Diagnosis ofClostridium difficile-associated disease: examination of multiple algorithms using toxin EIA, glutamate dehydrogenase EIA and loop-mediated isothermal amplification

A Rare Case of Polymerase Chain Reaction-Negative Severe Clostridioides difficile Infection

Accurately diagnosing Clostridioides difficile infection (CDI) is crucial for effective patient management. A misdiagnosis poses risks to patients, leads to treatment delays, and contributes to infection transmission in healthcare settings. While using polymerase chain reaction (PCR) to amplify the toxin B gene is a sensitive method for detecting toxigenic C. difficile, there is still a risk of false-negative results. These inaccuracies could have significant consequences for diagnosing and treating CDI, emphasizing the need for careful consideration and other diagnostic approaches. This case report highlights a patient with severe CDI who had negative PCR and toxin and a biopsy showing pseudomembranous colitis on further testing due to persistence and worsening of symptoms. In the diagnosis of C. difficile infection, healthcare providers should consider clinical symptoms, although diarrhea, which is a major sign of CDI, can be due to other causes. Even in the presence of negative PCR results, if a patient displays symptoms consistent with C. difficile-associated disease, healthcare providers may still contemplate treatment.

Clostridioides difficile infection surveillance in intensive care units and oncology wards using machine learning

OBJECTIVE

Screening individuals admitted to the hospital for Clostridioides difficile presents opportunities to limit transmission and hospital-onset C. difficile infection (HO-CDI). However, detection from rectal swabs is resource intensive. In contrast, machine learning (ML) models may accurately assess patient risk without significant resource usage. In this study, we compared the effectiveness of swab surveillance to daily risk estimates produced by an ML model to identify patients who will likely develop HO-CDI in the intensive care unit (ICU) setting.

DESIGN

A prospective cohort study was conducted with patient carriage of toxigenic C. difficile identified by rectal swabs analyzed by anaerobic culture and polymerase chain reaction (PCR). A previously validated ML model using electronic health record data generated daily risk of HO-CDI for every patient. Swab results and risk predictions were compared to the eventual HO-CDI status.

PATIENTS

Adult inpatient admissions taking place in University of Michigan Hospitals' medical and surgical intensive care units and oncology wards between June 6th and October 8th, 2020.

RESULTS

In total, 2,979 admissions, representing 2,044 patients, were observed over the course of the study period, with 39 admissions developing HO-CDIs. Swab surveillance identified 9 true-positive and 87 false-positive HO-CDIs. The ML model identified 9 true-positive and 226 false-positive HO-CDIs; 8 of the true-positives identified by the model differed from those identified by the swab surveillance.

CONCLUSION

With limited resources, an ML model identified the same number of HO-CDI admissions as swab-based surveillance, though it generated more false-positives. The patients identified by the ML model were not yet colonized with C. difficile. Additionally, the ML model identifies at-risk admissions before disease onset, providing opportunities for prevention.

Molecular characterization of Clostridium difficile isolated from carriage and association of its pathogenicity to prevalent toxic genes

BACKGROUND

There are reports of non-toxigenic C. difficile strains from asymptomatic carriers are increasing source of transmission. Asymptomatic carriage transmission in the hospital or community settings might have changed over the years. Therefore, we initiated a prospective epidemiological study to define the risk factors and pathogenicity of asymptomatic C. difficile carriage.

METHODS

Stools sample from 188 subjects with diarrhoea due to C. difficile toxin and colonization without diarrhoea was subjected to routine microbial culture, molecular characterization for identification of toxin genes and mechanisms of resistance in C.difficile. Demographic data were recorded. Fifty five were positive for C. difficile includes thirty nine toxigenic C. difficile (TCD) and sixteen non toxigenic C. difficile (NTCD) isolates. Pathogenecity of toxic and nontoxic strains were analysed using AO/EB staining, Annexin V staining using flow cytometer and Galleria mellonella survival analyses.

