Streptococcus

Question 1

Most Streptococcus are _______

Answer 1

Normal flora

• potentially pathogenic
• all have a preferred host and site
• indifferent facultative aerobes/anaerobes that have lactic acid fermentation

Question 2

Gram _____, and catalase _____

Answer 2

Positive; negative

- spherical cocci in pairs or chains

Question 3

Most require ____ or _____ for growth

Answer 3

Blood; serum

- no growth when shed into environment (unlike staph)

Question 4

What are the 6 groups of strep?

Answer 4

• pyogenic: most virulent, produce complete hemolysis
• oral or viridans: rare in animals
• lactic: associated with milk, cause mastitis
• enteric cocci: some are pathogenic, others are normal flora
• anaerobic: reclassified as peptococcus and peptostreptococcus

Question 5

Strep is also classified based on the type of ______

Answer 5

Hemolysis

• beta: clear, complete, various enzymes
• alpha: incomplete hemolysis, greenish due to H2O2
• gamma: none

Question 6

Strep is classified by ________ serological groups

Answer 6

Lancefield’s

• cell wall antigens, serological agglutination
• antigenic specificity resides in polysaccharides attached to teichoic acid layer of cell wall (C substance, for carb)
• group A-V
• could be subdivided based on cell wall proteins (M proteins)

Question 7

Capsules

Answer 7

Hyaluronic acid is non-immunogenic and non-antigenic

- act as adhesin and are antiphagocytic

Question 8

_____, ______, and _____ cause adherence and are antiphagocytic

Answer 8

M proteins, lipoteichoic acid, other cell wall proteins with fimbriae

Question 9

Toxins and enzymes

Answer 9

• streptolysin and soluble proteins are hemolysin and cytotoxins
• hyaluronidase: constituent of interstitial barrier
• streptodornase: DNAse
• streptokinase: fibrinolysin
• superantigens

Question 10

S. pyogenes

Answer 10

Only group A species, complete hemolysis and pyogenic

• mostly human pathogen
• disease in primates and lab animals
• pharyngitis, impetigo, skin infections
• superantigens: erysipelas, scarlet fever, rheumatic fever

Question 11

S. pyogenes has over 60 different _____

Answer 11

M protein (main virulence factor)
- immunity is type specific = no vaccine

Question 12

S. agalactiae

Answer 12

Only group B species, complete narrow zone, incomplete or non-hemolytic

• neonatal septicemias/meningitis
• group B strep test in late pregnancy

Question 13

What test is used to differentiate S. agalactiae?

Answer 13

CAMP

• christie, atkins, and munch-peterson factor
• diffusible, heat-stable protein
• causes complete lysis of cow or sheep RBC in the presence of S. aureus beta hemolysin producing arrowhead appearance of enhanced hemolysis

Question 14

S. agalactiae is an obligatory _____

Answer 14

Intramammary pathogen (host adapted)

• lives in milk duct, common cause of contagious bovine mastitis
• could not survive outside of host, easily spread by milking equipment or suckling calves

Question 15

S. agalactiae disease

Answer 15

Chronic, subclinical mastitis, resulting involution of alveoli and fibrosis, indurated masses
- cause of economic loss

Question 16

Treatment of S. agalactiae

Answer 16

Penicillin sensitive

- resistant to tetracycline and increasing resistance to erythromycin

Question 17

S. dysgalactiae

Answer 17

Wide alpha hemolysis

• normal flora in mouth, vagina, and skin other than udder
• survive well in environment, cannot be eliminated totally
• acute, severe mastitis or chronic, mild mastitis
• polyarthritis (joint-ill) and septicemia in lambs and calves

Question 18

What are the 2 most common causes of mastitis?

Answer 18

S. aureus and S. epidermidis

Question 19

S. zooepidemicus subsp. zooepidemicus

Answer 19

Complete hemolysis, common in many animals

• most common normal flora of skin and upper respiratory tract of horse
• 15 serotypes, no host correlations, causes sporadic infections
• wound infections, respiratory infections (pneumonia, strangles), omphalophlebitis, pyospeticemia, polyarthritis, endometritis, abortion

Question 20

S. zooepidemicus in cattle, goats, and lambs

Answer 20

Mastitis, endometritis, septicemia, arthritis, pneumonia

Question 21

Septicemia in poultry, rabbits, and swine

Answer 21

Cervical lymphadenitis in guinea pig

Question 22

S. zooepidemicus subsp. equi

Answer 22

Wide complete hemolysis, etiological agent of strangles, a regional or generalized suppurative lymphadenitis

• host adaptive, obligatory parasite, rarely isolated from non-equines
• must be differentiated from S. zooepidermicus subsp. zooepidermicus
• virulence factors: M protein and capsule
• resists phaogcytosis
• severe purulent infections and abscessation

Question 23

How do you differentiate S. zooepidermicus from S. equi?

Answer 23

• morphology: large mucoid colonies may run together, wide zone of clear hemolysis
• biochemically: S. equi does not ferment lactose or sorbitol
• S. zooepidemicus has very small colonies on blood agar, while S. equi has moist, muccoid colonies

Question 24

Strep transmission

Answer 24

Infected shedders and carriers

• may survive outside of host
• aerosol transmission

Question 25

Strep exposure

Answer 25

• inhalation, ingestion, contact, insects
• fall/spring
• yearlings or older but no prior exposure
• groups of horses

Question 26

Strep invasion

Answer 26

Colonization and invasion of nasopharyngeal mucosa

• incubation: 3-6 days, anorexia with high fever
• pharyngitis
• invasion of regional lymph nodes
• development of abscesses that rupture and drain at 10-30 days = disappearance of fever and signs

Question 27

Sequelae

Answer 27

• asphyxiation
• bastard strangles: septicemia and dissemination to any tissue, joint, skin, viscera
• gutteral pouch emphyema
• purpura hemorrhagica

Question 28

Strep immunity

Answer 28

Mainly humoral!!

• recovered animals may be immune for life
• there are vaccines available

Question 29

Strep diagnosis

Answer 29

Clinical: highly contagious (quarantine), morbidity is 40-80%, mortality is 5-10%
Culture: use lymph node aspirate and nasal swabs, differentiate from S. zooepidemicus

Question 30

Strep treatment

Answer 30

Drain abscess, antimicrobial therapy is controversial

- administration of procaine penicillin will stop abscess formation

Question 31

S. procinus

Answer 31

Complete hemolysis, pyogenic

• cervical lymphadenitis in swine = jowl abscesses (swine strangles)
• oral, avirulent live vaccine

Question 32

S. canis

Answer 32

Wide complete hemolysis, pyogenic

• normal flora of mouth, upper respiratory, intestine, genitalia in dogs/cats
• metritis, vaginitis, pyometra, neonatal septicemia, conjunctivitis, cystitis, otitis externa

Question 33

S. pneumoniae

Answer 33

Incomplete hemolysis

• primates and humans only
• no specific “C” substance or “M” protein
• > 90 polysaccharide capsule types: Quellung reaction used for serotyping
• most common cause of human bacterial pneumonia
• penicillin sensitive
• subunit vaccine available

Question 34

S. iniae

Answer 34

Incomplete and complete hemolysis

• thoracic and abdominal subq abscesses of dolphins
• occurs in many species of fish as a systemic disease

Question 35

Viridans streptococci

Answer 35

All incompletely hemolytic strep that are not pyogenic

• normal flora in mouth and pharynx
• opportunistic pathogens in humans
• S. mutans: plaque and dental caries in humans
• no significant disease in animals