Bacteriology Exam 4 (GPR) Flashcards
Actinomycetes: definition and gram stain
Actinomycetes is an order of bacteria that is: NONMOTILE, BRANCHING, and FILAMENTOUS. It is a GPR.
Main genera of interest in Actinomycetes
Nocardia spp
Nocardia catalase
Catalase +
Nocardia (gram, catalase, oxygen requirements)
gram positive rods, catalase positive, strictly aerobic
Epidemiology of Nocardia spp.
Soil and water organisms (NOT normal flora)
Where does Nocardia abscessus cause disease? Nocardia brasiliensis?
N. abscessus can cause disease in any body source, N. brasiliensis causes diseases in skin/tissue only.
Who are at the greatest risk for Nocardia infections?
Immunosuppressed patients
What does could an acinomycete gram stain look like that causes speculation of Nocardia infection?
Gram-positive branching or partially branching beaded filaments
What kind of stain can help us to identify Nocardia spp and differentiate them from mycobacteria?
Acid fast stain to observe presence of yellow to orange granules
What are special selective media to grow Nocardia in vitro? Why do we use them?
We can use BCYE with antibiotics to grow Nocardia. Nocardia are non-fastidious and can grow on routine media, but they are VERY slow growing which is why we can use the selective media to speed up the growth process.
What is the most isolated human pathogen in Nocardia sp?
N. asteroides
Nocardia (+ or -): Acid fast, Lysozyme resistance, Urea hydrolysis, Nitrate reduction, growth anaerobically
+ acid fast, + lysozyme resistance, + urea hydrolysis, +/- nitrate reduction, - growth anaerobically
Lysozyme broth growth with Nocardia
Nocardia is resistant to Lysozyme so it will grow in Lysozyme broth and it will be more turbid looking.
E. rhusiopathiae epidemiology
Zoonotic bacteria associated with animal workers (fish handlers, farmers, slaughterhouse workers, food prep workers, vets)
Types of infections caused by E. rhusiopathiae (3 types)
- skin lesions (erysipeloid)
- diffuse cutaneous infection with systemic symptoms
- bacteremia and endocarditis (severe!)
E. rhusiopathiae: Erysipeloid infection
localized skin infection resulting in sharply defined, purplish-red zone lesions on hands/fingers
Arcanobacterium epidemiology
Normal inhabitant of the mucosal membranes of sheep/dogs/cats/pigs (ZOONOTIC). Can cause infections in immunocompromised patients.
Gardnerella vaginalis epidemiology
Endogenous flora of the vagina that are opportunistic pathogens and kept in check by Lactobacillus sp.
Lactobacillus sp. epidemiology
Normal flora of human vagina to keep proper acidic pH, beneficial to the human host but may cause serious infections in immunocompromised patients
Primary purpose of Lactobacillus in vaginal areas
Metabolizes glucose to lactic acid to produce acidic vaginal pH environment to inhibit growth of pathogenic bacteria
Gram stain appearance of Arcanobacterium
delicate, curved, gram-positive rods with pointed ends
Lactobacillus gram stain appearance
pleomorphic GPR occurring in LONG chains and in coccobacilli and spiral forms
Ways to diagnose BV (bacterial vaginosis)
- Wet mount prepared in saline reveals “clue cells” which are squamous epithelial cells with numerous attached small rods
- Clue cells are present with lactobacilli being absent or very few in number
- Perform Nugent Scoring of BV grams
What will Gardnerella spp. not grow in? Why?
Blood culture broths - Gardnerella spp. are inhibited by SPS
What is a distinguishable characteristic of E. rhusiopathiae?
One of the few GPR that has the ability to produce H2S.
How to ID Arcanobacterium vs. Trueperella spp.
A. haemolyticum is beta hemolytic. Truperella sp. is non-hemolytic. (except Trueperella pyogenes)
A. haemolyticum is negative for liquefaction of gelatin, T. pyogenes is positive
Trueperella pyogenes
Formerly Arcanobacterium; animal pathogen; rare cause of infections
Which organism will create a REVERSE CAMP positive reaction on BAP?