RESULTS

Among 188, fifty five were positive for C.difficile. Infected or colonized individual with TCD or NTCD were more frequently exposed to hemodialysis compared with uncolonized patients. Isolates showed more resistant to clindamycin and levofloxacin. All TCD and eight of NTCD were tcdA-positive. Only four of TCD were positive for cdtA, tcdA, and tcdB (7%, n = 55). In thirty isolates erm (B) gene was found to be prevelant gene. High virulence was found with TCD strain and it was validated using in Galleria mellonella infection model which supported in vitro experiments. The strain with cdtA, tcdA, and tcdB, seen to have elevated virulence to increased resistance and virulence subsequently led to raised virulence in this pathogen.

CONCLUSION

Asymptomatic TCD colonization was relatively high, however, with a small number of enrolled subjects the significant of results might have limitations and the occurrence of CDI among different age group still remains unclear.

Disparate prevalence of toxigenic and nontoxigenic Clostridium difficile among distinct adult patient populations in a single institution

Clostridium difficile (CD) disease remains a costly and important hospital-associated infection. Although nontoxigenic CD is detected by some CD testing methods, can interfere with some detection algorithms and has been suggested as a treatment for CD disease, little is known about the relative occurrence of toxigenic and nontoxigenic CD in a single institution.We used both chromogenic and selective agar media to recover CD isolates and a molecular method to detect the toxin B gene from over 2400 fresh unformed stool specimens with isolates further tested for the toxin B gene. We recovered 74 nontoxigenic and 306 toxigenic CD isolates for which a collection site could be assigned.The frequency of recovery of toxigenic and nontoxigenic CD for each hospital location and the ratio of toxigenic to nontoxigenic CD were calculated. Although the overall prevalence of toxigenic and nontoxigenic CD was 12.7 % and 3.1 %, respectively, on some wards, 48 % of all CD were nontoxigenic, while on other wards, ≤5 % were nontoxigenic.The disparate ratios of nontoxigenic CD to toxigenic CD presented here for the various 'groups' within the adult veteran population are important to the ongoing discussion and reexamination of other published work on the occurrence of toxigenic and nontoxigenic CD, for evaluating the performance of CD detection tests, for designing infection control strategies and in ultimately understanding both CD carriage and disease.

Controversies Around Epidemiology, Diagnosis and Treatment of Clostridium difficile Infection

Clostridium difficile infection is a major public health problem. However, in recent years the epidemiology, risk factors, diagnosis, and treatment of C. difficile infection have undergone a significant change. The incidence of C. difficile has increased, not only in the healthcare sector but also in the community. Hospital-acquired infection and community-acquired disease have different risk factors, with the latter occurring in children and younger individuals without a history of antibiotic use or previous infections. From a clinician's perspective, a quick efficient diagnosis is required for patient treatment; however, the old method of using enzyme immunoassays is insensitive and not very specific. Recent literature around diagnostic testing for C. difficile infection suggests using PCR or a two-step algorithm to improve sensitivity and specificity. More failures and recurrence with metronidazole have led to treatment algorithms suggesting its use for mild infections and switching to vancomycin if there is no clinical improvement. Alternatively, if signs and symptoms suggest severe infection, then oral vancomycin is recommended as a first-line agent. The addition of a new but costly agent, fidaxomicin, has seen some disparity between the European and North American guidelines with regard to when it should be used. Lastly, rapid developments and good results with fecal microbial transplantation have also left clinicians wondering about its place in therapy. This article reviews the literature around some of the recent controversies in the field of C. difficile infection.

Real-time cellular analysis for quantitative detection of functional Clostridium difficile toxin in stool

Rapid and accurate diagnosis and monitoring of Clostridium difficile infection (CDI) is critical for patient care and infection control. We will briefly review current laboratory techniques for the diagnosis of CDI and identify aspects needing improvement. We will also introduce a real-time cellular analysis (RTCA) assay developed for the diagnosis and monitoring of CDI using electronic impedance to assess the cell status. The RTCA assay uses impedance measurement to detect minute physiological changes in cells cultured on gold microelectrodes embedded in glass substrates in the bottom of microtiter wells. This assay has been adapted for quantitative detection of C. difficile functional toxin directly from stool specimens. Compared to conventional techniques and molecular assays, the RTCA assay provides a valuable tool for the diagnosis of CDI as well as for the assessment of clinical severity and for monitoring therapeutic efficacies.

