7 – Streptococcus, Enterococcus Flashcards
Microbiology Characteristics
- Biocontainment level 2
- Gram-positive cocci
- Aerobic or facultatively anaerobic
- Can be fastidious
Commonly grouped by
- Hemolysis
- Lancefield group (surface antigens IDed serologically)
Fastidious
- Requires blood or serum in media to grow
How do you differentiate Streptococcus+Enterococcus from Staphylococcus
- Using catalase test
- Staphy=positive
- Strept+Entero=negative
Sterp vs. Entero: 2 tests
- Aesculin test
- Growth in NaCL
Streptococcus on agar
- Chains
E. faecalis on blood agar
- blue/grey colonies
- non-hemolytic
Natural host or habitat
- Host associated, part of normal microbiota
o Mucous membranes and respiratory tract: Strept
o Intestinal tract: Entero - Carriers are primary source
Environmental contamination with Enterococcus species associated with
- Nosocomial infections
Taxonomy
- Biochemical ID
- Lancefield grouping
Biochemical ID
- CAMP test
o Looking at enhancing of hemolysis of one organism due to the presence of another
o Positive=enhances it - Commercial biochemical strips
Lancefield grouping
- Groups A, B, C, F, G are polysaccharides
- Group D is a lipoteichoic acid
- *if antigen present=glandular appearance
- **some don’t group well (S. suis)
Virulence factors
- MSCRAMMs
- Exotoxins
- Phage mediate superantigen
- Capsule
- Hemolysins
- CAMP factor
Capsule
- Prevents phagocytosis
- Some composed of hyaluronic acid indistinguishable from some host tissues (may explain post-infection autoimmunity)
Hemolysins
- Cytotoxic to eukaryotic cells
CAMP factor
- Pore forming toxin
Mozart’s death
- Epidemic of deaths involving edema
- Previous to death: inflammatory fever
- *may have suffered Strept throat
o Had post-streptococcal glomerulonephritis
o *infection may stimulate production of cross-reactive antibodies
Clinical significance: S. pyogenes
- Humans
- Ex. strept throat, necrotizing fascilitis
Clinical significance: S. pneumoniae
- Humans: opportunistic and skin infections
- Horses: pneumonia
- Guinea pigs: pneumonia
Clinical significance: S. agalactiae (mastitis)
- CONTAGIOUS mastitis
- Source=infected cows
- Mainly subclinical (not systematically ill)
- Disease suggests breakdown of biosecurity
- Intra-mammary antibiotics (*many remain penicillin susceptible)
Breakdown of biosecurity: S. agalactiae
- Teat hygiene
- Cleaning milk equipment
- Hand washing
Clinical significance: S. dysgalactiae (mastitis)
- ENVIRONMENTAL mastitis
- Contamination of teats from environment/bedding
- Often subclinical
- Suggests management issues
- Treatment: dry cow treatment and teat sealer
Management issues: S. dysgalactiase
- Improve cleanliness
- Better bedding
- Access to shelter
Clinical significance: S. uberis in bovine milk
- CHAINS of gram-positive cocci
Clinical significance: S. equi subsp.equi (strangles)
- Normal inhabitant of upper respiratory tract
- 2-6 day incubation period
- High morbidity: 100%
- Low mortality: 10%
- *PENICILLIN is treatment of choice
- 75% who survive=resistance
- Transfer of immunity in COLOSTRUM
- Vaccines available
‘stangles’
- Abscessation of submandibular and retropharyngeal lymph nodes
S. equi subsp. Equi: strangles transmitted by
- Contact with nasal secretions form abscesses
- Direct contact or fomites
- Very contagious
- ISOLATION IS KEY: prevent transmission
Long term sequale following infection of S. equi subsp equi is possible
- Metastatic abscesses (‘bastard strangles’): spread throughout body
- Purpura hemorrhagica: vasculitis (Type III hypersensitivity)
- Guttural pouch empyema
Clinical significance: S. canis
- Infections not limited to particular anatomical site
- *penicillin is treatment of choice
- Necrotizing fasciitis and toxic and toxic shock syndrome (TSS)
Clinical significance: S. canis in kittens
- Respiratory
- Skin and soft tissue infections
- Abscessation
Clinical significance: S. canis in dogs
- Opportunistic pathogens (urinary, wounds, mammary)
Necrotizing fasciitis and TSS
- Phage superantigens expressed following exposure to FLUROQUINOLONES
1. Lysogenic phage into bacteria chromosome
2. When treat S. with fluroquionlones (interfere with DNA metabolism)=SOS response and get lytic phase of phage=bacteria burst
3. Phages interact with T-cells OUT of control=massive release of cytokines=shock=hypovolemia=death
Clinical significance: S. suis is cause of
- Meningitis
- Arthritis
- Septicemia
- Sudden death
