Coagulase – Ve Staphylococci

COAGULASE – ve STAPHYLOCOCCI

Q. 1

Which of the following disorders would more likely be associated with Staphylococcus saprophyticus rather than Staphylococcus aureus?

 A

Osteomyelitis       

 B

Tension pneumothorax

 C

Burns    

 D

Acute cystitis

Q. 1

Which of the following disorders would more likely be associated with Staphylococcus saprophyticus rather than Staphylococcus aureus?

 A

Osteomyelitis       

 B

Tension pneumothorax

 C

Burns    

 D

Acute cystitis

Ans. D

Explanation:

Ans:D.)Acute Cystitis.

Staphylococcus Aureus.

  • Skin infections are the most common form of S. aureus infection. This can manifest in various ways, including small benign boils, folliculitis, impetigo, cellulitis, and more severe, invasive soft-tissue infections.
  • Also responsible for food poisoning.
  • Most common bacteria associated with conjunctivitis
  • Can cause Toxic shock syndrome.
  • S. aureus is the bacterium that is commonly responsible for all major bone and joint infections. This manifests in one of three forms: osteomyelitis, septic arthritis and infection from a replacement joint surgery.
  • Most common pathogen isolated in sputum of children with cystic fibrosis during the first decade.
  • One of the most common causes of bacteremia and infective endocarditis.Prosthetic valve endocarditis is most commonly caused by Staphylococcus aureus.
  • Important pathogen causing pneumonia in a patient with bronchiectasis.

Coagulase negative Staphylococci
Staph epidermidis – MC pathogen infecting IV catheters, shunts, prosthetic valves, grafts, CSF shunts, dialyzer. Can form glycocalyx or slime layer, that protects bacteria from antibiotics
S. saphrophyticus – UTI in sexually active young women.


Q. 2

Which one of the following gram positive organism is most common cause of UTI among sexually active women-

 A

Staphylococcus epidermidis

 B

Staphylococcus aureus

 C

Staphylococcus saprophyticus

 D

Enterococcus

Q. 2

Which one of the following gram positive organism is most common cause of UTI among sexually active women-

 A

Staphylococcus epidermidis

 B

Staphylococcus aureus

 C

Staphylococcus saprophyticus

 D

Enterococcus

Ans. C

Explanation:

Ans. is ‘c’ i.e., Staphylococcus saprophyticus

Staph saprophyticus

Staph saprophyticus may be present on normal human skin and the periurethral area and can cause urinary tract infection, particularly in sexually active young women.

.  Staph saprophyticus strains causing UTI are usually sensitive to most antibiotics, except nalidixic acid.

.  Staph saprophyticus is novobiocin resistant.


Q. 3

A patient with a prosthetic heart valve develops endocarditis eight months after valve replacement. Most likely organism responsible is:

 A

Staphylococcus Aureus

 B

Staphylococcus Epidermidis

 C

Streptococcus Viridans

 D

HACEK group

Q. 3

A patient with a prosthetic heart valve develops endocarditis eight months after valve replacement. Most likely organism responsible is:

 A

Staphylococcus Aureus

 B

Staphylococcus Epidermidis

 C

Streptococcus Viridans

 D

HACEK group

Ans. B

Explanation:

Answer is B (Staphylococcus Epidermidis)

The most common causative organisms of infective endocarditic within the first 12 months after valve surgery are Coagulase Negative Staphylococci. Staphylococcus Epidermidis is a coagulase negative staphylococcus and the single best answer of choice.

Organism

Prothetic Valve endocarditis (% of cases) Time of onset after valve surgery

 

< 2 months

2-12 months

> 12 months

Coagulase Negative Staphylococcus

33

32

1   I

Staphylococcus Aureus

22

12

18

Enterococcii

08

12

11

Streptococcii (Viridans)

01

09

31

Gram Negative Bacilli

05

06

08

Gram Negative Coccohacilii (HACEK)

06

 Paravalvular abscesses in patients with acute infective endocarditis is especially seen in association with virulent organisms like staphylococci and enterococcii. Such abscesses may also be seen in association with some virulent strains of streptococcal endocarditis. Staphylococcus however are the most common organisms associated with such abscesses.


Q. 4

Most common cause of artificial heart valve infection‑

 A

Staphylococcus aureus

 B

Streptococcus mutans

 C

Staph epidermidis

 D

Pneumococcus

Q. 4

Most common cause of artificial heart valve infection‑

 A

Staphylococcus aureus

 B

Streptococcus mutans

 C

Staph epidermidis

 D

Pneumococcus

Ans. C

Explanation:

Ans. is ‘c’ i.e., Staph epidermidis

Most common cause of prosthetic valve endocarditis upto 12 months is coagulase – negative staphylococci (staph. epidermidis).

Most common causes of infective endocarditis

  • In native wall → Staphylococcus aureus.
  • In early prosthetic valve (up to 12 months after valve surgery) → Staphylococcus epidermidis (coagulase negative staphylococcus).
  • In late prosthetic valve (more than 12 months after valve surgery) → streptococcus viridans.
  • In IV drug abusers → Staphylococcus aureus.
  • In patients with intravenous catheter → coagulase negative staphylococci.
  • After dental procedure (tooth extraction) → streptococcus mutans.


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