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Other Neisseria Species

Neisseria gonorrhoeae and N. meningitidis are the 2 most pathogenic Neisseria species. Other Neisseria species are common commensal inhabitants of the upper respiratory tract and oral cavity of humans and other animals, but they have been implicated in clinical disease in occasional cases, particularly in immunocompromised patients. The focus of this chapter is on these other Neisseria species, with mention of species that previously have been…

Neisseria gonorrhoeae

Neisseria gonorrhoeae is a pathogen only of humans. Gonorrhea, one of the oldest known human illnesses, continues to result in significant morbidity; an estimated 87 million cases occur worldwide each year. In the US, gonorrhea is the second most frequently reported communicable disease after Chlamydia trachomatis. The reader is referred to organism- or syndrome-specific chapters for the overall approach to genital tract infections. The major public…

Neisseria meningitidis

Neisseria meningitidis (meningococcus) is an important cause of serious bacterial infections in children, most commonly manifesting as purulent meningitis or septicemia. Asymptomatic pharyngeal colonization is more common than invasive disease, and humans are the only reservoir. Gaspard Vieusseux provided the first clinical description of meningococcal disease during an outbreak in Geneva, Switzerland, as recently as 1805, which was followed by epidemics across Europe for the next…

Other Gram-Positive, Catalase-Negative Cocci: Leuconostoc and Pediococcus Species and Other Genera

Characteristics Of Pathogens Among the gram-positive catalase-negative cocci, streptococci and enterococci cause most human infections. The remaining organisms belong to 5 genera that can be identified according to the criteria proposed by Facklam and colleagues ( Table 124.1 ), and they form colonies that are α hemolytic or nonhemolytic on sheep blood agar and are easily confused with Streptococcus pneumoniae or viridans streptococci. These organisms appear…

Streptococcus pneumoniae

Acknowledgments We acknowledge the contributions of Carrie Byington, MD, Georges Peter, MD and Jerome O. Klein, MD, for their work on this chapter in the previous editions. All references are available online at Elsevier eBooks for Practicing Clinicians . In the introduction to his classic 1938 monograph The Biology of the Pneumococcus, Benjamin White wrote that the “pneumococcus is altogether an amazing cell. Tiny in size,…

Groups C and G Streptococci

The β-hemolytic streptococci can be subdivided on the basis of whether they form large colonies or minute colonies on solid agar. Most notable among those β-hemolytic streptococci that form large colonies are Streptococcus pyogenes (group A) and Streptococcus agalactiae (group B). Among the remaining Lancefield-reactive β-hemolytic streptococci, groups C and G organisms are most commonly associated with human disease. In this chapter, groups C and G…

Viridans Streptococci, Abiotrophia and Granulicatella Species, and Streptococcus bovis Group

The viridans streptococci are genetically diverse organisms that share the propensity to colonize humans and occasionally penetrate local barriers to cause life-threatening disease. Their importance as the predominant cause of endocarditis in children and adults has been known for decades. Improvements in identification and classification led to the recognition that these organisms are a significant cause of other infections as well, including septicemia and infection of…

Enterococcus Species

Historically enterococci, Streptococcus bovis, and S. equinus were grouped together as Lancefield group D streptococci. However, genomic analysis resulted in the reclassification of these organisms, and enterococci now are considered a separate genus ( Table 120.1 ). This chapter focuses on enterococci; the nonenterococcal group D streptococci are discussed in Chapter 121 . TABLE 120.1 Clinical Significance of Enterococci and Group D Streptococci Species Association With…

Streptococcus agalactiae (Group B Streptococcus )

The Pathogen and Pathogenicity Streptococcus agalactiae is the species designation for Lancefield group B Streptococcus (GBS). Colonies appear on sheep blood agar as 3- to 4-mm, grey-white colonies typically with a narrow zone of β-hemolysis; organisms are gram-positive cocci. The group B–specific cell wall carbohydrate antigen is common to all strains, and a surface capsular polysaccharide (CPS) allows classification into serotypes Ia, Ib, II, III, IV,…

Streptococcus pyogenes (Group A Streptococcus )

