Infectious Disease Exam Review: Sepsis, STIs, and Microbiology

Exam format: number of questions and style

50-55 questions; evenly spread across all 6 weeks; case-based scenarios; microbiology and Gram stain throughout

How many sepsis questions are on the exam?

5+ (heaviest single topic)

Sepsis: step 1

Recognize sepsis

Sepsis: step 2

Draw cultures and lactate; blood cultures from 2 different sites BEFORE antibiotics

Sepsis: step 3

Broad-spectrum IV antibiotics as soon as possible

Sepsis: step 4 (fluid of choice)

IV fluids: Lactated Ringer's

Sepsis: BP still low after fluids

Norepinephrine

Sepsis: refractory shock

Add steroids

Sepsis source control: infected catheter

Remove it

Sepsis source control: abscess

Drain it

Most common organism causing Group A strep

Streptococcus pyogenes

Group A strep diagnosis

Throat culture or rapid strep test (looks for GAS)

Three complications of Group A strep

Scarlet fever; acute rheumatic fever; post-streptococcal glomerulonephritis

Acute rheumatic fever: onset

2-3 weeks after untreated strep pharyngitis

Acute rheumatic fever: most common joint finding

Arthritis of the large joints

Acute rheumatic fever: cardiac findings

Myocarditis and valvulitis

Acute rheumatic fever: neurologic finding

Sydenham chorea

Acute rheumatic fever: skin and systemic findings

Subcutaneous nodules and fever

C. diff, non-severe: treatment

Fidaxomicin (Dificid); preferred over vancomycin

C. diff, severe: treatment

Vancomycin

Signs of a very sick (severe) C. diff patient

Bloody stool, high WBC, kidney injury

Uncomplicated UTI presentation

Dysuria, NO discharge, no fever

Complicated UTI presentation and treatment

Pyelonephritis, flank pain; cipro or another fluoroquinolone

Most common cause of UTI

E. coli

Patient has discharge: UTI or STI?

STI, not UTI; think chlamydia and gonorrhea

Chlamydia/gonorrhea testing: why site-specific?

Urine alone misses oral and anal sites

Chlamydia/gonorrhea: treatment approach

Treat both when either is suspected

Why not wait on culture for chlamydia/gonorrhea?

Patient may not come back and may have other partners

Most common cause of bacterial meningitis

S. pneumoniae

Bacterial meningitis: antibiotics

May require up to 3 antibiotics; cover Listeria

Bacterial meningitis: steroid

Dexamethasone

Most common cause of skin abscess

S. aureus

Skin abscess: first-line management

Incision and drainage first

Skin abscess: when to give antibiotics

Only if the scenario is complicated

Bacterial pneumonia: initial regimen

Amoxicillin plus doxycycline, or azithromycin

Bacterial pneumonia: penicillin-allergic

Fluoroquinolone: levofloxacin (Levaquin)

Two urine antigen tests for pneumonia

S. pneumoniae urinary antigen; Legionella urinary antigen

Lyme disease: why is diagnosis challenging?

Window period before antibodies appear; once antibody-positive, can stay positive for life

Lyme disease: treat if rash present but serology negative?

Yes, treat if the rash is present even if serology is negative

Lyme disease: treatment

Doxycycline

Rocky Mountain spotted fever: severity

Can be fatal

RMSF classic rash

Blanching macules that become petechial; start at wrists, forearms, ankles; spread inward; involve palms and soles

RMSF: treatment

Doxycycline (same as Lyme and anaplasmosis)

Anaplasmosis: treatment

Doxycycline (same as Lyme and RMSF)

Tick-borne diseases treated with doxycycline

Lyme disease, Rocky Mountain spotted fever, anaplasmosis

TB treatment regimen

RIPE: Rifampin, Isoniazid, Pyrazinamide, Ethambutol

Mycobacteria: culture and growth characteristics

Special culture media, slow metabolism, slow to grow

Mycobacteria: stain

Acid-fast

MAC stands for

Mycobacterium avium-intracellulare

MAC: where can it appear?

