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Step 2 Secrets > Infectious Diseases > Flashcards

Infectious Diseases Flashcards

1
Q

Urinary tract infections: which bugs are associated? what type of empiric antibiotic should be used?

A
  • E. coli

- Trimethoprim-sulfamethoxazole, nitrofurantoin, amoxicillin, quinolones

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2
Q

Bronchitis: which bugs are associated? what type of empiric antibiotic should be used?

A
  • Virus, H. influenzae, Moraxella spp.

- Usually no benefit from antibiotics, may consider macrolides or doxycycline

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3
Q

Classic pneumonia: which bugs are associated? what type of empiric antibiotic should be used?

A
  • Strep. pneumoniae, H. influenzae

- 3rd generation cephalosporin, azithromycin

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4
Q

Atypical pneumonia: which bugs are associated? what type of empiric antibiotic should be used?

A
  • Mycoplasma, Chlamydia spp.

- Macrolide, doxycycline

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5
Q

Osteomyelitis: which bugs are associated? what type of empiric antibiotic should be used?

A
  • Staph. aureus, Salmonella spp.

- Oxacillin, cefazolin, vancomycin

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6
Q

Cellulitis: which bugs are associated? what type of empiric antibiotic should be used?

A
  • Streptococci, staphylococci

- Cephalexin, dicloxacillin, clindamycin or trimethoprim-sulfamethoxazole if MRSA is suspected

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7
Q

Meningitis (neonate): which bugs are associated? what type of empiric antibiotic should be used?

A
  • Streptococci, E. coli, Listeria spp.

- Ampicillin + aminoglycoside, expanded spectrum 3rd generation cephalosporin (cefotaxime)

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8
Q

Meningitis (child/adult): which bugs are associated? what type of empiric antibiotic should be used?

A
  • Strep. pneumoniae, Neisseria meningitidis (in child with no immunization history, H. influenzae is most likely)
  • Cefotaxime or ceftriaxone + vancomycin
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9
Q

Endocarditis: which bugs are associated? what type of empiric antibiotic should be used?

A
  • Staphylococci, streptococci

- Antistaphylococcal penicillin (e.g. dicloxacillin, methicillin) or vancomycin + aminoglycoside

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10
Q

Sepsis: which bugs are associated? what type of empiric antibiotic should be used?

A
  • Gram-negative organisms, streptococci, staphylococci

- 3rd generation penicillin/cephalosporin + aminoglycoside, or imipenem

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11
Q

Septic arthritis: which bugs are associated? what type of empiric antibiotic should be used?

A
  • Staph. aureau = vancomycin
  • Gram-negative bacilli = ceftazidime or ceftriaxone
  • Gonococci = ceftriaxone, ciprofloxacin, or spectinomycin
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12
Q

What is the choice of antibiotic for Streptococcus A or B?

A
  • Penicillin, cefazolin

- Erythromycin

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13
Q

What is the choice of antibiotic for Strep. pneumoniae?

A
  • 3rd-generation cephalosporin + vancomycin

- Fluoroquinolone

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14
Q

What is the choice of antibiotic for Enterococcus?

A
  • Penicillin or ampicillin + aminoglycoside

- Vancomycin + aminoglycoside

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15
Q

What is the choice of antibiotic for Staph. aureus?

A
  • Anti-staphylococcus penicillin (e.g. methcillin)

- Vancomycin (MRSA)

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16
Q

What is the choice of antibiotic for Gonococcus?

A
  • Ceftriaxone or cefixime

- Spectinomycin

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17
Q

What is the choice of antibiotic for Meningococcus?

A
  • Cefotaxime or ceftriaxone

- Chloramphenicol or penicillin G if susceptible

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18
Q

What is the choice of antibiotic for Haemophilus?

A
  • 2nd or 3rd generation cephalosporin

- Ampicillin

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19
Q

What is the choice of antibiotic for Pseudomonas?

A
  • Antipseudomonal penicillin (ticarcillin, piperacillin) +/- beta lactamase inhibitor (clavulanate, tazobactam)
  • Ceftazidime, cefepime, aztreonam, imipenem, ciprofloxacin
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20
Q

What is the choice of antibiotic for Bacteroides?

A
  • Metronidazole

- Clindamycin

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21
Q

What is the choice of antibiotic for Mycoplasma?

A
  • Erythromycin, azithromycin

- Doxycycline

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22
Q

What is the choice of antibiotic for Treponema pallidum?

A
  • Penicillin

- Doxycycline

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23
Q

What is the choice of antibiotic for Chlamydia?

