UMEM Educational Pearls - Infectious Disease

Category: Infectious Disease

Title: HIV/AIDS medications and their common side effects

Keywords: HIV, Medications (PubMed Search)

Posted: 6/20/2020 by Michael Bond, MD (Updated: 6/21/2020)
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HIV/AIDS medications and their common side effects
  • Didanosine: pancreatitis
  • Indinavir: nephrolithiasis
  • Isoniazid: hepatitis
  • Trimethoprim-sulfamethoxazole: hyperkalemia, Stevens-Johnson Syndrome
  • Ritonavir: paresthesias, metabolic syndrome
  • Pentamidine: hyperglycemia or hypoglycemia
  • Efavirenz: psychosis
  • Dapsone: hepatitis
  • Nevirapine: hepatic failure
  • AZT: bone marrow suppression and macrocytic anemia
Thing you need to know for your certifying exam

Category: Infectious Disease

Title: Update to C. Difficile Treatment

Keywords: clostridium difficile, antibiotics, vancomycin (PubMed Search)

Posted: 8/4/2018 by Ashley Martinelli (Updated: 5/25/2024)
Click here to contact Ashley Martinelli

  • IDSA/SHEA recently released a guideline update for the management of Clostridium difficle infections
  • Discontinue inciting antibiotic therapy as soon as possible
  • Metronidazole is no longer considered first line therapy for C. difficle infection
  • Treatment course for 10 days unless initial fulminant or recurrence requiring vancomycin taper
  • Remember: Vancomycin IV does not cross into the GI tract and cannot be used to treat C. difficile

Clinical Definition


Initial episode, non-severe

WBC ≤ 15,000 AND  SCr <1.5

  • Vancomycin PO 125mg 4x daily, OR
  • Fidaxomicin PO 200mg 2x daily

If above agents unavailable, metronidazole PO 500mg 3x daily


Initial episode, severe

WBC ≥ 15,000 OR  SCr >1.5

  • Vancomycin PO 125mg 4x daily, OR
  • Fidaxomicin PO 200mg 2x daily


Initial episode, fulminant

Hypotension, shock, ileus, megacolon

  • Vancomycin PO 500mg 4x daily
  • Ileus? Give vancomycin enema 500mg q8h


First Recurrence


  • Prolonged vancomycin PO taper 125mg 4x daily, OR
  • Vancomycin PO 125mg 4x daily x 10 days if metronidazole was used initially
  • Consider fidaxomicin PO 200mg 2x daily if vancomycin used for initial treatment


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Debating between cefepime or piperacillin/tazobactam for your septic patient? Use this table to help you decide.





Gram Negative Spectrum

Pseudomonas aeruginosa 



Aerobic gram negative organisms 

E. coli 

Klebsiella sp. 

Proteus mirabilis 

M catarrhalis  

H. influenza 

E. coli 

Klebsiella sp. 

Proteus mirabilis 

M. catarrhalis 

H. influenza 

Anerobic gram negative organisms 


B. fragilis 


Gram Positive Spectrum




Aerobic gram positive organisms 



Group A Strep 

S. pneumoniae 




Group A Strep 

S. pneumoniae 

E. faecalis 

Anaerobic gram positive organisms 

P. acnes 


P. acnes 


Clostridium sp. 

Infection Site Concerns

CNS Penetration 



Urine Penetration 



Lung Penetration 



Dosing Frequency (Normal Renal Function)



1Tazobactam CNS penetration is limited, thus limiting antipseudomonal activity in the CNS 

2. Low pulmonary penetration, may not achieve therapeutic levels in patients with critical illness 


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Category: Infectious Disease

Title: Risk Factors for Community Associated C. difficile Infection

Keywords: c. difficile, antibiotic (PubMed Search)

Posted: 12/2/2017 by Ashley Martinelli (Emailed: 12/6/2017) (Updated: 12/6/2017)
Click here to contact Ashley Martinelli

Community-associated Clostridium difficile infection (CA-CDI) represents 41% of all CDI cases annually.  The association of specific outpatient exposures was assessed in a case control study by Guh, et al. They reviewed the CDC’s active surveillance reporting from 10 states through the Emerging Infections Program (Maryland participates).

