B- Toxic Shock Syndrome
- First observed in Menstruating
females using tampons )tampon
retained in vagina for 4-5 days(
- Any staphylococcal lesion can
predispose to TSS.
Virulence factor: TSST-1
culture: for isolation & identification.
ELISA: for toxin detection in blood
C- Staph. aureus food poisoning
1- 6 hrs.
Colic, vomiting, mild
Diarrhea, but no fever
1. Specimen: food, vomitus, stools.
2. Culture: on MSA.
3. ELISA: for toxin detection in sample or in isolated
4. Strain typing: to trace source of infection )e.g. phage
Coagulase negative Staphylococci (CoNS)
• General Characters:
– Non-hemolytic on blood
– Coagulase negative
– Mannitol non-fermenter
– Device-related infections
infections, … etc…)
– Urinary tract infection
– Wound infection
UTI (honeymoon) cystitis
A man underwent an emergency operation for
perforated appendix. He required admission
to the Intensive Care Unit. On the 5th day
of hospitalization he developed fever, and
the wound was erythematous, swollen,
with purulent discharge (Surgical site
infection “SSI”). The surgeon requested
bacteriological examination (culture and
sensitivity) of the wound pus
Surgical site infection
• Wound swabs were
• Gram staining &
cocci arranged in
clusters amongst pus
On Blood agar →
On nutrient agar →
Golden yellow pigment
On MSA →
Film from colonies
Which organism is causing this
• Gram-positive cocci in clusters, catalase positive
• β-hemolysis , golden yellow pigment, yellow
colonies on MSA and coagulase positivity
Antimicrobial susceptibility “Disc
the organism is
but sensitive to:
How do you interpret the
The organism is multi-resistant, including
methicillin-resistant S. aureus (MRSA).
Name other diseases caused by
1. Pyogenic infections
a. Localized skin infections, e.g. folliculitis, furuncles,
b. Staph pneumonia
c. Invasive staph. infections, e.g. endocarditis, cellulitis,
osteomyelitis, and septic arthritis
2. Toxin-mediated diseases
, a. Toxic shock syndrome
,b. Scalded skin syndrome
c. Food poisoning.
A group of people shared a carbohydrate- rich
meal. 1-6 hours later, they manifested vomiting,
diarrhea but no fever. The condition was mild and
a) What could be the clinical diagnosis?
b) What is the possible causative organism?
c) What is the virulence factor responsible for this
d) What is the mechanism of action of such
e) What is the laboratory test that is used to trace the
source of this outbreak?
1. All the following are characteristic features
of staphylococci except:
Gram positive cocci.
Arranged in clusters.
Catalase negative .
Usually grow on simple media.
Usually inhabit skin and mucosa.
2. The following medium is used to isolate S.
aureus from specimens contaminated by
a) Nutrient agar.
b) MacConkey's agar.
c) Blood agar .
d) Mannitol salt agar.
e) Chocolate agar
3. The localized nature of S. aureus lesions is due
b) Protein A.
4. S. aureus growth can be identified by the
following characters except:
a) Colony on blood agar is golden yellow.
b) Colony on blood agar is surrounded with a clear
c) Colony on Mannitol salt agar is rose pink.
d) Protein A positive.
e) Coagulase test positive.
5. One of the following is a S. aureus toxinmediated disease:
b) Staphylococcal pneumonia.
c) Toxic shock syndrome.
6. Staphylococcal strain typing is used :
a) To diagnose staphylococcal pyogenic diseases.
b) To differentiate between coagulase -ve and
coagulase +ve staphylococci.
c) To differentiate between staphylococci &
d) To trace the source of outbreaks of S. aureus in
the epidemiological studies.
e) To identify enterotoxin-producing strains of S.