A
  • Doxycycline, azithromycin

- Erythromycin, ofloxacin

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24
Q

What is the choice of antibiotic for Lyme disease (Borrelia spp.)?

A
  • Cefuroxime, doxycycline, amoxicillin

- Erythromycin

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25
Q

What does a blue/purple Gram stain most likely represent?

A

Gram-positive organism

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26
Q

What does a red Gram stain most likely represent?

A

Gram-negative organism

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27
Q

What do Gram-positive cocci in chains on Gram stain most likely represent?

A

Streptococci

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28
Q

What do Gram-positive cocci in clusters on Gram stain most likely represent?

A

Staphylococci

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29
Q

What do Gram-positive cocci in pairs (diplococci) on Gram stain most likely represent?

A

Streptococcus pneumoniae

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30
Q

What do Gram-negative coccobacilli (small rods) on Gram stain most likely represent?

A

Haemophilus spp.

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31
Q

What do Gram-negative diplococci on Gram stain most likely represent?

A

Neisseria spp. or Moraxella spp.

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32
Q

What do plump Gram-negative rods with thick capsules (mucoid appearance) on Gram stain most likely represent?

A

Klebsiella spp.

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33
Q

What do Gram-positive rods that form spores on Gram stain most likely represent?

A

Clostridum spp., Bacillus spp.

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34
Q

What do pseudohyphae on Gram stain most likely represent?

A

Candida spp.

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35
Q

What do acid-fast organisms on Gram stain most likely represent?

A

Mycobacterium (usually M. tuberculosis), Nocardia spp.

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36
Q

What do Gram-positive organisms with sulfur granules on Gram stain most likely represent?

A

Actinomyces spp. (pelvic inflammatory disease in IUD users; rare cause of neck mass/cervical adenitis)

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37
Q

What do silver-staining organisms on Gram stain most likely represent?

A

Pneumocystis jirovecii, cat-scratch disease

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38
Q

What does a positive India ink preparation (thick capsule) on Gram stain most likely represent?

A

Cryptococcus neoformans

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39
Q

What do spirochetes on Gram stain most likely represent?

A
  • Treponema spp., Leptospira spp. (both seen on dark-field microscopy)
  • Borrelia spp. (seen on regular light microscopy)
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40
Q

What is the gold standard for diagnosis of pneumonia?

A

Sputum culture. Try to get it before starting antibiotics, though many treat empirically without culture. Get blood cultures, too, because bacteremia is common with pneumonia.

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41
Q

What is the most common cause of pneumonia? How does it classically present?

A

Streptococcus pneumoniae. Look for rapid onset of shaking chills after 1-2 days of URI symptoms, followed by fever, pleurisy, and productive cough (yellowish-green or rust-colored from blood), esp. in older adults.
CXR shows lobar consolidation and WBC is high with large % of neutrophils.

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42
Q

How do you treat pneumonia?

A
  • Macrolide (e.g. azithromycin, clarithromycin)
  • Doxycycline
  • 3rd generation cephalosporin with macrolide or doxycycline
  • Fluoroquinolone with atypical coverage (e.g. levofloxacin, moxifloxacin)
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43
Q

What is the best prevention against S. pneumoniae?

A

Vaccination. Give to all children and adults over 65, splenectomized patients, patients with sickle-cell disease (who have autosplenectomy) or splenic dysfunction, immunocompromised patients (HIV, malignancy, organ transplant), and all patients with chronic disease (DM, cardiac, pulmonary, renal, or liver disease)

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44
Q

How do you recognize and treat Haemophilus influenzae pneumonia?

A

Now uncommon in children due to vaccination, but still important cause of pneumonia in elderly and those with underlying lung disease (e.g. COPD). Often resembles pneumococcal pnuemonica clinically, but look for Gram-negative coccobacilli on sputum Gram stain.
Treat with amoxicillin or 3rd generation cephalosporin.

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45
Q

Describe the hallmarks of Staph. aureus pneumonia.

A

Tends to cause hospital-acquired pneumonia and pneumonia in patients with cystic fibrosis (along with Pseudomonas spp.), IV drug abusers, and patients with chronic granulomatous disease (look for recurrent lung abscesses). Empyema and lung abscesses are relatively common with S. aureus pneumonia.

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46
Q

In what clinical scenario do you tend to see gram-negative pneumonias?

