Listeria, Corynebacterium, and Similar Organisms

Published on 08/02/2015 by admin

Filed under Basic Science

Last modified 08/02/2015

Print this page

rate 1 star rate 2 star rate 3 star rate 4 star rate 5 star
Your rating: none, Average: 0 (0 votes)

This article have been viewed 6538 times

Listeria, Corynebacterium, and Similar Organisms

Epidemiology

Most of the organisms listed in Table 17-1 are part of the normal human flora and colonize various parts of the human body, are found in the environment, or are associated with various animals. The two most notable pathogens are Listeria monocytogenes and Corynebacterium diphtheriae. However, these two species differ markedly in epidemiology. L. monocytogenes is widely distributed in nature and occasionally colonizes the human gastrointestinal tract. Many foods are contaminated with L. monocytogenes, including milk, raw vegetables, cheese, and meats. C. diphtheriae is only carried by humans, but in rare cases it is isolated from healthy individuals. Primary transmission for C. diphtheriae is through respiratory secretions or exudates from skin lesions.

TABLE 17-1

Epidemiology

Organism Habitat (Reservoir) Mode of Transmission
Listeria monocytogenes Colonizer:
Animals, soil, and vegetable matter; widespread in these environments
Human gastrointestinal tract
Direct contact:
Ingestion of contaminated food, such as meat and dairy products
Endogenous strain:
Colonized mothers may pass organism to fetus. Portal of entry is probably from gastrointestinal tract to blood and in some instances from blood to meninges.
Corynebacterium diphtheriae Colonizer:
Human nasopharynx but only in carrier state; not considered part of normal flora
Isolation from healthy humans is not common.
Direct contact:
Person to person by exposure to contaminated respiratory droplets
Contact with exudate from cutaneous lesions
Exposure to contaminated objects
Corynebacterium jeikeium Colonizer:
Skin flora of hospitalized patients, most commonly in the inguinal, axillary, and rectal sites
Uncertain
Direct contact:
May be person to person
Endogenous strain:
Selection during antimicrobial therapy
Introduction during placement or improper care of intravenous catheters
Corynebacterium ulcerans Normal flora:
Humans and cattle
Uncertain
Zoonoses:
Close animal contact, especially during summer
Corynebacterium pseudotuberculosis Normal flora:
Animals such as sheep, goats, and horses
Uncertain
Zoonoses:
Close animal contact, but infections in humans are rare
Corynebacterium pseudodiphtheriticum Normal flora:
Human pharyngeal and occasionally skin flora
Uncertain
Endogenous strain:
Access to normally sterile site
Corynebacterium minutissimum Normal flora:
Human skin
Uncertain
Endogenous strain:
Access to normally sterile site
Corynebacterium urealyticum Normal flora:
Human skin
Uncertain
Endogenous strain:
Access to normally sterile site
Leifsonia aquatica (formerly Corynebacterium aquaticum) Environment:
Fresh water
Uncertain
Corynebacterium xerosis Normal flora:
Human conjunctiva
Skin
Nasopharynx
Uncertain
Endogenous strain:
Access to normally sterile site
Corynebacterium striatum Normal flora:
Skin
Uncertain
Endogenous strain:
Access to normally sterile site
Corynebacterium amycolatum Normal flora:
Human conjunctiva
Skin
Nasopharynx
Uncertain
Endogenous strain:
Access to normally sterile site
Corynebacterium auris Uncertain:
Probably part of normal human flora
Uncertain
Rarely implicated in human infections
Kurthia spp. Environment Uncertain
Rarely implicated in human infections
Brevibacterium spp. Normal flora:
Human
Various foods
Uncertain
Rarely implicated in human infections
Dermabacter hominis Normal flora:
Human skin
Uncertain
Rarely implicated in human infections
Turicella otitidis Uncertain:
Probably part of normal human flora
Uncertain
Rarely implicated in human infections
Arthrobacter spp., Microbacterium spp., Cellulomonas spp., and Exiguobacterium sp. Uncertain
Probably environmental
Uncertain
Rarely implicated in human infections

In contrast to these two organisms, C. jeikeium is commonly encountered in clinical specimens, mostly because it tends to proliferate as skin flora of hospitalized individuals. However, C. jeikeium is not considered to be highly virulent. The penetration of the patient’s skin by intravascular devices is usually required for this organism to cause infection.

Pathogenesis and Spectrum of Disease

L. monocytogenes, by virtue of its ability to survive within phagocytes, and C. diphtheriae, by production of an extremely potent cytotoxic exotoxin, are the most virulent species listed in Table 17-2. Not all strains of C. diphtheriae are toxin-producing strains. The toxin gene is present in strains that have acquired the gene by viral transduction. The result is the incorporation of the toxin gene into the organisms’ genome. C. diphtheriae occurs in four biotypes: gravis, intermedius, belfanti, and mitis; C. gravis causes the most severe form of disease. The biotypes can be differentiated based on colonial morphology, biochemical reactions, and hemolytic patterns on blood agar.

