Lyme Disease

Review here and NEJM reviews here and here. IDSA 2006 guidelines on tick borne illness here.

Transmitted by ticks of the Ixodes family, usually nymphs (see photos), this spirochete infection causes the following recognized syndromes:

1. Early localized infection: characteristic rash (erythema chronica migrans) with cleared centre, of at least 5cm diameter, in context of possible fever, chills, headache, malaise, myalgias.
   
2. Early disseminated infection: few days to weeks post infection. Additional ECM lesions in presence of musculoskeletal symptoms (60% - i.e. migratory arthritis, muscle and joint pain), neurological (15% -- i.e. facial nerve palsy, menigoencephalitis, radiculopathies) or cardiac (10% -- i.e. AV block)
3. Late disseminated infection: up to 60% untreated. Arthritis of knees and hips, occasionally a slowly progressive encephalopathy or polyradiculopathy.

Recent article on the emergence of this disease in Canada. This article has probably caused more phone calls to the ID service for 'Lyme' in the past few months than in the past few years. The article demonstrates the expansion of the territory of the Ixodes tick and the concern is that where the tick goes, the pathogen will eventually follow.

Treatment for early disease is oral doxycycline (or amoxicillin in patients whom doxycycline is contraindicated) for 14-21 days. EDIT: 10 days is sufficient

Remember: to get Lyme disease you need to be bitten by the right tick (see below), at the right time of year, in the right place in the world. The majority of consults seen outside endemic areas (or travel to) involve the wrong tick and the wrong place. In these cases Lyme serology will *not* be helpful due to the low specificity.

NB: NEJM review of 'chronic lyme disease' that is worth a read....


I found this site useful as well...

Addendum -- Death from chronic lyme treatment...

Latent Tuberculosis

From the Canadian TB standards:

Who to test for LTBI?

• Contacts of a known case
• Immigrants to Canada within the past 2 years
• Healthcare workers or those at high risk of nosocomial exposure
• Immunosuppressed patients (HIV, transplant, high dose steroids, TNF-alpha, etc.)
• Radiographic evidence of possible old TB without symptoms and no diagnosis

Diagnosis:

• Mantoux test (PPD) 5-TU intradermal injection
• Read at 48-72 hours
• Record the number of millimetres of induration (raised area, not just red) without rounding
  

False negative:

• Severe illness including active TB
• Malnutrition
• Immunosuppression (iatrogenic, HIV, etc)
• Major viral illness

False positive:

• Allergy to PPD
• Previous fully treated TB
• BCG (see below)
• Non-TB mycobacterial sensitization

Treatment:

1. Exclude active disease
2. INH 300mg PO OD x 9 months +/- Vitamin B6 25mg PO OD
   OR
   RIFAMPIN 600mg PO OD x 4 months
   

NNT~10 for reactivation in the general population. Risk reduction from ~10% to 1% lifetime of reactivation. Lower NNT in at-risk groups.

C. difficile

Previous blog here.

Some more "novel stuff":

• Case reports (poor quality really) of the use of tigecycline for the treatment of severe CDAD.
• Article discussing the use of the non-absorbable rifamycin, rifaximin, for the treatment of CDAD -- AKA the "rifaximin chaser"
  

Stenotrophomonas maltophilia

Today we saw a patient with S. maltophilia catheter related bacteremia.

Review of the microbiology of this organism here.

• Straight or slightly curved, motile gram negative rod
• Obligate aerobe, will grow best at 35 degrees
• Non-lactose fermenter, catalase positive, oxidase negative
• Will grow on blood agar and MacConkey -- and can be selected for using imipenem innoculated plates as they are carbepenem resistant organisms.

Can be found in the environment -- and in the hospital in multiple places, usually involving water. Patients who are infected are more likely to have:

• Prior antibiotic therapy
• Central venous catheters
• Neutropenia or cytotoxic chemotherapy
• ICU/Mechanical ventillation/Tracheostomy
• Malignancy or steroid use

The majority of cases are nosocomial; however, community acquired infections can occur.

Distinguishing between colonization and infection can be difficult, particularly for respiratory isolates. Bacteremia is a common presentation with an attributable mortality of up to 60%. ICU admission (APACHE more than 15), shock and thrombocytopenia are associated with mortality.

Endocarditis can occur, as can hospital acquired pneumonia, nosocomial meningitis, cellulitis and urinary tract infection.

TMP-SMX is the antimicrobial agent of choice (greater than 90% are sensitive). Combination with ticarcillin/clavulanate should be considered for serious infections. Quinolones may be a reasonable alternative in the TMP/SMX resistant or intolerant but consideration should also be given to combining them with ticarcillin/clavulinate.

Nodular Lymphangitis

This weekend we saw a case of nodular lymphangitis presenting with a chronic draining infection of the hand and ascending nodular lymphangitis. This was in the context of significant animal exposures and fish tank exposures.

Acute Respiratory Distress Syndrome

Today we saw a case of a patient with subacute progressive hypoxemic respiratory failure for which no infectious etiology could be confirmed.

Many different pathogens can cause sepsis, which in turn can be associated with ARDS. In terms of specific pathogens, the following are reported to cause ARDS (outside of the usual pneumonia --> sepsis --> ARDS):

• Bacterial
  
  • S. pneumoniae
  • Gram negative rods including Pseudomonas
  • Legionella, Chlamydophilia, Mycoplasma
  • Tuberculosis
• Viral
  
  • Influenza A (and B) particularly H5N1 but also H1N1 and seasonal
    
  • Coronavirus (SARS)
  • Varicella Zoster (in primary infections)
• Parasite
  
  • Plasmodium Falciparum

A non-infectious syndrome, Acute Interstitial Pneumonia (AIP) can mimic the features of ARDS pathophysiologically, radiographically, and on biopsy. Some studies suggest that AIP is as common as the infectious causes.

Guidelines for the management of severe sepsis (including ARDS) are available here.

Foley Catheter Related Urinary Tract Infection

Its not sexy -- but we saw a case of foley catheter related urinary tract infection. These two articles discuss this phenomenon (#1 #2)

The risk is approximately 5% per day of insertion and strategies aimed at minimizing this infection (as article above) are important to reduce cost, morbidity and mortality.