Effect of sub-MIC of vancomycin and clindamycin alone and in combination with ceftazidime on Clostridium difficile surface layer protein A (slpA) gene expression

Faecal microbiota transplantation for Clostridioides difficile: mechanisms and pharmacology

Faecal microbiota transplantation (FMT) has emerged as a remarkably successful treatment for recurrent Clostridioides difficile infection that cannot be cured with antibiotics alone. Understanding the complex biology and pathogenesis of C. difficile infection, which we discuss in this Perspective, is essential for understanding the potential mechanisms by which FMT cures this disease. Although FMT has already entered clinical practice, different microbiota-based products are currently in clinical trials and are vying for regulatory approval. However, all these therapeutics belong to an entirely new class of agents that require the development of a new branch of pharmacology. Characterization of microbiota therapeutics uses novel and rapidly evolving technologies and requires incorporation of microbial ecology concepts. Here, we consider FMT within a pharmacological framework, including its essential elements: formulation, pharmacokinetics and pharmacodynamics. From this viewpoint, multiple gaps in knowledge become apparent, identifying areas that require systematic research. This knowledge is needed to help clinical providers use microbiota therapeutics appropriately and to facilitate development of next-generation microbiota products with improved safety and efficacy. The discussion here is limited to FMT as a representative of microbiota therapeutics and recurrent C. difficile as the indication; however, consideration of the intrinsic basic principles is relevant to this entire class of microbiota-based therapeutics.

Polymorphisms in the genes encoding surface associated proteins of Clostridioides difficile isolates

BACKGROUND

Although the diversity of Clostridioides difficile toxins have been extensively studied, little is known about the variation in the surface associated proteins (SAPs) which are important in early steps of bacterial colonization and infection. Here, we examined 65C. difficile isolates to identify polymorphisms in the genes encoding SAPs.

METHODS

PCR was used to amplify slpA, fliC, fliD, cwp66 and cwp84 genes, followed by sequencing. In addition, the antigenicity and immunogenicity properties of different types of SlpA, FliC, FliD, Cwp66 and Cwp84 proteins were predicted in-silico by VaxiJen and BcePred online servers.

RESULTS

The predominant slpA sequence type was gr-01 (42.37%), followed by hr-01 (11.86%) and 078-01 (10.16%). In addition, two new slpA subtypes of smz (smz-09-Ir and smz-010-Ir) and a new slpA sequence type (Ir-01) were identified among the isolates examined. Analysis of the nucleotide sequences of fliC, fliD, cwp66 and cwp84 genes revealed 7, 5,5,3 different sequence types, respectively. Insilico analysis of antigenicity of SAPs showed that FliC had the highest level of antigenicity whereas SlpA and Cwp66 proteins had the highest level of immunogenicity.

CONCLUSIONS

This study pointed to the nucleotide polymorphism in SAPs of C. difficile isolates and demonstrated noticeable diversity in antigenicity and immunogenicity of these proteins which need to be taken into consideration as promising therapeutic or vaccine targets.

Issues beyond resistance: inadequate antibiotic therapy and bacterial hypervirulence

The administration of antibiotics while critical for treatment, can be accompanied by potentially severe complications. These include toxicities associated with the drugs themselves, the selection of resistant organisms and depletion of endogenous host microbiota. In addition, antibiotics may be associated with less well-recognized complications arising through changes in the pathogens themselves. Growing evidence suggests that organisms exposed to antibiotics can respond by altering the expression of toxins, invasins and adhesins, as well as biofilm, resistance and persistence factors. The clinical significance of these changes continues to be explored; however, it is possible that treatment with antibiotics may inadvertently precipitate a worsening of the clinical course of disease. Efforts are needed to adjust or augment antibiotic therapy to prevent the transition of pathogens to hypervirulent states. Better understanding the role of antibiotic-microbe interactions and how these can influence disease course is critical given the implications on prescription guidelines and antimicrobial stewardship policies.

Organophosphate Ester, 2-Ethylhexyl Diphenyl Phosphate (EHDPP), Elicits Cytotoxic and Transcriptomic Effects in Chicken Embryonic Hepatocytes and Its Biotransformation Profile Compared to Humans

The effects of 2-ethylhexyl diphenyl phosphate (EHDPP) on cytotoxicity and mRNA expression, as well as its metabolism, were investigated using a chicken embryonic hepatocyte (CEH) assay. After incubation for 36 h, the lethal concentration 50 (LC₅₀) was 50 ± 11 μM, suggesting that EHDPP is one of a small cohort of highly toxic organophosphate esters (OPEs). By use of a ToxChip polymerase chain reaction (PCR) array, we report modulation of 6, 11, or 16/43 genes in CEH following exposure to 0.1, 1, or 10 μM EHDPP, respectively. The altered genes were from all nine biological pathways represented on the ToxChip including bile acids/cholesterol regulation, glucose metabolism, lipid homeostasis, and the thyroid hormone pathway. After incubation for 36 h, 92.5% of EHDPP was transformed, and one of its presumed metabolites, diphenyl phosphate (DPHP), only accounted for 12% of the original EHDPP concentration. Further screening by use of high-resolution mass spectrometry revealed a novel EHDPP metabolite, hydroxylated 2-ethylhexyl monophenyl phosphate (OH-EHMPP), which was also detected in a human blood pool. Additional EHDPP metabolites detected in the human blood pool included EHMPP and DPHP. Overall, this study provided novel information regarding the toxicity of EHDPP and identified a potential EHDPP metabolite, OH-EHMPP, in both avian species and humans.