Clostridioides difficile biofilms: A mechanism of persistence in the gut?

Abstract

Biofilms are structured bacterial communities encased in an extracellular matrix. The structure and complexity of biofilms depend on the microorganism and the local environment [1,2]. Biofilms form on tissues and foreign implants during human infections and confer pathogens resistance to drugs and immune responses, making biofilm-associated infections extremely difficult to treat [1]. Clostridioides difficile, a major healthcare-associated gastrointestinal pathogen, causes C. difficile infection (CDI), which is associated with high rates of recurrence, especially in the elderly [3]. CDI is strongly associated with long-term antibiotic therapy, which results in disruption of the native gut microbiota. In recent years, C. difficile biofilms have been considered to be important for persistence of the bacterium in the gut and for recurrent infections. Here we review the current knowledge on C. difficile biofilms in the context of the gut environment and infection. C. difficile forms biofilms in vitro Biofilm formation by C. difficile was first reported by Donelli and colleagues where they identified the role of polymicrobial biofilms in clogging of biliary stents using confocal and field emission scanning electron microscopy [4]. Soon after, biofilm formation by C. difficile strains of clinical origin (strains 630, R20291) on abiotic surfaces was reported, as quantitated by crystal violet staining [5,6]. Viable cell counts, as well as LIVE/DEAD viability staining showed that bacterial viability was higher in 1-to 3-day-old biofilms and decreased in 6-day-old biofilms [4-7]. C. difficile biofilms are multilayered, encased in a thick matrix composed of bacterial proteins, extracellular DNA (eDNA), and polysaccharide II; however, it is noteworthy that the composition and structure of biofilms are both time-and strain-dependent [5,7]. Numerous C. difficile factors which modulate biofilm formation have been identified, including pili, flagella proteins, the S-layer, Cwp84, quorum sensing, germination receptor SleC, and sporulation. Mutants deficient in stress-related proteins including the SOS response regulator, LexA, the RNA chaperone, Hfq, and the heat stress-associated chaperone, DnaK, have been associated with increased biofilm formation [8-10]. Interestingly, the toxins TcdA and TcdB were identified in the biofilm matrix of 3-and 6-day-old biofilms, suggesting that biofilms may play a role in C. difficile virulence [7]. Cyclic di-GMP (c-di-GMP) is thought to play an important role in the motile to sessile biofilm state shift through repression of flagellar synthesis and induction of pili [11]. In a recent global gene expression analysis of microfermentor biofilms, several genes controlled by the SinR-like regulators CD2214 and CD2215, including pilA1, were differentially expressed in biofilms, although pilA1 appeared to contribute to biofilm/ aggregate formation only in c-di-GMP overexpressing strains [12]. Thus, C. difficile forms complex biofilms in vitro which involves multiple regulatory pathways and several vir...

An osmotic laxative renders mice susceptible to prolonged Clostridioides difficile colonization and hinders clearance

“…One possible explanation for the prolonged C. difficile colonization in 5-day PEG treated mice, might be due to the bacteria's persistence in the mucosal compartment. In fact, it has been hypothesized that C. difficile biofilms may serve as reservoirs for recurrent infections (35) and C. difficile biofilms in the mucus layer were recently identified in patients as aggregates with Fusobacterium nucleatum (36). There was an interesting pattern of increased Enterobacteriaceae, Bacteroides, and C. difficile in both the stool and mucosal communities of PEG-treated mice suggesting a potential synergy.…”

Alimentary and Pharmaceutical Approach to Natural Antimicrobials against Clostridioides difficile Gastrointestinal Infection

“…The biofilm-forming capacity of C. difficile has significantly contributed to the increase in antibiotic resistance [ 16 , 17 ]. In fact, according to Semenyuk et al [ 18 ], C. difficile biofilms confer a 100-fold increase in metronidazole resistance [ 18 ].…”

“…It has been proven that the capacity of sessile bacteria to form biofilms in the mucus layer of the gut plays a fundamental role in gut health and disease. Although very little information has been published to date regarding the in vivo biofilm-forming capacity of C. difficile , it is well known that these multicellular structures could potentially protect bacteria from cellular immune responses and from antibiotics [ 16 , 17 ]. Moreover, the recurrence of CDI can be associated with biofilm persistence [ 17 ].…”

“…Although very little information has been published to date regarding the in vivo biofilm-forming capacity of C. difficile , it is well known that these multicellular structures could potentially protect bacteria from cellular immune responses and from antibiotics [ 16 , 17 ]. Moreover, the recurrence of CDI can be associated with biofilm persistence [ 17 ]. At present, among the most concerning unknown aspects of clostridial pathogenesis (gut colonization and infection progression) is the biofilm-forming capacity of C. difficile in vivo and how this multicellular intraspecific “dialogue” can interact with the host immune system [ 17 ].…”

“…Moreover, the recurrence of CDI can be associated with biofilm persistence [ 17 ]. At present, among the most concerning unknown aspects of clostridial pathogenesis (gut colonization and infection progression) is the biofilm-forming capacity of C. difficile in vivo and how this multicellular intraspecific “dialogue” can interact with the host immune system [ 17 ].…”