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Step Up To Medicine > Infectious Diseases > Flashcards

Infectious Diseases Flashcards

1
Q

What is syphilis?

A

It is caused by Treponema pallidum spirochetes transmitted by directed sexual contact with infectious lesions

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2
Q

What is the first stage of syphilis?

A
  1. Primary:
    • Characterized by chancre, which is an indurated, painless ulcer with a clean base that appears 4-6 weeks after exposure.
    • This lesion is highly infectious
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3
Q

What is the second stage of syphilis?

A
  1. Secondary:
    • Characterized by a maculopapular rash commonly on palms and soles
    • Develop 4-8 weeks after the chancre has healed
    • Patients are highly contagious during this stage
    • Condylomata lata: broad-based, wart-like, smooth, white papular erosions, painless, located in the anogenital region, intertriginous folds, and on oral mucosa
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4
Q

What is the third stage of syphilis?

A
  1. Latent:
    • Presence of positive serologic test results in the absence of signs and symptoms
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5
Q

What is the forth stage of syphilis?

A
  1. Tertiary:
    • Occurs years after the development of primary infection
    • Characterized by cardiovascular syphilis, neurosyphilis, and gummas (subcutaneous granulomas)
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6
Q

How do patients with syphilis commonly presents?

A
  1. Genital lesion
  2. Inguinal lymphadenopathy
  3. Maculopapular rash of secondary syphilis
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7
Q

How is syphilis diagnosed?

A
  1. Dark-field microscopy (definitive diagnosis)
  2. Serologic tests:
    • RPR, VDRL (nontreponemal): ideal for screening
    • FTA-ABS, MHA-TP (treponemal): confirmation to the above test
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8
Q

How is syphilis managed?

A
  1. Benzathine penicillin g, one dose IM. Effective in early syphilis
  2. Benzathine penicillin g, three dose IM, once per week. Given if patient is in late latent stage
  3. Repeat VDRL every 3 months to ensure or monitor response to treatment.
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9
Q

What is meningitis?

A

Inflammation of the meningeal membranes that envelop the brain and spinal cord.

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10
Q

What is aseptic meningitis?

A

Referred to nonbacterial infection such as enterovirus, HSV, parasites and fungi.

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11
Q

What are the common causes of bacterial meningitis according age groups?

A
  • Neonates: Group B streptococci, E.coli, Listeria monocytogenes
  • > 3 months - 50 years: S.pneumonia, H.influenzae, N.meningitidis
  • Adults >50 years: S.pneumoniae, N.meningitidis, L.monocytogenes, gram-negative bacilli
  • Immunocompromised: L.monocytogenes, gram-negative bacilli, S.pneumoniae
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12
Q

How does bacterial meningitis present?

A

Characteristic triad includes:
1. Fever
2. Nuchal rigidity
3. Changes in mental status

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13
Q

How is meningitis diagnosed?

A
  1. CT scan of the head if focal neurological symptoms are present or space-occupying lesion is suspected
  2. Lumbar puncture to examine CSF for cell count, protein, glucose, gram stain, culture and cryptococcal antigen or india ink
  3. Blood cultures before starting antibiotics
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14
Q

What are contraindications for lumbar puncture?

A
  1. Focal neurological deficit
  2. Altered mental status
  3. Immunocompromised
  4. Space occupying lesion
  5. Seizures
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15
Q

What are the CSF findings of bacterial meningitis?

A
  1. WBC count: >1000 cells/mm2
  2. WBC differential: Mostly PMNs
  3. Glucose: low
  4. Protein: high (100-500 mg/dL)
  5. Opening pressure: >200
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16
Q

What are CSF findings of aseptic meningitis?

A
  1. WBC count: <1000 cells/mm2
  2. WBC differential: Mostly lymphocytes and monocytes
  3. Glucose: normal (50-75 mg/dL)
  4. Protein: moderate elevation (24-200 mg/dL)
  5. Opening pressure: >200
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17
Q

What are the CSF findings in TB meningitis?

A
  1. WBC count: 100-1000 cells/mm2
  2. WBC differential: Mostly monocytes
  3. Glucose: low
  4. Protein: high (100-500 mg/dL)
  5. Opening pressure: >200
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18
Q

How is meningitis managed?

