Chapter 25 1. Describe the normal habitat of the organisms discussed in this chapter and the means of transmission for human infection. 2. List the general characteristics of the bacteria discussed in this chapter. 3. Identify unusual biochemical reactions and incubation conditions required of organisms discussed in this chapter. 4. Outline the major tests used to identify the organisms in these groups. 5. Compare the appearance of the different genera in Gram stain preparations. 6. Describe the colonial appearance of the clinically significant species. The habitats of the species listed in Table 25-1 vary from soil and water environments to the upper respiratory tract of various mammals. Certain species have been exclusively found in humans, whereas the natural habitat for other organisms remains unknown. TABLE 25-1 Identifiable virulence factors are not known for most of the organisms listed in Table 25-2. However, because infections usually involve exposure of compromised patients to contaminated materials, most of these species are probably of low virulence. Among the environmental organisms listed, Achromobacter spp. are most frequently associated with various infections, including bacteremia, meningitis, pneumonia, and peritonitis. They also have been implicated in outbreaks of nosocomial infections. Achromobacter piechaudii has been isolated from pharyngeal swabs, wounds, blood, and ear discharge. Achromobacter xylosoxidans increasingly has been recovered from patients with cystic fibrosis. However, it is unclear whether the organism is implicated in causing clinical disease in patients with cystic fibrosis or whether it simply colonizes the respiratory tract. A. denitrificans has been recovered from urine, prostrate secretions, the buccal cavity, pleural fluid, and eye secretions. A. faecalis has been isolated from a wide range of clinical specimens and has been identified in bacteremia, ocular infections, pancreatic abscesses, bone infections, urine, and ear discharge. Comamonas spp. have been identified in cases of endocarditis, meningitis, and catheter-associated bacteremia. They have also been recovered from sputum in patients with cystic fibrosis. Other organisms, such as O. urethralis and O. ureolytica have been isolated predominantly from the human urinary tract. Pseudomonas alcaligenes and Pseudomonas pseudoalcaligenes rarely have been identified in clinical samples. TABLE 25-2 Pathogenesis and Spectrum of Disease No special considerations are required for collection and transport of the organisms discussed in this chapter. Refer to Table 5-1 for general information on specimen collection and transport. Table 25-3 describes the colonial appearance and other distinguishing characteristics (e.g., pigment and odor) of each genus on 5% sheep blood and MacConkey agars. TABLE 25-3 Colonial Appearance and Characteristics
Alcaligenes, Bordetella (Non-pertussis), Comamonas, and Similar Organisms
Epidemiology
Species
Habitat (Reservoir)
Mode of Transmission
Achromobacter xylosoxidans
Environment, including moist areas of hospital. Transient colonizer of human gastrointestinal or respiratory tract in patients with cystic fibrosis
Not often known. Usually involves exposure to contaminated fluids (e.g., intravenous fluids, hemodialysis fluids, irrigation fluids), soaps, and disinfectants
Achromobacter piechaudii
Environment
Unknown. Rarely found in humans
Alcaligenes faecalis
Environment; soil and water, including moist hospital environments. May transiently colonize the skin
Exposure to contaminated medical devices and solutions
Bordetella bronchiseptica
Normal respiratory flora of several mammals, including dogs, cats, and rabbits. Not part of human flora
Probably by exposure to contaminated respiratory droplets during close contact with animals
Comamonas spp.
Environment, soil and water; can be found in hospital environment. Not part of human flora
Nosocomial opportunistic pathogens because of their ability to survive in aqueous environments
CDC group IVc-2
Uncertain. Probably water sources, including those in the hospital setting. Not part of human flora
Usually involves contaminated dialysis systems or exposure of wounds to contaminated water
Delftia acidovorans
Environment, soil and water; can be found in hospital environment. Not part of human flora
Uncertain. Rarely found in humans. Probably involves exposure to contaminated solutions or devices
Ignatzchineria spp.
Unknown. Probably environmental. Not part of human flora
Unknown. Rarely found in humans
Oligella urethralis
Oligella ureolytica
Unknown. May colonize distal urethra
Manipulation (e.g., catheterization) of urinary tract
Psychrobacter spp.
Unknown
Unknown
Roseomonas spp.
Unknown
Unknown. Rarely found in humans
Pathogenesis and Spectrum of Disease
Species
Virulence Factors
Spectrum of Disease and Infections
Achromobacter dentrificans
Unknown. Survival in hospital the result of inherent resistance to disinfectants and antimicrobial agents
Infections usually involve compromised patients and include bacteremia, urinary tract infections, meningitis, wound infections, pneumonia, and peritonitis; occur in various body sites; can be involved in nosocomial outbreaks.
Achromobacter xylosoxidans
Unknown. Survival in hospital the result of inherent resistance to disinfectants and antimicrobial agents
Infections usually involve compromised patients and include meningitis, pneumonia, otitis media, urinary tract infections, surgical wound infections, and bacteremia.
Alcaligenes faecalis
Unknown
Infections usually involve compromised patients. Often a contaminant; clinical significance of isolates should be interpreted with caution. Has been isolated from blood, respiratory specimens, and urine.
Alcaligenes piechaudii
Unknown
Rare cause of human infection.
Bordetella bronchiseptica
Unknown for humans. Has several factors similar to B. parapertussis
Opportunistic infection in compromised patients with history of close animal contact. Infections are uncommon and include pneumonia, bacteremia, urinary tract infections, meningitis, and endocarditis.
CDC group IVc-2
Unknown
Rare cause of human infection. Infections in compromised patients include bacteremia and peritonitis.
Comamonas testosteroni
Comamonas spp.
Unknown
Isolated from respiratory tract, eye, and blood but rarely implicated as being clinically significant.
Cupriavidus spp.
Unknown
Recovered from cystic fibrosis patients. Additional infections include bacteremia, peritonitis and tenosynovitis.
Delftia acidovorans
Unknown
Isolated from respiratory tract, eye, and blood but rarely implicated as being clinically significant.
Ignatzchineria spp.
Unknown
Clinical significance uncertain, has been isolated from wounds, urine, and blood.
Oligella urethralis
Unknown
Urinary tract infections, particularly in females.
Oligella ureolytica
Unknown
Also isolated from kidney, joint, and peritoneal fluid.
P. alcaligenes
P. pseudoalcaligenes
Unknown; low virulence associated with administration of contaminated solutions and medicines
Recovered from the respiratory secretions of patients with cystic fibrosis.
Psychrobacter spp.
Unknown
Rare cause of human infection
Roseomonas spp.
Unknown; uncommon isolates from humans
Clinical significance uncertain. Typically opportunistic infections. Most isolated from blood, wounds, exudates, abscesses, or genitourinary tract of immunocompromised or debilitated patients.
Laboratory Diagnosis
Specimen Collection and Transport
Cultivation
Media of Choice
Colonial Appearance
Organism
Medium
Appearance
Achromobacter denitrificans
Achromobacter xylosoxidans
Achromobacter piechaudii
Alcaligenes faecalis
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