UMEM Educational Pearls - Infectious Disease

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 http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm257024.htm
 

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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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.

http://www.cdc.gov/vaccines/pubs/vis/downloads/vis-rabies.pdf

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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.

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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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

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.

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

Treatment:

• 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.

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

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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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 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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Does this Patient with Diabetes have Osteomyelitis?

• Diagnosis of lower extremity osteomyelitis in the diabetic patient remains challenging
• Bone biopsy with culture remains the gold standard for diagnosis but is not always obtainable
• What clinical features, therefore, raise the likelihood of osteomyelitis?
• In this review, an ulcer size > 2 cm² (LR 7.2), ability to probe to bone using a sterile stainless steel probe (LR 6.4), and an ESR > 70 mm/h were found to be useful in predicting the presence of osteomyelitis
• Clinical features NOT found to be useful included fever (sensitivity 19%), presence of erythema, swelling, or purulence (LR 1), elevated white blood cell count (sensitvity 14%-54%), and superficial swab culture
• A note about radiographic studies:
  • bony changes on plain films may take up to 2 weeks to develop
  • plain films alone are only marginally useful if positive (LR 2.3)
  • MRI is more accurate than bone scan or plain films
  • If you are going to order a radiographic study, your best bet is the MRI

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Now that we have entered the session of cookouts, picnics, and family get togethers I thought I would review some of the more common causes of food poisoning and the typical foods that they are found in.

Bacteria	Foods Typically Found In	Onset of Symptoms
Staphylococcus aureus	Meat and seafood salads, sandwich spreads and high salt foods.	4-6 hours
Salmonella	Meat; poultry, fish and eggs and now tomatoes	12 to 24 hours. Assoociated with fever
Clostridium perfringens	Meat and poultry dishes, sauces and gravies.	12 to 24 hours.
Vibrio parahaemolyticus	Raw and cooked seafood.	12 to 24 hours.  Associated with fever
Bacillus cereus	Starchy food. Typically Chinese Fried Rice in test questions	12 to 24 hours.
Campylobacter jejuni	Meat, poulty, milk, and mushrooms.	24 hours

 

It has become standard that close contacts of individuals being treated for bacterial meningitis be treated prophalacticly with antibiotics to prevent additional cases.  Fluoroquinolones, in particular ciprofloxicin, have been the drug of choice as a single dose provided adequate protection.

Now the CDC is reporting the first cluster of fluoroquinolone-resistant meningococcal disease in North America have been documented along the Minnesota-North Dakota border.  As of now, the CDC still recommends ciprofloxacin for all parts of the country except for a 34-county area in the Minnesota-North Dakota area.  In that area the CDC is recommending rifampin, ceftriaxone or azithromycin be used.

This needs to be followed closely as the resistant organism is extremely likely to spread across the country and it will probably this time next year when nobody can use ciprofloxacin anymore.

Most of use remember that Fifth disease is a viral infection presenting with a distinctive rash (slapped check) caused by Parvovirus B19.  But do you know the numbering of the other six Contagious Illnesses that are associated with rashes:

1. First Disease – Measles caused by the rubeola virus
2. Second Disease – Scarlet Fever caused by Streptococcus pyogenes Group A
3. Third Disease – German Measles caused by rubella virus
4. Fourth Disease – Dukes Disease – In the late 1880-1900’s it was widely published about but in the 1960’s it was not proven to exist by either epidemiologic criteria or isolation of an etiologic agent.  Now felt to be a mild form of scarlet fever.  Some reports of it being caused by a Coxsackvirus or Echovirus
5. Fifth Disease - Erythema infectiosum caused by Parvovirus B19. Slapped Check
6. Sixth Disease - Exanthem subitum (meaning sudden rash), also referred to as roseola infantum (or rose rash of infants), sixth disease. Presents as rapid onset high fever, followed by a fine red rash when the fever subsides. Caused by Herpes Virus 6.

 

 Ludwig’s Angina:

Ludwig’s angina is most commonly a polymicrobial disease of mixed aerobic / anaerobic bacterial origin. Dental disease is the most common cause of Ludwig’s angina.

Diagnosis is usually made after obtaining a CT scan of the Neck and upper chest. 

Once the diagnosis is made, treatment should consist of broad spectrum antibiotics and surgical evaluation by ENT or Oral Surgery for possible I&D. Aggressive management of the patient’s airway is a must, and the patient should be intubated early in the course of the illness if there is any sign of airway compromise. Nasal intubation may be preferred by ENT/Oral Surgery.

Typical Antibiotics include a Penicillin with clindamycin or metronidazole.

Ludwig’s Angina Trivia:

• Initially described in 1836 by the German physician Wilhelm Frederick von Ludwig.
• It was called angina, which finds its origin from the Greek word, anchone, which means strangulation.  The term, angina was used to connote throat pain and infection as angina originates from the Greek word, anchone, that means strangulation.
• It is believed that Elizabeth I of England died of Ludwig's angina in 1603.

A recent study came out which confirms what we already knew... that MRSA infections are no longer confined to ICUs but are spreading to the community. What the new study does show, is that it affects particular populations disproportionately and Baltimore City, more than any other study population. The full article is attached below, or can be obtained for free from the JAMA website.

"Unadjusted incidence rates of all types of invasive MRSA ranged between approximately 20 to 50 per 100 000 in most ABCs sites but were noticeably higher in 1 site (site 7, Baltimore City) (TABLE 2)." "... we calculated interval estimates excluding site 7 (Baltimore City) to allow the reader to interpret a range of estimates reflecting different metropolitan areas. Regarding the high observed incidence rates reported by site 7, we conducted an evaluation to determine whether these results were valid, including a review of casefinding methods, elimination of cases to include only those with zip codes represented in the denominator, contamination in any laboratory, and other potential causes for increased rates; however, none were in error."

Attachments

• 0710170948_jama_mrsa.pdf (129 Kb)

Important EM pearls from the recent 2007 IDSA/ATS guidelines for treatment of community-acquired pneumonia (CAP) Patients should be treated for a minimum of 5 days CURB-65 a new pneumonic; any patient with ? 2 warrants admission Confusion Uremia elevated Respiratory rate low Blood pressure age > 65 Outpatient CAP treatment Healthy + no abx in past 3 months ? macrolide Comorbidities OR use of abx within last 3 months ? a respiratory fluoroquinolone OR ?-lactam + macrolide Inpatient CAP treatment ICU patients ? ?-lactam + either azithromycin or a respiratory fluoroquinolone Non-ICU patients ? respiratory fluoroquinolone OR ?-lactam + macrolide Mandell LA, et al. Infectious Diseases Society of America/American Thoracic Society Consensus Guidelines on the Management of Community-Acquired Pneumonia in Adults Clinical Infectious Diseases 2007;44:S27-S72

PPD is considered positive: >= 15 mm Induration: Anybody >= 10 mm induration: Born in a high-revalence country, are in a medically underserved population ( e.g.:Blacks, Hispanics, and Native Americans), individuals with a medical condition that increases risk of TB (e.g.; silicosis, gastrectomy, chronic renal failure, immunosuppressant therapy, malignancy, IV drug abusers, and those that work in the medical field. >=5mm induration: HIV or suspected HIV-positive, close contacts of newly diagnosed TB Cases (everybody on the plane), and abnormal CXR with fibrotic changes suggesting old TB MMWR September 08, 1995/ 44(RR-11);18-34