CORYNEBACTERIUM, ERYSIPELOTHRIX

• Gram-Positive Regular and Irregular Non-Spore-Forming Bacilli

  Non–Spore-Forming, Nonbranching, Catalase-Negative Bacilli
• Erysipelothrix rhusiopathiae


  Catalase negative bacilli, 3 species in the genus Erysipelothrix: Erysipelothrix rhusiopathiae (only species in the genus known to cause disease in humans), Erysipelothrix tonsillarum, Erysipelothrix inopinata
• Erysipelothrix rhusiopathiae


  • Found worldwide, commensal or a pathogen in a wide variety of vertebrates and invertebrates, including domestic swine, birds, and fishes
  • Thin, rod-shaped, gram-positive organism that can form long filaments arranged singly, in short chains, or in a "V" shape similar to that seen with Corynebacteria
  • Decolorizes easily, so it may appear gram variable
• Specimens received

  • Tissue biopsy or aspirates from skin lesions
• Inoculation and incubation

  Inoculated into a nutrient broth with 1% glucose and incubated in 5% CO2 at 35°C
• Erysipelothrix rhusiopathiae growth on culture media

  • Grows on standard culture media SBA and chocolate agar
  • Usually nonhemolytic and pinpoint after 24 hours of incubation
  • After 48 hours of incubation, two distinct colony types are seen: a smaller, smooth form is transparent, glistening, and convex with entire edges; larger, rough colonies are flatter with a matte surface, curled structure, and irregular edges
• Erysipelothrix rhusiopathiae characteristics

  • Nonmotile, pleomorphic, aerobic or facultatively anaerobic
  • Hydrogen sulfide positive (H2S +)
  • Voges-proskauer test negative (VP-)
  • Growth in a gelatin stab culture yields a highly characteristic "test tube brush–like" pattern at 22° C
• Human cases of Erysipelothrix rhusiopathiae

  • Typically result from occupational exposure, involves handling fish and animal products are most at risk
  • Usual route of infection is through cuts or scratches on skin
  • Resistant to salting, pickling, and smoking, and survives well in environmental sources, such as water, soil, and plant material
• Types of disease produced by Erysipelothrix rhusiopathiae in humans

  • Erysipeloid (a localized skin disease)
  • Septicemia (often associated with endocarditis)
  • Generalized, diffuse cutaneous infection
• The incidence of Erysipelothrix rhusiopathiae infections is low
• Non–Spore-Forming, Nonbranching, Catalase-Positive Bacilli

  • 20 genera, Corynebacterium, Mycobacterium, and Nocardia greatest clinical significance
  • All produce catalase, possess mycolic acids, and a unique type of peptidoglycan
• Corynebacterium

  • Gram-positive, nonmotile rods with irregularly stained segments, and sometimes granules
  • Frequently show club-shaped swellings and hence the name Corynebacteria (from coryne, meaning club)
  • First observed and described by Klebs (1883) but was first cultivated by Loeffler (1884)
  • Known as the Klebs–loeffler bacillus
  • Roux and Yersin (1888) discovered the diphtheria exotoxin and established its pathogenic effect
  • Antitoxin described by Von Behring (1890) who was awarded nobel prize for this work
• Diphtheria


  • Disease caused by C. diphtheriae, (Greek, diphtheria, "leathery skin," referring to the pseudomembrane that initially forms on the pharynx)
  • As the disease progresses, an adherent membrane (pseudomembrane) may begin to cover the tonsils, pharynx, and/or nasal tissues
• Corynebacterium genus

  • More than 100 species, at least 50 are thought to be clinically significant
  • Normal biota on the skins and mucous membranes of humans and animals, some found in the environment
  • Basis of 16S ribosomal ribonucleic acid (rRNA) sequencing, Corynebacteria are closely related to Mycobacteria and Nocardiae
• Lipophilic Corynebacteria

  • Divided into nonlipophilic and lipophilic species
  • Lipophilic corynebacteria often considered fastidious and grow slowly on standard culture media
  • Cultures often must be incubated for at least 48 hours before growth is detected
  • Growth is enhanced if lipids are included in the culture medium
• Corynebacterium diphtheriae toxin

