Prevention of Clostridium difficile spore formation by sub-inhibitory concentrations of tigecycline and piperacillin/tazobactam

The role of single and mixed biofilms in Clostridioides difficile infection and strategies for prevention and inhibition

Clostridioides difficile infection (CDI) is a serious disease with a high recurrence rate. The single and mixed biofilms formed by C. difficile in the gut contribute to the formation of recurrent CDI (rCDI). In parallel, other gut microbes influence the formation and development of C. difficile biofilms, also known as symbiotic biofilms. Interactions between members within the symbiotic biofilm are associated with the worsening or alleviation of CDI. These interactions include effects on C. difficile adhesion and chemotaxis, modulation of LuxS/AI-2 quorum sensing (QS) system activity, promotion of cross-feeding by microbial metabolites, and regulation of intestinal bile acid and pyruvate levels. In the process of C. difficile biofilms control, inhibition of C. difficile initial biofilm formation and killing of C. difficile vegetative cells and spores are the main targets of action. The role of symbiotic biofilms in CDI suggested that targeting interventions of C. difficile-promoting gut microbes could indirectly inhibit the formation of C. difficile mixed biofilms and improved the ultimate therapeutic effect. In summary, this review outlines the mechanisms of C. difficile biofilm formation and summarises the treatment strategies for such single and mixed biofilms, aiming to provide new ideas for the prevention and treatment of CDI.

Association Between Common Empiric Antibiotic Regimens and Clostridioides Difficile Infection in Pediatric Appendicitis

BACKGROUND

Clostridioides Difficile Infection (CDI) is a serious antibiotic related complication that has been reported among children undergoing treatment of appendicitis. CDI likelihood amongst different empiric antibiotic regimens for appendicitis remains unclear but likely has important implications for antibiotic stewardship.

METHODS

A retrospective cohort study of the Pediatric Health Information System was used to examine patients ages 1 through 18 who received operative management of acute appendicitis. Common empiric antibiotic regimens 1) Ceftriaxone & Metronidazole (CM) 2) Piperacillin & Tazobactam (PT) and 3) Cefoxitin were compared. Study outcomes were CDI within 28 days post-appendectomy and 30-day post-appendectomy percutaneous drainage procedures. Subset analyses were repeated to only include hospitals that standardized empiric antibiotic choice.

RESULTS

Of 105,911 patients, 220 (0.21 %) developed CDI. CDI was more common in patients that received CM (CM 0.29 % vs PT 0.15 % vs Cefoxitin 0.18 %; P < 0.01). On adjusted analysis, PT was associated with a lower likelihood of CDI (OR, 0.48; 95%CI, 0.31-0.74) compared to CM which was consistent in hospitals with standardized antibiotic choice. Exposure to more unique antibiotic regimens (OR, 1.70; 95 % CI, 1.50-1.93) and higher total antibiotic days (OR, 1.17; 95 % CI 1.13-1.21) were associated with an increased likelihood of CDI. There was no significant difference in the likelihood of post-appendectomy percutaneous drainage between antibiotic regimens.

CONCLUSIONS

CDI is rare following appendectomy for pediatric appendicitis. While PT was associated with statistically lower rates of CDI compared to CM, antibiotic stewardship efforts to avoid mixed regimens and decrease overall antibiotic exposure warrant exploration.

LEVEL OF EVIDENCE

Level III.

Design, Synthesis, and Evaluation of Cephamycin-Based Antisporulation Agents targeting Clostridioides difficile

With the aim of discovering small molecule inhibitors of the sporulation process in Clostridioides difficile, we prepared a series of C-7 α-(4-substituted-1H-1,2,3-triazol-1-yl)acetamide analogues of cefotetan, a known inhibitor of the C. difficile sporulation-specific protein target CdSpoVD. These analogues were evaluated using both in vitro binding assays with CdSpoVD and antisporulation assays against C. difficile. Further design concepts were aided utilizing the predicted docking scores (DS) using both AlphaFold (AF) models, and a crystal structure of the CdSpoVD protein (PDB 7RCZ). Despite being 1 order of magnitude more potent as a sporulation inhibitor than cefotetan, in vivo studies on compound 6a in a murine-model of C. difficile infection demonstrated comparable spore shedding capabilities as cefotetan. Importantly, compound 6a had no concerning broad spectrum antibacterial activities, toxicity, or hemolytic activity and thus has potential for further drug development.

Review of the Impact of Biofilm Formation on Recurrent Clostridioides difficile Infection

Clostridioides difficile infection (CDI) may recur in approximately 10-30% of patients, and the risk of recurrence increases with each successive recurrence, reaching up to 65%. C. difficile can form biofilm with approximately 20% of the bacterial genome expressed differently between biofilm and planktonic cells. Biofilm plays several roles that may favor recurrence; for example, it may act as a reservoir of spores, protect the vegetative cells from the activity of antibiotics, and favor the formation of persistent cells. Moreover, the expression of several virulence genes, including TcdA and TcdB toxins, has been associated with recurrence. Several systems and structures associated with adhesion and biofilm formation have been studied in C. difficile, including cell-wall proteins, quorum sensing (including LuxS and Agr), Cyclic di-GMP, type IV pili, and flagella. Most antibiotics recommended for the treatment of CDI do not have activity on spores and do not eliminate biofilm. Therapeutic failure in R-CDI has been associated with the inadequate concentration of drugs in the intestinal tract and the antibiotic resistance of a biofilm. This makes it challenging to eradicate C. difficile in the intestine, complicating antibacterial therapies and allowing non-eliminated spores to remain in the biofilm, increasing the risk of recurrence. In this review, we examine the role of biofilm on recurrence and the challenges of treating CDI when the bacteria form a biofilm.

