Staphylococcal Flashcards
Gram positive Cocci
Staphylococci
Streptococci
Enterococci
Staphylococcai
arranged in
grape like clusters, non capsulated, non motile
and non spore forming..
Staph. aureus couaglase test
Positive
Staph. epidermids and Staph. saprophyticus couaglase test
Negative
Staphylococcai catalase test
Positive
Sterptococcai catalase test ?
Negative
Enterococcai catalase test
Negative
Culture of staphylococcai
Facultative anaerobes
Grows on nutrient media : yellow golden colines
blood agar: Produce complete hemolysis
fermintat mannitol :yellow golden color
DNAase test for staph aureus
Positive
Staph. aureus can produce disease through
both
invasion by its cell components (antigenic structure), and by the production of extracellular enzymes and toxins.
What kind of antigenic structure have endotoxin like activity and produce septic shock?
Peptidoglycan
What part of antigenic structure function in antiphagocytic and anticomplement
Protein A
cause Staphylococci to become more
resistant to phagocytosis.
Coagulase
Most infections caused by Staph. aureus are
localized due to
coagulase production.
limits the accessibility of antibiotics to the
infection site
Coagulase
yielding
aggregation of the bacteria and promoting
their attachment to blood clots.
Clumping factor
Causes shock in: - tampon-using menstruating women - individuals with wound infections - patients with nasal packing used to stop bleeding from
the nose. The toxin is produced locally in the vagina, nose, or other
infected site, then enters the bloodstream, causing
toxemia.
Toxic shock syndrome toxin
In which type of toxin Blood cultures typically do not grow Staph. aureus.
Toxic shock syndrome toxin
causes food poisoning with prominent
vomiting (caused by cytokines which stimulate
the enteric nervous system to activate the
vomiting center in the brain) and watery
diarrhea.
• is heat-resistant and not
inactivated by brief cooking.
• It is resistant to stomach acid and enzymes.
Enterotoxin
Toxin seen in staphylococcal scalded skin
syndrome (peeling of the skin).
Exfoliative toxins
toxins that kill leucocytes and
cause necrosis of tissues.
Leukocidins
produced by recently isolated
community- associated CA-MRSA and is
associated with severe necrotizing pneumonia in
children.
Panton- Valentin leukocidin (PVL)(Pore-forming
toxin)
superantigens
1- Toxic shock syndrome toxin (TSST – 1)
2- Enterotoxins
3-Exfoliative toxins
Pyogenic diseases
Superficial examples of staph aureus
carbuncle, boils, impetigo,stye. wound infection and abscess formation.
most comon organism that causes pneumonia
Staph aureus
main cause of acute endocarditis in interavenous drug users(IVDUs) with high mortality rate.
Staph aureus
common organisms that
are involved in HAIs e.g. surgical site infections and pneumonia
Staph aureus
Bacteremia
Organisim found in blood
Septicemia
Organisms + toxin
Toxinemia
Only toxin in blood
Staph aureus
is manifested by an abrupt
onset of high fever, vomiting, diarrhea, myalgias, macular & sun burn-like rash that goes on to desquamate, and hypotension with cardiac and renal failure in the most severe cases.
leading to
widespread capillary leakage characterized by **fever **desquamative skin rash **hypotension ending in **shock with multisystem organ failures
Toxic shock syndrome
Staph aureus
superficial layers of the epidermis slough in
response to the presence of exfoliative toxin.
Scalded skin syndrome
Laboratory diagnosis of Staphylococcus aureus
infections:
Specimen
Direct gram stained smear
Culture
Biochemical reaction
Phage typing
To determine the source of infection in :
• Epidemiological tracing of outbreaks in hospitals.
Samples from wounds, nose and nail bed of doctors,
nurses and from fomites are tested. • Outbreaks of food poisoning, the organism isolated from
food, vomitus, stool, and from nose and nail bed of food
handlers.
Phage typing
The drug of choice for these Staphylococci aureus who are “methicillin”-
resistant (MRSA).
Vancomycin
causes urinary tract
infections, particularly in sexually active young
women.
Staph. saprophyticus:
Number one organism causing community-acquired urinary tract
infections in young women ?
