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Bacteriology > Streptococcus &Enterococcus > Flashcards

Streptococcus &Enterococcus Flashcards

1
Q

Microbiological Characteristics

A

-biocontainment level 2
-gram positive cocci
-aerobic or facultatively anaerobic
-can be fastidious (requires blood or serum in media to grow

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2
Q

Common groups of streptococcus and enterococcus

A
  1. Hemolysis (alpha, beta, gamma)
  2. Lancefield group (surface antigens identified serologically)
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3
Q

How to differentiate streptococcus and enterococcus from staphylococcus?

A

catalase test.

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4
Q

Histology characteristics

A

Streptococcus form chains
*Staphylococcus form clusters

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5
Q

Microbiological characteristics for Streptococcus agalactiae

A

Blood agar: weak beta-hemolysis

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6
Q

Microbiological characteristics for Streptococcus canis

A

Blood agar: strong beta-hemolysis

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7
Q

Microbiological characteristics for Streptococcus equi subspecies zooepidemicus

A

Blood agar: strong beta hemolysis

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8
Q

Microbiological characteristics for Streptococcus dysgalactiae

A

Blood agar: alpha-hemolysis

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9
Q

Microbiological characteristics for Streptococcus suis

A

Blood agar: alpha hemolysis

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10
Q

Microbiological characteristics for Enterococcus faecalis

A

Blood agar: blue/grey colonies

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11
Q

habitat of streptococci and enterococci

A

Streptococci: mucous membrane and respiratory tracts

Enterococci: intestinal tract
*environmental contamination associated with nosocomial infections

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12
Q

Differentiating enterococcus and streptococcus

A

Aesculin test (growth of NaCl)

Positive= enterococcus
Negative= streptococcus

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13
Q

Differentiating streptococcus species

A

Lancefield grouping (agglutination rxn)
- streptococcus suis will not group
-oher groups based on polyysaccharides and lipoteichoic acids

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14
Q

Biochemical ID of enterococcus and streptococcus

A

-commercial biochemical strip

-CAMP test

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15
Q

Virulence factors of streptococcus and enterococcus

A

-MSCRAMMs
-Exotoxins (superantigen- streptococcus pyogenes)
-phage mediated superantigen (streptococcus canis)
-capsule (prevents phagocytosis, some capsules composed of hyaluronic acid distinguishable from some host tissues= may explain post-infection autoimmunity)
-Hemolysins (cytotoxic to eukaryotic cells)
-CAMP factor (pore forming toxin)

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16
Q

S. pyogenes

A

humans
-strep throat, necrotizing fasciitis

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17
Q

S. pneumoniae

A

humans- opportunisti and skin infections

horses- pneumonia
guinea pigs- pneumonia

18
Q

S. agalactiae

A

cattle- chronic mastitis
-contagious (infectious cows=source)
-mostly subclinical disease, not systemically ill

-linked with breakdown of biosecurity (teat hygiene, cleaning milk equipment, hand washing)

-use intramammary antibiotics= penicillin

19
Q

S. dysgalactiae subsp dysgalatiae

A

cattle- acute mastitis
-environmental mastitis from contamination of teats from bedding
-linked with management issues (cleanliness, bedding, access to shelter)
-Treatment= dry cow treatment and teat sealer

20
Q

S. equi subsp equi

A

horses- strangles (abscess of submandibular and retropharyngeal lymph nodes)
-Reside in upper resp tract
-transmitted by contact with nasal secretions/discharge from abscesses; can be direct contact or fomites
-very contagious (100% morbidity, low mortality)
-2-6 day incubation
-75% of horses have immunity to future infections; immunity can be passed in colostrum

ISOLATION IS KEY

21
Q

Treatment for strangles

A

Penicillin is treatment of choice. vaccines available
-long term sequelae can be possible:
1. metastatic abscesses= bastard strangles= spread to lung, liver, mesentery, spleen, kidneys, brain
2. purpura hemorrhagica (vasculitis secondary to deposition of immune complexes
3. Guttural pouch empyema

22
Q

S. canis

A

Cats and dogs- septicemia, wound infections, abscesses, respiratory infections
>Kittens: respiratory, skin and soft tissue, abscesses
>dogs: opportunistic pathogens

