PCR ribotypes of Clostridioides difficile across Texas from 2011 to 2018 including emergence of ribotype 255

Antibacterial activity of ibezapolstat against antimicrobial-resistant clinical strains of Clostridioides difficile

Antimicrobial resistance is emerging in clinical strains of Clostridioides difficile. Ibezapolstat (IBZ) is a DNA polymerase IIIC inhibitor that has completed phase II clinical trials. IBZ has potent in vitro activity against wild-type, susceptible strains but its effect on C. difficile strains with reduced susceptibility to metronidazole (MTZ), vancomycin (VAN), or fidaxomicin (FDX) has not been tested. The primary objective of this study was to test the antibacterial properties of IBZ against multidrug-resistant C. difficile strains. The in vitro activity, bactericidal, and time-kill activity of IBZ versus comparators were evaluated against 100 clinical strains of which 59 had reduced susceptibility to other C. difficile antibiotics. Morphologic changes against a multidrug resistance strain were visualized by light and scanning electron microscopy. The overall IBZ MIC50/90 values (µg/mL) for evaluated C. difficile strains were 4/8, compared with 2/4 for VAN, 0.5/1 for FDX, and 0.25/4 for MTZ. IBZ MIC50/90 values did not differ based on non-susceptibility to antibiotic class or number of classes to which strains were non-susceptible. IBZ bactericidal activity was similar to the minimum inhibitory concentration (MIC) and maintained in wild-type and non-susceptible strains. Time-kill assays against two laboratory wild-type and two clinical non-susceptible strains demonstrated sustained IBZ activity despite reduced killing by comparator antibiotics for IBZ and VAN non-susceptible strains. Microscopy visualized increased cell lengthening and cellular damage in multidrug-resistant strains exposed to IBZ sub-MIC concentrations. This study demonstrated the potent antibacterial activity of IBZ against a large collection of C. difficile strains including multidrug-resistant strains. This study highlights the therapeutic potential of IBZ against multidrug-resistant strains of C. difficile.

The Strain and the Clinical Outcome of Clostridioides difficile Infection: A Meta-analysis

Background

The association between bacterial strains and clinical outcomes in Clostridioides difficile infection (CDI) has yielded conflicting results across studies. We conducted a systematic review and meta-analyses to assess the impact of these strains.

Methods

Five electronic databases were used to identify studies reporting CDI severity, complications, recurrence, or mortality according to strain type from inception to June 2022. Random effect meta-analyses were conducted to assess outcome proportions and risk ratios (RRs).

Results

A total of 93 studies were included: 44 reported recurrences, 50 reported severity or complications, and 55 reported deaths. Pooled proportions of complications were statistically comparable between NAP1/BI/R027 and R001, R078, and R106. Pooled attributable mortality was 4.8% with a gradation in patients infected with R014/20 (1.7%), R001 (3.8%), R078 (5.3%), and R027 (10.2%). Higher 30-day all-cause mortality was observed in patients infected with R001, R002, R027, and R106 (range, 20%-25%).NAP1/BI/R027 was associated with several unfavorable outcomes: recurrence 30 days after the end of treatment (pooled RR, 1.98; 95% CI, 1.02-3.84); admission to intensive care, colectomy, or CDI-associated death (1.88; 1.09-3.25); and 30-day attributable mortality (1.96; 1.23-3.13). The association between harboring the binary toxin gene and 30-day all-cause mortality did not reach significance (RR, 1.6 [0.9-2.9]; 7 studies).

Conclusions

Numerous studies were excluded due to discrepancies in the definition of the outcomes and the lack of reporting of important covariates. NAP1/BI/R027, the most frequently reported and assessed strain, was associated with unfavorable outcomes. However, there were not sufficient data to reach significant conclusions on other strains.