A

Pseudomonas infection is classically associated with cystic fibrosis, Klebsiella with alcoholics and homeless people (classic description of currant jelly sputum), and enteric Gram-negative organisms (e.g. E. coli) with aspiration, neutropenia, and hospital-acquired pneumonia.
Treat empirically with antipseudomonal penicillin (e.g. ticarcillin, piperacillin) with or without beta lactamase inhibitors (e.g. clavulanate, tazobactam) OR ceftazidime or ciprofloxacin.

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47
Q

How do you recognize Mycoplasma pneumonia?

A

Most common in adolescents and young adults. Long prodrome with gradual worsening of malaise, headaches, dry, nonproductive cough, and sore throat; fevers tend to be low-grade.
CXR with patchy, diffuse bronchopneumonia and looks terrible, although patient often does not feel that bad. Look for positive cold-agglutinin Ab titers, which may cause hemolysis or anemia.
Treat with macrolide (e.g. azithromycin) or broad-spectrum fluoroquinolone (e.g. levofloxacin or moxifloxacin).

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48
Q

How do you recognize chlamydial pneumonia?

A

Presents similarly to Mycoplasma pneumonia but has negative cold-agglutinin Ab titers.
Treat with macrolide (e.g. azithromycin) or broad-spectrum fluoroquinolone (e.g. levofloxacin or moxifloxacin).

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49
Q

In what setting do you see Pneumocystis jirovecii (PCP) and CMV pneumonia?

A

HIV-positive patients with CD4 counts less than 200 and other severely immunosuppressed patients.
PCP may require bronchoalveolar lavage for diagnosis. Can be seen with silver stains and usually causes bilateral interstitial lung infiltrates. Treat with trimethoprim-sulfamethoxazole or pentamidine.
CMV is characterized by intracellular inclusion bodies. Treat with ganciclovir or foscarnet.

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50
Q

What is the best time to treat PCP?

A

Before it happens! PCP is acquired when CD4 count is below 200. At that point you should institute prophylaxis in an HIV-positive patient with trimethoprim-sulfamethoxazole. Alternatives include atovaquone, dapsone, or pentamidine.

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51
Q

What is the most common organism associated with this scenario: Stuck with thorn or gardening?

A

Sporothrix schenckii

Treat with oral potassium iodide or ketoconazole

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52
Q

What is the most common organism associated with this scenario: Aplastic crisis in sickle cell disease?

A

Parvovirus B19

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53
Q

What is the most common organism associated with this scenario: Sepsis after splenectomy?

A

S. pneumoniae, H. influenzae, N. meningitidis (encapsulated organisms)

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54
Q

What is the most common organism associated with this scenario: Pneumonia in the Southwest (California, Arizona)?

A

Coccidioides immitis

Treat with itraconazole or fluconazole, amphotericin

55
Q

What is the most common organism associated with this scenario: Pneumonia after cave exploring or exposure to bird droppings in Ohio and Mississippi River valleys?

A

Histoplasma capsulatum

56
Q

What is the most common organism associated with this scenario: Pneumonia after exposure to a parrot or exotic bird?

A

Chlamydia psittaci

57
Q

What is the most common organism associated with this scenario: Fungus ball/hemoptysis after TB or cavitary lung disease?

A

Aspergillus spp.

Treat with voriconazole

58
Q

What is the most common organism associated with this scenario: Pneumonia in a patient with silicosis?

A

TB

59
Q

What is the most common organism associated with this scenario: Diarrhea after hiking/drinking from a stream?

A

Giardia lamblia

Stool cysts; treat with metronidazole

60
Q

What is the most common organism associated with this scenario: Pregnant woman with cats?

A

Toxoplasma gondii

Treat with spiramycin

61
Q

What is the most common organism associated with this scenario: B12 deficiency and abdominal symptoms?

A

Diphyllobothrium latum

62
Q

What is the most common organism associated with this scenario: Seizures with ring-enhancing brain lesion on CT?

A 
Taenia solium (cysticercosis) or toxoplasmosis
Treat neurocysticercosis with albendazole or praziquantel, usually with steroids. Consider anticonvulsants.
63
Q

What is the most common organism associated with this scenario: Squamous cell bladder cancer in Middle East or Africa?

A

Schistosoma haematobium

64
Q

What is the most common organism associated with this scenario: Worm infection in children?

A

Enterobius spp.
Positive tape test, perianal itching
Treat with mebendazole or albendazole

65
Q

What is the most common organism associated with this scenario: Fever, muscle pain, eosinophilia, and periorbital edema after eating raw meat?

A

Trichinella spiralis (trichinosis)

66
Q

What is the most common organism associated with this scenario: Gastroenteritis in young children?

