Media
This type of media where
Additives are used to bring out certain characteristics that cause organisms to look differently
Ex. Sugars for fermentation (Ex. Lactose), Types of hemolysis on blood agar
differential
In the CAMP test a single streak of beta-hemolytic Strep is placed perpendicular to a streak of beta - lysin producing Staph Aureus . After incubation a zone of increased lysis in the shape of an arrowhead is noted. This indicates the presumptive identification of :
Group B Strep ( S. agalactiae )
E. coli .. the most common cause of UTI has what IMVIC reactions ?
++--
What is the cause of Hansen's disease and what animal is it associated with ?
M. Leprae - causes Hansen's disease aka leprocy.. and can be be cultured in foot pads of armadillos
When a urine is cultured with a platinum loop calibrated to deliver 0.001 ml, each
colony grown is equal to:
1,000 CFUs
** 0.01 ml = 100 CFUs
CIN media is typically used for isolation of what gram negative bacteria?
Yersinia
A nasopharyngeal culture grows a predominance of a beta-hemolytic colony on sheep blood agar. The isolate is susceptible to bacitracin. The most likely identification is beta-hemolytic strep group ____
A ( Strep pyogenes)
Which genera of Enterobacteriaceae are usually nonmotile at 36°C?
Shigella, Klebsiella , Yersinia
** Yersinia can be motile at 22C
Which of the following organisms are used as controls for rapid growers and slow growers?
A. Mycobacterium fortuitum and Mycobacterium tuberculosis
B. Mycobacterium avium-intracellulare complex and Mycobacterium tuberculosis
C. Mycobacterium chelonei and Mycobacterium fortuitum
D. Mycobacterium kansasii and Mycobacterium tuberculosis
A. M. fortuitum - fast grower , M. Tb - slow grower
** avium and kansasii - slow growers
chelonei - fast grower
According to the Kirby–Bauer standard antimicrobial susceptibility testing method, what should be done when interpreting the zone size of a motile, swarming organism such as a Proteus species?
ignore the swarming
Thiosulfate–citrate–bile–sucrose (TCBS) agar is used for the isolation of what Gram-negative, facultative anaerobe and comma-shaped bacteria?
Vibrio
If you culture a tissue biopsy from a patient with post streptococcal glomerulonephritis, what
would you expect to grow?
nothing.. post strep infection
Three blood cultures taken from a 30-year-old
cancer patient receiving chemotherapy and
admitted with a urinary tract infection grew
lactose-negative, motile, gram-negative rods
prior to antibiotic therapy. Given the following
biochemical reactions, which is the most likely
organism?
H2S (TSI) = + Indole = + MR = +
VP = Neg Citrate = Neg Urease = +
DNase = + Phenylalanine deaminase = +
Gelatin hydrolysis = +
Ornithine decarboxylase = Neg
A. Proteus vulgaris
B. Proteus mirabilis
C. Serratia marcescens
D. Klebsiella pneumoniae
P. vulgaris
Although P. mirabilis is more frequently recovered
from patients with urinary tract infections, P. vulgaris
is commonly recovered from immunosuppressed
patients. P. mirabilis is indole negative and ornithine
decarboxylase positive but otherwise is very similar to
P. vulgaris.
Which organism, associated with tuberculosis in cattle, causes tuberculosis in humans, especially in regions where dairy farming is prevalent?
M. bovis
** this is also organism used for vaccine
of a smear taken from the periodontal
pockets of a 30-year-old man with poor dental
hygiene showed sulfur granules containing
gram-positive rods (short diphtheroids and some
unbranched filaments). Colonies on blood agar
resembled “molar teeth” in formation. !e most
likely organism is:
Actinomyces israelii
MRSA now makes up the majority of Staph aureus recovered in the lab. The gene responsible for this is the _____ gene and it encodes for an alternate ____
mecA , PBP ( penicillin binding protein)
MRSA now makes up the majority of Staph aureus recovered in the lab. The gene responsible for this is the _____ gene and it encodes for an alternate ____
mecA , PBP ( penicillin binding protein)
An isolate of E. coli recovered from the stool of a patient with severe bloody diarrhea should be tested for which sugar before sending it to a reference laboratory for serotyping?
Sorbitol
What do you call a mycobacteria sp. that produces pigmented colonies in the dark.. give an example
Scotochromogen ex.. M. gordonae, M. szulgai, M. scrofulaceum , M. xenopi
** photochromogens .. buff in dark pigmented in light (M. kansasii, M. marinum M, simiae)
nonphotochromogens- non pigmented in dark and light ( M. avium- intracellulare, M. xenopi)
rapid growers - grow in 3 -5 days (M. fortuitum, M. chelonae, M. smegmatis)
A gram-positive branching filamentous organism recovered from a sputum specimen was found to be positive with a modified acid-fast stain method. What is the most likely presumptive identification?
Nocardia Spp.
An emergency department physician suspected
Corynebacterium diphtheriae when examining the
sore throat of an exchange student from South
America. What is the appropriate media for the
culture of the nasopharyngeal swab obtained
Tinsdale media
This organism :
Usually due to contamination
Staph epidermidis
Which of the following organisms is often
confused with the Salmonella species
biochemically and on plated media?
A. E. coli
B. Citrobacter freundii
C. Enterobacter cloacae
D. Shigella dysenteriae
Citrobacter freundii
C. freundii strains, like Salmonella spp., are
usually H2S producers and may be confused with
Salmonella spp. unless the proper biochemical
tests are utilized. C. freundii and Salmonella spp. are
adonitol, indole, and malonate negative. However,
C. freundii is KCN positive, whereas Salmonella spp.
are KCN negative.
Which class of antibiotics is used for the treatment of serious gram-negative infections as well as infections with Mycobacterium tuberculosis?
Aminoglycosides
A patient with a human bite wound on the
right forearm arrived at the clinic for treatment.
!e wound was inflicted 36 hours earlier, and a
culture was taken by the physician on duty. After
48 hours, the culture results were:
Gram-stain smear = Gram-negative straight, slender
rods
Chocolate agar plate = “Pitting” of the agar by small,
yellow, opaque colonies
Oxidase = + Motility = Neg Catalase = Neg
Glucose = +
Growth in increased CO2 = + Growth at
42°C = Neg
What is the most likely identification of this
facultative anaerobe?
Eikenella corrodens