Prevalence of diagnostically-discrepant Clostridioides difficile clinical specimens: insights from longitudinal surveillance

Background

Clostridioides difficile Infection (CDI) is a healthcare-associated diarrheal disease prevalent worldwide. A common diagnostic algorithm relies on a two-step protocol that employs stool enzyme immunoassays (EIAs) to detect the pathogen, and its toxins, respectively. Active CDI is deemed less likely when the Toxin EIA result is negative, even if the pathogen-specific EIA is positive for C. difficile. We recently reported, however, that low-toxin-producing C. difficile strains recovered from Toxin-negative ('discrepant') clinical stool specimens can be fully pathogenic, and cause lethality in a rodent CDI model. To document frequency of discrepant CDI specimens, and evaluate C. difficile strain diversity, we performed longitudinal surveillance at a Southern Arizona tertiary-care hospital.

Methods

Diarrheic stool specimens from patients with clinical suspicion of CDI were obtained over an eight-year period (2015-2022) from all inpatient and outpatient Units of a > 600-bed Medical Center in Southern Arizona. Clinical laboratory EIA testing identified C. difficile-containing specimens, and classified them as Toxin-positive or Toxin-negative. C. difficile isolates recovered from the stool specimens were DNA fingerprinted using an international phylogenetic lineage assignment system ("ribotyping"). For select isolates, toxin abundance in stationary phase supernatants of pure cultures was quantified via EIA.

Results

Of 8,910 diarrheic specimens that underwent diagnostic testing, 1733 (19.4%) harbored C. difficile. Our major findings were that: (1) C. difficile prevalence and phylogenetic diversity was stable over the 8-year period; (2) toxigenic C. difficile was recovered from 69% of clinically Tox-neg ('discrepant') specimens; (3) the six most prevalent USA ribotypes were recovered in significant proportions (>60%) from Tox-neg specimens; and (4) toxin-producing C. difficile recovered from discrepant specimens produced less toxin than strains of the same ribotype isolated from non-discrepant specimens.

Conclusion

Our study highlights the dominance of Toxin EIA-negative CDI specimens in a clinical setting and the high frequency of known virulent ribotypes in these specimens. Therefore, a careful reevaluation of the clinical relevance of diagnostically-discrepant specimens particularly in the context of missed CDI diagnoses and C. difficile persistence, is warranted.

Assessing the Feasibility of Employing a Combination of a Bacteriophage-Derived Endolysin and Spore Germinants to Treat Relapsing Clostridioides difficile Infection

Clostridioides difficile is a Gram-positive, anaerobic, spore-forming bacillus and is a major cause of healthcare-associated infections. Whereas the vegetative form of the pathogen is susceptible to treatment with antibiotics, its ability to persist in the gut as antibiotic-resistant spores means that reinfection can occur in cases were the individual fails to re-establish a protective microflora. Bacteriophages and their lysins are currently being explored as treatment options due to their specificity, which minimizes the disruption to the other members of the gut microflora that are protective. The feasibility of employing recombinant endolysins to target the vegetative form of C. difficile has been demonstrated in animal models. In this study, we cloned and expressed the enzyme active domain of LysCD6356 and confirmed its ability to lyse the vegetative forms of a diverse range of clinical isolates of C. difficile, which included members of the hypervirulent 027 ribotype. Lytic activity was adversely affected by calcium, which is naturally found in the gut and is released from the spore upon germination. Our results suggests that a strategy in which the triggering of spore germination is separated in time from the application of the lysin could be developed as a strategy to reduce the risk of relapsing C. difficile infections.

Sentinel surveillance and epidemiology of Clostridioides difficile in Denmark, 2016 to 2019

