Infectious Disease Pearls

Author:	Reed.Simons
ID:	25325
Filename:	Infectious Disease Pearls
Update:	2010-08-27 08:02:34

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Can herpes zoster recur in immunocompetent persons?
-YES, zoster can recur in immunocompetent persons, even soon after the initial episode

What medications are most commonly implicated as the cause of Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis?
The most commonly implicated medications are antibiotics, including penicillins and sulfonamides, with the latter implicated more often than cephalosporins

When evaluating a patient in the ED with meningitis, the clinician must make treatment decisions based, at least in part, on the evaluation of the CSF. When the rest of the clinical picture strongly suggests viral meningitis, recognize that the finding of a preponderance of ? is not incongruous with the diagnosis.
<answer>
-Polymorphonuclear cells (PMNs)

Typically, aseptic meningitis is associated with mononuclear cell preponderance.  However, this may often be preceded by a transient predominance of PMN’s in the CSF for up to 48 hours, and perhaps longer.  One report of a pediatric population found that a majority of children with aseptic meningitis (57%) had a predominance of PMN’s during enteroviral season and that this persisted in many patients beyond 48 hours (2).

References:(1) Graham TP. Myth: Cerebrospinal fluid analysis can differentiate bacterial meningitis from aseptic meningitis CJEM 2003;5(5):348-9.(2) Negrini B, et. al. Cerebrospinal Fluid Findings in Aseptic Versus Bacterial Meningitis PEDIATRICS 2000;105: 316-9.(3) Zunt JR Cerebrospinal fluid testing for the diagnosis of central nervous system infection Neurol Clin 1999;17: 675-89.</answer>

The prevalence of HIV infection among incarcerated persons in the US is four times greater than the prevalence among persons in community settings.  What is the prevalence of each?
The prevalence of HIV infection among incarcerated persons in the US is 1.5%; among persons in community settings it is 0.4% (MMWR, June 25, 2010).

Most important risk factor for death from West Nile Virus:
Advanced age is the most important risk factor for death from WNV.

Typical CSF analysis of patients with West Nile Virus and neurologic symptoms:
<answer>
CSF analysis of patients with neurologic disease typically demonstrates an aseptic meningitis-like pattern: elevated protein, near-normal glucose, and pleocytosis with a predominance of lymphocytes (rather than neutrophils).

Ninety percent of patients with meningoencephalitis will have IgM antibody in their CSF within 8 days of symptom onset.</answer>

How do you diagnose West Nile Virus?
Diagnosis of WNV is made by serology, by detection of IgM antibody in either serum or CSF.

True or false:  Most people with West Nile Virus remain asymptomatic.
True: About 20% to 30% of infected patients experience an acute, febrile, influenza-like illness.

With the advent of vaccination for Haemophilus influenzae type B, acute epiglottitis presentations to EDs are now more commonly reported among adults than among children.  Do adults require emergent airway interventions as frequently as children?
In a literature review, just 15–33% of acute adult epiglottitis required emergent airway interventions (JEM, In Press, Online 7/23/10).

Why are the atypical pneumonia pathogens referred to as atypical?
They are "atypical" in the sense that they are not detectable on Gram stain or cultivatable on standard bacteriologic media (Clin Inf Dis; 44:S27).

What type of virus is West Nile Virus?
Mosquito born RNA virus from the family Flavivirus

What percentage of individuals develop an acute, febrile, influenza-like illness?
Only 20-30%

What percentage of patients with WNV develop neurologic disease?
<1%

Postinfectious glomerulonephritis is induced by infection with specific strains of group A Beta-hemolytic streptococci.  Does it only occur following pharyngitis?  How long after infection does the hematuria typically occur?
Postinfectious glomerulonephritis is most commonly preceded by symptoms of either pharyngitis or impetigo, with a latent period from infection to hematuria of 10 and 21 days, respectively (Mayo Clin Proc, Vol. 84, pg. 72).

On urine dipstick, urine nitrites have a low sensitivity but high specificity for the diagnosis of UTI. Name an important bacterial species that does not convert nitrates to nitrites, thereby giving a false negative test.
Enterococcus species do not convert nitrates to nitrites (JEM, 7/10, pg. 6).

Most episodes of febrile neutropenia occur in patients receiving chemotherapy. When does the neutrophil nadir typically occur after the last dose?
For most outpatient chemotherapy, the neutrophil nadir typically occurs 5 to 10 days after the last dose (Mayo Clin Proc, Vol. 81, pg. 843).

What is the leading cause of reported foodborne disease outbreaks?
Norovirus is the leading cause of reported outbreaks and outbreak-related illnesses (MMWR, August 13, 2010).

The 2010 guidelines from the CDC for the upcoming influenza season recommend routine influenza vaccination for all persons over what age?
Routine influenza vaccination is recommended for all persons aged 6 months or older. This represents an expansion of the previous recommendations for annual vaccination of all adults aged 19-49 years (MMWR, 8/6/10).

The CDC has recommended a 5-dose rabies vaccination regimen for postexposure prophylaxis to prevent human rabies. How has this recommendation recently changed?
As of 2010, new recommendations reduce the number of vaccine doses to four (MMWR, March 19, 2010).

The number of rabies vaccines recommended by the ACIP (Advisory Committee on Immunization Practices) has been reduced from 5 to 4 doses for unvaccinated patients. Why?
<answer>
This was based on evidence from multiple source, including pathogenesis data, animal trials, clinical studies, and epidemiological surveillance.

The first dose of the 4-dose regimen should be administered as soon as possible after exposure (day 0). Additional doses are then given on day 3, 7, and 14. The first dose of rabies vaccine should be administered with HRIG, infiltrating as much as possible into the wound, with the remainder given IM at a distant site from the vaccine.

This recommendation is not applicable to immunocompromised patients, who should continue to receive the full five doses.

Sullivan, DM. Update on Emerging Infections: News from the Centers for Disease Control and Prevention. Infectious disease/CDC Update. Ann Em Med July 2010;56(1):64-6.</answer>

An acute a diarrheal illness has been observed to result in excessive anticoagulation from warfarin.  How does a diarrheal illness potentiate warfarin activity?
Oral intake of nutrients declines, Vitamin K absorption is less, the in vitro source of vitamin K from bacterial flora decreases, and dehydration increases the relative concentration of warfarin in the blood (JAMA, Vol. 279, pg. 657).

When treating a patient with herpes zoster (shingles) what is the effect of corticosteroids on the development of postherpetic neuralgia?
Corticosteroids DO NOT have any effect on PHN (Mayo Clin Proc, Vol. 84, pg. 274).