2: staph: bacteremia, sepsis, and MRSA Flashcards Preview

ICM > 2: staph: bacteremia, sepsis, and MRSA > Flashcards

Flashcards in 2: staph: bacteremia, sepsis, and MRSA Deck (75)
1

what type of colonies does staph form on blood agar?

coag (+): golden B-hemolytic colonies
coag (-): small, white nonhemolytic colonies

2

rate of S. aureus colonization higher among:

-insulin-dependent diabetics
-HIVers
-patients undergoing hemodialysis
-individuals w/ skin damage

3

sites of S. aureus human colonization

-anterior nares
-skin (especially when damaged)
-vagina
-axilla
-perineum
-oropharynx

4

how many people are colonized?

25-50% of healthy people may be transiently or persistently colonized

5

diseases w/ increased risk for S. aureus infection

-diabetes
-congenital or acquired qualitative or quantitative defects of PMNs (neutropenia, CGD, chediak-higashi)
-skin abnormalities
-prosthetic devices

6

does MRSA invade much?

not really (only 5-10% of time) - mostly affects skin and soft tissue

7

describe pathogenesis of staph

-pyogenic -> abscesses
-inflam response, initial infiltrate of PMNs, then macrophages and fibroblasts
-localized/contained (coagulase) OR spreads to adjacent tissues/bloodstream

8

what does ER give anyone with a skin infection?

Bactrim + Kephlex - don't try to distinguish b/w staph and strep, so they give two drugs to cover both
-Bactrim: shitty dude for MRSA
-Kephlex: for methicillin sensitive + strep

9

3 toxins of staph

1. cytotoxins
2. pyrogenic toxin super Ag's
3. exfoliative toxin

10

what does the pyrogenic toxin super Ag's of staph mediate?

food-borne illness - toxin formed in food, sx present in absence of viable bacteria (enterotoxin)

staph TSS - toxin produced at site of colonization, causes clinical illness (TSST-1)

11

what does the exfoliative toxin of staph mediate?

staph scalded skin syndrome

12

why no staph vaccine?

anti-staph Ab's may be protective in vitro but have not shown protection in clinical trials

13

TSS treatment

Clindamycin
stops bacterial protein synthesis to stop toxin production

14

clinical manifestations of staph

-skin and soft tissue infection
-bacteremia
-cardiovascular infection
-sepsis and TSS
-splenic abscess
-bone and joint infection
-pulmonary infection
-meningitis
-bacteriuria

15

describe skin and soft tissue infections of staph

-impetigo (epidermis)
-folliculitis (superficial dermis)
-furuncules, carbuncles, abscesses (deep dermis)
-hidradenitis suppurativa (follicular infection of intertriginous areas)
-cellulitis, erysipelas, fasciitis (subQ tissues)
-pyomyositis (skeletal muscle)

16

describe CV infections of staph

-infective endocarditis (acute)
-cardiac device infection
-intravascular catheter infection
-septic thrombophlebitis

17

describe bone and joint infections of staph

-osteomyelitis - hematogenous, or secondary to a contiguous focus of infection
-prosthetic joint infection
-septic arthritis or bursitis

18

describe meningitis of staph

-most commonly occurs in the setting of head trauma or neurosurgery

19

describe bacteriuria of staph

-may be associated with indwelling urinary catheter
-probably a skin contaminant
-not typical urine infections symptoms

20

is necrotizing fasciitis more common with staph or strep?

strep

21

what is the leading cause of both community acquired and healthcare acquired bacteremia?

staph aureus

22

three categories of staph bacteremia

-healthcare-associated hospital onset (nosocomial)
-community-acquired
-healthcare-associated community onset (long term care facilities)

23

risk factors for staph bacteremia

-intravascular catheters
-MRSA colonization
-implanted prosthetic devices
-injection drug use

24

history associated with staph bacteremia

-recent skin or soft tissue infection
-presence of indwelling prosthetic devices
-injection drug use
-recent hospital exposure
-intravascular catheter

25

symptoms of metastatic infection with staph bacteremia

-bone or joint pain (vertebral osteomyelitis, discitis, epidural abscess)
-protracted fever or sweats (endocarditis)
-abdominal pain (LUQ = splenic infarction/abscess)
-CVA tenderness (renal infarction, psoas abscess)
-headache (septic emboli)

26

what must you make sure to include in physical exam of a patient with staph bacteremia?

careful cardiac exam for:
-new murmurs or evidence of heart failure
-stigmata of endocarditis
-neuro exam

27

what should you get as part of diagnostic eval for staph bacteremia?

-blood cultures (always 2 sets)
-echocardiography (TTE +/- TEE)
-other imaging based on symptoms

28

difference b/w strep and staph endocarditis ??

Strep viridans gets killed off pretty quickly by abx
staph blows through abx

29

treatment of staph aureus bacteremia in adults

-control source of infection
-empiric antibiotics pending sensitivity results (vancomycin)
-tailored therapy once sensitivities available
-MSSA: anti-staph PCN (nafcillin/oxacillin), cefazolin
-MRSA: vancomycin or daptomycin
-blood cultures 48-72h after start of therapy

30

duration of therapy in uncomplicated infection w/ no cardiac abnormalities

14d IV therapy

31

duration of therapy w/ deep focus of infection + more severe disease

varies

32

sepsis vs. SIRS (definitions)

sepsis: clinical syndrome complicating severe infection, signs occur in tissues remote from site of infection

SIRS: clinical syndrome complicating a noninfectious insult (i.e. pancreatitis, pulmonary contusion)