A

Rotavirus, Norwalk virus

67
Q

What is the most common organism associated with this scenario: Food poisoning after eating reheated rice?

A

Bacillus cereus

Infection is usually self-limited

68
Q

What is the most common organism associated with this scenario: Food poisoning after eating raw seafood?

A

Vibrio parahaemolyticus

69
Q

What is the most common organism associated with this scenario: Diarrhea after travel to Mexico?

A

E. coli (Montezuma revenge)

Treat with ciprofloxacin

70
Q

What is the most common organism associated with this scenario: Diarrhea after antibiotics?

A

Clostridium difficile

Use metronidazole or vancomycin

71
Q

What is the most common organism associated with this scenario: Baby paralyzed after eating honey?

A

Clostridium botulinum

Toxin blocks ACh release

72
Q

What is the most common organism associated with this scenario: Genital lesions in children in the absence of sexual abuse or activity?

A

Molluscum contagiosum

73
Q

What is the most common organism associated with this scenario: Cellulitis after dog/cat bite?

A

Pasteurella multocida

Treat animal bite wound with prophylactic amoxicillin-clavulanate

74
Q

What is the most common organism associated with this scenario: Slaughterhouse worker with fever?

A

Brucellosis

75
Q

What is the most common organism associated with this scenario: Pneumonia after being in a hotel or near air conditioner or water tower?

A

Legionella pneumophila

Treat with azithromycin or levofloxacin

76
Q

What is the most common organism associated with this scenario: Burn wound infection with blue/green color?

A

Pseudomonas spp.

S. aureus is also common but lacks color

77
Q

How is syphilis diagnosed?

A

Screen with rapid plasma reagin (RPR) or Venereal Disease Research Lab (VDRL) test. Confirm positive test with fluorescent treponemal Ab (FTA-ABS) or microhemagglutination (MHA-TP) test because false positive occur, classically in patients with SLE. Once syphilis is treated, RPR and VDRL tests become negative, whereas the FTA-ABS and MHA-TP tests often remain positive for life. You can also scrape the base of a genital chancre or condyloma lata and look for spirochetes on dark-field microscopy.

78
Q

Which group of patients should always be screened for syphilis?

A

Pregnant women. Early treatment can prevent birth defects.

79
Q

How is syphilis treated?

A

With penicillin. Use doxycycline for penicillin-allergic patients.

80
Q

Describe the 3 stages of syphilis.

A
  • Primary: painless chancre that resolves on its own within 8 weeks
  • Secondary: 6 weeks to 18 months after infection; condyloma lata, maculopapular rash (involves palms and soles), lymphadenopathy
  • Tertiary: years after initial infection; gummas (granulomas in many organs), neurologic symptoms (e.g. Argyll-Robertson pupils, dementia, paresis, tabes dorsalis, Charcot joints), thoracic aortic aneurysms
81
Q

How do you recognize measles (rubeola) infection in a child?

A

Lack of immunization? Koplik’s spots (tiny white spots on buccal mucosa) seen 3 days after high fever, cough, runny nose, and conjunctivitis with or without photophobia. On next day, maculopapular rash begins on head and neck, spreads downward to cover trunk (cephalocaudal progression). Treat supportively.

82
Q

Describe the complications of measles.

A

Giant-cell pneumonia, esp. in very young and immunocompromised, otitis media, encephalitis acute or late (subacute sclerosing panencephalitis usually occurs years later)

83
Q

Why is rubella (German measles) an important disease?

A

Infection in pregnant mothers can cause severe birth defects in the fetus. Screen and immunize all women of reproductive age without evidence of rubella Ab before pregnancy to avoid this. The vaccine is contraindicated in pregnancy women.

84
Q

How do you recognize a rubella (German measles) infection in children? What are the complications?

A

Milder than measles. Low-grade fever, malaise, tender swelling of suboccipital and postauricular nodes; arthralgias are common. After 2-3 day prodrome, faint maculopapular rash appears on face and neck and spreads to trunk (cephalocaudal progression), just like measles.
Complications include encephalitis and otitis media.

85
Q

How do you recognize erythema infectiosum (fifth disease) in children? What causes it?

A

Classic “slapped cheek” rash accompanied by mild constitutional symptoms (low fever, malaise). One day later, maculopapular rash appears on arms, legs, and trunk.
Caused by parvovirus B19, same virus that causes aplastic crisis in sickle cell disease.

86
Q

How do you recognize chickenpox? What causes it?