BackgroundSince 2008, Danish national surveillance of Clostridioides difficile has focused on binary toxin-positive strains in order to monitor epidemic types such as PCR ribotype (RT) 027 and 078. Additional surveillance is needed to provide a more unbiased representation of all strains from the clinical reservoir.AimSetting up a new sentinel surveillance scheme for an improved understanding of type distribution relative to time, geography and epidemiology, here presenting data from 2016 to 2019.MethodsFor 2─4 weeks in spring and autumn each year between 2016 and 2019, all 10 Danish Departments of Clinical Microbiology collected faecal samples containing toxigenic C. difficile. Isolates were typed at the national reference laboratory at Statens Serum Institut. The typing method in 2016-17 used tandem-repeat-sequence typing, while the typing method in 2018-19 was whole genome sequencing.ResultsDuring the study period, the sentinel surveillance scheme included ca 14-15% of all Danish cases of C. difficile infections. Binary toxin-negative strains accounted for 75% and 16 of the 20 most prevalent types. The most common sequence types (ST) were ST2/13 (RT014/020) (19.5%), ST1 (RT027) (10.8%), ST11 (RT078) (6.7%), ST8 (RT002) (6.6%) and ST6 (RT005/117) (5.1%). The data also highlighted geographical differences, mostly related to ST1 and temporal decline of ST1 (p = 0.0008) and the increase of ST103 (p = 0.002), ST17 (p = 0.004) and ST37 (p = 0.003), the latter three binary toxin-negative.ConclusionSentinel surveillance allowed nationwide monitoring of geographical differences and temporal changes in C. difficile infections in Denmark, including emerging types, regardless of binary toxin status.

Make It Less difficile: Understanding Genetic Evolution and Global Spread of Clostridioides difficile

Clostridioides difficile is an obligate anaerobic pathogen among the most common causes of healthcare-associated infections. It poses a global threat due to the clinical outcomes of infection and resistance to antibiotics recommended by international guidelines for its eradication. In particular, C. difficile infection can lead to fulminant colitis associated with shock, hypotension, megacolon, and, in severe cases, death. It is therefore of the utmost urgency to fully characterize this pathogen and better understand its spread, in order to reduce infection rates and improve therapy success. This review aims to provide a state-of-the-art overview of the genetic variation of C. difficile, with particular regard to pathogenic genes and the correlation with clinical issues of its infection. We also summarize the current typing techniques and, based on them, the global distribution of the most common ribotypes. Finally, we discuss genomic surveillance actions and new genetic engineering strategies as future perspectives to make it less difficile.

Isolation, molecular typing and antimicrobial resistance of Clostridium difficile in dogs and cats in Lanzhou city of Northwest China

Clostridium difficile infection (CDI) in human and animals belonged usually to antibiotic-associated diarrhea, ranging in severity from mild to life-threatening intestinal tract illnesses. This study aimed to isolation and characterization, toxin genes test, molecular typing, and drug sensitivity of Clostridium difficile (C. difficile) which were isolated from clinical diseased dogs and cats. A total of 247 clinical samples were collected from five animal hospitals in Lanzhou City of Northwest China, of which dogs and cats accounted for 74.9% (185/247) and 25.1% (62/247), respectively. We successfully identified 24 C. difficile strains by 16S rRNA and Matrix-Assisted Laser Desorption/Ionization Time of Fight Mass Spectroscopy (MALDI-TOF-MS). 10.3% (19/185) of dogs and 8.1% (5/62) of cats were positive for C. difficile. Among them, 16 strains were toxic and 8 were non-toxic, with a toxic rate of 57.9% (11/19) in dogs and 100% (5/5) in cats. A total of 10 STs and 10 RTs were identified in this study. The percentages of ST42 (RT106) and ST2 (RT014/LW01) among 16 toxic strains were 41.7 and 12.5%, respectively. However, ST3 (RT001), ST1 (RT027), ST133 (LW04), and ST-UN (LW04) had only one strain. ST42 (RT106) was the most common genotype and RT027 strain was first isolated in China from pets. Antimicrobial susceptibility test showed that isolates were extremely sensitive to vancomycin and metronidazole but were resistant to erythromycin and ciprofloxacin. The drug resistant rates to clindamycin, levofloxacin, moxifloxacin and meropenem were 62.5, 20.8, 16.7, and 8.3%, respectively. In conclusion, C. difficile was quietly prevalent in dogs and cats in Lanzhou city with RT106 and RT014 as the main ribotypes. The CDI in pets should be paying more attention and further studies are needed.

