Week 9

• Staphylococcus

  Gram positive cocci

  Catalase positive, Coagulase (Staphylococcus aureus is positive) turns serum fibrinogen into fibrin, Clotting

  Non-spore forming, non-motile

  Facultative aerobes

  Commensals of mammals - skin, nares, mucous membranes; opportunistic pathogens causing pyogenic infections (pus)
• Staphylococcus aureus

  Coevolved with human host over long time with multiple human to animal host jumps, but animal to human jumps are less frequent

  Six biotypes with different phenotypic properties
• Staphylococcus aureus strains

  • Livestock/ruminant strains: CC97, CC133, CC522, CC151, CC398
  • Poultry: ST385
  • Rabbits: ST121
  • Companion animals: CC8, CC15, CC22, CC30, CC45
• Staphylococcus aureus virulence factors

  • Protein A: Immune evasion, Bind Fc portion of IgG and inhibits opsonization
  • Leukocidin: Immune evasion, Leucocidal
  • Coagulase: Immune evasion, "Hide" bacteria from polymorphonuclear leukocytes (Neutrophils, eosinophils, basophils)
• Staphylococcus aureus is a major cause of mastitis in dairy cows, leading to significant economic loss
• Bovine staphylococcal mastitis

  • Reduced yields, clotted, watery, or bloody milk, Loss of milk, Need for veterinary intervention
  • Infection leads to massive influx of leukocytes into the udder
• Transmission of bovine staphylococcal mastitis

  1. Udder to udder

  2. Milking machines

  3. Farmer's hands

  4. Contaminated bedding
• Forms of bovine staphylococcal mastitis

  • Peracute: Necrosis, udder discoloration, Swollen quarters, sore on palpation, Fever, depression, anorexia
  • Acute: Severe swelling of affected gland, Purulent secretion with clots, Extensive fibrosis
  • Chronic: Elevated somatic cells counts, Episodes of bacterial shedding, Inflammatory response, Blockage of ducts and atrophy of alveoli
• Coagulase negative staphylococci are increasingly recognized as etiologic agents of intramammary infections
• Coagulase negative staphylococci causing intramammary infections


  • S. chromogenes, S. simulans, S. xylosus, S. epidermidis, S. hyicus, S. haemolyticus
• Diagnosis of bovine staphylococcal mastitis

  1. California mastitis test - field conditions, DNA in nucleated milk cells

  2. Somatic cell count - early mastitis detection (>200,000 = infected)

  3. Bulk tank somatic cell count - detection of subclinical or chronic mastitis
• Control of bovine staphylococcal mastitis

  1. Proper milking technique

  2. Good hygiene at milking time

  3. Single use paper towels to dry teat

  4. Milker should wear gloves

  5. Teat dip after milking (1% iodine)
• Treatment of bovine staphylococcal mastitis

  1. Detect subclinical infections and cull chronic cows

  2. Segregate infected cows

  3. Prevent introduction of positive cows to the herd

  4. Individual treatment with penicillinase-resistant β-lactams

  5. Dry cow therapy after drying off

  6. Vaccines
• Botryomycosis

  Bacterial granuloma or staphylococcal pseudomycetoma

  Chronic suppurative infection

  Granulomatous inflammatory response, Protection from antibiotics and phagocytosis leads to chronicity

  Poorly circumscribed, firm lesions that may or may not be painful, Lesion center may be ulcerated or drain, "Grains of sand" in exudate

  Splendore-Hoeppli phenomenon (bacteria encapsulated by eosinophilic material)
• Organisms causing botryomycosis

  • S. aureus, P. aeruginosa, and E. coli
  • Streptococcus spp., Pseudomonas spp., Proteus spp. ocassionally coinfect
• Treatment of botryomycosis

  1. Prolonged antibiotics

  2. Surgical excision

  3. Radical debulking
• Staphylococcus aureus infection in birds

  Bumblefoot/sore hocks (ulcerative pododermatitis)
• Prevention of bumblefoot/sore hocks

  1. Dry and clean bedding

  2. Trim talons and claws

  3. Correct diet
• Treatment of bumblefoot/sore hocks

  1. Reduce swelling and discomfort

  2. Disinfection

  3. Drying and bandaging

  4. Surgery
• Staphylococcal infections in other hosts

  • Small ruminants: Mastitis and septicemia
  • Lambs: Fatal toxemia, Chronic disease with organ abscess formation
  • Goats: Contagious pustular dermatitis (secondary to parapox virus)
  • Sheep and goats: Morel's disease (abscesses in superficial lymph nodes, mandibular region)
  • Poultry: Bones and joints (septic arthritis, subdermal abscesses, gangrenous dermatitis, and septicemia)
• Staphylococcus pseudintermedius

