Lecture 24. GI Infections 5

Mycobacterium spp. etiology

Aerobic, non-spore forming, gram-positive rods.

what makes Mycobacterium spp. ZN positive

High lipid and mycolic acid content in the cell wall.

due to the ZN positive component of Mycobacterium spp...

they are highly resistant but still susceptible to pasteurization

Common habitats of Mycobacterium spp.

Soil, vegetation, and water.

Media for growing Mycobacterium spp.

Egg-enriched media.

Types of pathogens associated with Mycobacterium spp.

Obligate pathogens, opportunists, and saprophytes.

Colony characteristics of M. tuberculosis

Rough colonies, hard to break; grows in 3-8 weeks at 37°C in aerobic conditions; enhanced by glycerol.

M. tuberculosis

what Mycobacterium spp. is indicated in this image that affects humans

Colony characteristics of M. bovis

Cream colonies, break easily; grows in 3-8 weeks at 37°C in aerobic conditions; inhibited by glycerol, enhanced by pyruvate.

M. bovis

what Mycobacterium spp. is indicated in this image that affects cattle

Colony characteristics of M. avium

Sticky, off-white colonies that break easily; grows in 2-6 weeks at 37-43°C; enhanced by glycerol.

M. avium

what Mycobacterium spp. is indicated in this image that affects domestic poultry

Colony characteristics of M. avium subsp. paratuberculosis

Small, hemispherical colonies with pigment; grows in 16 weeks at 37°C; requires mycobactin.

M. avium subsp. paratuberculosis

what Mycobacterium spp. is indicated in this image that affects ruminants

it is important to remember that tho the M. avium complex is associated with most avian species, it is not associated with....

psittacines

Pathogenesis of Mycobacterium spp.

They multiply intracellularly, causing chronic granulomatous infections.

Cause of mammalian tuberculosis

Mycobacterium tuberculosis complex.

Cause of avian tuberculosis

Mycobacterium avium subsp. avium (serotypes 1-3).

Cause of Johne's Disease

Mycobacterium avium subsp. paratuberculosis (MAP).

Cause of leprosy in humans and cats

Humans: M. leprae; Cats: M. lepraemurium.

Stain used for diagnosing Mycobacterium infections

Acid-fast staining (Ziehl-Neelsen).

Common media for culture of Mycobacterium spp.

Lowenstein-Jensen medium.

Molecular tools for diagnosing Mycobacterium infections

PCR and rRNA sequencing.

Differentiation of M. tuberculosis and M. bovis in the past was done via

Guinea pig and rabbit inoculation.

zoonotic implications of Mycobacterium spp.

M. tuberculosis, M. bovis, M. africanum, M. canettii, M. pinnipedii, M. marinum, M. ulcerans and M. leprae are all zoonotic to humans

Transmission of Johne's Disease

Fecal-oral route, mainly affecting calves.

MAP is brought into the herd by...

subclinical carriers brought into the herd

____% of cows in a herd can be subclinically infected w/ Johne's Disease

50%

Onset of signs of Johne's Disease

Acquired early in life but signs develop at ~2 years old.

Pathogenesis of Johne's Disease

Chronic granulomatous enteritis; bacteria infect Peyer's patches and macrophages in GIT & LNs.

what is the result of infection with Johne's disease that leads to chronic granulomatous enteritis

interference with nutrient uptake and processing

infection w/ Johne's disease

what lead to the physical condition of this cow

Clinical signs of Johne's Disease in cattle

Persistent diarrhea, weight loss/emaciation, ventral/intermandibular edema, death.

Additional signs in dairy cattle or goats with Johne's Disease

Drop in milk yield.

tubercular lesion

how would you describe the appearance of this intestine

How would you describe the Intestinal (tubercular) lesions seen with Johne's Disease

Thickened, corrugated distal small intestine in addition to edematous neighboring lymph nodes.

Diagnosis of Johne's Disease

1. Histopath: granulomatous enteritis w/ acid-fast macrophages

2. PCR, ELISA, or AGID.

Treatment for Johne's Disease

No real treatment; sometimes self-limiting via cell-mediated immunity.

Control of Johne's Disease

1. Separate young

2. feed MAP-free colostrum

3. remove infection sources

4. disinfect.

Disease caused by Mycobacterium ulcerans

Buruli ulcer in humans, koalas, and possums.

Disease caused by Mycobacterium marinum

Tuberculosis in fish, aquatic mammals, and amphibians.