A

Discrete macules (usually on trunk) turn into papules, which turn into vesicles that rupture and crust over. These changes occur in 1 day. Because lesions appear in successive crops, rash will be in different stages of progression in different areas. The cause is the varicella virus.

87
Q

How can you make a definitive diagnosis of chickenpox? At what point is a patient with chickenpox no longer infectious?

A

Tzanck smear of tissue from the base of a vesicle shows multinucleated giant cells.
Infectivity ceases only when the last lesion crusts over.

88
Q

What are the complications of chickenpox?

A

Infection of lesions with streptococci or staphylococci, which causes erysipelas, cellulitis, and/or sepsis. Also pneumonia (esp. very young children, adults, and immunocompromised), encephalitis, and Reye syndrome (do NOT give aspirin to child with fever). Can reactivate years later to cause herpes zoster (shingles), rash that develops in dermatomal distribution, often with preceding pain and paraesthesias. Child that has not been immunized or exposed can catch the disease from someone with shingles.

89
Q

Describe the treatment and prophylaxis for chickenpox.

A

No treatment is usually needed except supportive care. Acyclovir is used in severe cases. Routine vaccination is now recommended for all children. Varicella zoster IG is available for prophylaxis in patients with debilitating illness (e.g. leukemia, AIDS) if you see them within 4 days of exposure and for newborns of mothers with chickenpox. IVIG can be given if VariZIG is not available.

90
Q

What is scarlet fever? What causes it? How is it recognized and treated?

A

Febrile illness with rash caused by certain Strep spp. (those that produce erythrogenic toxin). Look for history of untreated streptococcal pharyngitis, which is followed by sandpaper-like rash on abdomen and trunk with circumoral pallor and strawberry tongue. Rash desquamates once fever subsides. Oral penicillin V is treatment of choice to prevent rheumatic fever. Alternatives include amoxicillin, cephalosporins, macrolides, or clindamycin.

91
Q

What are the diagnostic criteria for Kawasaki disease (mucocutaneous lymph node syndrome)?

A

Usually patients younger than 5 y/o.
- Fever for more than 5 days (mandatory)
- Bilateral conjunctival injection
- Changes in lips, tongue, or oral mucosa (e.g. strawberry tongue, fissuring, injection)
- Changes in extremities (e.g. skin desquamation, edema, erythema)
- Polymorphous truncal rash, which usually begins 1 day after fever starts
- Cervical lymphadenopathy
Also look for arthralgias or arthritis

92
Q

What is the most feared complication of Kawasaki disease? How do you prevent it?

A

Coronary artery aneurysms, congestive heart failure, arrhythmias, myocarditis, MI
If Kawasaki disease suspected, give aspirin and IVIG. Follow child with echocardiography to detect heart involvement.

93
Q

Describe the classic findings of Epstein-Barr virus infection (infectious mononucleosis).

A

Fatigue, fever, pharyngitis, cervical lymphadenopathy in young adult. Look for *splenomegaly (splenic rupture possible, avoid contact sports and heavy lifting), *hepatomegaly, *atypical lymphocytes (bizarre forms that resemble leukemia) with lymphocytosis, anemia, or thrombocytopenia, *positive serology (heterophile Abs - e.g. Monospot test - or specific EBV Abs (viral capsid antigen, EPV nuclear antigens).

94
Q

What is an important differential diagnosis of EBV infection?

A

Acute HIV infection, which can cause mononucleosis-type syndrome

95
Q

What is the association with EBV and cancer?

A

Associated with nasopharyngeal cancer, African Burkitt lymphoma, and post-transplant lymphoproliferative disorder

96
Q

Describe the classical vignette for Rocky Mountain Spotter Fever. What causes it? What is the treatment?

A

History of tick bite (esp. in patient on East Coast), one week before high fevers/chills, severe headache, and prostration or severe malaise. Rash appears 4 days later on palms and wrists and soles and ankles and spreads rapidly to trunk and face. Patients look quite ill. Caused by Rickettsia rickettsii. Treat with doxycycline; chloramphenicol is second choice.

97
Q

How do you recognize and treat the rash of impetigo? What causes it?

A

Caused by Streptococcus and Staphylococcus spp. Look for history of skin break. Rash starts as thin-walled vesicles that rupture and form yellowish crusts. Skin is described as “weeping”. Look for history of sick contacts. Treat with dicloxacillin, cephalexin, or clindamycin. Topical mupirocin may be also be used.

98
Q

Describe the two clinical types of endocarditis. What are the causative bugs?

