M. 1: Infectious Disease Flashcards
Lyme Disease
d/t borrelia burgdorferi (Bb) a spirochete, transmitted by ticks. in USA, mostly in northeast, mid-Atlantic states, Wisconsin, Minnesota, Northern California. Natural host is gray squirrel/fence lizard/ white foot mouse or deer. tick size is 1-4mm. highest transmission to boys 5-9 years old. nymphal ticks feed 36-48 hours, adult feeds 2-3 days before risk is significant. most infections during June-August.
Lyme disease s/s
stage 1: within 1-2 weeks, rash at inoculation site (erythema migrans) red annular macule/papule that progresses in a couple days to be surrounded with clear ring and a larger annular red ring. Bull’s eye, 5cm in size diagnostic. can have multiple lesions. Warm, pruritic, not painful. fades after several weeks. Can look different but rapid enlargement is characteristic. may have s/s of fever, malaise, headache, arthralgia, myalgia, stiff neck. Stage 2: early disseminated with secondary lesions similar but smaller. Frequent headaches, lethargy, neck pain, mood swings, irritability, neuralgia, paresthesia, motor/sensory impairment, cranial neuropathies, cardiac issues (AV heart block), and general illness weeks to 2 years without treatment. stage 3: late: pauciarticular or monoarticular arthritis weeks to months post bite. chronic neurological issues in 5% untreated. knees commonly affected. red, hot, edematous joints not as painful as bacterial arthritis. resolves but is recurrent and migratory.
Lyme disease diagnostics
EM is diagnostic. if no characteristic EM, serologic tests for IgM are + 2-4weeks after a bite and may indicate prior infection because they don’t decline for 4-6months after disease onset. Do ELISA or indirect IFA; if negative, no further testing. if + or unsure, test with IgM and IgG Western Blot for Bb antibodies if s/s <30 days. if s/s >30 days, IgG western blot alone. if 1 month + of s/s, IgG alone to support diagnosis. Differentials: eczema, tines, granuloma annular, cellulitis, insect bite, osteomyelitis, WNV, Parvo, relapsing fever, lymphadenopathy, meningitis, MS, ALS, thyroid disease.
Lyme disease treatment
prophylactic doxycycline, amoxicillin, or cefuroxime in children with history of : tick bite on 36-72 hours and in endemic area. If unidentified as Ixodes species, no prophylaxis but watch closely, and if s/s within 30 days, start diagnostics and treatment. Stage 1: <8 years old amoxicillin, >8 doxycycline; if unable to take either, cefuroxime. Disseminated disease, refer.
Post-Lyme disease syndrome
s/s that persist after thought d/t immune mediated inflammation rather than infection. lingering fatigue, musculoskeletal pain, cognitive/short term memory difficulties.
CA- MRSA
altered Penicillin-binding protein with decreased sensitivity to beta-lactam abx minus ceftaroline. toxicity > inflammatory cascade > tissue necrosis. Risks: boil/furuncle/abscess without draining puss that is red, warm, painful, potentially rapid onset; treatment failure with B-lactam agent; other family members infected; recent hx skin infection; neonate with infection; skin lesions looking like spider bite, or larger lesions; pus present; hx recurrent, small, contender, nonpruritic maculopapular lesions that become pruritic/painful; participation in contact sports; ethnic minority or poor living conditions; breast abscess; hx in past year of hospital, surgery, or percutaneous permanent indwelling medical device; child care and <2 years; CF or progressive RTI; head/neck infection.
MRSA diagnostics
tx superficial skin lesions without obtaining cultures often, outside of neonatal period. can be topical bacitracin/mupirocin 3x daily 7-10days; oral or IV abx for widespread impetigo. drug covering for MRSA on basis of prevalence of MRSA, if nosocomial infection, and severity. I&D with culture is treatment of choice for non-draining but fluctuant abscess. empiric treatment if severe local infection, s/s systemic toxicity, failed response to prior PO treatment. IV abx possible for temp >38, HR >90, RR >24, WBC >12000 or <400, immunocompromised, or risk endocarditis.