- *high case fatality rate
- *early treatment may be effective
Clinical significance: S. suis
- Affects nursery pigs, but can affect any age
o Acquire from sow and environment at farrowing - Associated with moving pigs, over-crowding and poor ventilation
- *enters body through TONSILS
- *discoloured ears and snout
Clinical significance: S. suis grouped by serotype
- Defined by capsular antigens
- Currently 33 serotypes
Clinical significance: S. suis, zoonotic infections primarily associated with serotype 2
- Most commonly people with animal contacts
o Pig farmers, vets, workers, abattoir workers, meat inspections - High fever
- Malaise
- Vomiting
- Meningitis
- Toxic shock
- Coma
- *human outbreak in China in 2005
- *enters through cuts/scratches (also nasopharynx, GIT)
Clinical significance: S. bovis
- D group, easily mistaken for Enterococcus or Viridans Strept
- Included in some probiotic cultures
- *role in rumen acidosis (grain overload)
Clinical significance: S. bovis, if isolated from suspect infection
- Should consider CLINCALLY SIGNIFICANT
o Wide variety of infections in people
o Opportunistic infections in dogs/cats
Clinical significance: S. bovis lactic acid producer
- Increase lactic acid produced with high fermentable diets
- Other rumen microbiota can’t metabolize lactate efficiently enough
- Rumen pH falls below 5=kills other organisms
- High lactate concentrations in rumen=water osmotically flows in from circulation=DEHYDRATION
- Absorption of lactate leading to SYSTEMIC ACIDOSIS
Chemical rumenitis causes
- Damage
o Allows organism translocation into portal vasculature and hepatic abscessation
Clinical significance: Enterococcus spp. (chickens)
- Mortality in chickens
o *fecal contamination of eggs - Management is key (prevent stress, cleaning, disinfect)
- Treat with antibiotics if catch early
- MUST be based on susceptibility test results
Clinical significance: Enterococcus spp. (chickens), acute
- Septicemia (depression, ruffled feathers)
- Some causes: only dead birds, first sign=death
Clinical significance: Enterococcus spp. (chickens), subacute to chronic
- Depression
- Loss of condition
- pyrexia
Clinical significance: Enterococcus spp. (dog and cat)
- opportunistic infections (nosocomial infections)
- *antimicrobial resistance
o Intrinsic and aquired
Clinical significance: Enterococcus spp. (dogs and cats) most commonly reported
- systemic infections: bacteremia, endocarditis
- localized infections: abdominal cavity, genitourinary tract, soft tissue, respiratory tract
Clinical significance: Enterococcus hirae(dog and cat)
- associated with GI infections in dogs/cats
Clinical significance: Enterococcus spp. (dog and cat), uncommonly causes URINARY tract INFECTIONS
- frequently encountered in uninfected animals
- ‘sub-clinical bacteriuria’
- *are there clinical signs consistent with infection?
Specimens to collect
- Mastitis: milk
- Dermatitis/surface: swabs, pus, exudates
- Sepsis/deat whole animal, culture brain for S. suis meningitis
- Respiratory: trans-tracheal wash fluid
Sample handling
- Stept susceptible to desiccation
- Entero generally pretty tough
- Swaps sent with transport media
- Do NOT freeze samples (except milk)
Laboratory ID
- Easily grown on ‘standard’ lab culture
o Most readily grow on blood agar (some better on chocolate agar)
o May improve growth with CO2 enriched atmosphere - Growth may take 48hrs
- Commercial biochemical test panels=helpful
- MALFI-TOF
- NAAT+DNA sequencing
- May want to ID S. suis serotypes
Zoonotic transmission: S. suis
- Primarily associated with pig contact
- Serotype 2
- TSS, meningitis, sepsis, deafness on recovery
Zoonotic transmission: S. equi subsp. Zooepidemicus
- From dogs and horses
- Drinking unpasteurized milk
Zoonotic transmission: S. canis
- From dogs
- May be underrecognized
Treatment options: Enterococcus spp
- MUST be guided by susceptibility testing
- *all are intrinsically resistance to cephalosporins
- Some intrinsically resistance to vancomycin (NOT VRE)
Treatment options:
- Streps and enterococci don’t tend to produce beta-lactamase (amox+clav offers no advantage over amox)
- Intrinsic resistance is important consideration (particularly for Enterococcus spp.)
- Strep: often think penicillin
Sequelae
- Negative after affect
Glomerulonephritis
- Inflammation that involves the capillaries of the renal glomeruli
Bacteriophage (phage)
- Virus that infects bacteria
