H serotyping
The work presents the results of analyzing the H-serotypes of B. thuringiensis isolates secluded from the feces of 20 animal species. Of the 190 isolates, 166 were from 14 mammalian species, 20 were obtained from 5 reptile species and 4 bird species. The obtained bacterial populations were assigned to 8 serotypes: H31, H6, H3abc, H7, H4ab/43, H5ab/21, H8ab, and H9. There were 3 atypical samples in the analyzed populations, as well as 65 that were not verified. Serotype analysis showed that H3abc dominated, accounting for 82.0% of the 122 serotyped isolates, H6 serotype was much less common (8.5%). The remaining 6 serotypes accounted for only up to 1.5% (Fig. 1). The resulting isolates could be multiples of the same organism.
[Fig. 1 here]
The PCR images of B. thuringiensis serotypes are given in Fig. 2.
[Fig. 2 here]
In the feces of several herbivores, isolates belonging to H3abc were ubiquitous, accounting for 89% of B. thuringiensis populations. Examples included the feces of anthropoids and bears.
Arginine hydrolase (ADH) was used as a factor for serotype identification. Urease reducing enzymes, nitrate reducing enzymes, and enzymes involved in the degradation of sucrose, mannose, cellobiose, and salicin were also used. This also includes enzymes involved in the production of acetyl methyl carbinol (AMC). The latter reaction may be negative only in some cases. All of the above features were used to analyze different antigenic subgroups belonging to different serotypes as well as to analyze a number of isolates that belonged to certain serotypes. Isolates belonging to the same serotype may have certain differences. In particular, six isolates of serotype H8ab were similar in the main characteristics. At the same time, to confirm the hypothesis of similar main characteristics in one serotype, it is necessary to test a larger number of samples.