MRSA treatment
I&D with cultures for draining fluids, abx if severe local infection, systemic s/s etc. for deep infections without fluid fluctuations and s/s bacteria (chills, fever, malaise), use warm compresses and PO antibiotics. uncomplicated soft tissue infection without fluid: empiric topical mupirocin 2%; moist heat on small furuncles. tx ecthyma and impetigo with PO abx 7 days. MRSA treatment if abscesses or rapidly progressing local infection with s/s cellulitis; systemic s/s; comorbidities/immunosuppression; abscess in hard to drain area; lack of response to I&D. for recurrent, review hygiene/wound care; decolonization with nasal mupirocin bid 5 days (groin/rectal area of diapered children); daily antiseptic body wash for up to 2 weeks, or diluted bleach baths 15min bid for 3 months.
Fever
38 C or higher. temps >41 are rarely infectious and mostly CNS. if <3 months, must do bacterial disease work up though most often it’s viral. viruses are seasonal (RSV/flu in winter, enterovirus in summer/fall). bacteremia can be occult. more common causes in 3-36months are otitis media, pneumonia, URIs, enteritis, UTIs, osteomyelitis, meningitis. Fever without focus: fever with no known fever etiology after careful h&p. 30% from 1-36months have no local s/s infection. children <2 years greatest risk for unsuspected occult bacteremia.
Fever H&P
duration/degree of fever, associated s/s, review of known exposures, recent vaccination, PMH of malignancy/splenectomy/shunt/indwelling catheter/immunologic disorders/reccurent bacterial infections/serious infections; Neo history of complications/abx/surgeries/hyperbilirubinemia; chronic illness; current medications; immunization history. careful assess for fever, bulging anterior fontanelle, respiratory system changes, lethargy/CNS issues, skin infection or rashes, skin perfusion, turgor.
Fever diagnostics
if <1month or <3 years old but toxic appearing, admit to hospital for septic w/u and abx. negative, low risk ambulatory w/u: CBC, ESR, CRP, catheterized UA, stool if diarrhea, CXR if cough, and appropriate cultures. viral testing on seasonality. HSV and CSF and skin site cultures if infant is <42 days, vesicular skin lesions, abnormal CSF, or seizures. Differentials: URI, lower RTI, GI disease, musculoskeletal infections, UTI, occult bactermia.
Fever management
High risk (febrile <1 month, toxic appearing child, 1-3months with temp >38.6 or chronic illness and unreliable caretakers, <3months, gestational age <37 weeks, hx preemie, abx in last week, 3-36months with temp >39 and lab results showing high risk): immediate hospitalization and work up. <36months appearing well with temp 39+, WBC >15000, not vaccinated with Him and pneumococcal should have empiric abx. Low risk (1-3months non toxic no evident tissue infection with low risk labs, 3-6months with temp 38-39 not appearing ill, 3-36months with fever >39 non toxic and previously healthy with non-focal bacterial infection and + rapid flu test, 3-36months mildly ill with temp 39-40 and low risk labs and is immunized): outpatient management with rocephin, close follow up
f/u indicated
change in or new rash, duskiness, cyanosis/mottling, coolness of extremities, poor feeding/vomiting, irritability, cries with positional changes, difficulty in comforting or arousing, seizure activity, bulging anterior fontanelle.
Fever of unknown origin
fever >38.3 for most days for 3 weeks + without etiology, despite 3 weeks outpatient visits and extensive studies, and no etiology after 1 week eval in hospital or outpatient. recommended ID consult. often atypical presentations of common disorders, notably infections or rheumatologic/connective tissue diseases. EBV, cat scratch, UTI, osteomyelitis in spine/pelvis. fever >6months in granulomatosis or autoimmune disease. if <6 years, infections more likely. >6, likely auto inflammatory or autoimmune.
FUO management
fatigue of reconditioning in adolescents with high pressure and expectations, vague complaints etc. assess exam carefully, can send: CBC, ESR, CRP, procalcitonin, cultures, UA, Mantoux skin test, x-rays as indicated, liver chemistries, BMA, echo, scans. differentials: infection, collagen-vascular disease, malignancies, drug fever, nosocomial, HIV associated, DI, hyperthyroid, inflammatory bowel, hematoma, anhidrotic ectodermal dysplasia, munchausen syndrome. ID consult if systemic illness of failure to thrive, very young, extreme parental anxiety, or extensive w/u planned. otherwise follow frequently, test as needed. avoid empiric use of abx.
