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Nonpneumococcal Streptococcal Infections and Rheumatic Fever

Classification and Identification of Streptococci Streptococci are gram-positive facultatively anaerobic, catalase-negative coccoid bacteria that grow in chains and colonize the skin and mucous membranes. When grown on blood agar plates, they may cause complete (β), incomplete (α), or no (γ) hemolysis. Using the Lancefield classification, hemolytic streptococci can be classified into types A through G based on acid-extractable carbohydrate antigens of cell wall material. Modern classification…

Streptococcus Pneumoniae Pulmonary Infections

Definition Streptococcus pneumoniae ( S. pneumoniae ) is a significant human bacterial pathogen and a major cause of community-associated bacterial infections. It is the most common bacterial cause of community acquired pneumonia (pneumococcal pneumonia; Chapter 85 ), sinusitis ( Chapter 394 ), and bacterial meningitis ( Chapter 381 ). Despite the availability of an effective vaccine, the burden of pneumococcal pneumonia remains high, particularly in older…

Staphylococcal Infections

Definition Staphylococci are well adapted as commensals and as pathogens. Coagulase-negative species constitute a significant proportion of the normal human cutaneous microbiome. Staphylococcus aureus , a coagulase-positive species, is a nasopharyngeal colonizer in a third of individuals, most of whom will not become infected. As a pathogen, S. aureus infections range in severity from relatively trivial skin infections to lethal invasive disease. Coagulase-negative species, which are…

Antibacterial Chemotherapy

Antibiotics provide a backbone for modern interventional medicine, in which surgery, central venous catheters, urinary catheters, implantable devices, and mechanical ventilation have become commonplace. These interventions support seriously ill patients, but they also give bacteria access to normally sterile areas. Therapies for cancer and immune-mediated disease often leave patients severely immunosuppressed. Bacterial infections in such patients are serious, and antibiotics provide critical life-saving support for such…

Approach to the Patient Before and After Travel

Prevention strategies and medical interventions for travelers should be individualized according to a risk assessment that considers both the itinerary and factors that are dependent on the prospective traveler. A structured approach to patient interaction ( Table 265-1 ) is the most efficient way to cover the necessary educational and preventive interventions. Providing clearly printed instructions in lay language is advised. The worldwide epidemiology of travel-related…

Approach to the Patient with a Sexually Transmitted Infection

Sexually Transmitted Infections Definition Sexually transmitted infections (STIs) include a wide variety of organisms that are transmitted through intimate contact involving skin or mucosal surfaces of the oropharynx, vagina, penis, and rectum. STIs can generally be divided into five broad categories (syndromes): urethritis, genital ulcers, epithelial cell disorders, vaginal discharge, and ectoparasites ( Table 264-1 ). Gender inclusive models ( Chapter 215 ) and programs of…

Approach to the Patient with Urinary Tract Infection

Definitions Urinary tract infection (UTI) is bacterial or fungal infection of urine with associated signs or symptoms. The clinical presentation varies from cystitis (bladder or lower tract infection) to pyelonephritis (renal or upper tract infection) and urosepsis (systemic inflammatory response syndrome or septic shock from a urinary source). Asymptomatic bacteriuria is best considered a state of colonization that requires treatment in only specific clinical circumstances. Urethritis…

Approach to the Patient with Suspected Enteric Infection

Definition Enteric infections are endemic in many low-income countries but may also be contracted from contaminated food or water in developed countries. Symptoms may range from minimal gastrointestinal distress to life-threatening watery diarrhea or dysentery. Epidemiology Worldwide, enteric infections are a leading cause of morbidity. In low- and middle-income countries without access to clean water and basic sanitation, young children are disproportionately affected with acute diarrheal…

Prevention and Control of Health Care–Associated Infections

The Burden of Health Care–Associated Infections Epidemiology The Centers for Disease Control and Prevention (CDC) defines health care–associated infections as infections that patients acquire during the course of receiving health care treatment for other conditions. Nosocomial infection is a term that refers specifically to a health care–associated infection that develops in association with hospital care. The development of infection during the course of health care is…

Approach to Fever and Suspected Infection in the Immunocompromised Host

Definition Healthy individuals possess robust antimicrobial defense systems that include physical barriers in the form of skin and mucosal membranes, innate immune defenses that are conserved through evolution, and adaptive (“acquired”) immune defense systems ( Chapter 35 ). These systems, which are highly interconnected, work in concert through an array of defensive surfaces, cells, and soluble factors to protect a host from potential microbial assailants. The…