TABLE 17-2

Pathogenesis and Spectrum of Diseases

Organism Virulence Factors Spectrum of Diseases and Infections
Listeria monocytogenes Listeriolysin O:
A hemolytic and cytotoxic toxin that allows for survival within phagocytes
Internalin: Cell surface protein that induces phagocytosis
Act A:
Induces actin polymerization on the surface of host cells, producing cellular extensions and facilitating cell-to-cell spread.
Siderophores:
Organisms capable of scavenging iron from human transferrin and of enhanced growth of organism.*
Systemic:
Bacteremia, without any other known site of infection
CNS infections: Meningitis, encephalitis, bran abscess, spinal cord infections
Neonatal:
Early onset: Granulomatosis infantisepticum—in utero infection disseminated systemically that causes stillbirth
Late onset: Bacterial meningitis
Immunosuppressed patients
Corynebacterium diphtheriae Diphtheria toxin:
A potent exotoxin that destroys host cells by inhibiting protein synthesis.
Respiratory diphtheria is a pharyngitis characterized by the development of an exudative membrane that covers the tonsils, uvula, palate, and pharyngeal wall; if untreated, life-threatening cardiac toxicity, neurologic toxicity, and other complications occur.
Respiratory obstruction develops and release of toxin into the blood can damage various organs, including the heart.
  Nontoxigenic strains:
Uncertain
Cutaneous diphtheria is characterized by nonhealing ulcers and membrane formation.
Immunocompromised patients, drug addicts, and alcoholics.
Invasive endocarditis, mycotic aneurysms, osteomyelitis, and septic arthritis*
Corynebacterium jeikeium Unknown:
Multiple antibiotic resistance allows survival in hospital setting
Systemic:
Septicemia
Skin infections:
Wounds, rashes and nodules
Immunocompromised:
Malignancies, neutropenia, AIDS patients.
Associated with indwelling devices such as catheters, prosthetic valves, and CSF shunts*
Corynebacterium ulcerans Unknown Zoonoses:
Bovine mastitis
Has been associated with diphtheria-like sore throat, indistinguishable from C. diphtheriae
Skin infections
Pneumonia
Corynebacterium pseudotuberculosis Unknown Zoonoses:
Suppurative granulomatous lymphadenitis
Corynebacterium pseudodiphtheriticum Unknown
Some stains have been identified that are resistant to macrolides*
Systemic:
Septicemia
Endocarditis
Pneumonia and lung abscesses; primarily in immunocompromised
Corynebacterium minutissimum Unknown
Probably of low virulence
Superficial, pruritic skin infections known as erythrasma
Immunocompromised:
Septicemia
Endocarditis
Abscess formation
Corynebacterium urealyticum Unknown
Multiple antibiotic resistance allows survival in hospital setting.
Immunocompromised and elderly:
Urinary tract infections
Wound infections
Rarely: endocarditis, septicemia, osteomyelitis, and tissue infections
Leifsonia aquatica ( formerly Corynebacterium aquaticum) Unknown Immunocompromised:
Bacteremia
Septicemia
Corynebacterium xerosis Unknown Immunocompromised:
Endocarditis
Septicemia
Corynebacterium striatum Unknown Immunocompromised:
Bacteremia
Pneumonia and lung abscesses
Osteomyelitis
Meningitis
Corynebacterium amycolatum Unknown
Multiple antibiotic resistance patterns
Immunocompromised:
Endocarditis
Septicemia
Pneumonia
Neonatal sepsis
Corynebacterium auris Unknown
Multiple antibiotic resistance patterns
Uncertain disease association but has been linked to otitis media
Kurthia spp., Brevibacterium and Dermabacter sp. Unknown Immunocompromised:
Rarely causes infections in humans
Bacteremia in association with indwelling catheters or penetrating injuries
Turicella otitidis Unknown Uncertain disease association but has been linked to otitis media
Arthrobacter spp., Microbacterium spp., Aureobacterium spp., Cellulomonas spp., and Exiguobacterium sp. Unknown Uncertain disease association

AIDS, Acquired immunodeficiency syndrome; CSF, cerebrospinal fluid; CNS, central nervous system.

L. monocytogenes is ingested through contaminated food. Once the organism has been phagocytized by white blood cells, it produces listeriolysin O, the major virulence factor. Listeriolysin O in combination with phospholipases enables the organism to escape from the white blood cells and spread to the bloodstream, eventually reaching the central nervous system and the placenta.