  • Toxigenic strains produce a very powerful heat labile polypeptide exotoxin
  • Almost all strains of gravis, 95-99% of intermedius and 80-85% of mitis produce this toxin
  • Carried by strains with a lysogenic B-phage that carries the TOX gene
  • Released if the iron in the medium is consumed
• Iron for Corynebacterium diphtheriae toxin production

  • Toxin production is influenced by the concentration of iron in the medium
  • The optimum level of iron for toxin production is 0.1 mg per liter, while a concentration of 0.5 mg per liter inhibits the formation of toxin
  • The toxin is released in significant amounts only when the available iron in the culture medium is exhausted
  • Acts by inhibiting protein synthesis
• Other medically important Corynebacteria

  The non-diphtheria Corynebacteria are diverse usually isolated from the environment and commensals of the skin and mucous membranes
• Corynebacterium ulcerans

  • Resembles gravis type of C. Diphtheriae but it liquefies gelatin, ferments trehalose slowly

  Does not reduce nitrate to nitrite

  It is PYZ negative and urease positive

  Animal contact or ingestion of unpasteurized dairy products

  Diphtheria-like toxin
• Corynebacterium pseudotuberculosis (C. ovis)

  • Known also as Preisz Nocard bacillus

  Primarily an animal pathogen and rarely infects man

  Human infections mainly occur in patients with animal (sheep) contact

  Dermonecrotic toxin cause the death of various cell types

  Diphtheria toxin
• Corynebacterium minutissimum


  • It is believed to be the causative agent of erythrasma, a localized infection of the stratum corneum
• Corynebacterium ulcerans

  Resembles gravis type of C. Diphtheriae but it liquefies gelatin, ferments trehalose slowly, does not reduce nitrate to nitrite, is PYZ negative and urease positive. Animal contact or ingestion of unpasteurized dairy products. Diphtheria-like toxin
• Corynebacterium pseudotuberculosis (C. ovis)

  Known also as Preisz-Nocard bacillus. Primarily an animal pathogen and rarely infects man. Human infections mainly occur in patients with animal (sheep) contact. Dermonecrotic toxin cause the death of various cell types. Diphtheria toxin
• Corynebacterium minutissimum


  It is believed to be the causative agent of erythrasma, a localized infection of the stratum corneum
• Corynebacterium jeikeium


  Infections have been limited to patients who are immune compromised, have undergone invasive procedures, or have a history of intravenous drug abuse. It is the most common cause of diphtheroid prosthetic valve endocarditis in adults
• Corynebacterium xerosis


  Commonly found on skin and mucota neoussites. C. Xerosis is rare, and affected patients are invariably immunosuppressed
• Corynebacterium bovis


  Commensal of cow's udder, which may cause bovine mastitis. Many of them cause infections in immunocompromised patients
• Diphtheroids resemble C. diphtheriae, occur as normal commensals in the throat, skin and other areas, may be mistaken for diphtheria bacilli and are known as diphtheroids. Stain more uniformly than diphtheria bacilli, are arranged in V forms or palisades rather than Chinese letter and possess few or no metachromatic granules. Common diphtheroids are C. pseudodiphtheriticum and C. xerosis
• Gardnerella vaginalis


  Short, pleomorphic gram-positive rod or coccobacillus that often stains gram variable or gram negative. Has a gram-positive type of cell wall; however, the peptidoglycan layer is thinner than that found in other gram-positive bacteria, such as Corynebacterium and lactobacillus. First described in 1953, is the only species in the genus. Found as normal biota in the human urogenital tract
• Gardnerella vaginalis


  Known for its association with bacterial vaginosis (BV) in humans. Organism can be isolated from 40% of women without BV. BV is a polymicrobial disease in which G. Vaginalis and other bacteria, such as Prevotella spp., Peptostreptococcus spp., Porphyromonas spp., Mobiluncus spp., Atopobium vaginae, and Mycoplasma hominis, are involved. Characterized by a mal-odorous discharge and vaginal pH greater than 4.5. Can also play a role in UTIs in men and women. The drug of choice to treat BV is metronidazole, although clindamycin is also good
• Gardnerella vaginalis