A
  1. Bacterial:
    • Infants: cefotaxime + ampicillin + vancomycin
    • > 3 months - 50 years: Ceftriaxone or cefotaxime + vancomycin
    • > 50 years: Ceftriaxone or cefotaxime + ampicillin + vancomycin
    • Immunocompromised: Ceftazidime + ampicillin + vancomycin
  2. Steroids if S.pneumoniae is suspected to prevent cerebral edema
  3. Vaccination
  4. Prophylaxis for all close contact of patient with meningococcus, rifampin or ceftriaxone is given
  5. For aseptic meningitis only supportive therapy only
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19
Q

What is tuberculosis?

A

A bacterial infection caused by Mycobacterium tuberculosis that typically affects the lungs. Primary infection is often initially asymptomatic, and bacteria remain dormant in the body until reactivation occurs in the case of immunodeficiency. Active disease classically manifests with fever, weight loss, night sweats, and a productive cough.

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20
Q

What is the pathophysiology of TB?

A
  1. Primary TB: bacilli are inhaled and deposited into the lung, surviving organisms multiply and disseminate. After resolution of primary infection the organism remain dormant within the granulomas
  2. Secondary TB: reactivation occurs when the host’s immunity is weakened
  3. Extrapulmonary TB: when immunity is impaired and not able to contain the bacteria in primary or secondary stage
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21
Q

What are the radio graphic findings in primary TB?

A
  • Ghon complex: calcified primary focus with an associated lymph node
  • Ranke complex: when Ghon complex undergoes fibrosis and calcification
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22
Q

How is TB diagnosed?

A
  1. CXR: diagnostic for active TB
    • Primary TB: middle or lower lobe infiltrates and cavitation
    • Secondary TB: apical zone infiltrates and cavitation
  2. Sputum acid-fast testing of 3 morning sputum specimens
  3. Tuberculin skin test (PPD test): screening test not diagnostic for active TB
    • Patient with no risk factors with induration >15 mm is positive
    • High risk population with induration >10 mm is positive
    • Patient with HIV, steroid users, organ transplant recipients, close contacts of those with active TB, or radiological evidence of primary TB with induration >5 mm is positive
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23
Q

How is TB managed?

A
  1. If PPD is positive and CXR is negative so active disease is ruled out patient is given isoniazid for 9 months
  2. If active disease: isoniazid, rifampin, pyrazindamid, and ethambutol or streptomycin for 2 months followed by isoniazid and rifampin for 4 months.
  3. Isoniazid should be given with pyridoxine (vitamin B6) to prevent sideroblastic anemia.
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24
Q

What are the side effects TB drugs?

A
  1. Rifampin: harmless orange body secretion, decrease sulfonylurea concentration
  2. Pyrazinamide: hyperuricemia, contraindicated in pregnancy
  3. Ethambutol: red-green eye blindness
  4. Streptomycin: ototoxicity, nephrotoxicity, contraindicated in pregnancy
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25
Q

What is infectious mononucleosis?

A

A highly contagious acute condition caused by the Epstein-Barr virus (EBV). IM spreads via bodily secretions, especially saliva (kissing, sharing food)

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26
Q

How does infectious mononucleosis present?

A

Fever, fatigue, sore throat, lymphadenopathy (posterior cervical), pharyngeal erythema and/or exudate, splenomegaly, maculopapular rash after ampicillin use, hepatomegaly, palatal petechiae, periorbital edema.

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27
Q

How is infectious mononucleosis diagnosed?

A
  1. Lab abnormalities seen: lymphocytosis, elevated aminotransferases
  2. Monospot test
  3. Peripheral blood smear shows atypical lymphocytes
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28
Q

What is the management plan for infectious mononucleosis?

A
  1. Rest, fluids
  2. Avoid contact sport for 3-4 weeks from onset of symptoms to prevent splenic rupture
  3. Short course of steroids in case of airway compromise
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29
Q

What is Lyme disease?

A

A vector-borne illness caused by spirochete Borrelia burgorferi transmitted by ticks.

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30
Q

What are the clinical features of Lyme disease?

A
  1. Stage 1: early localized infection, characterized by erythema migrans which is a well-demarcated target-shaped lesion.
  2. Stage 2: early disseminated infection, characterized by intermittent flu-like symptoms, headaches, neck stiffness, fever, fatigue, malaise, musculoskeletal pain.
  3. Stage 3: late persistent infection, months to years after initial infection
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31
Q

How is Lyme disease diagnosed?

