Do tetracyclines have the potential to reduce the risk of Clostridium difficile infection?

Clinical and Epidemiological Changes in French Soldiers After Deployment: Impact of Doxycycline Malaria Prophylaxis on Body Weight

BACKGROUND

Antibiotics are growth promotors used in animal farming. Doxycycline (DOXY) is a tetracycline antibiotic taken daily and continued 1 month after return to protect against malaria during travel and deployment in endemic areas. We evaluated DOXY impact on body weight in military international travelers.

MATERIEL AND METHODS

A prospective cohort analysis was conducted in 2016-2018, recruiting 170 French soldiers before a 4-month assignment overseas. Many clinical data including anthropometric measures by an investigator were collected before and after deployment. Weight gain was defined by an increase of 2% from baseline. The study protocol was supported by the French Armed Forces Health Services and approved by the French ethics committee (IRB no. 2015-A01961-48, ref promoter 2015RC0). Written, informed consent was obtained with signature from each volunteer before inclusion.

RESULTS

After deployment, 84 soldiers were followed up. Overall, 38/84 (45%) were deployed to Mali with DOXY malaria prophylaxis, and others were deployed to Iraq or Lebanon without malaria prophylaxis according to international recommendations. Body weight increased in 24/84 (30%), of whom 14/24 (58%) were exposed to DOXY. In bivariate analysis, DOXY had a positive but not significant effect on weight gain (P-value = .4). In the final logistic regression model (Fig. 3), weight gain after deployment positively correlated with an increase in waist circumference (odds ratio [OR] 1.23 with 95% CI [1.06-1.47]) suggesting fat gain; with sedentary work (OR 5.34; 95% CI [1.07-31.90]); and with probiotic intake (OR 5.27; 95% CI [1.51-20.40]). Weight impact of probiotics was more important when associated with DOXY intake (OR 6.86; 95% CI [1.52-38.1]; P-value = .016).

CONCLUSIONS

Doxycycline (DOXY) malaria prophylaxis during several months did not cause significant weight gain in soldiers. Further studies are required in older and less sportive traveling populations, and to investigate a cumulative effect over time and recurrent DOXY exposure. Doxycycline (DOXY) may enhance other growth-promoting factors including fatty food, sedentariness, and strain-specific probiotics contained in fermented dairy products which are also used as growth promotors.

Paeniclostridium sordellii and Clostridioides difficile encode similar and clinically relevant tetracycline resistance loci in diverse genomic locations

BACKGROUND

With the current rise of antibiotic resistance in bacteria, it is important to monitor the efficacy of antimicrobials in clinical use. Paeniclostridium sordellii (previously Clostridium sordellii) is a bacterial pathogen that causes human uterine infection after spontaneous or medically induced abortion, for which mortality rates approach 100%. Prophylactic antibiotics have been recommended for individuals undergoing medically-induced abortion, one of which is doxycycline, a member of the tetracycline antibiotic family. However, tetracycline resistance had not been well characterized in P. sordellii. This study therefore aimed to determine the levels of tetracycline resistance in P. sordellii isolates, and to identify associated loci and their genomic locations.

RESULTS

Using a MIC assay, five of 24 P. sordellii isolates were found to be resistant to tetracycline, minocycline, and importantly, doxycycline. Analysis of genome sequence data from 46 isolates found that phenotypically resistant isolates encoded a variant of the Clostridium perfringens tetracycline resistance determinant Tet P. Bioinformatic analysis and comparison of the regions surrounding these determinants found variation in the genomic location of Tet P among P. sordellii isolates. The core genome comparison of the 46 isolates revealed genetic diversity and the absence of dominant genetic types among the isolates. There was no strong association between geographic location of isolation, animal host or Tet P carriage with isolate genetic type. Furthermore, the analysis of the Tet P genotype revealed that Tet P is encoded chromosomally, or on one of two, novel, small plasmids, all consistent with multiple acquisition and recombination events. BLAST analysis of Clostridioides difficile draft genome sequences also identified a Tet P locus, the genomic location of which demonstrated an evolutionary relationship with the P. sordellii locus.

CONCLUSIONS

The Tet P determinant is found in variable genomic locations within diverse human and animal isolates of P. sordellii and C. difficile, which suggests that it can undergo horizontal transfer, and may disseminate tetracycline resistance between clostridial species. Doxycycline is a suggested prophylactic treatment for P. sordellii infections, however, a small sub-set of the isolates tested are resistant to this antibiotic. Doxycycline may therefore not be an appropriate prophylactic treatment for P. sordellii infections.