Purpose
Normal non-pathogenic flora can harm the host by acting as a reservoir of resistance determinants that are potentially transferable to human pathogens. This study aimed to assess the phenotypic and genotypic antimicrobial susceptibility patterns of the
Bacteroides fragilis
group (BFG) isolated from healthy individuals in Vietnam and Japan in order to elucidate the prevalence of antimicrobial resistance in human flora in the two economically and geographically different countries.
Materials and Methods
BFG was isolated from fecal samples of 80 healthy individuals in Vietnam (n=51) and Japan (n=29). Isolated strains were identified using MALDI-TOF MS, and the minimum inhibitory concentration (MIC) of 18 antibiotics was determined using the agar dilution method. Additionally, 20 antimicrobial resistance genes were detected using standard PCR.
Results
A total of 139 BFG strains belonging to 11 BFG species were isolated from the two countries, with diversity in the prevalence of each species.
B. fragilis
was not the predominant species. Isolations from Vietnam and Japan showed some similarities in terms of MIC
50
values, MIC
90
values, and the percentage of resistant strains. However, isolations from Vietnam showed significantly higher resistance to piperacillin, cefmetazole, clindamycin, tetracycline, and minocycline.
Erm
B,
tet
36,
tet
M,
nim, cat
A, and
qnr
A were not found in either country.
Cep
A was more common in
B. fragilis
than in non-fragilis
Bacteroides
. In contrast,
cfi
A,
erm
G,
mef
A,
msr
SA,
tet
X,
tet
X1,
bex
A,
qnr
B, and
qnr
S were found only in non-fragilis
Bacteroides
. There were differences in the prevalence of
erm
G,
lin
A,
mef
A,
msr
SA, and
qnr
S between isolates from Vietnam and Japan.
Conclusion
This study is the first report on the antimicrobial susceptibility patterns in the BFG isolated from healthy individuals in Vietnam and Japan. Compared to isolations from Japan, isolations from Vietnam showed significantly higher resistance to antimicrobial agents. The distribution of various antibiotic resistance genes also differed between the two countries.