The Roles of a Multidrug-Resistant Klebsiella pneumoniae High-Risk Clone and Its Resistance
Plasmids on the Gastrointestinal Colonization and Host-Defense Effectors in the Gut
(HUN-REN-SU Human Microbiota Research Group No “0272”.)
(BO/00286/22/5)
The asymptomatic gastrointestinal colonization of multidrug-resistant (MDR) bacteria
can lead to difficult-to-treat infections. We investigated the role of host factors
influencing colonization in an orogastrical murine infection model using a CTX-M-15-
and OXA-162-producing Klebsiella pneumoniae ST15 (MDR-KP) strain, as well as Escherichia
coli J53 (EC) and E. coli transconjugants with an IncFII(K) plasmid carrying CTX-M-15
(EC-CTXM), and with an IncL plasmid carrying OXA-162 (EC-OXA) genes. The fecal bacterial
count in colony-forming unit/gram stool (CFU/g) was determined by cultivation, IgA
and defensin levels by ELISA, and gut microbiota by 16S rRNA analysis. The CFU was
the lowest in EC, followed by EC-OXA and EC-CTXM, and the highest in the MDR-KP group.
The IgA level in feces increased in MDR-KP, EC-CTXM, and EC-OXA, and did not change
in EC. The beta-defensin 3 level markedly increased in all groups, with the highest
values in MDR-KP and EC-CTXM. Alpha-defensin-5 increased in all groups especially
in EC. In microbiota, the Bacteroidota phylum was dominant in MDR-KP, EC-CTXM, and
EC-OXA, whereas Proteobacteria was dominant in EC. The Muribaculaceae family was significantly
more common in the MDR-KP and EC-OXA groups, while the Lachnospiraceae family was
dominant in the EC group. While fecal IgA levels positively correlated with colonizing
bacterial CFU, the alpha-defensin 5 levels inversely correlated with CFUs and IgA
levels. The presence of the IncFII(K) plasmid induced beta-defensin 3 production.
The amounts of the Muribaculaceae family members exhibited a correlation with the
IncL plasmid. The detected amounts of the Lachnospiraceae family indicated the protective
role against the high-risk clone and the resistance plasmids’ dissemination. Our results
suggest that not only the MDR-KP clone itself but also the resistance plasmids play
a primary role in the colonization rate in the gastrointestinal tract. Both the MDR-KP
clone as well as the IncFII(K) and IncL resistance plasmids provide survival and colonization
benefits in the gut.