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Infection > Gram Positive Bacteria > Flashcards

Gram Positive Bacteria Flashcards

1
Q

What are the clinically important varieties of staphylococcus?

A

S.aureus, s. Epidermidis, s.saprophyticus.

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2
Q

How are staphylococci grown?

A

They grow easily under aerobic conditions on blood and other non selective agars.

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3
Q

What is the catalase status of staphylococci?

A

Catalase positive

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4
Q

What is the coagulase status of staphylococci?

A

S.aureus- coagulase positive.

Others are coagulase negative.

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5
Q

Where are staphylococci found?

A

On skin and mucosal surfaces of humans and other animals.

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6
Q

What are the virulence factors of Staphylococci?

A

Polysaccharide capsule allows them to resist phagocytosis.

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7
Q

What does catalase (found in staphylococci) do?

A

Inactivates hydrogen peroxide

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8
Q

What invasive diseases does S.aureus cause?

A 
Superficial pustules or boils
Surgical wound infections
Abcesses of deep soft tissue
Osteomyelitis
Septicaemia
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9
Q

What toxin mediated diseases does S.aureus cause?

A

Toxic shock syndrome
Scalded skin syndrome
Food poisoning

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10
Q

In what clinical situations is S.epidermidis commonly found?

A

Found in invasive medical devices such as intravascular cannulas.

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11
Q

What is a virulence factor of S.epidermidis that allows it to be resistant to a lot of antibiotics and adhere to surfaces?

A

Biofilm production

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12
Q

Which infections does S. Saprophyticus cause?

A

UTIs in adult women (10%)

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13
Q

Which antibiotics are used to treat staphylococci infections?

A

Most commonly-
B lactamase resistant : flucloxacillin

If MRSA
Then- vancomycin.

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14
Q

What shape are streptococci?

A

Chain forming cocci

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15
Q

What are B haemolytic streptococci?

A

They produce haemolysins which cause a zone of clearing around bacterial colonies growing on blood agar. This group is further subdivided according to the polysaccharide present in bacterial cell wall. These are classified A-G

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16
Q

What classification is strep pyogenes?

A

Group A beta haemolytic strep.

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17
Q

What invasive conditions are caused by strep pyogenes?

A

Invasive- impetigo, pharyngitis, lymphangitis, necrotising fasciitis, septicaemia

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18
Q

What toxin mediated conditions are caused by strep pyogenes?

A

Streptococcal toxic shock syndrome, scarlet fever

19
Q

What are the post infective conditions caused by strep pyogenes?

A

Rheumatic fever, glomerulonephritis, syndehams chorea

20
Q

Which abx are group A strep sensitive to?

A

Penicillin.

21
Q

What are the virulence factors of streptococci?

A

M protein- resists phagocytosis
DNAses
Hyaluronidase

22
Q

Which classification are the viridans streptococci?

A

Alpha haemolytic- causes green discoloration on blood agar.

23
Q

Where are strep viridans found?

A

In the oropharyngeal flora

24
Q

What diseases can viridans strep cause?

A

Infective endocarditis

25
Q

What is the morphology of strep pneumoniae?

A

Gram positive diplococcus

26
Q

What classification is strep pneumoniae?

A

Alpha haemolytic

27
Q

What is the major virulence factor of strep pneumoniae?

A

Polysaccharide capsule- resists phagocytosis.

28
Q

Where is strep pneumoniae commonly found?

A

In oro and nasopharyngeal flora of healthy individuals.

29
Q

How is strep pneumoniae transmitted?

A

Respiratory route in droplet form

30
Q

What diseases can strep pneumoniae cause?

A

Pneumonia and meningitis

31
Q

Which group of patients are particularly at risk from strep pneumoniae infection?

A

Asplenic patients

32
Q

What is the first line treatment for strep pneumoniae infection?

A

Penicillin

Erythromycin is used as an alternative in penicillin allergy.

33
Q

What are enterococci?

A

Closely related to group D strep.
Group D polysaccharide allows them to be bile tolerant and to grow in GI tract where they present as minority members of flora.

34
Q

How are enterococci grown?

A

On macConkey agar.

35
Q

What is the most common member of the enterococci?

A

Enterococcus faecalis- is a cause of UTIs and other hospital acquired infections.

36
Q

Which abx can be used for enterococcal UTI?

A

Nitrofurantoin

37
Q

What is the morphology of c.perfringens?

A

Bacillus

38
Q

What conditions does c.perfringens live in?

A

Anaerobic conditions

39
Q

What toxins do clostridium perfringens bacteria produce?

A

Enterotoxin- causes food poisoning

Exotoxins

40
Q

What diseases does C.perfringens cause?

A

Gas gangrene

Food poisoning

41
Q

What abx are clostridia sensitive to?

A

Penicillin and metronidazole

42
Q

What is c.difficile?

A

An anaerobic spore forming G+ bacillus found in the enteric flora. Responsible for abx associated diarrhoea and pseudomembranous colitis.

43
Q

Which abx is c.difficile sensitive to?

A

Vancomycin, metronidazole.

Infection (12 decks)

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