Tags: Cefazolin

Toxin-Mediated Infections

1. 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, …

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Streptococcus Dysgalactiae Subspp. Equisilimis & Streptococcus Zooepidemicus:Clinical Syndromes

1. PHARYNGITIS The symptoms of pharyngitis caused by these organisms mimic those of S pyogenes pharyngitis (Box 50-1; see also site). Poststreptococcal glomerulonephritis has been described following S dysgalactiae subspp. equisimilis and S zooepidemicus pharyngitis. Notably, however, no antistreptolysin O antibody response will be detected as these organisms do not produce streptolysin O. S dysgalactiae subspp. equisimilis pharyngitis has been associated with sterile reactive arthritis. Acute rheumatic fever, however, has not been described in association with S dysgalactiae subspp. equisimilis and S zooepidemicus pharyngitis. 2. SKIN & SOFT TISSUE INFECTIONS Cellulitis, wound infections, pyoderma, erysipelas, impetigo, and cutaneous ulcers can be caused by these organisms (see site). Breaches in skin integrity …

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Other Gram-Positive Cocci

VIRIDANS GROUP STREPTOCOCCI, INCLUDING ABIOTROPHIA DEFECTIVA & ABIOTROPHIA ADJACENS Essentials of Diagnosis • Facultatively anaerobic gram-positive cocci, catalase negative, coagulase negative. • a or ? hemolytic on blood agar. • Abiotrophia defectiva and Abiotrophia adjacens require pyridoxal or thiol group supplementation. • Streptococcus milleri group organisms often exhibit Lancefield antigens A, C, F, or G and often have a butterscotch odor. General Considerations A. Epidemiology. Viridans streptococci are part of the normal microbial flora of humans and animals and are indigenous to the upper respiratory tract, the female genital tract, all regions of the gastrointestinal tract, and, most significantly, the oral cavity. Clinically significant species that are currently recognized as belonging …

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Viridans Group Streptococci: Clinical Syndromes

1. ENDOCARDITIS Viridans streptococci have a strong association with bacterial endocarditis (see site) (Box 1). A defectiva and A adjacens were once an important cause of culture-negative endocarditis. However, current laboratory media and techniques enable these “nutritionally variant streptococci” to be identified more readily. 2. BACTEREMIA Viridans streptococci account for 2.6% of positive blood cultures reported from clinical laboratories; however, of these, only about one-fifth are thought to be clinically significant (the remainder are attributed to contamination or transient bacteremia). Viridans streptococci are, however, one of the leading causes of bacteremia in febrile neutropenic patients. Viridans streptococcal bacteremia in neutropenic patients usually occurs in association with aggressive cytoreductive therapy for acute …

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Streptococcus Pneumoniae

Essentials of Diagnosis • Most common infections include pneumonia, meningitis, sinusitis, and otitis media. • Predisposing factors include extremes of age (ie, infants and elderly) and underlying host defects in antibody, complement, and splenic function. • Transmission is human to human both in the community and nosocomially. • Pneumonia: productive cough, fever, chills, sweats, and dyspnea; lobar or segmental consolidation on chest x-ray; lancet-shaped gram-positive diplococci on Gram stain of sputum or growth of S pneumoniae from sputum, blood, or pleural fluid. • Meningitis: headache, stiff neck, fever, chill, and photophobia; nuchal rigidity, Kernig’s or Brudzinski’s sign; lancet-shaped gram-positive diplococci on Gram stain of cerebrospinal fluid (CSF), growth of S pneumoniae …

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Staphylococci

STAPHYLOCOCCUS AUREUS Essentials of Diagnosis • Large gram-positive cocci (0.7-1.5 um in size). • Colonies surrounded by zone of hemolysis on blood agar. • Colonies pigmented pale yellow to deep orange macroscopically. • Cluster in grapelike bunches microscopically. • Biochemically differentiated from streptococci by presence of the enzyme catalase. • Biochemically differentiated from other staphylococci by presence of the enzyme coagulase. • Analysis of chromosomal DNA can identify clonal isolates (useful in epidemiologic studies). General Considerations A. Epidemiology. Staphylococcus aureus colonizes the human skin, vagina, nasopharynx, and gastrointestinal tract. Colonization occurs shortly after birth and may be either transient or persistent. Published studies differ widely in estimates of the prevalence of …

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Cardiovascular Infections

Infective Endocarditis Potential Severity Acute endocarditis is life-threatening and often requires surgical intervention.Subacute endocarditis is an indolent disease that can continue for months. Epidemiology Infective endocarditis remains a serious but relatively uncommon problem. The incidence varies from series to series, being estimated to be as high as 11 per 100,000 population, and as low as 0.6 per 100,000 population. The exact incidence is difficult to ascertain, because the definitions for endocarditis differ in many surveys. A reasonable estimate is probably 2 per 100,000 population. This means that a primary care physician will encounter only 1 to 2 cases over a working lifetime. Endocarditis is more common in men than in women, …

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Intravascular Catheter-Related Infections

Potential Severity Can be life-threatening. Often prolong hospital stay, and can be complicated by metastatic lesions and bacterial endocarditis. Case 2 A 53-year-old white woman was admitted to the hospital with complaints of severe shaking during infusion of her hyperalimentation solution. She had been receiving intravenous hyperalimentation for 16years for a severe dumping syndrome that prevented eating by mouth. She had had multiple complications from her intravenous lines, including venous occlusions and line-associated bacteremia, requiring 24 line replacements. She had last been admitted 6 months earlier with Enter-obacter cloacae infection of her intravascular catheter requiring line removal andintravenous cefepime. Atthat time, a tunneled catheter had been placed in her leftsub-clavian vein, …

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Anti-Infective Agent Dosing

The characteristics that need to be considered when administering antibiotics include absorption (when dealing with oral antibiotics), volume of distribution, metabolism, and excretion. These factors determine the dose of each drug and the time interval of administration. To effectively clear a bacterial infection, serum levels of the antibiotic need to be maintained above the minimum inhibitory concentration for a significant period. For each pathogen, the minimum inhibitory concentration is determined by serially diluting the antibiotic into liquid medium containing 104 bacteria per millihter. Inoculated tubes are incubated overnight until broth without added antibiotic has become cloudy or turbid as a result of bacterial growth. The lowest concentration of antibiotic that prevents …

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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 …

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