*Penicillin is treatment of choice

23
Q

S. canis and fluroquinolones

A

Can be linked with necrotizing fasciitis and toxic shock syndrome
>phage superantigens occur after fluroquinilones. Phage becomes lytic and bursts. Phages will then interact with T cells of dog. Results in large increase of cytokines and can lead to shock, hyperemia, death

24
Q

S. equi subsp zooepidemicus

A

horse- joint infections
cattle- mastitis
pigs- septicemia
poultry- septicemia
cats and dogs- resp infections

25
Q

S. suis effects

A

pigs-meningitis, arthritis, septicemia= high fatality rate
humans- meningitis, hearing loss, septicemia

26
Q

S. suis in pigs

A

Organism enters body through tonsils

-typically affect nursery pigs but can be any age. Associated with moving pigs, over crowded and poor ventilation

-piglets acquire organism from sow and environment at farrowing

27
Q

How is S. suis grouped?

A

Grouped by serotype (what the immune system sees)= 33 serotypes

28
Q

Serotype 2 S. suis

A

-enters through cuts/scratches via nasopharynx/GIT

-most commonly infect people with animal contact (vets, farmers, meat inspectors, butchers)

-leads to high fever, malaise, vomiting, meningitis, toxic shock, coma

29
Q

S. bovis

A

cattle- rumen acidosis
other species- opportunistic infections

-Group D strep that is easily mistaken for Enterococcus

-included in probiotic cultures BUT if isolated from site of infection then it is clinically significant

30
Q

S. bovis as lactic acid producer

A
  1. increased lactic acid produced with high fermentable diets
  2. other rumen microbiota cant metabolize lactate efficiently
  3. Rumen pH drops below 5, killing other organisms
  4. High lactate concentrations in rumen, causes water to somotically flow in from circulation, resulting in dehydration
  5. absorption of lactate leading to systemic acidosis
  6. chemical rumenitis causes damage, allowing organism translocation into portal vasculature and hepatic abcessation
31
Q

Enterococcus species in poultry

A

-mortality in chicks (fecal contamination of eggs)
>first sign is often death
>acute: septicemia (depression, ruffled feathers)

-management is key (prevent stress and other diseases; cleaning and disinfection

-treat with antibiotics if caught early

-must be based on susceptibility

32
Q

Enterococcus species in dogs and cats

A

-opportunistic infections= nosocomial infections

-Can be:
>systemic infections= bacteremia and endocarditis
>localized infections= abdominal cavity, genitourinary tract, soft tissue, respiratory tract

-antimicrobial resistance frequently affects therapeutic selection (beware of intrinsic resistance and know which enterococcus species)

33
Q

Enterococcus and UTIs

A

-uncommonly causes urinary tract infections

**frequently found in uninfected animals - sub clinical bacteriuria. Need to ask if clinical signs are consistent with infection?

34
Q

Specimens to collect

A

Mastitis= milk

Dermatitis/surface= swabs, pus, exudates

Sepsis/death= whole animal, culture of brain fo S. suis meningitis

Respiratory- trans tracheal wash fluid

35
Q

Sample handling

A

-strep susceptible to desiccation
-enterococci is generally tough

-swabs should be sent with transport media
-Do not freeze samples (with exception to milk)

36
Q

Lab ID

A
  1. Culture
    -readily grow on blood agar, some better on chocolate agar, growth improved with cO2 enriched environment
    -growth may take 48hrs
  2. Commercial biochemical test panels
  3. MALDI-TOF or NAAT +DNA sequencing
37
Q

Zoonotic transmission species

A

-S. suis

-S. equi subsp zooepidemicus

-S. canis

38
Q

S. suis as zoonotic disease

A

-primarily associated with pig contact
-serotype 2
-toxic shock syndrome, meningitis, sepsis, deafness on recovery

39
Q

S. equi subsp zooepidemicus as zoonotic

A

-zoonotic transmission from dogs and horses
-drinking unpasteurized milk

40
Q

S. canis as a zoonotic

A

-may be unrecognized
-from dogs

41
Q

Treatment options

A

-Must be guided by susceptibility testing
-never use fluroquinolone for S. canis
-streps and enterococci dont tend to produce beta-lactamsases

42
Q

Enterococcus intrinsic resistance

A
  1. All resistant to cephalosporins
  2. some resistant to vancomycin (not VRE)
  3. E. faecium is inherently resistant to penicillin and aminoglycoside synergism

Bacteriology (20 decks)

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