A
  • Acute (fulminant) typically affects normal heart valves, most commonly caused by Staph. aureus
  • Subacute has an insidious onset and typically affects previously damaged or mechanical valves, most commonly caused by Strep. viridans (also Staph. epidermidis, Strep. bovis, Strep. faecalis)
  • Suspect colon cancer if Strep. bovis turns up
99
Q

How is endocarditis diagnosed and treated?

A

Diagnosis is generally made by blood cultures. Empiric treatment with broad-spectrum IV antibiotics until sensitivity results are known. 3rd generation penicillin or cephalosporin + aminoglycoside is a reasonable choice.

100
Q

What are the classic signs and symptoms of endocarditis?

A

General signs of infection (e.g. fever, tachycardia, malaise) plus new-onset heart murmur, embolic phenomena (e.g. stroke), *Osler nodes (painful nodules on tips of fingers), *Janeway lesions (nontender, erythematous lesions on palms and soles), *Roth spots (round retinal hemorrhages with white centers), septic shock (more likely with acute than subacute disease)

101
Q

What elements of the history point to endocarditis?

A
  • IV drug abusers (usually have R-sided lesions)
  • Patients with abnormal heart valves (e.g. prosthetic, rheumatic valvular disease, congenital heart defects - VSD or tetralogy of Fallot)
  • Postoperative patients (esp. after GI, GU, or dental surgery)
102
Q

What are the recommendations for endocarditis prophylaxis?

A

Cardiac conditions for which prophylaxis with DENTAL procedures is indicated include prosthetic cardiac valve, previous infectious endocarditis, congenital heart disease, and cardiac transplant recipients who develop valvulopathy.
- Single dose before procedure: amoxicillin is preferred oral therapy (cephalexin, clindamycin, azithromycin, or clarithromycin may be used for penicillin allergies). Ampicillin, cefazolin, ceftriaxone, or clindamycin may be used for patients unable to take oral meds.
No longer recommended for GU or GI procedures.

103
Q

What is the classic age group for meningitis?

A

Neonates - 75% of cases occur in children younger than 2 years

104
Q

Describe the physical findings of meningitis.

A

Often do not have classical findings (Kernig and Brudzinski signs). Look for lethargy, hyper- or hypothermia, poor muscle tone, bulging fontanelle, vomiting, photophobia, altered consciousness, and signs of generalized sepsis (e.g. hypotension, jaundice, respiratory distress). Seizures may be seen but simple febrile seizures are common for patients between 5 months and 6 years of age with a fever greater than 102 F.

105
Q

What should you do if you suspect meningitis?

A

In the absence of trauma, do a lumbar puncture immediately and begin broad-spectrum antibiotics and IV fluids. Do NOT wait for culture or other results to start antibiotics.

106
Q

What is the most common neurologic sequela of meningitis?

A

Hearing loss. All pediatric and many adult patients need formal hearing evaluation afterwards. Vision testing is also recommended. Other sequelae include mental retardation, motor deficits/paresis, epilepsy, and learning/behavioral disorders.

107
Q

What are the common viral (aseptic) causes of meningitis in children?

A

Mumps and measles in children who are not immunized. Watch for neonatal herpes encephalitis (HSV-2) if mother has genital lesions or herpes simplex virus at time of delivery.
Other children and adults can develop HSV-1 encephalitis, which classically affect the temporal lobes on a head CT or MRI. Give IV acyclovir.

108
Q

What types of bacterial meningitis require antibiotic prophylaxis in contacts?

A
  • N. meningitidis: rifampin, ciprofloxacin, ceftriaxone, or azithromycin
  • H. influenzae: rifampin
109
Q

What are the “big three” respiratory infections in patients younger than 5 years?

A

Croup, epiglottitis, and respiratory syncytial virus infection (bronchiolitis)

110
Q

How do you recognize croup (acute laryngotracheitis)? Describe the cause and treatment.

A

Look for a child 1-2 years of age, usually in the fall or winter. 50-75% of cases are due to parainfluenza virus; others are due to influenza virus.
Disease begins with symptoms of URI, 1-2 days later patient develops “barking” cough, hoarseness, and inspiratory stridor. The “steeple sign” (subglottic narrowing of trachea) is classic on frontal x-ray.
Treat supportively with a mist tent, humidified oxygen, and racemic epinephrine.

111
Q

How do you recognize epiglottitis? Describe the cause and treatment.

