Effects of ciprofloxacin on the expression and production of exotoxins by Clostridium difficile

Abstract

Hypervirulent BI/NAP1/027 strains of Clostridium difficile have been associated with increased mortality of C. difficile infection (CDI). The emergence of highly fluoroquinolone (FLQ)-resistant BI/NAP1/027 strains suggests that FLQ exposure may be a risk factor for CDI development. However, the mechanism for this is not clear. We compared the effects of subinhibitory concentrations of ciprofloxacin on Toxin A and B gene expression and protein production in recent (strain 039) and historical (strain 5325) BI/NAP1/027 clinical isolates with high-and low-level ciprofloxacin resistance, respectively. In the highly ciprofloxacin-resistant isolate (strain 039), ciprofloxacin significantly and dose-dependently increased Toxin A gene expression and shifted its expression to earlier in its growth cycle; TcdB gene expression also increased but was less sensitive to low-dose ciprofloxacin. Maximal Toxin A/B production (4 ng ml "1 ) was increased twofold and occurred significantly earlier than in the untreated control. In strain 5325, ciprofloxacin at 0.25¾MIC markedly increased both tcdA and tcdB expression but their temporal dynamics were unchanged. Maximal toxin production (250 ng ml "1 ) was reduced approximately threefold compared with that of the untreated control. These results demonstrate significant differences in ciprofloxacin-induced toxin gene expression and protein production among BI/ NAP1/027 isolates, and offer a new paradigm for FLQ-associated CDI caused by recent, highly antibiotic-resistant strains.

Effects of fluoroquinolone restriction (from 2007 to 2012) on Clostridium difficile infections: interrupted time-series analysis

“…19 Ciprofloxacin upregulates toxin gene expression in the hypervirulent NAPI strain of C. difficile that is highly resistant to fluoroquinolone. 20 The UK epidemic clones are markedly less susceptible to fluoroquinolones compared with the distinct stain. 21 In fact, resistance is common among prevalent ribotypes, e.g.…”

Synergistic Effects of Antimicrobial Peptides and Antibiotics against Clostridium difficile

“…Many studies have shown the effects of antibiotics on toxin production in C. difficile, but these were partly strain specific and therefore partially contradictory. Using ciprofloxacin at subinhibitory concentrations, Aldape et al demonstrated a significant and dose-dependent increase of toxin A gene expression and a shift of its expression to the earlier growth cycle in a highly ciprofloxacin-resistant isolate (17). TcdB gene expression was also increased but was less sensitive to lowdose ciprofloxacin.…”

Vaccines againstClostridium difficile

“…19,21,22 Although mechanisms that regulate toxin production are not completely elucidated, there are evidences that toxin synthesis is enhanced by several stimuli including metabolic stress, 23,24 temperature, 25 and sub-lethal doses of antibiotics. [26][27][28][29] Healthy individuals are generally able to mount a robust systemic immunity that limits gut damage induced by the toxins. 30,31 On the contrary, elderly or immuno-compromised subjects are prone to a series of symptoms whose severity ranges from mild diarrhea to fulminant pseudomembranous colitis.…”