Efficacy, Safety, Pharmacokinetics, and Microbiome Changes of Ibezapolstat in Adults with Clostridioides difficile Infection: A Phase 2a Multicenter Clinical Trial

Background

This study was the first human validation of the gram-positive bacterial DNA polymerase IIIC target in patients with Clostridioides difficile infection. The primary objectives were to assess clinical cure rates and adverse events (AEs). Secondary objectives were to evaluate plasma/fecal pharmacokinetics, microbiologic eradication, microbiome and bile acid effects, and sustained clinical cure (SCC) with ibezapolstat.

Methods

This single-arm, open-label, phase 2a study enrolled adults with C. difficile infection at 4 US centers. Patients received ibezapolstat 450 mg orally every 12 hours for 10 days and followed for an additional 28 days to assess study objectives.

Results

Ten patients with a mean (standard deviation [SD]) age of 49 [15] years were enrolled. Seven AEs were reported classified as mild-moderate. Plasma levels of ibezapolstat ranged from 233 to 578 ng/mL while mean (SD) fecal levels were 416 (494) µg/g stool by treatment day 3 and >1000 µg/g stool by days 8–10. A rapid increase in alpha diversity in the fecal microbiome was noted after starting ibezapolstat therapy, which was maintained after completion of therapy. A proportional decrease in Bacteroidetes phylum was observed (mean change [SD], −10.0% [4.8%]; P = .04) with a concomitantly increased proportion of Firmicutes phylum (+14.7% [5.4%]; P = .009). Compared with baseline, total primary bile acids decreased by a mean (SD) of 40.1 (9.6) ng/mg stool during therapy (P < .001) and 40.5 (14.1) ng/mg stool after completion of therapy (P = .007). Rates of both initial clinical cure and SCC at 28 days were 100% (10 of 10 patients).

Conclusions

In this phase 2a study, 10 of 10 patients achieved SCC, demonstrated favorable pharmacokinetics, minimal AEs, and beneficial microbiome and bile acids results. These results support continued clinical development.

Enteric Organisms Detected in Feces of Dogs With Bloody Diarrhea: 45 Cases

Bloody diarrhea is a common condition in dogs, but studies evaluating the enteropathogens involved specifically in adult dogs are scarce. In the present study, stool samples from 45 adult dogs with bloody diarrhea were evaluated for the four enteric organisms mainly reported in these cases: canine parvovirus type 2 (CPV-2), Clostridioides difficile, Clostridium perfringens, and Salmonella spp. In addition, the samples were also tested for coronavirus, rotavirus, Giardia spp., and Escherichia coli pathotypes to provide a better understanding of possible co-occurrence. Vaccination status, diet, and clinical outcome were also obtained when available. CPV-2b was identified in 17 dogs (37.8%), being the most frequent cause of bloody diarrhea, including completely vaccinated adult dogs. Toxigenic C. difficile and C. perfringens netF⁺ were detected in 6 (13.3%) and 5 (11.1%) dogs, in some cases in a co-occurrence with other enteric organisms. Three fatal cases of salmonellosis were identified in dogs fed a raw meat-based diet, raising the risks associated with this increasing practice.

Comparative clinical outcomes evaluation of hospitalized patients infected with Clostridioides difficile ribotype 106 vs. other toxigenic strains

BACKGROUND

Although Clostridioides difficile surveillance often identifies emerging strains, clinical outcome evaluations are rarely performed. Ribotype (RT) 106 is a commonly isolated C. difficile strain worldwide; however, studies investigating RT 106 clinical outcomes are limited. The purpose of this study was to investigate clinical outcomes of RT 106 infections compared with two other endemic strains of varying virulence.

METHODS

This multicenter study evaluated adults hospitalized with C. difficile infection (CDI). C. difficile samples underwent PCR ribotyping and patients infected with RT 106 were compared to patients infected with a known hypervirulent strain (RT 027) and a strain associated with less virulence (RT 014-020). Electronic medical records were reviewed by blinded investigators to assess the primary outcome of poor clinical outcome (composite of initial clinical failure, discharge to a higher level of care, 90-day CDI recurrence, and CDI-contributable mortality).