A

Usually children 2-5 years old. Main cause is H. influenzae type B (others include Staph. aureus, S. pyogenes, and S. pneumoniae).
Little or no prodrome, rapid progression to high fever, toxic appearance, drooling, and respiratory distress with no coughing. “Thumb sign” (swollen, enlarged epiglottis) is classical on lateral x-rays. Do NOT examine the throat or irritate the child in any way - may precipitate airway obstruction.
First step is to establish an airway (intubation and, if needed, tracheostomy).
Treat with combination of oxacillin or cefazolin or clindamycin or vancomycin + cefotaxime or ceftriaxone.

112
Q

Describe the classical clinical vignette for bronchiolitis. What is the cause? How is it treated?

A

Generally children 0-18 months, usually in fall or winter. >75% caused by respiratory syncytial virus (RSV); others include parainfluenza and influenza viruses.
First develop viral URI symptoms, followed 1-2 days later by rapid respirations, intercostal retractions, and expiratory wheezing. May have crackles on auscultation. Diffuse hyperinflation is classic on CXR, look for flattened diaphragms.
Treat supportively. Use ribavirin in patients with severe symptoms or at high risk (e.g. cyanosis or other chronic health problems).

113
Q

What “old-school” pediatric infection causes pseudomembranes and myocarditis?

A

Diptheria (Corynebacterium diphtheriae) causes grayish pseudomembranes (necrotic epithelium and inflammatory exudate) on pharynx, tonsils, and uvula as well as myocarditis.
Treat with antitoxin and either penicillin or erythromycin.

114
Q

What “old-school” pediatric infection causes whooping cough?

A

Pertussis (Bordetella pertussis) is associated with severe paroxysmal coughing and a high-pitched whooping inspiratory noise, particularly in children (esp. those under 1 year of age).
Treat with azithromycin or erythromycin.

115
Q

In what clinical scenario does rabies occur in the U.S.? Describe the classic physical findings.

A

Due to bites from bats, skunks, raccoons, or foxes; rarely from dogs. Incubation period is usually around 1-2 months. Classic findings are hydrophobia (fear of water due to painful swallowing) and CNS signs (e.g. paralysis).

116
Q

What should do after a patient is bitten by an animal?

A
  1. Treat local wound, cleanse thoroughly with oap. Do NOT cauterize or suture the wound. Amoxicillin-clavulanate is often given for cellulitis prophylaxis.
  2. Observe the animal. If possible, capture and observe the dog or cat to see if it develops rabies. If a wild animal is caught, it should be killed and the brain tissue examined for rabies.
  3. If wild animal escapes or has rabies, give rabies IG and vaccinate patient. In cases of dog or cat bite, do NOT give prophylaxis or vaccine unless the animal acted strangely or bit the patient without provocation and rabies is prevalent in the area. Do NOT give prophylaxis for rabbit or small rodent bites.
117
Q

What are the two main infections caused by Strep. pyogenes (group A strep)? What are the common sequelae?

A

Pharyngitis and skin infections. Sequelae include rheumatic fever, scarlet fever, and poststreptococcal glomerulonephritis.

118
Q

How does streptococcal pharyngitis present? How do you diagnose and treat it?

A

Sore throat with fever, tonsillar exudate, enlarged tender cervical lymph nodes, and leukocytosis.
Positive strep throat culture confirms diagnosis. Elevated titers of antistreptolysin O (ASO) and anti-DNase Ab can be used for retrospective diagnosis.
Treat pharyngitis with penicillin, amoxicillin, cephalosporin, macrolide, or clindamycin to avoid rheumatic fever and scarlet fever.

119
Q

What are the major and minor Jones criteria for rheumatic fever? Why is rheumatic fever less common today?

A

Major criteria (5): migratory polyarthritis, carditis, chorea, erythema marginatum, and subcutaneous nodules
Minor criteria: elevated ESR, CRP, WBC, ASO titer, prolonged PR interval on EKG, arthralgia
Diagnosis requires a history of strep pharyngitis + at least 1 major criterion.
Treatment of strep pharyngitis with antibiotics markedly reduced the incidence of rheumatic fever.
*Give all patients affected by rheumatic fever endocarditis prophylaxis before surgical procedures.

120
Q

How do you recognize poststreptococcal glomerulonephritis? How is it treated?

A

Occurs most commonly after strep skin infection, but may also occur after pharyngitis. Usually in children who presents with a history of infection 1-3 weeks earlier and now have abrupt onset hematuria, proteinuria (mild, not in nephrotic range), RBC casts, hypertension, edema (esp. periorbital), and elevated BUN/Cr.
Treat supportively. Control BP, use diuretics for severe edema.
Treatment of strep infections does not reduce the incidence of glomerulonephritis.