A
  1. Clinically
  2. Confirmed by serologic studies such as serum IgM and IgG antibodies and western blot
32
Q

What is the management plan for Lyme disease?

A
  1. Oral doxycycline, amoxicillin + cefuroxime, or erythromycin
    • If confined to skin then antibiotics are given for 10 days
    • If spread beyond skin then antibiotics are given for 20-30 days
33
Q

What are the causes of lower urinary tract infection?

A
  1. E.coli (most common cause)
  2. Staphylococcus saprophyticus (mainly in young sexually active female)
  3. Enterococcus
  4. Klebsiella
  5. Proteus spp.
  6. Pseudomonas
  7. Enterobacter
  8. Yeast (candida spp.)
34
Q

What are the clinical features of lower urinary tract infection?

A

Dysuria, frequency, urgency, suprapubic tenderness, gross hematuria, fever is characteristically ABSENT.

35
Q

How is lower UTI diagnosed?

A
  1. Dipstick urinalysis
  2. Urinalysis: clean-catch midstream specimen, >1 organism per oil-immersion field and >10 leukocytes/uL is abnormal
  3. Urine gram stain: >10^5 organisms/mL represents significant bacteriuria
  4. Urine culture: confirms the diagnosis
    • Obtain if patient >65 year, diabetic, recurrent UTI, presence of symptoms for 7 or more day, use of diaphragm
    • 10^2 to 10^4 CFU/mL are adequate for diagnosis if clinical symptoms are present
36
Q

What is asymptomatic bacteriuria?

A

Two successive positive cultures (>10^5 CFU/mL) must be present. Treated only in pregnancy or before urologic surgery.

37
Q

How is lower UTI treated?

A
  1. Acute uncomplicated cystitis (nonpregnant women): oral TMP/SMX for 3 days, nitrofurantoin for 5-7 days or Fosfomycin single dose. In men same treatment, but for 7 days.
  2. Pregnant women with UTI: ampicillin, amoxicillin, or oral cephalosporins for 7-10 days
38
Q

What are the causes of pyelonephritis?

A
  1. E.coli (most frequent cause)
  2. Gram-negative bacteria: proteus, Klebsiella, Enterobacter, and pseudomonas spp.
  3. Gram-positive bacteria: Enterococcus fecalis and S.aureus
39
Q

What are the clinical features of pyelonephritis?

A

Fever, chills, flank pain, symptoms of cystitis maybe present, appear more ill than patients with cystitis, costovertebral angle tenderness, abdominal tenderness may be present on examination

40
Q

How is pyelonephritis diagnosed?

A
  1. Urinalysis: look for pyuria, bacteriuria, and leukocyte casts
  2. Urine cultures: obtained in all patients with suspected pyelonephritis
  3. Blood cultures: obtained in ill-appearing patients and all hospitalized patients
  4. CBC
41
Q

How is pyelonephritis managed?

A
  1. Uncomplicated pyelonephritis:
    • Treated in outpatient
    • If gram-negative rod: TMP/SMX or a fluoroquinolone for 10-14 days
    • If gram-positive cocci: amoxicillin
    • A single dose of ceftriaxone or gentamicin is given initially before oral therapy
  2. If patient is severely ill, can’t tolerate oral therapy, elderly, pregnant, significant comorbidities, or if urosepsis is suspected:
    • Hospitalize and give IV fluids
    • Ampicillin + gentamicin o ciprofloxacin
    • If blood culture is negative continue IV therapy until patient is Afebrile for 24 hours then continue oral antibiotics for 14-21 days
    • If blood culture is positive continue IV therapy for 2-3 weeks
42
Q

What is toxic shock syndrome?

A

Most commonly associated with menstruating women and tampon use, caused by an enterotoxin of S.aureus or exotoxin of group A streptococcus. Diagnosis is primarily clinical.

43
Q

How does toxic shock syndrome present?

A
  1. Abrupt onset
  2. Flu-like symptoms, diffuse macular erythematous rash, strawberry tongue, warm skin, hypotension, nausea, vomiting and diarrhea.
  3. There must be at least 3 organ systems involved such as: GI, renal, hematologic, musculoskeletal, CNS
  4. During convalescent phase of illness, the rash usually desquamates over the palms and soles
44
Q

How is toxic shock syndrome managed?