Cases: ≥18, + C. difficile stool specimen collected as an outpatient or within 3 days of hospitalization, with no overnight stay in a health care facility in the prior 12 weeks, and no prior CDI diagnosis

Controls: matched 1:1 for age and sex within the same surveillance catchment area as the case patient on the date of the collection specimen. Exclusion criteria: prior diagnosis of CDI, diarrheal illness, overnight stay in health care facility in the prior 12 weeks

Data Collection: telephone interview, standardized questionnaire or comorbidities, medication use, outpatient health care visits, household and dietary exposures in the prior 12 weeks

Results: 452 participants (226 pairs), over 50% were ≥ 60 years of age, 70.4% female, and 29% were hospitalized within 7 days of diagnosis, no patients developed toxic megacolon or required colectomy.

Cases had more health care exposures, including the emergency department (11.2% vs 1.4% p <0.0001), urgent care (9.9% vs 1.8%, p=0.0003). In addition, cases also reported higher antibiotic exposures (62.2% vs 10.3%, p<0.0001) with statistically significant higher exposure to cephalosporins, clindamycin, fluoroquinolones, metronidazole, and beta-lactam and/or beta-lactamase inhibitor combination. The most common antibiotic indications were ear or sinus infections, URI, SSTI, dental procedure, and UTI. No differences were found in household or dietary exposures.

Take-home point: This study highlighted the risk for CA-CDI infection for patients presenting to an ED and reiterates that exposures to fluoroquinolones, cephalosporins, beta-lactam and/or beta-lactamase inhibitor combinations, and clindamycin significantly increases the risk of CA-CDI infection. Reducing unnecessary outpatient antibiotic prescribing may prevent further CA-CDI. 36% of case patients did not have any antibiotic or outpatient health care exposure; therefore, additional risk factors may exist.

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Category: Infectious Disease

Title: Cellulitis--Does your patient really have it?

Keywords: cellulitis (PubMed Search)

Posted: 12/15/2016 by Michael Bond, MD (Emailed: 12/17/2016) (Updated: 12/17/2016)
Click here to contact Michael Bond, MD


Take home points:

  1. Cellulitis is overdiagnosed
  2. 1/3 of patients diagnosed with cellulitis in the ED are ultimately given a different diagnosis
  3. The most common final diagnoses are vascular or inflammatory conditions.
  4. The over treatment of cellulitis increases healthcare costs, increases risk of adverse reactions, and can contribute to the development of drug resistant organisms.

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Category: Infectious Disease

Title: Zika Update: Signs and Symptoms

Keywords: Zika, arbovirus, infectious disease, mosquitos (PubMed Search)

Posted: 8/31/2016 by Jon Mark Hirshon, PhD, MPH, MD
Click here to contact Jon Mark Hirshon, PhD, MPH, MD

Zika virus and its transmission is currently an important infectious disease topic in the United States and the Western Hemisphere.  With domestic spread in the Continental United States, and the likely further spread to other parts of the southern United States, continued vigilance by healthcare providers remains important.


What are the signs and symptoms of Zika?


Most common signs and symptoms are:

  • Fever
  • Rash
  • Arthralgias
  • Conjunctivitis (generally nonpurulent)


Other symptoms can include

  • Myalgias
  • Headaches
  • Retro-orbital pain
  • Gastrointestinal upset


Symptoms can generally last 2 to 7 days.  Most individuals will have minimal or no significant symptoms and may not seek medical care. These symptoms are similar to other arboviruses, such as dengue or chikungunya. Potential serious complications include Guillian Barre syndrome.


Of course, the main concern remains infection of pregnant women and the impact that Zika has on the developing fetus, especially for the brain.

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Category: Infectious Disease

Title: Cutaneous Larva Migrans- What is it?

Keywords: Rash, Cutaneous larva migrans, nematode, tropics (PubMed Search)

Posted: 3/16/2016 by Jon Mark Hirshon, PhD, MPH, MD
Click here to contact Jon Mark Hirshon, PhD, MPH, MD

Cutaneous larva migrans (CLM) is an acquired dermatosis

  • Seen in patients returning from the tropics
    • Often seen in patient with a history of sunbathing or in barefoot beachgoers
  • Caused by the larvae of various nematode parasites of the hookworm family (Ancylostomatidae), with Ancylostoma braziliense the most frequently found in humans.


