Human infections caused by Clostridium sordellii are rare but
severe, with mortality rates nearing 70%. In the case of intrauterine infections by C. sordellii
after childbirth, spontaneous abortion or medical abortion, mortality rates
approach 100%. Antibiotic treatment and prophylaxis are
the only therapeutic options available; however, knowledge regarding antibiotic
resistance of this organism is limited. Our study aimed to construct an
antibiotic resistance profile for 24 C. sordellii isolates to members of
a specific and clinically relevant family of antibiotics; the tetracyclines. Assays
to determine the Minimum Inhibitory Concentration (MIC) for the antibiotics
tetracycline, minocycline and doxycycline were performed on all isolates. Of
the 24 C. sordellii isolates tested, 5 (~20%) were found to be resistant
to all three antibiotics. To identify genes that may confer resistance to the
tetracyclines and their associated genomic location, we undertook a molecular
analysis of the resistant isolates. PCR and sequencing analysis found that a
homologue of the Clostridium perfringens TetP determinant was present in
each of the strains. Furthermore, Southern hybridisation analysis found that
the location of the TetP-like determinant in C. sordellii appeared to be
strain dependent. Genome sequencing of the tetracycline resistant C.
sordellii isolates showed that among three strains TetP appears to be
encoded on two different plasmids, while in the two remaining strains TetP
appears to be located chromosomally. In one of these strains, TetP may be
associated with a ~22.7 kb mobilisable element. These results suggest that the
mobility of antibiotic resistance determinants, such as TetP, may not be
limited to transfer among a single clostridal species, but more broadly among
the clostridial genus, which may result from cohabitation of these bacteria in
the gut of humans and animals.