1E.coli
2 Staph. saprophyticus:
A major cause of sepsis in neonates
Staph. epidermidis
can enter the bloodstream (bacteremia) and
organ abcesses infections, especially at the site of
IV catheters, prosthetic implants
Staph. epidermidis
Staph. epidermidis
Are found especially at site of iv cathaters and prosthetic implants (prosthetic heart
valves, vascular grafts, and prosthetic joints) due
to the production of
glycocalyx (SLIME OR BIOFILM).
Coagulase –ve and non hemolytic on blood agar
S.epidermidis
S.saprophyticus
Novobiocin sensitivity test of staph epidermis result
Sensitive
Novobiocin sensitivity test of staph sarpophyticus result
Resistance
Mannitol fermentation and DNAase test for Coagulase negative Staphylococci:
Staph epidermis and staph sarpophyticus
Negative
How are Staphylococci clinically classified?
They are classified according to:
a)Exotoxin production
b)Exopigment production
c)Coagulase production
d)Catalase production
Coagulase production
If the bacterial pathogen with this morphology is coagulase positive, what surface protein binds the Fc portion of IgG, thereby preventing effective opsonization?
Protein A
A 20-year-old woman with a history of IV drug use presents at the emergency department with rapid onset lethargy, fever, and a heart murmur. Blood cultures were collected for analysis, and golden colonies grew from blood specimens. The Gram stain of the cells from the colonies resembled that shown. What is the most likely etiology and infection?
acute endocarditis caused by Staphylococcus aureus .
You’re in the clinical laboratory looking at a Gram stain when the laboratory technician comes up to you and says, “I think your patient has Staph epi [short for Staphylococcus epidermidis] bac-teremia.” Which one of the following sets of results did the tech find with the organism recovered from the blood culture?
(A) Gram-positive cocci in chains, catalase-positive, coagulase-positive
(B) Gram-positive
COCCi in chains, catalase-negative,
coagulase-negative
© Gram-positive cocci in clusters, catalase-positive,
coagulase-negative
(D) Gram-positive cocci in clusters, catalase-negative, coagulase-positive
(E) Gram-positive diplococci, catalase-negative, coagulase-positive
© Gram-positive cocci in clusters, catalase-positive,
coagulase-negative
Superantigen production by Staphylococcus aureus is involved in the pathogenesis of which one of the following diseases?
(A) Impetigo
(B) Osteomyelitis
(C) Scalded skin syndrome
(D) Septicemia
E-Toxic shock syndrome
E-Toxic shock syndrome
Which one of the following is the virulence factor produced by Staphylococcus aureus that prevents the activation of complement and thereby reduces opsonization by C3b?
(A) Catalase
(B) Coagulase
(C) Endotoxin
(D) Protein A
(E) Teichoic acid
Protein A
The main reason why methicillin-resistant Staphylococcus aureus
(MRSA) strains are resistant to methicillin and nafcillin is:
(A) they produce B-lactamase that degrades the antibiotics.
(B) they have altered penicillin-binding proteins that have reduced binding of the antibiotics.
(C) they have mutant porin proteins that prevent the antibiotics from entering the bacteria.
(D) they have plasmid-encoded export proteins that remove the drug from the bacteria.
B) they have altered penicillin-binding proteins that have reduced binding of the antibiotics.
A pore-forming exotoxin produced by Staphylococcus aureus that kills cells and is important in the severe, rapidly spreading necrotizing lesions caused by MRSA strains is:
(A) coagulase.
(B) enterotoxin.
(C) exfoliatin.
(D P-V leukocidin.
leukocidin
Of the following antibiotics, which one is the most appropriate to treat a severe necrotizing skin infection caused by an MRSA strain of Staphylococcus aureus?
(A) Amoxicillin
(B) Ceftriaxone
(C) Ciprofloxacin
(D) Gentamicin
(E) Vancomycin
Vancomycin
The Jones family of four had a delicious picnic lunch last Sunday.
It was a warm day, and the food sat in the sun for several hours.
Alas, 3 hours later, everyone came down with vomiting and non-bloody diarrhea. In the emergency room, it was found that Mrs.
Jones, who prepared the food, had a paronychia on her thumb.
Which one of the following is the most likely causative organism?
(A) Enterococcus faecalis
(B) Staphylococcus aureus
(C) Staphylococcus epidermidis
(D) Streptococcus agalactiae
(E) Streptococcus pyogenes
B) Staphylococcus aureus
