infections for which treatment duration guidelines have been established or for which there is sufficient clinical experience to establish treatment durations.
Status of the Host
Various host factors must be considered in the devising of antibacterial chemotherapy. The host's antibacterial immune function is of importance, particularly as it relates to opsonophagocytic function. Since the major host defense against acute, overwhelming bacterial infection is the polymorphonuclear leukocyte, patients with neutropenia must be treated aggressively and empirically with bactericidal drugs for suspected infection (Chap. 82). Likewise, patients who have deficient humoral immunity (e.g.
Site of Infection
The location of the infected site may play a major role in the choice and dose of antimicrobial drug. Patients with suspected meningitis should receive drugs that can cross the blood-CSF barrier; in addition, because of the relative paucity of phagocytes and opsonins at the site of infection, the agents should be bactericidal. Chloramphenicol, an older drug but occasionally useful in the treatment of meningitis, is bactericidal for common organisms causing meningitis (i.e.
Principles of Antibacterial Chemotherapy
The choice of an antibacterial compound for a particular patient and a specific infection involves more than just a knowledge of the agent's pharmacokinetic profile and in vitro activity.
Adverse drug reactions are frequently classified by mechanism as either dose-related ("toxic") or unpredictable. Unpredictable reactions are either idiosyncratic or allergic. Dose-related reactions include aminoglycoside-induced nephrotoxicity, linezolid-induced thrombocytopenia, penicillin-induced seizures, and vancomycin-induced anaphylactoid reactions. Many of these reactions can be avoided by reducing dosage in patients with impaired renal function, limiting the duration of therapy, or reducing the rate of administration.
Inhibition of Cell-Wall Synthesis
One major difference between bacterial and mammalian cells is the presence in bacteria of a rigid wall external to the cell membrane. The wall protects bacterial cells from osmotic rupture, which would result from the cell's usual marked hyperosmolarity (by up to 20 atm) relative to the host environment. The structure conferring cell-wall rigidity and resistance to osmotic lysis in both gram-positive and gram-negative bacteria is peptidoglycan, a large, covalently linked sacculus that surrounds the bacterium.
Inhibition of Protein Synthesis
Most of the antibacterial agents that inhibit protein synthesis interact with the bacterial ribosome. The difference between the composition of bacterial and mammalian ribosomes gives these compounds their selectivity.
Aminoglycosides Aminoglycosides (gentamicin, kanamycin, tobramycin, streptomycin, neomycin, and amikacin) are a group of structurally related compounds containing three linked hexose sugars. They exert a bactericidal effect by binding irreversibly to the 30S subunit of the bacterial ribosome and blocking initiation of protein synthesis.
To be effective, concentrations of an antibacterial agent must exceed the pathogen's MIC. Serum antibiotic concentrations usually exceed the MIC for susceptible bacteria, but since most infections are extravascular, the antibiotic must also distribute to the site of the infection. Concentrations of most antibacterial agents in interstitial fluid are similar to free-drug concentrations in serum.
(BQ) Part 1 book "Transplant infections" presents the following contents: Introduction to transplant infections, risks and epidemiology of infections after transplantation, specific sites of infection, bacterial infections.
Neonatal sepsis still remains a significant cause of morbidity and mortality in the newborn, particularly in preterm, low birth weight infants. Despite advances in neonatal care, overall case-fatality rates from sepsis may be as high as 50%. Clinical signs of bacterial infection are vague and non-specific, and up to now there exists no easily available, reliable marker of infection despite a large bulk of studies focussing on inflammatory indices in neonatology. Every neonatologist is faced with the uncertainty of under- or over- diagnosing bacterial infection.
The level of suspicion of infections with certain organisms should depend on the type of cancer diagnosed (Table 82-3). Diagnosis of multiple myeloma or CLL should alert the clinician to the possibility of hypogammaglobulinemia. While immunoglobulin replacement therapy can be effective, in most cases prophylactic antibiotics are a cheaper, more convenient method of eliminating bacterial infections in CLL patients with hypogammaglobulinemia.
Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài:
Rapid label-free identification of mixed bacterial infections by surface plasmon resonance
Harrison's Internal Medicine Chapter 130. Streptococcal and Enterococcal Infections
Streptococcal and Enterococcal Infections: Introduction
Many varieties of streptococci are found as part of the normal flora colonizing the human respiratory, gastrointestinal, and genitourinary tracts. Several species are important causes of human disease. Group A Streptococcus (GAS, S.
Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học Critical Care giúp cho các bạn có thêm kiến thức về ngành y học đề tài: Procalcitonin as a marker of bacterial infection in the emergency department: an observational study...
The development of vaccines and drugs that prevent and cure bacterial infections was one of the twentieth century's major contributions to human longevity and quality of life. Antibacterial agents are among the most commonly prescribed drugs of any kind worldwide. Used appropriately, these drugs are lifesaving. However, their indiscriminate use drives up the cost of health care, leads to a plethora of side effects and drug interactions, and fosters the emergence of bacterial resistance, rendering previously valuable drugs useless. ...
Upper Respiratory Infections: Treatment Antibiotics have no role in the treatment of uncomplicated nonspecific URI. In the absence of clinical evidence of bacterial infection, treatment remains entirely symptom-based, with use of decongestants and nonsteroidal antiinflammatory drugs. Other therapies directed at specific symptoms are often useful, including dextromethorphan for cough and lozenges with topical anesthetic for sore throat. Clinical trials of zinc, vitamin C, echinacea, and other alternative remedies have revealed no consistent benefit for the treatment of nonspecific URI.
Clinical Manifestations Most cases of acute sinusitis present after or in conjunction with a viral URI, and it can be difficult to discriminate the clinical features of one from the other. A large proportion of patients with colds have sinus inflammation, although bacterial sinusitis complicates only 0.2–2% of these viral infections. Common presenting symptoms of sinusitis include nasal drainage and congestion, facial pain or pressure, and headache.
Bacterial Infections In the first month after hematopoietic stem cell transplantation, infectious complications are similar to those in granulocytopenic patients receiving chemotherapy for acute leukemia (Chap. 82). Because of the anticipated 1- to 3week duration of neutropenia and the high rate of bacterial infection in this population, many centers give prophylactic antibiotics to patients upon initiation of myeloablative therapy. Quinolones decrease the incidence of gram-negative bacteremia among these patients.