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noisymaniacalBiotechnology

Feb 20, 2013 (4 years and 5 months ago)

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Medical Microbiology


Detection of disease:


Signs & Symptoms


Traditional Microbiological Identification


Physiological Characteristics


Microscopy Techniques


Biotechnology (e.g. PCR)


Immunological


Serological testing by agglutination


Fluorescent Antibodies


Enzyme Linked Immuno
-
Absorbance (ELISA) Assay


Western Blots for ELISA confirmation


Selected “Nasties”:

Agglutination Serological Test

Figure 18.6

Fluorescence Microscopy

ELISA

direct

indirect

Yersinia pestis

Black Death

Taxonomy


Member of the
Enterobacteriaceae

family



Yersinia is a Gram
-
negative coccobacilli



Target Tissues


This disease direct effects the lymph nodes which can
be found in the groin, neck, and armpits and cause
them to enlarge and suppurate.

Ecology and Infection Process


Biological vectors

Fleas

Rodents

Flea draws viable
Y. pestis

organisms


into its intestinal tract, and they multiply.


Some
Y. pestis

in the flea regurgitated

when the flea gets its next blood meal thus
transferring the infection to a new host.


A few bacilli are taken up by tissue macrophages
after they lose their capsular layer. Macrophages
can’t kill
Y. pestis

and provide protected
environment for bacilli so they can re
-
synthesize
their capsular layer.


The re
-
encapsulated organisms then kill the
macrophage and are released into the
extracellular environment where they travel to
draining lymph nodes.




Symptoms


Bubonic Plague

bacteria infect lymph nodes


Bubos


Fever


Headache


Vomiting Blood


Diagnostic Tests


Take smear from blood or feces
for bubonic plague


> bacteria has “safety pin”
appearance


Can also use FA (fluorescent
-
antibody) test

All plague bacilli have
unique diagnostic envelope glycoprotein called

the Fraction 1 (F1) antigen


Treatments and Preventive
Measures

7
-

to 10
-
day course of antimicrobic therapy


streptomycin


chloramphenicol


tetracycline


Vaccine:

Y. pestis

organisms grown in artificial media, inactivated with

formaldehyde, and preserved in 0.5% phenol. The vaccine contains

trace amounts of beef
-
heart extract, yeast extract, agar, and

peptones and peptides of soya and casein.


Control of rat populations concurrent with elimination of their flea

prevent spread of the plague to humans.

Epidemiology: Transmission


Bubonic

Infected Rodent


Fleas


Humans

Can also enter through breaks in skin when handling infected animal




Prevalence and Distribution in Global
Human and Animal Populations

1000
-

3000 cases reported

annually across the world


Africa (most cases)


Asia


Northeastern Brazil


Andes Mountain Regions


US (19
-
40 cases a year mostly


in Western areas such as


New Mexico and Arizona)

Mortality

Bubonic Plague


Untreated 50
-

60% mortality rate

Treated 5


20% mortality rate

Killed one third of the world’s population during the 14
th

century



Latest reports


As of 15 March 2001, World Health Organization has
reported a total of 436 suspected cases, including 11 deaths
in Nyanje area in Zambia.



As of 27 May 2002,
the Malawian Ministry of Health
has
reported a total of
71
cases of
bubonic

plague in Malawi.






Latest research


EVOLUTION:
A single gene change in a relatively
benign recent ancestor of the bacterium that causes
bubonic plague played a key role in the evolution of the
deadly disease

from a germ that causes a mild human
stomach illness acquired via contaminated food or water
to the flea
-
borne agent of the "Black Death.”




GENETICS:

Research on three genes, hemin storage
(hms)

genes, in
Y. pestis that

change it from a harmless,
long
-
term inhabitant in the flea midgut to one that
amasses in its foregut.




PREVENTION:
Current prevention measures include
dusting family pets with insecticides to prevent the
spread of the Yersinia pestis organism from the native
prairie dog populations