Bacteriology Exam 10 (AFB) Flashcards
What are known to be the smallest self-replicating organisms in nature?
Mollicutes: Mycoplasma and ureaplasma sp. (previously known to be viruses, but are not self-replicating)
What is M. pneumoniae, M. hominis, and U. urealyticum known to cause?
M. pneumoniae: walking pneumonia
M. hominis: UTIs
U. urealyticum: UTIs
T/F: Mycoplasma and Ureaplasma are lacking a cell wall.
True!
What antibiotics are mycoplasma and ureaplasma intrinsically resistant to and why?
Beta-lactams because they lack a cell wall, so there is a lack of target.
Most mycoplasma and ureaplasma are slow growing and highly fastidious. What are the exceptions?
M. hominis is rapid growing
M. pneumonia is aerobic
Can mycoplasma and ureaplasma be gram stained? Why?
No, they have no peptidoglycan wall.
T/F: Mycoplasma and ureaplasma are susceptible to heat and drying agents.
True
What is M. pneumoniae associated with when causing infections? What community of people?
Bronchitis, pharyngitis, or primary atypical walking pneumonia. It is a non-seasonal infection that infects young, healthier people and is more community-acquired. (Causes 50% of all confined population pneumonia such as in military, prisons, or schools).
What can M. pneumoniae be co-infectious with?
Neisseria meningitidis in infants and neonates
What is M. hominis and U. urealyticum associated with when causing infections? In what community of people ?
Both the causative agent of UTIs in immunocompromised people, frequently associated with asymptomatic sexually active people
T/F: M. hominis is NEVER considered normal flora.
False, it is located in the lower genitourinary system of 50% of healthy adults.
U. urealyticum is commonly isolated from ________ and ________ infants.
Premature and low birth weight
What are the special sample collection/processing procedures for Mycoplasma and Ureaplasma?
Lack of cell wall so extremely sensitive to heat and drying.
Transport media = SP4, Shepard’s 10B broth, or 2SP.
Must use dacron/rayon swabs, no calcium alginate or wooden swabs with cotton tips
What do M. hominis and U. urealyticum need in the media to grow?
Cholesterol (SP4, Shephard’s 10B broth, or 2SP)
What is the only mycoplasma to grow on BAP and CHOC?
M. hominis
How is M. pneumoniae typically diagnosed?
By a four-fold titer increase of antibodies
What does SP4 provide for the growth of M. hominis and M. pneumoniae?
Glucose and arginine
What organism gives a fried egg appearance when put onto a glass slide and stained with Dienes or methylene blue?
M. hominis
What organism is most likely if media is acidified from metabolism of glucose to create a yellow pigment, if it is slow growing?
M. pneumoniae
What organism is most likely if media pH is raised due to arginine utilization, turning the media to a orange/red color, and occurs in <24 hours?
U. urealyticum
What organism is most likely if media pH is raised due to arginine utilization, turning the media to a orange/red color, and occurs >24 hours, but less than 72 hours?
M. hominis
Treatment for mycoplasma and ureaplasma (what can you treat with, what can you not treat with)
Cannot treat with beta lactams, SXT, or rifampin
They are susceptible to tetracycline, fluoroquinolones, and some macrolides
What is a big difference between mycoplasma/ureaplasma and mycobacteria?
Mycobacteria have a cell wall, unlike mycoplasma and ureaplasma.
Why must you acid fast stain mycobacteria?
Due to mycolic acid in cell wall, resistant to alcohols and hydrophobic
General characteristics of acid-fast bacilli
Non-motile, non-spore forming rods, high lipid content in cell wall (mycolic acid), slow growing
What is the PPD test?
TB test that injects antigen intradermally and read 48 hours later to see if there is a raised firm area of 10mm or more. If there is, you have had TB
What is the Quantiferon Gold test?
Blood test to determine if you have TB antibodies
What do you use to emulsify a mycobacterium sample?
NaOH - decontaminant (kills non-mycobacterial organisms)
NALC - decongestant (liquifies sputum)
MGIT and LJ agar - solid or liquid
MGIT - liquid
LJ agar - solid
What respiratory specimens are acceptable to identify mycobacterium?
Sputum, bronchial wash, bronchial brush, BAL, leukens trap
What type of specimen may be collected for children under 3 with pulmonary TB?
Gastric aspirate - must be neutralized immediately because stomach acid could destroy bacteria.
What specimens could be acceptable for detection of mycobacterium, although rare?
Urine, stool, tissue/body fluids, and blood cultures
What does an acid fast stain look like?
