Bites, MRSA and Fasciitis Flashcards
(62 cards)
1
Q
infectious complications of bites
A
-breach of protective skin barrier –> innoculation of microorganisms into deeper tissues
2
Q
what is the microbiology make up reflected by an animal bite?
A
- oropharyngeal flora
- soil
- skin/feces of animal
3
Q
white type of bites have higher rates of infection?
A
cat and human bites > dog bites
4
Q
what are the determinants of infection in bites?
A
- the animal
- location
- type of injury
5
Q
what location of a bite is of particular concern?
A
hand - b/c closed spaced infection
6
Q
Dog bite prevalence
A
- 80% of all animal bites
- 5-20% become infected
7
Q
characteristics of dog bites
A
-usu by victims pet or dog known to victim
-most often upper extremity
- <4 yo most to head/neck
-most are provoked
(if not provoked, consider rabies)
8
Q
what percent of cat bites become infected?
A
30-50%
9
Q
what located of bites are more commonly infected?
A
bites to extremities > head, neck, face
10
Q
what is the single MC isolate species in bites?
A
pasteurella**
11
Q
infection 8-24 hrs after a bite w/ P. multocida results in what?
A
rapidly progressive cellulitis w/ purulent drainage
12
Q
common reasons for human bites
A
- self inflicted
- medical personnel
- fights
- domestic abuse
13
Q
What is a common location for a human bite during a fight?
A
a wound over MCP joint
14
Q
percentage of infection in human bites
A
10-30%
15
Q
common infective agent in human bites
A
viridans streptococci
16
Q
when do you refer to ortho for a human bite?
A
- injury to extensor tendon
- joint capsule over MCP joint
17
Q
essential w/u of bite
A
- culture and gram stain of all infected wounds
- vigorous cleansing and irrigation
- radiographs
18
Q
closure of bite wounds
A
- this is controversial
- don’t suture if infected
- don’t suture puncture cat wounds
- sm uninfected wounds may close by secondary intention
- facial wounds usu sutured
19
Q
indications for abx prophylaxis after a bite
A
- cat bites any location
- all hand bites
- comorbidities (DM, liver dz, etc)
20
Q
tx of choice for prophylaxis after bite
A
augmentin 500 mg TID x 5-7 days
21
Q
alternative tx options for prophylaxis after bite
A
- clindamycins
- doxy
- bactrim
- moxifoxacin
- dicloxacillin
22
Q
rabies
A
- rapidly progressive infectious dz of CNS caused by rabies virus
- transmitted via animal vector
- most occur in wild animals: raccoons, skunks, bats, foxes
23
Q
rabies virus family
A
-of family rhabdoviridae
24
Q
what 2 genera of rabies viruses cause human disease?
A
- lyssavirus
- vesicularvirus
25
transmission route of rabies virus
-viral infection of salivary glands of the biting animal
26
incubation period of rabies
20-90 days - remains close to site of exposure
27
pathogenesis of rabies virus
- virus binds to nicotinic Ach receptor in muscle on postsynaptic membrane of neuromuscular junction
- spreads and replicated along PNS to dorsal root ganglia, SC, and CNS then to all organs and tissue
- leads to acute encephalitis of gray matter of CNS, basal ganglia and SC
28
pathognomonic histology for rabies
negri bodies**
29
what are the 2 clinical forms of rabies
- encephalitis (furious) - 80%
| - paralytic (dumb/apathetic) - 20%
30
encephalitic rabies
- episodes of generalized hyperexcitiabilty, disorientation, hallucinations, bizarre behavior
- autonomic dysfunction: hypersalivation, hyperthermia, tachy, HTN, piloerection, cardiac arrythmias, priapism
31
paralytic rabies
- paresis of bitten extremity
- spread to quadriparesis
- facial weakness
- progressing to coma and organ failure
32
w/u for rabies once sx are evident
- Ag and Ab testing (DFA)
- CSF, saliva, and tissue testing
- brain bx
- skin bx
- RNA by RT-PCR
33
therapy for rabies
- thorough wound cleansing is vital
- tetanus prophylaxis
- no specific tx has showed benefit in clinical rabies
34
contraindicated tx in rabies
- steroids**
| - shortened incubation time and increased mortality in animal models
35
indication for rabies postexposure prophylaxis (PEP)
-consider the animal and the bite - if provoked or not and consult w/ public health authority
36
rabies vaccines
- Imogram/HyperRab: passive immunity w/ human rabies immune globulin (HRIG)
- Imovax/RabAvert: purified inactivated rabies vaccines
37
dosing/schedule of rabies vaccines
