New Anthrax Guidelines
By Amesh A. Adalja, MD, FACP, FACEP, March 21, 2014
It has been 13 years since the anthrax attacks of 2001 killed 5 and infected 17 people. Since that time, there has been a large outbreak among injection drug users in Europe and sporadic cases in the US, the last of which occurred in Minnesota in 2011. Details of that case have just been published.1
Evidence-based clinical guidance for treatment of anthrax is difficult to derive because clinical data are limited. Nonetheless, in February of this year, the CDC released significant new guidance containing several important points that merit emphasis.2
Presence of Meningitis Key Clinical Decision Point
Probably the biggest change in the guidance is to explicitly base treatment decisions on the presence or absence of meningitis, which is present in a high proportion of inhalational anthrax cases. Meningitis is often fatal and enhanced therapy is the most efficacious. If meningitis is present, 3 drugs are recommended: 1 with high CNS penetration (eg, meropenem) + 1 protein synthesis inhibitor (eg, linezolid) + 1 bactericidal agent (eg, ciprofloxacin). When meningitis is thought unlikely, the CNS penetrating agent need not be administered and 2 drugs are sufficient.1
Antitoxin Antibody Administration Stressed
As anthrax is largely a toxin-mediated illness, the use of an antitoxin is biologically plausible. Administration has been correlated with a diminution of the toxin burden, as was the case in the 2011 Minnesota case.1 This experience and the availability of GSK's raxibacumab and Emergent's anthrax immune globulin (AIG) led to the recommendation that antitoxin antibody should be administered to people with systemic illness.1
Fluid Drainage Emphasized
Another new recommendation is that fluid accumulation should be addressed. Pleural effusions and ascites teem with toxins and serve as reservoirs. Drainage, much like that performed for a traditional empyema, is a form of source control correlated with improved outcomes. The guidance recommends that such drainage be performed on anthrax patients with ascites and/or pleural effusions. In the case of pericardial effusions, drainage should be performed only when hemodynamic compromise is present.1
The guidance represents a big step forward in that it systematically assessed the available evidence related to treatment of anthrax and inferred best practices. Like the "Surviving Sepsis" guidelines, this document stands to have a positive impact on the care of patients with anthrax and to provide a platform from which to test other interventions.
- Sprenkle MD, Griffith J, Marinelli W, et al. Lethal factor and anti-protective antigen IgG levels associated with inhalation anthrax, Minnesota, USA. Emerg Infect Dis 2014. http://wwwnc.cdc.gov/eid/article/20/2/13-0245_article.htm. Accessed March 4, 2014.
- Hendricks KA, Wright ME, Shadomy SV, et al. Centers for Disease Control and Prevention expert panel meetings on prevention and treatment of anthrax in adults. Emerg Infect Dis 2014. http://dx.doi.org/10.3201/eid2002.130687. Accessed March 4, 2014.