PATHOGENIC BACTERIA I AND II

• PATHOGEN


  Infectious agent, a microorganism that can cause disease upon colonization of the host. They harbor the required virulence genes for infection (e.g. adherence, invasion and evasion of immune system and/or toxins)
• OBLIGATE PATHOGEN


  Microorganism which must infect a host and cause disease in order to multiply and be transmitted from one host to another
• FACULTATIVE PATHOGEN


  Microorganism which can infect and multiply in hosts but is also capable of multiplying in the environment
• OPPORTUNISTIC PATHOGEN


  Microorganism which does not ordinarily cause disease but under certain conditions (e.g. impaired host immunity) becomes pathogenic
• OBLIGATE INTRACELLULAR


  Can only reproduce inside the infected host cell (e.g. Rickettsia, Ehrlichia, Mycoplasma, Chlamydia)
• FACULTATIVE INTRACELLULAR


  Can survive and multiply intra- and extracellularly (e.g. Mycobacterium, Salmonella)
• EXTRACELLULAR


  Can survive and multiply extracellularly in the periphery of host cells (e.g. Streptococcus group A)
• Gram-Negative bacteria stain pink, Gram-Positive bacteria stain purple
• Gram-Positive bacteria


  • Cocci
  • Bacilli
  • Cocci & coccobacilli
  • Bacilli
• Gram-Negative bacteria


  • Enterobacteriaceae
  • Pseudomonads
  • Legionella
  • Vibrio
  • Campylobacter
  • Helicobacter
• Gram-Negative bacteria


  • Borrelia
  • Treponema
  • Leptospira
  • Haemophilus
  • Bordetella
  • Brucella
  • Pasteurella
  • Neisseria

  
• Gram-Positive bacteria


  • Clostridia
  • Actinomycetes
  • Listeria
  • Bacillus
  • Corynebacterium
  • Staphylococci
  • Streptococci
  • Enterococci

  
• Pathogenic bacteria


  • Extracellular & Facultative
  • Obligate intracellular
• Gram-Positive bacteria


  • Gram-positive cocci
  • Gram-positive rods/bacilli
• Gram-positive cocci


  Reservoir: on skin and mucus membranes of animals and humans -> commensals!
• Gram-positive cocci


  Locations: Upper respiratory tract (nose!), Lower urogenital tract, Gastrointestinal tract
• Staphylococcus


  Species of clinical importance: S. aureus (humans & animals), S. pseudintermedius (dogs & cats), S. hyicus (pigs)
• Staphylococcus


  Pyogenic infections: suppurative infections with pus-filled lesions (~abscess)
• Staphylococcus aureus


  Binds to extracellular fibrinogen in plasma to form a protective capsule
• Staphylococcus pseudointermedius


  Causes pyoderma (local suppurative skin infections) and otitis externa (ear infections) in dogs and cats
• Any skin disease that changes the normally dry, desert-like environment to a more humid environment can predispose the host to bacterial over-colonization
• Staphylococcal mastitis


  S. aureus causes contagious mastitis in cattle and small ruminants, often not cleared by the immune system leading to chronic, low-grade or subclinical infections with production losses
• Streptococcus


  Reservoir: on mucus membranes of animals and humans -> commensals!
• Streptococcus


  Species of clinical importance: S. pyogenes (humans), S. agalactiae (cattle), S. dysgalactiae (cattle), S. equi subsp. equi (horses)
• Streptococcus


  Host-specific suppurative infections, local and systemic including septicemia, throat and adjacent lymph node infections
• Streptococcus equi subsp. equi

  Causes strangles (equine distemper), a highly contagious febrile disease involving the upper respiratory tract with abscessation of regional lymph nodes in equines
• Streptococcal mastitis


  S. agalactiae colonizes milk ducts causing persistent infection with intermittent bouts of acute mastitis, S. dysgalactiae colonizes buccal cavity, genitalia and skin of mammary gland causing acute mastitis in cattle and small ruminants
• Gram-positive rods/bacilli


  Reservoir: Ubiquitous in the environment (herbage, sewage effluent, fresh water, feces from healthy animals)
• Gram-positive rods/bacilli


  Psychrophilic -> growth in fridge!
• Gram-positive rods/bacilli


  Facultative intracellular bacteria that can persist in macrophages, uses actin filaments to travel through cells

  
• Listeria monocytogenes


  Causes listeriosis with three clinical symptoms: septicemia, abortion, encephalitis
• Listeria monocytogenes


  Causes circling disease, silage disease, listeriosis in cattle and small ruminants, with encephalitis being the most readily recognized form
• Listeria monocytogenes can multiply in less acidic pH of spoiled silage, enhancing its growth
• Erysipelothrix rhusiopathiae is widespread in tonsils and intestines of many species, with up to 50% of healthy pigs harboring it</b>
• Erysipelothrix rhusiopathiae


  Causes four syndromes in susceptible animals (pigs 3 months to 1 year old): septicemia, arthritis, endocarditis, dermatopathy (diamond skin disease)
• Corynebacterium pseudotuberculosis


  Facultative intracellular pathogen that causes caseous lymphadenitis (abscessation and enlargement of lymph nodes) in sheep and goats
• Bacillus anthracis


  Aerobes or facultative anaerobes, obligate mammalian pathogen, endospore-forming
• Bacillus anthracis


  Reservoir: ubiquitous in soil, causes anthrax mostly in cattle, virulence factors include capsule and tripartite anthrax toxin
• Bacillus anthracis


  Causes per acute septicemia in ruminants with respiratory distress, shock, bleeding from orifices, and characteristic postmortem findings
• Gram-positive ANAEROBIC rods/bacilli


  • Neurotoxic clostridia (C. tetani, C. botulinum)
  • Histotoxic clostridia (C. chauvoei, C. septicum, C. novyi type A and B)
  • Enteropathogenic and enterotoxaemia-producing clostridia