Streptococcus and Enterococcus Flashcards
(32 cards)
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
2
Q
Catalase test
A
- Generally catalase negative
- Exceptions:
- -Streptococcus didelphis
- Catalase is an enzyme that breaks down hydrogen peroxide into water and oxygen
3
Q
Streptococcus didelphis
A
- Dermal septic necrosis in opossums
- Affects tip of tail, toes, eyes, ears, etc.
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
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)
6
Q
Transmission
A
- Inhalation
- Ingestion
- Sexual contact
- Congenital
- Via hands/fomites
7
Q
Typical presentation
A
- Pyogenic infection
- -Abscess
- -Sequelae:
- –Immune mediated lesions
- –Toxemia
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)
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)
10
Q
S. pyogenes
A
- Bovine mastitis (rare)
- Lymphangitis in foals
- Can cause disease in other species
11
Q
S. pneumoniae
A
-Reports of pneumonia in guinea pigs, rats, horses, non-human primates (+/- meningitis)
12
Q
Group B streps
A
-S. agalactiae (bovine contagious mastitis)
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
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)
15
Q
ADDL bulk tank culture report
A
- Contagious
- -Streptococcus agalactiae
- -Staphylococcus aureau
- -Mycoplasma spp.
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
S. suis
- 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
S. porcinus
- Cervical lymphadenitis
- Jowl, head, neck abscesses
- Carcass may be condemned at slaughter
27
S. canis
- 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
Necrotizing fasciitis
- 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
Enterococcus spp.
- 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
Enterococcus antimicrobial resistance
- 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
Diagnosis of strep infections
- 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
Treatment
- 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
