04 - Aerobic Non-Spore Forming Gram-Positive Bacili

T

T/F: Diphtheroids do not produce exotoxins

Nose, Throat, Nasopharynx, Skin, Urinary Tract and Conjunctivae

Corynebacterium is a common commensal found in what parts of the body?

Respiratory Droplets or Direct Contact

Mode of Transmission of Corynebacterium

C. diphtheriae

Principal human pathogen of genus corynebacterium

F; Heat Labile
F; Single-Chain polypeptide
T

MTF: Characteristics of the diphtheria toxin

1.) Heat stable
2.) Double-chain polypeptide
2.) Three-domain polypeptide

Grayish pseudomembrane over the tonsils, pharynx, and larynx

This is the main clinical finding of C. diphtheriae infection

F; No need for localized infection but needs to be toxigenic to establish systemic toxic effects

T/F: C. diphtheriae needs to be toxigenic to establish a localized infection

Bull neck

This is a clinical finding seen in patients with C. diphtheriae infection due to enlargement of lymph nodes

Beaded rods with clubbed ends

Explain the finding seen in gram-stain in patients with C. diphtheriae

Small, granular, and gray with a small zone of hemolysis

Explain the finding seen in BAP in patients with C. diphtheriae

Tellurite Plate (Modified Tinsdale’s Medium)

This is the selective and differential medium used for C. diphtheriae

Tellurite

Which component of the cysteine-tellurite agar is responsible for being the selective agent?

Brown/Black Colonies

Expected differential reaction finding in cysteine-tellurite agar in patients with C. diphtheriae

T
F; Non-encapsulated
T
F; Grow aerobically on most media

MTF: Morphology of C. diphtheriae

1.) Non-motile
2.) Encapsulated
3.) True branching is rarely seen
4.) Grow anaerobically on most media

Loffler’s serum medium

Corynebacteria grows on this medium much more readily than other respiratory organisms

F; Toxigenicity = Phage Gene while Invasiveness = Bacterial gene

T/F: The toxigenicity of C. diphtheriae is controlled by the bacterial gene while its invasiveness is controlled by the phage gene

ELISA

Which test can be used to detect diphtheria toxin from clinical C. diphtheriae isolates

F; More severe

T/F: C. diphtheriae gravis tends to produce less severe disease than C. diphtheriae mitis

Basis of growth characteristics (Colony Morphology, Biochemical Reactions, and Severity of Disease)

The 4 biotypes of C. diphtheriae is classified according to what?

Presence of neutralizing antitoxin

Resistance to diphtheria depends on what?

On the day the clinical diagnosis is made

When should the diphtheria antitoxin be given?

F; Only those unbound

T/F: The diphtheria antitoxin can neutralize toxins already bound to tissues

T

T/F: Antibiotics may be used to inhibit the growth of C. diphtheriae but it has no effect on the disease process

T

T/F: Levels of diphtheriae antitoxin decline overtime, leading to increased susceptibility in older people

T
F; Low pH
T

MTF: Characteristics of Listeria Monocytogenes

1.) Can survive refrigerator temperature
2.) Survive at high pH
3.) Survive at high salt conditions

Dairy or prepackaged raw produce

Listeria Monocytogenes outbreaks are mainly associated with what foods?

Pregnant women, fetus, and immunocompromised

Listeria monocytogenes infection is most common in which hosts?

4b

Which Listeria monocytogenes serotype causes most of the foodborne outbreaks

Adhesin Proteins (Ami, Fbp A, Flagellin proteins)

This Listeria monocytogenes virulence factor is responsible for bacterial binding to the host cells

Internalins A & B

This Listeria monocytogenes virulence factor interacts with E-cadherin to promote phagocytosis into the epithelial cells

Listeriolysin O

This Listeria monocytogenes virulence factor is responsible for lysing the membrane of the phagolysosome and allows the organism to escape into the cytoplasm of the epithelial cells

Act A

This Listeria monocytogenes virulence factor is responsible for inducing host cell actin polymerization and cause the formation of filopods

Early Onset Syndrome

This form of perinatal human Listeriosis is a disseminated form of the disease characterized by neonatal sepsis, pustular lesions & granulomas

Late onset syndrome

This form of perinatal human Listeriosis causes meningitis between birth & 3rd week of life

T

T/F: Listeria monocytogenes only causes mild gastroenteritis and self-limiting diarrhea in healthy individuals

T
F
T
F; Motile
F; Small zone of hemolysis

MTF: Characteristics of Listeria monocytogenes

1.) Facultative anaerobe
2.) Catalase (-)
3.) Esculin (+)
4.) Non-motile
5.) Non-hemolytic

F
T
T

MTF: Morphology of Listeria monocytogenes

1.) Spore-forming
2.) Gram (+)
3.) Occurs as diplo-bacilli

Ampicillin + Gentamicin

Usual treatment for listeria monocytogenes infection

Trimethoprim-Sulfamethoxazole

Usual treatment for listeria monocytogenes infection in patients who are allergic to penicillin

F; Group A beta-hemolytic streptococci

T/F: Erysipela is caused by Erysipelothrix rhusiopathiae in humans

Erysipeloid (Seal Finger/Whale Finger)

Main clinical manifestation of E. rhusiopathiae

F; (+)
T
F; Alpha-hemolytic
T

MTF: Morphology of E. rhusiopathiae

1.) Gram (-)
2.) Filamentous
3.) Beta-hemolytic on BAP
4.) Bacilli

H2S (+) Butt black

This is a special biochemical property of E. rhusiopathiae on Triple Sugar Iron

Penicillin

Drug of choice for severe E. rhusiopathiae infections

T

T/F: Mild E. rhusiopathiae infections will resolve without treatment after 3-4 weeks

Inhalation

Portal of entry of nocardia

F

T/F: Nocardia may trasmitted from person to person

F; Cell-mediated immunity

T/F: Nocardia is an opportunistic infection seen in patients with impaired humoral immunity

Abscess Formation

Usual pathologic process of nocardia infection

CNS

Hematogenous spread of nocardia from the lung often involves what organ system

N. brasiliensis

This Nocardia species is associated with most cutaneous infections

T

T/F: Nocardia is considered weakly acid fast

T
T
F; Hyphae-like Branching
F; (+)

MTF: Morphology of Nocardia

1.) Gram (+)
2.) Coccobacilli
3.) No branching
4.) Catalase-Urease (-)

Trimethoprim-Sulfamethoxazole

Drug of Choice of Nocardia infection