Corynebacterium and Other Gram Positive Rods Flashcards
(23 cards)
Genus Corynebacteria characteristics
- found in nature (soil, water plants) and mucosa and skin flora of humans and animals
- catalase positive
- pleomorphism results in palisades, picket fences, or Chinese letters
- non acid fast
- non branching gram positive rods
- non spore forming
Cornyeform (diphtheroids) bacteria
An opportunistic pathogen that affects immunocompromised patients (Rhodoccus equi)
Metachromatic granules (characteristic of Corynebacterium)
Contain polymerized inorganic phosphate, an energy rich compound that acts as a reserve store of energy and phosphate
MALDI-TOF MS
Reliably identifies toxigenic strains of Cornyebacterium. But it is still limited right now
Media for Corynebacterium Diphtheria
Cystine tellurite:
- Cystine: selective, enhances growth of fastidious organisms
- potassium tellurite:
-selective:
Inhibits gram positive and gram neg bacteria
- differential:
Reduction of potassium tellurite, colonies are gray-black
-Modified tinsdale agar: organisms are differentiated based on the conversion of the tellurite to tellurium
- results in black colonies
- Loeffler medium: contains serum and egg and stimulates growth of organism and production of metachromatic granules in the cells.
- gray, white translucent colonies
-Pai agar
4 diphtheriae bio types differentiated by colony morphology
- Intermedius
- Mitis
- Gravis
- Belfanti
Vaccines for Diptheriae
Dtap and Tdap are the vaccines
ID of Diptheria toxin
Elek test: immunodiffusion test, definitive ID by detection of diptheriae toxin
Corynebacterium diptheriae significance
-releases an exotoxin that causes damage to heart and neural cells and can be lethal
- causes respiratory and cutaneous diphtheria
- causes pharyngitis and forms a pseudo membrane made up of cellular debris
Toxin production for Diptheriae
Exotoxin released into bloodstream and has 2 subunits
- A subunit: blocks protein synthesis by inactivating elongation factor
- B subunit: binds to heart and neural tissue
This is for Respiratory Diptheriae
Presumptive Diagnosis of Diptheriae
- Determined by cystine-tellurite blood agar and modified tinsdale agar
- growth on sheep blood agar (observation of hemolytic reactions)
- loeffler and pai media: serum and egg and stimulate production of monochromatic granules
- Loeffler methylene blue stain: detects monochromatic granules
Definitive idenitification for Diptheriae
- Gueinea pig lethality test- lethal effect is neutralized by Diptheria antitoxi
- immunodiffusion test: Elek plate, Diptheria antitoxin filter paper strip
- tissue culture cell test: cytopathic effect is neutralized by Diptheria antitoxin
- EIA
- PCR
Corynebacterium jeikeium (JK)
- opportunistic infections of blood, wounds, dialysis exit site, bone marrow transplant
- causes meningitis, bacteremia, endocarditis, septicemia, pneumonia
- opportunistic pathogen (immunocompromised)
- normal skin flora
- rule out if found in blood culture or in pure culture from normally sterile site
- gram + coccobacilli that resemble strep
- urease -, no nitrate reduction, ferments glucose
- non-hemolytic, enhanced growth on Tween 80
- identified by MALDI Tof
- susceptible to vancomycin
-multi drug resistant
C. Urealyticum
- normal skin flora
- causes UTIs, kidney stones, alkaline encrusted cystitis and pyelitis
C. Ulcerans
-normal skin flora
- causes diphtheria like infections, zoonotic and cutaneous infections
C. pseudo-tuberculosis
- normal flora of sheep, goat, and horse
- lymphadenitis
Listeria Monocytogenes characteristics
- found in soil and water
- food borne outbreaks (fully cooked chicken linked to Tyson), so ingestion
- transmitted transplacentally or through infected north canal
- causes still birth, neonatal death, meningitis, bacteremia, encephalitis, endocarditis, conjunctivitis, skin infections, and lymphadenitis
-end over end motility, when incubated in nutrient broth at RT for 1hour at 25 deg C - Umbrella shaped pattern when incubated overnight in semisolid agar
At RT - grows well at 4 deg Celsius
- gram positive coccobaccili in pairs and short chains
- catalase positive (use catalase test to tell the difference between this and group B strep
-prevention: wash vegetables, thoroughly cook meat, pregnant women should avoid soft cheeses - listeriolysin O is the major virulence factor
- small, white, translucent, narrow zone of beta hemolysis, resembling strep
Lactobacillus Characteristics
- identified at the bench with alpha hemolytic, grey colonies on blood agar
- catalase negative
- non acid fast
- does not hydrolyze esculin
- H2S negative
- gram stain: chaining coccobaccilli, spirals, palisading, picket fence, Cheerios, Chinese letters
- non motile
- maintains proper pH in in vagina
- treat with penicillin
- dental infection, bacteremia, and endocarditis
Erysipelothrix Rhusiopathiae characteristics
-found in pigs, birds, fish, sheep, rabbits
-Infectious state: by direct contact or ingestion of contaminated water or meat (
-Cause skin lesions, bacteremia, and cellulitis
-On 5% sheep blood agar: they can be
-1. Large and rough colonies; slender filamentous, gram positive rods, can appear gram negative
-2. Small, smooth, and translucent colonies: small, slender rods or coccobacilli
-Produces H2S in TSI agar (black in TSI)
-Catalase negative and non motile
Arcanobacterium
-differentiate from strep by doing the streptex test. It tests negative
-Non branching gram positive rods that are delicate and curved with pointed ends
-Exhibit beta hemolysis
-Pharyngitis in 10-30 year olds, abscess infections
-Catalase negative and non acid fast
Rhodococcus
-aerobic actinomycete
-Non-hemolytic
-Growth on 5% sheep blood agar
-Shorter, branching gram positive rods (coccobacillary). Fragment into rods and cocci
-Identified at the bench, then sent to labcorp
-Mucoid salmon pink colonies
-Partially acid fast
-Found in fresh water, salt water, soil and farm animals
-Transmitted via respiratory inhalation (from feces) causes UTIs, bacteremia, wound infection, opportunistic pathogens
Nocardia
-Partially acid fast
-Aerobic actinomycete
-Found in soil and water, saphroyte, lab contaminant, skin flora and upper respiratory tract
-Transmits through traumatic inoculation or inhalation, primary pulmonary infections that disseminate to brain
-Gram positive, beaded, branching, delicate filamentous with fragmentation
-Beta hemolytic on sheep blood agar, wrinkled, dry, adherent, crumbly, chalky white to orange-tan, smells like dirt
-BYCE, Martin Lewis, modified Thayer Martin, and solid medium with paraffin as carbon source
-Grow very SLOWLY
-Mycetoma (chronic), Lymphocutaneous, skin abscesses or cellulitis
-Identified by MALDI-Tof, susceptibility tests sent to labcorp
Gardnerella Vaginalis
-thin peptidoglycan layer like gram negative
-Gram positive but stains as gram variable coccobaccilli (small pleomorphic)
-Detected by Affirm Vaginalis panel
-Clue cells: SQE with numerous attached small rods, seen in wet prep from vaginal swab
-Normal flora in female genital tract and get into the male urethra
-Media of choice: blood agar (non hemolytic), HBT Agar, CNS agar with added amphotericin
-SPS: free media or supplemented with gelatin
-Catalase negative, non acid fast
-Wet prep used for specimen
