Missed Infectious Disease Qs

1. A PPD should be done to confirm exposure before starting isoniazid therapy. For health-care workers a positive PPD is defined by induration greater than 10mm. For close contacts a positive PPD is defined by induration greater than 5mm.
2. First line prophylaxis for Traveler’s diarrhea is Quinolones such as Ciprofloxacin or Norfloxacin.
3. Giardia causes decreased fat absorption, leading to greasy foul-smelling stools.
4. A biopsy is the best first step in the management of leukoplakia.
1. It is a diagnosis of exclusion and a biopsy is the best way to rule out other possibilities such as Candidia, malignancy, and lichen planus. Hairy leukoplakia is a similar oral lesion found in immunocompromised patients, such as AIDS victims, due to an opportunistic EBV infection. While this patient may be HIV-positive or immunocompromised, it is more important to diagnose the chief complaint first
5. Ceftazidime (or cefepime) is a monotherapy of choice because it covers Pseudomonas. Vancomycin should be added if there is evidence of cellulitis or a catheter infection (B and D). Catheters don’t need to be removed immediately unless there is evidence of infection
6. Treatment of septic arthritis should be started with positive Gram stain results; do not wait for the culture to return.
1. Any swollen painful joint should be aspirated.
2. Septic arthritis is most commonly caused by Staphylococcus aureus. Salmonella septic arthritis is specific to sickle cell anemia, although staph is still the most common in sickle cell patients. Other causes include Neisseria gonorrhea, Streptococcus, Lyme disease, and pseudomonas.
3. Aspiration with polarizing microscopic exam is useful for crystal-induced arthritis, but gonococcus is most likely here due to the sexual history and other symptoms.
7. Patients on aminoglycosides for greater than 2 weeks are at risk for developing ototoxicity, especially with co-administration of loop diuretics.
1. Acute tubular necrosis leading to renal failure is a potential life-threatening effect of aminoglycoside therapy.
2. BUN and creatinine levels should be monitored in patients receiving treatment with aminoglycoside antibiotics, given their nephrotoxic potential
8. Esophagitis secondary to infection with Herpes Simplex Virus (HSV). These lesions are typically well circumscribed and have a “volcano” (deep and small) appearance, as opposed to esophagitis caused by CMV, which tend to be much larger, shallow ulcers.
1. the correct therapy would be oral acyclovir because of the nature of the ulcers.
2. Suspect CMV esophagitis in patients presenting with the triad of substernal burning with odynophagia, oral ulcerations and the presence of intracellular inclusions.
3. Suspect candida esophagitis in HIV patients with CD4 counts below 50 who present with odynophagia. Remember that there is an important difference in terminology for swallowing disorders. Dysphagia refers to difficulty swallowing wheras odynophagia refers to painful swallowing.
4. Esophagogastroduodenoscopy (EGD) is the most effective study to diagnose esophagitis.
5. Patients diagnosed with HIV esophagitis should receive treatment with oral fluconazole initially.
6. if presented with a vignette with an HIV-infected person with a CD4 count less than 50, initially treat for candidal esophagitis with oral fluconazole. If the patient can’t tolerate oral fluconazole due to pain then IV fluconazole may be used instead. If the patient does not improve, suspect another etiology and proceed with esophagoscopy with cytology, get a biopsy and initiate appropriate therapy pending on the results of the study. If CMV esophagitis is discovered, initiate treatment with oral ganciclovir. If HSV is discovered, treat with oral acyclovir.

CD4 <50: Lymphoma, CMV retinitis and esophagitis, Mycobacterium avium complex (MAC)

CD4 <100: Candida esophagitis, Cryptococcal meningitis, Cerebral toxoplasmosis

CD4 <200: Pneumocystis carinii (PCP), AIDS dementia

CD4 <500: Bacterial pneumonia, Tuberculosis, Kaposi’s sarcoma, Herpes zoster

9. Amoxicillin/clavulanate and second-generation cephalosporins are recommended for the prophylactic treatment of penetrating cat bites.
10. lymphogranuloma venereum (LGV) is a sexually transmitted chlamydial infection characterized by painful inguinal lymphadenopathy, fistulas and granulomas.
1. Characteristic findings include swollen painful inguinal lymph nodes with fistulas, strictures and granulomatous inflammation. Purulent discharge from the lymph node suggests a fistula. The painful lymphadenopathy usually occurs after a painless genital ulcer disappears. The organism is Chlamydia trachomatis types L1-L4.
11. Doxycycline is a tetracycline used for the treatment of Pasteurella multocida and other bacteria spread by cat and dog bites. It is the alternative to PCN and sulfa when there is an allergy. Fluroquinolones are not recommended in younger children due to the risk of tendon rupture and other adverse side effects, unless the injury is severe and/or several other treatment options have failed.
12. Although Streptococcus pneumoniae is the leading cause of bacterial pneumonia in all nursing home patients, individuals suffering from neurological impairment are particularly susceptible to pneumonia caused by anaerobic pathogens.
13. Early bacterial sepsis can manifest as respiratory alkalosis.
1. Patients who present with respiratory alkalosis should receive a CBC to screen for a leukocytosis and/or left shift to help determine if early sepsis is present.
2. Respiratory alkalosis occurs secondary to hyperventilation, which leads to hypocapnia (decreased PaCO2 levels)
14. Corynebacterium diphtheriae is characterized as a non-encapsulated, non-motile, gram-positive bacillus.
15. Chancroid is a sexually transmitted infectious disease characterized by painful ulcers, bubo formation, and painful inguinal lymphadenopathy. It is caused by Haemophilus ducreyi. Remember the mnemonic “ You DO cry with ducreyi."
1. Calymmatobacterium granulomatis is the causative organism of the sexually transmitted disease called granuloma inguinale. Patients with this condition present with large ulcerated lesions on the genitalia which are described as “beefy red” with friable granulation tissue. Unlike chancroid lesions, lesions of granuloma inguinale are painless and tissue analysis reveals characteristic Donovan bodies.
16. PPD Interpretation:

Results of > 5 mm and < 10 mm are positive in the following groups:

1. HIV-positive persons

2. Recent contacts of active TB patients

3. Persons with radiographic findings suggestive of old TB

4. Patients with organ transplantation and other severely immunocompromised states

Results of > 10 mm and < 15 mm are positive in the following groups:

1. Recent immigrants from high-prevalence countries

2. Intravenous drug users

3. Residents of high-risk congregate settings (e.g., prisons, nursing homes, shelters, hospitals)...this includes us (medical student/resident population)!

4. Mycobacteriology personal working in laboratory settings

5. Patients with high-risk conditions such as diabetes, leukemia, renal failure, and malnutrition

6. Children less than 4 years of age

Results of > 15 mm are positive in the following group:

1. EVERYONE

17. Immune Hypersensitivities:
1. Anaphylactic/Atopic (type I), Cytotoxic/antibody mediated (type II), Immune complex (type III), Delayed/cell mediated (type IV). Disease associated are:
2. Type I: anaphylaxis, allergic rhinitis (hay fever).
3. Type II: hemolytic anemia, ITP, erythroblastosis fetalis, rheumatic fever, Goodpasture syndrome, bullous pemphigoid, Graves disease, myasthenia gravis.
4. Type III: SLE, rheumatoid arthritis, polyarteritis nodosum, poststreptococcal glomerulonephritis, serum sickness, arthus reaction, hypersensitivity pneumonitis.
5. Type IV: type 1 diabetes mellitus, multiple sclerosis, Guillain-Barré syndrome, Hashimoto thyroiditis, graft-versus-host disease, PPD, contact dermatitis.