  Gram staining of vaginal secretions is generally regarded as the reference method for diagnosing BV. Observation of "clue cells," large squamous epithelial cells with gram positive and gram-variable bacilli and coccobacilli clustered on the edges - often appears as a pleomorphic, gram-variable coccobacillus or short rod. Often stain gram negative and are 1.5 to 2.5 µm in length. Nugent scoring system for Gram-stained vaginal smears is a more accurate means of diagnosing BV than cultures. Clue cells can be visualized in wet mounts of vaginal fluid when BV is suspected
• Gardnerella vaginalis


  Amsel's clinical criteria can also be used to diagnosis BV if three of four criteria are found: Homogeneous, thin, white discharge that smoothly coats the vaginal walls, Clue cells, Ph of vaginal fluid greater than 4.5, and Fishy odor of vaginal discharge before or after addition of 10% potassium hydroxide, the whiff test
• Gardnerella vaginalis


  Affirm VP III (Becton Dickinson, Sparks, MD), a DNA hybridization probe test for G. vaginalis, and the OSOM BV Blue test (Sekisui Diagnostics, Framingham, MA), which detects vaginal fluid sialidase activity, have acceptable performance compared with Gram staining of vaginal material. Cultures for G. vaginalis are infrequently performed. Vaginal discharge collected from suspected BV cases is the most common specimen - can also be isolated from urine. Takes longer than 24 hours to develop visible colonies, and G. vaginalis grows best in 5% to 7% CO2 at a temperature of 35° to 37° C
• Gardnerella vaginalis


  Grows on SBA as pinpoint, nonhemolytic colonies, also grows on CAP. Medium of choice for G. Vaginalis is human Blood Bilayer Tween (HBT) agar. V (vaginalis) agar also contains human blood (rabbit and human, not sheep) and is used for recovery of this organism. β-hemolytic, small, gray, and opaque. MALDI-TOF will identify this organism well. Some Laboratories use 16S rRNA gene sequencing for definitive identification of G. Vaginalis
• Other genera of irregularly shaped, gram-positive bacilli are: Arcanobacterium, Brevibacterium, Oerskovia, Turicell. They have been found to colonize humans and cause disease
• Rothia


  Organism resembles coryneform bacilli, forming not only short, gram-positive bacilli but also branching filaments that resemble filaments of facultative actinomycetes. When placed in broth, the species produces coccoid cells, a characteristic differentiating it from actinomycetes. Nitrate positive, nonmotile, esculin hydrolysis positive, and urease negative. Approximately two thirds of the isolates are catalase positive
• Rothia


  Actually gram-positive cocci that can appear rodlike, belong to the family micrococcaceae. Six species, two of which are regarded as clinically significant. Rothia mucilaginosa has been linked to bacteremia, endocarditis, pneumonia, and other infections. Rothia dentocariosa, which is typically, but not always, rod shaped, is a member of the normal human oropharyngeal microbiota and may be found in saliva and supragingival plaque
• Listeria Monocytogenes

  Non-spore-forming aerobic gram-positive bacilli / Ranging from coccobacilli to long filaments / 1-4 flagella / specific character of the organism manifest with tumbling end or over end motility at 22°C – 28°C but not at 37°C. No capsules. Resistant to cold, heat, salt, pH extremes, and bile. Grows on Muller Hinton agar with sheep blood as enrichment - Small zone of Hemolysis can be observed around and the underneath of the colony. Specimens are enriched if the tissues are kept at 4°C and plated on the media (Cold enrichment)
• Listeria Monocytogenes

  Bacteria are facultative anaerobic microbes. Catalase +, motile. Produce acid and not gas in various sugar fermentation tests. CAMP-positive
• Listeria Monocytogenes


  Can be found in a variety of dairy products, vegetables, fish and meat products. Will grow slowly on foods stored in a refrigerator. Can also be spread by contact with an infected product or surface, such as hands or counter tops, during food preparation