RESULTS

A total of 396 patients with CDI were identified (RT 106, 32.3%; RT 027, 29.3%; RT 014-020, 38.3%). Patients infected with RT 014-020 less often experienced a poor clinical outcome (40%) compared with RT 106 (56%) and RT 027 (65%) infection (P < 0.0001). After controlling for covariates and using RT 014-020 as a comparator, patients infected with RT 106 (OR, 2.25; 95% CI, 1.36-3.73) or RT 027 (OR, 2.56; 95% CI, 1.52-4.31) had higher odds of poor clinical outcome. Using RT 027 as the comparator, only RT 014-020 was associated with lower odds of poor clinical outcome (OR, 0.42; 95% CI, 0.27-0.65).

CONCLUSION

This study demonstrated that the emergent C. difficile RT 106 was associated with increased rates of poor clinical outcomes compared to RT 014-020 and comparable poor clinical outcomes to RT 027. These findings can help to better understand the clinical significance of this and future emerging ribotypes.

Clostridioides difficile Infection in Cancer and Immunocompromised Patients: Relevance of a Two-step Diagnostic Algorithm and Infecting Ribotypes on Clinical Outcomes

BACKGROUND

Patients with cancer are particularly vulnerable to Clostridioides difficile infection (CDI). Guidelines recommend a two-step diagnostic algorithm to differentiate carriers from CDI; however, there are limited data for this approach while including other confounding risk factors for diarrhea such as radiation, cytotoxic chemotherapy, and adoptive cell based therapies.

METHODS

We conducted a prospective, non-interventional, single center, cohort study of cancer patients with acute diarrhea and C. difficile, identified in stools by nucleic acid amplification tests (NAAT) and culture. Fecal toxin A/B was detected by enzyme immunoassay (EIA) and isolates were ribotyped using 16s rRNA fluorescent sequencing. Patients were followed for 90 days to compare outcomes according to malignancy type, infecting ribotype, and EIA status.

RESULTS

We followed 227 patients with a positive NAAT. Of these, 87% were hospitalized and 83% had an active malignancy. EIA was confirmed positive in 80/227 (35%) of patients. Those with EIA+ were older (60 ± 18 years vs 54 ± 19 years., P = .01), more likely to fail therapy [24/80 (30%) vs 26/147 (18%), P = .04] and experience recurrence [20/80 (25%) vs 21/147(14%), P < .05]. We found a low prevalence (22%) of ribotypes historically associated with poor outcomes (002, 018, 027, 56, F078-126, 244) but their presence were associated with treatment failure [17/50 (34%) vs 33/177 (19%), P = .02].

CONCLUSIONS

When compared to cancer patients with fecal NAAT+/EIA-, patients with NAAT+/EIA+ CDI are less likely to respond to therapy and more likely to experience recurrence, particularly when due to ribotypes associated with poor outcomes.

A multisite genomic epidemiology study of Clostridioides difficile infections in the USA supports differential roles of healthcare versus community spread for two common strains

Clostridioides difficile is the leading cause of healthcare-associated infectious diarrhoea. However, it is increasingly appreciated that healthcare-associated infections derive from both community and healthcare environments, and that the primary sites of C. difficile transmission may be strain-dependent. We conducted a multisite genomic epidemiology study to assess differential genomic evidence of healthcare vs community spread for two of the most common C. difficile strains in the USA: sequence type (ST) 1 (associated with ribotype 027) and ST2 (associated with ribotype 014/020). We performed whole-genome sequencing and phylogenetic analyses on 382 ST1 and ST2 C. difficile isolates recovered from stool specimens collected during standard clinical care at 3 geographically distinct US medical centres between 2010 and 2017. ST1 and ST2 isolates both displayed some evidence of phylogenetic clustering by study site, but clustering was stronger and more apparent in ST1, consistent with our healthcare-based study more comprehensively sampling local transmission of ST1 compared to ST2 strains. Analyses of pairwise single-nucleotide variant (SNV) distance distributions were also consistent with more evidence of healthcare transmission of ST1 compared to ST2, with 44 % of ST1 isolates being within two SNVs of another isolate from the same geographical collection site compared to 5.5 % of ST2 isolates (P-value=<0.001). Conversely, ST2 isolates were more likely to have close genetic neighbours across disparate geographical sites compared to ST1 isolates, further supporting non-healthcare routes of spread for ST2 and highlighting the potential for misattributing genomic similarity among ST2 isolates to recent healthcare transmission. Finally, we estimated a lower evolutionary rate for the ST2 lineage compared to the ST1 lineage using Bayesian timed phylogenomic analyses, and hypothesize that this may contribute to observed differences in geographical concordance among closely related isolates. Together, these findings suggest that ST1 and ST2, while both common causes of C. difficile infection in hospitals, show differential reliance on community and hospital spread. This conclusion supports the need for strain-specific criteria for interpreting genomic linkages and emphasizes the importance of considering differences in the epidemiology of circulating strains when devising interventions to reduce the burden of C. difficile infections.