33

diagnostic criteria for SIRS include:

-temp above 38C or less than 36C (100.4F or 96.8F)
-HR above 90 bpm
-RR above 20 breaths/min of PaCO2 less than 32 mmHg
-WBC above 12,000 or less than 4000
-SBP less than 90 mmHg

34

special management problems with central catheter related infections?

if you have a central line + a fever: blood cultures + Abs
no source for fever: switch line over wire (half assed)

not high yield

35

steps of sepsis severity (4)

1. SIRS
2. Sepsis (2 SIRS + confirmed or suspected infection)
3. Severe Sepsis (Sepsis + signs of end organ damage + hypotension SBP less than 90 + lactate above 4 mmol)
4. Septic Shock (Severe sepsis w/ persistent: hypotension, signs of end organ damage, lactate above 4 mmol)

36

definition of septic shock

sepsis-induced hypotension persisting despire adequate fluid resuscitation (=vasodilatory shock)

37

problem with nafcillin

-have to infuse every 4 hours
-causes phlebitis (irritation of veins)

38

risk factors for sepsis:

-ICU patient with nosocomial infection
-bacteremia
-age above 65 y/o
-immunosuppression
-diabetes
-cancer
-community acquired pneumonia
-genetic factors contributing to susceptibility to infection

39

where is daptomycin great? where is it not great?

bloodstream infection, but doesn't get into lungs super well

40

what is the increasing incidence of sepsis since the 1970s thought to be due to?

-advancing age
-immunosuppression
-multi-drug resistant infections

41

population with the highest incidence of sepsis

African American male
over 65 y/o
in winter (increased prevalence of resp infections)

42

top three pathogens (by frequency) causing sepsis

1. G(+) bacteria
2. G(-) bacteria
3. fungal pathogens

43

only things that reliably kill off enterococcus

linazolid
penicillin (if sensitive)
vancomycin

44

what should clinical evaluation of a septic patient include?

-determine source of infection (history and physical)
-assess respiratory status (O2 sats, respiratory effort)
-assess perfusion (BP, capillary refill, pulses)
-assess end-organ effects (lactate level, renal and hepatic fxn, mental status)

45

early management of sepsis

-control of airway (supplemental O2, intubation, ventilation)
-establish venous access (central venous catheter)
-maintain perfusion (IV fluids, vasopressors/inotropic agents)

46

how to control the septic focus

-early antibiotics (empiric therapy initially, then tailored to culture results)
-possible debridement/surgical intervention

47

what are some vasoactive agents used in septic shock?

-dobutamine
-dopamine
-epi
-norepi
-phenylephrine
-amrinone

48

which vasoactive agent has largest effect on heart rate?

epi

49

which vasoactive agents have largest effects on contractility?

dobutamine
epi
amrinone

50

which vasoactive agents have largest effects on arterial constriction? which have opposite effects (dilation)

norepi
phenylephrine

dilators:
dobutamine
amrinone

51

source control methods: sinusitis

surgical decompression of sinuses

52

source control methods: pneumonia

-

53

source control methods: empyema thoracis

-

54

source control methods: mediastinitis

-drainage
-debridement
-diversion

55

source control methods: peritonitis

-resection, repair, or diversion of ongoing sources of contamination
-drainage of abscesses
-debridement of necrotic tissues

56

source control methods: cholangitis

-bile duct decompression

57

source control methods: pancreatic infection

-drainage or debridement

58

source control methods: UTI

-drainage of abscesses
-relief of obstruction
-removal or changing of infected catheters

59

source control methods: catheter-related bacteremia

-removal of catheter

60

source control methods: endocarditis

-valve replacement

61

source control methods: septic arthritis

-joint drainage and debridement

62

source control methods: soft tissue infection

-debridement of necrotic tissue and drainage of discrete abscesses

63

source control methods: prosthetic device infeciton

-device removal

64

mortality rates with sepsis:
-general
-SIRS only
-sepsis only
-severe sepsis only
-septic shock only

10-50% - increases with severity of sepsis
-SIRS: 7%
-sepsis: 16%
-severe sepsis: 20%
-septic shock: 46%

65

what mediates methicillin resistance?

PBP2a - PBP encoded by mecA gene

66

where is mecA located?

on a mobile genetic element (staph chromosome cassette SCCmec)

67

what is the leading cause of surgical site infections?

HA-MRSA

68

diagnosis of HA-MRSA electrophoresis?

USA100 or USA200 pulse-field pattern

69

difference in type of infection associated with HA-MRSA vs. CA-MRSA

HA: severe, invasive disease

CA: skin and soft tissue infections in healthy young persons, community outbreaks

70

diagnosis of CA-MRSA electrophoresis?

USA300 or USA400 pulse-field pattern

71

risk factors for MRSA

-recent hospitalization
-residence in long-term care facility
-recent antibiotic therapy***
-HIV
-MSM
-injection drug use
-hemodialysis
-incarceration
-military
-sharing needles, razors, or other sharps
-sharing sports equipment
-diabetes
-prolonged hospital stay

72

what was the likely mechanism that brought about MRSA?

antibiotic selective pressure
-abx use (especially cephalosporin and fluoroquinoline) correlated with risk for MRSA colonization and infection

73

key components of the infection control program at the Billings Clinic to prevent/cut down prevalence of MRSA?

-hand hygiene
-decontamination of environment and equipment
-contact precautions for infected and colonized patients
-active surveillance cultures (ASCs)

74

describe the active surveillance

nares culture on admission, discharge, transfer, or death

75

what is the next threat on the horizon?

VRSA