121
Q

Distinguish between impetigo and erysipelas.

A

Both are superficial skin infections due to streptococi or S. aureus and often occur after a break in the skin.
Impetigo - changes first from maculopapules to vesicopustules and bullae and then to honey-colored, crusted lesions; staph > strep; contagious (watch for sick contacts)
Erysipelas - red, shiny, swollen, tender; may have vesicles and bullae, fever and lymphadenopathy
Treat both empirically with dicloxacillin, cephalexin, or clindamycin, though erysipelas may require parenteral therapy with a cephalosporin if systemic symptoms (e.g. fever, chills) are present.

122
Q

What organisms typically cause cellulitis? What special circumstances should make you think of atypical causes?

A

Streptococci and staphylococci cause most cases.
Think Pseudomonas spp. with burns or severe trauma, Pasteurella multocida after cat or dog bites (treat with ampicillin), Vibrio vulnificus in fishermen or others exposed to salt water (treat with tetracycline).
Diabetic patients with foot ulcers tend to have polymicrobial infections and need powerful broad-spectrum antibiotic coverage.

123
Q

Describe the physical findings of cellulitis. Define necrotizing fasciitis. How is it treated?

A

Skin is red, hot, and frequently tender. Looks like erysipelas but involves deeper subcutaneous tissue. Treat with anti-staph antibiotics to cover strep and staph.
Necrotizing fasciitis is the progression of cellulitis to necrosis and gangrene. Watch for crepitus and signs of systemic toxicity (e.g. tachycardia, fever, and hypotension). Often multiple organisms are involved (aerobes and anaerobes). Treat with IV fluids, I&D/debridement, and broad-spectrum antibiotics (e.g. ampicillin + clindamycin or metronidazole).

124
Q

What is the most common cause of endometritis (puerperal fever)? How do you recognize and treat it?

A

Infection of the endometrial lining, usually presenting as postpartum fever.
Hallmark is uterine tenderness, and most common cause is Strep. spp. Treat with clindamycin + gentamicin after getting local cultures.

125
Q

What infection in neonates is caused by Strep. agalactiae (group B strep)?

A

Most common cause of neonatal meningitis or sepsis. Often part of normal vaginal flora and may be acquired from birth canal. GBS is penicillin-sensitive. Expectant mothers are cultures for GBS and if it is present around time of delivery, prophylactic penicillin or ampicillin is given to prevent meningitis in the newborn.

126
Q

Other than pneumonia, what infections does Strep. pneumoniae commonly cause?

A

Otitis media, meningitis, sinusitis, and spontaneous bacterial peritonitis.

127
Q

What are the main infections caused by S. aureus?

A

Skin and soft-tissue abscesses (esp. after breast-feeding or after furuncle), endocarditis (esp. in drug users), osteomyelitis (most common cause unless sickle cell disease is present), septic arthritis, food poisoning (via preformed toxin), toxic shock syndrome (via preformed toxin), scalded skin syndrome (via preformed toxin, affects younger children who present with impetigo then desquamate), impetigo, cellulitis, wound infections, pneumonia (often forms lung abscess or empyema), furuncles and carbuncles

128
Q

Who are the classic spreaders of nosocomial staphylococcus infections?

A

Health care workers who are chronic nasal carriers can cause nosocomial infections.

129
Q

What is the treatment of choice for staph infections?

A

Antistaphylococcal penicillin (e.g. methicillin, dicloxacillin). Use vancomycin, clindamycin, doxycycline, or trimethoprim-sulfamethoxazole if MRSA is suspected.

130
Q

TB: What is the treatment for an exposed adult with negative PPD skin test?

A

None

131
Q

TB: What is the treatment for an exposed child younger than 5 years old with negative PPD?

A

Isoniazid (INH) for 3 months, then repeat PPD

132
Q

TB: What is the prophylaxis for PPD conversion (negative to positive) but no active disease?

A

Isoniazid (INH) for 9 months

133
Q

TB: What is the treatment for active pulmonary disease/positive culture?

A

Isoniazid (INH) + rifampin + pyrazinamide + ethambutol for 2 months, then INH + rifampin for 4 months in most patients

134
Q

What vitamin supplementation could be considered for TB patients on isoniazid (INH)?

A

Vitamin B6 (pyridoxine) or watch for signs of deficiency, such as neuropathy, confusion, angular chilitis, or a seborrheic dermatitis-like rash

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