A
  1. Hemodynamic stabilization
  2. Source of infection should be removed immediately
  3. Antistaphylococcal therapy such as naficillin, oxacillin, or vancomycin
45
Q

What is osteomyelitis?

A

Inflammatory destruction of bone due to infection

46
Q

What are the most common organisms causing osteomyelitis?

A
  1. S.aureus
  2. Coagulase-negative staphylococci
47
Q

How do patients with osteomyelitis present?

A

Pain over the involved area of bone (most common finding)

48
Q

How is osteomyelitis diagnosed?

A
  1. Needle aspiration of infected bone is the most direct and accurate means of diagnosis.
  2. MRI is the most effective imaging study
  3. ESR and CRP are useful in monitoring response to therapy
49
Q

What is the management plan for osteomyelitis?

A
  1. Give IV antibiotics for extended periods (4-6 weeks). It is initiated only after the microbial etiology is narrowed based o data from cultures
  2. Surgical debridement of infected necrotic bone is an important aspect of treatment
50
Q

What is pneumonia?

A

Acute respiratory illness characterized by inflammation of the lung alveoli from an infection resulting in a fluid accumulating in the alveoli.

51
Q

What are the 2 types of pneumonia?

A
  1. Community-acquired pneumonia: can be typical or atypical, most common pathogen is streptococcus pneumoniae
  2. Nosocomial pneumonia: occurs during hospitalization after first 72 hours, most common bacterial pathogens are gram-negative rods (E.coli, pseudomonas) and staphylococcus aureus
52
Q

What are the common agents that cause typical pneumonia?

A
  1. S.pneumonia (cause rust-colored sputum)
  2. H.influenzae (common in patients with COPD or smokers)
  3. Aerobic gram-negative rods such as Klebsiella (common in alcoholics and those with suppressed mentation, producing current-jelly sputum)
  4. S.aureus
53
Q

How does typical CAP present?

A

Sudden chill followed by fever, pleuritic pain and productive cough

54
Q

What are the common agents that cause atypical pneumonia?

A
  1. Mycoplasma pneumoniae
  2. Chlamydia pneumonia
  3. Chlamydia psittaci
  4. Coxiella burnetii
  5. Legionella spp. (common in immune suppressed patients)
55
Q

How does atypical CAP present?

A

Often begins with a sore throat and headache followed by a nonproductive cough and dyspnea. Pulse-temperature dissociation which is a normal pulse in the setting of high fever is suggestive of atypical CAP.

56
Q

How is pneumonia diagnosed?

A
  1. PA and lateral CXR is required to confirm the diagnosis
  2. Pretreatment expectorated sputum for Gram stain and culture
  3. Urinary antigen assay for Legionella in selected patients
  4. Pretreatment blood culture from different sites.
  5. Laboratory tests

2-5 not required if treated as outpatient

57
Q

How to decide whether to hospitalize a patient with pneumonia or not?

A

Using CURB-65 score:
- Confusion
- Urea >7 mmol/L or BUN >20
- Respiratory rate >30/min
- Blood pressure (systolic <90 mmHg or diastolic <60 mmHg)
- Age >65 years

Score >2 requires hospitalization, >4 requires ICU admission

58
Q

What is the management of pneumonia?

A
  1. Outpatient:
    • <60 years: macrolides or doxycycline, fluoroquinolones are alternatives
    • > 60 years: fluoroquinolone + macrolides or amoxicillin-clavulanate
    • treatment is continued for 5 days, do not stop until patient is Afebrile for 48 hours
  2. Inpatient:
    • Fluoroquinolone alone or a 3rd generation cephalosporin + macrolide
59
Q

What is the management of hospital-acquired pneumonia?

A

Ceftazidime or cefepime, imipenem, or piperacillin/tazobactam

60
Q

What lab tests are ordered if a patient presents with bloody diarrhea?

A
  1. CBC
  2. Stool sample for presence of fecal leukocytes
  3. 3 stool sample if presence of ova and parasites are suspected
  4. Bacterial stool culture
  5. Stool sample for C.difficile toxin if suspected according to history
  6. Colonoscopy/flexible sigmoidoscopy: for chronic diarrhea
  7. CT scan helpful if IBD or diverticulosis is suspected
61
Q

How is acute diarrhea managed?