Blue background, red mycolic acid
What AFB stain will have a black background with bright orange mycobacterium used for screening?
Auramine-Rhodamine fluorochrome
What is the difference between the Ziehl-Neelson and Kinyoun stain for AFB?
Ziehl-Neelson - apply heat
Kinyoun stain - cold stain
What agar is egg-based and contains malachite green to suppress gram positive bacteria?
Lowenstein Jensen (LJ agar) solid media
What is “Gruft”?
LJ agar with antibiotic
What agar for mycobacterium are solid-based?
LJ agar, middlebrook 7H10 and 7H11, and Mitchison’s selective 7H11
What agar for mycobacterium are liquid based?
Middlebrook 7H9 and Dubos Tween Albumin, MGIT tube (rapid ID)
What mycobacterium grows best at 42C?
M. xenopi
How long are mycobacterium incubated? What is considered a rapid grower vs a slow grower?
8 weeks;
Growth >7 days = slow grower
Growth <7 days = rapid grower
What is a photochromogen?
Produce bright yellow pigment ONLY after exposure to UV light
What is a scotochromogen?
Produce bright yellow pigment regardless if in light or dark
What is a non-photochromogen?
Does not produce bright yellow pigment at all (Buff)
What pigment formation category is Runyon group I? What species are included?
Photochromogens - M. kansasii, M. marinum, M. simiae
What pigment formation category is Runyon group II? What species are included?
Scotochromogens - M. scrofulaceum, M. szulgai, M. gordonae
What pigment formation category is Runyon group III? What species are included?
Non-chromagens (MAC) - M. avium, M. intracellularae, M. ulcerans
What category is Runyon group IV? What species are included?
Rapid growers - M. fortiuitum, M. chelonae
T/F: The Runyon groups categorize all mycobacterium.
False; only non-tubercular mycobacterium
What mycobacterium is one of the only niacin positive organism? What does this mean?
M. tuberculosis is niacin positive; because it cannot convert free niacin to niacin ribonucleotide, so niacin accumulates and creates a YELLOW color.
What does a positive niacin test look like? What organism could this be?
Yellow pigment; M. tuberculosis
What mycobacterium is positive for nitrate reduction? Negative? What color would this be?
M. tuberculosis is positive for nitrate reduction, creating a purple/red color, and M. bovis is negative (colorless).
Explain the nitrate reduction test
Add sulfanilamide to nitrate broth.
Red color = positive (nitrate was reduced)
Colorless = inconclusive, move to next step
Add zinc dust
Red color = negative (nitrate still present)
Colorless = positive (nitrate reduced to nitrite)
What organisms are negative/positive for the heat stable catalase test?
Negative = M. tuberculosis
Strong positive >45 mm = M. kansasii
Variable positive <45 mm = other mycobacteria
What organisms are positive for Arylsulfatase? What color is positive?
Positive is red
Rapid growers that are positive = M. fortuitum and M. chelonae
Slow growers that are positive = M. marinum and M. szulgai
What agar can be used for rapid growing mycobacterium?
MAC without crystal violet
Positive color for iron uptake test
Brown
What organisms are included in the M. tuberculosis complex?
**M. tuberculosis, **M. bovis, M. africanum, M. microti, M. canettii
What disease states does M. tuberculosis cause?
Primary, reactivation, or extrapulomary tuberculosis; formation of granulomas in lungs
What are important biochemicals/characteristics for the identification of M. tuberculosis?
Niacin positive
Nitrate positive
Heat stable catalase negative
Non-photo chromogen
Slow growing buff colonies
Growth at 35-37 ONLY
Cording
Treatment for M. tuberculosis
3 or more drugs over a 9 month period; often prescribed with b12 vitamins for liver health
What causes MDR-TB?
Can be caused by resistance and noncompliance of medication
What is the recommended susceptibility testing for TB?
Isoniazid, Rifampin, Ethambutol, and Streptomycin
What does M. bovis cauase?
TB in animals that can be transmitted to humans after the ingestion of contaminated milk (intestinal TB) can be pulmonary and resembles M. tuberculosis
What is the live attenuated strain of M. bovis?
Bacilli-Calmette-Guerin (BCG) immunization for tuberculosis
Biochemical reactions that aid in the identification of M. bovis
Non-photochromogen
Niacin negative
Nitrate negative
Slow growing
What diseases does M. kansasii cause?