Temporal Variations in Patterns of Clostridioides difficile Strain Diversity and Antibiotic Resistance in Thailand

Clostridioides difficile has been recognized as a life-threatening pathogen that causes enteric diseases, including antibiotic-associated diarrhea and pseudomembranous colitis. The severity of C. difficile infection (CDI) correlates with toxin production and antibiotic resistance of C. difficile. In Thailand, the data addressing ribotypes, toxigenic, and antimicrobial susceptibility profiles of this pathogen are scarce and some of these data sets are limited. In this study, two groups of C. difficile isolates in Thailand, including 50 isolates collected from 2006 to 2009 (THA group) and 26 isolates collected from 2010 to 2012 (THB group), were compared for toxin genes and ribotyping profiles. The production of toxins A and B were determined on the basis of toxin gene profiles. In addition, minimum inhibitory concentration of eight antibiotics were examined for all 76 C. difficile isolates. The isolates of the THA group were categorized into 27 A⁻B⁺CDT⁻ (54%) and 23 A^-B^-CDT^- (46%), while the THB isolates were classified into five toxigenic profiles, including six A⁺B⁺CDT⁺ (23%), two A⁺B⁺CDT⁻ (8%), five A⁻B⁺CDT⁺ (19%), seven A⁻B⁺CDT⁻ (27%), and six A⁻B⁻CDT⁻ (23%). By visually comparing them to the references, only five ribotypes were identified among THA isolates, while 15 ribotypes were identified within THB isolates. Ribotype 017 was the most common in both groups. Interestingly, 18 unknown ribotyping patterns were identified. Among eight tcdA-positive isolates, three isolates showed significantly greater levels of toxin A than the reference strain. The levels of toxin B in 3 of 47 tcdB-positive isolates were significantly higher than that of the reference strain. Based on the antimicrobial susceptibility test, metronidazole showed potent efficiency against most isolates in both groups. However, high MIC values of cefoxitin (MICs 256 μg/mL) and chloramphenicol (MICs ≥ 64 μg/mL) were observed with most of the isolates. The other five antibiotics exhibited diverse MIC values among two groups of isolates. This work provides evidence of temporal changes in both C. difficile strains and patterns of antimicrobial resistance in Thailand.

Systems biology evaluation of refractory Clostridioides difficile infection including multiple failures of fecal microbiota transplantation

BACKGROUND

Fecal microbiota transplantation (FMT) aims to cure Clostridioides difficile infection (CDI) through reestablishing a healthy microbiome and restoring colonization resistance. Although often effective after one infusion, patients with continued microbiome disruptions may require multiple FMTs. In this N-of-1 study, we use a systems biology approach to evaluate CDI in a patient receiving chronic suppressive antibiotics with four failed FMTs over two years.

METHODS

Seven stool samples were obtained between 2016-18 while the patient underwent five FMTs. Stool samples were cultured for C. difficile and underwent microbial characterization and functional gene analysis using shotgun metagenomics. C. difficile isolates were characterized through ribotyping, whole genome sequencing, metabolic pathway analysis, and minimum inhibitory concentration (MIC) determinations.