A. haemolyticum
Colony morphology for E. rhusiopathiae
Two colonies exist: large and rough, or smooth and small
*Both may start as gamma hemolytic but become alpha hemolytic after prolonged incubation
E. rhusiopathiae: catalase, motility, gram stain, H2S, VP, urease, and esculin hydrolyze
Catase -
Nonmotile
pleomorphic GPR
H2S +
VP -
Urease -
Esculin hydrolyze -
E. rhusiopathie gram stain appearance
GPR that can form long filaments and arranged in V shape (can appear gram variable)
Colony morphology/hemolysis of Lactobacillus sp.
Multiple colony morphologies:
1. pinpoint alpha hemolytic
2. rough, gray colonies with alpha/gamma hemolysis
What 3 pathogenic bacteria does Lactobacillus suppress?
Gardnerella vaginalis, Mobiluncus spp., and Prevotella spp.
Lactobacillus infections
Only found in immunocompromised patients, can cause possible endocarditis (rare)
G. vaginalis hemolysis patterns on BAP vs. HBT agar
On BAP, G. vaginalis is nonhemolytic
On HBT agar, G. vaginalis is beta hemolytic
Nugent Scoring of BV grams: what does a normal score indicate?
High numbers of Lactobacillus (no BV)
Nugent Scoring Criteria
Score of 7 or more indicates BV (no lactobacillus, high pathogens)
Score of 4-6 is intermediate
Score of 0-3 is normal (normal or high amounts of lactobacillus)
Affirm VP
Tests vaginal specimens for Gardnerella, Trichomonas, and Candida (blue indicates positive presence)
Many lactobacillus spp. are highly resistant to ________.
Vancomycin
Arcanobacterium: What may it cross react with? How to troubleshoot this?
Arcanobacterium is beta hemolytic and can cross react with Group G beta hemolytic Strep: THIS is why it is always important to perform a gram stain. (Group G beta hemolytic step will be GPC, Arcanobacterium is GPR)
Listeria monocytogenes epidemiology
Environmental opportunistic pathogen to humans through direct contact with animals, soil, and vegetation
*Primary transmission most often due to ingestion of contaminated foods (meats, veggies, dairy)
Listeria monocytogenes - who does it most often infect?
immunocompromised and neonates due to vertical transmission from mother to fetus
Listeria monocytogenes virulence and pathogenicity
Listeriolysin O - reduce T cell responsiveness
Phospholipases - enable escape from phagosome
Act A - induces hot cell actin polymerization
Corynebacterium diphtheriae epidemiology
Not normal flora - transmission through direct person to person contact via respiratory droplets, exudative pus from skin lesions, or fomites
What is C. diphtheriae virulence due to?
potent cytotoxic exotoxin from a plasmid (tox gene)
S&S of diphtheria
pharyngitis, difficulty swallowing, fever
cell necrosis and exudate forms a tough gray-to-white pseudomembrane that attaches to tissue
Non-toxigenic C. diphtheriae
Causes cutaneous diphtheria that is characterized by nonhealing ulcers and membrane formation (does not have the plasmid tox gene)
What are most C. jeikeium infections associated with? Why?
HAI’s - colonizer of inguinal, axillary, and rectal areas of body (associated with catheters, shunts, medical devices)
C. ulcerans epidemiology and infections
Normal microbiota in humans and cattle; zoonotic infections that usually present as skin infections or pneumonia
C. pseudotuberculosis epidemiology and infections
normal microbiota of various animals such as sheep, goats, horses (zoonotic) infections in humans is rare but may cause suppurative granulomatous lymphadenitis (lungs)
C. pseudodiphtheriticum epidemiology and infections
Normal microbiota of human upper respiratory tract and skin flora
Opportunistic pathogen that gain access to sterile sites and may cause sepsis, endocarditis, pneumonia, and lung abscesses
C. stratium epidemiology/infections
normal microbiota of skin, considered to be nosocomial/HAI due to catheterization - may cause bacteremia, pneumonia, lung abscesses, osteomyelitis, meningitis
C. urealyticum epidemiology/infection
Normal skin flora, big problem for HAIs
Most infections are related to UTIs, wound infections
C. diphtheria: catalase, motility, urease
Catalase +
Nonmotile
Urease -
C. jeikeium: catalase, oxygen requirements, urease, nitrate reduction, hemolysis
Catalase +
Urease -
Nitrate reduction -
Gamma hemolytic
C. pseudodiphtheriticum: nitrate reduction and urease
nitrate reduction +
urease +
C. pseudotuberculosis: urease
Urease +
C. ulcerans: nitrate, urease
nitrate -
urease +
C. urealyticum: nitrate, catalase, urease
nitrate -
catalase +
RAPID urease +
What will enhance the growth of C. urealyticum?
lipid-containing medium (lipophilic organism)
How can you decipher C. diphtheria from other Corynebacterium? What will a positive C. diphtheria look like?
