Infectious Disease Flashcards
3 bugs most commonly responsible for community-acquired acute bacterial meningitis
Streptococcus pneumoniae > Neisseria meningitidis, Listeria monocytogenes
4 Sx of acute bacterial meningitis
severe headache, fever, altered mental status, and symptoms of meningeal irritation such as neck stiffness (if one of the last 3 are not present, ABM is excluded)
Bugs responsible for nosocomial acute bacterial meningitis
Gram-negative bacilli > Staphylococcus aureus, Streptococci and other staphylococci
DDx for fever, headache, and meningeal irritation (5)
Meningitis (ABM, Acute aseptic meningitis syndrome eg AVM)
Brain abscess
Cerebral and spinal epidural abscess
Septic intracranial thrombophlebitis
Infective endocarditis with cerebral embolization
HIV-assoc opportunistic diseases (14)
Pneumocystis pneumonia (PCP, caused by Pneumocystis jiroveci, formerly known as Pneumocystis carinii) - most serious; 50% occur in prev unDx HIV
Mycobacterium tuberculosis infection
Disseminated Mycobacterium avium complex (MAC) infection
Toxoplasma gondii infection
Recurrent Streptococcus pneumoniae infections
Cytomegalovirus (CMV)
Herpes simplex virus (HSV)
Varicella-zoster virus (VZV)
Cryptococcus neoformans infection
Histoplasma capsulatum infection
Coccidioides immitis infection
Candida albicans infection
Lymphoma
Kaposi sarcoma (associated with infection by HHV-8)
The clinical syndrome of AIDS is defined as:
HIV-infected individuals who either:
Have a CD4 count that falls below 200 cells/mm3 OR
Develop one of the so-called AIDS-defining illnesses
A given opportunistic infection tends to occur at specific degrees of immune suppression. ________ is used to quantify immune suppression.
The CD4 count
HIV lifestyle modifications (4 groups)
1 Sexual exposure: Latex condoms reduce exposure and prevent transmission. Avoid fecal-oral (cryptosporidiosis, amebiasis, hepatitis, and giardiasis).
2 Environmental exposure: Professions with increased risk: healthcare or work in shelters or correctional institutions (TB), child care (giardiasis, hepatitis, CMV), animal care (toxoplasmosis, campylobacteriosis, cryptosporidiosis), gardening (cryptosporidiosis, toxoplasmosis). Monitor pet exposure: cats (bartonellosis, toxoplasmosis), reptiles (salmonellosis), and fish (Mycobacterium marinum).
3 Food- and water-related exposures: Avoid raw or undercooked eggs, meat, seafood, and dairy products. Avoid drinking untreated water, as well as swimming in lakes and rivers. Boiling drinking water in areas with cryptosporidiosis.
4 Travel: Pay attn to risk of diarrheal illnesses (traveler’s diarrhea). Killed vaccines (rabies, diphtheria-tetanus) can be given as recommended for all travelers, but live vaccines (polio, typhoid) should be avoided, except measles vaccine.