RESULTS

Growing ten strains from each sample, the index and first four recurrent cultures were single strain ribotype F078-126, the fifth was a mixed culture of ribotypes F002 and F054, and the final culture was ribotype F002. One single nucleotide polymorphism (SNP) variant was identified in the RNA polymerase (RNAP) β-subunit RpoB in the final isolated F078-126 strain when compared to previous F078-126 isolates. This SNV was associated with metabolic shifts but phenotypic differences in fidaxomicin MIC were not observed. Microbiome differences were observed over time during vancomycin therapy and after failed FMTs.

CONCLUSION

This study highlights the importance of antimicrobial stewardship in patients receiving FMT. Continued antibiotics play a destructive role on a transplanted microbiome and applies selection pressure for resistance to the few antibiotics available to treat CDI.

Impact of the introduction of nucleic acid amplification testing on Clostridioides difficile detection and ribotype distribution in Wales

OBJECTIVES

To determine the impact of the 2018 introduction of nucleic acid amplification tests (NAATs) for C. difficile detection on the laboratory diagnosis of C. difficile infection (CDI), and the distribution of C. difficile ribotypes.

METHODS

A retrospective analysis of five years (2015-2019) of C. difficile diagnostic laboratory and PCR ribotyping test results.

RESULTS

A total of 255,104 diagnostic results, from 136,353 patients were analysed: 199,794 samples where glutamate dehydrogenase (GDH) was used as the primary screen; and 55,310 where NAATs were employed. An overall decrease in frontline positivity from 2015 to 2019 (10.3% [n = 5017] to 6% [n = 3190] - p < 0.0001) was observed, despite an increase in the number of samples tested (48,778 to 52,839). NAAT positivity was lower than GDH (p < 0.0001) for the two years where it was implemented. The variance was accounted for by increased overall C. difficile isolation and reduced toxin negative strain culture from NAAT positive samples (p < 0.0001). Ribotype distribution (6546 samples) remained stable with decreasing RT27 isolation in each year except 2017 (p < 0.0001). RT78 was associated with toxin A/B EIA positivity (p < 0.0001).

CONCLUSIONS

Use of NAAT for the detection of C. difficile, as part of a 2-step algorithm, has not led to an increase in CDI laboratory diagnostic test positivity. In spite of ribotype distribution being comparable for screening in toxin A/B positive samples, there is a significantly greater correlation between NAAT positivity and culture of toxigenic strains compared to GDH.

Assessment of Kidney Injury as a Severity Criteria for Clostridioides Difficile Infection

BACKGROUND

The Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA) revised their Clostridioides difficile infection (CDI) severity classification criteria in 2017 to include an absolute serum creatinine (SCr) value above a threshold (≥1.5 mg/dL) rather than a relative increase from baseline (≥1.5 times the premorbid level). To date, how to best define kidney injury as a CDI disease severity marker has not been validated to assess severe outcomes associated with CDI.

METHODS

This multicenter cohort study included adult hospitalized patients with CDI. Patients were assessed for the presence of acute kidney injury (AKI), chronic kidney disease (CKD), and CDI severity using the 2010 and 2017 IDSA/SHEA CDI guidelines. Primary outcome was all-cause inpatient mortality.

RESULTS

The final study cohort consisted of 770 CDI episodes from 705 unique patients aged 65 ± 17 years (female, 54%; CKD, 36.5%; AKI, 29.6%). Eighty-two episodes (10.6%) showed discordant severity classification results due to the inclusion of more patients with preexisting CKD in the severe disease category using an absolute SCr threshold criterion. The absolute SCr criterion better correlated with all-cause mortality (odds ratio [OR], 4.04; 95% confidence interval [CI], 1.76-9.28; P = .001) than the relative increase in SCr (OR, 1.34; 95% CI, 0.62-2.89; P = .46). This corresponded to an increased likelihood of the 2017 CDI severity classification criteria to predict mortality (OR, 5.33; 95% CI, 1.81-15.72; P = .002) compared with the 2010 criteria (OR, 2.71; 95% CI, 1.16-6.32; P = .02).

