Streptococcus and Enterococcus

Question 1

Streptococcus spp.

Answer 1

• 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

Question 2

Catalase test

Answer 2

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

Question 3

Streptococcus didelphis

Answer 3

• Dermal septic necrosis in opossums

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

Question 4

Hemolysis on blood agar

Answer 4

• 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

Question 5

Virulence factors

Answer 5

=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)

Question 6

Transmission

Answer 6

• Inhalation
• Ingestion
• Sexual contact
• Congenital
• Via hands/fomites

Question 7

Typical presentation

Answer 7

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

Question 8

Lancefield grouping

Answer 8

• 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)

Question 9

Group A streps

Answer 9

• 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)

Question 10

S. pyogenes

Answer 10

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

Question 11

S. pneumoniae

Answer 11

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

Question 12

Group B streps

Answer 12

-S. agalactiae (bovine contagious mastitis)

Question 13

S. agalactiae

Answer 13

• 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

Question 14

Bovine mastitis streptococci

Answer 14

• 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)

Question 15

ADDL bulk tank culture report

Answer 15

• Contagious
• -Streptococcus agalactiae
• -Staphylococcus aureau
• -Mycoplasma spp.

Question 16

Group C streps

Answer 16

• S. dysgalactiae ssp. dysgalactiae
• S. dysgalactiae ssp. equisimilis
• S. equi ssp. equi
• S. equi ssp. zooepidemicus

Question 17

S. dysgalactiae ssp. dysgalactiae

Answer 17

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

Question 18

S. dysgalactiae ssp. equisimilis

Answer 18

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

Question 19

S. equi ssp. equi

Answer 19

• Strangles
• Genital infections
• Mastitis
• Other suppurative conditions

Question 20

Equine strangles

Answer 20

• 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

Question 21

Purpura hemorrhagica

Answer 21

• 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

Question 22

S. equi ssp. zooepidemicus

Answer 22

• 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

Question 23

Group D streps

Answer 23

• S. gallolyticus ssp. gallolyticus
• S. suis
• Enterococcus spp.

Question 24

S. gallolyticus ssp. gallolyticus

Answer 24

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

Question 25

S. suis

Answer 25

• 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

Question 26

S. porcinus

Answer 26

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

Question 27

S. canis

Answer 27

• 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

Question 28

Necrotizing fasciitis

Answer 28

• 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)

Question 29

Enterococcus spp.

Answer 29

• 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.

Question 30

Enterococcus antimicrobial resistance

Answer 30

• 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)

Question 31

Diagnosis of strep infections

Answer 31

• 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

Question 32

Treatment

Answer 32

• 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