Aerobic Gram positive bacilli; non-spore forming

Question 1

Name as many most clinically important Gram positive , AEROBIC, NON-SPORE forming bacilli as you can: goal is 7

Answer 1

Listeria, Corynebacterium diphtheriae and C. jeikium, Erysipelothrix, Nocardia, Arcanobacterium, Rhodococcus (cocco/coccobacilli/pleo)

mnemonic: Listen, Corn dip & Corn Jerk!, Erysa KNOWS Archaic Roads!

Question 2

give 3 to 5 characteristics of Listeria compared to Arcanobacterium (differentiate them, but also tell what’s similar)

Answer 2

Both are gram positive aerobic bacilli, with small beta-hemolytic colonies.

Listeria is catalase POSITIVE, CAMP positive, hippurate, and motile (umbrella and tumbling). A cause of bacteremia, meningitits (neonatal as well), encephalitis

Arcanobecterium haemolyticum is catalase NEGATIVE, CAMP test inhibited, NONMOTILE: more often causes pharyngitis/ wound infections.

Question 3

Compare and Differentiate Corynebacterium diphtheriae and C. jeikium

Answer 3

Both are diphtheroid gram positive aerobic rods and catalase positive.

C. diphtheriae is pyrazinamidase negative, and can reduce tellurite (brown/black + halos on Tinsdale or Cistine-tellurite agar), and urease negative.

C. jeikium doesn’t reduce tellurite, is asaccharolytic, and pyrazinamidase positive.

ALso know that diphtheriae causes….diphtheria! if the toxin is present (ELEK) and jeikium causes nosocomial infections especially of prosthetic valves and in immunocomped pts, and is multidrug resistant.

Question 4

What is Leoffler’s agar?

Answer 4

medium used to support production of metachromatic granules in C. diphtheriae, and growth with pleomorphism

Question 5

What test is rapid-positive for C. urealyticum?

Answer 5

urease!

Question 6

Give most likely identification: gram positive bacilli, aerobic, nonmotile, catalase negative, forms small beta-hemolytic colonies on SBA. Gives inhibition of hemolysis on CAMP test bc it inhibits activity of S. aureus’ beta-lysin

ALos, found in mucus mmbrns of livestock, causes pharyngitis esp in older kids, as well as abscess and tissue infections in humans and cows

Answer 6

Arcanobacterium haemolyticum

Question 7

What are 3 to 5 identifying characteristics of Nocardia?

what kinds of infections do they cause?

Answer 7

non spore forming gram positive bacilli, with branching/beaded appearnce (looks like fungi!),

partially acid-fast, produce chalky white colonies that turn orangey when mature, and have musty basement odor

causes pulmonary or disseminated infections esp in immcomped; ALso causes mycetomas, which are soft-tissue infections with macroscopic granules of pus and bacteria that look like sulfur grans

Question 8

Compare Rhodococcus equi to Nocardia

Answer 8

R. equi used to be in the genus Nocardia; the colonies are pink and slimy, not dry or chalky. The gram stain also shows coccobacilli, or diphtheroid bacilli in palisades or chinese letter arrangements—not branching/beaded.

Question 9

Characteristics of Erysipelothrix rhusiopathiae, both identification and source

Answer 9

a gram positive rod, aerobic, that is catalase negative (compared to Listeria), is nonmotile (again unlike Listeria), and H2S positive! causes blackening of TSI butt.

It is zoonotic, from contact with animals causing cellulitis from a wound, resembles erysipelas caused by group A strep.