CONCLUSIONS

Our findings support the 2017 IDSA/SHEA CDI severity classification criteria of a single pretreatment SCr in future CDI guideline updates.

In vitro activity of eravacycline against common ribotypes of Clostridioides difficile

Background

Eravacycline is a novel synthetic fluorocycline antibacterial approved for complicated intra-abdominal infections.

Objectives

The purpose of this study was to assess the in vitro activities of eravacycline and comparator antibiotics against contemporary clinical isolates of Clostridioides difficile representing common ribotypes, including isolates with decreased susceptibility to metronidazole and vancomycin.

Methods

Clinical C. difficile strains from six common or emerging ribotypes were used to test the in vitro activities of eravacycline and comparator antibiotics (fidaxomicin, vancomycin and metronidazole) by broth microdilution. In addition, MBC experiments, time–kill kinetic studies and WGS experiments were performed.

Results

A total of 234 isolates were tested, including ribotypes RT001 (n = 37), RT002 (n = 41), RT014-020 (n = 39), RT027 (n = 42), RT106 (n = 38) and RT255 (n = 37). MIC_50/90 values were lowest for eravacycline (≤0.0078/0.016 mg/L), followed by fidaxomicin (0.016/0.063 mg/L), metronidazole (0.25/1.0 mg/L) and vancomycin (2.0/4.0 mg/L). MBCs were lower for eravacycline compared with vancomycin for all ribotypes tested. Both vancomycin and eravacycline demonstrated bactericidal killing, including for epidemic RT027. The presence of the tetM or tetW resistance genes did not affect the MIC of eravacycline.

Conclusions

This study demonstrated potent in vitro activity of eravacycline against a large collection of clinical C. difficile strains that was not affected by ribotype, susceptibility to vancomycin or the presence of certain tet resistance genes. Further development of eravacycline as an antibiotic to be used in patients with Clostridioides difficile infection is warranted.

In Vitro Activity of Omadacycline, a New Tetracycline Analog, and Comparators against Clostridioides difficile

Omadacycline is a potent aminomethylcycline with in vitro activity against Gram-positive, Gram-negative, and anaerobic bacteria. Preliminary data demonstrated that omadacycline has in vitro activity against Clostridioides difficile; however, large-scale in vitro studies have not been done. The purpose of this study was to assess the in vitro susceptibility of omadacycline and comparators on a large biobank of clinical C. difficile isolates.

Omadacycline is a potent aminomethylcycline with in vitro activity against Gram-positive, Gram-negative, and anaerobic bacteria. Preliminary data demonstrated that omadacycline has in vitro activity against Clostridioides difficile; however, large-scale in vitro studies have not been done. The purpose of this study was to assess the in vitro susceptibility of omadacycline and comparators on a large biobank of clinical C. difficile isolates. In vitroC. difficile susceptibility to omadacycline and comparators (fidaxomicin, metronidazole, and vancomycin) was assessed using the broth microdilution method. Minimum bactericidal concentrations (MBCs) and time-kill assays were assessed for pharmacodynamics analysis, and whole-genome sequencing was performed in a subset of isolates to assess distribution of MICs and resistance determinants. Two hundred fifty clinical C. difficile isolates collected between 2015 and 2018 were tested for in vitro susceptibility of omadacycline and comparators. Ribotypes included F001 (n = 5), F002 (n = 56), F014-020 (n = 66), F017 (n = 8), F027 (n = 53), F106 (n = 45), and F255 (n = 17). Omadacycline demonstrated potent in vitro activity with an MIC range of 0.016 to 0.13 μg/ml, an MIC₅₀ of 0.031 μg/ml, and an MIC₉₀ of 0.031 μg/ml. No difference was observed for omadacycline MIC₅₀ and MIC₉₀ values stratified by ribotype, disease severity, or vancomycin susceptibility. Bactericidal activity was confirmed in time-kill studies. No difference was observed in MIC based on C. difficile phylogeny. Further development of omadacycline as an intravenous and oral antibiotic directed toward C. difficile infection is warranted.