Antibacterial Effect of Lemongrass (Cymbopogon citratus) against the Aetiological Agents of Pitted Keratolyis

Pitted keratolysis (PK) is a bacterial skin infection mostly affecting the pressure-bearing areas of the soles, causing unpleasant symptoms. Antibiotics are used for therapy, but the emergence of antiobiotic resistance, makes the application of novel topical therapeutic agents necessary. The antibacterial effects of 12 EOs were compared in the first part of this study against the three known aetiological agents of PK (Kytococcus sedentarius, Dermatophilus congolensis and Bacillus thuringiensis). The results of the minimal inhibitory concentration, minimal bactericidal concentration and spore-formation inhibition tests revealed that lemongrass was the most effective EO against all three bacterium species and was therefore chosen for further analysis. Seventeen compounds were identified with solid-phase microextraction followed by gas chromatography–mass spectrometry (HS-SPME/GC-MS) analysis while thin-layer chromatography combined with direct bioautography (TLC-BD) was used to detect the presence of antibacterially active compounds. Citral showed a characteristic spot at the Rf value of 0.47, while the HS-SPME/GC-MS analysis of an unknown spot with strong antibacterial activity revealed the presence of α-terpineol, γ-cadinene and calamenene. Of these, α-terpineol was confirmed to possess an antimicrobial effect on all three bacterium species associated with PK. Our study supports the hypothesis that, based on their spectrum, EO-based formulations have potent antibacterial effects against PK and warrant further investigation as topical therapeutics.

Inactivation of the riboswitch-controlled GMP synthase GuaA in Clostridioides difficile is associated with severe growth defects and poor infectivity in a mouse model of infection

Clostridioides difficile is the main cause of nosocomial antibiotic-associated diarrhoea. There is a need for new antimicrobials to tackle this pathogen. Guanine riboswitches have been proposed as promising new antimicrobial targets, but experimental evidence of their importance in C. difficile is missing. The genome of C. difficile encodes four distinct guanine riboswitches, each controlling a single gene involved in purine metabolism and transport. One of them controls the expression of guaA, encoding a guanosine monophosphate (GMP) synthase. Here, using in-line probing and GusA reporter assays, we show that these riboswitches are functional in C. difficile and cause premature transcription termination upon binding of guanine. All riboswitches exhibit a high affinity for guanine characterized by K_d values in the low nanomolar range. Xanthine and guanosine also bind the guanine riboswitches, although with less affinity. Inactivating the GMP synthase (guaA) in C. difficile strain 630 led to cell death in minimal growth conditions, but not in rich medium. Importantly, the capacity of a guaA mutant to colonize the mouse gut was significantly reduced. Together, these results demonstrate the importance of de novo GMP biosynthesis in C. difficile during infection, suggesting that targeting guanine riboswitches with analogues could be a viable therapeutic strategy.

Opportunities for Nanomedicine in Clostridioides difficile Infection

Clostridioides difficile, a spore-forming bacterium, is a nosocomial infectious pathogen which can be found in animals as well. Although various antibiotics and disinfectants were developed, C. difficile infection (CDI) remains a serious health problem. C. difficile spores have complex structures and dormant characteristics that contribute to their resistance to harsh environments, successful transmission and recurrence. C. difficile spores can germinate quickly after being exposed to bile acid and co-germinant in a suitable environment. The vegetative cells produce endospores, and the mature spores are released from the hosts for dissemination of the pathogen. Therefore, concurrent elimination of C. difficile vegetative cells and inhibition of spore germination is essential for effective control of CDI. This review focused on the molecular pathogenesis of CDI and new trends in targeting both spores and vegetative cells of this pathogen, as well as the potential contribution of nanotechnologies for the effective management of CDI.

Risk factors and outcomes associated with the carriage of tigecycline- and vancomycin-resistant Enterococcus faecium

OBJECTIVES

Vancomycin-resistant E. faecium (VRE) is a common cause of healthcare-associated infections. The emergence of VRE with tigecycline resistance (TVRE) is increasing but its impact on patient outcome is still not well defined. This study aimed to assess risk factors for the acquisition of TVRE and of patient outcomes associated with TVRE carriage/infection.

METHODS

At the University Hospital Frankfurt, we conducted a matched pair TVRE-VRE analysis to identify risk factors for TVRE carriage. Bed-to-bed contacts and potential transmission routes were reconstructed. TVRE were whole-genome sequenced to confirm suspected transmission events and to identify tigecycline resistance mechanisms.

RESULTS

76 TVRE cases were identified between 02/2014-04/2017 and compared to VRE colonized or infected controls. TVRE carriage was associated with exposure to tigecycline, an increased rate of bloodstream infections (BSI) with VRE or Candida spp., and higher mortality. Whole-genome sequencing-based analysis of 24 TVRE provided evidence for transmissions of TVRE, also across different wards.

CONCLUSIONS

Tigecycline exposure is the main risk factor for TVRE carriage. VRE/TVRE- and Candida-BSI are associated with worse clinical outcome. Hospital transmission of TVRE may occur despite strict contact precautions, whereas both antimicrobial stewardship and infection control interventions are of high importance to prevent emergence and spread of TVRE.

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.

Transcriptome Analysis of the Clostridioides difficile Response to Different Doses of Bifidobacterium breve

Probiotics are widely used in the prevention of Clostridioides difficile infection (CDI). The precise dosage of probiotics is a challenge. In this study, Clostridioides difficile ATCC 9689 (CD) was exposed to different doses of Bifidobacterium breve (YH68). A transcriptomic analysis was performed on CD cells that were separately exposed to low or high doses of YH68 cell-free culture supernatant (CFCS; CDL; or CDH, respectively). The results showed that the inhibitory effect of YH68 (cell pellets or CFCS) on the growth and the damage to the cell membrane integrity of CD exhibited a dose-response relationship at the physiological level. At the transcriptional level, a large number of differentially expressed genes (DEGs) were concentrated in amino acid, carbohydrate, energy metabolism and membrane transport in CDL and CDH cells, suggesting that both doses of YH68-CFCS triggered a significant change in activities in these metabolic pathways. Importantly, a significant stimulation or suppression was found in the pathogenic pathways (quorum sensing, signal transduction, flagellar assembly, biofilm formation, and drug resistance) of CDL and CDH cells, whereas there were some differences between the two doses. For example, the expression levels of genes related to quorum sensing and signal transduction in CDH cells were suppressed significantly, whereas genes encoding toxin production and sporulation factors were enhanced; in CDL cells, the expression levels of genes associated with flagellar assembly and biofilm formation were suppressed, whereas genes associated with drug resistance were upregulated significantly. These results indicated that the inhibitory effect of YH68-CFCS against CD, especially in pathogenic and metabolic aspects, did not demonstrate a dose-response relationship at the transcriptional level.