Most of the remaining organisms in Table 17-2 are opportunistic, and infections are associated with immunocompromised patients. For this reason, whenever Corynebacterium spp. or the other genera of gram-positive rods are encountered, careful consideration must be given to their role as infectious agents or contaminants. Corynebacterium urealyticum is an up-and-coming cause of cystitis in hospitalized patients, in those who have undergone urologic manipulation, and in the elderly.

Laboratory Diagnosis

Specimen Collection and Transport

No special considerations are required for specimen collection and transport of the organisms discussed in this chapter. Refer to Table 5-1 for general information on specimen collection and transport.

Specimen Processing

No special considerations are required for processing of most of the organisms discussed in this chapter. (Refer to Table 5-1 for general information on specimen processing.) One exception is the isolation of L. monocytogenes from placental and other tissue. Because isolating Listeria organisms from these sources may be difficult, cold enrichment may be used to enhance the recovery of the organism. The specimen is inoculated into a nutrient broth and incubated at 4°C for several weeks to months. The broth is subcultured at frequent intervals to enhance recovery.

Direct Detection Methods

Gram stain of clinical specimens is the only procedure used for the direct detection of these organisms. Most of the genera in this chapter (except Listeria, Rothia, and Oerskovia spp.) are classified as coryneform bacteria; that is, they are gram-positive, short or slightly curved rods with rounded ends; some have rudimentary branching. Cells are arranged singly, in “palisades” of parallel cells, or in pairs of cells connected after cell division to form V or L shapes. Groups of these morphologies seen together resemble and are often referred to as Chinese letters (Figure 17-1). The Gram stain morphologies of clinically relevant species are described in Table 17-3. L. monocytogenes is a short, gram-positive rod that may occur singly or in short chains, resembling streptococci.

TABLE 17-3

Gram Stain Morphology, Colonial Appearance, and Other Distinguishing Characteristics