Approach to Fever or Suspected Infection in the Normal Host

Overview of Fever Definition The traditional definition of a normal temperature as 98.6° F (37.0° C) came from a study more than 150 years ago, when 98.6° F (37.0° C) was the mean temperature from over 1 million axillary temperature measurements in 25,000 patients. Multiple more recent studies show contemporary axillary temperatures to be lower, with a mean axillary temperature of 96.75° F (36° C) and…

Principles of Anti-Infective Therapy

Selecting Antimicrobial Therapy Empirical Antimicrobial Therapy It is rare that antimicrobial therapy is instituted for a serious infection with full knowledge of the identity and antibiotic susceptibilities of the specific pathogen, so empirical antibiotic therapy typically must be initiated based on presumptions regarding the nature of the infection. The first challenge is to assess whether the patient likely has an infection and, if so, where is…

The Human Microbiome

The human microbiome has received considerable attention as a previously underappreciated factor in human health and disease. Alterations in the microbiome are associated with several clinical conditions, and restoration of a normal intestinal microbiome can be beneficial in selected situations. Definitions The so-called normal flora of microbes that live in and on the human body are part of the normal human microbiome. Although most attention has…

Introduction to Microbial Disease: Pathophysiology and Diagnostics

Infectious diseases have profoundly influenced the human genome and the course of human history. As of early 2023, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; Chapters 335 to 337 ) infection has caused nearly 7 million deaths worldwide. Beginning in the 1980s, acquired immunodeficiency syndrome (AIDS; Chapters 353 to 359 ) disrupted the social fabric of many countries, especially in Africa, and distressed health care systems…

Surgical Treatment of Joint Diseases

Epidemiology Estimates of the prevalence of arthritis and other rheumatic diseases demonstrate the enormous impact that these conditions have on the U.S. populace and the health care system in general. Over 21% of U.S. adults report physician-diagnosed arthritis. Osteoarthritis ( Chapter 241 ), which is the most prevalent form, affects upward to 31 million U.S. adults. Arthritis is already the leading cause of disability in the…

Systemic Diseases in Which Arthritis Is a Feature

Arthritis, arthralgias, and myalgias can be significant features of several systemic diseases and may be the presenting symptoms for some of these disorders ( Table 254-1 ). Appropriate evaluation of these musculoskeletal symptoms, including selected laboratory tests and radiographs, can provide clues to the early diagnosis of these diseases. Synovial biopsies are rarely necessary but can be diagnostic. Because of the rarity of many of these…

Fibromyalgia

Definition Fibromyalgia is the term that describes chronic widespread musculoskeletal pain, for which no alternative cause can be identified. If fatigue rather than pain is the presenting complaint, individuals are often diagnosed with chronic fatigue syndrome. , Gastroenterologists often see the exact same patients and focus on their gastroenterologic complaints, and often use the terms functional gastrointestinal disorder, irritable bowel syndrome, nonulcer dyspepsia, noncardiac chest pain,…

Crystal Deposition Diseases

The three most common crystal-induced arthropathies are caused by precipitation of monosodium urate monohydrate, calcium pyrophosphate dihydrate, and basic calcium phosphate and are termed gout, calcium pyrophosphate arthropathy , and basic calcium arthropathy , respectively. Basic calcium crystals are ultramicroscopic in size and are not detected by the compensated polarized microscopy used to identify monosodium urate and calcium pyrophosphate dehydrate crystals. Like monosodium urate and calcium…

Infections of Bursae, Joints, and Bones

Infection of Bursae Septic Bursitis Definition Bursae are the satellite structures that form to protect tissues from bony prominences. The superficial bursae, including the olecranon, prepatellar, infrapatellar, and bursae over the first metatarsophalangeal bunions, are more likely to become infected than are the deep bursae, such as the subacromial, trochanteric, and iliopsoas bursae. Epidemiology Olecranon bursitis may occur in as many as 10 in 100,000 persons…

Giant Cell Arteritis and Polymyalgia Rheumatica

Definition Polymyalgia rheumatica and giant cell arteritis, also called temporal arteritis, are companion systemic inflammatory disorders of unknown etiology that is propagated by antigen-driven, cell-mediated immune mechanisms that may be associated with specific genetic markers. These disorders represent a spectrum from severe proximal aches and pains and constitutional symptoms to an occlusive granulomatous vasculitis of medium and large vessels that can lead to permanent blindness or…