HIV-specific DDx for the following Sx: Constitutional symptoms (fever, weight loss, fatigue) Visual changes, eye pain Headache, mental status changes Cough, shortness of breath Oral lesions Odynophagia, dysphagia Chronic diarrhea GU symptoms Skin lesions Enlarged lymph nodes
Constitutional symptoms (fever, weight loss, fatigue)—mycobacterial infection (tuberculosis [TB] and MAC), HIV wasting syndrome, lymphoma, Bartonella infection
Visual changes, eye pain—CMV retinitis, ophthalmic varicella-zoster
Headache, mental status changes—toxoplasma encephalitis, CNS lymphoma, cryptococcal meningitis, progressive multifocal leukoencephalopathy (JC virus)
Cough, shortness of breath—PCP, TB, recurrent bacterial pneumonia, influenza
Oral lesions—thrush, oral hairy leukoplakia, aphthous ulcers, HSV
Odynophagia, dysphagia—candidal esophagitis, CMV esophagitis, HSV esophagitis
Chronic diarrhea—cryptosporidiosis, isosporiasis
GU symptoms—recurrent HSV infection, syphilis, cervical cancer
Skin lesions—Kaposi sarcoma, molluscum contagiosum, Bartonella infection (bacillary angiomatosis), scabies
Enlarged lymph nodes—lymphoma, mycobacterial infection, HIV lymphadenopathy, Bartonella
Stages in HIV infection
Acute retroviral syndrome
Clinical latency (Progressive decrease in CD4 counts and increase in viral load) = 10 years
AIDS
Typical positive findings in newly Dx HIV pt (5)
Generalized lymphadenopathy Oral candidiasis Angular cheilitis Pigmented lesions (Kaposi sarcoma, bacillary angiomatosis) Fungal nail infections
Initial tests for evaluating a pt with newly Dx HIV
CD4 lymphocyte count
HIV RNA quantitation (viral load)
HIV resistance testing (genotyping)
CBC
Routine chemistries (electrolytes, creatinine, LFTs, lipid panel)
Chest radiograph
Titers of antibodies against cytomegalovirus, Toxoplasma gondii, hepatitis B, hepatitis C
Purified protein derivative (PPD) to test for tuberculosis exposure along with anergy panel
RPR or VDRL
Screen for glucose-6-phosphate dehydrogenase (G6PD) deficiency (in patients with appropriate racial or ethnic background because of commonly used HIV drugs that predispose to hemolysis)
Fasting lipid panel (because of metabolic disorders associated with antiviral therapy)
Papanicolaou smear for women
Testosterone level for men
The management of the asymptomatic HIV patient involves: (3)
1 characterizing and following the progression of infection (via CD4 counts and viral load)
2 preventing opportunistic diseases (prophylaxis and routine surveillance)
3 attempting to forestall immunologic decline by the administration of drugs that have activity against HIV itself (NRTIs, NNRTIs, PIs –> HAART)
When to initiate antiretroviral Tx in an HIV pt?
Treat all patients with a history of an AIDS-defining illness or asymptomatic patients with a CD4 count of <200 cells per mm3.
Recommendation for treatment of other patients is less standardized; many physicians offer treatment to asymptomatic patients with CD4 cell counts between 201 and 350 cells per mm3.
Potentially fatal “do-not-miss” diagnoses that present with fever and rash: (6)
Meningococcemia Bacterial sepsis (e.g., staphylococcal sepsis) Endocarditis Rocky Mountain spotted fever Gonococcemia Typhoid fever
Signs of severe systemic illness (e.g., hypotension, meningismus) along with fever and rash suggest a potentially life-threatening condition such as: (5)
meningococcemia, toxic shock, endocarditis, Rocky Mountain spotted fever, Kawasaki disease
Fever + urticarial rash DDx (7)
Allergy - also pretty much any other type of rash
Hepatitis (acute or chronic)
EBV
HIV (established infection) - also vesiculobullar
Adenovirus - also maculopapular
Enteroviral infection - also pretty much any other type of rash
Mycoplasma - also maculopapular
Type of rash for the following (1 each; present with fever): Endocarditis Typhoid Staph sepsis Vibrio vulnificus Strep infection Ehrlichiosis Rocky Mtn spotted fever Secondary syphilis Lyme disease Primary HIV infection Varicella-zoster Herpes simplex Erythema multiforme Lymphoma Kawasaki disease
Endocarditis - Petechaial/purpura (P) Typhoid - maculopapular (MP) Staph sepsis - vesicular/bullous (VB) Vibrio vulnificus VB Strep infection - erythematous (E) Ehrlichiosis E Rocky Mtn spotted fever P Secondary syphilis MP Lyme disease MP Primary HIV infection MP Varicella-zoster VB Herpes simplex VB Erythema multiforme MP Lymphoma E Kawasaki disease E
Classically, pneumonias present with signs of consolidation: (4)
Bronchial breath sounds
Egophony (“e” to “a” changes)
Dullness to percussion
Increased tactile fremitus
Physical findings (6) and lab findings (6) in patients with community-acquired pneumonia that are associated with increased morbidity and mortality include:
Tachypnea (respiratory rate ≥30)
Temperature 30 × 109/L, or absolute neutrophil count 50 mm Hg (FiO2 0.21)
Arterial pH <9 g per dL
Serum creatine greater than 1.2 mg per dL or BUN greater than 20 mg per dL
Certain unfavorable chest radiograph findings (e.g., multilobar consolidation, pulmonary effusion, cavity formation)
Noninfectious conditions that can mimic pneumonia include: (4)
Pulmonary embolus
CHF
Lung cancer
Inflammatory lung disease (e.g., Wegener granulomatosis, eosinophilic pneumonia)
CURB-65 model for pneumonia
Confusion
Blood urea nitrogen >20 mg/dL
Respiratory rate >30 breaths per minute
Blood pressure (systolic less than 90, diastolic 3 may require ICU care.
