UNCLASSIFIED LTC John M. Scherer/(301) 619-8837/[email protected] 1 March 2010 A Historical...

UNCLASSIFIEDLTC John M. Scherer/(301) 619-8837/[email protected] 1 March 2010

A Historical Look at Anthrax: Facts, Misperceptions, and the

Importance of Diagnostics

LTC John M. Scherer, Ph.D., M.T. (ASCP)U.S. Army

UNCLASSIFIEDLTC John M. Scherer/(301) 619-8837/[email protected] 1 March 2010Slide 2

Annals New York Acad Sci 1970; 174: 577-582

Anthrax vaccine trials begin


Fact or Fiction

• Clinical Disease = Mortality

• Only particles < 5um in size are important

• Subclincal infections do not exist

• Inhalation Anthrax = Widened Mediastinum

• Diagnosis of anthrax is easy

• Diagnostics only provide post-mortem confirmation

Slide 3


Agenda

• Impact of particle size on infection

• Subclinical infections

• Inhalation anthrax cases from the Anthrax letters

• Diagnostics– Why is it so hard?– Are there sufficient bacteria to detect?

• Temporal influence of antibiotic use on survival of inhalation anthrax

• Conclusion

Slide 4


Particle Size Alters Infectious Dose

Slide 5

J of Hyg 1953; 51 359-371

In NHPs 12 um particles are14X less effective than single cell particles


Aerosolized Bacillus anthracis in Goat Hair Processing Mills

Slide 6

Am J Hyg 1960, Vol 72: 24-31


Do Subclinical Infections Occur?

Slide 7


The case against Subclinical Infection

• No increase in protection based on length of employment in hair processing mills (Anal New York Acad Sci 1958; 70: 574-583)

– Does subclinical infection correlate with protection?

• No asymptomatic cases found following sero-surveys of potentially exposed individuals of anthrax letters (n=66) (Clinical Infectious Diseases 2005; 41:991–7)

– Antibiotic use?

Slide 8


The case for Subclincal Infection

Slide 9

Norman, PS, Am J Hyg 1960; 72: 32-37.

Albrink WS. Am J Path 1959; 35: 1055-1065

“The first two animals (John and Melvin) exhibited no positive physical disorder after their initial exposure and survived despite the fact that organisms were demonstrated in the blood of one on the second through the tenth days and of the other from the third throughthe eleventh days. The animals maintained their appetites and their vigorous protestations to physical examination in unabated manner. Although a bacteremia was apparent in each, it was of low grade and exhibited no progression. The temperature varied little from normal (100 to 101 F).”


2001 Inhalation Anthrax Cases


Inhalation anthrax from Anthrax letters

• 11 people infected with Bacillus anthracis by aerosol route

• 55% (6/11) of the inhalation anthrax cases survived

• Average time from exposure to symptoms (when known) – 4.5 days (SD 0.8 days)

• Average time of symptoms before treatment with antibiotics – 3.8 days (SD 1.6 days)

• On average it was ~8 days from the initial exposure before therapy was initiated




• Observations consistent with historical cases of inhalation anthrax

• Only 7 of 11 (64%) had a widened mediastinum


Technical Memorandum, Medical Aspects of Anthrax, AD 801-504, 1966 (date scanned)

United States Army Biological Laboratories, Fort Detrick




• Observations consistent with historical cases of inhalation anthrax

• Only 7 of 11 (64%) had a widened mediastinum

• In the post 2001 sero-survey, ~10% (n=6/66) hade a widened mediastinum that was not attributed to B. anthracis exposure

• 3 of the 11 individuals (27%) were sent home after seeking health care


Diagnostics


Why is Bacillus anthracis so difficult to diagnose?

• Physician– Uncommon– Generic flu-like illness

• Laboratory– Uncommon– Culture contamination with Bacillus species is “common”– Looks like other non-pathogenic Bacillus species– Clinical labs reluctant to report contaminants


Why is Bacillus anthracis so difficult for clinical labs to identify?

• Study conducted by Connecticut Depart of Public Health (EID 2005; 11: 1583-1486)

• 33 of 34 of Connecticut's clinical labs participated

• Mar to Dec 2003 (10 months)

• GPRs in blood or CSF isolated < 32hours

• 623 isolates reported (average 62/month)

• 195 of the isolates were Bacillus species (not anthracis)

• Additional workload ~0.3 FTEs

Slide 17


In animal models, is there sufficient bacteremia to detect?

• Some basic assumption that are supported:– Higher doses decrease incubation period– There is bacteraemia when animals are symptomatic– Levels vary but typically are > 1000 org/ml– Toxin levels are also detectable

• However, it is extremely difficult to provide a precise number because the studies use different strains, doses, animal models, and methods for determining bacteremia


Sample data

Technical Memorandum 19, Pathogenesis of Anthrax- A Progress Report, November 1962



Clinical Cases


Reported as a minimum value

Technical Memorandum 19, Pathogenesis of Anthrax- A Progress Report, November 1962


1958 Ft Detrick Case



• Inhalation anthrax letter cases - All blood samples tested before administration of antibiotics were positive by PCR

– Assay sensitivity 1 pg or 167 org (EID 2002; 8: 1178-1181).........1 org ~6 fg

– Sample volume 5 ul– Equates to ~30,000 org/ml of eluate– Specimen processing should “concentrate” sample by a factor of

10-100x

• Therefore, predicted levels in the blood would be at a minimum between 300-3,000 org/ml

• Time-to-positive estimates for blood cultures supports an estimate of >1000 org/ml (ave 14.5hrs from collection, n=7)


Clinical Infectious Diseases 2007; 44:968–71

Legend is incorrect in manuscript,

should be ng/ml


Temporal influence of antibiotic use on survival of inhalation anthrax


Anthrax survival predictions

Wilkening, PNAS 2006;103: 7589–7594Holty, Ann Intern Med. 2006;144: 270-280

Note: Left graph X axis is day symptoms develop, right graph is day of exposureFor left graph symptoms arise at a mean of 4 days following exposure


Conclusion

• Diagnosis of inhalation anthrax does not equal death (with appropriate therapy, individuals who are symptomatic for 4 days still have ~50% survival rate)

• Initiating therapy each day before the onset of fulminate anthrax improves survival by ~10-20%

• Increasing the particle size increases the ID50, it does not render the material non-infective

• Widened-mediastinum is present in only approximately 50% of cases and has been observed in non-anthrax cases

• Individuals seeking medical care are predicted to have detectable levels bacteremia

• Anthrax toxins are readily detectable at the same time as bacteria appear in the blood


LTC John M. Scherer Ph.D., M.T. (ASCP)

Voice: 301-619-8837 / DSN 343-8837Email: [email protected]

LTC John M. Scherer Ph.D., M.T. (ASCP)

Voice: 301-619-8837 / DSN 343-8837Email: [email protected]

Date post:	31-Dec-2015
Category:	Documents
Upload:	miranda-clarke
View:	213 times
Download:	1 times

UNCLASSIFIED LTC John M. Scherer/(301) 619-8837/[email protected] 1 March 2010 A Historical...

Documents