Chryseobacterium, Sphingobacterium, and Similar Organisms

1. Describe the general characteristics of the organisms discussed in this chapter.

2. Identify the normal habitat and the routes of transmission for the organisms.

3. List the appropriate media for cultivation of the organisms listed, particularly E. meningoseptica.

4. Describe the colonial appearance of E. meningoseptica.

5. Outline the tests used to differentiate the major genera in this group, including Elizabethkingia sp., Myoides spp., Sphingobacterium spp., and Bergeyella zoohelicum.

Genera and Species to Be Considered

Current Name	Previous Name
Rhizobium radiobacter
Bergeyella zoohelicum	Weeksella zoohelicum, CDC group IIj
CDC group IIb*	Flavobacterium spp. (IIb)
CDC group EO-3
CDC group EO-4
CDC group O-1, O-2, and O-3
Chryseobacterium spp.^†	Flavobacterium gleum and Flavobacterium indologenes
Elizabethkingia meningoseptica	Chryseobacterium meningosepticum, Flavobacterium meningosepticum, and CDC group IIa
Empedobacter brevis	Flavobacterium breve
Myroides odoratus	Flavobacterium spp.
Myroides odoratimimus	Flavobacterium spp.
Sphingobacterium multivorum	Flavobacterium multivorum and CDC group IIK-2
Sphingobacterium spiritivorum	Flavobacterium spiritivorum and CDC group IIK-3
Sphingobacterium thalpophilum
Weeksella virosa	CDC group IIf

^*Includes clinical strains of C. gleum and C. indologenes other than the type strains.

^†Includes type strain of C. gleum and C. indologenes (formerly Flavobacterium gleum and F. indologenes).

General Characteristics

The organisms discussed in this chapter are environmental inhabitants that are occasionally encountered in human specimens. Most of the organisms originated in the heterogenous group Flavobacterium. However, when subjected to molecular analysis, they did not prove to be closely related and therefore have been reclassified. They are considered together here because they share similar physiologic and morphologic characteristics. Most are yellow-pigmented, oxidase-positive, glucose oxidizers that grow on MacConkey agar. Sphingobacterium spp. have an unusually large amount of sphingophospholipid compounds in their cell membranes. Sphingobacterium mizutaii, which does not grow on MacConkey agar, is discussed in Chapter 27.

As environmental inhabitants, these organisms may be found in various niches (Table 24-1). Most notable in terms of clinical relevance is their ability to survive in hospital environments, especially in moist areas. Although they are not considered part of normal human flora, these species can colonize a patient’s respiratory tract during hospitalization. This results from exposure to contaminated water or medical devices. Transmission also may occur directly from contaminated pharmaceutical solutions and, in the case of E. meningoseptica, from person to person.

TABLE 24-1

Epidemiology

Species	Habitat (Reservoir)	Mode of Transmission
Elizabethkingia meningoseptica, Chryseobacterium spp., Empedobacter brevis, Sphingobacterium spp.	Soil, plants, water, food, and hospital water sources, including incubators, sinks, faucets, tap water, hemodialysis systems, saline solutions, and other pharmaceuticals Not part of human flora	Exposure of patients to contaminated medical devices or solutions, but source is not always known. May colonize upper respiratory tract. E. meningoseptica occasionally may be transmitted from birth canal to neonate.
Chryseobacterium indologenes		Catheter-related infections
Bergeyella zoohelicum	Normal oral flora of dogs and other animals	Dog and cat bites

Because of their ability to survive well in hospital environments, these organisms have the potential to contaminate laboratory culture media and blood culture systems. Whenever these species are encountered, their clinical significance and the potential for contamination should be seriously considered.

Pathogenesis and Spectrum of Disease

As environmental organisms, no specific virulence factors have been identified for these species. However, the ability to survive in chlorinated tap water may give these organisms an edge in their ability to thrive in hospital water systems.