Repurposing the Antiamoebic Drug Diiodohydroxyquinoline for Treatment of Clostridioides difficile Infections

Clostridioides difficile, the leading cause of nosocomial infections, is an urgent health threat worldwide. The increased incidence and severity of disease, the high recurrence rates, and the dearth of effective anticlostridial drugs have created an urgent need for new therapeutic agents. In an effort to discover new drugs for the treatment of Clostridioides difficile infections (CDIs), we investigated a panel of FDA-approved antiparasitic drugs against C. difficile and identified diiodohydroxyquinoline (DIHQ), an FDA-approved oral antiamoebic drug. DIHQ exhibited potent activity against 39 C. difficile isolates, inhibiting growth of 50% and 90% of these isolates at concentrations of 0.5 μg/ml and 2 μg/ml, respectively. In a time-kill assay, DIHQ was superior to vancomycin and metronidazole, reducing a high bacterial inoculum by 3 log₁₀ within 6 h. Furthermore, DIHQ reacted synergistically with vancomycin and metronidazole against C. difficile in vitro. Moreover, at subinhibitory concentrations, DIHQ was superior to vancomycin and metronidazole in inhibiting two key virulence factors of C. difficile, toxin production and spore formation. Additionally, DIHQ did not inhibit the growth of key species that compose the host intestinal microbiota, such as Bacteroides, Bifidobacterium, and Lactobacillus spp. Collectively, our results indicate that DIHQ is a promising anticlostridial drug that warrants further investigation as a new therapeutic for CDIs.

Repurposing a platelet aggregation inhibitor ticagrelor as an antimicrobial against Clostridioides difficile

Drug resistance in Clostridioides difficile becomes a public health concern worldwide, especially as the hypervirulent strains show decreased susceptibility to the first-line antibiotics for C. difficile treatment. Therefore, the simultaneous discovery and development of new compounds to fight this pathogen are urgently needed. In order to determinate new drugs active against C. difficile, we identified ticagrelor, utilized for the prevention of thrombotic events, as exhibiting potent growth-inhibitory activity against C. difficile. Whole-cell growth inhibition assays were performed and compared to vancomycin and metronidazole, followed by determining time-kill kinetics against C. difficile. Activities against biofilm formation and spore germination were also evaluated. Leakage analyses and electron microscopy were applied to confirm the disruption of membrane structure. Finally, ticagrelor's ability to synergize with vancomycin and metronidazole was determined using checkerboard assays. Our data showed that ticagrelor exerted activity with a MIC range of 20-40 µg/mL against C. difficile. This compound also exhibited an inhibitory effect on biofilm formation and spore germination. Additionally, ticagrelor did not interact with vancomycin nor metronidazole. Our findings revealed for the first time that ticagrelor could be further developed as a new antimicrobial agent for fighting against C. difficile.

Toxin A and B genes expression of Clostridium difficile in the sub-minimum inhibitory concentration of clindamycin, vancomycin and in combination with ceftazidime

BACKGROUND AND OBJECTIVES

Antibiotics prescribed for infections have diverse effects on microbiota and the pathogen Clostridium difficile (C. difficile) as the most important antibiotic-associated diarrhea. This study aims to determine the gene expression of toxins A and B at the transcription level in the sub-MIC of vancomycin (VAN), clindamycin (CLI), and ceftazidime (CAZ) alone and in combination.

MATERIALS AND METHODS

The MIC and fractional inhibitory concentration (FIC) of two C. difficile samples (a clinical isolate and ATCC 9689) were determined by microdilution and checkerboard microdilution methods, respectively. The total RNA was extracted from the medium inoculated with ∼10⁶ CFU/mL of fresh bacteria in the pre-reduced medium containing ½ MIC of antibiotics alone and ½ FIC of antibiotics in combination. Real-time PCR was performed by sybrGreen methods in triplicate, and the data were analyzed by the comparative ΔΔ^CT method.

RESULTS

All antibiotics except CAZ (alone and in combination) decreased the gene expression of toxins A and B within 24 hours. VAN and CLI reduced toxin gene expression within 24 and 48 hours. However, CAZ alone and in combination with VAN as well as CLI increased the gene expression of toxins A and B.

CONCLUSION

The results confirmed toxin gene transcription and toxin production are associated with the type of isolates and antibiotics, as well as the combined form of antibiotics. This could be the reason which can explain the occurrence of C. difficile infection among patients who were treated with the third generation of cephalosporins alone and in combination with another antibiotic in the form of combinational therapy.

A microbiota-generated bile salt induces biofilm formation in Clostridium difficile

Clostridium difficile is a major cause of nosocomial infections. Bacterial persistence in the gut is responsible for infection relapse; sporulation and other unidentified mechanisms contribute to this process. Intestinal bile salts cholate and deoxycholate stimulate spore germination, while deoxycholate kills vegetative cells. Here, we report that sub-lethal concentrations of deoxycholate stimulate biofilm formation, which protects C. difficile from antimicrobial compounds. The biofilm matrix is composed of extracellular DNA and proteinaceous factors that promote biofilm stability. Transcriptomic analysis indicates that deoxycholate induces metabolic pathways and cell envelope reorganization, and represses toxin and spore production. In support of the transcriptomic analysis, we show that global metabolic regulators and an uncharacterized lipoprotein contribute to deoxycholate-induced biofilm formation. Finally, Clostridium scindens enhances biofilm formation of C. difficile by converting cholate into deoxycholate. Together, our results suggest that deoxycholate is an intestinal signal that induces C. difficile persistence and may increase the risk of relapse.