Clinical manifestations:

  • Linear, serpentine erythematous lesions
  • Intense pruritus
  • Will often heal spontaneously over weeks or months without treatment



  • Thiabendazole (applied topically)
    • Oral alternatives include other anti-parasitic medications such as albendazole, ivermectin
    • Oral thiabendazole as a single dose can be used, but is less effective than albendazole or ivermectin
  • Consider antibiotics if there is secondary bacterial infections
  • Freezing the leading edge has been previously used, but is considered ineffective and painful.


Bottom Line:

  • Consider CLM the next time a patient complains of a linear, erythematous itchy rash after returning from their all-inclusive stay in a Caribbean resort

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1603162221_clm.jpg (86 Kb)

Category: Infectious Disease

Title: A new form of Lyme Disease

Posted: 2/10/2016 by Michael Bond, MD (Emailed: 2/13/2016) (Updated: 2/13/2016)
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Borrella mayonii a new species

There is a new bacteria that is causing Lyme disease. Borrella burgdorferi is the typical bacteria associated with lyme disease, but now several cases of Borrelia mayonii have been isolated from patients and ticks that live in Minnesota, Wisconsin and North Dakota. What is unique about this new species is that it is associated with nausea, vomiting, diffuse macular rashes, and neuro symptoms [e.g.: confusion, visual disturbance, and somnolence) along with the typical lyme disease symptoms of arthralgias and headaches.

Current lyme tests should detect this new species and treatment is the same as Borrella burgdorferi. The take home pearl is that we may see patients with "atypical" lyme disease symptoms so this should be on our differential for patients presenting with rashes, nausea, vomiting and neurologic complaints.

Category: Infectious Disease

Title: New C. Diff Colitis Medication

Keywords: C. Diff Colitis (PubMed Search)

Posted: 7/16/2011 by Michael Bond, MD (Updated: 5/25/2024)
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C. Diff Colitis

The general treatment recommendations for C. Diff Colitis are to place the patient on PO metronidazole and if they fail this treatment PO vancomycin (125 mg 4x day).  Vancomycin is generally reserved for resistant cases due to the fear that it could induce Vancomycin resistant enterococcus.

For severally ill patients it is recommended that you prescribe IV metronidazole and PO vancomycin when they are not actively vomiting.  Remember there is no role for IV vancomycin as it does not get into the bowel lumen to eradicate the infection.

There is some great news though, the FDA recently approved a new drug, a macrolide antibiotic fidaxomicin (Dificid), for the treatment of C. Diff Colitis. Fidaxomicin was found to be as effective as vancomycin in preventing recurrence 3 weeks after treatment.  Currently it is recommended that fidaxomicin be reserved for cases where patients are having recurrences after 3 weeks of vancomycin treatment.

The FDA news release can be found at

Category: Infectious Disease

Title: Soft Tissue Infection in Cirrhotic Patients

Keywords: infection, cirrhosis (PubMed Search)

Posted: 4/4/2011 by Rob Rogers, MD (Updated: 5/25/2024)
Click here to contact Rob Rogers, MD

Hemorrhagic bullae in an ill-appearing patient with underlying cirrhosis should prompt consideration for an invasive infection due to Vibrio vulnificus.

V. Vulnificus is a gram negative rod and causes a highly lethal infection in patients with cirrhosis.

Antibiotics for these patients should include coverage for this organism. This should include doxycycline and a third genaration cephalosporin.

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Category: Infectious Disease

Title: Rabies Update: News from the CDC

Keywords: rabies, vaccination, animal bite, racoon, bat (PubMed Search)

Posted: 8/5/2010 by Ellen Lemkin, MD, PharmD
Click here to contact Ellen Lemkin, MD, PharmD

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.

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.

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Spinal Epidural Abscess Pitfalls

  • The classic triad of back pain, fever, and neurologic deficits are found in < 15% of patients at the time of presentation
  • Up to 75% will be afebrile
  • Up to 67% will have a normal initial neurologic exam
  • < 40% have a WBC greater than 12,000 cells/mm3
  • < 33% will have an abnormality on plain film in the first 7-10 days

Take Home Point: In the patient with risk factors for spinal epidural abscess (IVDU, DM, indwelling catheters, etc) do not exclude the diagnosis based upon the absence of a fever, a normal WBC count, and a normal neurologic exam.

