UMEM Educational Pearls - Infectious Disease

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

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

Show References

 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. 

Show References

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

Show References

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

General Information:

-As of April 5^th, 14 confirmed cases of a new influenza A virus (H7N9) have occurred in China.  Six of those have died. 

-Presumed transmission via infected poultry in bird markets, and thus far no person-to-person transmission has occurred.

-Likely susceptible to oseltamavir or inhaled zanamivir

 

Area of the world affected:

-China

Relevance to the US physician:

- Suspect in patients with a respiratory illness and appropriate travel history.

- Refer to CDC within 24 hours if test positive for flu A but cannot be subtyped

- If H7N9 is suspected, patients should be under droplet and airborne precautions

 

Bottom Line:

No human-to-human transmission from H7N9 thus far, but the possibility exists.  Any unsubtypeable influenza A patient should be placed on droplet and airborne precautions and oseltamavir or zanamivir started immediately.

 

University of Maryland Section of Global Emergency Health
Author: Andi Tenner, MD, MPH

 

Show References