5 Bugs that cause pneumonia in an outpatient (previously healthy and no use of antimicrobials within the previous 3 months) and Tx
S. pneumoniae, M. pneumoniae, C. pneumoniae, H. influenzae, Respiratory viruses
Tx: Advanced-generation macrolide (e.g., azithromycin or clarithromycin), OR doxycycline
In the United States, STDs are most prevalent among young individuals of low socioeconomic class. The notable exception is ___________, which is more evenly distributed across the population.
Chlamydia trachomatis infection
Certain STD syndromes can mimic other conditions:
Urethritis: (2)
PID: (4)
Vulvovaginitis/cervicitis: (2)
Urethritis: Urinary tract infection, prostatitis
PID: Ectopic pregnancy, appendicitis, pyelonephritis, cystitis
Vulvovaginitis/cervicitis: Normal cyclical changes in vaginal secretions during menstrual cycle, dysfunctional uterine bleeding
What are primary and secondary syphilis?
Physical findings in secondary syphilis commonly include: (6)
Findings in tertiary syphilis (3)
Primary stage: painless, indurated ulcer (chancre) at the inoculation site. If untreated, approximately half the patients progress to a disseminated/secondary (hematogenous) stage, and the rest go directly to a stage of latent disease (serologic evidence of infection but no clinical manifestations). In the secondary stage, the organisms are widely dispersed throughout the body.
Physical findings in secondary syphilis commonly include:
Generalized maculopapular rash (characteristically involves palms and soles; Color Plate 10)
Mucous patches (silver gray erosions with an erythematous periphery that are generally painless)
Condylomata (wartlike enlarged papules that are moist and pink to gray white; these lesions are highly infectious)
Generalized nontender lymphadenopathy
The primary chancre (present in approximately 15% of cases)
Nonspecific constitutional symptoms (fever, sore throat, malaise, and headache)
Late/tertiary syphilis is marked by end-organ damage, involving: Nervous system (general paresis; tabes dorsalis; paresthesias; loss of position, pain, and temperature sensation) Cardiovascular system (syphilitic aortitis) Gumma formation (granulomas with central necrosis, most commonly involving the skin, skeletal system, mouth, larynx, liver, and stomach, but all organs have been reported to be involved)
The laboratory diagnosis of syphilis can be performed by: (3)
Dark-field microscopy of lesions (to demonstrate the presence of spirochetes)
Direct immunofluorescence microscopy
Serology (both nontreponemal tests such as rapid plasma reagin [RPR] and Venereal Disease Research Laboratory [VDRL], which are used for screening, and direct treponemal tests such as immunofluorescence and hemagglutination to detect antibodies specific for T. pallidum)
The VDRL can be used to monitor response to therapy.
What is PID and what are the sequelae? (3)
PID = infection of the upper female reproductive tract (endometrium, fallopian tubes, and pelvic peritoneum); can lead to a variety of sequelae:
Ectopic pregnancy
Tubal infertility
Chronic pelvic pain
Lab finding in urethritis (male) due to gonococcal infection
Gram-negative diplococci (N. gonorrhoeae) inside PMNs
The majority (>90%) of UTIs are caused by ________ (aerobic/anaerobic) gram-_______ bacteria.
Approximately 80% of community-acquired and 50% of nosocomial UTIs are caused by __________, with most of the remainder caused by gram-_________ bacteria such as _________ (4).
Another etiologic agent in patients with an indwelling urinary catheter is ___________.
aerobic, negative
Escherichia coli; negative; Enterobacter, Klebsiella, Proteus, and Pseudomonas
yeast (most often Candida species)