Category: Infectious Disease

Title: Herpes Encephalitis

Keywords: Encephalitis, Herpes (PubMed Search)

Posted: 9/22/2009 by Rob Rogers, MD (Updated: 5/25/2024)
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Herpes Encephalitis-When to Consider

Herpes encephalitis is a potential lethal condition with high morbidity. Obviously our job in the ED is to rule-out bacterial meningits. So, when should we consider the diagnosis of herpes encephalitis?

  • High wbc in the CSF with a negative gram stain
  • Lymphcytic predominance in the CSF
  • Altered patient and abnormal CSF
  • And, just about any of the softer "rule-out aseptic meningitis" patients

Although no great guidelines exist, consider ordering a herpes PCR when sending studies on the "rule-out meningitis" patient. What about emperically treating a patient with Acyclovir? Again, no great data. Consider treating with 10 mg/kg IV q 8 hours for patients with abnormal CSF (in addition to the Ceftriaxone/Vanc, etc.) if you are worried about them, if they are altered (or encephalopathic), and if the CSF is abnormal (elevated wbc) with a negative gram stain. Acyclovir can always be discontinued when the PCR returns negative.


Daptomycin and MRSA

  • Several new antibiotics are approved for the treatment of infections due to MRSA: linezolid, daptomycin, and tigecycline.
  • Although most are familiar with linezolid, it seems that both daptomycin and tigecycline are being used more frequently.
  • A few pearls on daptomycin:
    • administered IV once daily
    • dose needs to be adjusted in patients with renal failure
    • exerts its effect through a calcium-dependent binding to the bacterial membrane resulting in cell death
  • Importantly, daptomycin is inactivated by pulmonary surfactant and therefore should not be given in patients with suspected MRSA pneumonia.

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Category: Infectious Disease

Title: Infections That Cause Temperature-Pulse Dissociation

Keywords: Infections, Temperature (PubMed Search)

Posted: 12/29/2008 by Rob Rogers, MD (Updated: 5/25/2024)
Click here to contact Rob Rogers, MD

This pearl is dedicated to Dr. Michael Rolnick....


Infections That Cause Temperature-PulseDissociation

Certain infections may cause temperature-pulse dissociation (relative bradycardia in association with fever).

Remember that normally there will be an increase in pulse rate by 10 bpm for every 1 degree increase in temperature. So, if a patient has a temperature of 103 F, expect them to be tachycardic.

Any intracellular organism has the potential to cause a relative bradycardia (Faget's sign)

Infections that cause dissociation:

  • Salmonella typhi
  • C burnetii (agent of Q fever)
  • Chlamydia infections
  • Dengue fever

Category: Infectious Disease

Title: CA-MRSA, treatment

Keywords: CA-MRSA, Treatment (PubMed Search)

Posted: 12/27/2008 by Michael Bond, MD (Updated: 5/25/2024)
Click here to contact Michael Bond, MD

It is almost impossible to get through a shift these days with out seeing an abscess that is caused by CA-MRSA.  As of the 2007 Antibiotic nomogram (2008 data not yet available) at University of Maryland CA-MRSA was only 70% sensitive to clindamycin, and >98% sensitive to bactrim and > 96% sensitive to doxcycline.  A local community hospital in Baltimore is showing only 55% sensitivity to clindamycin.

As a New Year's resolution to yourself I recommend that you check with your local hospital's Micrology department to see what the sensitivities are to bactrim, clindamycin, doxycycline.  If sensitivities are less than 80% it would generally be recommended that these medications not be used as initial empiric treatment.

For Baltimore bactrim and doxycycline should probably be the preferred treatment options.

Have a Great New Year.

Category: Infectious Disease

Title: Healthcare Associated Pneumonia

Keywords: Pneumonia (PubMed Search)

Posted: 11/18/2008 by Rob Rogers, MD (Updated: 5/25/2024)
Click here to contact Rob Rogers, MD

Healthcare Associated Pneumonia (HCAP)....why is this important for the emergency physician?

Most of us are very familiar with the types of pneumonias commonly seen in clinical practice: community-acquired pneumonia (CAP), hospital-acquired pneumonia(HAP), and ventilator-associated pneumonia (VAP). But, some may not be that aware of a relatively newer type of pneumonia that has been well-defined, healthcare-associated pnemonia (HCAP). Experts in infectious disease and critical care now say that we (the ED) should be assessing ALL pneumonia patients for HCAP risk factors.