A
  1. Rehydrate and monitor electrolytes
  2. Treat underlying cause
  3. 5-day course of ciprofloxacin in patients who have moderate to severe disease:
    • High fever, bloody stools, or severe diarrhea: quinolones are appropriate
    • If C.difficile infection use metronidazole
62
Q

What are the causes of viral hepatitis?

A
  • Hepatitis A: transmitted by fecal-oral route, often affects travelers
  • Hepatitis B: transmitted sexually or parenterally
  • Hepatitis C: transmitted parenterally
  • Hepatitis D: requires the outer envelop of hepatitis B surface antigen
  • Hepatitis E: transmitted by fecal-oral route
63
Q

How is hepatitis diagnosed?

A
  1. Serology
  2. PCR: to detect viral RNA to diagnose HCV
  3. LFT: ALT is typically elevated more than AST
64
Q

What are the hepatitis serology for viral causes?

A
  1. Hepatitis A:
    • Anti-HAV IgM denotes acute infection
    • Anti-HAV IgG suggests immunity and persists for life
  2. Hepatitis B:
    • HBsAg: present in acute or chronic infection
    • HBeAg: reflects active viral replication, presence indicates infectivity
    • Anti-HBs: present after vaccination or after clearance of HBsAg, indicates immunity
    • Anti-HBc: appears during window period where HBsAg is disappearing and anti-HBsAg hasn’t appeared
  3. Hepatitis C:
    • Anti-HCV: key marker of infection, but absence doesn’t rule out infection
    • HCV RNA measured by PCR: detectable 1-2 weeks after infection
  4. Hepatitis D:
    • Anti-HDV: presence indicates HDV superinfection
  5. Hepatitis E:
    • Anti-HEV IgM: suggests infection
    • Anti-HEV IgG: begins to rise during the same period of IgM, but persists for life
    • HEV RNA: checked in serum or stool to confirm infection
65
Q

What is the complication of chronic hepatitis?

A

Risk of developing Hepatocellular carcinoma, so do liver US and check AFP levels every 6 months

66
Q

How is HIV diagnosed?

A
  1. PCR RNA viral load test
  2. ELISA
  3. Western blot test: specific test used to confirm a positive result on an ELISA test
67
Q

How is AIDS diagnosed?

A

A patient with HIV has AIDS if he or she has a CD4+ T-cell count below 200, a CD4+ T-cell percentage of total lymphocytes below 14%, or an AIDS-defining illness.

68
Q

How is HIV managed?

A

2 nucleoside reverse transcriptase inhibitors and either of the following:
- A nonnucleoside reverse transcriptase inhibitor (NNRTI)
- Protease inhibitor with a pharmacokinetic booster (ritonavir, cobicistat)

69
Q

What is the prophylaxis treatment for opportunistic infection?

A
  1. PCP: occurs when CD4 cell count is <200, TMP/SMX is the preferred agent
  2. TB: isoniazid + pyridoxine if PPD is positive
  3. MAC: start prophylaxis when CD4 cell count is <100 with clarithromycin and azithromycin
  4. Toxoplasmosis: start prophylaxis when CD4 cell count is <100 with TMP/SMX
70
Q

What is the most common bacterial STD?

A

Chlamydia trachomatis

71
Q

How does chlamydia present?

A
  1. Many are asymptomatic
  2. Men: dysuria, purulent urethral discharge, scrotal pain and swelling, and fever
  3. Women: purulent urethral discharge, intermenstrual or postcoital bleeding, and dysuria
72
Q

How is chlamydia managed?

A
  1. One oral dose of azithromycin or oral doxycycline for 7 days
  2. Treat all sexual partners
73
Q

What are the two types of herpes simplex virus?

A
  1. HSV-1: typically associated with lesions of the oropharynx, so commonly transmitted through non sexual contact
  2. HSV-2: associated with lesions of the genitalia, so commonly transmitted through sexual contact

BUT both can cause either genitalia and oral lesions

74
Q

How does HSV present?

A

HSV-1: groups of vesicles on patches of erythematous skin
HSV-2: painful genital vesicles or pustules, inguinal lymphadenopathy and vaginal and/or urethral discharge.

75
Q

What is chancroid?

A

A sexually transmitted disease caused by Haemophilus ducreyi. Presents with painful genital ulcer that can be deep with ragged borders and with a purulent base an unilateral tender inguinal lymphadenopathy.

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