Phenotypic Characterization of Non-toxigenic Clostridioides difficile Strains Isolated From Patients in Mexico

Clostridioides difficile is a Gram positive, sporulated, rod-shape, anaerobic pathogen responsible for nosocomial diarrhea and colitis, mainly in antibiotic treated patients. C. difficile produce two toxins responsible for disease, toxin A (TcdA) and toxin B (TcdB), although not all strains produce them. Non-toxigenic C. difficile (NTCD) strains are able to colonize the intestinal mucosa and are often isolated from asymptomatic individuals. NTCD are poorly studied, their evolutionary history has not been elucidated, and their relationship with illness remains controversial. The aim of this work was to analyze the phenotype of NTCD strains isolated from clinical cases in hospitals of México, and whether NTCD strains present characteristics that differentiate them from the toxigenic strains. Seventy-four C. difficile strains isolated from patients were tested for cytotoxicity and 14 were identified as NTCD strains. We analyzed phenotypical characteristics that are important for the biology of C. difficile like colony morphology, antibiotic resistance, motility, sporulation, and adherence. Strains were also genotyped to determine the presence of genes coding for TcdA, TcdB and binary toxin and ribotyped for 027 type. When compared with toxigenic strains, NTCD strains presented an enlarged branched colony morphology, higher resistance to metronidazole, and increased sporulation efficiency. This phenotype has been reported associated with mutations that regulates phenotypic characteristics like swimming, sporulation or adhesion. Our results show that phenotype of NTCD strains is heterogeneous but still present characteristics that differentiate them from toxigenic strains.

Risk factors for treatment failure in patients receiving β-lactam/β-lactamase inhibitor combinations for Enterobacteriaceae bloodstream infection: A retrospective, single-centre, cohort study

The aim of this study was to investigate risk factors for treatment failure in patients receiving in vitro-active therapy with β-lactam/β-lactamase inhibitor (BL/BLI) for Enterobacteriaceae bloodstream infection (E-BSI). This was a retrospective, single-centre study of patients diagnosed with E-BSI at an Italian centre over a 4-year period. Exclusion criteria were age <18 years, clinical data unavailable, polymicrobial BSI, failure to receive in vitro-active therapy and death within 72 h from drawing the index blood culture. Patients who received BL/BLI as appropriate empirical and/or definitive therapy for ≥50% of the total treatment duration were selected. The primary endpoint was all-cause 30-day mortality. The secondary endpoint was 90-day relapse. Of 1319 eligible patients, 835 were selected. A total of 714 received BL/BLI as appropriate empirical therapy, of whom 522 remained on BL/BLI as definitive therapy and 192 shifted to another antibiotic for <50% of the treatment duration; 121 received BL/BLI as definitive therapy only. Non-susceptibility to extended-spectrum cephalosporins (NS-ESCs) was detected in 207 episodes (24.8%). All-cause 30-day mortality was 6.8%. In multivariate analysis adjusted for NS-ESC, independent predictors of mortality were Charlson comorbidity index, septic shock, Proteus spp. and CVC-related BSI, whilst urinary source was a protective factor. The 90-day relapse rate was 4.2%. Immunosuppression was the main independent predictor for relapse. BL/BLI was the most common antibiotic administered to patients with E-BSI in this cohort. Among patients appropriately treated with BL/BLI, failure rates were low and were primarily associated with underlying diseases, clinical severity at BSI onset and infection source.

Single-cell electro-phenotyping for rapid assessment of Clostridium difficile heterogeneity under vancomycin treatment at sub-MIC (minimum inhibitory concentration) levels

Current methods for measurement of antibiotic susceptibility of pathogenic bacteria are highly reliant on microbial culture, which is time consuming (requires > 16 hours), especially at near minimum inhibitory concentration (MIC) levels of the antibiotic. We present the use of single-cell electrophysiology-based microbiological analysis for rapid phenotypic identification of antibiotic susceptibility at near-MIC levels, without the need for microbial culture. Clostridium difficile (C. difficile) is the single most common cause of antibiotic-induced enteric infection and disease recurrence is common after antibiotic treatments to suppress the pathogen. Herein, we show that de-activation of C. difficile after MIC-level vancomycin treatment, as validated by microbiological growth assays, can be ascertained rapidly by measuring alterations to the microbial cytoplasmic conductivity that is gauged by the level of positive dielectrophoresis (pDEP) and the frequency spectra for co-field electro-rotation (ROT). Furthermore, this single-cell electrophysiology technique can rapidly identify and quantify the live C. difficile subpopulation after vancomycin treatment at sub-MIC levels, whereas methods based on measurement of the secreted metabolite toxin or the microbiological growth rate can identify this persistent C. difficile subpopulation only after 24 hours of microbial culture, without any ability to quantify the subpopulation. The application of multiplexed versions of this technique is envisioned for antibiotic susceptibility screening.

Effect of Bifidobacterium breve in Combination With Different Antibiotics on Clostridium difficile

While combinations of probiotics with antibiotics have exhibited beneficial and adverse effects in the treatment of Clostridium difficile infection (CDI), no substantive explanation has been provided for these effects. In this study, C. difficile ATCC 9689 (CD) was treated with Bifidobacterium breve (YH68) in combination with five different antibiotics to explore the effects of the different combinations on C. difficile. Cell-free culture supernatant (CFCS) of YH68 was combined with metronidazole (MTR), vancomycin (VAN), clindamycin (CLI), ceftazidime (CAZ) or ampicillin (AMP) to treat CD. The plate counting method was used to determine the growth and spore production of CD, and cell damage was assessed by the measurement of extracellular ATP levels with a luminescence-based kit. The production of toxin A/B was measured with an ELISA kit. The gene expression levels of tcdA and tcdB in CD were evaluated by real-time qPCR. The CFCS of YH68 (3 × 109 CFU/mL) at 0.25 times the minimal inhibitory concentration (MIC) (0.25YH68) in combination with the five antibiotics exerted stronger inhibitory effects on the growth and spore production of CD than the same antibiotics in the absence of 0.25YH68, except 0.25YH68&MTR&, 0.25YH68&MTR&CAZ, and 0.25YH68&VAN&CLI. However, treatment with 0.25YH68&VAN, 0.25YH68&, 0.25YH68&MTR&CAZ, 0.25YH68&VAN&CAZ, 0.25YH68&VAN&, and 0.25YH68&CAZ& resulted in increased cell damage. In addition, the different combinations, except 0.25YH68&CLI, 0.25YH68&MTR& and 0.25YH68&VAN&CLI, dramatically reduced the production of toxin A/B in comparison with the effects of the same antibiotics in the absence of 0.25YH68. The gene expression levels of tcdA and tcdB in CD were lowered upon treatment with 0.25YH68 in combination with MTR, CLI, CAZ, MTR&CAZ, MTR&, CLI&CAZ, and CLI&, whereas the levels were enhanced by 0.25YH68 in combination with VAN, AMP, MTR&CLI, VAN&CLI, VAN&, and CAZ&. In summary, YH68 in combination with specific antibiotics could enhance the inhibitory effects of antibiotics against CD. In addition, the antagonistic effects between some antibiotics could be weakened by YH68.