Variations in virulence and molecular biology among emerging strains of Clostridium difficile

Clostridium difficile is a Gram-positive, spore-forming organism which infects and colonizes the large intestine, produces potent toxins, triggers inflammation, and causes significant systemic complications. Treating C. difficile infection (CDI) has always been difficult, because the disease is both caused and resolved by antibiotic treatment. For three and a half decades, C. difficile has presented a treatment challenge to clinicians, and the situation took a turn for the worse about 10 years ago. An increase in epidemic outbreaks related to CDI was first noticed around 2003, and these outbreaks correlated with a sudden increase in the mortality rate of this illness. Further studies discovered that these changes in CDI epidemiology were associated with the rapid emergence of hypervirulent strains of C. difficile, now collectively referred to as NAP1/BI/027 strains. The discovery of new epidemic strains of C. difficile has provided a unique opportunity for retrospective and prospective studies that have sought to understand how these strains have essentially replaced more historical strains as a major cause of CDI. Moreover, detailed studies on the pathogenesis of NAP1/BI/027 strains are leading to new hypotheses on how this emerging strain causes severe disease and is more commonly associated with epidemics. In this review, we provide an overview of CDI, discuss critical mechanisms of C. difficile virulence, and explain how differences in virulence-associated factors between historical and newly emerging strains might explain the hypervirulence exhibited by this pathogen during the past decade.

Molecular test based on isothermal helicase-dependent amplification for detection of the Clostridium difficile toxin A gene

The AmpliVue Clostridium difficile assay and a glutamate dehydrogenase (GDH)-illumigene algorithm were evaluated using 308 diarrheal stool specimens of patients suspected of having C. difficile infection. Compared to the enriched toxigenic culture method, the sensitivities, specificities, and positive and negative predictive values of the AmpliVue C. difficile assay and the GDH-illumigene-based algorithm were 91.7% (95% confidence interval [CI], 76.4 to 97.8), 100% (95% CI, 98.3 to 100), 100% (95% CI, 87 to 100), and 98.9% (95% CI, 96.6 to 99.7), respectively.

Real-time cellular analysis coupled with a specimen enrichment accurately detects and quantifies Clostridium difficile toxins in stool

We describe here the use of an immunomagnetic separation enrichment process coupled with a modified real-time cellular analysis (RTCA) system (RTCA version 2) for the detection of C. difficile toxin (CDT) in stool. The limit of CDT detection by RTCA version 2 was 0.12 ng/ml. Among the consecutively collected 401 diarrheal stool specimens, 53 (13.2%) were toxin-producing C. difficile strains by quantitative toxigenic culture (qTC); bacterial loads ranged from 3.00 × 10(1) to 3.69 × 10(6) CFU/ml. The RTCA version 2 method detected CDT in 51 samples, resulting in a sensitivity of 96.2%, a specificity of 99.7%, and positive and negative predictive values of 98.1% and 99.4%, respectively. The positive step time ranged from 1.43 to 35.85 h, with <24 h for 80% of the samples. The CDT concentrations in stool samples determined by RTCA version 2 correlated with toxigenic C. difficile bacterial load (R(2) = 0.554, P = 0.00002) by qTC as well as the threshold cycle (R(2) = 0.343, P = 0.014) by real-time PCR. A statistically significant correlation between the CDT concentrations and the clinical severity of CDI was observed (P = 0.015). The sensitivity of the RTCA version 2 assay for the detection of functional toxins in stool specimens was significantly improved when the immunomagnetic separation enrichment process was incorporated. More than 80% positive results can be obtained within 24 h. The stool specimen CDT concentration derived using the RTCA version 2 assay correlates with clinical severity and may be used as a marker for monitoring the status of CDI.