Acknowledgment The authors acknowledge use of substantial material from this chapter in the previous edition. Group A Streptococcus (GAS) is synonymous with Streptococcus pyogenes, the only species in this group of β-hemolytic streptococci. GAS is a leading pathogenic bacterium affecting children and adolescents, and it is associated with a wide spectrum of infections and diseases. Worldwide, >600 million cases of GAS pharyngitis (“strep throat”) and >700…

Coagulase-Negative Staphylococci and Micrococcaceae

Coagulase-Negative Staphylococci Staphylococcus epidermidis and other coagulase-negative staphylococci (CoNS), once considered nonpathogenic commensal organisms, now are recognized clearly as potential true pathogens, particularly in hospitalized patients and those with indwelling foreign bodies. Multiple surveys have shown that CoNS are the most frequent cause of nosocomial bloodstream infections (BSIs) around the globe. These organisms are implicated particularly in bacteremic disease in patients in the intensive care unit…

Staphylococcus aureus

Acknowledgements The authors acknowledge substantial use of Robert S. Duam’s work in this chapter in the previous edition. Staphylococcus aureus is the most virulent species of the genus Staphylococcus and the most common pathogen isolated among pediatric patients in North America. The pathogenicity of S. aureus reflects its ability to acquire and integrate accessory genetic elements that confer virulence and to evade host defenses by a…

Classification of Bacteria

The ability to differentiate among distinct groups of organisms and to communicate with a common language about organisms in the context of disease is essential for clinical microbiologists and for physicians caring for patients. The official taxonomic ranks for naming bacterial organisms are kingdom, division, class, order, family, genus, and species. A bacterial species is defined as a distinct group of organisms that share a constellation…

Management of HIV Infection

The treatment and prognosis of pediatric HIV infection have changed dramatically since the start of the epidemic in the 1980s. The Department of Health and Human Services (DHHS) Panel on Antiretroviral Therapy and Medical Management of HIV-Infected Children has developed guidelines for use of antiretroviral agents in pediatric HIV infection. These guidelines are updated regularly to ensure that recommendations are based on the most recent evidence.…

Infectious Complications of HIV Infection

Opportunistic infections (OIs) were key to the identification of the AIDS and have been a major cause of HIV-associated morbidity and mortality. An unusual clustering of cases of Pneumocystis jirovecii pneumonia ( Pneumocystis pneumonia, PCP) in the early 1980s led in part to the recognition of AIDS. Other AIDS-associated OIs, including disseminated mycobacterial disease, cryptococcal meningitis, cerebral toxoplasmosis, and cytomegalovirus (CMV) retinitis, were recognized soon thereafter.…

Diagnosis and Clinical Manifestations of HIV Infection

Acknowledgements The authors acknowledge the use of substantial material from this chapter in the previous edition. Most cases of HIV infection in infants and young children result from perinatal transmission, which can occur in utero, during labor and delivery, or postnatally during breastfeeding. HIV acquired by sexual contact and injectable drug use contributes to the growing number of cases in adolescents and young adults. The early…

Immunopathogenesis of HIV-1 Infection

In the absence of antiretroviral therapy, most HIV-1 infections in children are due to mother-to-child transmission during pregnancy, birth, or breastfeeding. In settings where maternal HIV testing and treatment are available most infections occur during adolescence (see Chapter 109 ) due to sexual activity and/or injected drug used. In this chapter, we will review the main features of HIV-1 immunopathogenesis with emphasis on the unique features…

Epidemiology and Prevention of HIV Infection in Infants, Children, and Adolescents

The epidemiology of infection with HIV type 1 (HIV) in infants, children, and adolescents has evolved dramatically since the first case of pediatric HIV infection was described in 1983. This evolution is due in part to improvements in the management of HIV infection, with resultant decreased mother-to-child transmission of HIV and increased survival of HIV-infected individuals. This chapter addresses the epidemiology and prevention of HIV infection…

Infectious Complications of Corticosteroid Therapy

Corticosteroids play a key role in the management of many neoplastic, autoimmune, allergic, and autoinflammatory disorders. Corticosteroids are used for their lympholytic and antiinflammatory effects during infection, for example, to prevent airway obstruction during croup or Epstein-Barr virus−associated tonsillitis, or to dampen immune reconstitution inflammatory syndrome (IRIS) when treating pulmonary or brain infection in patients with acquired immunodeficiency syndrome (AIDS). Corticosteroids also are given frequently after…