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Bacteriology and Mycology > Streptococcus and Enterococcus > Flashcards

Streptococcus and Enterococcus Flashcards

1
Q

Streptococcus spp.

A
  • First described in Germany in 1868
  • Over 98 spp. (pathogenic and nonpathogenic)
  • Gram positive, nonmotile cocci
  • Facultative anaerobes
  • Single, pairs, and long chains
  • Widely distributed
  • Environmentally resistant
  • Commensals of upper respiratory, alimentary, and lower genital tracts
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2
Q

Catalase test

A
  • Generally catalase negative
  • Exceptions:
  • -Streptococcus didelphis
  • Catalase is an enzyme that breaks down hydrogen peroxide into water and oxygen
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3
Q

Streptococcus didelphis

A
  • Dermal septic necrosis in opossums

- Affects tip of tail, toes, eyes, ears, etc.

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4
Q

Hemolysis on blood agar

A
  • Alpha = green discoloration
  • -Partial hemolysis
  • -Commensal streptococci and enterococci
  • Beta = clearing of agar around colony
  • -Complete hemolysis
  • -Most pathogens are in the beta hemolytic group
  • Gamma - non-hemolytic
  • -Commensal streptococci
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5
Q

Virulence factors

A

=Help organism evade defenses

  • Capsule (antiphagocytic with hyaluronic acid)
  • M protein (antiphagocytic surface protein)

=Help with attachment
-M protein (adhesin that binds fibrinogen)

=Help with spread
-Streptokinases (promotes dispersion (plasminogen activation –> fibrin hydrolyses) and degrades clots)

=Help with damage

  • Streptolysins (direct cytotoxins (lyse neutrophils, macrophages, RBCs, and platelets))
  • Pyrogenic exotoxins (immune-mediated: some are superantigens)
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6
Q

Transmission

A
  • Inhalation
  • Ingestion
  • Sexual contact
  • Congenital
  • Via hands/fomites
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7
Q

Typical presentation

A
  • Pyogenic infection
  • -Abscess
  • -Sequelae:
  • –Immune mediated lesions
  • –Toxemia
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8
Q

Lancefield grouping

A
  • Beta-streps (and milk isolates)
  • Separated by groups (exceptions: S. pneumoniae and S. uberus)
  • Agglutination test: uses antibodies to surface carbohydrate antigens
  • Groups A-W (A-G are important in vet med)
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9
Q

Group A streps

A
  • Mostly human infections
  • Not considered normal flora of veterinary species
  • S. pyogenes (strep throat)
  • S. pneumoniae (an aggressive infection, abrupt and overwhelming, due to superantigens)
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10
Q

S. pyogenes

A
  • Bovine mastitis (rare)
  • Lymphangitis in foals
  • Can cause disease in other species
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11
Q

S. pneumoniae

A

-Reports of pneumonia in guinea pigs, rats, horses, non-human primates (+/- meningitis)

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12
Q

Group B streps

A

-S. agalactiae (bovine contagious mastitis)

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13
Q

S. agalactiae

A
  • Ruminants - contagious (not normal flora), chronic mastitis
  • Horses - genital tract infections (rare)
  • Dogs - endocarditis, neonatal sepsis
  • Cats - kidney and uterine infections
  • Humans - neonatal sepsis/meningitis
  • -Pregnant women are tested for group B strep
  • -If positive, receive IV antibiotics a few hours prior to vaginal birth
  • Contagious mastitis in dairy cattle
  • -Obligate mammary pathogen
  • -ID aided by CAMP test
  • –Hemolytic synergism: Staphylococcal beta toxin and CAMP factor of S. agalactiae (positive CAMP test)
  • –Creates zone of enhanced hemolysis
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14
Q

Bovine mastitis streptococci

A
  • Contagious
  • -S. agalactiae (Group B)
  • Environmental
  • -S. dysgalactiae ssp. dysgalactiae (Group C)
  • -S. equi ssp. zooepidemicus (Group C)
  • -S. uberis (doesn’t group)
  • -S. pyogenes (Group A)
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15
Q

ADDL bulk tank culture report

A
  • Contagious
  • -Streptococcus agalactiae
  • -Staphylococcus aureau
  • -Mycoplasma spp.
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16
Q

Group C streps

A
  • S. dysgalactiae ssp. dysgalactiae
  • S. dysgalactiae ssp. equisimilis
  • S. equi ssp. equi
  • S. equi ssp. zooepidemicus
17
Q

S. dysgalactiae ssp. dysgalactiae

A
  • Bovine acute mastitis (environmental strep)
  • Lamb polyarthritis (septic)
  • Report of a litter of great dane puppies with systemic neonatal infection and death
18
Q

S. dysgalactiae ssp. equisimilis

A
  • Various suppurative conditions in various species
  • Dogs: sepsis, dermatitis, pneumonia, abscesses, UTIs
  • Horses: abscesses, endometritis, abortion, mastitis, wound infections
  • Swine: secondary penumonia
19
Q

S. equi ssp. equi

A
  • Strangles
  • Genital infections
  • Mastitis
  • Other suppurative conditions
20
Q

Equine strangles

A
  • Not normal flora
  • Fever, purulent rhinitis/pharyngitis
  • Upper airways, guttural pouches
  • Abscessed lymph nodes, typically mandibular and pharyngeal
  • May become systemic = bastard strangles
  • Chronic carrier state possible (e.g. guttural pouch)
  • Diagnosis
  • -Culture - nasal swab/wash, abscess
  • -M protein PCR
  • Antibiotic treatment may promote bastard strangles
  • Quarantine; very contagious
  • Most that recover (~75%) develop protective immunity
  • Vaccination for high-risk horses
21
Q