In the lungs or disseminated throughout the body

MAC: always treat?

No; pulmonary MAC in particular may just be monitored

MAC prophylaxis

Azithromycin when CD4 < 50 (azithromycin is NOT part of RIPE)

Candida risk factors

Immunocompromised, steroids, cancer treatment, recent antibiotic use

Candida diagnosis

Clinical, in the office; can be cultured

Candida: thrush treatment

Clotrimazole

Candida: esophagitis treatment

PO fluconazole

Candida: severe or invasive treatment

IV antifungal

Galactomannan test detects

Aspergillus (serum or BAL)

Beta-D-glucan test detects

Broad fungal marker; not species-specific

Histoplasmosis: exposure

Bird and bat droppings

Coccidioidomycosis: nickname and region

Valley Fever; Southwest US

Blastomycosis: exposure and region

Moist soil; US and Canada

Cryptococcus gattii: region

Pacific Northwest

Fungal pneumonia patient who has been in an endemic region

Identify which endemic fungus matches the region

HSV: sites it can manifest

Fingers (whitlow) and lips (also genital)

HSV: latency and tropism

Mucoepithelial cells; latent in sensory ganglia (why recurrences return to the same spot)

HSV treatment (oral or genital)

Acyclovir or valacyclovir

VZV: first infection vs reactivation

First infection = chickenpox; reactivation = shingles

VZV treatment

Acyclovir or valacyclovir

EBV: antiviral treatment?

None; supportive care only

EBV: enlarged tonsils

Steroids can manage symptoms

EBV: diagnosis

Monospot (not reliable in young children) or serology (more complicated panel)

EBV: splenic complication

Enlarged spleen; get an ultrasound

EBV: oncogenic?

Yes

CMV treatment

IV ganciclovir, then oral valganciclovir (prodrug, pill form)

CMV diagnosis

Biopsy showing inclusion bodies; diagnosis is complicated

CMV disease means

Actively showing signs and symptoms

CMV mono vs EBV mono

CMV mono syndrome is different from EBV mono

CMV tropism

Epithelial cells, monocytes, lymphocytes (explains multi-organ disease)

COVID-19: asymptomatic or young and healthy

Supportive care

COVID-19: not hospitalized

Paxlovid (first line)

COVID-19: sicker or hospitalized

Remdesivir

Influenza: very sick patient

Oseltamivir (Tamiflu)

RSV: antiviral treatment?

None

RSV: prevention in high-risk young children

Monoclonal antibodies; consider age, time of year, past medical history

HIV-2: key features

Mainly West Africa; rare; spreads less easily; progresses to AIDS more slowly

Acute HIV presentation

Mono-like syndrome: fever, sore throat, rash; >80% had flu-like symptoms

Suspect acute HIV: which test shortens window period?

HIV PCR

Current HIV screening test

4th-generation combined antibody/antigen test

HIV tropism

CD4 receptor plus a co-receptor

AIDS definition

CD4 < 200

CD4 < 200 prophylaxis

Bactrim; prevents PCP and treats toxoplasmosis

CD4 < 50 prophylaxis

Azithromycin; prevents MAC

At what CD4 do you start HIV treatment?

Trick question: no threshold; if someone has HIV, you treat it

HIV treatment regimen structure

Always 3 drugs from 2 classes (one 2-drug regimen exists)

HIV: consequence of poor adherence

Resistance and loss of undetectable status

HIV: genotype timing

Run at baseline and to check for resistance

PrEP drugs

Truvada and Descovy

Backbone of most HIV regimens

Tenofovir plus emtricitabine

Descovy: tenofovir form and pros/cons

Tenofovir alafenamide (TAF); better for bones and kidneys; NOT protective for vaginal sex (poor tissue penetration, takes weeks)