Chronic pulmonary disease, extrapulmonary disease, disseminated infections (rare)
Notable features/biochemicals for M. kansasii
- Photochromogen
- Exhibits cording
- Niacin negative
- > 45mm bubbles for heat stable catalase
- Slow growing smooth to rough
- Grows best at 37C
Notable features/biochemicals for M. marinum
Slow growing
Photochromogen
Grows at 28-32C
What is the site of infection and disease states for M. marinum?
- Causes disease in fish, isolated from salt/freshwater aquariums
- Can cause cutaneous infections associated with water (Swimming Pool Granuloma)
- would be isolated from a wound bc limited to the skin
Notable characteristics about M. simiae
- Isolated from monkeys
- Causes rare infections in people with lung damage (rare in US except Texas)
- Photochromogen
- Short coccobacilli
What diseases can M. gordonae cause and where are they acquired from?
Acquired from contaminated drinking water, called “tap water bacillus”
- Can cause meningitis, synovitis, cutaneous lesions, pulmonary disease
Notable characteristics of M. gordonae
Scotochromogen
Yellow-orange colonies
Slow growing in 10-14 days at 22-37C
What diseases does M. scrofulaceum cause?
Cervical lymphadenitis in children (infected cervical lymph nodes)
- Pulmonary with skin lesions
Growth of M. scrofulaceum
Scotochromogen
Yellow-orange colonies in 4-6 wks at 25-37C
Growth of M. xenopi
OPTIMAL GROWTH 42C
NO GROWTH 25C
Slow growth 37C
Non-photochromogen with “birds nest morphology”
Epidemiology/Diseases caused by M. xenopi
Found in hot water taps and birds, causes rare slow progressing pulmonary infections
What diseases does M. szulgai cause?
Pulmonary diseases, lymphadenitis, BURSITIS (inflammation of joints)
Identification of M. szulgai (growth)
Scotochromogen at 37C
Photochromogen at 22C
What is the most common NTM causing tuberculosis in the US?
M. avium complex (MAC)
What is included in the MAC?
M. avium, M. intracellulare
Where is MAC acquired (site)?
Environmental sources (soil, water, house dust)
What infections does MAC cause?
Pulmonary TB, systemic TB (HIV), and cervical lymphadenitis in children
What does MAC look like in lymph node biopsy (notable feature)?
AFB inside of macrophages
Growth of MAC
Non-chromogen
Slow growing smooth colonies that turn yellow with age
Growth at 37C
What diseases can the M. terrae complex cause?
Septic arthritis, synovitis –> affects joints
Where is M. terrae complex acquired from (site)?
Soil, vegetables
What diseases does M. haemophilum cause and in what group?
Immunocompromised; causes swellings/ulcers/abscesses, draining fistulas and joint disease in Bone Marrow transplant patient
Growth of M. haemophilum
Requires hemin for growth
Grows at 28-32C
No growth at 37C
Non-chromogenic
What does M. ulcerans cause?
Painful nodule after trauma that develops into an ulcer
Growth of M. ulcerans
Grows 30-33C
NG at 37C
Little growth at 25C
Nonchromogenic; slow growing
Smooth to rough buff colonies
What are “rapid growers”
Growth in less than 7 days
where is M. fortuitum found?
Soil, dust water
What diseases does M. fortuitum cause?
Skin and soft tissue infections in catheter/IV/injection sites
M. chelonae infections
Disseminated cutaenous infections (similar to M. fortuitum
What organism is M. abscessus closely related to?
M. chelonae
Where is M. abscessus found and what disease state may it cause?
Tap water; may cause lung disease, otitis media, or disseminated cutaneous infections
What disease does M. leprae cause?
Hansens disease/Leprosy
What part of the body does Leprosy/Hansen disease affect?
Skin, mucous membranes, and peripheral nerves. May cause tuberculoid leprosy or lepromatous leprosy
Diagnosis for M. leprosy
Demonstrate acid fast bacilli on skin biopsy
Inoculate mouse foot pads to demonstrate disease (major swelling)
M. genavense
Causes disseminated infections in HIV patients; only recovered from liquid media
Where is Nocardia found and what infections may it cause?
Environmental organism found in soil/plants
May cause pulmonary infections after inhalation in immunocompromised patients
Causes cutaneous infection (thorn, splinter) may present the same as a fungal infection
Smell of Nocardia
Earthy
What medias will Nocardia grow on?
BCYE, regular media, Thayer Martin
ID of Nocardia
Beaded, branching GPRs that are partially acid fast, chalky orange-tan to reddish colonies, aerial hyphae may be visible under dissecting microscope
Treatment for Nocardia
Drainage and surgery; Sulfonamides
Unique features of Rhodococcus equi
Has salmon pink mucoid colonies
Soil organism