The development of infection basically requires exposure of debilitated patients to a contaminated source, resulting in respiratory colonization (Table 24-2). Depending on the patient’s health, subsequent infections, such as bacteremia and pneumonia, may develop. These infections are most frequently caused by Elizabethkingia meningoseptica or Myroides odoratus. Infections of several other body sites, which may or may not be preceded by respiratory colonization, have been associated with the other species.

TABLE 24-2

Pathogenesis and Spectrum of Diseases

Species	Virulence Factors	Spectrum of Disease and Infections
Elizabethkingia meningoseptica, Chryseobacterium spp., Empedobacter brevis, Sphingobacterium spp.	Specific virulence factors are unknown. Able to survive chlorinated tap water. E. meningoseptica, the species most often associated with human infections, can be encapsulated or produce proteases and gelatinases that destroy host cells and tissues.	Bacteremia (often associated with implanted devices, such as catheters, or contaminated medical solutions). E. meningoseptica is particularly associated with meningitis in neonates and less commonly in adults. Other organisms are associated with pneumonia, mixed infections of wounds, ocular and urinary tract infections, and occasionally sinusitis, endocarditis, peritonitis, and fasciitis.
Chryseobacterium indologenes		Catheter-related bacteremia Bacteremia associated with malignancies and neutropenia
Bergeyella zoohelicum		Dog and cat bite wounds Rarely meningitis and bacteremia
Myroides odoratus, Myroides odoratimimus	Pathogenesis unknown	Rarely isolated from humans. Associated with urine, blood, wounds, and respiratory specimens.
Weeksella virosa	Pathogenesis unknown	Genitourinary isolation, most often in women.

Meningitis caused by E. meningoseptica is the most notable infection associated with the organisms listed in Table 24-2. This life-threatening infection, which may be accompanied by bacteremia, originally gained attention because it occurred in neonates. However, E. meningoseptica meningitis can also occur in compromised adults. The organism has been implicated in hospital-based outbreaks of both meningitis and pneumonia.

Gram staining is used to detect these organisms in clinical material. The Chryseobacterium spp., E. meningoseptica, and CDC group IIb are medium to long straight rods that often appear as “II-forms” (i.e., cells that appear thin in the center and thicker at the ends). Empedobacter brevis varies in being short to long rods. Sphingobacterium spp. are short straight rods, S. thalpophilum may exhibit II-forms. Rhizobium radiobacter yellow group are slender, medium to long, gram-negative rods. CDC groups EO-3 and EO-4 are coccobacilli, and CDC groups O-1, O-2, and O-3 are short, gram-negative, curved rods.

Cultivation

Media of Choice

All genera and CDC groups in this chapter grow well on routine laboratory media such as 5% sheep blood and chocolate agars. They also grow well in the broth of blood culture systems and in common nutrient broths such as thioglycollate and brain-heart infusion.

Incubation Conditions and Duration

These organisms will produce detectable growth on blood and chocolate agars when incubated at 35°C in either carbon dioxide or ambient air for a minimum of 24 hours. Growth on MacConkey agar is usually detectable within 24 hours of inoculation.

Colonial Appearance

Table 24-3 presents descriptions of the colonial appearance and other distinguishing characteristics of each genus on 5% sheep blood and MacConkey agars.

TABLE 24-3

Colonial Appearance and Characteristics

Organism	Medium	Appearance
Rhizobium radiobacter	BAP MAC Only gold members can continue reading. Log In or Register to continue Share this: Click to share on Twitter (Opens in new window) Click to share on Facebook (Opens in new window) Like this: Like Loading... Related Related posts: Acinetobacter, Stenotrophomonas, and Similar Organisms Liver and Lung Trematodes Infections of the Lower Respiratory System Gastrointestinal Tract Infections Stay updated, free articles. Join our Telegram channel Tags: Bailey Scotts Diagnostic Microbiology Aug 25, 2016 \| Posted by admin in MICROBIOLOGY \| Comments Off on Chryseobacterium, Sphingobacterium, and Similar Organisms Full access? Get Clinical Tree Get Clinical Tree app for offline access Get Clinical Tree app for offline access

Organism

Medium

Appearance

Rhizobium radiobacter

BAP

MAC

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