Safety and preliminary efficacy of orally administered lyophilized fecal microbiota product compared with frozen product given by enema for recurrent Clostridium difficile infection: A randomized clinical trial

Background

Fecal microbiota transplantation (FMT) via colonoscopy or enema has become a commonly used treatment of recurrent C. difficile infection (CDI).

Aims

To compare the safety and preliminary efficacy of orally administered lyophilized microbiota product compared with frozen product by enema.

Methods

In a single center, adults with ≥ 3 episodes of recurrent CDI were randomized to receive encapsulated lyophilized fecal microbiota from 100–200 g of donor feces (n = 31) or frozen FMT from 100 g of donor feces (n = 34) by enema. Safety during the three months post FMT was the primary study objective. Prevention of CDI recurrence during the 60 days after FMT was a secondary objective. Fecal microbiome changes were examined in first 39 subjects studied.

Results

Adverse experiences were commonly seen in equal frequency in both groups and did not appear to relate to the route of delivery of FMT. CDI recurrence was prevented in 26 of 31 (84%) subjects randomized to capsules and in 30 of 34 (88%) receiving FMT by enema (p = 0.76). Both products normalized fecal microbiota diversity while the lyophilized orally administered product was less effective in repleting Bacteroidia and Verrucomicrobia classes compared to frozen product via enema.

Conclusions

The route of delivery, oral or rectal, did not influence adverse experiences in FMT. In preliminary evaluation, both routes appeared to show equivalent efficacy, although the dose may need to be higher for lyophilized product. Spore-forming bacteria appear to be the most important engrafting organisms in FMT by the oral route using lyophilized product.

Trial registration

ClinicalTrials.gov NCT02449174

The Effect of a Piperacillin/Tazobactam Shortage on Antimicrobial Prescribing and Clostridium difficile Risk in 88 US Medical Centers

Background

Anti-infective shortages are a pervasive problem in the United States. The objective of this study was to identify any associations between changes in prescribing of antibiotics that have a high risk for CDI during a piperacillin/tazobactam (PIP/TAZO) shortage and hospital-onset Clostridium difficile infection (HO-CDI) risk in 88 US medical centers.

Methods

We analyzed electronically captured microbiology and antibiotic use data from a network of US hospitals from July 2014 through June 2016. The primary outcome was HO-CDI rate and the secondary outcome was changes in antibiotic usage. We fit a Poisson model to estimate the risk of HO-CDI associated with PIP/TAZO shortage that were associated with increased high-risk antibiotic use while controlling for hospital characteristics.

Results

A total of 88 hospitals experienced PIP/TAZO shortage and 72 of them experienced a shift toward increased use of high-risk antibiotics during the shortage period. The adjusted relative risk (RR) of HO-CDI for hospitals experiencing a PIP/TAZO shortage was 1.03 (95% confidence interval [CI], .85-1.26; P = .73). The adjusted RR of HO-CDI for hospitals that both experienced a shortage and also showed a shift toward increased use of high-risk antibiotics was 1.30 (95% CI, 1.03-1.64; P < .05).

Conclusions

Hospitals that experienced a PIP/TAZO shortage and responded to that shortage by shifting antibiotic usage toward antibiotics traditionally known to place patients at greater risk for CDI experienced greater HO-CDI rates; this highlights an important adverse effect of the PIP/TAZO shortage and the importance of antibiotic stewardship when mitigating drug shortages.

Novel Antimicrobials for the Treatment of Clostridium difficile Infection

The current picture of Clostridium difficile infection (CDI) is alarming with a mortality rate ranging between 3% and 15% and a CDI recurrence rate ranging from 12% to 40%. Despite the great efforts made over the past 10 years to face the CDI burden, there are still gray areas in our knowledge on CDI management. The traditional anti-CDI antimicrobials are not always adequate in addressing the current needs in CDI management. The aim of our review is to give an update on novel antimicrobials for the treatment of CDI, considering the currently available evidences on their efficacy, safety, molecular mechanism of action, and their probability to be successfully introduced into the clinical practice in the near future. We identified, through a PubMed search, 16 novel antimicrobial molecules under study for CDI treatment: cadazolid, surotomycin, ridinilazole, LFF571, ramoplanin, CRS3123, fusidic acid, nitazoxanide, rifampin, rifaximin, tigecycline, auranofin, NVB302, thuricin CD, lacticin 3147, and acyldepsipeptide antimicrobials. In comparison with the traditional anti-CDI antimicrobial treatment, some of the novel antimicrobials reviewed in this study offer several advantages, i.e., the favorable pharmacokinetic and pharmacodynamic profile, the narrow-spectrum activity against CD that implicates a low impact on the gut microbiota composition, the inhibitory activity on CD sporulation and toxins production. Among these novel antimicrobials, the most active compounds in reducing spore production are cadazolid, ridinilazole, CRS3123, ramoplanin and, potentially, the acyldepsipeptide antimicrobials. These antimicrobials may potentially reduce CD environment spread and persistence, thus reducing CDI healthcare-associated acquisition. However, some of them, i.e., surotomycin, fusidic acid, etc., will not be available due to lack of superiority versus standard of treatment. The most CD narrow-spectrum novel antimicrobials that allow to preserve microbiota integrity are cadazolid, ridinilazole, auranofin, and thuricin CD. In conclusion, the novel antimicrobial molecules under development for CDI have promising key features and advancements in comparison to the traditional anti-CDI antimicrobials. In the near future, some of these new molecules might be effective alternatives to fight CDI.

