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Other Gram-Negative and Gram-Variable Bacilli

A large number of gram-negative aerobic bacilli have been reported to cause human infection. In this chapter, selected gram-negative and gram-variable organisms are discussed that have not been described in other chapters and are important in certain clinical or epidemiologic circumstances, are newly described, or present special problems of diagnosis or therapy. For some of the bacteria considered here, taxonomy is in a state of flux…

Klebsiella granulomatis (Donovanosis, Granuloma Inguinale)

Donovanosis is a chronic, progressive ulcerative disease of the skin and subcutaneous tissues that is caused by the encapsulated, gram-negative bacterium Klebsiella (formerly Calymmatobacterium ) granulomatis. The infection is also commonly referred to as granuloma inguinale, but because this term can easily be confused with lymphogranuloma venereum (caused by the invasive L-serovars of Chlamydia trachomatis ), many experts now recommend donovanosis as the preferred term. McLeod…

Bartonella, Including Cat-Scratch Disease

Revised March 27, 2021 Background and Classification of Bartonella Species The genus Bartonella is a member of the class Alphaproteobacteria and family Bartonellaceae, and it is closely related to the genera Brucella and Agrobacterium ; members of the family Rickettsiaceae are more distantly related. On the basis of genetic similarity, unification of the genera Bartonella and Rochalimaea as a single genus and the removal of the…

Capnocytophaga

The genus Capnocytophaga consists of nine or more gram-negative fastidious species that typically reside as normal flora in the oral cavities of humans and other vertebrates including dogs and cats. Members of this genus can cause serious life-threatening infections in humans including septicemia and meningitis as a direct consequence of inapparent injuries or penetrating trauma resulting from animal contact or bites, most often involving dogs. Persons…

Legionnaires’ Disease and Pontiac Fever

Reviewed for currency January 14, 2021 History Legionnaires’ disease (LD) is an acute pneumonic illness caused by gram-negative bacilli of the genus Legionella , the most common of which is Legionella pneumophila (Lp). Pontiac fever (PF) is a febrile, nonpneumonic, systemic illness closely associated with, if not caused by, Legionella spp. Legionellosis is the term that encompasses all diseases caused by, or presumed to be caused…

Rat-Bite Fever: Streptobacillus moniliformis and Spirillum minus

Rat-bite fever is a rare systemic febrile illness typically transmitted by the bite of a rat or other small rodent. The infection has a worldwide distribution and can be caused by either Streptobacillus moniliformis or Spirillum minus, bacteria commonly found in the oropharyngeal flora of rodents. Streptobacillary disease accounts for the vast majority of cases of rat-bite fever in the United States, whereas S. minus infections…

Yersinia enterocolitica and Yersinia pseudotuberculosis

First discovered in 1894 in Hong Kong by Alexandre Yersin and Shibasaburo Kitasato, the genus Yersinia currently includes 18 species. Of these, only three have been identified as human pathogens: Y. pestis, Y. pseudotuberculosis, and Y. enterocolitica. While Y. pestis causes plague and is responsible for one of the greatest calamities in human history, the Black Death of mid-14th century Europe, infections from Y. pseudotuberculosis and…

Plague (Yersinia pestis)

The genus Yersinia includes at least 19 described species, of which 3 are important human pathogens. Yersinia enterocolitica and Yersinia pseudotuberculosis are enteric pathogens usually acquired through ingestion of contaminated food or water. The third species, Yersinia pestis, causes plague. Although closely related to Y. pseudotuberculosis, Y. pestis has undergone a marked evolutionary shift to become a vector-borne pathogen capable of achieving the high levels of…

Pasteurella Species

Pasteurella are gram-negative coccobacilli that inhabit the oral cavity and gastrointestinal tract of many animals and cause various infectious problems, including septicemia and pneumonia. In humans infection is most often caused by dog and cat bites, resulting in cellulitis, subcutaneous abscesses, and a number of other syndromes. Bacteria belonging to the genus Pasteurella were first isolated from birds with cholera in 1878; they were characterized 2…

Francisella tularensis (Tularemia)

Francisella tularensis is a gram-negative pathogen primarily of animals and occasionally of humans. The disease is now recognized as tularemia in most areas of the world, but it has been called rabbit fever, deer fly fever, Francis disease, and market men's disease in the United States; wild hare disease (yato-byo) and Ohara disease in Japan; and water-rat trappers’ disease in Russia. Tularemia continues to be responsible…

