Mechanistic Insights Into Vancomycin Resistance In Clostridioides Difficile

<p><em>C. difficile </em>is a nosocomial, opportunistic pathogen that has become more hypervirulent over the last decade. Vancomycin is currently a frontline antibiotic for the treatment of <em>C. difficile</em> infections. Yet, strains of <em>C. difficile</em> are becoming non-susceptible to vancomycin. Emergence of the vancomycin non-susceptible phenotype has led to various questions including: What resistance elements are present that might contribute to the phenotype? Are these elements located on the chromosome or a plasmid? Where did these elements originate from? To address these questions, whole genome sequence analysis was performed to survey genes that may be involved in the vancomycin non-susceptible phenotype. Bioinformatic analysis was used to answer whether putative vancomycin-resistance genes were chromosomal or plasmid based. Culture-dependent methods were used to detect enterococci from stools of patients from Texas and Kenya infected with <em>C. difficile</em> and this was supplemented with patient data to describe co-colonization in the gut and its effects on patients.</p> <p>The sequencing analysis revealed the presence of a putative <em>van </em>gene cluster in all isolates tested. The presence of vancomycin-resistance elements varied among the isolates and included: <em>vanRS, vanW, vanH, </em>and <em>vanZ</em>. <em>In silico </em>analysis of sequences suggested that the putative vancomycin-resistance genes were chromosomal. A high prevalence of enterococci and vancomycin-resistant enterococci (VRE) was observed in the stools of <em>C. difficile </em>patients from both Kenya and Texas. In addition, the presence of enterococci increased the duration of CDI symptoms and this might also promote selection of non-spore forming <em>C. difficile</em> isolates. Finally, high proportions of VRE and non-susceptible <em>C. difficile </em>isolates were found in the same stools, suggesting a potential source of resistance elements.</p> <p>Although rigorous functional analysis is needed to confirm the specific genes responsible for vancomycin non-susceptibility in <em>C. difficile</em>, the presence of vancomycin-resistance genes underlines a promising avenue for further experimentation. Knowing that the genes are likely chromosomal will help in downstream characterization of these genes. Given the correlation between vancomycin-resistant enterococci<em> </em>and the vancomycin non-susceptibility phenotype in <em>C. difficile, </em>and the shared epidemiology between the two bacteria, it is plausible that these resistance elements may have originated from <em>Enterococci </em>spp, however, further genetic analysis is needed to confirm this observation. Overall, this study has shed some light on the mechanism of vancomycin non-susceptibility in <em>C. difficile </em>and has highlighted avenues for further exploration. Moreover, the relationship between <em>Enterococci </em>spp. and <em>C. difficile </em>during infection has become clearer and might enhance future treatment strategies</p>

Name thesis:degree_name

Masters of Science (MS)

Level thesis:degree_level

Thesis (MS)

Year dc:date.available

2020

Authors dc:creator

• Mahmood, Ayesha
• <p>0000-0003-3038-161X</p>

Contributors dc:contributor

• Charles Darkoh, Ph.D.
• Cesar Arias, M.D., Ph.D.
• Anne-Marie Krachler, Ph.D.

• C. difficile
• vancomycin resistance
• enterococcus
• CDI
• Medicine and Health Sciences

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/1034

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-2086