Cystine-tellurite blood agar and Modified Tinsdale agar
Presumptive positive for C. diphtheriae occurs when there is a brown-black halo produced on both media.
What Corynebacterium will have a REVERSE camp reaction?
C. pseudotuberculosis and C. ulcerans
What Corynebacterium is RAPIDLY urease positive?
C. urealyticum
L. monocytogenes media to grow
VERY fastidious - needs lots of things to grow. BHI is most common nonselective media used for cultivation of Listera sp.
Listeria monocytogenes: hemolysis, catalase, motility, bile esculin, CAMP
beta hemolytic
catalase positive
motile at room temp (umbrella motility)
bile esculin +
CAMP + (block/small arrowhead)
Organism with block/rectangular CAMP positive result
L. monocytogenes
What does L. monocytogenes usually cause?
meningitis in neonates/immunocompromised
Organism that is motile at room temp
L. monocytogenes
“tumbling end over end” on wet mount
“umbrella motility” on agar tube
What GPR is easily identified based on its salmon-colored colonies on BAP?
Rhodococcus equi
What is the Elek Plate Testing used for? What is a positive result?
It is used to differentiate C. diphtheriae toxin-producing strains vs. non-toxin producing strains.
The presence of precipitin lines = strain produced the toxins.
What is the lipophilic Corynebacterium?
C. jeikeium
C. diphtheriae: CAMP test
CAMP negative
B. anthracis: motility, hemolysis, morphology on BAP, gram stain
non-motile, gamma hemolytic, “medusa head”/”comet tail” morphology, large rectangular bacilli with centrally located spores
Epidemiology of B. anthracis
Common soil and environmental organism - may be recovered in skin, blood, CSF, or respiratory samples
When are endospores produced?
During harsh environmental conditions to enhance bacterial survival
B. anthracis virulence and pathogenicity
Lethal toxin - kills the cells
Edema toxin - swelling and inflammation of tissue
protective antigen - carrier protein to facilitate LT/ET cellular entry
Cutaneous B. anthracis
Most common infection type - endospores inoculate areas of broken skin.
2-3 days after exposure: small papule appears at site of inoculation
3-7 after exposure: black eschar appears
Gastrointestinal B. anthracis infection
Ingestion of endospores leads to lesions on mouth area, results in N/V/D, vomiting blood
B. anthracis inhalation (what is another name for it, S&S, mortality rates, what do chest x ray reveal)
Called wool sorter’s/rag pickers disease - from breathing in endospores. S&S include 2-5 days of non-productive cough, N/V, respiratory distress, shock, death
Highest mortality rates
Chest x ray reveals pleural effusion and mediastinal widening
B. cereus epidemiology and common illnesses
soil/environmental organism that can cause food poisoning with ingestion of contaminated meats/veggies/rice/grains/dairy
Heat Shock Testing
Used for growth and enhancement of endospore producing bacteria
- Sample heated 60-70C for 30 minutes to kill vegetative cells but keep endospores alive to increase recovery
All labs must report _______ to the CDC with __ days.
B. anthracis; 7 days
> 1 um with no endospore swelling within the cell
vegetative B. anthracis, cereus, thuringiensis
<1 um with no endospore swelling
B. subtilis
How to distinguish B. anthracis from other bacillus spp.
B. anthracis is gamma hemolytic and non-motile
Other bacillus sp. are beta hemolytic and motile
B. anthracis: motility, catalase, colony morphology/hemolysis
non motile
catalase +
large gray and flat with medusa head and gamma hemolytic
B. cereus: motility, hemolysis, gram stain
beta hemolytic, motile, frosted glass appearing bacilli on gram stain
B. cereus: what does it cause? what 2 types?
Food poisoning
Diarrheal: 8-16 hour incubation period with longer duration
Emetic: 1-5 hour incubation period with shorter duration
How to identify B. subtilis from other beta hemolytic and motile bacillus sp.
<1 um cell width