High Prevalence and Genetic Diversity of Large phiCD211 (phiCDIF1296T)-Like Prophages in Clostridioides difficile

Clostridioides difficile (formerly Clostridium difficile) is a pathogenic bacterium displaying great genetic diversity. A significant proportion of this diversity is due to the presence of integrated prophages. Here, we provide an in-depth analysis of phiCD211, also known as phiCDIF1296T, the largest phage identified in C. difficile so far, with a genome of 131 kbp. It shares morphological and genomic similarity with other large siphophages, like phage 949, infecting Lactococcus lactis, and phage c-st, infecting Clostridium botulinum A PhageTerm analysis indicated the presence of 378-bp direct terminal repeats at the phiCD211 genome termini. Among striking features of phiCD211, the presence of several transposase and integrase genes suggests past recombination events with other mobile genetic elements. Several gene products potentially influence the bacterial lifestyle and fitness, including a putative AcrB/AcrD/AcrF multidrug resistance protein, an EzrA septation ring formation regulator, and a spore protease. We also identified a CRISPR locus and a cas3 gene. We screened 2,584 C. difficile genomes available and detected 149 prophages sharing ≥80% nucleotide identity with phiCD211 (5% prevalence). Overall, phiCD211-like phages were detected in C. difficile strains corresponding to 21 different multilocus sequence type groups, showing their high prevalence. Comparative genomic analyses revealed the existence of several clusters of highly similar phiCD211-like phages. Of note, large chromosome inversions were observed in some members, as well as multiple gene insertions and module exchanges. This highlights the great plasticity and gene coding potential of the phiCD211/phiCDIF1296T genome. Our analyses also suggest active evolution involving recombination with other mobile genetic elements.IMPORTANCEClostridioides difficile is a clinically important pathogen representing a serious threat to human health. Our hypothesis is that genetic differences between strains caused by the presence of integrated prophages could explain the apparent differences observed in the virulence of different C. difficile strains. In this study, we provide a full characterization of phiCD211, also known as phiCDIF1296T, the largest phage known to infect C. difficile so far. Screening 2,584 C. difficile genomes revealed the presence of highly similar phiCD211-like phages in 5% of the strains analyzed, showing their high prevalence. Multiple-genome comparisons suggest that evolution of the phiCD211-like phage community is dynamic, and some members have acquired genes that could influence bacterial biology and fitness. Our study further supports the relevance of studying phages in C. difficile to better understand the epidemiology of this clinically important human pathogen.

Impact and Time Course of Clostridium difficile Colonization in Very Low Birth Weight Infants

BACKGROUND

Clostridium difficile is a gram-positive, anaerobic spore-forming, toxin-producing bacillus, which is one of the most common causes for health care-associated infections. High colonization rates in clinically asymptomatic neonates and infants have been described, although most studies go back to the early 1980 and 1990s, and were carried out in term and late preterm infants.

OBJECTIVES

The aim of our study was to determine both the impact and time course of C. difficile colonization in a cohort of very low birth weight infants (VLBWI) in an era of PCR-based technologies for diagnosis.

METHODS

Stool samples of VLBWI were analyzed for the presence of C. difficile strains in regular intervals during the hospital stay by PCR ribotyping. Analysis was continued throughout the first 2 years of life.

RESULTS

A 32% C. difficile colonization rate during the first 2 years of life and an in-hospital colonization rate of 8% was found in a cohort of 190 VLBWI. C. difficile colonization occurred mainly in the first 6 months of life, which was similar to term neonates. In-hospital colonization accounted for only a small percentage of cases with no detection of hypervirulent strains. Also, C. difficile colonization was not related to an adverse outcome in this VLBWI cohort. Oral lactoferrin of bovine origin and treatment with piperacillin/tazobactam were negatively correlated with C. difficile colonization in our study.

CONCLUSIONS

C. difficile colonization in our cohort of VLBWI was significantly lower than has been described in the literature and was not related to an adverse outcome.

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

Clostridium difficile (C.difficile) infection is often established in the presence of antibiotics and probably antibiotics can influence surface layer protein A (slpA) expression as a colonization factor. The aim of this study is to evaluate the effect of vancomycin (VAN), clindamycin (CLI) alone and in combination with ceftazidime (CAZ) on slpA gene expression to determine whether such antibiotics can have any effect on slpA expression. About ∼10⁶ CFU/mL was inoculated to medium containing an appropriate concentration of antibiotics alone and in combination. After 24 and 48 h incubation under anaerobic condition, 3 mL of culture was excluded and centrifuged in 8000 × g per 3 min. The pellet was washed and used for RNA extraction. The RNA extraction, Dnase I treatment and cDNA synthesis was performed by RNA extraction, Dnase I, and cDNA synthesis kits, respectively. The real-time PCR were carried out by sybrGreen methods and data were analyzed based on comparative ΔΔC_T. All antibiotics alone and in combination, except VAN/CAZ in clinical isolate, decreased the level of slpA gene expression in the 24-h incubation. While the expression profile of slpA was different in the 48-h incubation period. The VAN and CLI decreased the slpA expression, although the template of expression is closed to control medium. CAZ alone and in combination increased slpA expression. C. difficile may down-regulate slpA expression in the early stages of growth in sub-inhibitory concentration of antibiotics. But, over time C. difficile increases or over expresses the slpA expression level. Consequently C. difficile binds strongly to epithelial cells and continues to survive in the presence of sub-MIC concentration of antibiotics. This effect is observed especially with regard to CAZ and probably other third generation cephalosporins or in combination therapy with VAN or CLI, which are prescribed in the clinic. CAZ can interfere with the anti-down regulatory feature of VAN, CLI, and maybe other antibiotics.

The role of tigecycline in the management of Clostridium difficile infection: a retrospective cohort study

OBJECTIVE

We aimed to compare the outcomes of patients with C.difficile infection (CDI) treated either with tigecycline associated with vancomycin, or with vancomycin alone.

METHODS

This single-centre retrospective cohort study included all adults hospitalized from September 2014 through August 2015 for symptomatic, incident CDI confirmed by polymerase chain reaction for C. difficile toxin in stools. The primary outcome was the rate of favourable outcome, defined as a composite of clinical response (resolution of symptoms without need for additional CDI therapy) and achieving discharge without CDI-related surgery or intensive care; a secondary outcome was CDI recurrence. We constructed a non-parsimonious logistic regression model to calculate a propensity score (PS) for those receiving tigecycline.

