Background
Burkholderia mallei
is a Gram-negative bacterium that causes glanders, a zoonotic disease, especially in equine populations (e.g. horses, donkeys, and mules).
B. mallei
usually grows slowly on most culture media, and this property makes it difficult to isolate from clinical specimens. One of the problems is that
B. mallei
is easily overgrown by other bacteria, especially in animal specimens collected from non-sterile sites. The aim of this study was to develop a new selective agar for the laboratory diagnosis of glanders. We formulated a new agar, named BM agar, to enrich
B. mallei
growth, but inhibit the growth of other bacteria and fungi based on their antimicrobial profiles. We compared the growth of
B. mallei
on BM with Xie’s and PC agars, the two previously described selective agars for
B. mallei.
Results
BM agar could sufficiently grow almost all of the tested
B. mallei
strains within 72 h: only one out of the 38 strains grew scantly after 72 h of incubation. BM agar was further tested with other
Burkholderia
species and various bacterial species commonly found in the nasal cavities and on the skin of horses. We have found that other
Burkholderia
species including
B. pseudomallei
and
B. thailandensis
can grow on BM agar, but non-
Burkholderia
species cannot. Furthermore, the specificities of the three selective agars were tested with or without spiking
B. mallei
culture into clinical specimens of non-sterile sites collected from healthy horses. The results showed that BM agar inhibited growths of fungi and other bacterial species better than PC and Xie’s agars. We have also found that growth of
B. mallei
on BM agar was equivalent to that on 5% horse blood agar and was significantly greater than those on the other two agars (
P
< 0.05).
Conclusions
We believe that BM agar can be used to efficiently isolate
B. mallei
from mixed samples such as those typically collected from horses and other contaminated environments.
Electronic supplementary material
The online version of this article (10.1186/s12917-019-1874-0) contains supplementary material, which is available to authorized users.