Why care, you ask?

  • Higher mortality than CAP
  • May look like CAP
  • Treated much differently than CAP

Risk factors: (most are common sense)

  • Nursing home or extended care facility resident
  • Recently admiited to a hospital for 2 or more days in the preceeding 90 days
  • Home wound care or attending a clinic for wound care
  • Dialysis patient
  • Home infusion therapy (antibiotics)
  • Immunosuppresive therapy or disease


  • 3 drugs....not like treatment of CAP!
  • Usually a combination of a big gun anti-pseudomonal (e.g. Pip/Tazo) combined with a broad spectrum respiratory fluoroquinolone (e.g. Moxi), combined with Vancomycin
  • Key difference between treatment of CAP and HCAP is consideration for multi-drug resistant pathogens, pseudomonas, and MRSA.

Category: Infectious Disease

Title: Spontaneous Bacterial Peritonitis

Keywords: spontaneous bacterial peritonitis, ascites, paracentesis (PubMed Search)

Posted: 10/14/2008 by Mike Winters, MBA, MD (Updated: 5/25/2024)
Click here to contact Mike Winters, MBA, MD

Can You Rely on Your Clinical Impression to Exclude SBP?

  • SBP is an important can't miss diagnosis, as the mortality rate even for treated patients is approximately 20%
  • The incidence of SBP ranges from 2.5% (clinic setting) to 12% of all patients admitted with decompensated cirrhosis
  • SBP is diagnosed by a neutrophil count > 250 or a positive ascitic fluid culture obtained via paracentesis
  • Can our clinical impression exclude SBP without performing a paracentesis? Unfortunately, the answer is NO.
  • Sensitivity of physician clinical impression is just about 75%, with a specificity of 34%
  • Fever is uncommon in patients with SBP (sensitivity as low as 17%)
  • Take Home Point: only a diagnostic paracentesis can reliably exclude SBP in patients admitted for decompensated cirrhosis

Show References

Category: Infectious Disease

Title: HCAP ?

Keywords: health care associated pneumonia, antibiotics, (PubMed Search)

Posted: 9/16/2008 by Mike Winters, MBA, MD (Updated: 5/25/2024)
Click here to contact Mike Winters, MBA, MD

Health care-associated pneumonia

  • Health care-associated pneumonia (HCAP) is a distinct entity
  • HCAP includes any patient with pneumonia and 1 or more of the following:
    • hospitalization for 2 or more days in an acute care facility within the preceeding 90 days
    • nursing home patients
    • patients of long-term care facilities
    • patients who attend a hospital or hemodialysis clinic
    • patients who received IV antibiotics, chemotherapy, or wound care within 30 days of infection
  • Data indicate that the mortality for HCAP is higher than CAP
  • The most common organisms in HCAP include S.aureus, P.aeruginosa, Klebsiella species, Haemophilus species, and Escherichia species
  • An initial recommended antibiotic regimen includes a combination of an antipseudomonal cephalosporin plus a fluoroquinolone plus an agent active against MRSA

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Category: Infectious Disease

Title: Necrotizing Fasciitis Pearl

Keywords: necrotizing fasciitis (PubMed Search)

Posted: 8/4/2008 by Rob Rogers, MD (Updated: 5/25/2024)
Click here to contact Rob Rogers, MD

 Necrotizing Fasciitis Pearl

A few things to remember about treating necrotizing soft tissue infections:

  • Often polymicrobial and most of the time we in the ED won't have a microbial diagnosis
  • If due to strep, patient may benefit from the addition of Clindamycin. Streptococcal species may stop multiplying in a wound/cellulitis and continue to produce large amounts of tissue toxin. In this case, many antibiotics (like the ubiquitous Zosyn-which works on dividing bacteria) may not work well. Clindamycin will actually affect toxin binding. The phenomenon of Strep species  dividing but continuing to produce toxin is referred to as the Eagle affect. 

So, when shot-gunning the antibiotics in a patient with a really bad soft tissue infection (not the run of the mill cellulitis) consider adding Clindamycin to the regimen. 

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