RESULTS

In all, 266 patients were included: 62 patients received both vancomycin and tigecycline, and 204 patients received vancomycin alone. The patients from the two groups were similar regarding demographics and comorbidities but patients in the tigecycline group had a more severe CDI. A favourable outcome in the tigecycline group versus the vancomycin group was found in 50/62 (81%) versus 193/204 (95%). We matched patients receiving tigecycline or not according to the PS and 86 patients (43 pairs) could be matched. The OR for favourable outcome with tigecycline in the matched analysis was 0.92 (95% CI 0.60-1.44; p 0.74). The rate of CDI recurrences was 8/62 (13%) in the tigecycline group versus 39/204 (19%) in the vancomycin group (p 0.2).

CONCLUSION

Adding tigecycline to CDI standard therapy did not increase the clinical cure nor reduce the rate of CDI recurrences.

Toxin production of Clostridium difficile in sub-MIC of vancomycin and clindamycin alone and in combination with ceftazidime

Toxin production in Clostridium difficile (C. difficile) is a key process for induction of diarrhea. Several factors such as sub-MIC of antibiotics impact on toxin production. The aim of this research is investigation of sub-minimum inhibitory concentration (sub-MIC) of vancomycin (VAN), clindamycin (CLI) separately and in combination with ceftazidime (CAZ) on toxin production in C. difficile. About ∼10⁶ colony forming units (CFU) from 18-h culture of C. difficile ATCC 9689 and clinical isolates A⁺/B⁺/CTD^-, were cultured anaerobically in the pre-reduced medium with appropriate concentration of separated and in combination antibiotics. After 24 and 48 h, 1 mL of culture was removed, centrifuged and the supernatant stored at-70 °C for later use. The evaluation of toxin production was carried out by the ELISA technique. All antibiotics alone and in combination formats inhibited toxin production over a period of 24 h. This effect is also observed in presence of VAN and CLI during a period of 48 h. Over a 4 h period, CAZ increased toxin production alone and in combination, especially with CLI. The data showed VAN and CLI decrease the level of toxins. In contrast, the CAZ not only increases the level of produced toxin, but also can interfere with VAN and CLI. Based on the results, combination therapy which is performed for treatment or prevention of other infections may cause toxin production and probably the severity of C. difficile AAD to increase.

A Review of Experimental and Off-Label Therapies for Clostridium difficile Infection

In spite of increased awareness and the efforts taken to optimize Clostridium difficile infection (CDI) management, with the limited number of currently available antibiotics for C. difficile the halt of this increasing epidemic remains out of reach. There are, however, close to 80 alternative treatment methods with controversial anti-clostridial efficacy or in experimental phase today. Indeed, some of these therapies are expected to become acknowledged members of the recommended anti-CDI arsenal within the next few years. None of these alternative treatment methods can respond in itself to all the major challenges of CDI management, which are primary prophylaxis in the susceptible population, clinical cure of severe cases, prevention of recurrences, and forestallment of asymptomatic C. difficile carriage and in-hospital spread. Yet, the greater the variety of treatment choices on hand, the better combination strategies can be developed to reach these goals in the future. The aim of this article is to provide a comprehensive summary of these experimental and currently off-label therapeutic options.

Direct Photolysis of Fluoroquinolone Antibiotics at 253.7 nm: Specific Reaction Kinetics and Formation of Equally Potent Fluoroquinolone Antibiotics

Three fluoroquinolone-to-fluoroquinolone antibiotic transformations were monitored during UV-C irradiation processes. In particular, the following reactions were observed: enrofloxacin-to-ciprofloxacin, difloxacin-to-sarafloxacin, and pefloxacin-to-norfloxacin. The apparent molar absorptivity and fluence-based pseudo-first-order rate constants for transformation of the six fluoroquinolones by direct photolysis at 253.7 nm were determined for the pH 2-12 range. These parameters were deconvoluted to calculate specific molar absorptivity and fluence-based rate constants for cationic, zwitterionic, and anionic fluoroquinolone species. For a typical disinfection fluence of 40 mJ/cm(2), the apparent transformation efficiencies were inflated by 2-8% when fluoroquinolone products were not considered; moreover, the overall transformation efficiencies at 400 mJ/cm(2) varied by up to 40% depending on pH. The three product antibiotics, namely ciprofloxacin, sarafloxacin, and norfloxacin, were found to be equally or more potent than the parent fluoroquinolones using an Escherichia coli-based assay. UV treatment of a solution containing difloxacin was found to increase antimicrobial activity due to formation of sarafloxacin. These results highlight the importance of considering antibiotic-to-antibiotic transformations in UV-based processes.

Ertapenem Prophylaxis Associated With an Increased Risk of Clostridium difficile Infection Among Surgical Patients

A case-control study was conducted to determine risk factors for hospital-onset Clostridium difficile infection among patients admitted to 2 surgical units. Ertapenem prophylaxis was significantly associated with C. difficile infection risk (odds ratio, 3.13 [95% CI, 1.13-8.68], P=.028) and may offer an antimicrobial stewardship target among surgical patients.

Effects of tigecycline and vancomycin administration on established Clostridium difficile infection

The glycylcycline antibiotic tigecycline was approved in 2005 for the treatment of complicated skin and soft tissue infections and complicated intra-abdominal infections. Tigecycline is broadly active against both Gram-negative and Gram-positive microorganisms, including Clostridium difficile. Tigecycline has a low MIC against C. difficile in vitro and thus may represent an alternate treatment for C. difficile infection (CDI). To assess the use of tigecycline for treatment of established CDI, 5- to 8-week-old C57BL/6 mice were colonized with C. difficile strain 630. After C. difficile colonization was established, mice (n = 10 per group) were treated with either a 5-day course of tigecycline (6.25 mg/kg every 12 h subcutaneously) or a 5-day course of vancomycin (0.4 mg/ml in drinking water) and compared to infected, untreated control mice. Mice were evaluated for clinical signs of CDI throughout treatment and at 1 week posttreatment to assess potential for disease development. Immediately following a treatment course, C. difficile was not detectable in the feces of vancomycin-treated mice but remained detectable in feces from tigecycline-treated and untreated control mice. Toxin activity and histopathological inflammation and edema were observed in the ceca and colons of untreated mice; tigecycline- and vancomycin-treated mice did not show such changes directly after treatment. One week after the conclusion of either antibiotic treatment, C. difficile load, toxin activity, and histopathology scores increased in the cecum and colon, indicating that C. difficile-associated disease occurred. In vitro growth studies confirmed that subinhibitory concentrations of tigecycline were able to suppress toxin activity and spore formation of C. difficile, whereas vancomycin did not. Taken together, these data show how tigecycline is able to alter C. difficile pathogenesis in a mouse model of CDI.

