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Thera VII > 02 Gram-Positive Cocci > Flashcards

02 Gram-Positive Cocci Flashcards

1
Q

What are the Gram-Positive Cocci?

A

Staphylococci (grapelike clusters). Streptococci (Spherical cocci in chains or pairs)

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2
Q

How does Staphylococci cause disease?

A

Cause disease by producing toxins and by multiplying in tissues –> inflammation

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3
Q

What are the diseases of S. aureus?

A

Abscesses. Endocarditis. Osteomyelitis. Food poisoning. Toxic shock syndrome (TSS)

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4
Q

What are the diseases of S. epidermidis?

A

Endocarditis. Infected foreign bodies

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5
Q

What are the diseases of S. saprophyticus?

A

UTIs

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6
Q

Which Staphylococci will test positive in a coagulase test?

A

S. aureus

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7
Q

How are staphylococci transmitted?

A

Normal human flora. S. epidermidis = skin, mucous membranes. S. aureus = nose, skin (Diarlysis, DM, IVDA, surgical pts, AIDS. Colonized pts have increased risk of becoming infected)

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8
Q

What are the clinical findings from Staphylococci?

A

Inflammatory. Toxin-mediated

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9
Q

What are the inflammatory clinical findings from Staphylococci?

A

Skin infections (impetigo, furuncles, cellulitis, surgical wound infections). Bacteremia from localized lesion. Endocarditis. Osteomyelitis and arthritis (hematogenous or traumatic). Pneumonia. Abscesses after bacteremia

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10
Q

What are the Toxin-Mediated clinical findings from Staphylococci?

A

Food poisoning due to ingestion of enterotoxin preformed in foods, incubation period (1-8 hours). TSS in menstruating women using tampons or those with wound infections. Scalded skin syndrome in young children - sloughing of the superficial layers of the epidermis in response to the presence of exfoliation

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11
Q

What are some common causes of Streptococci?

A

Pharyngitis. Skin and soft tissue infections (impetigo, cellulitis, necrotizing fasciitis). Pneumonia. UTI. Intraabdominal infection. Endocarditis

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12
Q

What are the two types of bacteria that should always be considered with tissue infections?

A

Staph or Strep

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13
Q

How are Streptococci classified?

A

Alpha-Hemolytic (partial lysis of RBC in the agar). Beta-Hemolytic (complete lysis)

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14
Q

What Streptococci group is S. pneumoniae?

A

Alpha-hemolytic

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15
Q

What Streptococci group is Viridans Streptococci?

A

Alpha-hemolytic

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16
Q

What Streptococci group is S. pyogenes?

A

Group A (beta-hemolytic)

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17
Q

What Streptococci group is S. agalactiae?

A

Group B (beta-hemolytic). GBS

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18
Q

What Streptococci group is Enterococci?

A

Group D (beta-hemolytic)

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19
Q

What Streptococci group is S. bovis?

A

Group D (beta-hemolytic)

20
Q

How is Streptococci commonly transmitted?

A

Normal flora of throat, skin, intestines. Oropharynx: viridans strep, S. pneumoniae. Skin: S. pyogenes. Female genital tract: S. agalatiae. Lower intestinal tract: enterococci, anaerobic streptococci

21
Q

Where is S. pyogenes found?

A

Skin

22
Q

Where is S. agalactiae found?

A

Female genital tract

23
Q

Where is Viridans Strep found?

A

Oropharynx

24
Q

Where is S. pneumoniae found?

A

Oropharynx

25
Q

What are some common causes of Group A Strep - S. pyogenes?

A

Pharyngitis (fever, tender cervical lymph nodes, inflammation, exudate, fever), if untreated, recovery in 10 days; rheumatic fever may follow (may extend to otitis, sinusitis, mastoiditis, meningitis). Cellulitis, necrotizing fasciitis - exotoxin B rapidly destroys tissue. Pyoderma (impetigo) - communicable superficial infection of abraded skin that forms pus or crusts (acute glomerulonephritis may follow)

26
Q

What are immunologic disorders from Streptococci?

A

Inflammation in an organ that was NOT infected by the streptococci. NOT benefit from PCN treatment after onset. Occurs 2-3 weeks after infection. Acute glomerulonephritis (AGN). Rheumatic fever

27
Q

What is Acute Glomerulonephritis (AGN)?

A

Typically occurs 2-3 weeks after skin infection with Group A Strep. HTN, facial edema (periorbital) and ankles, “smokey” urine (rbcs) –> complete recovery in most pts. Initiated by antigen-antibody complexes on the glomerular basement membrane

28
Q

How is AGN prevented?

A

By eradication of nephritogenic streptococci from skin colonization

29
Q

What is Rheumatic Fever?

A

Occurs ~2 weeks after Group A Strep pharyngitis. Fever, migratory polyarthritis, carditis may damage mitral and aortic valves. Resulting from cross-reactions b/w strep antigens and antigens of joint and heart tissue. “Autoimmune” disease greatly exacerbated by recurrence of strep infection –> long term PCN prophylaxis

30
Q

How is Rheumatic Fever prevented?

A

By treatment of strep infection within 8 days after onset

31
Q

For laboratory diagnosis, why are gram-stain smears in pharyngitis useless for streptococci?

A

Cannot distinguish S. pyogenes from normal flora (viridans strep). Useful from skin lesions or wounds

32
Q

What is the “Rapid Strep Test”?

A

Direct detection of Group A polysaccharide antigen in throat swabs, 10-15 minutes, highly specific (>95%), 80-90% sensitive

33
Q

What is a common cause of Group B Strep (S. agalactiae)?

A

Neonatal sepsis and meningitis. Infected in utero or during passage thru birth canal. Early-onset (1st 3 days): 75% of neonatal infection (pneumonia, prolonged membrane ruptures (>18 hours) in colonized women; low-birth-weight. Late-onset (10-14 days, up to 3 months): meningitis more common; full-term infants

34
Q

How is S. agalactiae in DM?

A

14x higher risk - Bacteremia from infected foot ulcers or cellulitis

35
Q

What are some risks of getting S. agalactiae infection in adults?

A

DM. CVD. Solid cancers. Alcoholism. Cirrhosis

36
Q

What is done to prevent GBS is pregnant women?

A

Found in 2-7% of patients urine. Screen by culture at 35-37 weeks. Infection causes septic abortion, stillbirth, chorioamnionitis, endometritis

37
Q

What is Viridans Strep?

A

Part of mouth flora. Infective endocarditis (organism enters bloodstream from the oropharynx as a result of poor oral hygiene or after dental surgery)

38
Q

What are the Group D Streptococci?

A

Enterococci. S. bovis

39
Q

What can Enterococci cause?

A

UTIs in catheterized pts. Endocarditis following GI or GU surgery or instrumentation. Intraabdominal and pelvic infections

40
Q

What is most commonly associated with S. bovis?

A

Bacteremia or endocarditis is strongly associated with colon cancer

41
Q

What can Strep pneumoniae (pneumococcus) cause?

A

Respiratory tract infections: otitis, sinusitis, pneumonia. Bacteremia. Meningitis

42
Q

What are the characteristics of S. pneumoniae?

A

Polysaccharide capsules (virulence factors which interfere with phagocytosis. Infection or administration of vaccine elicit specific antibody formation which helps opsonizes the organism –> phagocytosis)

43
Q

What is done for prevention of S. pneumoniae?

A

Vaccines. Pneumococcal vaccine (23-type): immunocompromized, elderly. 7-valent conjugate vaccine in children

44
Q

What is the Transmission/Pathogenesis of S. pneumoniae?

A

5-50% of the healthy population harbor virulent organisms in oropharynx. Produce IgA protease enhance the organisms ability to colonize the mucosa of the upper respiratory tract. NO toxins

45
Q

What are the predisposing host factors to infection?

A

Compromised gag reflex (CNS depression, alcohol or drug intoxication). Abnormality of the respiratory tract (pooling of mucus, bronchial obstruction). Pulmonary congestion, HF. Splenectomy. Sickle cell anemia, nephrosis

46
Q

What is the laboratory diagnosis for S. pneumoniae?

A

Predominant organism in sputum smears. Alpha-hemolytic colonies on blood agar. Antimicrobial susceptibility testing - important for therapeutic decision. Can detect by urin antigen from first voided clean catch urine (> 90% specificity in adults, 21-54% false positive in children with nasopharyngeal carriage and no evidence of pneumonia)

Thera VII (37 decks)

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