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Antifungal Agents

Fungal infections in children generally can be divided into superficial infections that affect persons with normal immune systems and invasive infections that occur primarily in children who are immunocompromised. Children can be immunocompromised due to genetic defects, pre-term birth, hematopoietic cell or solid organ transplantation, or following one of the chemotherapeutic regimens used for childhood malignancies. Improved treatments for malignancy and increasing success in the treatment…

Antibacterial Agents

Antibacterial agents, their mechanism of action, spectrum of antibacterial activity, patterns of antibiotic resistance, and current clinical use are presented in this chapter. Fig. 292.1 summarizes the main sites of antibacterial agent activity. Chapter 289 provides the principles regarding the selection of agents based on the characteristics of the patient and co-morbidities, site(s) of infection, likely pathogen(s) and antibiotic susceptibilities, antibiotic tissue exposure, and consideration of…

Pharmacokinetic and Pharmacodynamic Basis of Optimal Antimicrobial Therapy

Acknowledgment The authors acknowledgment contributions of Michael D. Reed to this chapter in previous editions. As clinicians continuously strive to practice evidence-based medicine, the use of antibiotics can be frustratingly empiric. Ethical concerns, multiple confounding variables, and unclear endpoints hamper clinical infectious disease research. This empiricism is clear in most recommendations for antibiotic dosing and duration of therapy, especially in children, because only a fraction of…

Mechanisms and Detection of Antimicrobial Resistance

Microorganisms have survived for millions of years because of their ability to adapt to hostile environments. Since the 1940s, bacteria that cause human infections have been exposed to ever-increasing antimicrobial pressure as a result of appropriate and inappropriate use of these agents. In the US, investigators have estimated that >7 million pounds of antimicrobial agents are consumed annually by humans. Approximately 80% of all antibiotics sold…

Principles of Anti-Infective Therapy

The selection of optimal antibiotic therapy for presumed bacterial infection is based on the assessment of the balance of benefits and risks of specific therapy for each child. Prescribing the right antibiotic(s) early in the course of a serious infection can save a life or avoid substantial morbidity. Antibiotic therapy given to a child without bacterial infection exposes the child needlessly to antibiotic toxicities and other…

Use of Common Clinical Laboratory Tests to Assess Infectious and Inflammatory Diseases

Acute Phase Response Stimuli of many kinds, including infection, trauma, hemorrhage, or ischemia, activate the innate immune system through binding of pathogen-associated molecular patterns (PAMPs) and/or danger-associated molecular patterns (DAMPs) to pattern-recognition receptors (PRRs) on the surface of neutrophils, monocytes, and a variety of other cells. These events lead to the release of multiple proinflammatory cytokines, including interleukin1β (IL-1β), IL-6, IL-8, and tumor necrosis factor (TNF).…

Laboratory Diagnosis of Infection Due to Viruses, Chlamydia, and Mycoplasma

Viruses The availability of rapid and reliable viral diagnostic tests, particularly nucleic acid amplification tests (NAATs), facilitates decision making in the prevention, treatment, public health, and infection control measures related to viral infections. With specific antiviral therapy available for many clinically relevant viruses, a specific viral diagnosis may limit the need for further diagnostic testing and unnecessary antibiotic therapy. Two major approaches to diagnosis of viral…

Laboratory Diagnosis of Infection Due to Bacteria, Fungi, Parasites, and Rickettsiae

Bacteria Collection and Processing of Clinical Specimens Proper collection and handling of clinical specimens is a crucial first step in the microbiologic diagnosis of an infectious disease. No degree of laboratory expertise can correct the errors of inappropriately collected and transported specimens. Common problems include submission of insufficient quantities of specimens; contamination of specimens with microbial flora present in and on the patient; use of inappropriate…

Blood Trematodes: Schistosomiasis

Schistosomiasis (i.e., bilharzia or snail fever) is a parasitic infection caused by trematodes that reside in the circulatory system. More than 230 million people worldwide suffer from schistosomiasis, which causes a range of disease from overt clinical manifestations to subtle hindrance of day-to-day activities. Infected children can have impaired growth and development. Infection occurs from exposure to freshwater into which snails, the intermediate host of the…

Clonorchis, Opisthorchis, Fasciola, and Paragonimus Species

Liver and lung trematodes are hermaphroditic, zoonotic flukes that use snails as intermediate hosts ( Table 284.1 ). Snails are infected by eggs in feces passed into the environment by humans and other mammals. The snails release cercariae that encyst in second intermediate hosts (i.e., fish, crustaceans, and amphibians) or on water plants. When encysted cercariae are ingested, humans and other definitive hosts become infected. TABLE…