Purpura hemorrhagica

A
  • Noncontagious , immune-mediated vasculitis
  • -Edema of head, ventral abdomen, and limbs
  • -Petechial hemorrhages of mucous membranes
  • -Life-threatening
  • Rare complication of bacterial/viral infections:
  • -1-17% of strangles cases develop this, usually 1-2 weeks after recovery
  • Associated with high antigenic load and exaggerated immune response
  • -Immune complexes: M-protein and antibody
  • -Neutrophils release lysosomal enzymes and radical oxygen species –> compromise blood vessel integrity
22
Q

S. equi ssp. zooepidemicus

A
  • Normal flora in oral cavity, pharynx, upper respiratory tract, and genital tract
  • Opportunistic infections
  • -Pneumonia
  • -Joint/naval infection (newborn/foal)
  • –Originates from the mare genital tract (normal flora)
  • -Abscesses, arthritis, osteomyelitis, endometritis, and mastitis
  • Cattle: metritis and mastitis
  • Swine (1-3 weeks): septicemia and arthritis (increased cases in 2019)
  • Poultry: septicemia and vegetative endocarditis
  • Lambs: pericarditis and pneumonia
  • Guinea pigs: cervical lymphadenitis
  • Dogs:
  • -Progressive pneumonia (may start like mild kennel cough)
  • -Pyrexia, dyspnea, tachycardia
  • -Death without premonitory signs or within 48 hours of respiratory signs
  • -Sepsis reported in racing greyhounds
  • Cats:
  • -Progressive pneumonia
  • -Purulent rhinosinusitis
  • -Meningitis; extension of otitis media/interna
23
Q

Group D streps

A
  • S. gallolyticus ssp. gallolyticus
  • S. suis
  • Enterococcus spp.
24
Q

S. gallolyticus ssp. gallolyticus

A
  • Previously S. bovis biotype I
  • Pigeons, goslings, chickens
  • Septicemia in domestic birds, endocarditis, arthritis, osteomyelitis, opportunistic infections
25
Q

S. suis

A
  • Classified by capsule antigens (1-34)
  • Virulence factor - Suislysin
  • -Causes tissue damage
  • Septicemia (–> endocarditis, polyarthritis, meningitis, pneumonia)
  • Fading pig syndrome
  • -3-12 weeks old
  • -Respiratory or CNS signs
  • Other host species:
  • -Septicemia in birds has been reported
  • -Rarely isolated from ruminants and horses
  • Type II - zoonotic
  • -Some association with swine (farm, slaughter house, raw pork consumption)
  • -Clinical signs:
  • –Meningitis (most common)
  • –Septicemia w/o meningitis
  • –Endocarditis (rarely)
  • -Serious infections –> deafness, ataxia
  • -Low mortality
26
Q

S. porcinus

A
  • Cervical lymphadenitis
  • Jowl, head, neck abscesses
  • Carcass may be condemned at slaughter
27
Q

S. canis

A
  • Commensal of skin and mucosa of dogs, cats, rats, mice, rabbits, minks, and foxes
  • Leading strep infection in dogs
  • Neonatal infections
  • Some suppurative conditions
  • -Meningoencephalitis
  • -Rhinitis/necrotizing sinusitis
  • -Necrotizing fascititis
  • Sporadic opportunistic pathogens
  • Outbreak suggests spread of virulent strain
  • Culture/sensitivity - very susceptible on MIC panels, yet can cause severe disease
28
Q

Necrotizing fasciitis

A
  • Rapidly developing cellulitis of soft tissues of fascia –> necrosis of soft tissue –> may lead to STSS
  • Flesh eating bacteria
  • Extensive necrosis and gangrene of skin and underlying tissues: usually limbs, painful
  • Minor wound –> severe with exudate along fascial planes (24-72 hours)
29
Q

Enterococcus spp.

A
  • Separated from Streptococcus in 1984 based on DNA hybridization studies
  • Alpha or gamma hemolytic
  • Morphologically identical to Streptococcus sp.
  • Biochemical differences:
  • -Salt tolerant - grows on media with 6.5% NaCl
  • -Hydrolyze esculin in presence of 40% bile salts
  • > 41 species (two of which are medically important
  • Commensals of GI, skin, oral, and nasal cavities
  • E. faecalis - more likely to produce a biofilm
  • E. faecium - generally more resistant with poor prognosis
  • Nosocomial infections (bed rails, door, knobs, stethoscopes, monitoring devices, hands, gloves)
  • Clinical presentations
  • -UTIs, wound infections, pancreatitis, mastitis, etc.
30
Q

Enterococcus antimicrobial resistance

A
  • Intrinsic
  • -Low affinity PBPs, therefore penicillins are bacteriostatic (not -cidal)
  • -R to aminoglycosides due to exogenously produced folate
  • Acquired
  • -Macrolides
  • -Vancomycin - 30% of human infections are VRE (few cases in vet med)
31
Q

Diagnosis of strep infections

A
  • In clinic: Gram stain
  • -Chains of gram-positive cocci
  • Submit proper specimen for aerobic culture
  • -Remember streptococci are often commensals
  • PCR available for S. equi ssp. equi M protein
32
Q

Treatment

A
  • Local treatment: abscesses, wounds, joints
  • Systemic treatments:
  • -Beta-hemolytic streps:
  • –Sensitive (predictably susceptible)
  • —Penicillins
  • —Cephalosporins
  • –Resistant
  • —Aminoglycosides
  • —Fluoroguinolones
  • —Tetracycline
  • -Enterococcus spp.
  • –Ampicillin or clavamox
  • –If serious infection, call the lab:
  • —Bone or sepsis

Bacteriology and Mycology (6 decks)

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