Brucellosis ( Brucella Species)

Brucellosis is the most frequently encountered worldwide zoonotic disease, which can be acquired from sheep, goat, cattle, swine, and other animals and transmitted to humans. Each year half a million new human brucellosis cases cause serious consequences on health and socioeconomic issues, particularly in underdeveloped countries. The disease is under control in developed countries. The disease is frequently transmitted from unsterilized milk and dairy products, and…

Haemophilus Species, Including H. influenzae and H. ducreyi (Chancroid)

Haemophilus influenzae Description of the Pathogen H. influenzae is a small, nonmotile, non–spore-forming bacterium and a pathogen of humans found principally in the upper respiratory tract, first reported by Pfeiffer in 1892. The sensational claim that it was the primary agent of epidemic influenza proved fallacious; nonetheless, it has a wide range of pathogenic potential. Its requirement for growth factors, which can be supplied by erythrocytes,…

Bacillary Dysentery: Shigella and Enteroinvasive Escherichia coli

Revised August 2, 2021 Reviewed for currency January 14, 2021 The term dysentery was used by Hippocrates to indicate a condition characterized by the frequent passage of stool containing blood and mucus, accompanied by straining and painful defecation. It was not until the end of the 19th century, when the causes of amebiasis and bacillary dysentery were determined, that the two great forms of dysentery could…

Salmonella Species

Salmonellae are named for the pathologist Salmon, who was involved in the first isolation (by Theobald Smith) of Salmonella choleraesuis from the porcine intestine. Salmonella are effective commensals and pathogens that cause a spectrum of diseases in humans and animals, including domesticated and wild mammals, reptiles, birds, and insects. Some Salmonella serotypes, such as Salmonella enterica Typhi, Salmonella Paratyphi, and Salmonella Sendai, are highly adapted to…

Acinetobacter Species

Acinetobacter, an aerobic, catalase-positive, oxidase-negative, gram-negative coccobacillus, was first described in 1911, but the initial description of the taxonomy of this diverse species was not published until 1986. Ubiquitous in nature, the 54 species of the genus Acinetobacter are associated with a specific ecologic niche that shapes their genomic contents. ( Table 222.1 ) Acinetobacter baumannii is the most virulent species and causes the bulk of…

Burkholderia pseudomallei and Burkholderia mallei : Melioidosis and Glanders

Revised August 10, 2021 The genus Burkholderia is currently composed of many species, but only three are notable pathogens for humans or animals: the former B. cepacia complex (described in Chapter 220 ), B. pseudomallei (the agent of melioidosis), and B. mallei (the agent of equine glanders). All three are aerobic, nonsporulating, straight or slightly curved gram-negative bacilli that were formerly placed in the genus Pseudomonas.…

Stenotrophomonas maltophilia and Burkholderia cepacia Complex

Revised April 26, 2022 Stenotrophomonas maltophilia and the Burkholderia cepacia complex (BCC) cause infections in a variety of vulnerable patient populations including hospitalized patients such as patients with cancer and patients with specific genetic diseases such as cystic fibrosis (CF) and chronic granulomatous disease (CGD). The high level of inherent and acquired resistance to antibiotics makes treating these infections particularly challenging. Microbiology Both S. maltophilia and…

Pseudomonas aeruginosa and Other Pseudomonas Species

Revised November, 2019 Pseudomonas species are ubiquitous gram-negative bacteria capable of inhabiting a wide variety of diverse environments, including soil, water, plants, insects, and animals. Among all Pseudomonas species, P. aeruginosa is the most important species affecting humans and is responsible for serious debilitating and life-threatening infections. P. aeruginosa infections were noted in the literature in the 1800s when physicians began to report a “condition” causing…

Enterobacteriaceae

Reviewed for currency November 8, 2020 The family Enterobacteriaceae belongs to the domain Bacteria, phylum Proteobacteria, class Gammaproteobacteria, and order Enterobacteriales ( ). The Enterobacteriaceae are gram-negative, non–spore-forming, facultative anaerobes that are typically motile by means of peritrichous flagella, ferment glucose, reduce nitrate to nitrite, and produce catalase but not oxidase. The family includes multiple genera implicated in human infection ( Table 218.1 ). TABLE…