Tigecycline for the Treatment of Severe and Severe Complicated Clostridium difficile Infection

Introduction

Clostridium difficile infection (CDI) is a common cause of nosocomial diarrhea. Metronidazole and vancomycin are the primary treatment options for CDI, but increasing rates of antimicrobial resistance and severe, refractory disease have prompted the need for alternative agents. Tigecycline has previously demonstrated favorable in vitro activity against C. difficile isolates, but clinical data on its use in the treatment of CDI are severely lacking. The objective of this study was to describe our experience using tigecycline in the treatment of severe and severe complicated CDI.

Methods

This was a retrospective case series of hospitalized patients with severe and severe complicated CDI who were treated with tigecycline. Disease severity assessments were determined according to current practice guidelines. Diagnosis of toxigenic CDI was confirmed by polymerase chain reaction and patients were excluded if they received tigecycline for <48 h. Data were collected by review of the electronic medical record. The primary outcome was clinical cure. Secondary outcomes were sustained response, hospital mortality, and 28-day all-cause mortality.

Results

A total of 7 cases of severe and complicated CDI were reviewed. Intravenous tigecycline administered as a 100-mg loading dose followed by 50 mg twice daily resulted in clinical cure in 85.7% (n = 6/7) of cases. The majority of patients (n = 4/5) were treated with the novel triple therapy combination of tigecycline, vancomycin, and metronidazole and resulted in clinical cure in 80% (n = 4/5) cases. Sustained response at 28 days was 100% among evaluable cases (n = 5/5). Hospital mortality did not occur in any patients, and 28-day all-cause mortality was 28.6% (n = 2/7).

Conclusion

Tigecycline appears to be a reasonable addition to the therapeutic regimen in the treatment of severe or complicated CDI, including cases that are refractory to standard therapy. A prospective clinical trial confirming these observational findings is warranted.

Electronic supplementary material

The online version of this article (doi:10.1007/s40121-014-0050-x) contains supplementary material, which is available to authorized users.

Challenges and opportunities in the management of Clostridium difficile infection

Clostridium difficile infection (CDI) is increasing in all regions of the world where sought. There is no gold standard for diagnosis of CDI, with available tests having limitations. Prevention of CDI will be seen with antibiotic stewardship, improved disinfection of hospitals and nursing homes, chemo- and immuno-prophylaxis and next generation probiotics. The important therapeutic agents are oral vancomycin and fidaxomicin with metronidazole being used only in mild cases or when oral therapy cannot be given. Current therapy of CDI for 10 days is associated with high rate of recurrence that may be prevented by prolonging initial therapy. Future treatment strategies will focus on drugs that inhibit C. difficile, reduce toxin activity and inflammation in the gut, and improve colonic flora diversity.

Polymerase chain reaction ribotyping of Clostridium difficile isolates in Qatar: a hospital-based study

Background

Clostridium difficile infection (CDI) is not generally reported to public health authorities in the Middle East and its true prevalence remains largely unknown. The aims of this study were to determine the prevalence of CDI and its associated ribotypes among C. difficile isolates in Qatar. Influence of age and correlation with other risk factors e.g. proton pump inhibitor use, antibiotic use, existence of chronic conditions, etc was also investigated for CDI positive patients.

Methods

A total of 1,532 patients with suspected CDI were recruited from two hospitals between 2011 and 2012. C. difficile was identified using glutamate dehydrogenase (GDH) lateral flow assay and toxins A and B Enzyme Immunoassay (EIA). The C. difficile positive samples were then cultured for PCR-ribotyping.

Results

122 of the 1,532 (7.9%) samples from individual patients were identified as C.difficile positive; and 79 of these were viably cultured (~65%). From these, 36 different PCR ribotypes were isolated, of which strains 258 (6 [7.6%]), 01/014/046 (5 [6.3%]), and 011/053/056/107 (4 [5%]) were the most prevalent. The prevalence of PCR-ribotype 027 was 1.3% (n = 1). An age of ≥65 years and treatment with proton pump inhibitors correlated with higher frequency of CDI. Treatment with third generation cephalosporins (50 [41%]) and piperacillin/tazobactam antibiotics (55 [45.1%]) was most frequently associated with CDI.

Conclusion

The most common C. difficile ribotype identified in Qatar was 258, which is different from those found in North America, Europe and Asia. The prevalence of CDI was higher in Qatar than Europe; though comparable to other Middle Eastern countries. These findings underscore the importance of local surveillance to detect and control C. difficile infection.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2334-14-502) contains supplementary material, which is available to authorized users.

Tigecycline suppresses toxin A and B production and sporulation in Clostridium difficile

BACKGROUND

Clostridium difficile infection (CDI) is mediated by potent extracellular toxins and is spread largely via bacterial spores. We and others have shown that some antibiotics stimulate C. difficile toxin production in a strain-specific manner; however, the effects of newer anti-C. difficile antibiotics on this process remain to be investigated.

METHODS

The effects of the protein synthesis inhibitor tigecycline on sporulation and toxin A and toxin B production were compared in historical (strain 9689) and hypervirulent BI/NAP1/027 (strain 5325) isolates of C. difficile in vitro.

RESULTS

Tigecycline at 1/4× MIC stimulated an increased and earlier toxin A and/or B gene expression in both the historical and the hypervirulent strains, although a commensurate increase in toxin protein production was observed only in the 9689 strain. In fact, in the hypervirulent 5325 strain, toxin production was dramatically suppressed. By comparison, subinhibitory concentrations of vancomycin and metronidazole also stimulated increased protein toxin production by the historical, but not the hypervirulent, strain. In addition, tigecycline dose-dependently reduced viable spore production by both the 9689 and 5325 strains. Vancomycin treatment also suppressed spore formation in both C. difficile strains; however, metronidazole, while reducing spore formation in the 9689 strain, stimulated a near 2 log increase in spore production by the 5325 isolate.

CONCLUSIONS

In summary, these findings suggest that the treatment of CDI patients with tigecycline could effectively both control disease progression and limit its spread by disrupting sporulation.