LESSN 2a: Staphylococcus species

Question 1

General description

Answer 1

• Gram-positive cocci (approx. 1µm diameter)
  resembling grapes
  -Grow on non-enriched media
  -facultative anaerobes, oxidase-negative, and
  catalase-positive
  -non-motile and and non spore forming
• causing pyogenic infections
  -some are coagulase positive which correlates with pathogenecity
• comparatively stable in environment

Question 2

usual habitat of staphylococcus :

Answer 2

commensals on skin and mucous membrane

Question 2

Colonial characteristics:

Answer 2

: colonies are usually white, opaque and up to 4 mm in diameter.

Question 2

Colonies
produce double haemolysis

Answer 2

of S. aureus and S. pseudintermedius

Question 3

The colonies of bovine and human strains of S. aureus are

Answer 3

golden yellow

Question 3

Colonies of some coagulase-negative staphylococci are also
pigmented

Question 4

Haemolysis in sheep or ox blood agar: Four staphylococcal haemolysins s are
recognized

Answer 4

Alpha, beta, gamma and delta

Question 5

Staphylococcal cell wall proteins, which bind to
facilitate bacterial attachment to tissues

Answer 5

fibronectin and fibrinogen,

Question 5

Pyogenic characteristics causes

Answer 5

suppurative lesions

Question 6

Structural features including including

Answer 6

-capsular polysaccharide
-teichoic acids and
protein A interfere with opsonization and subsequent phagocytosis

Question 7

Exoenzymes such as kinases and hyaluronidase promote tissue invasion, and
exotoxins including haemolysins and leukocidin lyse host cell membranes

Question 7

Pathogenic effects can range from relatively minor local infections to lifethreatening septicaemia

Question 7

(dx)

Question 7

Sample source: lesions (skin scrapings, swab samples);
exudates; mastitic milk sample

Question 8

Demonstration of bacteria:

Answer 8

Gram-staining, or culture on blood agar, selective blood agar, MacConkey agar

Question 9

Identification criteria:

Answer 9

–Colonial characteristics
– Presence or absence of haemolysis
– Absence of growth on MacConkey agar
– Catalase production
– Coagulase production
– Biochemical profile

Question 10

CLINICAL INFECTIONS

Question 11

can be either endogenous or exogenous in origin

Question 12

many are opportunistic and associated with - –trauma,
-immunosuppression,
-intercurrent parasitic or fungal infections,
-allergic conditions or endocrine and
-metabolic disturbance

Question 13

S. aureaus (lambs); Lambs can carry S. aureus on their skin and nasal mucosa and infection occurs through minor skin trauma including tick bites

Answer 13

Tick pyaemia

Question 13

S. aureus, most often causes subclinical
infections; virulence factor is alpha toxin that results to tissue necrosis and can
be life threatening

Answer 13

Bovine staphylococcal mastitis:

Question 13

Staphylococcal diseases of importance in domestic animals include

Answer 13

mastitis,
tick pyaemia,
exudative epidermitis,
botryomycosis and pyoderm

Question 13

is a vector for the rickettsial agent of tick-borne fever

Answer 13

Ixodes ricinus

Question 13

which can cause immunosuppression in lambs and maypredispose to staphylococcal infection;
characterized either by septicaemia and
rapid death or by localized abscess formation

Answer 13

Anaplasma phagocytophilum

Question 14

dx- bacterial confirmations;

Question 14

S. hyicus; occurs worldwide in sucklers and weaned pigs up to 3 months of age

Answer 14

Exudative epidermitis (greasy pig disease)

Question 14

Treatment (tx) - tetracyclines and tick control

Question 14

can be isolated from the vaginal mucosa and skin of healthy sows.

Answer 14

Staphylococcus hyicus

Question 15

produced by S. hyicus appears to be the major virulence factor as injection of this toxin into the skin of young pigs produces exfoliation

Answer 15

Exfoliative toxin

Question 15

a chronic, suppurative granulomatous condition, which usually occur within a few weeks of castration in the horse due to infection of the stump of the spermatic cord (scirrhous cord); can also occur in mammary tissues

Answer 15

Botryomycosis : S. aureus in horses

Question 15

dogs with wound infections, surgical site infections, pyoderma, otitis and urinary tract infections are most commonly reported; common cause of nosocomial infection in vet hospitals

Answer 15

Methicillin-resistant staphylococcal infections in animals: