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FM2 > Gram Positive Cocci > Flashcards

Gram Positive Cocci Flashcards

1
Q

List four prototypic diseases associated with Streptococcus pneumoniae

A

Otitis media
Sinusitis
Pneumonia
Meningitis

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2
Q

Describe treatment for Strep pneumoniae meningitis

A

Widespread penicillin resistance

tx with vancomycin and cefriaxone or dexamethasone

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3
Q

Describe Streptococcus pneumonia morphology

A

Gram positive, lancet shaped diplococci
a-hemolytic on blood agar
opaque mucoid colonies

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4
Q

Describe how to distinguish Streptococcus pneumoniae from Streptococcus viridans

A

Strep pneumoniae has + bile solubility and + optochin sensitivity

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5
Q

The most important virulence factor for Streptococcus pneumoniae is the ___________, which is antiphagocytic and stimulates an intense hose inflammatory response

A

capsular polysaccharide

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6
Q

Outcomes from septic shock may be improved by the addition of ________ to treatment regime

A

corticosteroids- block inflammatory events at subcellular level

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7
Q

True or false: Streptococcus pneumoniae remains highly susceptible to penicillin

A

FALSE.

high levels of penicillin resistance due to altered PBPs

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8
Q

List populations that are highly susceptible to Streptococcus pneumoniae

A

Alcoholics (aspiration)
COPD, heart failure
Influenza A (airway damage, predisposes to aspiration)
Diseases that cause inability to mobilize antibody response
Sickle cell disease
Asplenics
CSF leaks ex following head trauma
People living in close quarters (ex prison)

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9
Q

True or false: most influenza-related deaths are due to direct effects of the influenza virus

A

FALSE

Deaths often due to decompensation, secondary bacterial infection, pneumonia

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10
Q

True or false: Streptococcus pneumoniae is spread by airborne respiratory droplets but is not highly contagious

A

TRUE

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11
Q

True or false: the vaccine for Streptococcus pneumoniae is not recommended to be routinely administered in children

A

FALSE

is one of standard vaccines of childhood

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12
Q

A new ______ pneumococcal vaccine has been shown in trials to be 89% effective against any serotype of S. pneumoniae

A

conjugate

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13
Q

Children with otitis media more than ____ times for year should receive antibiotic prophylaxis against S. pneumoniae

A

4x per year

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14
Q

List treatment regime for the common diseases caused by S. pneumoniae

A

Otitis media: Amoxicillin 80 mg/kg/d or erythromycin Sinusitis: Amoxicillin-clavulinate or FQ
Pneumonia: Ceftriaxone + Macrolide or FQ
Meningitis: Ceftriaxone + Vancomycin

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15
Q

List prototypic diseases associated with Group A Streptococcus

A 
Pharyngitis
Impetigo
Erysipelas
Cellulitis
Toxic shock syndrome
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16
Q

List the prototypic diseases associated with Group B Streptococcus

A

Pueperal and neonatal sepsis

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17
Q

List the prototypic diseases associated with Group D Streptococcus

A

Urinary tract infection
Surgical wound infection
Endocarditis

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18
Q

List prototypic diseases associated with viridans a Streptococcus

A

Dental caries
Bacteremia
Subacute endocarditis

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19
Q

List the prototypic diseases associated with Peptostreptococcus (anaerobic strep)

A

Peritonitis

Intraabdominal abscess

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20
Q

Describe the morphology of Streptococci

A

Gram positive cocci in pairs and chains

Convex, opaque colonies

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21
Q

Streptococcus pneumoniae are __-hemolytic. Group A and B Streptococcus are ___- hemolytic, Group D are often ___- hemolytic

A

S. pneumoniae: a-hemolytic
Group A and B: B-hemolytic
Group D: y-hemolytic

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22
Q

The __ polysaccharide is an important antigen of many Streptococcus and is the basis of the Lancefield grouping scheme

A

C polysaccharide

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23
Q

The __ protein is a virulence factor specific to Group A Streptococcus and is the basis of the Lancefield typing scheme

A

M protein

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24
Q

M protein is antiphagocytic, promotes binding to surface fibronectin, and plays a role in post-streptococcal sequelae including _______ and ________

A

Rheumatic fever and glomerulonephritis

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25
Q

Organisms that are a-hemolytic can be Strep ____ or Strep _____; the two are distinguished on the basis of the _________test

A

Viridans or pneumoniae

Copper disc test

26
Q

Group D Streptococcus includes two subgroups:

A

Enterococci and non-enterococci

27
Q

Enterococci (do/do not) grow on 6.5% salt and (are/ are not) penicillin sensitive

A

Do grow on 6.5% salt

Not penicillin sensitive

28
Q

Community acquired infections caused by enterococci include ________. Nosocomial infections caused by enterococci include __________

A

Community: endocarditis, UTI
Nosocomial: catheter associated UTI, bacteremia, surgical site infections

29
Q

______ toxin of Group A Streptococcus causes Scarlet fever and is produced by _______ phage

A

Erythogenic toxin; lysogenic phage

30
Q

List some extracellular enzymes and toxins produced by B-hemolytic Streptococci

A 
Streptolysin O, S
Diphosphopyridine nucleotidase
Streptokinases 
Deoxyribonucleases 
Hyaluronidase
Proteinase
31
Q

There are two forms of toxic shock syndrome: the Staphylococcus aureus form is mostly associated with tampon use and has (high/low) mortality. The form associated with Group ___ Streptococcus a necrotizing infection with (high/low) mortality in healthy people

A

S. aureus: low mortality

Streptococcal: high mortality

32
Q

The treatment for Streptococcal TSS includes:

A

Penicillin

Surgical debridement

33
Q

Rheumatic fever and glomerulonephritis are _______ sequelae of Group A Strep infection and are mediated by ____ protein

A

non-suppurative; M protien

34
Q

True or false: clinical features alone are highly diagnostic for Strep pharyngitis

A

false, only 50-75% acurate

35
Q

True or false: most sore throats are due to Streptococcus

A

False, most due to viral infection or mycoplasma

36
Q

List suppurative complications of Group A Strep pharyngitis

A

Peritonsillar abscess
Pneumonia with empyema
Bacteremia, distant metastatic infection (rare)

37
Q

Differentiate rheumatic fever from glomerulonephritis on the basis of pathogenesis, precipitating infection, antibiotic prevention, treatment

A 
Rheumatic fever:
Autoimmune cause, heart and joints
Precipitated by pharyngitis
Is preventable with antibiotics 
Tx= aspirin
Glomerulonephritis:
Immune complex mediated 
Precipitated by skin infection
Not preventable with antibiotics
Tx= supportive only
38
Q

Group ___ Strep is transferred from mother to neonate during parturition. Group __ is usually nosocomial. Group ___ Strep is transmitted by airborne droplets or contact

A

B
D
A
All others- autochthonous

39
Q

List susceptible hosts for Group A Strep

A

College students, military recruits, prisoners
Neonates and post-partum women
Damaged skin
Post-surgery

40
Q

List preferred treatment for Streptococcal infections

A

Penicillin

Erythromycin or vancomycin if penicillin allergy

41
Q

List preferred treatment for enterococcal infections

A

Ampicillin
Penicillin AND gentamicin
Vancomycin

42
Q

What is the reservoir of Staphylococcus aureus?

A

Nares, skin, mucosal surfaces

43
Q

Describe modes of transmission of Staphylococcus aureus

A
  • individual’s endogenous flora spreads to normally sterile site
  • spread person to person by fomites, contact, respiratory droplets
  • ingestion of food contaminated with toxin
44
Q

List general categories of Staphylococcus aureus virulence factors

A
  • surface proteins
  • toxins
  • enzymes
  • antibiotic resistance genes
45
Q

Describe two surface proteins of Staphylococcus aureus that act as virulence factors

A
  • teichoic acid- aids in attachment by binding fibronectin

- protein A- inhibits antibody-mediated clearance by phagocytes

46
Q

Describe toxins of Staphylococcus aureus that act as virulence factors

A
  • cytotoxins: ex PVL- damage mammalian cell membranes, alpha/beta/delta/gamma toxins
  • exfoliative toxins- desquamation
  • enterotoxins- GI symptoms
  • TSST-1- activation of T cells, cytokine storm, superantigen
47
Q

List two major enzymes of Staphylococcus aureus that act as virulence factors

A
  • coagulase: converts fibronectin to fibrin, protects from phagocytosis
  • catalase: breaks down H2O2
48
Q

List the major cutaneous infections caused by S. aureus

A 
Impetigo
Cellulitis
Folliculitis
Furuncle, carbuncle
Wound infection
Mastitis
49
Q

Food poisoning caused by S. aureus is mediated by a _____-stable toxin; illness occurs (soon/late) after food ingestion.

A

heat stable

soon

50
Q

Toxic shock syndrome caused by S. aureus is commonly associated with _____ use or surgical packing. Mortality is (high/low). ________ is critical.

A

tampon
low mortality
fluid resuscitation

51
Q

Scalded skin syndrome is more common in (young children/ adults) and mortality is (high/low)

A

young children

low mortality

52
Q

List the major risk groups for S. aureus infection and S. epidermidis infeciton

A

S. aureus:

  • menstruating women (TSS)
  • neonates (scalded skin)
  • young children (impetigo)
  • implanted medical devices (bacteremia, endocarditis)
  • immunocompromised, post-viral (pneumonia)
  • IV drug users (bacteremia, endocarditis)
  • burn/ post-op patients (soft tissue infection

S. epidermidis: mostly associated with implanted medical devices

53
Q

Describe lab diagnostics to differentiate S. aureus from S. epidermidis

A

S aureus is coagulase positive and positive mannitol fermenter, most colonies yellow-gold and hemolytic

S. epidermidis is coagulase negative, does not ferment mannitol, colonies are nonhemolytic and white

54
Q

List important measures to prevent Staphylococcal infections

A

Hand hygiene, proper wound cleaning, proper food handling, limiting long term use of catheters, chemoprophylaxis to prevent post-op surgical site infections

55
Q

Describe the normal reservoir of Staphylococcus epidermidis infection

A

skin, mucous membranes

56
Q

Describe Staphylococcus epidermidis virulence

A

Largely associated with ability to form biofilms, which act as barrier to antibiotics and host immunity, form on implantable medical devices

57
Q

List major diseases associated with Staphylococcus epidermidis

A 
Hospital acquired bacteremia
Endocarditis
Catheter infections
Implanted medical device infection 
Surgical site infection (could develop up to 3 yrs post-op)
58
Q

Staphylococcus saprophyticus is a coagulase negative staph that may cause ____, typically in adolescent, newly sexually active females

59
Q

True or false: staph described as “methicillin resistant” can be treated with other beta lactam antibiotics and semi-synthetic penicillins

A

FALSE
Resistance mechanism imparts resistance to more than methicillin- applies to all beta lactams, semi-synthetic penicillins, most cephalosporins, monobacams, carbapenems.

60
Q

______ and ________ are antibiotics that were developed in response to the threat of vancomycin resistant S. aureus

A

Linezolid and daptomycin

61
Q

True/ false: when staphylococci infect an implanted medical device, appropriate treatment involves long term IV antibiotics and leaving the device in to sterilize it

A

False, rarely able to resolve coagulase - infection without removing the infected device due to biofilm formation

FM2 (11 decks)

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