Tags: carbapenems

Important Anaerobes

Essentials of Diagnosis Foul odor of draining purulence Presence of gas in tissues No organism growth on aerobic culture media Infection localized in the proximity of mucosal surface Presence of septic thrombophlebitis Tissue necrosis and abscess formation Association with malignancies (especially intestinal) Mixed organism morphologies on Gram stain General Considerations Epidemiology and Ecology Anaerobic bacteria are the predominant component of the normal microbial flora of the human body. The following sites harbor the vast majority of them: Skin Mostly gram-positive bacilli such as Propionibacterium acnes Gastrointestinal tract In the oral cavity Prevotella spp., Porphyromonas spp., Peptostreptococcus spp., microaerophillic streptococci, and Fusobacterium spp. are the most important anaerobes found; they significantly outnumber […]

Toxin-Mediated Infections

TETANUS Tetanus is a disease of global incidence produced by the toxin of Clostridium tetani. The risk of acquiring it increases in people > 60 years of age and in neonates, especially in Third World countries where poor sanitary conditions predispose to umbilical stump contamination. Immunization campaigns have played a crucial role in bringing about the observed decreasing incidence in the United States. The pathogenesis of tetanus involves the absorption of preformed toxin, or, less commonly, invasion of toxin-producing organisms from contaminated wounds; it may complicate surgical wounds colonized with C tetani. Incubation periods vary depending on the portal of entry. The toxin tetanospasmin blocks the transmission of inhibitory neurons, which […]

Infection in Patients With Aids

Paeruginosa infections may occur in patients with AIDS. Risk factors for infection include a CD4 count of < 100 cells/mL3, neutropenia or functional neutrophil defects, intravascular catheterization, hospitalization, and prior use of antibiotics including ciprofloxacin or trimethoprim-sulfamethoxazole. Many cases are community acquired. Bacteremia is common, and the lung or an intravenous catheter is the most frequent portal of entry. An impaired ability to mount immunotype-specific antibodies to Pseudomonas lipopolysaccharide antigen has been noted in HIV-positive individuals with bacteremia. Relapse is frequent, and mortality is high, 40%. Pneumonia is usually associated with cavitation and a high relapse rate. Bacterial sinusitis is an important and frequently undetected illness in HIV-positive individuals, and P […]

Other Bacillus Species

General Considerations Bacillus species other than B anthracis are found in soil, decaying organic matter, and water, but they are rare causes of disease. Risk factors associated with Bacillus infection include the presence of intravascular catheters, intravenous drug use, sickle cell disease, and immunosuppression — particularly corticosteroid use, transplantation, AIDS, and neutropenia secondary to chemotherapy. The hardy growth characteristics of Bacillus spp. cause them to arise as common laboratory contaminants; however, they are also capable of causing severe invasive illness. B cereus and B subtilis are the most frequent Bacillus spp. to cause invasive infection. Pneumonia, meningoencephalitis, endocarditis (native and prosthetic valves), and intravascular catheter infection have been well described. High-grade […]

Enterococci

Essentials of Diagnosis Gram stain shows gram-positive cocci that occur in singles, pairs, and short chains; recovery of microorganism from culture of blood or other sterile source. Lancefield group D antigen. Clinical isolates: Enterococcus faecalis, 74%; E faecium, 16%; other species, 10%. Facultative anaerobes grow in 6.5% NaCl at pH 9.6 and at temperatures ranging from 10 °C to 45 °C, and grow in the presence of 40% bile salts and hydrolyze esculin and L-pyrrolidonyl-ß-naphthylamide. Infections typically of a gastrointestinal or genitourinary origin. The most common infections are urinary tract infection, bacteremia, endocarditis, intra-abdominal and pelvic infection, and wound and soft tissue infection. General Considerations Epidemiology Enterococci are able to grow […]

Specific Anti-Infective Agents

Antibiotics Before prescribing a specific antibiotic, clinicians should be able to answer these questions: How does the antibiotic kill or inhibit bacterial growth? What are the antibiotic's toxicities and how should they be monitored? How is the drug metabolized, and what are the dosing recommendations? Does the dosing schedule need to be modified in patients with renal dysfunction? What are the indications for using each specific antibiotic? How broad is the antibiotic's antimicrobial spectrum? How much does the antibiotic cost? Clinicians should be familiar with the general classes of antibiotics, their mechanisms of action, and their major toxicities. The differences between the specific antibiotics in each class can be subtle, often […]

Urinary Tract Infections and Prostatitis

Definition Infections of the urinary tract represent a wide variety of clinical syndromes including urethritis, cystitis, prostatitis, and pyelonephritis. A urinary tract infection is defined as the presence of microorganisms in the urine that cannot be accounted for by contamination. The organisms have the potential to invade the tissues of the urinary tract and adjacent structures. Lower tract infections include cystitis (bladder), urethritis (urethra), prostatitis (prostate gland), and epididymitis. Upper tract infections involve the kidney and are referred to as pyelonephritis. Uncomplicated urinary tract infections are not associated with structural or neurologic abnormalities that may interfere with the normal flow of urine or the voiding mechanism. Complicated urinary tract infections are […]

Infectious disorders

Infectious diseases comprise those illnesses that are caused by microorganisms or their products. Clinical manifestations of infection occur only when sufficient tissue injury has been inflicted directly by microbial products (e.g., endotoxins and exotoxins), or indirectly by host responses (e.g., cytokines and hydrolytic enzymes released by polymorphonuclear leukocytes). Despite the extraordinary recent advances that have occurred in therapeutics for infectious diseases, a number of basic principles should be followed to prescribe antimicrobials and vaccines is an optimal manner. This chapter addresses the broader issues of treating infectious diseases and provides a number of practical clinical examples to demonstrate rational therapeutics. A rational therapeutic strategy in the management of proved or suspected […]

Antimicrobial therapy: general principles

A wide variety of antimicrobial agents is available to treat established infections caused by bacteria, fungi, viruses, or parasites. This section will cover the general principles of antimicrobial therapy and will also include illustrative clinical problems to emphasize proper decision-making in using antimicrobials. Determinants of Antimicrobial Efficacy Measurement of antimicrobial activity in vitro Susceptibility testing is indicated for any bacterial pathogen warranting chemotherapy. Drugs that irreversibly destroy the ability of an organism to replicate, and perhaps in the process destroy the structural integrity of the organism, are microbicidal. Drugs that reversibly impair replicating ability, with this function being restored when drug concentrations fall below critical inhibitory levels, are microbiostatic. In quantitative […]

Toxicity of Antimicrobial Therapy

Mechanisms of toxicity The mechanisms associated with common adverse reactions to antimicrobials include dose-related toxicity that occurs in a certain fraction of patients when a critical plasma concentration or total dose is exceeded, and toxicity that is unpredictable and mediated through allergic or idiosyncratic mechanisms. For example, certain classes of drugs such as the aminoglycosides are associated with dose-related toxicity. In contrast, the major toxicity of the penicillins and cephalosporins is due to allergic reactions. These differences are explained in part by the relative ability of specific drugs to inhibit enzymatic pathways in the host versus their stimulation of specific immune response. Not included in these lists is mention of the […]

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