Organism Gram Stain Appearance on 5% Sheep Blood Agar
Arthrobacter spp. Typical coryneform gram-positive rods after 24 hr, with “jointed ends” giving L and V forms, and coccoid cells after 72 hr (i.e., rod-coccus cycle*) Large colony; resembles Brevibacterium spp.
Brevibacterium spp. Gram-positive rods; produce typical coryneform arrangements in young cultures (<24 hr) and coccoid-to-coccobacillary forms that decolorize easily in older cultures (i.e., rod-coccus cycle*) Medium to large; gray to white, convex, opaque, smooth, shiny; nonhemolytic; cheeselike odor
Cellulomonas spp. Irregular, short, thin, branching gram-positive rods Small to medium; two colony types, one starts out white and turns yellow within 3 days and the other starts out yellow
CDC coryneform group F-1 Typical coryneform gram-positive rods Small, gray to white
CDC coryneform group G Typical coryneform gram-positive rods Small, gray to white; nonhemolytic
Corynebacterium accolens Resembles C. jeikeium Resembles C. jeikeium
C. afermentans subsp. afermentans Typical coryneform gram-positive rods Medium; white; nonhemolytic; nonadherent
C. afermentans subsp. lipophilum Typical coryneform gram-positive rods Small; gray, glassy
C. amycolatum Pleomorphic gram-positive rods with single cells, V forms, or Chinese letters Small; white to gray, dry
C. argentoratense Typical coryneform gram-positive rods Medium; cream-colored; nonhemolytic
C. aurimucosum Typical coryneform gram-positive rods Slightly yellowish sticky colonies; some strains black-pigmented
C. auris Typical coryneform gram-positive rods Small to medium; dry, slightly adherent, become yellowish with time; nonhemolytic
C. coyleae Typical coryneform gram-positive rods Small, whitish and slightly glistening with entire edges; either creamy or sticky
C. diphtheriae group Irregularly staining, pleomorphic gram-positive rods Various biotypes of C. diphtheriae produce colonies ranging from small, gray, and translucent (biotype intermedius) to medium, white, and opaque (biotypes mitis, belfanti, and gravis); C. diphtheriae biotype mitis may be beta-hemolytic; C. ulcerans and C. pseudotuberculosis resemble C. diphtheriae
C. falsenii Typical coryneform gram-positive rods Small; whitish, circular with entire edges, convex, glistening, creamy; yellow pigment after 72 hr
C. freneyi Typical coryneform gram-positive rods Whitish; dry; rough
C. glucuronolyticum Typical coryneform gram-positive rods Small; white to yellow, convex; nonhemolytic
C. jeikeium Pleomorphic; occasionally, club-shaped gram-positive rods arranged in V forms or palisades Small; gray to white, entire, convex; nonhemolytic
C. imitans Typical coryneform gram-positive rods Small, white to gray, glistening, circular, convex; creamy; entire edges
C. macginleyi Typical coryneform gram-positive rods Tiny colonies after 48 hr; nonhemolytic
C. matruchotii Gram-positive rods with whip-handle shape and branching filaments Small; opaque, adherent
C. minutissimum Typical coryneform gram-positive rods with single cells, V forms, palisading and Chinese letters Small; convex, circular, shiny, and moist
C. mucifaciens Typical coryneform gram-positive rods Small, slightly yellow and mucoid; circular, convex, glistening
C. propinquum Typical coryneform gram-positive rods Small to medium with matted surface; nonhemolytic
C. pseudodiphtheriticum Typical coryneform gram-positive rods Small to medium; slightly dry
C. pseudotuberculosis Typical coryneform gram-positive rods Small, yellowish white, opaque, convex; matted surface
C. riegelii Typical coryneform gram-positive rods Small, whitish, glistening, convex with entire edges; either creamy or sticky
C. simulans Typical coryneform gram-positive rods Grayish white; glistening; creamy
C. singulare Typical coryneform gram-positive rods Circular; slightly convex with entire margins; creamy
C. striatum Regular medium to large gram-positive rods; can show banding Small to medium; white, moist and smooth (resembles colonies of coagulase-negative staphylococci)
C. sundsvallense Gram-positive rods, some with terminal bulges or knobs; some branching Buff to slight yellow, sticky, adherent to agar
C. thomssenii Typical coryneform gram-positive rods Tiny after 24 hr; whitish, circular, mucoid and sticky
C. ulcerans Typical coryneform gram-positive rods Small, dry, waxy, gray to white
C. urealyticum Gram-positive coccobacilli arranged in V forms and palisades Pinpoint (after 48 hr); white, smooth, convex; nonhemolytic
C. xerosis Regular medium to large gram-positive rods can show banding; Small to medium; dry, yellowish, granular
Dermabacter hominis Coccoid to short gram-positive rods Small; gray to white, convex; distinctive pungent odor
Exiguobacterium acetylicum Irregular, short, gram-positive rods arranged singly, in pairs, or short chains; (i.e., rod-coccus cycle*) Golden yellow
Kurthia spp. Regular gram-positive rods with parallel sides; coccoid cells in cultures >3 days old Large, creamy or tan-yellow; nonhemolytic
Leifsonia aquatica Irregular, slender, short gram-positive rods Yellow
Listeria monocytogenes Regular, short, gram-positive rods or coccobacilli occurring in pairs (resembles streptococci) Small; white, smooth, translucent, moist; beta-hemolytic
Microbacterium spp. Irregular, short, thin, gram-positive rods Small to medium; yellow
Oerskovia spp. Extensive branching; hyphae break up into coccoid to rod-shaped elements Yellow-pigmented; convex; creamy colony grows into the agar; dense centers
Rothia spp. Extremely pleomorphic; predominately coccoid and bacillary (broth, Figure 17-2, A) to branched filaments (solid media, Figure 17-2, B) Small, smooth to rough colonies; dry; whitish; raised
Turicella otitidis Irregular, long, gram-positive rods Small to medium; white to cream, circular, convex

*Rod-coccus cycle means rods are apparent in young cultures; cocci are apparent in cultures greater than 3 days old.

Includes strains G-1 and G-2.

Includes C. diphtheriae, C. ulcerans, and C. pseudotuberculosis.

Cultivation

Media of Choice

Corynebacterium spp. usually grow on 5% sheep blood and chocolate agars. Some coryneform bacteria do not grow on chocolate agar, and the lipophilic (lipid loving) species (e.g., C. jeikeium, C. urealyticum, C. afermentans subsp. lipophilum, C. accolens, and C. macginleyi) produce much larger colonies when cultured on 5% sheep blood agar supplemented with 1% Tween 80 (Figure 17-3).

Selective and differential media for C. diphtheriae should be used if diphtheria is suspected. The two media commonly used for this purpose are cystine-tellurite blood agar and modified Tinsdale agar (TIN). Tellurite blood agar maybe used with or without cystine. Cystine enhances the growth of fastidious organisms, including C. diphtheriae. Both media contain a high concentration of potassium tellurite that is inhibitory to normal flora. Organisms capable of growing on Tinsdale agar are differentiated based on the conversion of the tellurite to tellurium. This conversion results in color variations of grey to black colonies on the two media. C. diphtheriae also produces a halo on both media. C. diphtheriae can be presumptively identified by observing brown-black colonies with a gray-brown halo on Tinsdale agar (Figure 17-4

Buy Membership for Basic Science Category to continue reading. Learn more here