During the selection process of probiotics for vaginal applications, twenty-five lactic acid bacteria (LAB) isolates from human vagina belonging to six different species were tested for antimicrobial resistance by a microdilution method. Gene-specific PCR amplifications proved the strains carry no acquired antibiotic resistance genes, except for a tet(W) gene present in two tetracycline-susceptible Bifidobacterium bifidum strains. Genome analysis of a selected set of strains showed no other acquired resistance determinants. The tet(W) of B. bifidum was inactive by the insertion of two guanine residues in the middle of the gene. Surprisingly, the inactive gene became active and functional very easily, providing resistance to tetracycline and remaining stable afterward. LAB intended to be used in health applications must be free of acquired antimicrobial resistance genes; these could be spread and transferred to human pathogens.
Species | Strain | Antibiotic (MIC as µg mL−1) | |||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
GEN | KAN | STR | NEO | TET | ERY | CLI | CHL | AMP | PEN | VAN | QDA | LIN | TMP | CIP | RIF | ||
L. crispatus | VA20-32AN | 2 | 16 | 2 | 16 | 2 | 0.06 | 0.25 | 4 | 1 | 0.5 | 0.5 | 1 | 4 | >64 | 16 | 1 |
VA27-7 | 4 | 32 | 64 | 8 | 1 | 1 | 2 | 8 | 2 | 2 | 1 | 1 | 4 | 32 | 64 | 4 | |
VA27-9 | 1 | 16 | 2 | 2 | 2 | 0.03 | 0.5 | 4 | 2 | 0.5 | 0.5 | 1 | 4 | 64 | 32 | 2 | |
VA28-12 | 1 | 16 | 2 | 2 | 2 | 0.06 | 0.5 | 4 | 2 | 0.5 | 0.5 | 2 | 4 | 64 | 32 | 2 | |
VA32-17 | 2 | 64 | 2 | 8 | 4 | 0.03 | 0.5 | 2 | 1 | 1 | 0.5 | 1 | 2 | >64 | 64 | 8 | |
VA32-17AN | 4 | 128 | 32 | 4 | 2 | 0.25 | 0.5 | 4 | 1 | 0.5 | 1 | 1 | 2 | 16 | 32 | 4 | |
VA50-4AN | ≤0.5 | 32 | 1 | 2 | 4 | 0.12 | 0.12 | 4 | 4 | 1 | 0.5 | 1 | 4 | >64 | 32 | 4 | |
L. jensenii | VA04-1AN | ≤0.5 | 4 | 2 | 1 | 0.25 | ≤0.016 | 0.12 | 4 | 0.25 | 0.12 | 1 | 0.5 | 1 | >64 | 8 | 0.25 |
VA04-2AN | ≤0.5 | 4 | 4 | 1 | 0.5 | 0.03 | 0.12 | 2 | 0.5 | 1 | 1 | 0.5 | 2 | >64 | 8 | 0.25 | |
VA15-2AN | ≤0.5 | ≤2 | 1 | ≤0.5 | 1 | ≤0.016 | ≤0.03 | 2 | 0.06 | 0.06 | 0.5 | 0.5 | 0.5 | >64 | 8 | 0.25 | |
VA16-11 | ≤0.5 | 8 | 1 | 2 | 4 | 0.06 | 0.25 | 4 | 0.06 | ≤0.03 | 2 | 0.5 | 2 | >64 | 16 | 0.5 | |
Breakpoint (µg mL−1) | 16 | 16 | 16 | - | 4 | 1 | 4 | 4 | 2 | - | 2 | - | - | - | - | - | |
L. salivarius | VA09-4 | 8 | 64 | 16 | 4 | 2 | 0.25 | 0.25 | 2 | 1 | 0.25 | 128 | 0.25 | 0.5 | ≤0.12 | 1 | 2 |
VA16-20 | ≤0.5 | 4 | 2 | 0.5 | 1 | 0.06 | 0.06 | 2 | 0.5 | 0.12 | >128 | 0.5 | 0.5 | 0.25 | 0.5 | 0.5 | |
VA37-13 | ≤0.5 | 4 | ≤0.5 | ≤0.5 | 0.5 | 0.06 | 0.06 | 2 | 0.25 | 0.12 | >128 | 0.5 | 0.5 | 0.25 | ≤0.25 | 0.5 | |
VA40-10 | 128 | >1024 | >256 | 256 | 2 | 1 | 1 | 4 | 1 | 0.25 | >128 | 1 | 1 | 1 | 4 | 0.5 | |
VA40-12AN | 4 | 128 | 32 | 4 | 2 | 0.25 | 0.25 | 4 | 0.5 | 0.25 | >128 | 1 | 0.5 | 0.25 | 1 | 1 | |
VA40-14AN | 4 | 128 | 32 | 4 | 2 | 0.25 | 0.5 | 4 | 0.5 | 0.25 | >128 | 1 | 0.5 | ≤0.12 | 1 | 1 | |
Breakpoint (µg mL−1) | 16 | 64 | 64 | - | 8 | 1 | 4 | 4 | 4 | - | n.r. | - | - | - | - | - | |
L. paracasei | VA02-1AN | ≤0.5 | 16 | 8 | 1 | 2 | 0.12 | 0.06 | 8 | 1 | 0.25 | >128 | 1 | 4 | 0.5 | 4 | 0.5 |
VA24-4 | 1 | 16 | 8 | 4 | 4 | 0.12 | 0.06 | 4 | 0.5 | 0.25 | >128 | 1 | 2 | 0.25 | 4 | 0.5 | |
VA26-3 | ≤0.5 | 16 | 8 | 2 | 2 | 0.12 | 0.06 | 4 | 1 | 0.25 | >128 | 1 | 2 | 1 | 2 | 0.5 | |
VA27-8 | 1 | 32 | 16 | 8 | 2 | 0.06 | 0.06 | 8 | 0.5 | 0.25 | >128 | 1 | 4 | 0.25 | 4 | 0.5 | |
Breakpoint (µg mL−1) | 32 | 64 | 64 | - | 4 | 1 | 4 | 4 | 4 | - | n.r. | - | - | - | - | - | |
L. reuteri | VA15-3 | ≤0.5 | 4 | 2 | ≤0.5 | 8 | 0.12 | ≤0.03 | 4 | 1 | 2 | >128 | 1 | 2 | >64 | 32 | 0.25 |
VA24-5 | ≤0.5 | 16 | 4 | ≤0.5 | 16 | 0.06 | ≤0.03 | 4 | 2 | 8 | >128 | 0.5 | 4 | >64 | 32 | 0.25 | |
Breakpoint (µg mL−1) | 8 | 64 | 64 | - | 32 | 1 | 4 | 4 | 2 | - | n.r. | - | - | - | - | - | |
B. bifidum | VA07-1AN | 8 | 64 | >256 | 16 | 1 | ≤0.016 | 0.06 | 1 | ≤0.03 | ≤0.03 | 0.5 | 0.5 | 0.5 | 16 | 8 | 2 |
VA07-2AN | 32 | 64 | >256 | 32 | 1 | ≤0.016 | ≤0.03 | 1 | ≤0.03 | ≤0.03 | 1 | 0.5 | 0.5 | 16 | 8 | 1 | |
Breakpoint (µg mL−1) | 64 | - | 128 | - | 8 | 1 | 1 | 4 | 2 | - | 2 | - | - | - | - | - |
This entry is adapted from the peer-reviewed paper 10.3390/ijms21072594