Intestinal Trematodes

More than 70 species of zoonotic, hermaphroditic intestinal flukes can parasitize the human intestine. Most human infections are asymptomatic, but heavy infections are more likely to result in clinical disease. Adult flukes are flat and leaf-shaped, ranging in length from a few millimeters to several centimeters. They attach to the intestinal mucosa by means of oral and ventral suckers and release eggs having a characteristic operculum…

Taenia (Multiceps) multiceps and Taenia serialis : Coenurosis

Coenurosis is human infection with larval forms of the animal tapeworms Taenia (Multiceps) multiceps and Taenia serialis. The coenurus is a fluid-filled cyst that is a few millimeters to 2 cm or more in diameter. The wall is a thin, delicate membrane to which multiple invaginated scolices (i.e., protoscolices) are attached in rows or clusters. These zoonotic infections occur primarily in tropical and subtropical regions. Epidemiology…

Echinococcus Species: Agents of Echinococcosis

Echinococcus Granulosus Description of the Pathogen Echinococcus granulosus , which causes cystic echinococcosis, is a cestode whose life cycle involves dogs and other canids as definitive hosts for the intestinal tapeworm. Domestic and wild ungulates are intermediate hosts for the tissue-invading metacestode, which is the larval stage of the tapeworm ( Fig. 281.1 ). The metacestode (i.e., echinococcal cyst) is a fluid-filled, spherical, unilocular cyst that…

Taenia solium, Taenia asiatica, and Taenia saginata : Taeniasis and Cysticercosis

Clinical syndromes associated with infection with Taenia species tapeworms include intestinal disease caused by adult parasites (i.e., taeniasis) and single or multiorgan inflammatory conditions associated with larval stages within tissue (i.e., cysticercosis and coenurosis). Distinguishing morphologic features of adult tapeworms include an anterior scolex and a series of segments (i.e., proglottids) that develop at the base of the scolex and extend distally as the worm grows…

Diphyllobothriidae, Dipylidium and Hymenolepis Species

Diphyllobothriidae Description of the Pathogens Pseudophyllidean cestodes in the family Diphyllobothriidae can cause intestinal tapeworm infections in humans. Around 16 species have been reported to cause human infections, though only six species have been confirmed with modern molecular techniques. In addition to humans, natural definitive hosts for the adult tapeworms generally include wild and domestic fish-eating terrestrial carnivores (e.g., dogs, cats, bears), marine mammals including pinnipeds,…

Blood and Tissue Nematodes: Filarial Worms

Human filariasis encompasses parasitic infections caused by several species of tiny, thread-like nematode worms that affect the skin, lymphatic vessels, and connective and subcutaneous tissues. Although rarely a direct cause of death, some filarial worms, especially the three species causing lymphatic filariasis and the one causing onchocerciasis, cause substantial disability globally. Filarial worms are transmitted by various blood-feeding vectors, including several species of mosquitoes, blackflies, and…

Tissue Nematodes

Tissue nematodes are parasitic roundworms that invade human tissues. Many of these nematodes are present in outdoor environments and are transmitted to children through the ingestion of nonfood substances. Most of these tissue parasites are zoonoses, with the infectious stage occurring in another animal host. However, infections in a child may result in permanent changes in cognitive ability, development, or vision. This chapter focuses on some…

Intestinal Nematodes

Intestinal nematode infections are caused by a group of helminths, sometimes referred to as soil-transmitted nematodes, soil-transmitted helminths, or geohelminths. They are among the most common parasitic infections in humans and affect more than one-seventh of the world’s population. In most endemic populations, children are affected disproportionately by intestinal nematodes and often acquire infections of high intensity (i.e., large numbers of worms in the gastrointestinal tract)…

Trypanosoma Species (Trypanosomiasis)

Organisms of the genus Trypanosoma are flagellated protozoan parasites that inhabit the blood and tissue of a wide variety of vertebrate hosts, including birds, reptiles, and mammals. The name is derived from the Greek, trypano (meaning auger, a helical shaped tool) and soma (meaning body). The trypanosomes that infect humans in Africa (T. brucei) are transmitted by the bite of Glossina flies, whereas human trypanosomiasis in…

Trichomonas vaginalis

Trichomonas vaginalis can infect both men and women and is recognized as the most common nonviral sexually transmitted infection in the world. Description of The Pathogen T. vaginalis , a flagellated protozoan parasite, was first described in 1836 by French physician Alfred François Donné, who observed these “animalculi” in vaginal fluid under a light microscope. T. vaginalis eukaryotic parasites are typically oval or fusiform, 7–32 μm…