Module 5.3 Gram Positive Aerobic Rods (Part 2) Flashcards
What are some of the key characteristics of gram-positive aerobic rods, the mycolata group?
- lipid rich outer envelope with mycolic acid
- Facultative intracellular and therefore can survive in macrophages
- cause granulomatous inflammation
- immunity is cellular, type 1
Case Report:
- 5 yo dairy goat, losing weight and not milking well
- hx of deworming and Johne’s testing
- trending downwards for 6 mos
- body was sent to AHL and the report came back with Corynebacterium pseudotuberculosis
What is a common clinical sign you would see? (think gross path)
Caseous lymphadenitis
What are some common characteristic of the Corynebacterium species?
- small gram positive rods, pleomorphic (coccoid, club-shaped, rods)
- Aerobic, 1-2 days for growth
- commensals on the MM and skin
- opportunistic
- mostly pyogenic infections
- host-specific
- main diagnostics are serology and whole blood gamma interferon test (intracellular, type 1 immune response)
Corynebacterium pseudotuberculosis 2-PR-Z
- CONTAGIOUS
- passed from other infected animals
- wound contamination
- typical onion ring structure of caseous lesions
How do we prevent and treat Corynebacterium pseudotuberculosis?
- In vivo intracellular penetration is problematic
- there is issues with intracellular penetration of antibiotics commonly used against gram positive aerobes such as Penicillin G
- since there is no effective therapy, cull based on blood testing
- vaccination not overly efficacious therefore use in endemic regions
What are the common characteristics of the Mycobacterium species?
- very weakly gram positive, rod, aerobic
- large amounts of lipids (mycolic acid) in the cell wall = need acid fast stain
- survives well in the environment
- facultative intracellular pathogens
- slow growing, highly pathogenic
- cause chronic granulomatous infections
Mycobacterium bovis 2-OBL-R-Z
- REPORTABLE
- tuberculosis disease - #1 ds. in the world
- there is a reservoir for domestic and wildlife animals (deer/elk, buffalo, bison)
What is the pathogenesis for tuberculosis? (Mycobacterium bovis)
Aerosol infection (can also be ingestion), local multiplication and uptake by macrophages, containment, reactivation, disease/transmission
- an infected macrophage will commonly cause granulomas
- there is a TH! response with gamma interferon causing macrophage activation
variable outcome depending on cellular immunity
What clinical signs will you see with tuberculosis?
- nodules on the mesenteric LNs, udder, mediastinal LNs, submandibular LNs
How do we diagnose bovine tuberculosis? Mycobacterium bovis
- usually detected at slaughter
- tuberculin test
- test and slaughter
- acid-fast stain
- slow culture
- DNA-based methods
- we do occasionally have detection in Canada through abattoir meat inspection programs and persistent disease in Wood Buffalo National Park
How do we treat bovine tuberculosis? Mycobacterium bovis
- cull
- can use antimicrobial agents in humans
Avian tuberculosis 3-PR-Z?
- chronic bacterial infections
- often entry by air, intestine, dissemination
- control the same as bovine TB
Mycobacterium marinum 3-OPP-Z
- water acquired
- saprophytic, opportunistic
- fast growing organism
- pyogranulomatous skin lesions in humans (fish finger)
Case Report:
- 4 yo cow, declining in lactation losing weight post-calving, watery diarrhea
- emaciated and seriously ill
- body sent to AHL and reported granulomatous proliferation of ileo-cecal mucosa
What is a likely cause?
Mycobacterium avium subspecies paratuberculosis = Johne’s disease!
Mycobacterium avium subspecies paratuberculosis (MAP) 1-PR-Z
- aerobic rods, grown on lipid rich media
- acid-fast bacterium
- infection through milk, pasture or in utero
- localizes lymph nodes
- granulomatous enteritis, cachexia
- numerous asymptomatic shedders
- genetic predisposition (Guernsey, Jersey, Shorthorn)