- Imogram/HyperRab: no later than 7 days after 1st vaccine at site of bite - 20IU/kg
- Imovax/RabAvert: 4 separate 1 ml doses IM deltoid days 0, 3, 7, 14
38
considerations on rabies PEP
never administer HRIG and vaccine in same syringe or into same anatomic site
39
2 clinically important spider bites in North America
- lacrodectism (Black Widow - lacrodectus species)
| - loxoscelism (brown recluse - loxosceles species)
40
lactrodecism
- resides in dark places
- shiny black w/ red hourglass marking on ventral abdomen
- F more potent
- summer and early autumn
- bite perceived as sharp pinprick or unnoticed
41
lactrodecism bite pathogenesis
- venom contains toxin causing Ach & NE release/depletion from presynaptic terminals
- painful cramps w/ rigidity from bite site to large muscles of extremities and trunk
42
other sequelae of lactrodecism bite
- salivation
- lacrimation
- diaphoresis
- urination
- defecation
- GI upset
- emesis
- renal failure
- rhabdo
- resp arrest
- cerebral hemorrhage
- cardiac failure
43
tx for lactrodecism bite
- RICE and tetanus prophylaxis
- if severe: hospital admin for IV pain control and muscle spasms
- antivenom available but questionable efficacy
44
loxoscelism
- south-central US
- dark brown violin shape on the cephalothorax (violin neck points back)
- 6 eyes in pairs
- live in dark places
- not aggressive
45
active enzymatic components of loxoscelism venom
- sphingomyelinase D
| - hyaluronidase
46
outcome of loxoscelism bite
- usu only cause minor injuries w/ edema and erythema
| - occasionally causes severe necrosis of skin/subQ tissue and more rarely causes systemic hemolysis
47
loxoscelism bite characteristics
- initially is painless or may produce a stinging sensation - often unaware of bite
- w/i hours becomes painful and pruritic w/ central induration surrounded by zones of ischemia and erythema
- if severe: erythema spreads and the center of the lesion becomes hemorrhagic w/ bulla or necrotic
- black eschar forms and sloughs weeks later
48
systemic variant of loxoscelism bite
- may occur in about 10%
- renal failure, rhabdo, hemolysis
- 24-72 hrs after bite
49
MRSA
-strain of staph aureus resistant to all beta lactam abx currently available
50
hospital associated MRSA
-invasive disease in debilitated or immunocompromised individuals, including pneumonia, bloodstream infections such as endocarditis, deep wound infection and osteomyelitis
51
community acquired MRSA
- MC causes pyogenic skin and soft tissue infection in the form of boils, deep abscesses, and cellulitis
- capable of potentially lethal infection such as necrotizing fasciitis, necrotizing pneumonia and bacteremia
52
tx of HA-MRSA
IV vancomycin, daptomycin or tigecycline
| -use contact precaustions
53
primary tx of CA-MRSA
I&D
54
tx of MRSA for pts who have abscesses to multiple sites or rapid progession of associated cellulitis
- abx x 5-10 days
| - options: bactrim, tetracyclines, linezolid, clindamycin
55
tx for MRSA if recurrent infection or if other household members develop infections
- nasal decolonized w/ mupirocin twice per day x 5-10 days
| - or same tx + topical body decolonization w/ skin antiseptic solution x 5-14 days
56
necrotizing fasciitis
rapidly progressive infection of the deep fascia w/ necrosis of the subQ tissue
57
type 1 necrotizing fasciitis
- polymicrobial
- usu delivered into SQ via surgery, trauma, bowel perf or IV drug use
- MC form (90%)
- MC to extremity, abd wall, perineum or near operative wounds
58
type 2necrotizing fasciitis
- monomicrobial
- usu GAS "flesh eating bacteria"
- MRSA becoming more prominent cause
59
what are the 2 greatest risk factors for necrotizing fasciitis?
- DM
| - severe peripheral vascular dz
60
progression of necrotizing fasciitis
- rapid progression of erythema, ecchymosis w/ bullae, and necrosis or gangrene
- edematous induration of SQ tissues extending beyond margin of erythema
- high fevers and unrelenting pain out of proportion to cutaneous findings
- anesthesia of skin d/t infarction of cutaneous nerves
61
gold standard for diagnosis of necrotizing fasciitis
- open surgical exploration
| - histology and culture of deep tissue bx
62
primary therapeutic modality in necrotizing fasciitis
surgical debridement
- frist one w/i 24 hrs from onset of sx
- repeat until all devitalized tissue removed
- start abx immediately
