Staphylococcus Aureus

By: Jamie Naumann

Colony Characteristics

Family – Staphylococcaceae Gram Positive Non-motile Cocci (round appearance under

microscope) Usually found in grape-like clusters Catalase positive

Continued..

Primarily coagulase positive › Some strains may be atypical in that they do

not produce coagulase Glistening, opaque, yellow to white

appearance on blood agar Patterns of B or A hemolysis may be

visible Fairly large colonies Rancid odor to colonies

Further identification is available using commercial test kits

Can be identified by phage typing or by 16S ribosomal DNA typing

Reproduce asexually

Dangers of S. Aureus

It is dangerous in animals not only for potential effect on the animals health, but the ease for which infections and diseases can be transmitted to humans!

Humans can also infect animals All mammals are vulnerable to

infection

Transmission

Aerosol Direct contant

› Fomites› Infected animals› Infected people

In a laboratory rodent setting, it is more likely for humans to infect animals!

Colonization In healthy, immunocompentent

animals S. aureus colonization of the skin, intestinal tract, or nasopharyx is generally asymptomatic

May be colonized from an abscess/lesion, but is usually a secondary infection

S. aureus is a classic opportunist, taking advantage of broken skin or other entry sites to cause an infection!

Examples of Clinical Signs/Diseases..

Dogs› Pyaemia dermatitis (condtion of abscesses

and contamination of the blood) Horses

› Botryomycosis (Bacterial infection of the skin or organs)

Poultry› Septicaemia and arthritis

Cases have also been reported in cats, pigs, beef cattle and numerous other animals

Dairy cattle› S. aureus is considered highly dangerous

and a major cause of mastitis › Hard to treat› An estimated half of S. Aureus strains have

the ability to be resistant to antibiotics! Humans

› Can destroy tissue› S. aureus gastroenteritis (self-limiting with

the person recovering in 8–24 hours) Symptoms = nausea, vomiting, diarrhea,

and abdominal pain

Generally skin infections are the most common diseased produced› Localized collection of pus (abscess, boil) › Cellulitis (infection of tissue leading to

swelling)› Crusting of skin› If infection spreads to the blood; fever,

chills, and low blood pressure are present Can cause severe infections!

Pictures of infection in humans..

Methicillin-Resistant Staphyloccus Aureus

(MRSA) By changing its chemical makeup slightly

to evade attack, S. aureus has become resitant to many commonly used antibiotics› In 1997, physicians were alarmed to encounter

staph strains that resist even vancomycin, which used to work when all else failed!

The infection is most dangerous when it’s related to a surgical wound, and otherwise healthy animals can easily lose a limb or worse

World wide problem and is responsible for increasing number of deaths due to its ability to resist most forms of antibiotic treatment!

It is very serious and immediate medical attention is needed when S. aureus is found in any laboratory, food source or companion animal!

Each year some 500,000 patients in American hospitals contract a staphylococcal infection!

Although S. aureus is hard to treat in patients, most chemical cleaners found in a veterinary or human hospital can kill it on surfaces and/or fomites

Infections can be prevented with proper sanitary techniques, such as wearing gloves.

Sources

www.doctorslounge.com/infections/microbiology/bacteria/staphylococcus.htm

http://www.ehow.com/how-does_5615904_veterinary-diseases-caused-staphylococcus-aureus.html

http://www.criver.com/SiteCollectionDocuments/rm_ld_r_staphylococcus_aureus.pdf