The potential use of bacteria and viruses as biological terror weapons makes certain
highly pathogenic microorganisms a worldwide public health threat. In an outbreak
investigation involving a possible deliberate spread of a biological warfare agent
there is a need for a fast and reliable diagnostic method. Ideally, the same method
should be usable for both bacteria and viruses. To distinguish between natural and
deliberate spread, information on the prevalence/incidence of the organism/disease,
ecology and natural mechanisms for spread is needed. In addition, knowledge of
national and international subtypes reflecting both micro- and macro-evolution of the
organisms is required for the analysis.
The field of molecular epidemiology has evolved during the last decades with the
introduction of several different methods to type and characterize bacteria. There is
now a plethora of different molecular techniques available to identify and discriminate
between different strains of bacteria. In this thesis, rapid protocols based on
pyrosequencing technology were developed and used for discrimination of Bacillus
anthracis from closely related bacillus species. The technique was also used for
identification and subtyping of Francisella species, including the human pathogen
Francisella tularensis and its subspecies. Also a rapid generic protocol for detection
and genotyping of infectious agents including bacteria, parasites, and viruses was
developed.
Tularemia epidemics occur in limited geographical areas, and at variable intervals. The
reasons for these irregularities are still unknown. There may be ecological niches in the
affected areas, which harbor the bacteria between epidemics, or the bacterium may be
reintroduced into an ecological system that permits its amplification. The establishment
of a relevant typing system indentifying individual strains is of great importance .One
of the most promising methods, MLVA was evaluated as a tool for practical use in
epidemiological investigations of tularemia in Sweden. PFGE analysis was used as
reference method. Typing data were combined with geomapping (GIS), in order to
predict sources of infection and determine possible reservoirs for the different MLVA
types. The results indicate that MLVA has the capacity to be used as a standalone
typing method in outbreak investigations. It was possible to use this method directly on
clinical specimens without isolating the bacterium by cultivation. In most cases, a
certain MLVA type was not correlated to a strict geographic location, indicating that
subtyping might be of limited use in surveillance and outbreak investigations of
tularemia in endemic countries