  Coagulase positive

  Hard to differentiate from S. intermedius and S. delphini
• Pyodermafrom Staphylococcus pseudointermedius

  Skin disease with pus, Impaired defense mechanisms permit secondary bacterial invasion (food allergy, endocrine disease, or other immuno-suppressive conditions)
• Types of pyoderma

  • Primary: Transient and non-recurrent insult
  • Secondary: Persistent or recurrent underlying problem, More common, overinfection
  • Surface pyoderma (epidermal layers immediately under stratum corneum, Puppy pyoderma, fold pyoderma, "hot spots" (pyotraumatic dermatitis), mucocutaneous pyoderma)
  • Superficial pyoderma (upper layers of the skin and hair follicle)
  • Deep pyoderma (infection deep within the hair follicle, with or without follicular rupture (furunculosis))
• Otitis externa from Staphylococcus pseudointermedius

  More common in dogs and cats than rabbits

  Can be acute or chronic, unilateral or bilateral

  Inciting cause must be addressed to prevent recurrence
• Clinical signs of otitis externa

  • Head shaking, pain, malodor, erythema, erosion, ulceration, swelling, and/or seruminous gland inflammation
• Otitis externa is distal to the tympanic membrane, the ear pinna may or may not be involved
• Differential diagnoses for otitis externa

  • Parasites, fungi, viruses, endocrine/autoimmune disease, foreign body, medicating reactions, overcleaning
• Staphylococcus hyicus

  Coagulase variable in tubes (mostly positive)

  Microbiota of swine (also in poultry) - skin, nasal cavity, conjunctiva, vagina, and prepuce

  Opportunistic pathogen with exfoliative toxins, highly contagious, skin abrasions facilitate entry
• Staphylococcus hyicus in pigs (greasy pig disease)

  • Dirty, brown, greasy, wet skin, Sebaceous exudation
  • Morbidity can reach 20%, mortality 80% within 3-5 days
  • Mainly in sucking and weaned pigs younger than 8 weeks
  • Localized forms may occur eartips, head, flanks, and extremities
  • Pyelonephritis and arthritis less frequent
• Staphylococcal toxic shock syndrome

  Rare disease, acute emergency in dogs

  Severe, diffuse, generalized erythema

  Edema

  Disseminated intravascular coagulopathy

  Caused by staphylococcal exotoxins with superantigen activity leading to excessive cytokine production
• Methicillin-resistant Staphylococcus aureus (MRSA)

  Endemic in human hospitals

  Emergence of ST398 in Dutch pigs, dogs, horses, and cats

  Resistant to all beta-lactams except new anti-MRSA cephalosporin, Transpeptidase PBP2A of lower affinity for beta-lactams, multiresistant strains

  Asymptomatic human carriage in nares

  Occupational risk
• Diagnosis of staphylococci

  Grow on non-enriched media

  Differentiate staphylococci vs streptococci (catalase positive vs catalase negative)

  Coagulase test

  Hemolytic pattern and biochemical profiles

  MALDI-TOF mass spectrometry

  Molecular based methods
• Enterococcus and Streptococcus

  Catalase negative

  Hemolytic (α-partial, β-complete, Ɣ-no hemolysis, growth in 6.5% NaCl = Enterococci)
• Streptococci

  • Only grow on media containing blood serum
  • Commensals in upper respiratory, intestinal, and lower genital tract
  • Transmitted via inhalation, ingestion, sexually, congenitally, and indirectly via hands and fomites
• Lancefield grouping

  Serological identification of cell wall or capsular antigens, 20 Lancefield serogroups
• Streptococcal virulence factors

  • Invasion: Streptokinase, Hyaluronidase
  • Adhesion: Protein F
  • Evasion: M protein, Hyaluronan
  • Toxins: Streptococcal pyrogenic exotoxins, Lipoteichoic acid
• Streptococcus equi subsp. equi

  Obligate pathogen with very restricted host range (horses), β-hemolytic, Lancefield group C, Prevalent worldwide, Remarkably homogenous, clonal
• Transmission of Streptococcus equi subsp. equi

  Inhalation or ingestion after direct contact with discharges from infected horses or contaminated environment (can survive at least 3 months in environment)
• Strangles (Equine distemper)


  Etiology Streptococcus equi subsp. equi

  Upper respiratory tract + head and neck lymph nodes of equines (adenitis), Primarily in younger horses, Older horses that are immunologically naive
• Pathogenesis of Strangles

  Enzymes/toxins cause rhinitis, pharyngitis and fever, Spread to local lymph nodes causing lymphadenitis and abscess formation

  Progressive expansion of infected lymph nodes results in rupture externally to skin surface or internally to guttural pouch

  Bacteremia, vasculitis

  Mesenteric nodes may be involved