Staphylococcus Flashcards
All cocci are gram +ve Except
VeNoM
Veilonella
Neisseria
Moraxella
Classification of Gram +ve Cocci
Micrococcacae - Staphylococcus, Micrococcus
Streptococcacae - Streptococcus, Pneumococcus, Enterococcus
Shape of Staphylococcus and Micrococcus
Bunch of grapes - S Aureus
Tetrad - Micrococcus
Glucose utilisation in Micrococcus and Staphylococcus
Oxidative - Micrococcus
Fermentative - S Aureus
Micrococcus and Staphylococcus are Catalase
Positive
Micrococcus and Staphylococcus are Oxidase
Micrococcus - Positive
Staphylococcus - Negative
Staphylococcus is Bacitracin
Resistant (Tough)
Micrococcus is Bacitracin
Sensitive
What is glucose utilisation medium
Hugh and Leifson (Bromothymol blue indicator)
S. Aureus produces which pigment
Golden pigment
Features of Staphylococcus aureus
Non motile
Non sporing
Catalase +ve
Oxidase -ve
Virulence factors of S Aureus associated with cell wall
Peptidoglycan, Teichoic acid
Virulence factor of S Aureus associated with cell surface
Protein A , Clumping factor
Features of Protein A
Anti-complementary
Anti-phagocytosis
Co-agglutination
In case of S Aureus , for co-agglutination test which strain is used
COWAN-1 Strain
Toxins produced By Staph aureus
Hemolysins
Panton-valentin toxin (PV Toxin)
Epidermolytic/Exfoliative toxin
Enterotoxin
Types of Hemolysin toxin
Alpha - Lyse sheep and human RBC, inactivated at 70° and activated at 100°
Beta/Sphingomyelinase - Lyse sheepn RBC only, Hot cold phenomenom
Gamma - Lyse sheep and human RBC
Delta - Same
Panton-valentin toxin is secreted by
Methicillin resistant Staph Aureus
Epidermolytic or Exfoliative toxin can cause
Staphylococcus scalded skin syndrome (SSSS)
Ritter’s disease
TEN(Toxic epidermal necrolysis)
Site of action of Epidermolytic toxin in Staphylococcus scalded skin syndrome
Stratum granulosum - Desmoglein 1
Most common Type of Enterotoxin
Enterotoxin A
Heat stable
Enterotoxin can cause
Food poisioning - Vagomimetic action - Vomiting
Incubation period for Food poisoning caused by Enterotoxin
1-6 hours
Enterotoxin F can cause
Toxic shock Syndrome
Toxic shock Syndrome is associated with
Long term tampon usage
Fatal
Criteria of Toxic Shock Syndrome
Fever >102°F
Hypotension - SBP <90
Maculopapular rash + Any 3 or more organs involvement
Enzymes associated with Staphylococcus
Thermonuclease
DNAase
Phosphatase
Catalase
Coagulase
Clinical Features seen in Staphylococcus
SOFT PAINS
S - Skin and Soft tissue infections
O - Osteomyelitis
F - Food poisioning (<6hrs)
T - Toxic Shock Syndrome, Toxic epidermal Necrolysis
P - pneumoniae, Pneumocele
A - Acute infective endocarditis
I - infective Arthritis
N - Necrotizing Fascilitis
S - Sepsis
Botryomycosis is caused by
Staph aureus
Most common cause of Native valve infective endocarditis
S. Aureus
Most common cause of Hospital acquired pneumonia or VAP
S. Aureus
Microscopic Finding of S Aureus
Bunch of grapes
Culture used for S. Aureus
Nutrient Agar - Golden pigment (Staphyloxanthin @22°C, Non diffusible)
Blood Agar - Pin head colonies, Narrow zone Hemolysis
Selective media for staph aureus
S. Aureus - Salt(7-10%)
Mannitol Salt agar
Ludlam’s agar
Salt milk agar
How we will get to know about Catalase positive or negative
Catalase positive organisms - Bubbles on slide
Examples of Catalase positive organisms
Cats Space Being Made
S- S. Aureus, Serratia (Red)
P- Pseudomonas
A - Aspergillus
C - Candida, Cryptococcus
E - Ecoli, Enterobacteriacea
BeiNG - Bacillus anthracis, Neisseria gonorrhea and meningitidis
MADE - MTB and Micrococcus
Types of Coagulase test
Slide Coagulase
Tube Coagulase
Slide Coagulase is also known as
Bound Coagulase
Tube Coagulase is also known as
Free Coagulase
Slide Coagulase is positive in
Staph aureus
Staph intermedius
Staph Hyicus
Staph Lugdunensis
Tube Coagulase is positive in
Staph aureus
Staph intermedius
Staph Hyicus
Staph Schleiferi
Tube Coagulase/Free Coagulase test Procedure
Rabbit/Human Plasma (Coagulase reacting factor) added in culture broth - CRF -coagulase complex - activates Fibrinogen - leads to clotting of plasma
Typing done in Staph aureus
Phage Typing - Phage 80/81A
Phage 3 - MRSA
Gonotypic Typing - Pulsefield Gel electrophoresis
Treatment of Staphylococcus infection
Penicillin (Beta lactams)
Methicillin
Vancomycin
Resistance develops against beta lactams due to
By Beta lactamase production (BLA gene and transferred by Plasmid)
Most common method of beta lactam resistance
Transduction > Conjugation
In case of Penicillin resistance, which drug can be used
Methicillin
Methicillin resistance develops due to which gene
Mec A gene (Chromosomally mediated)
Diagnosis of MRSA is done by
Dilution broth (Best)
If MIC Cefoxitin >8microgm/L or
MIC Oxacillin >4mircrogm/L
Other methods - Cefoxitin/Oxacillin disc Diffusion agar
Latex agglutination for PBP2a
ELISA or PCE for MecA gene
Most common method of MRSA Spread
Hands of healthcare workers
How to eliminate MRSA infection
Nasal Carriers - Ointment Muprocin
Other - Chlorhexidine washes
Precaution - Hand washing
Which drug can be used in case of MRSA
Vancomycin
Daptomycin
Vancomycin resistant Staph aureus is associated with conversion of
Conversion of D-ala-D-ala to D-ala-D-lactate/serine
Which gene is involved in development of VRSA
VAN-A gene
Diagnosis of VISA(Vancomycin intermedius S. Aureus) and VRSA
VISA - MIC - 4-8microgm/L
VRSA - MIC - >16microgm/L
Examples of Coagulase Negative staphylococcus
Staphylococcus epidermidis
Staphylococcus saprophyticus
Which is most common Coagulase Negative staphylococcus
Staphylococcus epidermidis
Staphylococcus epidermidis is mostly associated with which infection
Prosthetic valve endocarditis
Staphylococcus saprophyticus is associated with which infection
UTI
Biofilm can be shown by which Coagulase Negative staphylococcus
Staphylococcus epidermidis
Biofilm protects bacteria against antibiotics
Which Coagulase Negative staphylococcus is Novobiocin resistant or sensitive
S epidermidis - Sensitive
S saprophyticus - Resistant
